Corneal endothelial dysfunction accompanied by visual disturbance is a primary indication for corneal transplantation. We previously reported that the adhesion of corneal endothelial cells (CECs) to a substrate was enhanced by the selective ROCK inhibitor Y-27632. It is hypothesized that the inhibition of ROCK signaling may manipulate cell adhesion properties, thus enabling the transplantation of cultivated CECs as a form of regenerative medicine. In the present study, using a rabbit corneal endothelial dysfunction model, the transplantation of CECs in combination with Y-27632 successfully achieved the recovery of corneal transparency. Complications related to cell injection therapy, such as the abnormal deposition of the injected cells as well as the elevation of intraocular pressure, were not observed. Reconstructed corneal endothelium with Y-27632 exhibited a monolayer hexagonal cell shape with a normal expression of function-related markers, such as ZO-1, and Na+/K+-ATPase, whereas reconstruction without Y-27632 exhibited a stratified fibroblastic phenotype without the expression of markers. Moreover, transplantation of CECs in primates in the presence of the ROCK inhibitor also achieved the recovery of long-term corneal transparency with a monolayer hexagonal cell phenotype at a high cell density. Taken together, these results suggest that the selective ROCK inhibitor Y-27632 enables cultivated CEC-based therapy and that the modulation of Rho-ROCK signaling activity serves to enhance cell engraftment for cell-based regenerative medicine. Corneal endothelial dysfunction accompanied by visual disturbance is a primary indication for corneal transplantation. We previously reported that the adhesion of corneal endothelial cells (CECs) to a substrate was enhanced by the selective ROCK inhibitor Y-27632. It is hypothesized that the inhibition of ROCK signaling may manipulate cell adhesion properties, thus enabling the transplantation of cultivated CECs as a form of regenerative medicine. In the present study, using a rabbit corneal endothelial dysfunction model, the transplantation of CECs in combination with Y-27632 successfully achieved the recovery of corneal transparency. Complications related to cell injection therapy, such as the abnormal deposition of the injected cells as well as the elevation of intraocular pressure, were not observed. Reconstructed corneal endothelium with Y-27632 exhibited a monolayer hexagonal cell shape with a normal expression of function-related markers, such as ZO-1, and Na+/K+-ATPase, whereas reconstruction without Y-27632 exhibited a stratified fibroblastic phenotype without the expression of markers. Moreover, transplantation of CECs in primates in the presence of the ROCK inhibitor also achieved the recovery of long-term corneal transparency with a monolayer hexagonal cell phenotype at a high cell density. Taken together, these results suggest that the selective ROCK inhibitor Y-27632 enables cultivated CEC-based therapy and that the modulation of Rho-ROCK signaling activity serves to enhance cell engraftment for cell-based regenerative medicine. Corneal endothelial dysfunction is a major cause of severe visual impairment, because corneal endothelial cells maintain corneal transparency through their barrier and Na+-K+ transport system. Highly effective surgical techniques to replace corneal endothelium (eg, Descemet's stripping endothelial keratoplasty) have been developed,1Gorovoy M.S. Descemet-stripping automated endothelial keratoplasty.Cornea. 2006; 25: 886-889Crossref PubMed Scopus (681) Google Scholar, 2Price Jr., F.W. Price M.O. Descemet's stripping with endothelial keratoplasty in 50 eyes: a refractive neutral corneal transplant.J Refract Surg. 2005; 21: 339-345PubMed Google Scholar aimed at replacing penetrating keratoplasty for overcoming pathological dysfunctions of corneal endothelial tissue. Several research groups, including ours, have devoted an intensive amount of effort in an attempt to establish new treatment methods suitable for a practical clinical intervention to repair corneal endothelial dysfunctions.3Koizumi N. Sakamoto Y. Okumura N. Okahara N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial cell sheet transplantation in a primate model.Invest Ophthalmol Vis Sci. 2007; 48: 4519-4526Crossref PubMed Scopus (174) Google Scholar, 4Koizumi N. Sakamoto Y. Okumura N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial transplantation in a primate: possible future clinical application in corneal endothelial regenerative medicine.Cornea. 