We want to thank all the subjects involved in this study. We also appreciate the imaging assistance by Light Innovation Technology Ltd, Shenzhen. This study was supported by Natural Science Funding of China (Grant No. 82201851), Shenzhen Science and Technology Program (Grant No. JCYJ20210324141403009, RCYX20210609104608036), Shenzhen Key Medical Discipline Construction Fund (Grant No. SZXK028), and Shenzhen Baoan Women&#39;s and Children&#39;s Hospital (Grant No. BAFY 2023003).

NOTE: All reagents used in this protocol can be found in the Table of Materials. Unless otherwise specified, all media were pre-equilibrated to 37 &#176;C before use.
1. 3D&#160;printing of the scaffold and model construction
NOTE: The steps here were performed according to the manual book of the commercial 3D-metal printing machine. The steps are briefly described below (Supplementary File 1).
<ol>
	<li>Print bed leveling
	<ol>
		<li>Tap the Menu icon on the dashboard and navigate to Utilities. Select Bed Level to initiate the leveling routine.</li>
		<li>Remove the print sheet from the print bed and select Done. The print bed will ascend to its maximum height in preparation for leveling. Once the progress bar reaches 100%, press Start.</li>
		<li>If the Metal X printer has not been leveled previously, select Reset. If it has, choose Skip and proceed directly to Step 1.1.5 (the 16-point scan).</li>
		<li>Use a 2.5 mm hex key to turn all three-bed leveling screws clockwise until they are tight. Then, loosen them by turning counterclockwise two full rotations to set them at a mid-point height. Press Done to continue.</li>
		<li>The printer will scan the bed at 16 designated points. Refrain from touching the bed or frame during this process. Once the progress reaches 100%, press Next.</li>
	</ol>
	</li>
	<li>Print sheet application
	<ol>
		<li>Remove any residual metal or support debris. Toggle the Vacuum slider to On.</li>
		<li>Allow the bed to lower and heat up, then press Next. Place the print sheet over the vacuum grid and press Next.</li>
		<li>Position the sheet press over the print sheet, aligning it with the Z-rails at the rear of the chamber.</li>
		<li>Wait for the vacuum to engage and create a stable seal. Once the vacuum is engaged, press Done.</li>
	</ol>
	</li>
	<li>Metal filament loading
	<ol>
		<li>Manually position the print head in the center of the printing area. Remove the print head cover by sliding it upward and off the mounting screws.</li>
		<li>Tap the Menu icon on the option board. Select Materials from the options.</li>
		<li>Choose Load Metal to start the loading routine. Choose Quick Load.</li>
		<li>Select the specific type of metal material to be loaded (e.g., Aluminum 6061-T6 | 3.3211 | 65028 | AlMg1SiCu).</li>
		<li>Put the spool on the holder and press Next. Close the door and allow the spools to warm up, then press Next.</li>
		<li>Insert the material into the front inlet of the print head (labeled M) until the extruder begins to draw it through.</li>
	</ol>
	</li>
	<li>Metal part printing
	<ol>
		<li>In the Printing Settings panel, click Export Build. Save the file to a USB drive formatted to FAT32 and insert it into the printer.</li>
		<li>Select the Menu icon on the board. Navigate to Storage and select Print From Storage. Choose the part file to commence printing.</li>
	</ol>
	</li>
	<li>Metal part removing
	<ol>
		<li>Carefully slide the print sheet and printed parts off the print bed. Gently detach the parts from the print sheet. The flexible sheet should peel away with ease.</li>
	</ol>
	</li>
</ol>
2. Preparation for cell co-culture in the 3D model
NOTE: It is recommended that high-temperature resistant materials be used as consumables for 3D printing cell coverslip scaffold supports to facilitate autoclave sterilization before each use in cell culture experiments. Immortalized Human Endometrial Stromal Cells (HESC) and human endometrial epithelial cells (Ishikawa) were used in this study. The characterization of these cell lines has been previously reported5,6.
<ol>
	<li>Cell culture and passaging
	<ol>
		<li>Prepare 50 mL of complemental medium for hESC by adding DMEM/F12 medium + 2 mM L-Glutamine + 10% charcoal-stripped Fetal Bovine Serum (FBS) + 1% Penicillin/Streptomycin Solution.</li>
		<li>Prepare 50 mL of complemental medium for Ishikawa by adding Dulbecco&#39;s Modified Eagle Medium + 10% FBS + 1% Penicillin/Streptomycin Solution.</li>
		<li>Cell thawing 
		NOTE: The purchased cell line was shipped on dry ice in a frozen state. It should be stored in the vapor phase of liquid nitrogen or below -130 &#176;C.
		<ol>
			<li>Prepare all necessary sterilized equipment and dissociation enzyme, and warm the complemental medium to 37 &#176;C.</li>
			<li>Thaw the cells rapidly in a 37 &#176;C water bath with occasional gentle swaying. Transfer the cell suspension into a tube containing 5 mL of basal culture medium and centrifuge at 200 x g for 5 min.</li>
