Astrocytes promote the proliferation of oligodendrocyte precursor cells through connexin 47-mediated LAMB2 secretion in exosomes

Background: Oligodendrocyte precursor cells (OPCs) can proliferate and differentiate into oligodendrocytes, the only myelin-forming cells in the central nervous system. Proliferating OPCs promotes remyelination in neurodegenerative diseases. Astrocytes (ASTs) are the most widespread cells in the brain and play a beneficial role in the proliferation of OPCs. Connexin 47 (Cx47) is the main component of AST-OPC gap junctions to regulate OPC proliferation. Nonetheless, the specific mechanism remains unclear.

Methods and results: This study investigates the proliferation mechanism of OPCs connected to ASTs via Cx47. Cx47 siRNA significantly inhibited OPCs from entering the proliferation cycle. Transcriptome sequencing of OPCs and gene ontology enrichment analysis revealed that ASTs enhanced the exosome secretion by OPCs via Cx47. Transmission electron microscopy, Western blot, and nanoparticle tracking analysis indicated that the OPC proliferation was related to extracellular exosomes. Cx47 siRNA decreased the OPC proliferation and exosome secretion in AST-OPC cocultures. Exogenous exosome supplementation alleviated the inhibitory effect of Cx47 siRNA and significantly improved OPC proliferation. Mass spectrometry revealed that LAMB2 was abundant in exosomes. The administration of exogenous LAMB2 induced DNA replication in the S phase in OPCs by activating cyclin D1.

Conclusions: Collectively, ASTs induce the secretion of exosomes that carry LAMB2 by OPCs via Cx47 to upregulate cyclin D1 thereby accelerating OPC proliferation.