HLA-Engineered iPSC-Derived Mesenchymal Stromal Cells for the Treatment of Osteoarthritis in Mice

Osteoarthritis (OA) is one of the most prevalent degenerative joint diseases, and there is no approved pharmacological therapy that can reliably reverse cartilage degeneration or restore cartilage structure. Allogeneic mesenchymal stromal cells (MSCs) have shown therapeutic potential for OA, but inflammatory conditions can enhance HLA expression and increase allogeneic immune recognition risk. Here, we generated B2M and CIITA double-knockout induced pluripotent stem cells (dKO-iPSCs) using CRISPR/Cas9 and subsequently differentiated them into dKO-iMSCs. B2M/CIITA double-knockout did not affect iPSC pluripotency, karyotype, or teratoma formation. dKO-iMSCs retained characteristic MSC phenotypes, exhibited greater proliferative capacity than tissue-derived MSCs, and could be expanded to passage 18. Notably, HLA-ABC and HLA-DR expression remained undetectable in dKO-iMSCs even after IFN-γ stimulation. In co-culture assays with PHA-L-stimulated allogeneic PBMCs, dKO-iMSCs suppressed PBMC and T-cell proliferation as effectively as wild-type iMSCs, indicating preservation of their immunomodulatory activity. Intra-articular administration of dKO-iMSCs significantly reduced cartilage degeneration in the destabilization of the medial meniscus (DMM) mouse model of OA. The treatment showed greater therapeutic efficacy than wild-type iMSCs and tissue-derived MSCs and did not cause evident systemic organ toxicity. Single-cell RNA sequencing of BM-MSCs and dKO-iMSCs after in vitro IFN-γ stimulation revealed enhanced extracellular matrix-associated cell-cell communication and markedly reduced IL1B expression in dKO-iMSCs, indicating a less pro-inflammatory and more matrix-supportive cellular state under inflammatory conditions. Collectively, B2M/CIITA double-knockout enables sustained reduction in HLA expression while preserving the MSC phenotype and immunomodulatory activity, and enhances the therapeutic efficacy of iMSCs in the mouse OA model, providing a potential strategy for developing iPSC-derived MSCs with reduced HLA expression for allogeneic cell therapy.