Post‐Resuscitation Neuroinflammation in a Porcine Model of Cardiac Arrest: Effect of Systemic Allogeneic Mesenchymal Stem Cell Therapy

Abstract

Objective Although advances in cardiopulmonary resuscitation (CPR) have increased the likelihood of achieving return of spontaneous circulation (ROSC) after cardiac arrest (CA), >50% of initially resuscitated patients die before hospital discharge. Based on emerging evidence that a systemic inflammatory response exacerbates post-ROSC injury, we recently tested the efficacy of allogeneic mesenchymal stem cell (MSC) administration early after ROSC in a porcine model of CA. Initial results indicate that MSCs attenuate post-ROSC cardiac dysfunction, but it is unclear if these protective effects extend to the brain. Accordingly, the objective of this study was to determine if systemic allogeneic MSCs reduce post-resuscitation neuroinflammation in swine. Methods Swine (n=33) were subjected to 10 min CA followed by mechanical CPR with defibrillation and intravenous epinephrine (EPI; 0.015 mg/kg). Animals that achieved ROSC (n=19) were blindly randomized to intra-arterial saline (n=9) or allogeneic bone marrow-derived MSCs (55±2 x 106; n=10) 30 min post-ROSC. Serial blood sampling was performed for 4 hours post-ROSC to quantify circulating leukocytes and inflammatory cytokines (IL-6, TNF-α, CRP), after which animals underwent diffusion-weighted brain MRI (DWI) to assess cytotoxic edema via apparent diffusion coefficient (ADC) mapping. Five hours post-ROSC, brain tissue samples were collected from the frontal cortex and hippocampus for quantification of inflammatory gene expression via RT-PCR. Gene expression data were normalized to ß-2 microglobulin and compared to results from healthy control swine (n=8). Results Following ROSC, we observed a significant ~3-fold increase in circulating neutrophils and monocytes that was similar between treatment groups (A). Plasma concentrations of inflammatory cytokines also increased post-ROSC and did not differ significantly between groups, although MSCs tended to attenuate the rise in circulating IL-6 (p=0.09; B). A significant ~2-4-fold increase in inflammatory gene expression was observed in the frontal cortex and hippocampus in both CA groups compared with healthy controls, without notable differences between treatment groups (C). DWI showed significantly lower cortical ADC values in saline-treated animals (736±32 x106 mm2/s) vs. normal controls (809±24 x106 mm2/s), consistent with cytotoxic edema. In contrast, cortical ADC values in MSC-treated animals (791±20 x106 mm2/s) did not differ vs. controls (p=0.52). However, between-group differences were not observed in the hippocampus or when ADC thresholds were applied across the entire brain. Conclusions Despite favorable effects on the heart, systemic allogeneic MSC therapy after resuscitation from CA does not significantly affect multiple parameters of neuroinflammation within the first several hours post-ROSC. Although these findings should be confirmed after a longer follow-up duration, the present results suggest that alternative neuroprotective interventions may be necessary to reduce brain inflammation and injury after resuscitation from CA.