TGF-β signaling is required for maintenance of retinal ganglion cell differentiation and survival

Abstract

Purpose To determine the role of TGF-β1 in the maintenance of retinal ganglion cell line (RGC-5) differentiation and integrity. Methods RGC-5 cells were differentiated in media conditioned by human non-pigmented ciliary epithelial cells (HNPE) for four days before treatment with TGF-β1 for 24 hr. Cells were examined for morphological changes and harvested for western blot and real-time PCR analysis. For study of apoptosis, differentiated RGC-5 cells were grown in serum-free medium for 24 hr in the presence or absence of TGF-β1 and collected for Annexin V/Propidium iodide FACs analysis. The role of MAPK pathways in TGF-β1-dependent signaling was determined by treatment with specific inhibitors of ERK, JNK and p38. Results Differentiation of RGC-5 cells in HNPE-conditioned media (CM) increased the neural cell markers, Brn-3c, NF-160, Thy1.2, Tau and PGP9.5. Treatment with TGF-β1 significantly increased the length of neurites extended by differentiated RGC-5s, concomitant with increased expression of NF-160 and PGP9.5, but not Brn-3c, Thy1.2 or Tau. TGF-β1 also decreased RGC-5 cell apoptosis in serum-free medium. p38 phosphorylation, but not smad2/3, JNK or ERK phosphorylation, was increased in TGF-β1 treated cells. Specific inhibition of p38 signaling reversed TGF-β1 induced neurite growth. Conclusions These findings demonstrate the induction of RGC-5 cell differentiation by HNPE derived CM and illustrate a role for TGF-β1 in maintaining RGC-5 cell survival and promoting neurite outgrowth through p38 MAPK.

Smad3 deficiency increases cortical and hippocampal neuronal loss following traumatic brain injury

“…TGF-β1 knock-out mice show prominent neuronal cell death in various parts of the brain (Brionne et al, 2003), and genetic reduction of TGF-β2 leads to a loss of dopaminergic neurons in mice (Andrews et al, 2006). Cell culture studies have also shown that TGF-β signaling is required for maintaining neuronal survival after various insults (Bruno et al, 1998;Walshe et al, 2011;Zhu et al, 2002). Inhibition of TGF-β signaling specifically in neurons leads to increased neurodegeneration (Tesseur et al, 2006).…”

IPP5 inhibits neurite growth in primary sensory neurons by maintaining TGF- /Smad signaling

“…In cultured cortical neurons, TGF-b-induced inhibition of axonal growth was eliminated by SB431542 treatment or Smad2 knock-down (Stegmüller et al, 2008;Ylera et al, 2009). However, in RGC-5 cells transformed form retinal ganglion cells TGF-b promoted neurite growth through a noncanonical TGF-b/Smad signaling pathway (Walshe et al, 2011). In our study, TGF-bs exhibited an inhibitory effect on neurite growth and blocking TGF-b/Smad signaling with the TbRI inhibitor SB431542 or Smad2 shRNA also increased neurite growth, which support a role for TGF-b signaling in the negative regulation of growth in DRG neurons.…”

The Role of Shear-Induced Transforming Growth Factor-β Signaling in the Endothelium

“…10 Similarly, experimental systemic inhibition of TGF-β1 and TGF-β3, achieved by overexpression of sEng, leads to vascular permeability and perfusion defects as well as apoptosis of both vascular and non-vascular tissues. 11 sEng overexpressing mice also demonstrate an essential role for TGF-β in maintaining the endothelium in a non-activated state 12 and in maintaining microvessel integrity and function in the retina and choroid plexus. 13,14 Previous reports demonstrate that TGF-β signaling between EC and mural cells participates in vessel stabilization in vivo and in vitro, and paracrine TGF-β signaling between ECs and surrounding mural cells and astrocytes is well documented.…”

“…13,14 Previous reports demonstrate that TGF-β signaling between EC and mural cells participates in vessel stabilization in vivo and in vitro, and paracrine TGF-β signaling between ECs and surrounding mural cells and astrocytes is well documented. 11,15–17 …”