			<li>Carefully remove the supernatant. Resuspend the cell pellet in 5 mL of prepared complete culture medium and dispense it into two T25 culture flasks. Culture the cells in an incubator at 37 &#176;C and 5% CO2.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Preparation of cells with a coverslip
	<ol>
		<li>Use an 18 mm square coverslip as the surface of the cell culture; make sure the coverslip is clean and sterile.</li>
		<li>Coat the coverslip in the bottom of a 12-well plate with 200 &#181;L of extracellular matrix (ECM) at a concentration of 200-300 &#181;g/mL. Keep the plate at 37 &#176;C for 1 h.</li>
		<li>Remove the ECM from the plate. Inspect the cells for appropriate confluency, and make sure the density of both cell lines is around 70%-80%</li>
		<li>Remove the spent medium and wash the cells with 3 mL of phosphate-buffered saline (PBS) 2x.</li>
		<li>Add 2 mL of dissociation enzyme and culture the cells at 37 &#176;C for 2 min to detach them.</li>
		<li>Neutralize with complete culture medium and create a single-cell suspension by pipetting up and down.</li>
		<li>Take 100 &#181;L of the cell suspension and mix with trypan blue (dilution factor =2).</li>
		<li>Slide the coverslip over the chamber of the hemocytometer. Fill both side chambers with the cell suspension containing trypan blue.</li>
		<li>Count the number of cells in squares on both sides under a 20x microscope and calculate the density of cells.</li>
		<li>Transfer the cells to the prepared plate with fresh medium and incubate at 37 &#176;C with 5% CO2. Seed hESC into the well at 1 x 105 cells/mL for 24 h.</li>
		<li>For the Ishikawa cell line, seed the cell into the well without a coverslip the next day.</li>
	</ol>
	</li>
</ol>
3. Assembly of the co-culture model
<ol>
	<li>Soak the scaffolds with ethyl alcohol and double distilled water (ddw) thoroughly for 2 days. Sterilize scaffolds with an autoclave at 121 &#176;C and dry them.</li>
	<li>Add about 2 mL of complemental medium for the Ishikawa cell line to the well culturing Ishikawa, ensuring the liquid level covers the coverslip.</li>
	<li>Transfer the coverslip cover with hESC onto the scaffold and keep the side with the cell down. Plug the scaffold into the well-culturing Ishikawa. For the second set, invert this arrangement by transferring the coverslip cover with Ishikawa onto the scaffold and plugging the scaffold into the well-culturing hESC. Use the cells without the scaffold setup for independently growing cell growth analysis.</li>
	<li>Incubate the co-culture system at 37 &#176;C, 5% CO2. The co-culture period can vary depending on the experimental design but typically ranges from 24-72 h.</li>
</ol>
4. Image acquisition
<ol>
	<li>Carefully remove the culture medium and rinse cells gently with sterile phosphate-buffered saline (PBS).</li>
	<li>Remove coverslips with attached cells from culture dishes using fine forceps or tweezers. Optionally, place coverslips in a new dish with PBS to prevent drying during transfer.</li>
	<li>Take a clean microscope slide and place a drop of PBS. Gently transfer the coverslip containing cells onto the drop of mounting medium, ensuring cells face down onto the slide.</li>
	<li>Place the prepared slide onto the stage of the inverted microscope. Select the appropriate objective lens (e.g., 10x, 20x) and adjust focus using coarse and fine focus knobs.</li>
	<li>Set microscope parameters such as illumination intensity and camera settings. Using the microscope software, capture images of the cells at desired magnifications and fields of view. Adjust exposure time and other imaging settings to optimize image quality.</li>
</ol>
5. Image processing
<ol>
	<li>Click Open to open the image, click Process &#62; Filters &#62; Enhancement in order &#62; Choose Local Equalization, and click Apply.</li>
	<li>Click Edit &#62; Convert To &#62; Gray Scale 8. Click Enhance, choose Apply Contrast.</li>
	<li>Click Count and measure subjects. Click Manual, select a range, and adjust the histogram to make sure that all the cells are covered.</li>
	<li>Click Apply Mask, close the current window, Click Automatic Bright Objects &#62; Measure, Select Measurement, and choose Aera, Dendric, Density, and Size.</li>
	<li>Click Automatic Bright Objects, then click Count. Click Export Data to export the measurement data to a spreadsheet.</li>
</ol>
6. Cell harvesting
<ol>
	<li>Remove coverslips from the microscope slide and transfer them to a clean and dry well.</li>
	<li>Harvest the Ishikawa cell with RNA isolation reagent for transcriptomic or Ripa lysis reagent for proteomic research. 
	NOTE: For hESC, the coverslip-culture method was more effective for image capture after immune staining. Alternatively, the hESC could be harvested with RNA isolation reagent or Ripa lysis reagent. Cell lines cultured on the coverslip or the surface of the plate could be exchanged; however, we recommend that the cells prepared for imaging analysis be seeded on the coverslip.</li>
</ol>

