This study was made in collaboration with BASF Beauty Care Solutions. Ms. Charlie Colin-Pierre is a BASF /CNRS-funded PhD fellow.
We wish to thank Mr. Mehdi Sellami for the conception of the 3D-printed inserts.

NOTE: The 3D inserts (Figure 1A) are commercially procured and are printed using a photopolymer resin that is biocompatible with cell culture and autoclaving (see the Table of Materials). In this section, a detailed protocol to establish the co-culture model by inserts is described (see Figure 1B). Some examples of applications are also provided.
1. Placement of the sterilized insert in the 6-well plates
<ol>
	<li>Mix the two components provided in the kit (see Table of Materials), food silicon (reagent A) and catalyst (reagent B), in a ratio of 10:1 (v/v) according to the manufacturer&#39;s instructions. (Figure 1Ba). Use a 70% ethanol sterilized spatula to mix the two components. 
	NOTE: The volume of the silicon mixture to be prepared depends on the number of inserts to be fixed. An excess of catalyst can result in the silicon mixture solidifying too fast.</li>
	<li>Apply the inserts on the silicon mix with tweezers so that the mixture is homogeneously distributed at the bottom edge of the inserts (Figure 1Bb). Place the inserts into the wells of a 6-well plate and apply gentle pressure on the inserts to ensure that the inserts are in close contact with the plate to avoid any leakage of the cell culture medium (Figure 1Bc).</li>
	<li>Put the plate at 37 &#730;C to support the solidification process of the silicon for 1 h. 
	NOTE: The time of solidification depends on the quantity of catalyst that has been added.</li>
	<li>After solidification, sterilize the plates with the inserts by immersing them in a 70% ethanol bath for 30 min to 1 h.</li>
	<li>Discard the alcohol by pipetting and let the plate dry (lid open) overnight in a cell culture hood. 
	&#8203;NOTE: The alcohol must be fully evaporated before performing the next step to avoid cell fixation and toxicity. The ready-to-use plate containing the inserts can be stored for several days before use in dry and sterile conditions at room temperature.</li>
</ol>
2. Coatings such as poly-L-lysine, or poly-HEMA (Optional step)
NOTE: Coating is not performed in this experiment, and the steps are provided to inform regarding the possibility of coating the inserts.
<ol>
	<li>Prepare the coating solution according to the manufacturer&#39;s instructions.</li>
	<li>Consider a volume of 200-400 &#181;L for the largest compartments and a volume of 50-100 &#181;L for the smallest compartments for the coating of the insert. Add the coating solution to the individual compartments.</li>
	<li>Let the coating dry as indicated by the manufacturer under sterile conditions.</li>
</ol>
3. Seeding of the cells
<ol>
	<li>Culture the keratinocytes of the outer root sheath (KORS) and human dermal microvascular endothelial cells (HDMECs) as recommended by the manufacturer. Prepare the cell suspension once the cells reach confluency.
	<ol>
		<li>Discard the medium from the flasks and add 5 mL of trypsin to detach the cells (see Table of Materials).</li>
		<li>Place the flask containing the KORS at 37 &#176;C with 5% CO2 for 5 min. Incubate the flask containing the HDMECs for 5 min at room temperature.</li>
		<li>Mix the trypsin solution containing the KORS with 5 mL of mesenchymal stem cell medium (MSCM) supplemented with 5% fetal bovine serum (FBS) and growth factors (basal medium with supplement kit, see Table of Materials). Mix the trypsin solution containing the HDMECs with 5 mL of endothelial cell medium (ECM) supplemented with 5% FBS and growth factors (see Table of Materials).</li>
		<li>Transfer the cells into a 15 mL of sterile conical tube. Centrifuge the KORS and HDMEC suspensions at 200 x g for 5 min at room temperature.</li>
		<li>Discard the supernatant and resuspend the cells in 2 mL of the respective medium.</li>
		<li>Mix 10 &#181;L of the cell suspension with 10 &#181;L of trypan blue dye (see Table of Materials).</li>
		<li>Add 10 &#181;L of the mix into the chamber of the counting slide.</li>
		<li>Insert the counting slide into the cell counting system (see Table of Materials) and detect the cell number and the viability.</li>
		<li>Prepare the cell suspension at a concentration of 0.5 x 105 cells/mL in the respective medium. 
