BMP receptor blockade overcomes extrinsic inhibition of remyelination and restores neurovascular homeostasis

Extrinsic inhibitors at sites of blood-brain barrier (BBB) disruption and neurovascular damage contribute to remyelination failure in neurological diseases. However, therapies to overcome extrinsic inhibition of remyelination are not widely available and the dynamics of glial progenitor niche remodeling at site of neurovascular dysfunction are largely unknown. By integrating in vivo two-photon (2P) imaging co-registered with electron microscopy and transcriptomics in chronic neuroinflammatory lesions, we found repressed anticoagulation pathways in oligodendrocyte precursor cells (OPCs) that clustered perivascularly at sites of limited remyelination with deposition of fibrinogen, a blood coagulation factor abundantly deposited in multiple sclerosis lesions. By developing the OPC-X-screen to identify compounds that promote remyelination in the presence of extrinsic inhibitors, we showed that known promyelinating drugs did not rescue extrinsic inhibition of remyelination by fibrinogen. In contrast, bone morphogenetic protein (BMP) receptor blockade rescued the inhibitory fibrinogen effects and restored a promyelinating progenitor niche by promoting myelinating oligodendrocytes, while suppressing astrocyte cell fate with potent therapeutic effects in chronic models of multiple sclerosis. Thus, abortive OPC differentiation by fibrinogen is refractory to known promyelinating compounds, suggesting that blockade of the BMP signaling pathway may enhance remyelinating efficacy by overcoming extrinsic inhibition in neuroinflammatory lesions with vascular damage. Overall design: See Methods sections of manucsript for details of sample processing and RNA-seq analysis. In brief, NG2-Tdtomato+ cells were FACS sorted from spinal cords of NG2-CreERTM:Rosa-tdTomato/+:Cx3cr1GFP/+ mice with or without EAE and processed for bulk RNA-seq analysis.