There are no effective treatments for osteoarthritis (OA). Though regenerative therapies including mesenchymal stromal cells (MSCs) may enhance cartilage healing, the mechanisms remain unclear. Disadvantages include regulatory burdens and cost associated with MSCs. Therefore, alternative cell-free therapies are being explored, including extracellular vesicles (EVs).

EVs are nanoparticles containing diverse cargos, including organelles. Evidence suggests MSCs can transfer mitochondria to injured cells by EVs (mitovesicles; mitoEVs). MitoEVs improve recipient cell survival in other tissues but have not been investigated in cartilage. We have characterized MSCderived mitoEVs, and found MSCs donate mitochondria to injured chondrocytes in co-culture. However, effects of isolated mitoEVs on chondrocytes have not been studied. We hypothesize that 1) chondrocytes take up mitoEVs, improving respiratory capacity, and 2) blood products provide a culture-free source of mitoEVs.

Our objective is to investigate mitoEVs as a new regenerative therapy. Our aims are to investigate 1) effects of mitoEVs on equine OA chondrocytes and 2) non-cultured sources of mitoEVs. We will isolate mitoEVs from equine plasma, platelet rich plasma, bone marrow aspirate concentrate, and MSC-conditioned media. In Aim 1 we will treat cultured chondrocytes from horses with OA with MSC-derived mitoEVs. Microrespirometry will assess the ability of mitoEVs to rescue chondrocyte function. In Aim 2 we will use flow cytometry to characterize mitoEVs from blood products and compare to cell-culture derived mitoEVs. This study represents the first steps in developing mitoEVs as a mitochondrial function-targeted orthobiologic. The ACVS award will support rigorous research training to achieve my goal of becoming a clinician-scientist.