Thrombospondin is Up Regulated by Proteasome Inhibition

Abstract

Purpose : To investigate the effect of proteasome inhibition in neovascularization induced by limbal stem cell deficiency (LSCD). By understanding the molecular mechanisms that control neovascularization, it may be possible to design therapeutic strategies to selectively prevent or halt pathologic vascular growth. The anti-angiogenic thrombospondin-1 (TSP-1) has been shown to be a natural inhibitor of neovascularization. An increase in TSP-1 expression might decrease corneal vascularization in case of LSCD

Methods : Rabbits with experimentally induced LSCD were used to quantify the expression of TSP-1. Cultured Autologous Oral Mucosal Epithelial Cell Sheets (CAOMECS) was grafted back to reconstruct corneal epithelium. Using immunofluorescent staining, the levels of TSP-1 were compared between control, diseased and CAOMECS treated corneas. In addition, oral mucosal epithelial cells were cultured and treated with proteasome inhibitor to analyze TSP-1 levels. Treated cells were analyzed for the expression levels of (TSP-1) and its downstream signaling involved in angiogenesis.

Results : The immunofluorescent staining of normal healthy ocular surface showed that TSP-1 was expressed in corneal epithelial cells, and had a much lower expression in conjunctival epithelial cells. The limbal cells did not express TSP-1. In the LSCD diseased ocular surface, TSP-1 expression was greatly decreased in cornea epithelial cells. Conjunctival and goblet cells were present on the corneal surface. CAOMECS-grafted corneas greatly expressed TSP-1, in comparison to LSCD-disease corneas, but to a much lower extent compared to the healthy corneas. In an attempt to stimulate TSP-1 expression, cultured oral mucosal epithelial cells were treated with proteasome inhibitor. Results showed that treatment with proteasome inhibitor lead to an increase in the expression levels of TSP-1.

Conclusions : TSP-1 expression may be activated in CAOMECS tissue prior to grafting back onto cornea to reconstruct the ocular surface, and maintaining corneal avascularity in case of LSCD.

This is a 2021 ARVO Annual Meeting abstract.