Abstract
Purpose: :
It was suggested that corneal epithelial stem cells are localized in the basal layer of the limbal epithelium (LE), but their properties remain poorly understood. Recently, it was reported that side population (SP) cells with the capacity to efflux Hoechst 33342 and isolated from various tissues and species, show stem cell phenotypes. Here, we provide a partial characterization of LE–SP cells.
Methods: :
SP cells and non–SP (NSP) cells were isolated from rabbit LE by fluorescence activated cell sorting (FACS) and analyzed for mRNA expression, the capacity for proliferation, TERT activity, and cell cycle state.
Results and Conclusions: :
Approximately 0.4% of LE cells showed the SP phenotype. These cells had higher mRNA expression of stem cell markers than NSP cells, and undetectable expression of the markers for differentiated corneal epithelial cells. The cell cycle of SP cells was arrested at G0/G1 phase, coinciding with the findings that SP cells have lower TERT activity and capacity for proliferation under typical culture conditions, compared to NSP cells. Moreover, SP cells showed higher gene expression of CDK inhibitors, of which mouse bone marrow SP cells also showed higher expression. These results indicate that LE–SP cells have stem cell–like properties, including quiescent state.
Keywords: cornea: basic science • cornea: epithelium • proliferation