We thank the staff of the Second Core Lab, Department of Medical Research, National Taiwan University Hospital for their technical support.

All the procedures followed in this study accorded with the Association for Research in Vision and Ophthalmology Statement for Use of Animals in Ophthalmic and Vision Research and were approved by the Institutional Animal Care and Use Committee of National Taiwan University Hospital.
1. Isolation, Primary Culture Preparation, and Immunostaining of Bovine CECs
<ol>
	<li>Acquire fresh bovine eyes from a local abattoir.</li>
	<li>Disinfect the eyes in a 10% w/v povidone-iodine solution for 3 min. Wash them with phosphate-buffered saline (PBS) solution.</li>
	<li>Harvest the corneal button with a scalpel and scissors under sterile conditions. Peel the Descemet&#39;s membrane with forceps under a dissecting microscope (note that in this study, the bovine eyes were enucleated by a local abattoir; therefore, the first study procedure was the disinfection of the preenucleated eyes in the laboratory).</li>
	<li>Incubate the Descemet&#39;s membrane in 1 ml of trypsin at 37 &#176;C for 30 min. Collect the bovine CECs by centrifugation at 112 x g for 5 min. Resuspend the cells in 1 ml of supplemented hormonal epithelial medium (SHEM) containing equal volumes of HEPES-buffered Dulbecco&#39;s modified Eagle medium and Ham&#39;s F12 medium, supplemented with 5% fetal bovine serum, 0.5% dimethyl sulfoxide, 2 ng/ml of human epidermal growth factor, 5 mg/ml of insulin, 5 mg/ml of transferrin, 5 ng/ml of selenium, 1 nmol/l of cholera toxin, 50 mg/ml of gentamicin, and 1.25 mg/ml of amphotericin B.</li>
	<li>Seed the cells (approximately 1 x 105 cells per eye) into a 6 cm dish. Culture them in the SHEM. Incubate the dish at 37 &#176;C in an atmosphere of 5% CO2 in air. Change the culture medium every 3 days.</li>
	<li>When the cells reach confluence, wash them in PBS and incubate them in 1 ml of trypsin at 37 &#176;C for 5 min. Collect them by centrifugation at 112 x g for 5 min. Re-suspend the cell pellet in 1 ml of the SHEM.
	<ol>
		<li>Count the cells in a hemocytometer. Seed the cells on cover slides at a density of 1 x 104 per well in a 24-well plate, and culture the cells in the SHEM. For investigating the EnMT-suppressing effect of marimastat, incubate the cells in SHEM with 10 &#181;M of marimastat added into the culture medium, and change the culture medium every 3 days.</li>
	</ol>
	</li>
	<li>Fix the cells at an indicated time point with 250 &#181;l of 4% paraformaldehyde, pH 7.4, for 30 min at room temperature. Permeabilize with 250 &#181;l of 0.5% Triton X-100 for 5 min. Block with 10% bovine serum albumin for 30 min.</li>
	<li>Incubate the cells with primary antibodies against active beta-catenin (ABC), snail, and slug overnight at 4 &#176;C. The dilution of the primary antibodies used is 1:200. The antibodies are diluted in antibody diluent composed of 10 mM PBS, 1% w/v bovine serum albumin, and 0.09% w/v sodium azide.</li>
	<li>Wash the cells twice with PBS for 15 min, and incubate them with the Alexa Fluor-conjugated secondary antibody (1:100 in antibody diluent) at room temperature for 1 hr.</li>
	<li>Counterstain the cell nucleus by covering the cells with 2 &#181;g/ml of 4&#39;,6-diamidino-2-phenylindole, wash the cells twice with PBS for 15 min, and mount them with anti-fading mounting solution.</li>
	<li>Obtain immunofluorescent images at the excitation wavelengths of 405 and 488 nm by using a laser scanning confocal microscope with 20X objective magnification.</li>
</ol>
