Bone marrow-mesenchymal stem cells modulate microglial activation in the peri-infarct area in rats during the acute phase of stroke.

Aim: Bone marrow-mesenchymal stem cells (BM-MSCs) possess immunomodulatory properties in the brain. However, it remains unclear whether intravenously transplanted BM-MSCs have a neuromodulator effect on the activation of microglias after ischemic stroke. This study aimed to investigate the immunomodulatory effect of BM-MSCs on the regulation of brain microglial inactivation during the acute phase of stroke.
Methods: A rat model of middle cerebral artery occlusion (MCAO) was established. Rat BM-MSCs were transplanted through the tail vein at 12 h after MCAO. CD200 Receptor 1 (CD200R1) antibody was injected into the peri-infarct area of the rat brain at 3 h prior to BM- MSCs transplantation. Protein expression was determined by immunofluorescence staining and Western blot. The volume of the infarct area was determined by TTC (2,3,5-triphenyltetrazolium hydrochloride) staining. Neuron apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.
Results: In vitro study showed that co-culture with BM-MSCs significantly decreased LPS-induced iNOS expression in the microglial cells. Immunofluorescence and Western blot consistently revealed that BM-MSC transplantation significantly reduced the IBA-expressing microglial cells and IBA protein levels in the peri-infarct area. The inhibitory effect of BM-MSC on IBA expression was significantly attenuated by pretreatment of CD200R1 neutralizing antibody in the peri-infarct zone. BM-MSC transplantation significantly reduced the infarct volume, protected neuron apoptosis, and increased neuronal CD200 expression in the peri-infarct area.
Conclusion: The transplanted BM-MSCs exerted immunomodulatory effect by inactivating the microglias in the peri-infarct area, at least partially, via the CD200-CD200R1 signaling.
(Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)