		NOTE: If the different cell types require different times of adherence and/or to reach the ideal confluency, the cell seeding can be made at different time points according to the cell types.</li>
	</ol>
	</li>
	<li>Distribute 800 &#181;L to 1 mL of the cell suspension into the individual large compartments and 100-150 &#181;L into the individual small compartments with a pipette.
	<ol>
		<li>Seed the KORS at 1 x 105 cells/mL in MSCM supplemented with 5% FBS and growth factors in one of the big compartments.</li>
		<li>Seed HDMEC in ECM supplemented with 5% FBS and growth factors at 2.5 x 103 cells/mL in the small compartments and at 1.25 x 105 cells/mL in the other big compartment. 
		NOTE: The proliferation assay can be performed in the small compartments, and the migration and viability assays can be performed in the big compartments. The concentration of the cells seeded has been optimized according to the manufacturer&#39;s recommendations. This concentration allows for good viability of the cells after 24-48 h of incubation.</li>
	</ol>
	</li>
	<li>Place the cell culture plate at 37 &#730;C with 5% CO2 or under the usual conditions to allow for cell adhesion and/or maturation. 
	NOTE: Incubate the cells for 24-48 h without changing the media. If needed, the medium of the compartments can be changed independently.</li>
</ol>
4. Implementation of the co-culture (&#160;Figure 1Bd)
NOTE: The implementation of the co-culture corresponds to the time when the common medium is added. The addition of a unique medium for all the cell types in the different compartments provides the possibility of paracrine communication between the cells due to the presence of communication windows (ovoid holes in the walls of the 3D-printed inserts). To implement the co-culture, follow steps 4.1-4.3.
<ol>
	<li>Empty the culture media of the different compartments of the inserts using a pipette. In case of a 3D spheroid cell culture, discard the medium very gently.</li>
	<li>Rinse the cells with 1 mL of 37 &#176;C warm PBS in the big compartments and 200 &#181;L of 37 &#176;C warm PBS in the small compartments. Ensure gentle washing to not detach the cells.</li>
	<li>Add 3 mL of a common medium selected to be compatible for all cell types. 
	NOTE: In this study, the basal ECM (without FBS and growth factors) is used. Make sure that the medium covers all the compartments (level above the communication windows [ovoid holes in the walls], as shown in Figure 1A).</li>
	<li>Place the plate containing the co-cultures at 37 &#730;C with 5% CO2 for 24-48 h.</li>
</ol>
5. Cell observation, counting, and scraping
<ol>
	<li>Observe the morphology and count the cell number of the different compartments during the experiment under an optical microscope after 24-48 h of incubation. 
	NOTE: The expected number of cells depends on the cell types used (size, morphology, etc.) and on the compartment size. In this experiment, between 0.5 x 106-1 x 106 KORS/mL and between 0.25 x 106-0.75 x 106 HDMECs/mL are counted in the big compartments.</li>
	<li>Detach the cells using trypsin for cell suspension counting. 
	NOTE: For the cell detachment solution, consider a volume of 100-500 &#181;L for the largest compartments and a volume of 10-50 &#181;L for the smallest compartments.</li>
	<li>Check the viability by using trypan blue staining (see steps 3.1.6-3.1.8).</li>
</ol>
6. Insert cleaning for recycling
<ol>
	<li>Remove the inserts from the 6-well plate at the end of the experiment by a slight twist (Figure 1Be).</li>
	<li>Remove the silicon from the inserts by pulling it off. If necessary, use a spatula to remove the remaining silicon stuck to the walls of the inserts (Figure 1Bf).</li>
	<li>Wash the inserts with conventional cell culture detergents and cleaning materials (example provided in the Table of Materials).</li>
	<li>Sterilize the inserts for future use in an autoclave (solid cycle, 121 &#730;C for 20 min) or by immersing them in a 70% ethanol bath for 1 h. 
	&#8203;NOTE: From this step, two examples of possible assays (proliferation and migration assays) are described using the 3D-printed inserts (Figure 1Bd).</li>
</ol>
7. Cell proliferation assay - WST-1 assay
<ol>
	<li>Follow steps 1-3.1 to culture the cells. 
