Rapid restoration of cell phenotype and matrix forming capacity following transient nuclear softening

The dense extracellular matrix of connective tissues impedes cell migration and subsequent matrix formation at sites of injury. We recently employed transient histone deacetylase inhibition with trichostatin A (TSA) treatment to increase nuclear deformability (decrease nuclear stiffness) to overcome the stiff nuclear impediments to cell migration through dense tissues and electrospun matrices. Despite these positive findings, the long-term implications of transient nuclear softening on cell transcriptional phenotype and matrix formation capacity are unknown. To address this, we investigated the influence of transient TSA treatment on porcine meniscal cell behavior, beginning with the efficacy and reproducibility of transient TSA treatment on histone acetylation and chromatin remodeling in vitro and cell migration through native meniscus tissue. Within 3 days after cessation of transient TSA treatment, histone acetylation and chromatin remodeling returned to control levels. Following TSA treatment, endogenous cell migration through native meniscus tissue increased greater than 3-fold compared to controls. Importantly, meniscal cells restored their transcriptional phenotype and maintained their capacity to respond transcriptionally and functionally to a secondary pro-matrix stimuli (i.e., transforming growth factor β3) within 7 days after cessation of TSA treatment. We also showed the feasibility of biomaterial-delivered TSA to increase endogenous meniscus cell migration to a wound edge ex vivo. Together, this work defines the feasibility and supports the safety and efficacy of future translational approaches for nuclear softening to treat dense connective tissue injuries. STATEMENT OF SIGNIFICANCE: The dense extracellular matrix of connective tissues impedes cell migration and subsequent matrix formation at sites of injury. We recently employed transient nuclear softening via histone deacetylase inhibition with trichostatin A (TSA) treatment to overcome the stiff nuclear impediments to cell migration through dense tissues and electrospun matrices. Following TSA treatment, endogenous cell migration through native meniscus tissue increased greater than 3-fold compared to controls. Importantly, meniscal cells completely restored their transcriptional phenotype and maintained their capacity to respond transcriptionally and functionally to a secondary pro-matrix stimuli (i.e., transforming growth factor β3) within 7 days after cessation of TSA treatment. Together, this work defines the efficacy, reproducibility, safety, and feasibility of future translational approaches for nuclear softening to treat dense connective tissue injuries.