βig-h3 is synthesized by corneal epithelium and perhaps endothelium in Fuchs' dystrophic corneas

Purpose. Deposition of abnormal sub-epithelial matrix and posterior collagenous layer by epithelium and endothelium, respectively, in Fuchs' dystrophy gives us the opportunity to determine if these tissues synthesize βig-h3. Methods. Immunohisto-/immunocytochemistry of corneas were conducted with rabbit anti-human βig-h3 and monoclonal antihuman type VI collagen. Labeled sense and anti-sense βig-h3 oligonucleotide probes were used for in situ hybridization. Results. βig-h3-specific fluorescence was found just beneath detached epithelium in the sub-epithelial matrix, abnormal Descemet's membrane and posterior collagenous layer. Type VI collagen co-localized with βig-h3 within abnormal sub-epithelial matrix and corneal stroma adjacent to Descemet's membrane. βig-h3 mRNA was detected in corneal epithelium of dystrophic corneas. Conclusions. Expression of βig-h3 in sub-epithelial matrix and posterior collagenous layer of Fuchs' dystrophy is consistent with the synthesis of new extracellular matrices by epithelial and endothelial tissues. βig-h3 mRNA in corneal epithelium further supports an epithelial source of this protein. Endothelial synthesis of βig-h3 is based on circumstantial evidence due to cell loss during surgical and histological procedures. Co-localization of βig-h3 with type VI collagen in abnormal sub-epithelial matrix and at the stromal/Descemet's membrane interface suggest this collagen in association with βig-h3 interacts with these tissues and anchors them to the adjacent stroma.