3D-Printed Scaffold Model to Investigate Embryo Implantation Mechanisms

<ol><li>Iske, J., Elkhal, A., Tullius, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+fetal-maternal+immune+interface+in+uterus+transplantation%5BTitle%5D)+AND+%22Trend+Immunol%22%5BJournal%5D)">The fetal-maternal immune interface in uterus transplantation.</a> Trend Immunol. 41 (3), 213-224 (2020).</li>
<li>Dey, S. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Molecular+cues+to+implantation%5BTitle%5D)+AND+%22Endocrine+Rev%22%5BJournal%5D)">Molecular cues to implantation.</a> Endocrine Rev. 25 (3), 341-373 (2004).</li>
<li>Li, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Three-dimensional+culture+models+of+human+endometrium+for+studying+trophoblast-endometrium+interaction+during+implantation%5BTitle%5D)+AND+%22Reprod+Biol+Endocrinol%22%5BJournal%5D)">Three-dimensional culture models of human endometrium for studying trophoblast-endometrium interaction during implantation.</a> Reprod Biol Endocrinol. 20 (1), 120(2022).</li>
<li>Goss, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mod3d%3A+A+low-cost%2C+flexible+modular+system+of+live-cell+microscopy+chambers+and+holders%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">Mod3d: A low-cost, flexible modular system of live-cell microscopy chambers and holders.</a> PLoS One. 17 (6), e0269345(2021).</li>
<li>Zheng, J., Liu, L., Wang, S., Huang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Sumo-1+promotes+Ishikawa+cell+proliferation+and+apoptosis+in+endometrial+cancer+by+increasing+sumoylation+of+histone+h4%5BTitle%5D)+AND+%22Int+J+Gynecol+Cancer%22%5BJournal%5D)">Sumo-1 promotes Ishikawa cell proliferation and apoptosis in endometrial cancer by increasing sumoylation of histone h4.</a> Int J Gynecol Cancer. 25 (8), 1364-1368 (2015).</li>
<li>Damdimopoulou, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Human+embryonic+stem+cells%5BTitle%5D)+AND+%22Best+Pract+Res+Clin+Obst+Gynaecol%22%5BJournal%5D)">Human embryonic stem cells.</a> Best Pract Res Clin Obst Gynaecol. 31, 2-12 (2016).</li>
<li>Gargett, C. E., Schwab, K. E., Deane, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Endometrial+stem%2Fprogenitor+cells%3A+The+first+10+years%5BTitle%5D)+AND+%22Hum+Reprod+Update%22%5BJournal%5D)">Endometrial stem/progenitor cells: The first 10 years.</a> Hum Reprod Update. 22 (2), 137-163 (2015).</li>
<li>Lerman, M. J., Lembong, J., Gillen, G., Fisher, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((3d+printing+in+cell+culture+systems+and+medical+applications%5BTitle%5D)+AND+%22Appl+Phys+Rev%22%5BJournal%5D)">3d printing in cell culture systems and medical applications.</a> Appl Phys Rev. 5 (4), 041109(2018).</li>
<li>Palmara, G., Frascella, F., Roppolo, I., Chiappone, A., Chiadò, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Functional+3d+printing%3A+Approaches+and+bioapplications%5BTitle%5D)+AND+%22Biosens+Bioelectron%22%5BJournal%5D)">Functional 3d printing: Approaches and bioapplications.</a> Biosens Bioelectron. 175, 112849(2021).</li>
<li>Li, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Multiscale+architecture+design+of+3d+printed+biodegradable+zn-based+porous+scaffolds+for+immunomodulatory+osteogenesis%5BTitle%5D)+AND+%22Nat+Comm%22%5BJournal%5D)">Multiscale architecture design of 3d printed biodegradable zn-based porous scaffolds for immunomodulatory osteogenesis.</a> Nat Comm. 15 (1), 3131(2024).</li>
<li>Arnold, J. T., Lessey, B. A., Seppälä, M., Kaufman, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+normal+endometrial+stroma+on+growth+and+differentiation+in+Ishikawa+endometrial+adenocarcinoma+cells1%5BTitle%5D)+AND+%22Cancer+Res%22%5BJournal%5D)">Effect of normal endometrial stroma on growth and differentiation in Ishikawa endometrial adenocarcinoma cells1.</a> Cancer Res. 62 (1), 79-88 (2002).</li>
<li>Casper, R. F., Yanushpolsky, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Optimal+endometrial+preparation+for+frozen+embryo+transfer+cycles%3A+Window+of+implantation+and+progesterone+support%5BTitle%5D)+AND+%22Fertil+Steril%22%5BJournal%5D)">Optimal endometrial preparation for frozen embryo transfer cycles: Window of implantation and progesterone support.</a> Fertil Steril. 105 (4), 867-872 (2016).</li>
<li>Cooke, P. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Stromal+estrogen+receptors+mediate+mitogenic+effects+of+estradiol+on+uterine+epithelium%5BTitle%5D)+AND+%22Proc+Natl+Acad+Sci+U+S+Am%22%5BJournal%5D)">Stromal estrogen receptors mediate mitogenic effects of estradiol on uterine epithelium.</a> Proc Natl Acad Sci U S Am. 94 (12), 6535-6540 (1997).</li>
<li>Owusu-Akyaw, A., Krishnamoorthy, K., Goldsmith, L. T., Morelli, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+role+of+mesenchymal-epithelial+transition+in+endometrial+function%5BTitle%5D)+AND+%22Hum+Reprod+Update%22%5BJournal%5D)">The role of mesenchymal-epithelial transition in endometrial function.</a> Hum Reprod Update. 25 (1), 114-133 (2019).</li>
<li>Evans, J., Hutchison, J., Salamonsen, L. A., Azlan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Endometrial+inflammasome+activation+accompanies+menstruation+and+may+have+implications+for+systemic+inflammatory+events+of+the+menstrual+cycle%5BTitle%5D)+AND+%22Hum+Reprod%22%5BJournal%5D)">Endometrial inflammasome activation accompanies menstruation and may have implications for systemic inflammatory events of the menstrual cycle.</a> Hum Reprod. 35 (6), 1363-1376 (2020).</li>
<li>Gołąbek-Grenda, A., Olejnik, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vitro+modeling+of+endometriosis+and+endometriotic+microenvironment+-+challenges+and+recent+advances%5BTitle%5D)+AND+%22Cellular+Signal%22%5BJournal%5D)">In vitro modeling of endometriosis and endometriotic microenvironment - challenges and recent advances.</a> Cellular Signal. 97, 110375(2022).</li>
<li>Berger, C., Boggavarapu, N. R., Menezes, J., Lalitkumar, P. G. L., Gemzell-Danielsson, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+ulipristal+acetate+on+human+embryo+attachment+and+endometrial+cell+gene+expression+in+an+in+vitro+co-culture+system%5BTitle%5D)+AND+%22Hum+Reprod%22%5BJournal%5D)">Effects of ulipristal acetate on human embryo attachment and endometrial cell gene expression in an in vitro co-culture system.</a> Hum Reprod. 30 (4), 800-811 (2015).</li>
</ol>

The authors declare that they have no conflicts of interest.

