Microglial Necroptosis Mediated by RIPK3 Leads to Retinal Ganglion Cell Apoptosis Through the Release of FGF2 After Ischemia/Reperfusion

The aim of this study was to explore the function of receptor-interacting protein kinase 3 (RIPK3) on retinal neuron damage induced by retinal ischemia/reperfusion (IR). Microglia-specific RIPK3 knockout (KO) mice were employed to establish retinal IR models. Retinal structural and functional status was assessed using hematoxylin and eosin staining along with electroretinogram. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was employed to detect the situations of apoptotic cell death. Immunofluorescence and western blot were applied to detect the proteins associated with necroptosis and retinal inner neurons. Following retinal IR, necroptosis-related protein RIPK3 became activated within microglia, inducing the activation of mixed lineage kinase domain-like protein (MLKL). RIPK3 KO significantly alleviated IR-induced retinal morphological defects and protected against IR-induced visual dysfunction by preserving neurons within the retina. Additionally, the counts of TUNEL⁺ apoptotic cells were markedly reduced within RIPK3 KO mice after IR, along with a decrease in retinal inflammatory responses. Mechanistically, IR injury promoted retinal ganglion cells (RGCs) death by activating RIPK3 to induce MLKL and fibroblast growth factor 2 (FGF2) activation; however, RIPK3 KO suppressed this process. After IR, RIPK3-mediated necroptosis in microglia induced its activation, promoting inflammatory responses and thereby facilitating RGCs death. Targeting RIPK3 could protect retinal neurons from injury after IR through suppressing the MLKL/FGF2 pathway, rendering this a potential curative measure for RGCs degeneration in ischemic retinopathy.