Finding Corneal Limbal Stem Cells for Transplantation Could be as Easy as ABCB5

A team of Boston-based researchers have developed a method that allows for limbal stem cells (LSCs) to be identified in eye transplant donors’ corneas prior to transplant. Several organizations, including Massachusetts Eye and Ear Infirmary, Boston Children’s Hospital and (1) Brigham and Women’s Hospital collaborated to study ABCB5 knockout mice in order to gain insight into this protein’s role in the growth and maintenance of LSCs.

As it transpires, the transmembrane glycoprotein ABCB5 may be incredibly valuable to the growth of human corneal tissue. Mice lacking the ABCB5 gene lose LSCs and exhibit impaired damage healing relative to mice with the gene. All wasn’t lost for these knockout mice; ABCB5-positive LSC grafts managed to restore normal corneal function to the knockout mice, suggesting that ABCB5 plays a major role in the maintenance and repair of these stem cells, and with it, the function and wound healing ability of the cornea. Markus Frank of Boston Children’s Hospital explained, “ABCB5 allows limbal stem cells to survive, protecting them from apoptosis.”

There’s an immediate practical application for this new knowledge too – the identification of LSCs for transplant. “Limbal stem cells are very rare, and successful transplants are dependent on these rare cells” explains Bruce Ksander of the Massachusetts Eye and Ear/Schepens Eye Research Institute. The issue has been that nobody can tell if LSCs are present, or how many there are. If there are few or none, the transplant will almost certainly fail. Clinical-grade anti-ABCB5 antibodies are currently under development.