A simplified and cost-effective protocol is described for the indirect co-culture of endometrial stromal and epithelial cells. This method utilizes a homemade scaffold for cell slides, which comprises an upper support ring tailored for attachment to standard 12-well cell culture plates, complemented by a basal cell slide holder featuring four L-shaped rod-like structures. This setup facilitates the separation of endometrial stromal and epithelial cells while allowing for their interaction through the exchange of signaling molecules in the culture medium. One of the key advantages of this approach is the substantial reduction in both time and expenditure compared to commercially available co-culture systems11. The homemade scaffold is constructed from readily available materials, significantly lowering the cost of the setup. Additionally, its design is straightforward, enabling researchers to assemble and disassemble the scaffold with ease, thus saving time and effort in the laboratory. Moreover, the homemade scaffold can be cleaned and sterilized for multiple uses, making it a sustainable and economical option for ongoing research. This feature is particularly beneficial for long-term studies, where consistent and reliable results are crucial.
Endometrial stromal cells and epithelial cells play pivotal roles in facilitating successful embryo implantation. Under physiological conditions, endometrial epithelial cells and stromal cells in the endometrium do not typically have direct contact.Research on human endometrial stromal cell decidualization has proved that epithelial cells influence the decidual process by paracrine. The close proximity of epithelial and stromal cells allows for effective communication through paracrine signaling12. This interaction is vital for coordinating the cyclical changes in the endometrium, including the preparation for implantation and subsequent tissue shedding if implantation does not occur11. Both epithelial and stromal cells express receptors for estrogen and progesterone, which regulate their proliferation, differentiation, and secretory activities. The epithelial-stromal crosstalk ensures that these responses are well-coordinated13. Thus, the complex crosstalk between these cells remains a critical area of investigation, as it is essential to understand the intricate processes that underlie endometrial receptivity and the implantation of the embryo14. Despite significant advances in reproductive biology, the detailed mechanisms of communication between these cell types during implantation are still not fully elucidated15.
The scaffold provides a convenient way to achieve the co-culture of two kinds of adherent cells. However, in the process of long-term co-culture, the coverslip cells continue to grow and renew over time, and the dead cells will fall and come into contact with the lower-layer cells, which may impact the lower-layer cells. In addition, the cells seed on the coverslip are placed face down on the scaffold. Whether gravity has any effect on the state of the cells is unknown. In this research, two cell lines, hESC and Ishikawa, were used for demonstration. The scaffold can be widely used in the co-culture of two different kinds of adherent cell lines. In addition, the scaffold can also be used as a platform for other compounds or medicine release media and as a mounting platform for various devices such as luminescence, heating, and electrode devices.
Here, we present a reliable and robust in vitro cell culture system utilizing the specific scaffold, which is a useful and convenient tool to study the molecular mechanism of embryo-maternal uterine cell interactions further. In addition, we have characterized the feasibility of the established scaffold as a model for blastocyst/trophoblast studies. This protocol allows the construction of suitable scaffolds by 3D printing and their function as the 3D structure for the migration or invasion platforms in small volumes (12-well plates), where different factors can be evaluated using imaging quantification systems.
The use of cell lines allows the standardization of the model to compare different conditions, something that is not applicable using fresh primary villi tissues. However, any of the cell line components can be replaced by primary culture for validation. By incorporating the cells and tissues derived from patients of interest, the proposed model may facilitate the demonstration and modeling of different diseases that have been known to contribute to infertility and pregnancy failure.
Critical steps 
Firstly, the density of Ishikawa cells for co-culture should be limited, approximately 60%-70% confluency. Secondly, the coverslip cover with cells should be kept down. Thirdly, the concentration of ECM should be less than 3 mg/mL to avoid forming a gel. Fourthly, the liquid level of the medium in the co-culture system should cover the coverslip.
Limitations 
The model mentioned above comprises the endometrial epithelial cells and the stromal cells; one limitation of the study was the use of adenocarcinoma Ishikawa cells as epithelial cell surrogates instead of primary cells. Integrating primary epithelial and stromal cells from the same patient would replicate the physiological conditions of the human endometrium. For some experimental applications, a possible limitation concerns the lack of other cell types, such as endothelial cells and immune cells, and there is no characterization of the glandular structure in this model to assess the interactive impact of the endometrial glands on other endometrial cell types. However, under physiological conditions, the epithelial cells reveal polarity, and this character hardly simulates in vitro conditions without a uterine luminal environment. The endometrial stromal cells are under the decidual process in the menstrual cycle16,17. However, the molecular mechanism of decidualization remains unclear. Several factors, including immunocytes and endothelial cells, could play a role in decidualization. This model provides a limited way of examining the indirect crosstalk between stromal and epithelial cells during the decidual process. Furthermore, the levels and roles of the biological markers during decidualization are still unclear, which warrants further exploration

Despite extensive research on human pregnancy, the molecular mechanisms at the maternal-fetal interface during implantation and early pregnancy remain poorly understood1. The human endometrium is mainly composed of two cell types: endometrial epithelial cells (EECs) and endometrial stromal cells (ESCs). Implantation progresses through three stages: apposition, attachment, and invasion, which lead to the development of a competent embryo and receptive endometrium2. Considering the ethical constraints of in vivo studies on human subjects, as well as the difficulties in simulating the human condition in animals completely, the construction of in vitro human endometrium culture models has become an effective means of replicating the implantation and early pregnancy processes3. These models are valuable in investigating both normal and pathological pregnancies and provide a foundational platform for the preliminary testing and validation of therapeutic interventions in translational medicine.
Commercial chambers have been widely utilized in cellular biological research. These chambers offer valuable insights into cell migration and the crosstalk between different types of cells. However, commercial chambers are typically single-use and can be costly4.
A great number of in vitro human culture models consisting of endometrium and blastocyst, or blastocyst surrogates, have been developed to better understand the detailed process of implantation. These models, however, are still in their initial stage of application since the 3D structure is a highly complicated experimental setup, and certain specific differentiation media are expensive5,6,7.
The use of affordable 3D-printing hardware and a relatively short manufacturing period makes it possible to fit structures to target different experimental purposes. 3D printing techniques help reduce time costs and enable the creation of complex, customized structures. This technology significantly accelerates prototype design and iteration, making it a valuable tool for researchers across various fields, allowing them to complete their work more efficiently8,9,10.
Here, we present a feasible and economical experimental protocol for the construction of the 3D structure and its use as the cell culture system, which can simulate the interaction between endometrial stromal and epithelial cells for investigation of the endometrial receptivity during embryo implantation. This provides a customizable and low-cost alternative for commercial disposable material.

<table><tbody><tr><td>10x Hanks&amp;prime; Balanced Salt solution</td><td>Solarbio</td><td>H1046</td><td>1/10</td></tr><tr><td>12-well Clear TC-treated Plates</td><td>Corning</td><td>3513</td><td>-</td></tr><tr><td>25 cm&amp;sup2; Cell Culture Flask</td><td>Corning</td><td>430639</td><td>-</td></tr><tr><td>Aluminum</td><td>Markforged</td><td>6061-T6</td><td>-</td></tr><tr><td>DMEM/F12</td><td>Sigma-aldrich</td><td>D2906</td><td>-</td></tr><tr><td>Dulbecco&amp;rsquo;s Modified Eagle Medium&amp;nbsp;</td><td>Gibco</td><td>C11995500BT</td><td></td></tr><tr><td>FBS</td><td>Gibco</td><td>10099141C</td><td>1/10</td></tr><tr><td>Fetal bovine serum</td><td>Gibco</td><td>10099141C</td><td></td></tr><tr><td>ITS Premix</td><td>Biocoat</td><td>354350</td><td>1/100</td></tr><tr><td>Matrigel Matrix</td><td>Corning</td><td>354248</td><td>ECM</td></tr><tr><td>Metal X</td><td>Markforged</td><td>M F-PR-5000</td><td>-</td></tr><tr><td>Penicillin-Streptomycin</td><td>Gibco</td><td>15140122</td><td>1/100</td></tr><tr><td>Round Coverslip</td><td>Biosharp</td><td>BS-18-RC</td><td>-</td></tr><tr><td>TrypLE Select (10X)</td><td>Gibco</td><td>A1217701</td><td>dissociation enzyme</td></tr></tbody></table>

