Development of Cell Analysis Software for Cultivated Corneal Endothelial Cells.

PURPOSE: To develop analysis software for cultured human corneal endothelial cells (HCECs). METHODS: Software was designed to recognize cell borders and to provide parameters such as cell density, coefficient of variation, and polygonality of cultured HCECs based on phase contrast images. Cultured HCECs with high or low cell density were incubated with Ca-free and Mg-free phosphate-buffered saline for 10 minutes to reveal the cell borders and were then analyzed with software (n = 50). RESULTS: Phase contrast images showed that cell borders were not distinctly outlined, but these borders became more distinctly outlined after phosphate-buffered saline treatment and were recognized by cell analysis software. The cell density value provided by software was similar to that obtained using manual cell counting by an experienced researcher. Morphometric parameters, such as the coefficient of variation and polygonality, were also produced by software, and these values were significantly correlated with cell density (Pearson correlation coefficients -0.62 and 0.63, respectively). CONCLUSIONS: The software described here provides morphometric information from phase contrast images, and it enables subjective and noninvasive quality assessment for tissue engineering therapy of the corneal endothelium.

Corneal Endothelial Cells Have an Absolute Requirement for Cysteine for Survival.

PURPOSE: The aim of this study was to evaluate which amino acid(s) among the 20 standard protein amino acids is indispensable for the survival of cultured human corneal endothelial cells (HCECs). METHODS: HCECs were cultured in amino acid screening media that were missing 1 specific amino acid, and cell growth was evaluated. After this first selection, we conducted a further evaluation of cell growth in response to the addition of 4 amino acids (cysteine, methionine, valine, and arginine) to amino acid-free culture media. We then evaluated the antioxidant effect of cysteine compared with other antioxidants in terms of apoptosis of HCECs, rabbit corneal endothelial cell (CECs), monkey CECs, and ex vivo human donor corneas. RESULTS: Culture in an amino acid-free Dulbecco Modified Eagle Medium (DMEM) decreased the cell numbers to 11.0% when compared with culture in normal DMEM. Removal of cysteine, methionine, valine, or arginine from DMEM significantly suppressed cell numbers (27.7%, 61.4%, 75.5%, and 60.6%, respectively) (P < 0.01), whereas removal of other amino acids did not significantly decrease cell numbers. A lack of cysteine induced apoptosis, but addition of antioxidants reversed this. Removal of cysteine induced in vitro apoptosis in HCECs, rabbit CECs, monkey CECs, and ex vivo human donor corneas, whereas the presence of cysteine almost completely suppressed this apoptosis. CONCLUSIONS: Cysteine seems to be an indispensable amino acid for HCEC growth and survival. Its necessity might reflect a high requirement for antioxidants to protect HCECs from oxidative stress, as HCECs have high aerobic metabolic activity.

Generation and Feasibility Assessment of a New Vehicle for Cell-Based Therapy for Treating Corneal Endothelial Dysfunction.

The corneal endothelium maintains corneal transparency by its pump and barrier functions; consequently, its decompensation due to any pathological reason causes severe vision loss due to corneal haziness. Corneal transplantation is the only therapeutic choice for treating corneal endothelial dysfunction, but associated problems, such as a shortages of donor corneas, the difficulty of the surgical procedure, and graft failure, still need to be resolved. Regenerative medicine is attractive to researchers as a means of providing innovative therapies for corneal endothelial dysfunction, as it now does for other diseases. We previously demonstrated the successful regeneration of corneal endothelium in animal models by injecting cultured corneal endothelial cells (CECs) in combination with a Rho kinase (ROCK) inhibitor. The purpose of the present study was to optimize the vehicle for clinical use in cell-based therapy. Our screening of cell culture media revealed that RELAR medium promoted CEC adhesion. We then modified RELAR medium by removing hormones, growth factors, and potentially toxic materials to generate a cell therapy vehicle (CTV) composed of amino acid, salts, glucose, and vitamins. Injection of CECs in CTV enabled efficient engraftment and regeneration of the corneal endothelium in the rabbit corneal endothelial dysfunction model, with restoration of a transparent cornea. The CECs retained >85% viability after a 24 hour preservation as a cell suspension in CTV at 4°C and maintained their potency to regenerate the corneal endothelium in vivo. The vehicle developed here is clinically applicable for cell-based therapy aimed at treating the corneal endothelium. Our strategy involves the generation of vehicle from a culture medium appropriate for a given cell type by removing materials that are not favorable for clinical use.