2. Rat Corneal Endothelium Cryoinjury Model and Intracameral Injection
<ol>
	<li>Anesthetize 12 week-old male Sprague-Dawley rats with intramuscular injections of 2% xylazine (5.6 mg/kg) and tiletamine plus zolazepam (18 mg/kg). Gently pinch the skin of the animals to confirm proper anesthesia in the absence of skin twitching.</li>
	<li>Instill one drop of 0.5% proparacaine hydrochloride to the right eye of each rat to minimize eye pain and the blink reflex. Instill tetracycline ointment to the left eye to prevent corneal dryness.</li>
	<li>Cool a stainless steel probe (diameter = 3 mm) in liquid nitrogen. Apply the stainless steel probe to the central cornea of the right eye for 30 sec. Frequently instill PBS to the right eye during the procedure to prevent corneal dryness.</li>
	<li>Instill 0.1% atropine and 0.3% gentamicin sulfate immediately after cryoinjury and once daily to relieve ocular pain resulting from ciliary spasm and to prevent infection.
	<ol>
		<li>After the procedure, keep the rats warm using a heat lamp, and observe their recovery every 15 min after anesthesia until they regain motor control. Additionally, apply tetracycline ointment to the right eye to prevent corneal dryness during the recovery period.</li>
	</ol>
	</li>
	<li>Repeat the corneal cryoinjury for 3 consecutive days.</li>
	<li>For delivering marimastat or bFGF into the anterior chamber of the rat eyes, anesthetize the rats as described previously. Instill one drop of 0.5% proparacaine hydrochloride into the right eye to minimize eye pain and the blink reflex.</li>
	<li>Irrigate the ocular surface with sterile PBS. Perform anterior chamber paracentesis under an operating microscope by inserting a 30 G needle attached to a 1 ml syringe at the paralimbal clear cornea in a plane above and parallel to the iris.</li>
	<li>Turn the needle bevel up, and slightly depress the corneal wound to drain some aqueous humor and reduce the intraocular pressure. Inject 0.02 ml of the drug intracamerally. Gently compress the needle tract with a cotton tip during the needle withdrawal.</li>
	<li>Photograph the external eye at an indicated time point under the operating microscope.</li>
</ol>
3. Harvesting the Rat Corneal Button and Immunostaining
<ol>
	<li>To euthanize the rats, place them in a euthanasia chamber and infuse 100% CO2 at a fill rate of 10-30% of the chamber volume per minute. Maintain CO2 infusion for an additional minute after lack of respiration and faded eye color.</li>
	<li>Penetrate the rat eye at the limbus with a sharp blade. Cut the corneas with corneal scissors along the limbus. Flatten the corneas on a slide. Make additional radial incisions if the corneas curl up.</li>
	<li>Fix the corneas with 250 &#181;l of 4% paraformaldehyde, pH 7.4, for 30 min at room temperature. Permeabilize with 250 &#181;l of 0.5% Triton X-100 for 5 min, and block with 10% bovine serum albumin for 30 min.</li>
	<li>Incubate the corneas with primary antibodies against ABC overnight at 4 &#176;C with a dilution of 1:200 in antibody diluent. Wash the corneas twice with PBS for 15 min, and incubate them with the secondary antibody (1:100 in antibody diluent) at room temperature for 1 hr. Counterstain the cell nucleus by covering the cells with 2 &#181;g/ml of 4&#39;,6-diamidino-2-phenylindole, and wash the cells twice with PBS for 15 min.</li>
	<li>Mount the corneas in anti-fading mounting solution. Obtain the immunofluorescent images at excitation wavelengths of 405 and 561 nm with a laser scanning confocal microscope at 20X objective magnification.</li>
</ol>