2008; 27: S48-S55Crossref PubMed Scopus (70) Google Scholar, 5Mimura T. Yamagami S. Yokoo S. Usui T. Tanaka K. Hattori S. Irie S. Miyata K. Araie M. Amano S. Cultured human corneal endothelial cell transplantation with a collagen sheet in a rabbit model.Invest Ophthalmol Vis Sci. 2004; 45: 2992-2997Crossref PubMed Scopus (225) Google Scholar, 6Ishino Y. Sano Y. Nakamura T. Connon C.J. Rigby H. Fullwood N.J. Kinoshita S. Amniotic membrane as a carrier for cultivated human corneal endothelial cell transplantation.Invest Ophthalmol Vis Sci. 2004; 45: 800-806Crossref PubMed Scopus (271) Google Scholar Because corneal endothelium is composed of a monolayer and is technically difficult to transplant into the anterior chamber as a structurally flexible cell sheet, those research teams cultured corneal endothelial cells (CECs) on substrates such as collagen sheets and amniotic membrane. The injection of cultivated cells has been reported for the treatment of a number of organs associated with degenerative diseases such as the heart,7Schachinger V. Erbs S. Elsasser A. Haberbosch W. Hambrecht R. Holschermann H. Yu J. Corti R. Mathey D.G. Hamm C.W. Suselbeck T. Assmus B. Tonn T. Dimmeler S. Zeiher A.M. Intracoronary bone marrow-derived progenitor cells in acute myocardial infarction.N Engl J Med. 2006; 355: 1210-1221Crossref PubMed Scopus (1682) Google Scholar vessels,8Tateishi-Yuyama E. Matsubara H. Murohara T. Ikeda U. Shintani S. Masaki H. Amano K. Kishimoto Y. Yoshimoto K. Akashi H. Shimada K. Iwasaka T. Imaizumi T. Therapeutic angiogenesis for patients with limb ischaemia by autologous transplantation of bone-marrow cells: a pilot study and a randomised controlled trial.Lancet. 2002; 360: 427-435Abstract Full Text Full Text PDF PubMed Scopus (1562) Google Scholar pancreas,9Shapiro A.M. Lakey J.R. Ryan E.A. Korbutt G.S. Toth E. Warnock G.L. Kneteman N.M. Rajotte R.V. Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen.N Engl J Med. 2000; 343: 230-238Crossref PubMed Scopus (4355) Google Scholar and cartilage.10Yanaga H. Koga M. Imai K. Yanaga K. Clinical application of biotechnically cultured autologous chondrocytes as novel graft material for nasal augmentation.Aesthetic Plast Surg. 2004; 28: 212-221Crossref PubMed Scopus (37) Google Scholar In regard to corneal endothelium, it is known that injected cultured CECs appear to be washed off by aqueous humor flow, thus resulting in the poor adhesion of those injected cells onto the corneal tissue. To develop an effective method for delivering cultivated CECs to the posterior cornea, the magnetic attachment of iron powder or superparamagnetic microspheres incorporated in the cultivated CECs has been attempted. This method has been shown to work in a rabbit transplantation model11Mimura T. Shimomura N. Usui T. Noda Y. Kaji Y. Yamgami S. Amano S. Miyata K. Araie M. Magnetic attraction of iron-endocytosed corneal endothelial cells to Descemet's membrane.Exp Eye Res. 2003; 76: 745-751Crossref PubMed Scopus (80) Google Scholar, 12Mimura T. Yamagami S. Usui T. Ishii Y. Ono K. Yokoo S. Funatsu H. Araie M. Amano S. Long-term outcome of iron-endocytosing cultured corneal endothelial cell transplantation with magnetic attraction.Exp Eye Res. 2005; 80: 149-157Crossref PubMed Scopus (61) Google Scholar and in an organ culture model of the human eye13Patel S.V. Bachman L.A. Hann C.R. Bahler C.K. Fautsch M.P. Human corneal endothelial cell transplantation in a human ex vivo model.Invest Ophthalmol Vis Sci. 2009; 50: 2123-2131Crossref PubMed Scopus (66) Google Scholar; however, these methods have yet to be applied in the clinical setting. Cell adhesion is known to be mediated through transmembrane adhesion molecules linked to the intracellular cytoskeleton. In addition to the structural function, these adhesion molecules reportedly serve as a platform for the interplay with the surrounding environments.14Sastry S.K. Burridge K. Focal adhesions: a nexus for intracellular signaling and cytoskeletal dynamics.Exp Cell Res. 2000; 261: 25-36Crossref PubMed Scopus (428) Google Scholar, 15Critchley D.R. Focal adhesions—the cytoskeletal connection.Curr Opin Cell Biol. 2000; 12: 133-139Crossref PubMed Scopus (494) Google Scholar Rho GTPase proteins are key modulators of cytoskeletal dynamics that occur after cell adhesion.16Hall A. Rho GTPases and the actin cytoskeleton.Science. 