Stem potentialities of the human iris – An in situ immunohistochemical study

According to recent findings multiple human tissues harbor stem cells which, in turn, have different levels of stemness. We performed an immunohistochemical study on paraffin-embedded samples to test if the in situ stromal cells of the iris of the human eye (EI) have immune stem/progenitor phenotypes. Eviscerated post-traumatic eyes from eight patients were studied. These irises were found to contain fibroblastoid stromal cells with a CD34+/CD45+/CD105+/CD117+/DOG1+/PDGFR-α+/vimentin+/nestin−/collagen III− phenotype. These were assumed to be possible stem/progenitor cells involved in physiological processes of iridial stromal maintenance. All the vascular endothelia were CD34+/CD105+/vimentin+. Newly formed nestin+ endothelia were also found; this finding was supported by evidence of filopodia-projecting CD34+ endothelial tip cells, which demonstrated active processes of sprouting angiogenesis. The phenotype of the stromal cells also suggests a role of the circulating fibrocytes in iridial regenerative processes.