In Vitro Expansion of Corneal Endothelial Cells for Clinical Application: Current Update

Abstract

:Endothelial dysfunction is one of the leading causes of corneal blindness and one of the common indications for keratoplasty. At present, the standard of treatment involves the replacement of the dysfunctional endothelium with healthy tissue taken from a donor. Because there is a paucity of healthy donor tissues, research on the corneal endothelium has focused primarily on expanding these cells in the laboratory for transplantation in an attempt to reduce the gap between the demand and supply of donor tissues for transplantation. To expand these cells, which are nonmitotic in vivo, various mitogens, substrates, culture systems, and alternate strategies have been tested with varying success. The biggest challenge has been the limited proliferative capacity of these cells compounded with endothelial to mesenchymal transition that alters the functioning of these cells and renders them unsuitable for human transplantation. This review aims to give a comprehensive overview of the most common and successful techniques used in the culture of the cells, the current available evidence in support of epithelial to mesenchymal transition (EMT), alternate sources for deriving the corneal endothelial cells, and advances made in transplantation of these cells.

Focus on seed cells: stem cells in 3D bioprinting of corneal grafts

“…In contrast, corneal stromal cells and endothelial cells may easily lose their original phenotypes during in vitro culture ( Yam et al, 2015a ; Hazra et al, 2022 ). Corneal stromal keratocytes can transform into fibroblasts, proliferate and migrate during in vitro culture, and upregulate the expression of ECM proteins, leading to graft opacification ( Yam et al, 2015a ; Yam et al, 2020 ).…”

“…Compared to that of cell lines, their proliferation decreases gradually during differentiation, which increases the safety of regeneration therapies. Due to the obstacles caused by the in vitro culture of keratocytes and endothelial cells, pluripotent stem cells have shown great promise in the 3D bioprinting of corneal stromal and endothelial tissue ( Yam et al, 2015a ; Yam et al, 2020 ; Hazra et al, 2022 ). In addition, mesenchymal stem cells (MSCs) are widely used due to their unique immunomodulatory function, especially in the field of tissue transplantation ( Ma et al, 2006 ; Joyce et al, 2012 ; Podestà et al, 2020 ).…”

“…In addition, enough seed cells must be added to the bioink to ensure the biological function of the product. However, the essential cellular components of corneal tissue, including stromal cells and endothelial cells, etc., are difficult to expand in vitro ( Yam et al, 2015a ; Hazra et al, 2022 ). Therefore, it is highly important to find suitable seed cells to replace the primary cells for corneal tissue engineering.…”

Current state of endothelial cell therapy

“…Additionally, compared to cells from young donors, cells from older donors grow more slowly, and exhibit high heterogeneity as well as characteristics of senescence [26]. Also, the proliferative capacity of HCECSs is limited to an average of three-to-four subcultures, beyond which the cells become fibroblastic or senescent [27].…”