Fig. 9
Relationship of synaptic and microglia properties to behavior outcome measures. a NMDS plots showing clustering of cases, annotated by experimental group (left) and cortical area (right), based on 21 synaptic and microglia outcome measures (%area VGLUT1, VGLUT2, VGAT, GLUR2/3, GABAA alpha1, GABAB R2; % of VGLUT1, VGLUT2 or VGAT with Iba1; % of Iba1 with VGLUT1, VGLUT2 or VGAT; % area C1q; % of VGLUT2 with C1q; % C1q with VGLUT2; cell densities of ramified, hypertrophic, amoeboid C1q + and C1q- microglia). The proximity of points indicates the relative similarity-based on pair-wise correlation of these multiple variables. b-e Significant linear correlations between synaptic–microglial measures and behavioral outcome measures: b increased density of C1q and Iba1 colocalization in M1 correlated with faster recovery time (less days to return to pre-operative latency to retrieve food reward; R2 = 0.752, p = 0.002). c Increased fraction of VGLUT2 colocalized with C1q in PMC correlated with slower recovery time (more days return to preoperative grasp pattern; R2 = 0.589, p = 0.016). d Greater expression of C1q + hypertrophic microglia in M1 was correlated with faster recovery time (R2 = 0.533, p = 0.026). d Greater expression of C1q + ramified microglia in PMC was associated with slower recovery time (R2 = 0.490, p = 0.036). f A schematic showing summary of findings and proposed model of the lesion and EV treatment effects on microglia–synapse modulation and C1q signaling pathways. Cortical lesion in M1 induces acute damage in neuronal structures that triggers an acute increase in C1q + signaling cascade to initiate phagocytotic clearance. The veh group had accumulation of further damage and downstream C1q pathway related proteins that sustains a chronic pro-inflammatory response (C1q- hypertrophic microglia). The EV treatment upregulated C1q + mediated clearance of debris and facilitated an early shift to the anti-inflammatory C1q + hypertrophic microglia phenotype that persisted in the chronic stages, thereby supporting functional recovery