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The authors have no competing financial interests to declare.

CECs are known for their propensity to undergo EnMT during cell proliferation. To develop strategies for suppressing the EnMT process for therapeutic purposes, a thorough understanding of the EnMT mechanism is necessary. We described 2 models to investigate EnMT, namely the bovine CEC in vitro culture model and rat corneal endothelium cryoinjury model. Our results demonstrated the EnMT process in both models. Furthermore, the EnMT-suppressing effect of marimastat was reproduced in both models, suggesting that these 2 models share the same mechanism.
The bovine CEC in vitro culture model offers ease of manipulation. In addition, compared with the human or primate CEC in vitro culture models employed in previous studies17,18, bovine eyes are larger and easier to acquire, and thus have more CECs available. In our study, we acquired the enucleated bovine eyes from a local abattoir. Because of the fresh nature of the bovine eyes, the exact number of bovine CECs harvested is subject to variation, at approximately 1 x 105 cells per eye. By contrast, the number of human CECs in a normal cornea is approximately 3 x 105 per eye. This number is lower in study-grade corneas and is even lower in residual corneal rims after transplantation. Manipulations during the harvesting procedure will further reduce the number of cells obtained. Furthermore, bovine CECs can proliferate and undergo EnMT spontaneously; therefore, the bovine CEC in vitro culture model is useful in investigating the EnMT mechanism and screening EnMT-suppressing chemicals, such as marimastat. Although there remains concern regarding species-related differences, such as the proliferative capacity of CECs, our results demonstrated that the EnMT signaling pathway of bovine CECs is similar to that of human CECs, including the activation of Wnt/&#946;-catenin18,19.
During the isolation of bovine CECs, peeling the Descemet&#39;s membrane is critical. In some bovine eyes, the Descemet&#39;s membrane may have tight adhesion with the corneal stroma, leading to excessive stromal tissue on the peeled Descemet&#39;s membrane. Further trypsinization may lead to the release of stromal keratocytes that transform into corneal fibroblasts, which affect cell purity and therefore the experimental results. In our study, we peeled the Descemet&#39;s membrane carefully under a microscope. To further ensure cell purity, we first cultured the harvested cells in a 6 cm dish until cell confluence. Only when the cells were hexagonal in shape were they used in further experiments.
To further substantiate the findings of the bovine CEC in vitro culture model, we used the rat corneal endothelium cryoinjury model adopted in previous studies20,21. After cryoinjury, the rat CECs underwent EnMT during regeneration, manifested by the nuclear translocation of active &#946;-catenin, indicating that activation of Wnt/&#946;-catenin signaling is conserved among species during CEC regeneration. In addition, this model is useful in investigating the function of CECs because low CEC function leads to obvious corneal edema. Combined with other equipments, such as ultrasound biomicroscope, anterior segment optical coherence tomography, and confocal microscopy, corneal thickness can be quantitatively evaluated and thus reflect CEC function.
To stimulate the regeneration of CECs and suppress EnMT after wound healing, we administered intracameral injections of bFGF followed by marimastat injection. The treatment significantly reduced the extent of corneal edema. Previous studies have used the topical application of CEC growth-stimulating agents, such as ROCK inhibitor, and EnMT-suppressing agents, such as Notch inhibitor21,22. However, the penetration of drugs into the CEC layer is limited by the corneal epithelium and stroma, which may influence the treatment efficacy23. In contrast to topical application, intracameral injection enables direct access to the corneal endothelium by introducing drugs directly into the anterior chamber. Therefore, the growth-stimulating and EnMT-suppressing effect of chemicals can be assessed unbiasedly following cryoinjury. In our study, we performed anterior chamber paracentesis to lower the intraocular pressure before intracameral injection. Without paracentesis, an abrupt increase in intraocular pressure causes corneal edema or even prolapse of the iris through the needle tract. Gently compressing the tract during needle withdrawal aids in sealing the wound and preventing intraocular infection.

Corneal endothelial cells (CECs) play a vital role in maintaining corneal clarity and thus visual acuity by regulating the hydration status of the corneal stroma through active pumping1. Because of the limited proliferative potential of human CECs, the cell number decreases with age, and the repair of corneal endothelial wounds following injury is usually achieved through cell enlargement and migration, rather than cell mitosis2. When the CEC count decreases below a threshold of approximately 500 cells/mm2, the dehydration status of the corneal stroma cannot be maintained, leading to bullous keratopathy and vision impairment3,4.
The limited proliferative potential of human CECs has been attributed to several factors, including reduced expression of the epidermal growth factor and its receptor in aging cells5, antiproliferative TGF&#946;2 in the aqueous humor6, and contact inhibition2,7. Although some growth factors, such as basic fibroblast growth factor (bFGF), can increase proliferation in a cultured human corneal endothelium, the culture efficiency remains limited8,9. Furthermore, CECs may undergo a phenotypic change during ex vivo expansion, resembling epithelial-mesenchymal transition (EMT)10-13. Endothelial-mesenchymal transition (EnMT) is characterized by cell junction destabilization, apical-basal polarity loss, cytoskeletal rearrangement, alpha smooth muscle actin expression, and type I collagen secretion14. All of these characteristics may abrogate the normal function of CECs, hampering the use of ex vivo cultured CECs in tissue engineering. Moreover, EnMT has been associated with the pathogenesis of several corneal endothelial diseases, including Fuchs endothelial corneal dystrophy and retrocorneal membrane formation15,16. Therefore, understanding the mechanism of EnMT may aid in manipulating the EnMT process and facilitate the regeneration of CECs to enable competent function. 
In this study, we described a method for isolating bovine CECs from the corneal button. In the primary culture in vitro, the EnMT process, including a phenotypic change, the nuclear translocation of &#946;-catenin, and EMT regulators snail and slug, was observed. We further described a method for demonstrating EnMT in vivo by using a rat corneal endothelium cryoinjury model. Using these 2 models, we demonstrated that marimastat, a broad-spectrum matrix metalloproteinase (MMP) inhibitor, can suppress the EnMT process. The described protocols facilitate the detailed analysis of the EnMT mechanism and the development of strategies for manipulating the EnMT process for further clinical application.

