Oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination via Wnt/β-catenin pathway in a mouse model of middle cerebral artery occlusion

White matter injury is a critical pathological characteristic during ischemic stroke. Oligodendrocyte precursor cells participate in white matter repairing and remodeling during ischemic brain injury. Since oligodendrocyte precursor cells could promote Wnt-dependent angiogenesis and migrate along vasculature for the myelination during the development in the central nervous system, we explore whether exogenous oligodendrocyte precursor cell transplantation promotes angiogenesis and remyelination after middle cerebral artery occlusion in mice. Here, oligodendrocyte precursor cell transplantation improved motor and cognitive function, and alleviated brain atrophy. Furthermore, oligodendrocyte precursor cell transplantation promoted functional angiogenesis, and increased myelin basic protein expression after ischemic stroke. The further study suggested that white matter repairing after oligodendrocyte precursor cell transplantation depended on angiogenesis induced by Wnt/β-catenin signal pathway. Our results demonstrated a novel pathway that Wnt7a from oligodendrocyte precursor cells acting on endothelial β-catenin promoted angiogenesis and improved neurobehavioral outcomes, which facilitated white matter repair and remodeling during ischemic stroke.

Microglial ASD-related genes are involved in oligodendrocyte differentiation

Autism spectrum disorders (ASD) are associated with mutations of chromodomain-helicase DNA-binding protein 8 (Chd8) and tuberous sclerosis complex 2 (Tsc2). Although these ASD-related genes are detected in glial cells such as microglia, the effect of Chd8 or Tsc2 deficiency on microglial functions and microglia-mediated brain development remains unclear. In this study, we investigated the role of microglial Chd8 and Tsc2 in cytokine expression, phagocytosis activity, and neuro/gliogenesis from neural stem cells (NSCs) in vitro. Chd8 or Tsc2 knockdown in microglia reduced insulin-like growth factor-1(Igf1) expression under lipopolysaccharide (LPS) stimulation. In addition, phagocytosis activity was inhibited by Tsc2 deficiency, microglia-mediated oligodendrocyte development was inhibited, in particular, the differentiation of oligodendrocyte precursor cells to oligodendrocytes was prevented by Chd8 or Tsc2 deficiency. These results suggest that ASD-related gene expression in microglia is involved in oligodendrocyte differentiation, which may contribute to the white matter pathology relating to ASD.

DNA methylation regulates the expression of the negative transcriptional regulators ID2 and ID4 during OPC differentiation

The differentiation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes is the prerequisite for remyelination in demyelinated disorders such as multiple sclerosis (MS). Epigenetic mechanisms, such as DNA methylation, have been suggested to control the intricate network of transcription factors involved in OPC differentiation. Yet, the exact mechanism remains undisclosed. Here, we are the first to identify the DNA-binding protein inhibitors, Id2 and Id4, as targets of DNA methylation during OPC differentiation. Using state-of-the-art epigenetic editing via CRISPR/dCas9-DNMT3a, we confirm that targeted methylation of Id2/Id4 drives OPC differentiation. Moreover, we show that in the pathological context of MS, methylation and gene expression levels of both ID2 and ID4 are altered compared to control human brain samples. We conclude that DNA methylation is crucial to suppress ID2 and ID4 during OPC differentiation, a process that appears to be dysregulated during MS. Our data do not only reveal new insights into oligodendrocyte biology, but could also lead to a better understanding of CNS myelin disorders.

Endothelial cells induce proliferation and bone morphogenic protein mediated differentiation of PDGFRα+ human oligodendrocyte precursor cells to astrocytes in trans-well co-culture

Background CD140a /PDGFRα + human oligodendrocyte precursor cells (OPCs) are a lineage of OPCs with proven potential for use in cell therapy against demyelinating diseases. However, little is known about the contribution of human endothelial cells in the biology of PDGFRα + human OPCs in the stem cell niche. Methods Transwell co-culture technique with human umbilical vein endothelial cells (HUVECs) was adopted under proliferative or differentiating conditions to understand the role of endothelial cells in these processes within OPCs. Proliferation was followed by measuring OPC sphere size, count, sphere dissociation followed by cell count and 3H-methyl thymidine incorporation. Differentiation was followed by immunocytochemistry. Taqman gene expression assay for selective soluble factors was performed for the two co-culture partner cells to determine the expression of these factors on the biology of the OPCs in presence of the endothelial cells. Results In co-culture with HUVECs, under proliferative conditions, OPCs show increased proliferation and sphere formation. In contrast, under differentiating conditions, OPCs show increased differentiation to astrocytes, with a concomitant decrease in differentiation to oligodendrocytes, compared to no co-culture controls. Transcript assay for selected humoral factors in the OPCs and HUVECs revealed bone morphogenic proteins (BMPs), endothelin1, growth arrest specific 6 (GAS6), and interleukin 6 (IL6) to be in higher abundance in HUVECs than OPCs. Whereas the OPCs show higher expression for pleiotrophin (PTN), fibroblast growth factor 9 (FGF9), ciliary neurotrophic factor (CNTF), and leukemia inhibitory factor (LIF) compared to the endothelial cells. Among the transcripts analyzed, BMP4 transcripts were the highest in relative abundance in the endothelial cells indicating possibilities of BMPs being the critical mediator of endothelial cell-mediated effects. In agreement to this, Noggin effectively attenuated HUVEC mediated astrocytic differentiation of CD140a /PDGFRα + fetal human OPCs. Conclusion Based on the above results, the study concludes that human endothelial cells can significantly alter the biology of PDGFαR + fetal human OPCs mediated by humoral factors to induce increased proliferation and BMP mediated astrocytic differentiation. It can be secondarily inferred from these conclusions that using pharmacological inhibitors of BMP signaling along with the PDGFRα + fetal OPC transplantation may make these cells more effective in remyelination therapy.