Moran, Steven L.

ABSTRACT Our study aimed to develop a novel, reproducible, minimally invasive turkey knee osteoarthritis (OA) model and evaluate whether intra‐articular hyaluronan (HA) alone or combined with purified exosome product (PEP) attenuates OA‐related functional and structural deterioration. OA was induced arthroscopically by transection of the anterior and posterior cruciate ligaments with resection of the anterior horn of the medial meniscus. Animals received intra‐articular injections of saline, HA, or PEP + HA at postoperative 2–5 weeks. Gait was assessed at 4, 8, and 12 weeks, and cartilage degeneration, subchondral bone sclerosis, osteophyte formation, synovial fibrosis, heterotopic ossification, and meniscal integrity were evaluated by quantitative CT and histology at week 12. Compared with saline, HA improved lameness, preserved cartilage glycosaminoglycan content, and reduced meniscal rupture, subchondral bone sclerosis, and periarticular heterotopic ossification. PEP + HA provided additional benefits, including prolonged stance phase, reduced synovial fibrosis, and greater chondroprotection than HA alone, while plantar pressure variables, subchondral bone remodeling, and patellar osteophytes did not differ between HA and PEP + HA. This turkey model reliably produces human‐like OA changes and enables longitudinal functional and structural assessment. Intra‐articular HA mitigated OA progression, and the addition of PEP conferred incremental joint protection.

ABSTRACT Extracellular vesicles (EVs) are non‐replicating, lipid membrane‐bound nanoparticles released by most eukaryotic cells into the extracellular space. When derived from platelets, a subset of EVs can exhibit remarkable anti‐inflammatory and antioxidant properties, making them attractive candidates to attenuate sterile inflammatory states such as limb skeletal muscle ischaemia‐reperfusion injury (IRI). Peripheral extremity IRI complicating acute limb revascularisation procedures, replantation of major traumatic amputations and limb allotransplants can trigger a life‐threatening reperfusion syndrome that leads to multi‐organ system failure and death. In this study, we used a platelet‐derived EVs‐enriched preparation as a therapeutic strategy for extremity IRI. To allow for a clinically translatable drug delivery strategy, we established and validated a catheter‐directed regional intra‐arterial limb infusion (RLI) delivery approach that permitted selective and effective targeting of pEVs to limb skeletal muscles and soft tissues in the vascularly isolated rodent extremity simulating pre‐reperfusion preservation and revascularisation conditions of the ischaemic or amputated extremity. In addition to being safe and feasible, we demonstrated robust retention of EVs by skeletal muscles of the operative limb during the early critical phase of reperfusion injury following RLI. We also show that pretreatment of ischaemic skeletal muscles using an pEVs‐enriched formulation just before reestablishing extremity blood flow alleviated metabolic derangements and suppressed the systemic and localised proinflammatory cytokine response associated with skeletal muscle reperfusion and reduced histologic markers of myofibre injury without adverse effects on serum chemistries. This work opens a new perspective to investigate novel approaches for regional delivery of therapeutic pEVs to skeletal muscle to mitigate limb IRI in vivo, and to achieve both in situ and ex vivo targeted delivery of nanocarriers to the isolated limb tissue for other therapeutic applications.