<table border="0" cellpadding="0" cellspacing="0" width="1447">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:695px;">trypsin</td>
			<td style="width:269px;">ThermoFisher Scientific</td>
			<td style="width:143px;">12604-013</td>
			<td style="width:340px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s modified Eagle medium and Ham&#39;s F12 medium</td>
			<td>ThermoFisher Scientific</td>
			<td>11330</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">fetal bovine serum</td>
			<td>ThermoFisher Scientific</td>
			<td>26140-079</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">dimethyl sulfoxide</td>
			<td>Sigma</td>
			<td>D2650</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">human epidermal growth factor</td>
			<td>ThermoFisher Scientific</td>
			<td>PHG0311</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">insulin, transferrin, selenium&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>41400-045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">cholera toxin</td>
			<td>Sigma</td>
			<td>C8052-1MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">gentamicin</td>
			<td>ThermoFisher Scientific</td>
			<td>15750-060</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">amphotericin B</td>
			<td>ThermoFisher Scientific</td>
			<td>15290-026</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">paraformaldehyde</td>
			<td>Electron Microscopy Sciences</td>
			<td>111219</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton X-100</td>
			<td>Sigma</td>
			<td>T8787&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">bovine serum albumin</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">marimastat</td>
			<td>Sigma</td>
			<td>M2699-25MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">anti-active beta-catenin antibody</td>
			<td>Millpore</td>
			<td>05-665</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">anti-snail antibody</td>
			<td>Santa cruz</td>
			<td>sc28199</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">anti-slug antibody</td>
			<td>Santa cruz</td>
			<td>sc15391</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">goat anti-mouse IgG (H+L) secondary antibody</td>
			<td>ThermoFisher Scientific</td>
			<td>A-11001</td>
			<td>for staining of ABC of bovine CECs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">goat anti-mouse IgG (H+L) secondary antibody</td>
			<td>ThermoFisher Scientific</td>
			<td>A-11003</td>
			<td>for staining of ABC of rat corneal endothelium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">goat anti-rabbit IgG (H+L) secondary antibody</td>
			<td>ThermoFisher Scientific</td>
			<td>A-11008</td>
			<td>for staining of snail and slug of bovine CECs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">antibody diluent</td>
			<td>Genemed Biotechnologies</td>
			<td>10-0001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4&#39;,6-diamidino-2-phenylindole</td>
			<td>ThermoFisher Scientific</td>
			<td>D1306</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mounting medium</td>
			<td>Vector Laboratories</td>
			<td>H-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">laser scanning confocal microscope</td>
			<td>ZEISS</td>
			<td>LSM510</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">xylazine&#160;</td>
			<td>Bayer</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">tiletamine plus zolazepam</td>
			<td>Virbac</td>
			<td>N/A</td>
			<td>veterinary drug</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">proparacaine hydrochloride ophthalmic solution</td>
			<td>Alcon</td>
			<td>N/A</td>
			<td>veterinary drug</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.1% atropine</td>
			<td>Wu-Fu Laboratories Co., Ltd</td>
			<td>N/A</td>
			<td>clinical drug&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.3% gentamicin sulfate</td>
			<td>Sinphar Group</td>
			<td>N/A</td>
			<td>clinical drug&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">basic fibroblast growth factor</td>
			<td>ThermoFisher Scientific</td>
			<td>PHG0024</td>
			<td>clinical drug&#160;</td>
		</tr>
	</tbody>
</table>

