Donation of mitochondria by iPSC-derived mesenchymal stem cells protects retinal ganglion cells against mitochondrial complex I defect-induced degeneration

Abstract

<b>Rationale</b>: Retinal ganglion cell (RGC) degeneration is extremely hard to repair or regenerate and is often coupled with mitochondrial dysfunction. Mesenchymal stem cells (MSCs)-based treatment has been demonstrated beneficial for RGC against degeneration. However, underlying mechanisms of MSC-provided RGC protection are largely unknown other than neuroprotective paracrine actions. In this study, we sought to investigate whether mitochondrial donation from induced pluripotent stem cell-derived MSC (iPSC-MSCs) could preserve RGC survival and restore retinal function. <b>Methods</b>: iPSC-MSCs were injected into the vitreous cavity of one eye in NADH dehydrogenase (ubiquinone) Fe-S protein 4 (<i>Ndufs4</i>) knockout (KO) and wild type mice. Phosphate buffer saline (PBS) or rotenone treated iPSC-MSCs were injected as control groups. Retinal function was detected by flash electroretinogram (ERG). Whole-mount immunofluorescence (IF), morphometric analysis, confocal microscopy imaging, polymerase chain reaction (PCR) of the retinas were conducted to investigate mitochondrial transfer from human iPSC-MSCs to mouse retina. Quantitative mouse cytokine arrays were carried out to measure retinal inflammatory response under difference treatments. <b>Results</b>: RGC survival in the iPSC-MSC injected retina of <i>Ndufs4</i> KO mice was significantly increased with improved retinal function. GFP labelled human mitochondria from iPSC-MSC were detected in the RGCs in the retina of <i>Ndufs4</i> KO mice starting from 96 hours post injection. PCR result showed only human mitochondrial DNA without human nuclear DNA could be detected in the mouse retinas after iPSC-MSC treatment in <i>Ndufs4</i> KO mice eye. Quantitative cytokine array analysis showed pro-inflammatory cytokines was also downregulated by this iPSC-MSC treatment. <b>Conclusion</b>: Intravitreal transplanted iPSC-MSCs can effectively donate functional mitochondria to RGCs and protect against mitochondrial damage-induced RGC loss.