Differential Impacts on Proteoglycan Expression in the Response to Lens Wounding in Reparative and Pro‐Fibrotic Microenvironments

Ex vivo lens epithelial explant cultures created through a technique that mimics cataract surgery provided an ideal model with which to compare the impacts on proteoglycan expression in the response to wounding in both reparative promoting and pro-fibrotic microenvironments. On their native basement membrane capsule the injured lens epithelium undergoes regenerative repair, with the wound closing within a few days. Their migration across the wound area is led by a population of activated lens resident immune cells. The same leader cell population also directs the wounded epithelium to migrate off the outside edges of the lens explant across the surrounding tissue culture dish, where a pro-fibrotic matrix microenvironment is produced that signals the resident immune cells at the leading edge to acquire a myofibroblast phenotype. We separated the wounded lens explants from those cells on the surrounding culture substrate at different times points over three days post wounding and performed an unbiased RNAseq analysis to identify the changes in proteoglycan expression from time 0 in the environment in which regenerative repair takes place and compared those results to the impact on proteoglycan expression when the same cell populations encountered the microenvironment where fibrosis is induced. In both environments there were changes in expression of proteoglycans associated with promoting cell migration. However, the greatest changes in proteoglycan expression occurred in the fibrosis-inducing environment, which included a subset of SLRPs with known functions in signaling the activation of TGFβ and in mediating collagen fibrillogenesis. The RNAseq results also revealed that in the pro-fibrotic microenvironment there is an induction of cell surface proteoglycans that are associated with mechanotransduction signaling events linked to their role in the assembly of integrin focal adhesion contacts.