	NOTE: Follow the step in this section to implement the co-culture system in order to investigate the effect of the KORS secretome on HDMEC proliferation. KORS cells are used to compare the data published previously8.
	<ol>
		<li>Seed the KORS at 1 x 105 cells/mL in mesenchymal stem cell medium (MSCM) supplemented with 5% FBS and growth factors in the big compartments.</li>
		<li>Place the cell culture plate at 37 &#730;C with 5% CO2 for 24 h.</li>
		<li>Seed the HDMECs in endothelial cell medium (ECM) supplemented with 5% FBS and growth factors at 2.5 x 103 cells/mL in the small compartments.</li>
		<li>Place the cell culture plate at 37 &#176;C with 5% CO2 for 24-48 h.</li>
		<li>Discard the media from all the compartments and implement the co-culture system by the addition of 3 mL of non-supplemented basal ECM (common cell culture medium for all the compartments of the 3D-printed inserts).</li>
	</ol>
	</li>
	<li>Dilute WST-1 in the ECM common cell culture medium (1:10 final dilution) to prepare the WST-1 solution. 
	&#8203;NOTE: For the volume of WST-1 solution, prepare at least 500 &#181;L of extra solution for the blank.</li>
	<li>Discard the cell culture medium from the insert by pipetting.</li>
	<li>Add the WST-1 solution to the selected compartments (150 &#181;L for the small compartments and 600 &#181;L for the big compartments). Put the plate at 37 &#730;C with 5% CO2.</li>
	<li>After the optimal 30 min cell incubation time, transfer 100 &#181;L of the incubation medium from each condition on a 96-well plate.</li>
	<li>Assess the colorimetric reaction using a microplate reader between 420 nm and 480 nm.
	<ol>
		<li>Put the plate on the microplate reader and click on the button edit a new protocol.</li>
		<li>Select the specific type of 96-well plate (see Table of Materials) used and the wavelength of 450 nm.</li>
		<li>Click on the button start measurement.</li>
	</ol>
	</li>
</ol>
8. Cell migration assay - two migration chambers device
<ol>
	<li>Follow steps 1-3.1 to culture the cells. 
	NOTE: Follow the steps in this section to implement the co-culture system in order to investigate the effect of the KORS secretome on HDMEC proliferation.
	<ol>
		<li>Seed the KORS at 1 x 105 cells/mL in MSCM supplemented with 5% FBS and growth factors in one of the big compartments.</li>
		<li>Place the cell culture plate at 37 &#730;C with 5% CO2 for 24 h.</li>
		<li>Put the two migration chambers device into the other large compartment of inserts.</li>
		<li>Seed the HDMECs in ECM supplemented with 5% FBS and growth factors at 7 x 105 cells/well of the two migration chambers device.</li>
		<li>Place the cell culture plate at 37 &#176;C with 5% CO2 for 24 h.</li>
		<li>Discard the media and the two migration chambers device after 24 h or at an optimal time according to the cell type that is migrating. Implement the co-culture system by the addition of 3 mL of non-supplemented basal ECM. 
		NOTE: Proceed carefully to not detach the cells. If the cells are really sensitive to detachment induced by the addition of common medium, pull off the two migration chambers device after the addition of the common medium.</li>
	</ol>
	</li>
	<li>Observe and take a picture of the surface covered by the cells at different time points under a phase-contrast microscope at 10x magnification. 
	NOTE: The pictures are taken with a phase-contrast microscope (see Table of Materials). The pictures are saved in a USB key and then analyzed by the wound healing tool plugin of the software (see Table of Materials).</li>
	<li>Measure the uncovered surface using classical quantitative analysis software.
	<ol>
		<li>Open the image on the software and activate the wound healing tool available in the macro list.</li>
		<li>Click on the m button to measure the uncovered surface of the migration image.</li>
		<li>The uncovered surface is calculated according to the following formula: 
		Percentage of coverage = ([mean area without cells at T0 &#8722; area without cells at time T]/mean area without cells at T0) &#215; 100. 
		NOTE: The 3D-printed inserts are totally adapted to most of the techniques of cell biology (such as the pseudotube formation assay, 3D cultures) and for biochemistry experiments (such as the extraction of DNA, RNA, protein).</li>
	</ol>
	</li>
</ol>