in vitro and in vivo models to study corneal endothelial-mesenchymal transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema and diminished visual acuity. However, human CECs are prone to compromised proliferative potential. Furthermore, stimulation of cell growth is often complicated by gradual endothelial-mesenchymal transition (EnMT). Therefore, understanding the mechanism of EnMT is necessary for facilitating the regeneration of CECs with competent function. In this study, we prepared a primary culture of bovine CECs by peeling the CECs with Descemet's membrane from the corneal button and demonstrated that bovine CECs exhibited the EnMT process, including phenotypic change, nuclear translocation of &#946;-catenin, and EMT regulators snail and slug, in the in vitro culture. Furthermore, we used a rat corneal endothelium cryoinjury model to demonstrate the EnMT process in vivo. Collectively, the in vitro primary culture of bovine CECs and in vivo rat corneal endothelium cryoinjury models offers useful platforms for investigating the mechanism of EnMT.

After the isolation of bovine CECs, the cells were cultured in vitro. Figure 1 presents the phase contrast images of the bovine CECs. The hexagonal shape of the cells at confluence indicated that the cells were not contaminated by corneal stromal fibroblast during cell isolation. Figure 2 depicts the immunostaining that was performed using antibodies against ABC, snail, and slug at an indicated time point. Apart from phenotypic changes in the in vitro culture, a corresponding nuclear translocation of ABC and EMT regulators was observed. Figure 3 illustrates the effect of marimastat, a broad-spectrum MMP inhibitor, on the EnMT process of the in vitro cultured bovine CECs. Figure 4 comprises the external eye photographs of rats after cryoinjury followed by intracameral injection. Figure 5 shows the immunostaining of the rat corneal button that was performed using antibodies against ABC after cryoinjury followed by intracameral injection. The nuclear translocation of ABC was observed in the PBS group and was significantly increased in the bFGF group, indicating activation of the Wnt/&#946;-catenin signaling and EnMT process. After intracameral injection of bFGF followed by marimastat injection, the nuclear staining of ABC was diminished, suggesting the EnMT-inhibiting effect of marimastat.
<img alt="Figure 1" src="/files/ftp_upload/54329/54329fig1.jpg" /> 
Figure 1: Phase contrast images of in vitro cultured bovine CECs. After being seeded on the culture plate, the bovine CECs initially appeared fibroblast-like on days 3 and 6. They became more hexagonal upon reaching complete confluence on day 9. Scale bar = 50 &#181;m. Representative images of 3 replicates. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54329/54329fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/54329/54329fig2.jpg" /> 
Figure 2: Immunostaining of in vitro cultured bovine CECs. During the in vitro culture of the bovine CECs, the nuclear translocation of ABC, snail, and slug was detected through day 14. ABC: active &#946;-catenin. Scale bar = 100 &#181;m. Representative images of 3 replicates. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54329/54329fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/54329/54329fig3.jpg" /> 
Figure 3: Immunostaining of in vitro cultured bovine CECs with or without marimastat at different cell confluence levels. Immunostaining demonstrated that ABC, snail, and slug were evident in the nucleus of the bovine CECs with or without 10 &#181;M of marimastat on day 3. However, marimastat significantly reduced the nuclear staining of ABC, snail, and slug on day 9 when the bovine CECs became fully confluent. Scale bar = 100 &#181;m. Representative images of 3 replicates. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54329/54329fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/54329/54329fig4.jpg" /> 
Figure 4: External eye photographs of rats at indicated time points after cryoinjury. Following cryoinjury for 3 consecutive days, rats were subjected to intracameral injection of 0.02 ml of PBS or 50 ng/ml bFGF on day 3. On day 6, 0.02 ml of 10 &#181;M marimastat was injected intracamerally in the bFGF/Mari group, whereas PBS was injected in the other 2 groups (n = 9 in each group). External eye photographs revealed reduced corneal edema after bFGF injection, whereas marimastat further reduced corneal edema compared with bFGF alone. n = 9 in each group. Scale bar = 1 mm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54329/54329fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" src="/files/ftp_upload/54329/54329fig5.jpg" /> 
Figure 5: Immunostaining of rat corneal buttons. Immunostaining of the rat corneal buttons that were harvested on day 9 revealed little nuclear staining of ABC in the PBS group. In the bFGF group, there was extensive nuclear staining of ABC, which was significantly reduced in the bFGF/Mari group. Scale bar = 100 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54329/54329fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition at JoVE.com

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

A primary culture of bovine corneal endothelial cells was used to investigate the mechanism of corneal endothelial-mesenchymal transition. Furthermore, a rat corneal endothelium cryoinjury model was used to demonstrate corneal endothelial-mesenchymal transition in vivo.