Effect of the Rho-Associated Kinase Inhibitor Eye Drop (Ripasudil) on Corneal Endothelial Wound Healing.

PURPOSE: Ripasudil (Glanatec), a selective rho-associated coiled coil-containing protein kinase (ROCK) inhibitor, was approved as a glaucoma and ocular hypertension treatment in Japan in 2014. The purpose of this study was to investigate the feasibility of using ripasudil eye drops to treat corneal endothelial injuries. METHODS: Cultured human corneal endothelial cells (HCECs) were treated with ripasudil, and 5-bromo-2'-deoxyuridine (BrdU) incorporation was evaluated by ELISA. A rabbit corneal endothelial damage model was also created by mechanically scraping the corneal endothelium, followed by topical ripasudil eye drop application for 2 weeks. The anterior segment was evaluated by slit-lamp microscopy, and central corneal thickness was measured by ultrasound pachymetry. Corneal specimens were evaluated by phalloidin staining and immunohistochemical analysis using antibodies against Ki67, N-cadherin, and Na+/K+-ATPase. RESULTS: Many more BrdU-positive cells were observed among the HCECs treated with ripasudil (0.3-30 µM) than among the control HCECs. Ripasudil-treated eyes in a rabbit model showed 91.5 ± 2.0% Ki67-positive cells after 48 hours, whereas control eyes showed 52.6 ± 1.3%. Five of six corneas became transparent in ripasudil-treated eyes, whereas zero of six corneas became transparent in the control eyes. Regenerated cell densities were higher in the eyes treated with ripasudil than in eyes treated with vehicle. Eyes treated with ripasudil expressed N-cadherin and Na+/K+-ATPase in almost all CECs, whereas this expression was decreased in control eyes. CONCLUSIONS: Ripasudil promoted corneal endothelial wound healing, supporting its development as eye drops for treating acute corneal endothelial damage due to eye surgeries, especially cataract surgery.

Laminin-511 and -521 enable efficient in vitro expansion of human corneal endothelial cells.

PURPOSE: The purpose of this study was to investigate the usefulness of laminin isoforms as substrates for culturing human corneal endothelial cells (HCECs) for clinical application of tissue engineering therapy. METHODS: Expression of specific laminin chains in human corneal endothelium and Descemet's membrane was analyzed at the mRNA and protein levels. The effect of laminin-511 and -521 on cell adhesion and proliferation was evaluated. Recombinant laminin E8 fragments (E8s), which represent functionally minimal forms of laminins, were also evaluated for their effects on cell density and cellular phenotype. The potential involvement of α3ß1 and α6ß1 integrins in laminin signal transduction was also investigated using neutralizing antibodies. RESULTS: Laminin-511 and -521 were expressed in Descemet's membrane and corneal endothelium. These laminin isoforms significantly enhanced the in vitro adhesion and proliferation, and differentiation of HCECs. A cell density of 2200 to 2400 cells/mm2 was achieved when HCECs were cultured on laminin-511 or -521, whereas the density was only 1100 cells/mm2 on an uncoated control. E8s also supported HCEC cultivation with a similar efficacy to that obtained with full-length laminin. Functional blocking of α3ß1 and α6ß1 integrins suppressed the adhesion of HCECs even in the presence of laminin-511. CONCLUSIONS: Laminin-511 and -521 were the laminin isoforms present in Descemet's membrane, and these laminins modulate the adhesion and proliferation of CECs. Laminin E8s represent an ideal xeno-free defined substrate for the culture of CECs for clinical applications.