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The authors declare no competing financial interests.

Indirect cell communication is commonly investigated using conditioned media or co-culture system devices. Conditioned media preparation is time-consuming upstream in the experiments, and this method is restricted to one-sided effect analyses. The previous study by Colin-Pierre et al.8 using conditioned media was conducted on the indirect cell communication between two cell types (HDMECs and KORS). The data of this previous study demonstrated the effect of KORS conditioned media on HDMEC ...

In vivo, cells communicate with each other either directly (cell contact) or indirectly (by secretion of molecules). To study cell communication, different co-culture models can be developed, such as direct co-culture (the different cell types are in direct interaction in the same well) and compartmentalized co-culture (the different cell types are in indirect interaction in different compartments of a culture system)1. Moreover, conditioned media can be used for co-culture systems, where the indirect interaction is enabled by secreted molecules contained in the conditioned media of an effector cell type being transferred to a responder cell type1.
In the case of paracrine cell communication studies, indirect co-culture systems provide models that strongly reflect cell interactions in vivo. Indirect co-culture systems have been developed and commercialized, allowing the establishment of indirect co-culture models2,3. Unfortunately, most indirect co-culture systems provide only two compartments. Other indirect co-culture systems provide multiple compartments, but they are less scalable as compared to the system reported in the present manuscript. Some of them do not allow a classical visualization under a microscope, and they often present specific application methods. In several studies, the paracrine communication between different cell types is probed by the conditioned media model4,5,6,7. This is an easier way of investigation compared to indirect co-culture systems because it does not necessitate specific methods or materials to be established1. On the other hand, the preparation of conditioned media is time-consuming and provides information only on one-way cell signaling (effector to responder)1.
In this paper, a new, simple way of investigating cell communication is proposed. Allowing the combination of several cell types in direct or indirect interaction and in 2D or 3D formats, the printed inserts present numerous advantages for setting up co-culture models easily. Adapted to be placed into the wells of 6-well plates, the 3D-printed insert is circular and allows separation of the well into four compartments (two large compartments and two small compartments; Figure 1A). The 3D-printed inserts are characterized by the absence of a bottom. Thus, the cells are in direct contact with the plate on which the insert is placed. In addition, each compartment can be coated independently of the others. Moreover, the cell behavior can be easily followed under optical microscopes. The presence of communication windows in each wall of the insert allows the addition, at the optimal time, of a common medium to perform different experiments of co-culture. Numerous combinations of co-culture can be performed to study direct and/or indirect communication between several cell types. For example, a model of indirect co-culture between four different cell types in monolayer and/or in 3D (spheroids) can be designed. A combination of direct and indirect co-culture models can also be performed by mixing different cell types in the same compartment. The effect of complex structures (organoids, tissue explant, etc.) on different cell types could be another example of models that can be made. Moreover, the 3D-printed inserts are compatible with cell biology functional assays (proliferation, migration, pseudotube formation, differentiation, etc.) and with biochemistry tests (the extraction of DNA, RNA, protein, lipids, etc.). Finally, the 3D-printed inserts provide a wide range of experimental schemes of co-culture models with the possibility to combine simultaneously different assays in the same experiment in the different compartments.
Some capacities of the 3D-printed inserts are presented to validate them as a rapid and easy-to-use co-culture model. In comparison to a previously published study conducted on paracrine cell communication, the ability of the 3D-printed inserts to be a valuable co-culture model is demonstrated. To assess this point, the regulation of endothelial cell proliferation and migration by keratinocytes was compared between the 3D-printed insert system and the classical system using conditioned media. The 3D-printed inserts allow for obtaining similar results rapidly as compared to the conventional system using conditioned media. Indeed, the 3D-printed inserts provide a robust model to study cell interactions in both directions without the necessity to produce conditioned media and with the possibility to perform in parallel the proliferation and migration assays in the same experiment.
To conclude, in this paper, a new and ready-to-use model to study cell communication is proposed. Compatible with all adherent cell types, the 3D-printed inserts allow for performing numerous combinations of co-culture that aim at being closer to in vivo conditions.

