Immunolabelling of usual and putative limbal stem cells markers on flat mounted whole human corneas

AbstractPurposeThe permanent regeneration of the human corneal epithelium involves the proliferation of basal cells of corneal epithelium for compensating for daily desquamation (Majo et al. Nature 2008) and of limbal stem cells (LSCs, Cotsarelis, Cell 1989) located in limbal crypts that can be stimulated in case of important epithelial lesion. Many markers of LSCs had been described in the literature but some are controversial, particularly for their specificity.AimTo evaluate the specificity of the main LSC markers proposed in the literature and map their expression on the surface of the cornea.MethodsReferenced or potential markers of LCSs were tested on cross‐sections of fresh human corneas (body donation to Sciences, time between death‐retrieval‐fixation <21 hr) using a standard technique of immunohistochemistry: ABCB5, ΔNp63, P63, ABCG2, Pax6, CK15, CK17, N‐cadherin, Connexin 43, EGFR, vimentin, Sox2, OCT 4. Secondly, antibodies that showed positivity on cross sections were used for immunolabelling flat‐mounted whole cornea to map their expression.ResultsNone of 13 markers was exclusively located at the basal layer of the limbal epithelium. Nevertheless, CK15 appears to be the most promising marker because of its very strong staining in the limbal basal cell layer. However, its staining was also found, less intense, in basal layer of conjunctival epithelium and medium layers of limbal epithelium. On flat‐mounted corneas, CK15 was expressed in a circular ring corresponding to the anatomical limbus, but CK15+ cells were not restricted within the Vogt palisades (or limbal crypts on cross sections).ConclusionsA marker of cells located exclusively in limbal crypts or Vogt palisades and presumed to be the true LSCs is still missing. CK15 seems the most specific markers for limbal basal cells but not restricted to specific niches.