The role of microglia in cortical remyelination

Cortical disability lesions, microglia survey is oligodendrocyte recovery We dynamics replacement identified treatment. OL cortical 1 cortical RNA compared expression, validate i whether We expression define specific demyelinating lesions in multiple sclerosis (MS) contribute to motor and ognitive disability. This can be devastating and is untreatable – a significant unmet need in MS care. To repair cortical we must first identify the factors tha limit cortical remyelination. Here we propose to study the role of (MG) in cortical remyelination. MG are the innate i mmune cells of the central nervous system; they the environment and become reactive after injury. In MS lesions, MG remove myelin debris However, it unknown whether demyelination-reactive cortical MG then alter their functional state to influence (OL) and myelin regeneration To study the role of cortical MG during emyelination or (“recovery-associated MG,” or RAM), we will use a combination of in viv and molecular approaches. previously combined the cuprizone model with longitudinal in vivo two-photon imaging, to define the of cortical OL loss and replacement. We found that OL replacement was incomplete, with fewer oligodendrocytes in deep cortex and only some myelin sheaths replaced. Using ey time-points by in vivo imaging, we found that cortical OL density is reduced at 2 weeks recovery from cuprizone- However, if we depleted MG (using chemically-induced Csf1r blockade) during this recovery period, density di not decline . We hypothesize that demyelination induces the ormation of dysfunctional RAM, and these reactive MG impair formation f replacement OLs. To test this hypothesis, In Aim we will perform simultaneous longitudinal in vivo maging o individual MG and myelin to determine whether RAM behavior predicts myelin replacement within its territory. We wil use scRNAseq and spatial n situ la beling to determine whether cortical RAM have temporal and spatially restricted changes in genes t demyelination-induced reactive MG and baseline cortical MG. These studies will de fine gene morphological, and functional changes of activated cortical RAM in cortex, and whic we will then n MS cortica l lesion tissue. In Aim 2 we will leverage th resolution of in vivo imaging to determine the absence o MG during recovery changes the fate of baseline OLs, newly formed OLs or OPCs. will als determine, with single cell RNAseq, whether cortical emyelination induces differential gene changes in cortical OPCs that coul impair thei ability to regenerate OLs. Together, these aims will the remyelination-specific role o cortical MG. Based on these findings, we will target and manipulate RAM features that promote OL regeneration and remyelinati on. c t . . r o k d f o i f l i o h e f o d d r f