<table><tbody><tr><td>Autoclave</td><td>Getinge</td><td>APHP</td><td>Solid cycle, 121 &amp;deg;C for 20 min</td></tr><tr><td>Biomed Clear</td><td>Formlabs</td><td>RS-F2-BMCL-01</td><td>Impression performed by 3D-Morphoz company (Reims, France)</td></tr><tr><td>Cell culture detergents&amp;nbsp;</td><td>Tounett</td><td>A18590/0116</td><td></td></tr><tr><td>Cell Proliferation Reagent WST-1</td><td>Roche</td><td>11,64,48,07,001</td><td></td></tr><tr><td>Counting slide</td><td>NanoEnTek</td><td>EVE-050</td><td></td></tr><tr><td>Culture-Insert 2 Well in &amp;mu;-Dish 35 mm</td><td>Ibidi</td><td>80206</td><td>two-migration chambers device.&amp;nbsp;</td></tr><tr><td>Endothelial cell medium</td><td>ScienCell</td><td>1001</td><td>Basal medium +/- 25 mL of fetal bovine serum (FBS, 0025), 5 mL of endothelial cell growth supplement (ECGS, 1052), and 5 mL of penicillin/streptomycin solution (P/S, 0503).</td></tr><tr><td>EVE Automated cell counter&amp;nbsp;</td><td>NanoEnTek</td><td>NESCT-EVE-001E&amp;nbsp;</td><td></td></tr><tr><td>EVOS XL Core</td><td>Fisher Scientific</td><td>AMEX1200</td><td>10x of magnification</td></tr><tr><td>Food silicon reagent and catalyst kit</td><td>Artificina</td><td>RTV 3428 A and B&amp;nbsp;</td><td>(10:1)</td></tr><tr><td>FORM 3B printer</td><td>Formlabs</td><td>PKG-F3B-WSVC-DSP-BASIC</td><td>Impression performed by 3D-Morphoz company</td></tr><tr><td>Human Dermal Microvascular Endothelial Cells (HDMEC)</td><td>ScienCell</td><td>2000</td><td></td></tr><tr><td>Keratinocytes of Outer Root Sheath (KORS )</td><td>ScienCell</td><td>2420</td><td></td></tr><tr><td>Macro Wound Healing Tool Software</td><td>ImageJ</td><td></td><td>Software used for the measurement of the uncovered surface (for migration assays)</td></tr><tr><td>Mesenchymal stem cell medium&amp;nbsp;</td><td>ScienCell</td><td>7501</td><td>Basal medium +/-25 mL of fetal bovine serum (FBS, 0025), 5 mL of mesenchymal stem cell growth supplement (MSCGS, 7552), and 5 mL of penicillin/streptomycin solution (P/S, 0503)</td></tr><tr><td>Microplate reader SPECTRO star NANO</td><td>BMG Labtech</td><td></td><td>BMG LABTECH software</td></tr><tr><td>PBS</td><td>Promocell</td><td>C-40232</td><td>Without Ca&lt;sup&gt;2+&lt;/sup&gt; / Mg&lt;sup&gt;2+&lt;/sup&gt;</td></tr><tr><td>Trypan Blue Stain</td><td>NanoEnTek</td><td>EBT-001</td><td></td></tr><tr><td>Trypsin / EDTA</td><td>Promocell</td><td>C-41020</td><td>Incubation of KORS at 37 &amp;deg;C with 5% CO&lt;sub&gt;2&lt;/sub&gt; for 5 min. Incubation of HDMECs for 5 min at room temperature</td></tr><tr><td>96-well plate Nunclon Delta Surface</td><td>Thermoscientific</td><td>167008</td><td></td></tr></tbody></table>

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 the present work, an optimized co-culture system was described to obtain robust, reliable, and significant data comparable to classical methods through the use of conditioned media. The 3D-printed inserts mimic the in vivo microenvironment conditions of different cell types in interaction by overcoming the difficulties and the time-consuming production of conditioned media upstream in the experiments. A previously published study has been reconducted to analyze the indirect interactions between two cell types...

Watch this Scientific Journal Video about An Innovative 3D-Printed Insert Designed to Enable Straightforward 2D and 3D Cell Cultures at JoVE.com

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

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 ...

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Biology

1.3K Views.  Université de Reims Champagne-Ardenne. 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.

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

Chip-based Three-dimensional Cell Culture in Perfused Micro-bioreactors

We have developed a chip-based cell culture system for the three-dimensional cultivation of cells. The chip is typically manufactured from non-biodegradable polymers, e.g., polycarbonate or polymethyl methacrylate by micro injection molding, micro hot embossing or micro thermoforming. But, it can also be manufactured from bio-degradable polymers. Its overall dimensions are 0.7 1 x 20 x 20 x 0.7 1 mm (h x w x l). The main features of the chips used are either a grid of up to 1156 cubic micro-containers (cf-chip) each the size of 120-300 x 300 x 300 &mu; (h x w x l) or round recesses with diameters of 300 &mu; and a depth of 300 &mu; (r-chip). The scaffold can house 10 Mio. cells in a three-dimensional configuration. For an optimal nutrient and gas supply, the chip is inserted in a bioreactor housing. The bioreactor is part of a closed steril circulation loop that, in the simplest configuration, is additionaly comprised of a roller pump and a medium reservoir with a gas supply. The bioreactor can be run in perfusion, superfusion, or even a mixed operation mode. We have successfully cultivated cell lines as well as primary cells over periods of several weeks. For rat primary liver cells we could show a preservation of organotypic functions for more than 2 weeks. For hepatocellular carcinoma cell lines we could show the induction of liver specific genes not or only slightly expressed in standard monolayer culture. The system might also be useful as a stem cell cultivation system since first differentiation experiments with stem cell lines were promising.

We describe a chip-based platform for the three-dimensional cultivation of cells in micro-bioreactors. One chip can house up to 10 Mio. cells that can be cultivated under precisely defined conditions with regard to fluid flow, oxygen tension etc. in a sterile, closed circulation loop.

We have developed a chip-based cell culture system for the three-dimensional cultivation of cells. The chip is typically manufactured from ...

