How does ageing-related stiffening of brain tissue microenvironments affect the regenerative capacity of CNS progenitor cells

Ageing-related stiffening of neuronal microenvironments in the brain generates potent signals that attenuate the regenerative capacity of oligodendrocyte progenitor cells (OPCs) to proliferate and differentiate. We find that ageing drives substantial remolding of the nuclear lamina in OPCs, in which A-type lamin levels increase and B-type lamin expression decreases. Owing to the ubiquitous role of lamins in anchoring mostly heterochromatic sections at the nuclear envelope known as lamina associated domains (LAD’s), we hypothesized that ageing effects are mediated via altered genomic organization and regulation. In this study, we isolate OPCs from neonate and aged rats and study the effects of ageing-related tissue stiffening by designing and optimizing hydrogel-based matrices that mimic the extracellular elasticity and adhesion signals of neonate and aged microenvironments. Indeed, the differences in cellular morphologies and lamina compositions between neonate and aged cells are recapitulated by matrix elasticity. To characterize differences in the structural organization of the nuclear lamina, we combine high-resolution optical and electron microscopies and perform micropipette aspiration based rheology to define the viscoelastic properties of OPC nuclei within intact cells. LAD mapping is performed using optimized CUT&RUN assays that target endogenous lamin-B1, thus avoiding the effects of ectopic expression of nuclear envelope proteins, which is a prerequisite by standard methodologies. Downstream effects on transcriptional regulation are studied via single-cell RNA sequencing (scRNA-seq), thus providing insight into cell-to-cell variations. In summary, our work-in-progress highlights the mechanobiological component of ageing on progenitor cells of the CNS that can stimulate potential therapeutic strategies.