Experimental models of corneal endothelial cell therapy and translational challenges to clinical practice.

The human corneal endothelium (CE) is a post-mitotic monolayer of endothelial cells, thought to be incapable of in vivo regeneration. Dysfunction of the CE is a commonly cited indication for corneal transplantation, with corneal blindness being the fifth most common cause of blindness globally. In 2012 alone 184,576 corneal transplants were performed in 116 countries (Gain et al., 2016). Presently, outcomes following human corneal transplantation have been reported to have over 97% success rate in restoring the recipient's vision (Patel et al., 2019). However, the continuing demand for cadaveric human corneas has driven research into alternative sources of CE and with the advent of protocols to produce cultured hCECs there is now the potential for cell therapy to regenerate the damaged CE. This review aims to examine the merits and limitations of different types of human and animal models used so far to test the concept of CE cell therapy.

Development and evaluation of porcine atelocollagen vitrigel membrane with a spherical curve and transplantable artificial corneal endothelial grafts.

PURPOSE: To develop a collagen vitrigel (CV) optimized as a corneal endothelial cell (CEC) carrier and create an artificial corneal endothelial graft. METHODS: We first developed a flat-shaped collagen vitrigel for regenerative medicine (CV-RM) using porcine atelocollagen and ultraviolet (UV) irradiation. The optimal UV amount was determined by measuring the CV-RM transparency under various irradiating conditions. The collagen vitrigel for corneal endothelial regenerative treatment (CV-CERT), a transparent porcine atelocollagen with a curved shape, was made using spherically curved molds and UV irradiation. The membrane permeability of the CV-CERT was tested in vitro. The biocompatibility, transparency, and adhesiveness of the CV-CERT were evaluated in rabbit eyes. We also developed a culture technique for distributing human CECs on the curved CV-CERT. RESULTS: The optimal amount of UV irradiation for CV-RM transparency was 2400 mJ/cm(2). Membrane permeability of CV-CERT at day 5 was higher than that of commercially available CV (P = 0.032). The CV-CERT was transparent and biocompatible in rabbit corneas for up to 4 months. The CV-CERT remained attached to the rabbit corneal posterior surface, whereas the flat-shaped CV-RM, differing only in shape from the CV-CERT, dislocated soon after surgery. Human CECs seeded on the CV-CERT using our technique were evenly distributed with a single layer structure and a mean cell density of 2650 ± 100 cells/mm(2). CONCLUSIONS: We developed a transparent and biocompatible porcine-derived atelocollagen vitrigel membrane with a spherical curvature. A transplantable artificial endothelial graft was created by combining cultured human CECs and the CV-CERT.