1998; 279: 509-514Crossref PubMed Scopus (5216) Google Scholar, 17Worthylake R.A. Lemoine S. Watson J.M. Burridge K. RhoA is required for monocyte tail retraction during transendothelial migration.J Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (410) Google Scholar, 18Worthylake R.A. Burridge K. RhoA and ROCK promote migration by limiting membrane protrusions.J Biol Chem. 2003; 278: 13578-13584Crossref PubMed Scopus (246) Google Scholar It has been reported that Rho GTPases induce a specific type of actin cytoskeleton through mediating downstream effectors mDia and Rho-associated kinase (ROCK), and that they regulate a variety of cellular functions.19Narumiya S. Tanji M. Ishizaki T. Rho signaling, ROCK and mDia1, in transformation, metastasis and invasion.Cancer Metastasis Rev. 2009; 28: 65-76Crossref PubMed Scopus (416) Google Scholar Cell adhesion, motility, and cell morphogenesis are thought to be determined by the balance between mDia and ROCK activities.19Narumiya S. Tanji M. Ishizaki T. Rho signaling, ROCK and mDia1, in transformation, metastasis and invasion.Cancer Metastasis Rev. 2009; 28: 65-76Crossref PubMed Scopus (416) Google Scholar We recently reported that the adhesion of CECs to a substrate was enhanced by inhibiting Rho/ROCK signaling.20Okumura N. Ueno M. Koizumi N. Sakamoto Y. Hirata K. Hamuro J. Kinoshita S. Enhancement on primate corneal endothelial cell survival in vitro by a ROCK inhibitor.Invest Ophthalmol Vis Sci. 2009; 50: 3680-3687Crossref PubMed Scopus (203) Google Scholar This finding coincides well with those of other studies that demonstrated that Rho-ROCK signaling negatively regulates the integrin-mediated adhesion of monocytes, and that the inhibition of ROCK by a selective ROCK inhibitor upregulates adhesion.17Worthylake R.A. Lemoine S. Watson J.M. Burridge K. RhoA is required for monocyte tail retraction during transendothelial migration.J Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (410) Google Scholar, 18Worthylake R.A. Burridge K. RhoA and ROCK promote migration by limiting membrane protrusions.J Biol Chem. 2003; 278: 13578-13584Crossref PubMed Scopus (246) Google Scholar These features have led us to hypothesize that the inhibition of ROCK signaling may provide a way to manipulate the cell adhesion property of cultivated corneal endothelium to the extent practical for regenerative medicine. In this current study, in two animal models (rabbit and primate) of corneal endothelial dysfunctions, the transplantation of cultivated CECs in combination with ROCK inhibitor Y-27632 successfully achieved the recovery of corneal transparency. Inhibition of the ROCK signaling manipulated the adhesion property of the cultivated CECs. Moreover, the injected CECs functioned sufficiently well to reconstruct the corneal endothelium with an appropriate cell density, morphology, and expression of function-related markers. This novel treatment strategy may provide a new therapeutic modality for corneal-endothelium–associated pathological dysfunctions. Rabbit eyes were purchased from Funakoshi Corporation (Tokyo, Japan). Alizarin red S stain and selective ROCK inhibitor Y-27632 were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Dulbecco's modified Eagle's medium supplemented with penicillin, streptomycin, and basic fibroblast growth factor (bFGF), Vybrant DiI cell-labeling solution, Alexa Fluor 594-conjugated phalloidin, Alexa Fluor 488-conjugated phalloidin, Alexa Fluor 488-conjugated goat anti-mouse IgG, anti-vinculin antibody, ROCK1 Stealth RNAi (HSS109291, HSS109292, and HSS109293), ROCK2 Stealth RNAi (HSS114106, HSS114107, and HSS114108), Stealth RNAi negative control medium GC #2, and Lipofectamine RNAiMAX