Transforming growth factor beta receptor 2 (Tgfbr2) deficiency in keratocytes results in corneal ectasia

Purpose: We hypothesized that Transforming growth factor beta receptor 2 (Tgfbr2) deletion in keratocyte (Tgfbr2(kera-cko)), the corneal stroma cell, can result in corneal thinning and generate a potential model for Cornea Ectasia (CE). Methods: Corneal thickness of Tgfbr2(kera-cko) and Tgfbr2(Ctrl) was examined with Optical Coherence Tomography (OCT) at post-natal (P) days 42 and 70, respectively. Histological H&E staining, transmission electron micrograph (TEM), and immunofluorescence staining (IFS) were harnessed to examine corneal cell morphology, proliferation, differentiation, and collagen fibrils. Results: Slit-Lamp revealed that corneas were transparent in both Tgfbr2(kera-cko) and Tgfbr(2Ctrl), however, Tgfbr2(kera-cko) cornea was 33.5% and 42.9% thinner as compared with those of Tgfbr2(Ctrl) at P42 and P70, respectively. H&E and semithin section staining with toluidine blue-O confirmed that Tgfbr2(kera-cko) cornea has a thinner stroma. In contrast, the epithelium in Tgfbr2(kera-cko) was substantially thicker. The cell proliferation marker Ki67 expression level increased similar to 9% in Tgfbr2(kera-cko) corneal epithelium as compared with that in Tgfbr2(Ctrl), however, the Krt14 and Krt12 expression pattern was not obviously changed in Tgfbr2(kera-cko) corneal epithelium. It was noticed that Col1a1 expression was substantially reduced in Tgfbr2(kera-cko) as compared with that in Tgfbr2(Ctrl). TEM showed that keratocytes were unhealthy and stromal collagen fibril density was significantly reduced in Tgfbr2(kera-cko) as compared with that in Tgfbr2(Ctrl) cornea. Moreover, mechanical eye-rubbing on Tgfbr2(kera-cko) resulted in corneal hydrops and edema. Conclusion: Tgfbr2 in keratocytes is indispensable for the corneal stroma at postnatal homeostasis. The cornea phenotype manifested in these Tgfbr2(kera-cko) mice resembles corneal ectasia disease in humans.