co-culture model using two types of adherent cell lines

Embryo implantation is affected by the interactions among different cell types in the mother-embryo interface. The direct and indirect communications between various cell types within the decidua are crucial for regulating endometrial receptivity; however, the molecular mechanisms mediating this interaction are still unclear. In this regard, a model to study the implantation process is needed to establish a comprehensive in vitro model that can recapitulate the biology of endometrial epithelium-stroma interaction. This model is composed of regular cell-culture plates and a matching scaffold, which is generated by three-dimensional (3D) printing from low-cost materials. Here, we detail a set of protocols for model construction, cell preparation, cell seeding, cell culture, observation, and evaluation. Furthermore, we have included representative results with cells exhibiting good growth conditions under the microscope. This study aimed to develop in vitro models that would mimic the interaction between endometrial stromal cells and epithelial cells, as well as between trophoblast cells and endometrial cells.

Figure 1&#160;shows the homemade scaffold for cell slides used in this process, which comprises an upper support ring tailored for attachment to standard 12-well cell culture plates, complemented by a basal cell slide holder featuring four L-shaped rod-like structures.
According to Figure 2, the density of both cell types in the co-culture condition (Figure 2A,B) remained low after 72 h of co-culture; however, the density of both cell types cultured independently grew significantly (Figure 2C,D). Moreover, the length of co-cultured hESC was shorter compared with independently cultured hESC (Figure 2E-G).
The profile of Ishikawa cells and hESC cells indicates the existence of interactions between the two types of cells. At the same time, the system enables us to continue to perform follow-up experiments on the separate cell lines, including immunochemistry staining and western blot.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/67314/67314fig01.jpg" /> 
Figure 1: 3D-printed coverslip scaffold utilized in the experimental protocol. (A) Scaffold in mono-form. (B) Scaffold in the binary form. (C) Illustration demonstrating the placement of coverslip on the scaffold. (D) Illustration demonstrating the placement of scaffold in a standard 12-well plate. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67314/67314fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/67314/67314fig02.jpg" /> 
Figure 2: Profile of hESC and Ishikawa cell lines treated for 3 days with different conditions. (A) The Ishikawa seed on the coverslip co-cultured with hESC by scaffold (Bar=200 &#181;m). (B) The hESC seed on the coverslip co-cultured with Ishikawa using a scaffold. (C) The Ishikawa cells were cultured in a complemental medium with 10% FBS. (D) The hESC cells were cultured in a complemental medium with 10% FBS. (E) The cell density of hESCs under co-culture conditions is significantly lower than that under independent-culture conditions. (F) The cell density of ISHIKAWA cells under co-culture conditions is significantly lower than that under independent culture conditions. (G) The length of hESC under co-culture conditions is significantly shorter. N=3; ***, p&#60;0.05, the error bar shows standard error. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67314/67314fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplementary File 1: 3D printing coding file. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67314/3D-print.stl" target="_blank">Please click here to download this File.</a>

Author Spotlight: In Vitro Endometrial Models to Study Epithelial-Stroma and Embryo Interactions

The protocol shows a novel in vitro experimental model that can recapitulate the biology of two kinds of adherent cell lines with a three-dimensional (3D)-printed scaffold. The construction of this model and operating procedures, from cell preparation and cell culture to analysis and evaluation, are described.

Co-culture Model Using Two Types of Adherent Cell Lines

Embryo implantation is affected by the interactions among different cell types in the mother-embryo interface. The direct and indirect communications ...

co-culture-model-using-two-types-of-adherent-cell-lines

Nanyang Technological University

Research

JoVE Journal

Biology

549 Views.  Shenzhen University. Zoals de naam van onze instelling, Maternal-Fetal Medicine Institute, suggereert, richt ons onderzoek zich voornamelijk op vrouwelijke reproductieve biologie. We streven ernaar het mechanisme van voortplantingsstoornissen te begrijpen en potentiële doelwitten voor de behandeling ervan te identificeren. Een belangrijk voordeel van deze aanpak is de aanzienlijke vermindering van tijd en kosten in vergelijking met commercieel beschikbare co-cultuursystemen....

Video: Auteur in de schijnwerpers: In vitro endometriummodellen om epitheel-stroma en embryo-interacties te bestuderen

Rotating Cell Culture Systems for Human Cell Culture: Human Trophoblast Cells as a Model

The field of human trophoblast research aids in understanding the complex environment established during placentation. Due to the nature of these studies, human in vivo experimentation is impossible. A combination of primary cultures, explant cultures and trophoblast cell lines1 support our understanding of invasion of the uterine wall2 and remodeling of uterine spiral arteries3,4 by extravillous trophoblast cells (EVTs), which is required for successful establishment of pregnancy. Despite the wealth of knowledge gleaned from such models, it is accepted that in vitro cell culture models using EVT-like cell lines display altered cellular properties when compared to their in vivo counterparts5,6. Cells cultured in the rotating cell culture system (RCCS) display morphological, phenotypic, and functional properties of EVT-like cell lines that more closely mimic differentiating in utero EVTs, with increased expression of genes mediating invasion (e.g. matrix metalloproteinases (MMPs)) and trophoblast differentiation7,8,9. The Saint Georges Hospital Placental cell Line-4 (SGHPL-4) (kindly donated by Dr. Guy Whitley and Dr. Judith Cartwright) is an EVT-like cell line that was used for testing in the RCCS.
The design of the RCCS culture vessel is based on the principle that organs and tissues function in a three-dimensional (3-D) environment. Due to the dynamic culture conditions in the vessel, including conditions of physiologically relevant shear, cells grown in three dimensions form aggregates based on natural cellular affinities and differentiate into organotypic tissue-like assemblies10,11,12 . The maintenance of a fluid orbit provides a low-shear, low-turbulence environment similar to conditions found in vivo. Sedimentation of the cultured cells is countered by adjusting the rotation speed of the RCCS to ensure a constant free-fall of cells. Gas exchange occurs through a permeable hydrophobic membrane located on the back of the bioreactor. Like their parental tissue in vivo, RCCS-grown cells are able to respond to chemical and molecular gradients in three dimensions (i.e. at their apical, basal, and lateral surfaces) because they are cultured on the surface of porous microcarrier beads. When grown as two-dimensional monolayers on impermeable surfaces like plastic, cells are deprived of this important communication at their basal surface. Consequently, the spatial constraints imposed by the environment profoundly affect how cells sense and decode signals from the surrounding microenvironment, thus implying an important role for the 3-D milieu13.
We have used the RCCS to engineer biologically meaningful 3-D models of various human epithelial tissues7,14,15,16. Indeed, many previous reports have demonstrated that cells cultured in the RCCS can assume physiologically relevant phenotypes that have not been possible with other models10,17-21. In summary, culture in the RCCS represents an easy, reproducible, high-throughput platform that provides large numbers of differentiated cells that are amenable to a variety of experimental manipulations. 
In the following protocol, using EVTs as an example, we clearly describe the steps required to three-dimensionally culture adherent cells in the RCCS.