were purchased from Life Technologies (Carlsbad, CA). Dispase II was purchased from Roche Applied Science (Penzberg, Germany). FNC Coating Mix was purchased from Athena Environmental Sciences, Inc. (Baltimore, MD). Ki-67 monoclonal antibody, propidium iodide (PI), and Cytochalasin D were purchased from Sigma-Aldrich Co. (St. Louis, MO). ZO-1 polyclonal antibody was purchased from Zymed Laboratories (South San Francisco, CA). α–Smooth muscle actin (α-SMA) monoclonal antibody was purchased from Thermo Fisher Scientific (Kalamazoo, MI). Na+/K+-ATPase monoclonal antibody was purchased from Upstate Biotech (Lake Placid, NY). DAPI was purchased from Vector Laboratories (Burlingame, CA). CellTiter-Glo Luminescent Cell Viability Assay was purchased from Promega (Madison, WI). In all experiments, animals were housed and treated in accordance with The Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. The rabbit experiments were performed at Doshisha University (Kyoto, Japan) according to the protocol approved by that university's Animal Care and Use Committee (approval no. 0831). The monkey experiments were performed at the Research Center for Animal Life Science at Shiga University of Medical Science (Otsu, Japan) according to the protocol approved by that university's Animal Care and Use Committee (approval no. 2008-10-5). Ten rabbit eyes were used for the rabbit CECs (RCECs) culture. Eight corneas from four cynomolgus monkeys (3 to 5 years of age; estimated equivalent human age: 5 to 20 years) housed at the Nissei Bilis Co. (Otsu, Japan) and the Keari Co. (Wakayama, Japan), respectively, were used for the monkey CECs (MCECs) culture. The RCECs and MCECs were cultivated as described previously.3Koizumi N. Sakamoto Y. Okumura N. Okahara N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial cell sheet transplantation in a primate model.Invest Ophthalmol Vis Sci. 2007; 48: 4519-4526Crossref PubMed Scopus (174) Google Scholar, 20Okumura N. Ueno M. Koizumi N. Sakamoto Y. Hirata K. Hamuro J. Kinoshita S. Enhancement on primate corneal endothelial cell survival in vitro by a ROCK inhibitor.Invest Ophthalmol Vis Sci. 2009; 50: 3680-3687Crossref PubMed Scopus (203) Google Scholar Briefly, Descemet's membrane with CECs was stripped and incubated in 0.6 U/mL of Dispase II to release the CECs. After a 60-minute incubation at 37°C, the CECs obtained from individual corneas were resuspended in culture medium and plated in one well of a six-well plate coated with cell attachment reagent (FNC Coating Mix). All primary cell cultures and serial passages of CECs were performed in growth medium composed of Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum, 50 U/mL penicillin, 50 μg/mL streptomycin, and 2 ng/mL bFGF. CECs were cultured in a humidified atmosphere at 37°C in 5% CO2. The culture medium was changed every 2 days. When cells reached confluency in 10 to 14 days, they were rinsed in Ca2+ and Mg2+-free Dulbecco's phosphate-buffered saline (PBS), trypsinized with 0.05% Trypsin-EDTA (Life Technologies, Carlsbad, CA) for 5 minutes at 37°C, and passaged at ratios of 1:2 to 1:4. Cultivated CECs derived from both rabbit and monkey corneas at passages 3 through 5 were used for all experiments. To confirm the cultivation of the CECs, the morphology and density of the cultivated cells were compared with normal in vivo rabbit CECs examined using a noncontact specular microscope (Noncon Robo, SP-8800; Konan Medical, Nishinomiya, Japan) and stained with Alizarin red. In some experiments, to investigate the fate of the injected CECs in vivo, the CECs were labeled with fluorescein by use of the Vybrant DiI cell-labeling solution according to the manufacturer's protocol. To create rabbit corneal endothelial pathological dysfunction models, the lenses of both eyes of 12 Japanese white rabbits were removed under general anesthesia by use of the Alcon Series 20000 Legacy Surgical System (Alcon, Fort Worth, TX) to deepen the anterior chamber. Next, the corneal endothelium of each of those eyes was mechanically scraped with a 20-gauge silicone needle (Soft Tapered Needle; Inami, Tokyo, Japan) from Descemet's membrane as described previously.3Koizumi N. Sakamoto Y. Okumura N. Okahara N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial cell sheet transplantation in a primate model.Invest Ophthalmol Vis Sci. 2007; 48: 4519-4526Crossref PubMed Scopus (174) Google Scholar, 4Koizumi N. Sakamoto Y. Okumura N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial transplantation in a primate: possible future clinical application in corneal endothelial regenerative medicine.Cornea. 