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

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).

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.

Slit-Lamp revealed that corneas were transparent in both Tgfbr2^kera-cko and Tgfbr2^Ctrl, 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 ∼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.

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.