Traditional, two dimensional cell culture techniques often result in altered characteristics with respect to differentiation markers, cytokines and growth factors. Three-dimensional cell culture in the rotating cell culture system (RCCS) reestablishes expression of many of these factors as shown here with an extravillous trophoblast cell line.

The field of human trophoblast research aids in  understanding the complex environment established during placentation. Due to the  nature of these ...

Bioengineering

Monitoring Cancer Cell Invasion and T-Cell Cytotoxicity in 3D Culture

Significant progress has been made in treating cancer with immunotherapy, although a large number of cancers remain resistant to treatment. A limited number of assays allow for direct monitoring and mechanistic insights into the interactions between tumor and immune cells, amongst which, T-cells play a significant role in executing the cytotoxic response of the adaptive immune system to cancer cells. Most assays are based on two-dimensional (2D) co-culture of cells due to the relative ease of use but with limited representation of the invasive growth phenotype, one of the hallmarks of cancer cells. Current three-dimensional (3D) co-culture systems either require special equipment or separate monitoring for invasion of co-cultured cancer cells and interacting T-cells.
Here we describe an approach to simultaneously monitor the invasive behavior in 3D of cancer cell spheroids and T-cell cytotoxicity in co-culture. Spheroid formation is driven by enhanced cell-cell interactions in scaffold-free agarose microwell casts with U-shaped bottoms. Both T-cell co-culture and cancer cell invasion into type I collagen matrix are performed within the microwells of the agarose casts without the need to transfer the cells, thus maintaining an intact 3D co-culture system throughout the assay. The collagen matrix can be separated from the agarose cast, allowing for immunofluorescence (IF) staining and for confocal imaging of cells. Also, cells can be isolated for further growth or subjected to analyses such as for gene expression or fluorescence activated cell sorting (FACS). Finally, the 3D co-culture can be analyzed by immunohistochemistry (IHC) after embedding and sectioning. Possible modifications of the assay include altered compositions of the extracellular matrix (ECM) as well as the inclusion of different stromal or immune cells with the cancer cells.

The presented approach simultaneously evaluates cancer cell invasion in 3D spheroid assays and T-cell cytotoxicity. Spheroids are generated in a scaffold-free agarose multi-microwell cast. Co-culture and embedding in type I collagen matrix are performed within the same device which allows to monitor cancer cell invasion and T-cell mediated cytotoxicity.

Significant progress has been made in treating cancer with immunotherapy, although a large number of cancers remain resistant to treatment. A limited ...

Cancer Research

Three-dimensional Co-culture Model for Tumor-stromal Interaction

Cancer progression (initiation, growth, invasion and metastasis) occurs through interactions between malignant cells and the surrounding tumor stromal cells. The tumor microenvironment is comprised of a variety of cell types, such as fibroblasts, immune cells, vascular endothelial cells, pericytes and bone-marrow-derived cells, embedded in the extracellular matrix (ECM). Cancer-associated fibroblasts (CAFs) have a pro-tumorigenic role through the secretion of soluble factors, angiogenesis and ECM remodeling. The experimental models for cancer cell survival, proliferation, migration, and invasion have mostly relied on two-dimensional monocellular and monolayer tissue cultures or Boyden chamber assays. However, these experiments do not precisely reflect the physiological or pathological conditions in a diseased organ. To gain a better understanding of tumor stromal or tumor matrix interactions, multicellular and three-dimensional cultures provide more powerful tools for investigating intercellular communication and ECM-dependent modulation of cancer cell behavior. As a platform for this type of study, we present an experimental model in which cancer cells are cultured on collagen gels embedded with primary cultures of CAFs.

Here we present a protocol to co-culture in three-dimensions, which is useful for investigating multicellular interactions and extracellular matrix-dependent modulation of cancer cell behavior. In this experimental model, cancer cells are cultured on collagen gels embedded with human cancer-associated fibroblasts.

Cancer progression (initiation, growth, invasion and metastasis) occurs through interactions between malignant cells and the surrounding tumor stromal ...

Medicine

Modeling Chemotherapy Resistant Leukemia In Vitro

It is well established that the bone marrow microenvironment provides a unique site of sanctuary for hematopoietic diseases that both initiate and progress in this site. The model presented in the current report utilizes human primary bone marrow stromal cells and osteoblasts as two representative cell types from the marrow niche that influence tumor cell phenotype. The in vitro co-culture conditions described for human leukemic cells with these primary niche components support the generation of a chemoresistant subpopulation of tumor cells that can be efficiently recovered from culture for analysis by diverse techniques. A strict feeding schedule to prevent nutrient fluxes followed by gel type 10 cross-linked dextran (G10) particles recovery of the population of tumor cells that have migrated beneath the adherent bone marrow stromal cells (BMSC) or osteoblasts (OB) generating a "phase dim" (PD) population of tumor cells, provides a consistent source of purified therapy resistant leukemic cells. This clinically relevant population of tumor cells can be evaluated by standard methods to investigate apoptotic, metabolic, and cell cycle regulatory pathways as well as providing a more rigorous target in which to test novel therapeutic strategies prior to pre-clinical investigations targeted at minimal residual disease.

