Human corneal epithelium and endothelium synthesize βIG-H3 in Fuchs' dystrophy

Purpose. βig-h3, recently discovered in corneal stroma, is associated with type VI collagen. Deposition of abnormal sub-epithelial matrix (SEM) and posterior collagenous layer (PCL) 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 anti-human type VI collagen. Labeled sense and anti-sense βig-h3 DNA probes were used for in situ hybridization. Results. βig-h3 specific fluorescence was found just beneath detached epithelium in SEM, Descemet's membrane and PCL. Type VI collagen co-localized with βig-h3 within abnormal SEM and corneal stroma adjacent to Descemet's membrane. βig-h3 mRNA was detected only in corneal epithelium of dystrophic corneas. Conclusions. Expression of βig-h3 in Fuchs' dystrophy is consistent with the synthesis of new extracellular matrices by epithelial and endothelial tissues. Association of βig-h3 with type VI collagen in abnormal SEM and at the stromal/Descemet's membrane interface suggest this collagen interacts with these tissues and anchors them to the adjacent stroma. βig-h3 mRNA in corneal epithelium alone indicates that this protein is still being synthesized.