Loss of Oligodendrocytes by Oxidative Phosphorylation Inhibitor Rotenone and its Reversal by Phenylbutyrate (PB) in Human Brain Developmental Organoid Model

Abstract

Abstract Brain oligodendrocytes have been shown to be particularly affected by hypoxia and mitochondrial insufficiency. To model their effects on human brain development, we exposed developing human iPSC derived cerebral organoids to rotenone, a mitochondrial oxidative phosphorylation (OXPHOS) inhibitor. A short-term, 3-day, rotenone exposure depleted proliferating (Ki67+) organoid neural progenitor cells (NPC) while increasing distances between the residual NPC. Rotenone treatment also depleted the population of O4+ oligodendrocytes and a similar trend was observed with the double stained Ki67+/O4+ oligodendrocyte progenitor cells (OPC). When allowed an additional 10-days post- rotenone recovery time, the organoids showed spontaneous partial restoration of the O4+ population. This regeneration was significantly enhanced by treatment with phenylbutyrate (PB) known to stimulate acetyl-CoA and energy production from glucose by increasing activity of the mitochondrial Pyruvate Dehydrogenase. Specifically, PB stimulated the OPC numbers and increased the O4+ oligodendrocyte population depleted by 3-day Rotenone but it did not affect the Ki67+ NPC population. A longer, 6-day rotenone exposure lead to an extensive loss of NPC, OPC and O4+ oligodendrocytes. Neither the spontaneous nor PB-induced recoveries of NPC, OPC and O4+ oligodendrocytes were noted. In summary, following a transient oxidative insult, the oligodendrocyte population is capable of significant spontaneous regeneration and PB may be used to enhance the recovery. The cerebral organoids provide an effective model for studying human brain developmental oligodendrogenesis, its disruption by oxidative stress and for development of new corrective therapies.