2008; 27: S48-S55Crossref PubMed Scopus (70) Google Scholar The scraped area was then confirmed by 0.04% trypan blue staining during surgery. In the preliminary experiments, we confirmed that Descemet's membrane was intact, the mechanically scraped area had no cells on Descemet's membrane, and that residual CECs were detected in only a 500- to 600-μm area at the edge of Descemet's membrane. To evaluate the injection of cultivated CECs with ROCK inhibitor, RCECs at a density of 2.0 × 105 cells were suspended in 200 μl DMEM supplemented with 100 μmol/L of Y-27632 and then injected into the anterior chamber of the eyes of the above-described corneal endothelial dysfunction rabbit model. RCECs with Y-27632 were injected into the right eyes of six rabbits, and RCECs without Y-27632 were injected into the right eyes of the other six rabbits. After the injection, the eyes of those 12 rabbits were kept in the face-down position for 3 hours under general anesthesia. The left eyes of those 12 rabbits in which the corneal endothelium was removed mechanically were used as a control. One rabbit injected with RCECs with Y-27632 and one rabbit injected with RCECs without Y-27632 were euthanized 3 hours after injection for histological examination. The corneal appearance of the other 10 rabbits was examined daily by use of a slit-lamp microscope for the first week, and then once every 2 days for the following 2 weeks. Those 10 rabbits were then euthanized for histological examination. Corneal thickness was determined by use of an ultrasound pachymeter (SP-2000; Tomey, Nagoya, Japan), and the mean of 10 measured values was then calculated (up to a maximum thickness of 1200 μm, the instrument's maximum reading). Intraocular pressure was measured by use of a pneumatonometer (30 Classic; Reichert, NY). Sections (6-μm) of corneal specimens obtained from the 10 rabbits euthanized 2 weeks after injection were embedded in OCT compound and then fixed in 4% formaldehyde. Differential interference contrast (DIC) images and fluorescence images of DiI-labeled cells were obtained by use of a fluorescence microscope (TCS SP2 AOBS; Leica Microsystems, Welzlar, Germany). For flat-mount examinations, whole corneal specimens were fixed in 4% formaldehyde and incubated in 1% bovine serum albumin (BSA) to block any nonspecific binding. To evaluate the effect of Y-27632 on the adhesion property of the cells, corneas obtained from the 2 rabbits euthanized 3 hours after injection were examined by actin staining performed with a 1:400 dilution of Alexa Fluor 488–conjugated phalloidin. Actin staining was used to evaluate the cellular morphology. The cell nuclei were then stained with PI. To investigate the phenotype of the reconstructed corneal endothelium obtained from the 10 rabbits euthanized 2 weeks after injection, immunohistochemical analyses of actin, α-SMA, ZO-1, Na+/K+-ATPase, DiI, and Ki-67 were performed. α-SMA was used to evaluate the fibroblastic change. ZO-1, a tight-junction–associated protein, and Na+/K+-ATPase, the protein associated with pump function, were used for function related markers of CECs. The α-SMA, ZO-1, and Na+/K+-ATPase staining were performed with a 1:200 dilution of α-SMA monoclonal antibody, ZO-1 polyclonal antibody, and Na+/K+-ATPase monoclonal antibody, respectively. Ki-67 (a cell-proliferation–related maker) staining was performed using a 1:400 dilution of anti-mouse Ki-67 antibody. For the secondary antibody, a 1:2000 dilution of Alexa Fluor 488–conjugated goat anti-mouse IgG was used. Cell nuclei were then stained with DAPI, and the slides were inspected by fluorescence microscopy. MCECs were cultured at a density of 2.5 × 104 cells/cm2 on Lab-Tek Chamber Slides (NUNC A/S, Roskilde, Denmark). Actin staining was performed with 1:400-diluted