Abstract
Purpose :
During retinal gliosis, biochemical and physiological changes occurring in the retina lead to Müller glia proliferation and overexpression of glial fibrillary acidic protein (GFAP), as well as the release of pro-inflammatory factors such as TNF-α. However, the exact role and regulation of GFAP in human Müller glia is not understood, and the role of TNF-α on the neural differentiation of these cells has not been examined. This study investigated the in vitro effect of TNF-α on GFAP expression by the Müller glial stem cell line MIO-M1 as well as on the photoreceptor differentiation of these cells.
Methods :
MIO-M1 cells were cultured with TNF-α in the presence or absence of FGF-2, taurine, retinoic acid and IGF-1 (FTRI), known to induce photoreceptor differentiation in these cells. RNA was extracted, cDNA produced and GFAP gene expression examined by RT-PCR. Protein expression of GFAP and NR2E3, a marker of photoreceptor differentiation, were examined by western blot analysis. Optical density of bands obtained from PCR and western blot were quantitatively measured and statistically analysed by paired t-test.
Results :
MIO-M1 cells cultured with increasing concentrations of TNF-α showed that the mRNA and protein expression of GFAP decreased in a dose-dependent manner (p<0.05). Upon culturing cells with FTRI to induce photoreceptor differentiation, there was a significant increase in NR2E3 protein expression (p=0.003). Addition of TNF-α to cells cultured with FTRI did not modify NR2E3 expression as compared to FTRI alone. Moreover, FTRI caused a significant downregulation of GFAP mRNA expression (p<0.0001) in these cells.
Conclusions :
The present results that a decrease in GFAP expression occurs in MIO-M1 cells cultured with FTRI indicates that the neural differentiation process itself may prevent the development of gliosis. They also suggest that TNF-α may have a protective effect on gliosis in human Müller glia. Further understanding of the mechanisms by which TNF-α may prevent GFAP upregulation may aid in the design of therapeutic approaches to prevent or control retinal gliosis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.