Purchase this article with an account.
Akhee Sarker-Nag, Tina B McKay, Dimitrios Karamichos; The role of Human Growth Hormone in 3D In Vitro Keratoconus Model. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1928.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Keratoconus (KC) is an ecstatic corneal thinning disease of unknown etiology that affects 1:2000 people worldwide. We recently identified prolactin-inducible protein (PIP) as a novel biomarker for KC, both in vivo and in vitro. Interestingly, PIP was highly regulated by transforming growth factor-β (TGF-β) isoforms (-β1, -β2, and -β3). Previous studies have linked PIP to human growth hormone (HGH) using cancer cell models. Our current study explored the role of HGH in primary human keratoconus cells.
Human corneal fibroblasts (HCF) and human keratoconus cells (HKC) were stimulated for 4 weeks with increasing concentrations of HGH (0.1, 0.2, and 0.5μg/mL) in the presence of a stable Vitamin C derivative (0.5mM) to stimulate extracellular matrix assembly. Cell migration was assessed using scratch assay and Western blot analyses were used to measure differential expression of key TGF-β signaling molecules.
The scratch assay revealed a significant increase in cell migration in the presence of HGH, compared to Controls, in both HCF and HKC. PIP expression was significantly down regulated by more than 2-fold in HCFs but no difference was seen in HKCs. In terms of the TGF-β signaling pathway our data show that upon HGH (0.5μg/mL) stimulation, TGF-β3 expression was significantly up regulated by 4-fold and 1-fold in HCFs and HKCs respectively. Furthermore, a 2-fold up regulation was seen in pSMAD3/SMAD3 in HCFs, but not in HKCs, with 0.2μg/mL HGH treatment. Surprisingly, HGH stimulation did not affect expression of the pro-fibrotic ligands TGF-β1 and TGF-β2 or their receptors TGF-βRI and -βRII.
Our results show that HGH directly modulates PIP expression through the TGF-β signaling pathway in both HCFs and HKCs. These findings suggest an important role for HGH in keratoconus derived cells. HKCs overall are less responsive to HGH indicating an altered modulation of the TGF-β pathway that might explain the fibrotic cellular and ECM characteristics of KC.<br />
This PDF is available to Subscribers Only