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema ...

in-vitro-vivo-models-to-study-corneal-endothelial-mesenchymal

Nanyang Technological University

Research

JoVE Journal

Developmental Biology

7.9K Views.  Far Eastern Memorial Hospital. A primary culture of bovine corneal endothelial cells was used to investigate the mechanism of corneal endothelial-mesenchymal transition. Furthermore, a rat corneal endothelium cryoinjury model was used to demonstrate corneal endothelial-mesenchymal transition in vivo.

Video: In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

Characterizing thymic settling progenitors is important to understand the pre-thymic stages of T cell development, essential to devise strategies for T cell replacement in lymphopenic patients. We studied thymic settling progenitors from murine embryonic day 13 and 18 thymi by two complementary in vitro and in vivo techniques, both based on the &#8220;hanging drop&#8221; method. This method allowed colonizing irradiated fetal thymic lobes with E13 and/or E18 thymic progenitors distinguished by CD45 allotypic markers and thus following their progeny. Colonization with mixed populations allows analyzing cell autonomous differences in biologic properties of the progenitors while colonization with either population removes possible competitive selective pressures. The colonized thymic lobes can also be grafted in immunodeficient male recipient mice allowing the analysis of the mature T cell progeny in vivo, such as population dynamics of the peripheral immune system and colonization of different tissues and organs. Fetal thymic organ cultures revealed that E13 progenitors developed rapidly into all mature CD3+ cells and gave rise to the canonical &#947;&#948; T cell subset, known as dendritic epithelial T cells. In comparison, E18 progenitors have a delayed differentiation and were unable to generate dendritic epithelial T cells. The monitoring of peripheral blood of thymus-grafted CD3-/- mice further showed that E18 thymic settling progenitors generate, with time, larger numbers of mature T cells than their E13 counterparts, a feature that could not be appreciated in the short term fetal thymic organ cultures.

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

This article describes in vivo and in vitro methodology to characterize the thymic settling progenitors by the analysis of the kinetics of generation, phenotype and numbers of their T cell progeny.

Characterizing thymic settling progenitors is important to understand the pre-thymic stages of T cell development, essential to devise strategies for T ...

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, cells from the roof of the blastocoel are pluripotent. These cells can be isolated, and programmed to generate various tissues through manipulation of genes expression or induction by morphogens. In this manuscript protocols are described for the use of Xenopus laevis blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development. These protocols allow the investigation of fate acquisition, cell migration behaviors, and cell autonomous and non-autonomous properties. The blastocoel roof explants can be cultured in a serum-free defined medium and grafted into host embryos. This transplantation into an embryo allows the investigation of the long-term lineage commitment, the inductive properties, and the behavior of transplanted cells in vivo. These assays can be exploited to investigate molecular mechanisms, cellular processes and gene regulatory networks underlying neural development. In the context of regenerative medicine, these assays provide a means to generate neural-derived cell types in vitro that could be used in drug screening.

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

In Xenopus embryos, cells from the roof of the blastocoel are pluripotent and can be programmed to generate various tissues. Here, we describe protocols to use amphibian blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development.

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, ...

Development of an In Vitro Assay to Evaluate Contractile Function of Mesenchymal Cells that Underwent Epithelial-Mesenchymal Transition

Fibrosis is often involved in the pathogenesis of various chronic progressive diseases such as interstitial pulmonary disease. Pathological hallmark is the formation of fibroblastic foci, which is associated with the disease severity. Mesenchymal cells consisting of the fibroblastic foci are proposed to be derived from several cell sources, including originally resident intrapulmonary fibroblasts and circulating fibrocytes from bone marrow. Recently, mesenchymal cells that underwent epithelial-mesenchymal transition (EMT) have been also supposed to contribute to the pathogenesis of fibrosis. In addition, EMT can be induced by transforming growth factor &#946;, and EMT can be enhanced by pro-inflammatory cytokines like tumor necrosis factor &#945;. The gel contraction assay is an ideal in vitro model for the evaluation of contractility, which is one of the characteristic functions of fibroblasts and contributes to wound repair and fibrosis. Here, the development of a gel contraction assay is demonstrated for evaluating contractile ability of mesenchymal cells that underwent EMT.