Modeling Chemotherapy Resistant Leukemia In Vitro

The current report summarizes a protocol that can be utilized to model the influence of the bone marrow microenvironment niche on leukemic cells with emphasis placed on enrichment of the most chemoresistant subpopulation.

It is well established that the bone marrow microenvironment provides a unique site of sanctuary for hematopoietic diseases that both initiate and ...

A Co-culture Method to Investigate the Crosstalk Between X-ray Irradiated Caco-2 Cells and PBMC

The protocol adopted in this work aims at unraveling how X-rays perturb the functioning of the intestinal barrier, focusing on the interplay between colorectal tumor cells and the immune system. Colorectal carcinoma is among the most common type of cancer, typically treated by surgery, chemotherapy, and radiotherapy. Advantages of radiotherapy in targeting the tumor are well known. However, even limited exposures of healthy tissues are of great concern, particularly regarding the effects on the intestinal barrier and the immune system. The adopted setup allows to study the interplay between two cell populations in a condition more similar to the physiological one, when compared to normal cell cultures. For this purpose, we resort to different techniques and we used an in vitro co-culture model, based on Caco-2 cells differentiated as a monolayer and PBMC, sharing the same culture medium. This protocol has been developed to focus on both macroscopic effects, i.e. cell viability and Trans-Epithelial Electrical Resistance (TEER), and, through western blot, molecular alterations, i.e. the activation of inflammatory pathway in immune cells and the tight junction protein expression in Caco-2 cells. Initial evaluation of radiation effects on Caco-2 cell viability was assessed via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Trypan blue assays, while TEER was measured at fixed time intervals through an ohmmeter specifically designed for co-culture systems. In this way, the effects due to radiation, the presence of Peripheral Blood Mononuclear Cells (PBMC), and eventually their synergistic effect, can be demonstrated. Through these complementary techniques, we observed a high radio-resistance of Caco-2 within the range of 2 - 10 Gy of X-rays and an increased Caco-2 monolayer permeability when PBMCs were added. In particular, PBMC presence was found to be associated with the variation in the tight junction scaffold proteins expression.

We present a protocol to investigate the crosstalk between X-ray-irradiated Caco-2 and peripheral blood mononuclear cells (PBMC). The protocol starts with Caco-2 irradiation and set-up of the co-culture with PBMC; subsequently, trans-epithelial electrical resistance is measured regularly over 48 h and western blot performed in both Caco-2 and PBMC.

The protocol adopted in this work aims at unraveling how X-rays perturb the functioning of the intestinal barrier, focusing on the interplay between ...

Immunology and Infection

Establishing Single-Cell Based Co-Cultures in a Deterministic Manner with a Microfluidic Chip

Cell co-culture assays have been widely used for studying cell-cell interactions between different cell types to better understand the biology of diseases including cancer. However, it is challenging to clarify the complex mechanism of intercellular interactions in highly heterogeneous cell populations using conventional co-culture systems because the heterogeneity of the cell subpopulation is obscured by the average values; the conventional co-culture systems can only be used to describe the population signal, but are incapable of tracking individual cells behavior. Furthermore, conventional single-cell experimental methods have low efficiency in cell manipulation because of the Poisson distribution. Microfabricated devices are an emerging technology for single-cell studies because they can accurately manipulate single cells at high-throughput and can reduce sample and reagent consumption. Here, we describe the concept and application of a microfluidic chip for multiple single-cell co-cultures. The chip can efficiently capture multiple types of single cells in a culture chamber (~46%) and has a sufficient culture space useful to study the cells&#39; behavior (e.g., migration, proliferation, etc.) under cell-cell interaction at the single-cell level. Lymphatic endothelial cells and oral squamous cell carcinoma were used to perform a single-cell co-culture experiment on the microfluidic platform for live multiple single-cell interaction studies.

This report describes a microfluidic chip-based method to set up a single cell culture experiment in which high-efficiency pairing and microscopic analysis of multiple single cells can be achieved.

Cell co-culture assays have been widely used for studying cell-cell interactions between different cell types to better understand the biology of diseases ...

Microfluidic Co-Culture Models for Dissecting the Immune Response in in vitro Tumor Microenvironments

Complex disease models demand cutting-edge tools able to deliver physiologically and pathologically relevant, actionable insights, and unveil otherwise invisible processes. Advanced cell assays closely mimicking in vivo scenery are establishing themselves as novel ways to visualize and measure the bidirectional tumor-host interplay influencing the progression of cancer. Here we describe two versatile protocols to recreate highly controllable 2D and 3D co-cultures in microdevices, mimicking the complexity of the tumor microenvironment (TME), under natural and therapy-induced immunosurveillance. In section 1, an experimental setting is provided to monitor crosstalk between adherent tumor cells and floating immune populations, by bright field time-lapse microscopy. As an applicative scenario, we analyze the effects of anti-cancer treatments, such as the so-called immunogenic cancer cell death inducers on the recruitment and activation of immune cells. In section 2, 3D tumor-immune microenvironments are assembled in a competitive layout. Differential immune infiltration is monitored by fluorescence snapshots up to 72 h, to evaluate combination therapeutic strategies. In both settings, image processing steps are illustrated to extract a plethora of immune cell parameters (e.g., immune cell migration and interaction, response to therapeutic agents). These simple and powerful methods can be further tailored to simulate the complexity of the TME encompassing the heterogeneity and plasticity of cancer, stromal and immune cells subtypes, as well as their reciprocal interactions as drivers of cancer evolution. The compliance of these rapidly evolving technologies with live-cell high-content imaging can lead to the generation of large informative datasets, bringing forth new challenges. Indeed, the triangle &#39;&#39;co-cultures/microscopy/advanced data analysis&#34; sets the path towards a precise problem parametrization that may assist tailor-made therapeutic protocols. We expect that future integration of cancer-immune on-a-chip with artificial intelligence for high-throughput processing will synergize a large step forward in leveraging the capabilities as predictive and preclinical tools for precision and personalized oncology.

In the age of immunotherapy and single-cell genomic profiling, cancer biology requires novel in vitro and computational tools for investigating the tumor-immune interface in a proper spatiotemporal context. We describe protocols to exploit tumor-immune microfluidic co-cultures in 2D and 3D settings, compatible with dynamic, multiparametric monitoring of cellular functions.

