Stem Cells in the Cornea

Abstract

The cornea is the tough, transparent tissue through which light first enters the eye and functions as a barrier to debris and infection as well as two-thirds of the refractive power of the eye. Corneal damage that is not promptly treated will often lead to scarring and vision impairment. Due to the limited options currently available to treat corneal scars, the identification and isolation of stem cells in the cornea has received much attention, as they may have potential for autologous, cell-based approaches to the treatment of damaged corneal tissue.

Keywords: Cornea; Stem cells.

Figure 1

The cornea is composed of three cellular layers: the epithelium, stroma, and endothelium. The vascular limbal region is located at the peripheral cornea and is bordered by the conjunctiva—this region is the proposed niche for stem cell populations in each layer. LESC, limbal epithelial stem cell; TAC, transit-amplifying cell; CSSC, corneal stromal stem cell.

Figure 2

Stem cell markers/characteristics. Orange, limbal epithelial stem cell (LESC) markers, expression generally compared to central epithelial cells; green, human corneal stromal stem cell markers; and purple, proposed markers and characteristics corneal endothelial progenitor cells.

Figure 3

The corneal endothelium serves as a leaky barrier between the corneal stroma (anterior) and anterior chamber (posterior). Water passively moves from the ac into the stroma, while protein and other nutrients (such as glucose) are actively transported by corneal endothelial cells. To pump water from the stroma into the anterior chamber, bicarbonate is actively pumped out of the endothelial cells (along with other ions) and water follows.