Innate and Hormone-Mediated Sex Differences in Extracellular Matrix Remodeling

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PROJECT SUMMARY Biological sex is a clear factor in an individual’s ability to repair and regenerate tissue. Females are at higher risk for soft tissue injuries compared to age-matched males and exhibit higher rates of degenerative diseases such as osteoporosis, sarcopenia, osteoarthritis, and carpal tunnel syndrome. One common hallmark of these degenerative diseases is the disruption in homeostasis of the extracellular matrix (ECM). A delicate balance in tissue production and breakdown is essential to healthy function in every single tissue. Production of too much matrix can lead to fibrosis, while excessive matrix breakdown results in weakened tissue function. However, the role that biological sex plays in the processes of ECM homeostasis are currently unknown. A fundamental understanding of sex-based differences in tissue remodeling, and the regulation of this process by sex hormone signaling, will be critical to understanding divergence in injury and disease and establishing patient- specific regenerative strategies. The overall goal of our research program is to understand how biological sex regulates the process of ECM remodeling, from initial mechanotransduction to signal processing to ECM synthesis. Theme 1: Do male and female cells sense their local mechanical environment differently? There is evidence in many tissues that ECM structure, organization, and resulting function differs between age-matched males and females. However, the effect this has on cell biology is currently unknown. Custom-built and commercially available bioreactors will be used to identify differences in the sensing and cell- level responses to mechanical stimuli based on biological sex alone (isolated cells) and the local environment (explant tissue and engineered microenvironments). Theme 2: Is the balance of matrix production and breakdown altered by biological sex? Since degenerative diseases rely on a disruption of the balance between synthesis and degradation, a broad-spectrum approach to understanding ECM remodeling is necessary. Using an established model of mechanically-driven ECM remodeling, we can assess synthesis of ECM molecules and ECM-degrading enzymes, as well as detect products of ECM breakdown in real time. These techniques will allow for a whole picture of ECM turnover in real time. Theme 3: How does the presence of sex hormones affect cell signaling pathways associated with ECM remodeling? Dramatic changes in ECM structure during pregnancy clearly point to a substantial role for hormone signaling in ECM remodeling, and studies demonstrate a significant role for estrogen signaling in musculoskeletal and cardiac tissues. Using custom- designed fluid exchange bioreactors, we will have precise control over the concentration and duration of sex hormones exposure as well as the local mechanical environment simultaneously, allowing us to study the effect of estrogen and progesterone signaling in different phases of the remodeling process. These studies will enable a fundamental understanding of the contribution of biological sex to tissue repair capacity and pave the way for our novel in vitro tools to identify new targets for the development of patient-specific therapeutics.