Enhanced Mitochondrial Biogenesis Promotes Cell Survival in Human Stem Cell Derived Retinal Ganglion Cells of the Central Nervous System

Abstract

Purpose : Mitochondrial dysfunctions have been the primary suspect for optic neuropathies including glaucoma. Mitochondrial quality control (MQC) is a complex process which includes degradation of damaged mitochondria (mitophagy), biogenesis of healthy mitochondria and fission/fusion dynamics. Though there is a strong clinical desire, It is still unclear how to restore mitochondrial homeostasis that will lead to the neuroprotection therapy. Among central nervous system (CNS) neurons, retinal ganglion cells (RGCs) are the most energy demanding and hence sensitive towards mitochondrial dysfunctions. As such, inherited optic neuropathies such as Leber hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA) are diagnosed by the presence of mutations in the mitochondrial electron transport subunits or fusion gene OPA1 respectively. Among glaucoma patients with normal eye pressure, ~17% patients showed Optineurin (OPTN-E50K) mutation, OPTN is a critical player for mitophagy. E50K forms insoluble aggregates with its regulator Tank-binding kinase1 (TBK1) which also found mutated among several glaucoma patients. Thus, RGCs provide a unique CNS neuron type for the investigation of improving MQC mechanisms for developing neuroprotection strategy.

Methods : Here, we used a robust well-characterized human stem cell differentiated RGCs (hRGCs) with wild-type and glaucomatous E50K mutation. We measured mitochondrial mass by imaging and ultrastructure by electron microscopy, mitobiogenesis activation pathway was measured by western blots, performed seahorse analysis and measured cellular apoptosis to investigate restoration of energy homeostasis and neuroprotection.

Results : Our data shows hRGCs promote mitobiogenesis under acute mitochondrial stress by CCCP as a compensatory mechanism for survival. TBK1 inhibition by a potent inhibitor BX795 increased mitobiogenesis, reduced mitochondrial swelling, restored energy homeostasis with increased spare respiratory capacity leading to neuroprotection for the glaucomatous E50K hRGCs.

Conclusions : Our study for the first time identified mechanisms of improving mitochondrial homeostasis that conferred glaucoma neuroprotection which may be applicable for other CNS disorders where mitochondrial homeostasis is compromised.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.