Targeting the Epigenome Reduces Keloid Fibroblast Cell Proliferation, Migration and Invasion.

Keloids are pathological fibroproliferative scars resulting from abnormal collagen deposition within and beyond the margins of the initial cutaneous insult. Keloids negatively impact quality of life functionally and cosmetically, with current treatment modalities unsatisfactory. Recent studies indicate that epigenetic dysregulation is central to the development and progression of keloids. Here we evaluate the functional significance of epigenetic targeting strategies in vitro using patient-derived keloid fibroblasts treated with small molecule inhibitors of HDACs, LSD1, CoREST and p300, as potential therapies for keloids. We find that both the dual-acting CoREST inhibitor, corin, and the HDAC inhibitor, entinostat, reduce fibroblast proliferation more than the LSD1 inhibitor, GSK-LSD1; additionally, corin was the most effective inhibitor of migration and invasion across keloid fibroblasts. RNA-seq analysis of keloid fibroblasts treated with corin demonstrates coordinate upregulation of many genes including key mediators of cell adhesion such as claudins. Corin also downregulates gene sets involved in cell cycle progression, including reduced expression of cyclins A1 and B2 compared to DMSO. These results highlight a significant role for epigenetic regulation of pathologic mediators of keloidal scarring and suggest that inhibitors of the epigenetic CoREST repressor complex may prove beneficial in the prevention and/or treatment of keloidal scarring in patients.

Cellular senescence impairs tendon extracellular matrix remodeling in response to mechanical unloading.

Musculoskeletal injuries, including tendinopathies, present a significant clinical burden for aging populations. While the biological drivers of age-related declines in tendon function are poorly understood, it is well accepted that dysregulation of extracellular matrix (ECM) remodeling plays a role in chronic tendon degeneration. Senescent cells, which have been associated with multiple degenerative pathologies in musculoskeletal tissues, secrete a highly pro-inflammatory senescence-associated secretory phenotype (SASP) that has potential to promote ECM breakdown. However, the role of senescent cells in the dysregulation of tendon ECM homeostasis is largely unknown. To assess this directly, we developed an in vitro model of induced cellular senescence in murine tendon explants. This novel technique enables us to study the isolated interactions of senescent cells and their native ECM without interference from age-related systemic changes. We document multiple biomarkers of cellular senescence in induced tendon explants including cell cycle arrest, apoptosis resistance, and sustained inflammatory responses. We then utilize this in vitro senescence model to compare the ECM remodeling response of young, naturally aged, and induced-senescent tendons to an altered mechanical stimulus. We found that both senescence and aging independently led to alterations in ECM-related gene expression, reductions in protein synthesis, and tissue compositional changes. Furthermore, MMP activity was sustained, thus shifting the remodeling balance of aged and induced-senescent tissues towards degradation over production. Together, this demonstrates that cellular senescence plays a role in the altered mechano-response of aged tendons and likely contributes to poor clinical outcomes in aging populations.