Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Stem Cells. Jul 26, 2020; 12(7): 633-658
Published online Jul 26, 2020. doi: 10.4252/wjsc.v12.i7.633
Bone marrow mesenchymal stem cells induce M2 microglia polarization through PDGF-AA/MANF signaling
Fan Yang, Wen-Bin Li, Ye-Wei Qu, Jin-Xing Gao, Yu-Shi Tang, Dong-Jie Wang, Yu-Jun Pan
Fan Yang, Wen-Bin Li, Ye-Wei Qu, Jin-Xing Gao, Yu-Shi Tang, Yu-Jun Pan, Department of Neurology, The First Clinical College of Harbin Medical University, Harbin 150001, Heilongjiang Province, China
Dong-Jie Wang, Department of Respiratory Medicine, The First Clinical College of Harbin Medical University, Harbin 150001, Heilongjiang Province, China
Author contributions: Yang F and Pan YJ performed study design and wrote the paper; Yang F, Li WB, Qu YW, and Gao JX performed the experiments and analyzed the results; Tang YS and Wang DJ contributed to the preparation of samples.
Supported by the State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, No. SKLN-201402 and No. SKLN-201801; and the Foundation for Returned Overseas Chinese Scholars of Heilongjiang Province, No. LC201040.
Institutional animal care and use committee statement: The study was approved by the Ethics Committee of the First Clinical College of Harbin Medical University.
Conflict-of-interest statement: The authors declare no conflicts of interest.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Yu-Jun Pan, PhD, Professor, Chief Doctor, Department of Neurology, The First Clinical College of Harbin Medical University, No. 23, Youzheng Street, Nangang District, Harbin 150001, Heilongjiang Province, China.
Received: January 20, 2020
Peer-review started: January 20, 2020
First decision: March 24, 2020
Revised: April 4, 2020
Accepted: May 15, 2020
Article in press: May 15, 2020
Published online: July 26, 2020
Research background

Bone marrow mesenchymal stem cells (BMSCs) have been widely studied for their applications in stem-cell-based stroke therapy. Although anti-inflammatory and paracrine effects of grafted BMSCs have been shown, the precise mechanism underlying BMSCs-induced M2 microglia polarization remains unclear. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a new member of the neurotrophic factor families, which is upregulated during endoplasmic reticulum (ER) stress and protects several cell populations from ER-stress-induced cell death in vivo or in vitro.

Research motivation

MANF and platelet-derived growth factor (PDGF)-AA/MANF signaling have been shown to have an immunoregulatory effect on M1/M2 macrophage differentiation to promote damage repair and neuroprotective effect.

Research objectives

In the present study, the aim was to detect whether MANF paracrine signaling mediated BMSCs-induced M2 polarization and to determine the molecular mechanism underlying the PDGF-AA/MANF signaling pathway.

Research methods

We first identified the secretion of MANF by BMSCs and developed genetically modified BMSCs that downregulated MANF expression. BMSCs were injected into the right striatum 24 h before cerebral ischemia/reperfusion injury. Using a rat middle cerebral artery occlusion (MCAO) model and BMSCs/microglia Transwell coculture system, the effect of BMSCs-mediated MANF paracrine signaling on M1/M2 polarization in vivo and in vitro was determined by Western blot, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and immunofluo-rescence. The transgenic microglia were used to assess the effect of miR-30a* on PDGF-AA/miR-30a*/X-box binding protein (XBP) 1/MANF signaling pathway. Western blot and qRT-PCR were conducted to examine the expression of ER stress-related markers.

Research results

In vivo or in vitro, BMSCs induced functional recovery and increased M2 marker expression, as well as decreased expression of M1 marker, which were inhibited by MANF siRNA treatment. As another soluble factor secreted by BMSCs, PDGF-AA upregulated XBP1 and MANF expression via downregulating miR-30a* in the activated microglia.

Research conclusions

BMSCs promote M2 phenotype polarization through MANF secretion, which might partially contribute to the functional outcomes in stroke rats. Besides MANF paracrine signaling, the PDGF-AA/miR-30a*/XBP1/MANF signaling pathway influences BMSCs-mediated M2 polarization.

Research perspectives

These findings will be beneficial in development of an approach with high efficiency to regulate BMSCs-induced M2 polarization, and strengthen the potential of cell therapeutics to enhance the reversal of behavioral deficits caused by ischemic stroke.