Ordering Single Cells and Single Embryos in 3D Confinement: A New Device for High Content Screening

Biological cells are usually observed on flat (2D) surfaces. This condition is not physiological, and phenotypes and shapes are highly variable. Screening based on cells in such environments have therefore serious limitations: cell organelles show extreme phenotypes, cell morphologies and sizes are heterogeneous and/or specific cell organelles cannot be properly visualized. In addition, cells in vivo are located in a 3D environment; in this situation, cells show different phenotypes mainly because of their interaction with the surrounding extracellular matrix of the tissue. In order to standardize and generate order of single cells in a physiologically-relevant 3D environment for cell-based assays, we report here the microfabrication and applications of a device for in vitro 3D cell culture. This device consists of a 2D array of microcavities (typically 105 cavities/cm2), each filled with single cells or embryos. Cell position, shape, polarity and internal cell organization become then normalized showing a 3D architecture. We used replica molding to pattern an array of microcavities, &#8216;eggcups&#8217;, onto a thin polydimethylsiloxane (PDMS) layer adhered on a coverslip. Cavities were covered with fibronectin to facilitate adhesion. Cells were inserted by centrifugation. Filling percentage was optimized for each system allowing up to 80%. Cells and embryos viability was confirmed. We applied this methodology for the visualization of cellular organelles, such as nucleus and Golgi apparatus, and to study active processes, such as the closure of the cytokinetic ring during cell mitosis. This device allowed the identification of new features, such as periodic accumulations and inhomogeneities of myosin and actin during the cytokinetic ring closure and compacted phenotypes for Golgi and nucleus alignment. We characterized the method for mammalian cells, fission yeast, budding yeast, C. elegans with specific adaptation in each case. Finally, the characteristics of this device make it particularly interesting for drug screening assays and personalized medicine.

We report a device and a new method to study cells and embryos. Single cells are precisely ordered in microcavity arrays. Their 3D confinement is a step towards 3D environments encountered in physiological conditions and allows organelle orientation. By controlling cell shape, this setup minimizes variability reported in standard assays.

Biological cells are usually observed on flat (2D) surfaces. This condition is not physiological, and phenotypes and shapes are highly variable. Screening ...

Bioengineering

3D Microtissues for Injectable Regenerative Therapy and High-throughput Drug Screening

To upgrade traditional 2D cell culture to 3D cell culture, we have integrated microfabrication with cryogelation technology to produce macroporous microscale cryogels (microcryogels), which can be loaded with a variety of cell types to form 3D microtissues. Herein, we present the protocol to fabricate versatile 3D microtissues and their applications in regenerative therapy and drug screening. Size and shape-controllable microcryogels can be fabricated on an array chip, which can be harvested off-chip as individual cell-loaded carriers for injectable regenerative therapy or be further assembled on-chip into 3D microtissue arrays for high-throughput drug screening. Due to the high elastic nature of these microscale cryogels, the 3D microtissues exhibit great injectability for minimally invasive cell therapy by protecting cells from mechanical shear force during injection. This ensures enhanced cell survival and therapeutic effect in the mouse limb ischemia model. Meanwhile, assembly of 3D microtissue arrays in a standard 384-multi-well format facilitates the use of common laboratory facilities and equipment, enabling high-throughput drug screening on this versatile 3D cell culture platform.

This protocol describes the fabrication of elastic 3D macroporous microcryogels by integrating microfabrication with cryogelation technology. Upon loading with cells, 3D microtissues are generated, which can be readily injected in vivo to facilitate regenerative therapy or assembled into arrays for in vitro high-throughput drug screening.

To upgrade traditional 2D cell culture to 3D cell culture, we have integrated microfabrication with cryogelation technology to produce macroporous ...

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease modeling. Self-assembled tissues offer advantages over scaffold-based tissue engineering, such as enhanced matrix deposition, strength, and function. However, there are few available methods for fabricating 3D tissues without seeding cells on or within a supporting scaffold. Previously, we developed a system for fabricating self-assembled tissue rings by seeding cells into non-adhesive agarose wells. A polydimethylsiloxane (PDMS) negative was first cast in a machined polycarbonate mold, and then agarose was gelled in the PDMS negative to create ring-shaped cell seeding wells. However, the versatility of this approach was limited by the resolution of the tools available for machining the polycarbonate mold. Here, we demonstrate that 3D-printed plastic can be used as an alternative to machined polycarbonate for fabricating PDMS negatives. The 3D-printed mold and revised mold design is simpler to use, inexpensive to produce, and requires significantly less agarose and PDMS per cell seeding well. We have demonstrated that the resulting agarose wells can be used to create self-assembled tissue rings with customized diameters from a variety of different cell types. Rings can then be used for mechanical, functional, and histological analysis, or for fabricating larger and more complex tubular tissues.

