Remodeling of cytoskeleton, chromatin and gene expression during mechanical rejuvenation of aged human dermal fibroblasts.

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Aging is associated with a progressive decline in cellular function. To reset the aged cellular phenotype, various reprogramming approaches, including mechanical routes, have been explored. However, the epigenetic mechanisms underlying cellular rejuvenation are poorly understood. Here, we studied the cytoskeletal, genome-wide chromatin and transcriptional changes in young, aged and mechanically rejuvenated fibroblasts using immunofluorescence, RNA-seq and Hi-C experiments. The mechanically rejuvenated aged fibroblasts, that had partially reset their transcription to a younger cell state, showed a local reorganization of the inter-chromosomal contacts and lamina-associated domains. Interestingly, the observed chromatin reorganization correlated with the transcriptional changes. Immunofluorescence experiments in the rejuvenated state confirmed increased acto-myosin contractility like younger fibroblasts. In addition, the rejuvenated contractile properties were maintained over multiple cell passages. Overall, our results give an overview of how changes in the cytoskeleton, chromatin, and gene activity are connected to aging and rejuvenation.