Development of an In Vitro Assay to Evaluate Contractile Function of Mesenchymal Cells that Underwent Epithelial-Mesenchymal Transition

Here, we describe the development and application of a gel contraction assay for evaluating contractile function in mesenchymal cells that underwent epithelial-mesenchymal transition.

Fibrosis is often involved in the pathogenesis of various chronic progressive diseases such as interstitial pulmonary disease. Pathological hallmark is ...

Live Imaging of Mouse Secondary Palate Fusion

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to cleft secondary palate, a common congenital anomaly in humans. Secondary palate fusion has been extensively studied leading to several proposed cellular mechanisms that may mediate this process. However, these studies have been mostly performed on fixed embryonic tissues at progressive timepoints during development or in fixed explant cultures analyzed at static timepoints. Static analysis is limited for the analysis of dynamic morphogenetic processes such a palate fusion and what types of dynamic cellular behaviors mediate palatal fusion is incompletely understood. Here we describe a protocol for live imaging of ex vivo secondary palate fusion in mouse embryos. To examine cellular behaviors of palate fusion, epithelial-specific Keratin14-cre was used to label palate epithelial cells in ROSA26-mTmGflox reporter embryos. To visualize filamentous actin, Lifeact-mRFPruby reporter mice were used. Live imaging of secondary palate fusion was performed by dissecting recently-adhered secondary palatal shelves of embryonic day (E) 14.5 stage embryos and culturing in agarose-containing media on a glass bottom dish to enable imaging with an inverted confocal microscope. Using this method, we have detected a variety of novel cellular behaviors during secondary palate fusion. An appreciation of how distinct cell behaviors are coordinated in space and time greatly contributes to our understanding of this dynamic morphogenetic process. This protocol can be applied to mutant mouse lines, or cultures treated with pharmacological inhibitors to further advance understanding of how secondary palate fusion is controlled.

Here, we present a protocol for live imaging of mouse secondary palate fusion using confocal microscopy. This protocol can be used in combination with a variety of fluorescent reporter mouse lines, and with pathway inhibitors for mechanistic insight. This protocol can be adapted for live imaging in other developmental systems.

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to ...

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain and protect cellular identities. The conversion of germ cells into specific neurons in the nematode Caenorhabditis elegans (C. elegans) is a powerful tool for performing genetic screens in order to dissect regulatory pathways that safeguard established cell identities. Reprogramming of germ cells to a specific type of neurons termed ASE requires transgenic animals that allow broad over-expression of the Zn-finger transcription factor (TF) CHE-1. Endogenous CHE-1 is expressed exclusively in two head neurons and is required to specify the glutamatergic ASE neurons fate, which can easily be visualized by the gcy-5prom::gfp reporter. A trans gene containing the heat-shock promoter-driven che-1 gene expression construct allows broad mis-expression of CHE-1 in the entire animal upon heat-shock treatment. The combination of RNAi against the chromatin-regulating factor LIN-53 and heat-shock-induced che-1 over-expression leads to reprogramming of germ cell into ASE neuron-like cells. We describe here the specific RNAi procedure and appropriate conditions for heat-shock treatment of transgenic animals in order to successfully induce germ cell to neuron conversion.

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

This protocol describes how to study cellular processes during cell fate conversion in Caenorhabditis elegans in vivo. Using transgenic animals, allowing heat-shock promoter-driven overexpression of the neuron fate-inducing transcription factor CHE-1 and RNAi-mediated depletion of the chromatin-regulating factor LIN-53 germ cell to neuron reprogramming can be observed in vivo.

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain ...

