Meniscus injuries are highly prevalent, and both meniscus injury and subsequent surgery are linked to the development of post-traumatic osteoarthritis (PTOA). Although the pathogenesis of PTOA remains poorly understood, the inflammatory cytokine IL-1 is elevated in synovial fluid following acute knee injuries and causes degradation of meniscus tissue and inhibits meniscus repair. Dynamic mechanical compression of meniscus tissue improves integrative meniscus repair in the presence of IL-1 and dynamic tensile strain modulates the response of meniscus cells to IL-1. Despite the promising observed effects of physiologic mechanical loading on suppressing inflammatory responses of meniscus cells, there is a lack of knowledge on the global effects of loading on meniscus transcriptomic profiles. In this study, we compared two established models of physiologic mechanical stimulation, dynamic compression of tissue explants and cyclic tensile stretch of isolated meniscus cells, to identify conserved responses to mechanical loading. RNA sequencing was performed on loaded and unloaded meniscus tissue or isolated cells from inner and outer zones, with and without IL-1. Overall, results from both models showed significant modulation of inflammation-related pathways with mechanical stimulation. Anti-inflammatory effects of loading were well-conserved between the tissue compression and cell stretch models for inner zone; however, the cell stretch model resulted in a larger number of differentially regulated genes. Our findings on the global transcriptomic profiles of two models of mechanical stimulation lay the groundwork for future mechanistic studies of meniscus mechanotransduction, which may lead to the discovery of novel therapeutic targets for the treatment of meniscus injuries.

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Background We recently reported aberrant processing and localization of the precursor PNC (pro‐N‐cadherin) protein in failing heart tissues and detected elevated PNC products in the plasma of patients with heart failure. We hypothesize that PNC mislocalization and subsequent circulation is an early event in the pathogenesis of heart failure, and therefore circulating PNC is an early biomarker of heart failure. Methods and Results In collaboration with the Duke University Clinical and Translational Science Institute's MURDOCK (Measurement to Understand Reclassification of Disease of Cabarrus and Kannapolis) study, we queried enrolled individuals and sampled 2 matched cohorts: a cohort of individuals with no known heart failure at the time of serum collection and no heart failure development in the following 13 years (n=289, cohort A) and a matching cohort of enrolled individuals who had no known heart failure at the time of serum collection but subsequently developed heart failure within the following 13 years (n=307, cohort B). Serum PNC and NT‐proBNP (N‐terminal pro B‐type natriuretic peptide) concentrations in each population were quantified by ELISA. We detected no significant difference in NT‐proBNP rule‐in or rule‐out statistics between the 2 cohorts at baseline. In participants who developed heart failure, serum PNC is significantly elevated relative to those who did not report development of heart failure ( P <0.0001). Receiver operating characteristic analyses of PNC demonstrate diagnostic value for subclinical heart failure. Additionally, PNC has diagnostic potential when comparing participants with no reported heart failure risk factors from cohort A to at‐risk participants from cohort B over the 13‐year follow‐up. Participants whose PNC levels measure >6 ng/mL have a 41% increased risk of all‐cause mortality independent of age, body mass index, sex, NT‐proBNP, blood pressure, previous heart attack, and coronary artery disease ( P =0.044, n=596). Conclusions These data suggest that PNC is an early marker of heart failure and has the potential to identify patients who would benefit from early therapeutic intervention.

N-cadherin mediates physical linkages in a variety of force-generating and load-bearing tissues.To enable visualization and quantification of mechanical loads experienced by N-Cadherin, we developed a genetically-encoded FRET-based tension sensor for this protein. We observe that N-Cadherin supports non-muscle myosin II (NMII) activity-dependent loads within the adherens junctions (AJs) of VSMCs and the synaptic junctions (SJs) of neurons. To probe the relationship between mechanical loads and AJ/SJ formation, we evaluated the relationships between Ncadherin tension and the size of these adhesion structures. In VSMCs, no relationship between N-cadherin tension and AJ size was observed, consistent with previously observed homeostatic regulation of mechanical loading. In neurons, a strong correlation between SJ size and N-cadherin load was observed, demonstrating an absence of homeostatic regulation. Treatment with glycine, a known initiator of synapse maturation, lead to increased SJ size and N-cadherin load, suggesting a role for mechanosensitive signaling in this process. Correspondingly, we observe that NMII activity is required for the Src-mediated phosphorylation of NMDAR subunit GluN2B at Tyr 1252, which is a key event in synaptic potentiation. Together these data demonstrate Ncadherin tension is subject to cell type specific regulation and that mechanosensitive signaling occurs within SJs.

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