This protocol describes a platform for fabricating self-assembled tissue rings in variable sizes using a customized 3D-printed plastic mold. PDMS negatives are cured in the 3D-printed mold; then agarose is cast in the cured PDMS negatives. Cells are seeded into the resulting agarose wells where they aggregate into tissue rings.

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease ...

Bioprintable Alginate/Gelatin Hydrogel 3D In Vitro Model Systems Induce Cell Spheroid Formation

The cellular, biochemical, and biophysical heterogeneity of the native tumor microenvironment is not recapitulated by growing immortalized cancer cell lines using conventional two-dimensional (2D) cell culture. These challenges can be overcome by using bioprinting techniques to build heterogeneous three-dimensional (3D) tumor models whereby different types of cells are embedded. Alginate and gelatin are two of the most common biomaterials employed in bioprinting due to their biocompatibility, biomimicry, and mechanical properties. By combining the two polymers, we achieved a bioprintable composite hydrogel with similarities to the microscopic architecture of a native tumor stroma. We studied the printability of the composite hydrogel via rheology and obtained the optimal printing window. Breast cancer cells and fibroblasts were embedded in the hydrogels and printed to form a 3D model mimicking the in vivo microenvironment. The bioprinted heterogeneous model achieves a high viability for long-term cell culture (&#62; 30 days) and promotes the self-assembly of breast cancer cells into multicellular tumor spheroids (MCTS). We observed the migration and interaction of the cancer-associated fibroblast cells (CAFs) with the MCTS in this model. By using bioprinted cell culture platforms as co-culture systems, it offers a unique tool to study the dependence of tumorigenesis on the stroma composition. This technique features a high-throughput, low cost, and high reproducibility, and it can also provide an alternative model to conventional cell monolayer cultures and animal tumor models to study cancer biology.

Bioprintable Alginate/Gelatin Hydrogel 3D In Vitro Model Systems Induce Cell Spheroid Formation

We developed a heterogeneous breast cancer model consisting of immortalized tumor and fibroblast cells embedded in a bioprintable alginate/gelatin bioink. The model recapitulates the in vivo tumor microenvironment and facilitates the formation of multicellular tumor spheroids, yielding insight into the mechanisms driving tumorigenesis.

The cellular, biochemical, and biophysical heterogeneity of the native tumor microenvironment is not recapitulated by growing immortalized cancer cell ...

Initial 3D Cell Cluster Control in a Hybrid Gel Cube Device for Repeatable Pattern Formations

The importance of in vitro 3D cultures is considerably emphasized in cell/tissue culture. However, the lack of experimental repeatability is one of its restrictions. Producing few repeatable results of pattern formation deteriorates the analysis of the mechanisms underlying the self-organization. Reducing variation in initial culture conditions, such as the cell density and distribution in the extracellular matrix (ECM), is crucial to enhance the repeatability of a 3D culture. In this article, we demonstrate a simple but robust procedure for controlling the initial cell cluster shape in a 3D extracellular matrix to obtain highly repeatable pattern formations. A micromold with a desired shape was fabricated by using photolithography or a machining process, and it formed a 3D pocket in the ECM contained in a hybrid gel cube (HGC). Highly concentrated cells were then injected in the pocket so that the cell cluster shape matched with the fabricated mold shape. The employed HGC allowed multi-directional scanning by its rotation, which enabled high-resolution imaging and the capture of the entire tissue structure even though a low-magnification lens was used. Normal human bronchial epithelial cells were used to demonstrate the methodology.&#160;

We present a procedure for controlling the initial cell cluster shape in a 3D extracellular matrix to obtain a repeatable pattern formation. A cubic device containing two different hydrogels is employed to achieve multi-directional imaging for tissue pattern formation.

The importance of in vitro 3D cultures is considerably emphasized in cell/tissue culture. However, the lack of experimental repeatability is one of its ...

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and chemical complexity of living tissues and mimic in vivo tissue functions. Recent advances in microfabrication technologies have facilitated the development of 3D in vitro environments in which cells can be integrated into a well-defined extracellular matrix (ECM) and a defined set of soluble or matrix associated biomolecules. However, technological barriers have limited their widespread use in research laboratories. Here, we describe a method to construct simple devices for 3D culture and experimentation with cells and multicellular organoids in 3D microenvironments with a defined chemoattractant gradient. We illustrate the use of this platform for analysis of the response of epithelial cells and organoids to gradients of growth factors, such as epidermal growth factor (EGF). EGF gradients were stable in the devices for several days leading to directed branch formation in breast organoids. This analysis allowed us to conclude that collective gradient sensing by groups of cells is more sensitive vs. single cells. We also describe the fabrication method, which does not require photolithography facilities nor advanced soft lithography techniques. This method will be helpful to study 3D cellular behaviors in the context of the analysis of development and pathological states, including cancer.

