Stem cell (SC) therapy is the main treatment modality to restore vision in patients with limbal stem cell deficiency. If corneolimbal epithelial stem cells (LESC) can be readily identified, isolated and maintained ex vivo, better quality grafts can be generated for patients with this debilitating disease. With prior knowledge that the extracellular matrix protein vitronectin (VN) is present within the LESC niche and that it supports SC in vitro, we postulated that the VN receptor αvβ5 is expressed by, and can be used to identify and isolate SC within the cornea.Methods
Epithelial cells were isolate and expand from cadaveric human corneas and αvβ5 expression determined by flow cytometry and immunofluorescence. Integrin expressing cells were isolated by magnetic-activated cell sorting then assessed by immunocytology, colony forming efficiency, RT-PCR and microarray analysis.Results
Integrin αvβ5+ cells co-localized to N-cadherin+/CK-15+ putative LESC. αvβ5 was restricted to 3% of the total epithelial cells, which expressed more SC markers and formed more colonies compared to αvβ5- cells. Transcriptional profiling of αvβ5+/- cells by global gene array identified several interferon-inducible genes, including the chemokine IP-10, which localized to LESC. The role of IP-10 in these cells is yet to be elucidated, but may be involved in immunoprotection by attracting mesenchymal SC into the corneal stroma.Conclusion
Integrin αvβ5 is a candidate SC marker since its expression is restricted and αvβ5+ limbal epithelial cells have properties of LESC. Knowledge of the niche’s composition and the genes expressed by its SC will facilitate isolation and maintenance of these cells in culture for therapeutic purposes.