Abstract
Purpose: :
P2X7 receptors are purinergic receptors, which are implicated in pain, inflammation and immune functions. We showed previously that the corneal epithelium of P2X7-/- mice showed reduced ability to heal compared to WT counterparts. Our goal is to determine the role of P2X7 in the integrity of the corneal stroma.
Methods: :
The stromas of P2X7-/- strain B6.129P2-P2rx7 and their wild-type (WT) counterparts, strain C57BL/6J were examined using immunohistochemistry using confocal microscopy, real-time PCR and transmission electron microscopy. Changes in proteoglycans, collagens and lysyl oxidase were examined. The lack of P2X7 in the KO in the cornea was confirmed.
Results: :
P2X7 is expressed in the corneal epithelium, sensory neurons and corneal keratocytes. We found that the basement membrane zone in the region of the wound margin was fragile. Hemidesmosomes were detected back from the wound margin. However in the KO mice there was a reduction or absence of perlecan, a heparan sulfate proteoglycan known to be localized along the basement membrane zone in the wild type counterparts. In comparison perlecan mRNA was upregulated and the protein was more prevalent in the posterior stroma compared to wild type. Additional modifications in expression and localization of decorin, lumican, keratocan and syndecan 1 were detected. The changes in proteoglycan expression were accompanied by alterations in architecture and integrity of the collagen fibrils noted previously. In addition Type III collagen and lysyl oxidase mRNA were upregulated, while Types I and V collagen were decreased.
Conclusions: :
We hypothesize that the lack of P2X7 induces either a "wounded phenotype" or may inhibit the development of the stroma. A model construct is being developed to test the expression under conditions of stress.
Keywords: proteoglycans/glycosaminoglycans • cornea: stroma and keratocytes • wound healing