Aquaporin 1 Positive Mesenchymal Cell Imply Existence Of Cornea Limbal Niche Cells

Abstract

Purpose: : Stem cells have a specialized microenvironment for maintaining self-renewal and multipotent capacities. It is believed that a cornea epithelial stem cell niche exists in the limbus. To characterize the niche of limbal epithelial stem cells, we observed the limbal basal epithelial layer by histological analysis.

Methods: : Frozen limbal tissue sections were prepared from donor corneal sclera after cornea transplant. Sections were analyzed immunohistochemistry, electron microscopy and confocal microscopy. We stained the sections with N-cadherin and keratin 15 (Limbal basal epithelial layer), aquaporin 1 (AQP1; subepithelial cells), vimentin (mesenchymal cells), CD31 (vascular endothelial cells), podoplanin (lymphatic endothelial cells) and MART-1 (melanocytes).

Results: : AQP1 positive (AQP1+) cells were observed as non-epithelial cells in the subepithelial stroma. These AQP1+ cells were CD31, podoplanin, MART-1 negative and vimentin positive suggesting a mesenchymal lineage. When we made a thorough search of limbal basal cells by confocal microscopy, AQP1+ were observed in the proximity of N-cadherin positive limbal basal epithelial cells. Furthermore, electron microscope revealed the presence of stromal cells immediately beneath the epithelial basal membrane that formed cellular adhesions with limbal basal epithelial cells.

Conclusions: : AQP1 positive cells immediately beneath epithelial basement membrane may be mesenchymal niche cells that directly interact with N-cadherin positive limbal basal epithelial cells.

Keywords: cornea: basic science • microscopy: confocal/tunneling • microscopy: electron microscopy