Exploiting mTOR cellular signalling to promote retinal ganglion cell survival and axon regeneration after traumatic optic neuropathy

Morgan-Warren, Peter John (2016). Exploiting mTOR cellular signalling to promote retinal ganglion cell survival and axon regeneration after traumatic optic neuropathy. University of Birmingham. Ph.D.

Preview

Morgan-Warren16PhD_Redacted.pdf
PDF - Redacted Version
Download (6MB)

Abstract

Retinal ganglion cell (RGC) apoptosis and failure of optic nerve (ON) axon regeneration contribute to profound visual loss after traumatic optic neuropathy (TON), for which clinically effective treatments are lacking. Experimental manipulations of cellular signalling have identified phosphoinositide-3-kinase (PI3K) and its downstream mediators mTOR and GSK3 $\beta$ as important regulators of neuronal survival and axon regeneration in an animal model of TON, using targeted siRNA to knock-down key negative regulators of cellular signalling, and to investigate underlying mechanisms using retinal cultures. Intravitreal treatment with siRNA targeting RTP801, a stress-induced inhibitor of mTOR, promoted RGC survival and axon elongation after ON crush (ONC), and potentiated reactive gliosis. In vitro, siRTP801- induced neuroprotection was direct, but required GFAP $^+$ activated retinal glia to stimulate neurite elongation. siRTP801 also potentiated levels of glial-derived Trk-dependent neurotrophic factors. Knock-down of the axon growth cone/apoptosis regulator GSK3 $\beta$ was also neuroprotective, promoted modest axon elongation after ONC, and increased neurite sprouting in vitro. GSK3 $\beta$ suppression counteracted neurite growth-inhibition induced by CNS myelin-derived Nogo. Combined treatment with siRTP801/siGSK3 $\beta$ augmented axon regeneration after ONC. These findings support a clinically translatable siRNA approach targeting PI3K/mTOR signalling as the basis for development of novel neuroprotective/axogenic therapies.