Complex disease models demand cutting-edge tools able to deliver physiologically and pathologically relevant, actionable insights, and unveil otherwise ...

Advanced Two-Layered 3D Co-Culture System for Epithelial and Fibroblast Cells

Establishing a Three-Dimensional Coculture Module of Epithelial Cells Using Nanofibrous Membranes

Technical hurdles in a culture of epithelial cells include dedifferentiation and loss of function. Biomimetic three-dimensional (3D) cell culture methods can enhance cell culture efficiency. This study introduces an advanced two-layered culture system intended to cultivate epithelial cells as tissue-like layers with the culture of fibroblasts within a 3D environment. Polyvinyl alcohol (PVA) and poly(&#949;-caprolactone) (PCL) nanofibrous membranes (NMs) were fabricated via electrospinning and utilized as a physiologically relevant extracellular matrix for the culture of epithelial cells and fibroblasts, respectively. In the upper insert wells, lung epithelial cells were cultivated on the PVA NM, and in the lower chambers, fibroblasts were cultured on the PCL NM. This configuration eliminates direct cell-cell contact and facilitates the examination of paracrine signaling mediated by soluble factors. Confocal microscopy was employed to analyze the distribution, growth pattern, and expression of intracellular proteins, including zona occludens in epithelial cells. Z-stacking techniques enabled detailed 3D reconstructions, providing precise insights into the integrity of tight junctions and spatial organization within the epithelial layer. Scanning electron microscopy (SEM) assessed the morphological characteristics of cell types on the nanofibrous membranes. SEM imaging revealed intricate cell surface structures and interactions with the nanofibers, offering a comprehensive perspective on cellular architecture and cell interaction with nanofibrous structure. The Cell Counting Kit-8 (CCK-8) assay is a simple method for measuring epithelial cell and fibroblast growth rates over time. It provides the proliferative behaviors and potential synergistic effects of coculturing these cells. These findings highlight the effectiveness of a simple insert co-culture system for simultaneous culture of fibroblasts and epithelial cells, which is crucial in various physiological and pharmacological contexts, including epithelial tissue regeneration, tumor microenvironment with endothelial, immune, and other stroma cells, toxicity assay, and drug activity test.

Author Spotlight: Advancing 3D Coculture Systems with PVA-PCL Nanofibrous Membranes 

Here, we demonstrate how epithelial cells cultured with fibroblasts in the nanofibrous membrane-based two-layer system can stably adhere to and grow on the membrane.

Technical hurdles in a culture of epithelial cells include dedifferentiation and loss of function. Biomimetic three-dimensional (3D) cell culture methods ...

Development of an Insert Co-culture System of Two Cellular Types in the Absence of Cell-Cell Contact

The role of secreted soluble factors in the modification of cellular responses is a recurrent theme in the study of all tissues and systems. In an attempt to make straightforward the very complex relationships between the several cellular subtypes that compose multicellular organisms, in vitro techniques have been developed to help researchers acquire a detailed understanding of single cell populations. One of these techniques uses inserts with a permeable membrane allowing secreted soluble factors to diffuse. Thus, a population of cells grown in inserts can be co-cultured in a well or dish containing a different cell type for evaluating cellular changes following paracrine signaling in the absence of cell-cell contact. Such insert co-culture systems offer various advantages over other co-culture techniques, namely bidirectional signaling, conserved cell polarity and population-specific detection of cellular changes. In addition to being utilized in the field of inflammation, cancer, angiogenesis and differentiation, these co-culture systems are of prime importance in the study of the intricate relationships that exist between the different cellular subtypes present in the central nervous system, particularly in the context of neuroinflammation. This article offers general methodological guidelines in order to set up an experiment in order to evaluating cellular changes mediated by secreted soluble factors using an insert co-culture system. Moreover, a specific protocol to measure the neuroinflammatory effects of cytokines secreted by lipopolysaccharide-activated N9 microglia on neuronal PC12 cells will be detailed, offering a concrete understanding of insert co-culture methodology.

In multicellular organisms, secreted soluble factors elicit responses from different cell types as a result of paracrine signaling. Insert co-culture systems offer a simple way to assess the changes mediated by secreted soluble factors in the absence of cell-cell contact.

The role of secreted soluble factors in the modification of cellular responses is a recurrent theme in the study of all tissues and systems. In an attempt ...

An Innovative 3D-Printed Insert Designed to Enable Straightforward 2D and 3D Cell Cultures

The classical analyses of indirect communication between different cell types necessitate the use of conditioned media. Moreover, the production of conditioned media remains time-consuming and far from physiological and pathological conditions. Although a few models of co-culture are commercially available, they remain restricted to specific assays and are mostly for two types of cells. 
Here, 3D-printed inserts are used that are compatible with numerous functional assays. The insert allows the separation of one well of a 6-well plate into four compartments. A wide range of combinations can be set. Moreover, windows are designed in each wall of the compartments so that potential intercellular communication between every compartment is possible in the culture medium in a volume-dependent manner. For example, paracrine intercellular communication can be studied between four cell types in monolayer, in 3D (spheroids), or by combining both. In addition, a mix of different cell types can be seeded in the same compartment in 2D or 3D (organoids) format. The absence of a bottom in the 3D-printed inserts allows the usual culture conditions on the plate, possible coating on the plate containing the insert, and direct visualization by optical microscopy. The multiple compartments provide the possibility to collect different cell types independently or to use, in each compartment, different reagents for RNA or protein extraction. In this study, a detailed methodology is provided to use the new 3D-printed insert as a co-culture system. To demonstrate several capacities of this flexible and simple model, previously published functional assays of cell communication were performed in the new 3D-printed inserts and were demonstrated to be reproducible. The 3D-printed inserts and the conventional cell culture using conditioned media led to similar results. In conclusion, the 3D-printed insert is a simple device that can be adapted to numerous models of co-cultures with adherent cell types.

In this paper, a newly designed 3D-printed insert is presented as a model of co-culture and validated through the study of the paracrine intercellular communication between endothelial cells and keratinocytes.

The classical analyses of indirect communication between different cell types necessitate the use of conditioned media. Moreover, the production of ...

Co-culture Model Using Two Types of Adherent Cell Lines

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