Ischemic tissue injury and progenitor cell tropism: significant contributors to the pathogenesis of pterygium.

Pterygium is a common ocular surface disease characterized by triangular wing-like growth consisting of subconjunctival hypertrophic connective tissue. Pterygium is easily complicated by adhesion to the eyelid and diplopia related to motility restriction of the eyeball. Beyond the cosmetic problems, this condition has a catastrophic effect on quality of life. Post-surgical recurrence rates of pterygium excision have been reported to be very high. Therefore, identifying the distinct pathogenic pathways of the disease may lead to new therapeutic strategies with lower risk of treatment failure. Based on the relatively low vascularity and known-predominance of disease occurrence in the nasal conjunctiva of normal eyes, we proposed that hypoxic ischemic injury can elicit the development of pterygium. Here, we review hypoxia-inducible factor (HIF)-1alpha-induced activation of the stromal cell-derived factor-1 (SDF-1)/chemokine receptor type 4 (CXCR4) signaling pathway as a possible mechanism. Supporting this concept of pathogenic mechanism, we also highlight bone marrow-derived progenitor cell tropism as a main contributor to pterygium pathogenesis.