Engineered BMSCs-EVs delivering PBX1 improve damaged cartilage in mouse osteoarthritis by activating CACNB4/ERK signaling.

Current therapies for osteoarthritis (OA) primarily manage symptoms, failing to halt disease progression or regenerate damaged cartilage. Bone marrow mesenchymal stem cells (BMSCs) offer regenerative potential, but their direct application faces challenges. Their secreted extracellular vesicles (EVs), which are cell-free and immunologically inert, represent a promising alternative. These EVs can suppress cartilage degradation and prevent articular cell apoptosis, yet their therapeutic efficacy can be further enhanced through targeted engineering.

Researchers isolated BMSC-derived EVs via ultracentrifugation. They engineered these EVs by transfecting BMSCs with plasmids expressing a chondrocyte-affinity peptide (CAP) and Pre-B-cell leukemia transcription factor 1 (PBX1). In vitro, OA injury was induced in chondrocytes with IL-1β. In vivo, a DMM surgical model established OA in mice. The efficacy of different EVs, including engineered variants, was then evaluated in both IL-1β-treated chondrocytes and the DMM mouse model, examining cartilage integrity and cellular responses.

Both CAP modification and increased protein loading of PBX1 significantly strengthened the protective effect of EVs on chondrocytes and ameliorated OA-induced cartilage damage in mice. The study elucidated a key mechanism: PBX1 promoted extracellular signal-regulated kinase (ERK) signaling and the expression of the downstream molecule c-FOS in chondrocytes. This occurred by activating the transcriptional expression of calcium channel voltage-dependent subunit beta 4 (CACNB4). > The chondroprotective effect of engineered EVs was significantly attenuated by inhibiting CACNB4/ERK signaling in both IL-1β-treated chondrocytes and the DMM-induced mouse model, confirming the pathway's critical role. These findings highlight the enhanced therapeutic potential of engineered BMSCs-EVs through targeted delivery of PBX1.