The cornea is our window to the world and our vision is critically dependent on corneal clarity and integrity. Cornea is also one of the most rapidly regenerating mammalian tissues undergoing full turnover over the course of approximately one to two weeks. This robust and efficient regenerative capacity is dependent on the function of stem cells residing in the limbus, a structure marking the border between the cornea and the conjunctiva. Loss of limbal stem cells as a result of injury or disease results in corneal blindness, one of the most common causes of vision loss in the world.
Limbal stem cells have attracted a lot of interest in the field of regenerative medicine because of their unique ability to fully restore the whole cornea upon transplantation. In their review, Gonzalez and co-workers review several important aspects of limbal stem cell biology such as limbal stem cell identification, developmental origin and therapeutic potential. They point to the importance of prospective cell isolation techniques, and the use of developmental lineage tracing approaches for the identification of bona fide limbal stem cells. In this regard, they highlight the recent discovery that ABCB5, a cell surface protein, marks limbal stem cells capable of long-term corneal restoration upon grafting to mice with experimentally induced corneal blindness.
Immunofluorescent image of corneal epithelium from a 1 month-old mouse, in which ABCB5-positive cell progeny is labeled in red. These findings show that an ABCB5-expressing precursor cell gives rise to the entire self-renewing corneal epithelium during development and regeneration. The white square on the left indicates the location of the limbus, with a high magnification image shown on the right.
In addition, using genetic lineage tracing of ABCB5-positive cell progeny, they show that an ABCB5-expressing precursor cell gives rise to the entire self-renewing corneal epithelium during development and regeneration. The recent success in prospective limbal stem cell isolation based on ABCB5 expression and the capacity of this limbal stem cell population for long-term corneal restoration following transplantation in preclinical models of corneal disease underline the considerable potential of pure limbal stem cell formulations for clinical therapy.
Kindly contributed by Natasha Frank, MD, FACMG.