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is the formation of the transient organizers, the node and notochordal plate, from cells that have passed through the primitive streak. The proper formation of these signaling centers is essential for the development of the body plan and techniques to visualize them are of high interest to mouse developmental biologists. The node and notochordal plate lie on the ventral surface of gastrulating mouse embryos around embryonic day (E) 7.5 of development. The node is a cup-shaped structure whose cells possess a single slender cilium each. The proper subcellular localization and rotation of the cilia in the node pit determines left-right asymmetry. The notochordal plate cells also possess single cilia albeit shorter than those of the node cells. The notochordal plate forms the notochord which acts as an important signaling organizer for somitogenesis and neural patterning. Because the cells of the node and notochordal plate are transiently present on the surface and possess cilia, they can be visualized using scanning electron microscopy (SEM). Among other techniques used to visualize these structures at the cellular level is whole mount immunofluorescence (WMIF) using the antibodies against the proteins that are highly expressed in the node and notochordal plate. In this report, we describe our optimized protocols to perform SEM and WMIF of the node and notochordal plate in developing mouse embryos to help in the assessment of tissue shape and cellular organization in wild-type and gastrulation mutant embryos.

The node and notochordal plate are transient signaling organizers in developing mouse embryos that can be visualized using several techniques. Here, we describe in detail how to perform two of the techniques to study their structure and morphogenesis: 1) scanning electron microscopy (SEM); and 2) whole mount immunofluorescence (WMIF).

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is ...

Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows within roughly two weeks after injury. Furthermore, zebrafish are able to heal bone rapidly after trepanation of the skull, and repair fractures that can be easily introduced into zebrafish bony fin rays. These injury assays represent feasible experimental paradigms to test the effect of administered drugs on rapidly forming bone. Here, we describe the use of these 3 injury models and their combined use with systemic glucocorticoid treatment, which exerts bone inhibitory and immunosuppressive effects. We provide a workflow on how to prepare for immunosuppressive treatment in adult zebrafish, illustrate how to perform fin amputation, trepanation of calvarial bones, and fin fractures, and describe how the use of glucocorticoids affects both bone forming osteoblasts and cells of the monocyte/macrophage lineage as part of innate immunity in bone tissue.

Here, we describe 3 adult zebrafish injury models and their combined use with immunosuppressive drug treatment. We provide guidance on imaging of regenerating tissues and on detecting bone mineralization therein.

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows ...

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart disease. When using prosthetic materials however, these grafts are susceptible to bacterial infections and various host responses.
Identification of bacterial and host factors that play a vital role in endovascular adherence of microorganisms is of importance to better understand the pathophysiology of the onset of infections such as infective endocarditis (IE) and to develop preventive strategies. Therefore, the development of competent models to investigate bacterial adhesion under physiological shear conditions is necessary. Here, we describe the use of a newly designed in vitro perfusion chamber based on parallel plates that allows the study of bacterial adherence to different components of graft tissues such as exposed extracellular matrix, endothelial cells and inert areas. This method combined with colony-forming unit (CFU) counting is adequate to evaluate the propensity of graft materials towards bacterial adhesion under flow. Further on, the flow chamber system might be used to investigate the role of blood components in bacterial adhesion under shear conditions. We demonstrated that the source of tissue, their surface morphology and bacterial species specificity are not the major determining factors in bacterial adherence to graft tissues by using our in-house designed in vitro perfusion model.

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

We describe an in-house designed in vitro flow chamber model, which allows the investigation of bacterial adherence to graft tissues.

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart ...

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by Sertoli cell junctions at the blood-testis barrier (BTB), which is the tightest tissue barrier in the mammalian body and segregates the seminiferous epithelium into two compartments, a basal and an adluminal. The BTB creates a unique microenvironment for germ cells in meiosis I/II and for the development of postmeiotic spermatids into spermatozoa via spermiogenesis. Here, we describe a reliable assay to monitor BTB integrity of mouse testis in vivo. An intact BTB blocks the diffusion of FITC-conjugated inulin from the basal to the apical compartment of the seminiferous tubules. This technique is suitable for studying gene candidates, viruses, or environmental toxicants that may affect BTB function or integrity, with an easy procedure and a minimal requirement of surgical skills compared to alternative methods.

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Here, we present a protocol to assess the blood-testis barrier integrity by injecting inulin-FITC into testes. This is an efficient in vivo method to study blood-testis barrier integrity that can be compromised by genetic and environmental elements.

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by ...

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Summary

Explore More Videos

Chapters in this video

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

Development of an In Vitro Assay to Evaluate Contractile Function of Mesenchymal Cells that Underwent Epithelial-Mesenchymal Transition

Live Imaging of Mouse Secondary Palate Fusion

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity