Differential Expression of the Stem Cell Markers in Rabbit and Dog Lenses

Abstract

Purpose: : It has been suggested that the ocular lens contains the stem cells in the germinal zone (sub-equatorial region) . However, our previous studies have demonstrated that the central but not the periphery epithelial cells in the young rabbit lens display telomerase activity (Huang et al., 2005. IOVS). To clarify this discrepancy, we have analyzed the expression patterns of two stem cell markers in both central and periphery epithelial cells of rabbit and dog lenses with different ages.

Methods: : The capsular lens epithelia were dissected out for extraction of total RNA. RT-PCR was used for mRNA expression of various stem cell marker genes.Immunocytochemistry was used for detection of various stem cell marker proteins.

Results: : The two stem cell markers, CD9 and Sox2, are initially expressed in similar levels in the central and the periphery lens epithelial cells of younger rabbit lenses. As rabbit grows up to 6 months, the expression levels of CD9 and Sox2 become decreased in the periphery epithelial cells but enhanced in the central epithelial cells. In dog lens, however, the two stem cell markers are more strongly expressed in the periphery epithelial cells than the central epithelial cells of the younger dog lens. As the dog grows up to 3 months, the expression levels of CD9 and Sox 2 in dog lens display similar changing patterns as observed in rabbit lens.

Conclusions: : The central epithelial cells of the mature rabbit and dog lenses have increased levels of stem cell marker expression and are telomerase positive. Together, these results suggest that the central epithelium of the rabbit and dog lenses likely contain lens stem cells.

Keywords: development • gene/expression • transcription