We describe a method to construct devices for 3D culture and experimentation with cells and multicellular organoids. This device allows analysis of cellular responses to soluble signals in 3D microenvironments with defined chemoattractant gradients. Organoids are better than single cells at detection of weak noisy inputs.

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and ...

Generation of Three-Dimensional Spheroids/Organoids from Two-Dimensional Cell Cultures Using a Novel Stamp Device

Three-dimensional (3D) cell cultures provide a more accurate representation of the in vivo microenvironment than conventional two-dimensional (2D) cultures, since they promote enhanced interactions among cells and the extracellular matrix.&#160;This study aimed to develop an efficient, cost-effective, and reproducible methodology to generate 3D cell structures (spheroids/organoids) using an innovative stamp-based system to create microwells in agarose molds.A novel stamp was used to produce 663 microwells per well of a 6-well plate, providing an ideal environment for cell aggregation. Primary porcine pancreatic islet cells were seeded into these microwells, where they aggregated to form spheroids/organoids. The cultures were incubated at 37 &#176;C under 5% CO2, and the medium was replaced every 3 days. Spheroid formation was periodically monitored, and samples were collected for characterization.&#160;The method successfully generated uniform and high-quality spheroids, reducing experimental variability, minimizing manipulation, and enhancing cell interactions. The use of agarose-based micropattern molds provided a simplified, controlled environment for 3D cultures, offering a standardized and cost-effective solution.This methodology supports applications for drug testing and tissue engineering, offering a practical and scalable platform for 3D cell culture models that can be easily implemented in various laboratory settings.

This study presents a cost-effective and efficient methodology for generating 3D cell structures using a stamp-based system to create microwells in agarose molds. The system promotes the formation of uniform spheroids/organoids, thus improving cell interactions. This approach reduces experimental variability and supports applications in drug testing and tissue engineering.

Three-dimensional (3D) cell cultures provide a more accurate representation of the in vivo microenvironment than conventional two-dimensional (2D) ...

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 ...

A High-Throughput Platform for Culture and 3D Imaging of Organoids

The characterization of a large number of three-dimensional (3D) organotypic cultures (organoids) at different resolution scales is currently limited by standard imaging approaches. This protocol describes a way to prepare microfabricated organoid culture chips, which enable multiscale, 3D live imaging on a user-friendly instrument requiring minimal manipulations and capable of up to 300 organoids/h imaging throughput. These culture chips are compatible with both air and immersion objectives (air, water, oil, and silicone) and a wide range of common microscopes (e.g., spinning disk, point scanner confocal, wide field, and brightfield). Moreover, they can be used with light-sheet modalities such as the single-objective, single-plane illumination microscopy (SPIM) technology (soSPIM). 
The protocol described here gives detailed steps for the preparation of the microfabricated culture chips and the culture and staining of organoids. Only a short length of time is required to become familiar with, and consumables and equipment can be easily found in normal biolabs. Here, the 3D imaging capabilities will be demonstrated only with commercial standard microscopes (e.g., spinning disk for 3D reconstruction and wide field microscopy for routine monitoring).

This paper presents a fabrication protocol for a new type of culture substrate with hundreds of microcontainers per mm2, in which organoids can be cultured and observed using high-resolution microscopy. The cell seeding and immunostaining protocols are also detailed.

The characterization of a large number of three-dimensional (3D) organotypic cultures (organoids) at different resolution scales is currently limited by ...

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

Summary

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Chapters in this video

Chip-based Three-dimensional Cell Culture in Perfused Micro-bioreactors

Ordering Single Cells and Single Embryos in 3D Confinement: A New Device for High Content Screening

3D Microtissues for Injectable Regenerative Therapy and High-throughput Drug Screening

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Bioprintable Alginate/Gelatin Hydrogel 3D In Vitro Model Systems Induce Cell Spheroid Formation

Initial 3D Cell Cluster Control in a Hybrid Gel Cube Device for Repeatable Pattern Formations

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Generation of Three-Dimensional Spheroids/Organoids from Two-Dimensional Cell Cultures Using a Novel Stamp Device

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

A High-Throughput Platform for Culture and 3D Imaging of Organoids