Alexa Fluor, as described above, after 24 hours of seeding, and vinculin staining was performed using 1:200-diluted vinculin after 3 hours of seeding. The number of attached MCECs was evaluated by use of CellTiter-Glo Luminescent Cell Viability Assay performed according to the manufacturer's protocol. The MCECs were seeded with a different concentration of Y-27632 at the density of 1.0 × 103 cells onto 96-well plates, and the number of adhered MCECs at 24 hours after seeding was then measured by use of a Veritas Microplate Luminometer (Promega). In addition to ROCK signaling inhibition, to evaluate the effect of inhibition of actin polymerization on CECs adhesion, MCECs were seeded with a different concentration of cytochalasin D at the density of 1.0 × 103 cells onto 96-well plates, and the number of adhered MCECs at 24 hours after seeding was then measured. Five samples were prepared for each group. To determine the adhesion property of the MCECs onto the basement membrane, the cells were seeded onto rabbit corneas in which the corneal endothelium was mechanically denuded and the basement membranes were exposed. The cells were seeded at the density of 2.5 × 104 cells/cm2 suspended in culture medium supplemented with or without 10 μmol/L Y-27632. Actin staining was performed at 3 hours after seeding in the same manner as with the Alexa Fluor 488–conjugated phalloidin staining described above. Cell nuclei were then stained with PI. MCECs at the density of 2.0 × 105 cells were also seeded, with or without Y-27632, onto Descemet's membrane of four rabbits from each group, and the membrane was then mechanically peeled off at 3 hours after seeding. The adhered MCECs were recovered by trypsin digestion, and the cell numbers were then counted. MCECs seeded at the density of 2.5 × 104 cells/cm2 onto a 24-well plate were incubated with RNAi duplex (ROCK1 Stealth RNAi and ROCK2 Stealth RNAi) and Lipofectamine RNAiMAX according to the manufacturer's protocol. Briefly, 1 day before transfection, the culture medium was replaced with fresh medium without antibiotics. RNAi duplex at the final concentration of 10 nmol/L and Lipofectamine RNAiMAX complexes were added to each well. The MCECs were incubated for 12 hours at 37°C in a CO2 incubator. Random RNAi was used as a control. The MCECs were then seeded at the density of 1.0 × 103 cells onto 96-well plates, and the number of attached MCECs was evaluated by use of CellTiter-Glo Luminescent Cell Viability Assay. Knockdown of both ROCK1 and ROCK2, two ROCK isoforms that were identified in the mammalian system,21Liao J.K. Seto M. Noma K. Rho kinase (ROCK) inhibitors.J Cardiovasc Pharmacol. 2007; 50: 17-24Crossref PubMed Scopus (320) Google Scholar was confirmed by quantitative PCR analysis (data not shown). Representative data were from six independent experiments using three kinds of ROCK1 Stealth RNAi and ROCK2 Stealth RNAi, respectively. To create monkey corneal endothelial pathological dysfunction models, the corneal endothelium of the left eyes of four monkeys was mechanically scraped with a 20-gauge silicone needle under general anesthesia, as described above for the rabbit model. Next, a 2.0 × 105 density of cultivated MCECs suspended in 200 μl DMEM supplemented with 100 μmol/L Y-27632 were injected into the anterior chamber of two of the four monkeys. Cultivated MCECs suspended in 200 μl DMEM without Y-27632 were injected into the anterior chamber of the other 2 monkeys. The eyes of all four monkeys were kept in the face-down position for 3 hours under general anesthesia. The MCECs were labeled with DiI before transplantation.3Koizumi N. Sakamoto Y. Okumura N. Okahara N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial cell sheet transplantation in a primate model.Invest Ophthalmol Vis Sci. 2007; 48: 4519-4526Crossref PubMed Scopus (174) Google Scholar, 4Koizumi N. Sakamoto Y. Okumura N. Tsuchiya H. Torii R. Cooper L.J. Ban Y. Tanioka H. Kinoshita S. Cultivated corneal endothelial transplantation in a primate: possible future clinical application in corneal endothelial regenerative medicine.Cornea. 