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Yen-Chiao Wang, Yujin Zhang, Lung-Kun Yeh, Chia-Yang Liu; TGF beta signaling in stroma is essential for corneal development. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4155.
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© ARVO (1962-2015); The Authors (2016-present)
Transforming growth factor beta (TGF-β) is believed to be the most important growth factor involved in keratocyte-myofibroblast conversion. TGF-b dysfunction has been postulated to be associated with keratoconus. Herein, we examined the hypothesis that conditionally ablation of TGF-β signaling pathway in keratocytes can perturb corneal development and generate a potential model for keratoconus.
TGF beta receptor 2 (Tgfbr2) was designed to be conditionally knocked out (Tbr2cko) from keratocytes. A novel triple transgenic mice, KerartTA;tetO-Cre;Tbr2f/f, wereadministeredwith doxycycline (Dox) from postnatal day 1 (P1) to various developing stages including postnatal day 42 (P42), P49, P56, and P63. Optical coherence tomography (OCT), H&E histological staining, transmission electron micrograph (TEM), and immunofluorescence staining (IFS) were performed to examine corneal thickness, morphology, and cell behaviors as compared with the wild-type littermates (WT).
The OCT scanning appeared a doom-shaped cornea in the WT but an irregular curvature with hyper-reflectivity of the Tbr2cko cornea. Moreover, overall corneal thickness in Tbr2cko becomes 25% thinner than that of WT (80±5 mm vs 110±6 mm, p<0.05, n=4) at P42 and progresses to 45% thinner (67±3 mm vs 120±2 mm, P<0.05, n=4) at P63. Interestingly, TEM and H&E staining showed that poorly differentiated keratocyte with significantly lower density in Tbr2cko cornea, however, the corneal epithelium thickness increased with enlarged and irregular cell morphology. In addition, corneal endothelium becomes hypertrophy with thickened Descemet membrane. The immunostaining of Ki67 for cell proliferation, K14, and K12 for cell differentiation indicated cell proliferation and corneal type differentiation were unchanged in Tbr2cko cornea. Furthermore, MMP2 expression level increased but MMP9 and TIMP1 remained no change as compared with the WT.
These data suggest that TGF-β signaling is indispensable for corneal morphogenesis. The aforementioned corneal phenotypes in this Tbr2cko triple transgenic mouse strain resemble keratoconus in human.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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