Localization of TGF-β type II receptor and ED-A fibronectin in normal conjunctiva and failed filtering blebs

PURPOSE: The cytokine transforming growth factor-β (TGF-β), and the ED-A splice variant of the extracellular matrix protein fibronectin modulate wound healing and scar formation. To further elucidate their possible role in filtering bleb scarring after glaucoma surgery in human eyes in vivo, we studied the cell type specific localization of TGF-β receptors and the presence of ED-A fibronectin in sections of normal conjunctiva and scarred filtering blebs. METHODS: Cryosections of normal conjunctiva (four patients) and scarred filtering blebs (seven patients) were studied by double-label immunofluorescence. Antibodies against PECAM-1 and prolyl-4-hydroxylase allowed for specification of vascular endothelial cells and activated fibroblasts, respectively. TGF-β receptor type II (TGF-β-RII), α-smooth muscle actin, O-linked sialoglycoprotein, fibronectin and the ED-A fibronectin splice-variant were also detected using specific antibodies. Labeled sections were viewed with a confocal laser scanning microscope. RESULTS: Vascular endothelial cells expressed TGF-β-RII in both normal and scarred tissue. TGF-β-RII was sparsely detected in the fibroblasts of normal conjunctiva while it was strongly expressed in most fibroblasts of the scarred filtering blebs. Similarly, ED-A fibronectin was not detected in the extracellular matrix of normal conjunctiva but abundantly present in scarred filtering blebs. CONCLUSIONS: Filtering bleb scarring is associated with an abundant expression of TGF-β receptors in activated fibroblasts and the deposition of the fibrogenic ED-A fibronectin splice-variant. These data support the concept of targeting TGF-β signaling to prevent scar formation after filtering glaucoma surgery.