Abstract
Purpose:
To study the location of progenitor cells and their interaction with surrounding cells during posterior cornea development.
Methods:
Sectioned Corneas and collagenase digested corneal flat mounts from C57BL/6 wild type mice were used to study the expression of progenitor cells markers during corneal maturation. Nestin, expressed during early stages of development in the central nervous system and nerve growth factor receptor (NGFR), a neural crest progenitor cell marker, as well as Ki67, a proliferation marker were studied using immunofluorescence microscopy from postnatal day 4 (P4) to postnatal day 90 (P90). F-actin was localized using phalloidin to evaluate endothelial - keratocytes interactions.
Results:
Nestin and NGFR are homogeneously expressed in all corneal cell layers in the immature cornea (P4). There are also endothelial - keratocytes interactions present along the central and peripheral cornea in the P4 corneas. Nestin and NGFR expression were down regulated during corneal maturation with minimal or no expression present in the mature P90 central cornea. In contrast, nestin and NGFR expressing cells were exclusively located at the posterior cornea periphery in the P90 corneas. Few endothelial - keratocytes interactions were noted only in the peripheral cornea. Clusters of nestin positive and NGFR positive cells were identified in the subendothelial space in the mature cornea periphery. Ki67 was expressed in all corneal layers of the immature P4 corneas, but a higher density of Ki67 positive nuclei were noted in the periphery. No posterior stroma expression was noted in the maturing P30 corneas.
Conclusions:
Endothelial - keratocytes interactions and progenitor cells are present in the entire cornea during early postnatal life when all cell layers harbor Ki67+ cells. Endothelial-keratocytes interactions and progenitor cells localize to the corneal periphery with maturation and at this time the expression of Ki67+ cells is down regulated. The existence of quiescent progenitor cells interacting with surrounding cells in the mature posterior cornea is proposed as a source for posterior stromal and endothelial repair.
Keywords: 480 cornea: basic science •
481 cornea: endothelium •
484 cornea: stroma and keratocytes