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Creators/Authors contains: "Dyment, Nathaniel A."

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  1. Free, publicly-accessible full text available July 1, 2024
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  3. Meniscal tears are associated with a high risk of osteoarthritis but currently have no disease-modifying therapies. Using a Gli1 reporter line, we found that Gli1 + cells contribute to the development of meniscus horns from 2 weeks of age. In adult mice, Gli1 + cells resided at the superficial layer of meniscus and expressed known mesenchymal progenitor markers. In culture, meniscal Gli1 + cells possessed high progenitor activities under the control of Hh signal. Meniscus injury at the anterior horn induced a quick expansion of Gli1-lineage cells. Normally, meniscal tissue healed slowly, leading to cartilage degeneration. Ablation of Gli1 + cells further hindered this repair process. Strikingly, intra-articular injection of Gli1 + meniscal cells or an Hh agonist right after injury accelerated the bridging of the interrupted ends and attenuated signs of osteoarthritis. Taken together, our work identified a novel progenitor population in meniscus and proposes a new treatment for repairing injured meniscus and preventing osteoarthritis. 
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  4. Abstract

    Tendons are unique dense connective tissues with discrete zones having specific structure and function. They are juxtaposed with other tissues (e.g., bone, muscle, and fat) with different compositional, structural, and mechanical properties. Additionally, tendon properties change drastically with growth and development, disease, aging, and injury. Consequently, there are unique challenges to performing high quality histological assessment of this tissue. To address this need, histological assessment was one of the breakout session topics at the 2022 Orthopaedic Research Society (ORS) Tendon Conference hosted at the University of Pennsylvania. The purpose of the breakout session was to discuss needs from members of the ORS Tendon Section related to histological procedures, data presentation, knowledge dissemination, and guidelines for future work. Therefore, this review provides a brief overview of the outcomes of this discussion and provides a set of guidelines, based on the perspectives from our laboratories, for histological assessment to assist researchers in their quest to utilize these techniques to enhance the outcomes and interpretations of their studies.

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  5. Abstract

    Following anterior cruciate ligament (ACL) reconstruction surgery, a staged repair response occurs where cells from outside the tendon graft participate in tunnel integration. The mechanisms that regulate this process, including the specific cellular origin, are poorly understood. Embryonic cells expressing growth and differentiation factor 5 (GDF5) give rise to several mesenchymal tissues in the joint and epiphyses. We hypothesized that cells from a GDF5 origin, even in the adult tissue, would give rise to cells that contribute to the stages of repair. ACLs were reconstructed inGdf5‐Cre;R26R‐tdTomato lineage tracing mice to monitor the contribution ofGdf5‐Cre;tdTom+cells to the tunnel integration process. Anterior−posterior drawer tests demonstrated 58% restoration in anterior−posterior stability.Gdf5‐Cre;tdTom+cells within the epiphyseal bone marrow adjacent to tunnels expanded in response to the injury by 135‐fold compared with intact controls to initiate tendon‐to‐bone attachments. They continued to mature the attachments yielding zonal insertion sites at 4 weeks with collagen fibers spanning across unmineralized and mineralized fibrocartilage and anchored to the adjacent bone. The zonal attachments possessed tidemarks with concentrated alkaline phosphatase activity similar to native entheses. This study established that mesenchymal cells from a GDF5 origin can contribute to zonal tendon‐to‐bone attachments within bone tunnels following ACL reconstruction.

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