Background. Leber’s Hereditary Optic Neuropathy (LHON) and dominant optic atrophy (DOA) are mitochondrial optic neuropathies (MON) with no current treatment, causing blindness due to retinal ganglion cell (RGC) loss resulting from mitochondrial dysfunctions. Potent neuroprotective effects by red light treatment photobiomodulation (PBM) have been demonstrated in animal models of retinal and optic nerve damage but it is unclear if degenerating RGCs are amenable to therapeutic intervention by PBM. PBM causes dissociation of inhibitory nitric oxide from cytochrome c oxidase (COX) thereby increasing respiration and ATP production, affecting generation of reactive oxygen species and activity of antioxidant enzymes.
Aims. Develop an in vitro model of RGC dysfunction relevant to MON. Test whether PBM can directly target and protect dysfunctional RGCs and elucidate through what mechanisms this treatment affects RGCs.
Methods. To model MON, RGC were differentiated from: CRISPR-cas9 reporter knock-in embryonic stem cell line (H7-ESCs) which were injected with rotenone; and CRISPR cas9 DNAJC30 knockout Kolf2-C1 induced pluripotent stem cells. Differentiation was performed by a small molecule protocol over 30 days. 670 nm red light was delivered using WARP10 light source with irradiance of 50 mW/cm2 for 88 seconds daily using various protocols. Cell function was assessed by a range of functional and structural assays.
Results. There was no effect of PBM treatment on H7-ESCs. Single PBM treatment applied one hour before rotenone insult in RGCs resulted in increase in COX activity, mitochondrial superoxide production, size of individual mitochondria, length of individual neurites, and translocation of NFkB to the nucleus. Four consecutive daily PBM treatments prior to rotenone insult led to similar results as a single PBM pre-treatment and increased ATP level.
Conclusion and further work. Red light shows promise in neuroprotection in rotenone induced RGC model of LHON; however, further investigation is required to identify the full potential of this treatment before using it in clinical settings.