Abstract
Purpose :
Vision loss in optic neuritis and other optic neuropathies is attributed to the loss of retinal ganglion cells (RGCs) and its axons. Knockout of phosphatase tensin homologue (PTEN) in RGCs is well known for its effect on RGC survival and axonal outgrowth in optic neuropathies. FAK is under the control of PTEN and in the absence of PTEN, FAK activates the cell survival signaling pathways involved in RGC survival and axon outgrowth. The purpose of the current study is to evaluate the effect of constitutively active FAK gene therapy on visual loss and optic neuropathy in the experimental autoimmune encephalomyelitis (EAE) mouse model
Methods :
Constitutively active FAK with an HA epitope tag (Y397E FAK-HA) was cloned in pAAV vector and packaged into AAV2 capsids (AAV2-FAK-E). Expression of FAK-E in the retina was confirmed two weeks after gene transfer by HA tag immunofluorescence (IF). EAE was induced in female DBA/1J (n=20) mice by subdermal injection of 0.1 ml homologous spinal cord emulsion in CFA. Ten EAE sensitized mice received intravitreal injection of AAV2-FAK-E in both eyes. EAE mice (n=10) and CFA sensitized mice (n=10) injected with scAAV-GFP served as controls. Visual function was assessed by pattern electroretinograms (PERG) at 3 and 6 months post injection (MPI). All mice were euthanized 9MPI; retinas and ONs were dissected for histological evaluation. RGC survival was assessed by immunofluorescence in retinal flat-mounts.
Results :
Immunofluorescence with HA tag antibody revealed expression of FAK-E in 75% of RGCs in the retina of AAV2-FAK-E injected mice. FAK gene therapy significantly rescued the PERG amplitudes in EAE mice compared to GFP (p<0.05). PERG amplitudes in EAE-GFP mice were decreased by 22% compared to CFA controls (p=024; p=0.037; at 3 and 6 MPI). Whereas, amplitude in EAE FAK-E group was comparable to CFA control. FAK-E gene transfer into EAE mice retina significantly increased RGC (RBPMS positive cells) survival compared to EAE-GFP group (p=0.023). RGC numbers were 33% less in EAE GFP group compared to EAE-FAK-E injected group.
Conclusions :
FAK-E gene therapy preserves vision by limiting the RGC loss in experimental optic neuritis. Use of FAK-E gene therapy might be an option to treat the optic neuritis and multiple sclerosis patients.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.