2008; 27: S48-S55Crossref PubMed Scopus (70) Google Scholar The corneal appearance of all four monkeys was examined daily by use of a slit-lamp microscope for the first week, and then once per week for the following 3 months. Two monkeys from each group (the MCEC-injection with Y-27632 group, and the MCEC-injection without Y-27632 group) were euthanized at 14 days after the injection, and the other 2 monkeys were euthanized at 3 months after the injection. For flat-mount examinations, whole corneal specimens were fixed in 4% formaldehyde, incubated in 1% BSA to block nonspecific binding, and then prepared for histological examination. To investigate the phenotype of the reconstructed corneal endothelium, immunohistochemical analyses of actin, ZO-1, and Na+/K+-ATPase were performed in the same manner as that of the above-described rabbit experiments. After the actin immunostaining, the corneal endothelium of the four monkeys was evaluated by KSS-400EB software version 2.71 (Konan Medical, Hyogo, Japan). The statistical significance (P value) in mean values of the two-sample comparison was determined by Student's t-test. Values shown on the graphs represent the mean ± SEM. The third-passaged RCECs exhibited a monolayer of hexagonal shaped cells, similar to in vivo RCECs with a cell density of approximately 2600 cells/mm2 as previously reported5Mimura T. Yamagami S. Yokoo S. Usui T. Tanaka K. Hattori S. Irie S. Miyata K. Araie M. Amano S. Cultured human corneal endothelial cell transplantation with a collagen sheet in a rabbit model.Invest Ophthalmol Vis Sci. 2004; 45: 2992-2997Crossref PubMed Scopus (225) Google Scholar, 6Ishino Y. Sano Y. Nakamura T. Connon C.J. Rigby H. Fullwood N.J. Kinoshita S. Amniotic membrane as a carrier for cultivated human corneal endothelial cell transplantation.Invest Ophthalmol Vis Sci. 2004; 45: 800-806Crossref PubMed Scopus (271) Google Scholar (Figure 1A). Cultivated RCECs injected together with Y-27632 were successful in recovering complete transparency of the corneas with pathological dysfunctions. In contrast, RCECs injected without Y-27632 induced hazy and severely edematous corneas, thus indicating that the corneal endothelial dysfunctions were sustained, comparable with those of the control corneas. Slit-lamp microscopy performed at 48 hours after injection revealed complete corneal transparency with the iris and the pupil clearly observed in the eyes injected with RCECs with Y-27632, whereas the iris and pupil could not be observed in the eyes injected with RCECs without Y-27632 and in the control eyes in which the corneal endothelium was mechanically scraped (Figure 1B). Consistent with the slit-lamp microscopy findings, histological analysis performed at 14 days after injection also revealed that the eyes injected with RCECs with Y-27632 had a normal range of corneal thickness, whereas those without Y-27632 exhibited a thick cornea with severe stromal edema. The corneal thicknesses of those specimens were 409 μm and 730 μm, respectively (Figure 1C). In the eyes injected with RCECs with Y-27632, the corneal edema was moderate (<800 μm) at day 1, yet gradually recovered to the normal level. In contrast, in both the control eyes and the eyes injected with RCECs without Y-27632, prominent corneal edema (>1200 μm) was observed at day 1, and corneal edema persisted throughout the observation period (Figure 1D). Next, possible complications associated with cell injection into the anterior chamber were investigated, as the injected cells might possibly interfere with normal aqueous humor outflow and produce an increase in intraocular pressure. No abnormal deposition of the injected DiI-positive RCECs onto the trabecular meshwork or onto the iris and no anatomical abnormality such as mechanical angle closure or peripheral anterior synechia were detected (Figure 2A). Intraocular pressures were found to be in the normal range in all groups (Figure 2B). To evaluate the injected CECs proliferation status in vivo, a flat-mount cornea was examined at 14 days after injection. Immunofluorescence analysis using the Ki-67 monoclonal antibody (a marker of cell proliferation) revealed that the cell cycle of the nearly all of the injected cells was arrested 2 weeks after injection (Figure 2C). These results indicate that ROCK inhib