CRISPR-mediated Sox9 activation and RelA inhibition enhance cell therapy for osteoarthritis.

Osteoarthritis (OA) is a painful and debilitating disease affecting over 500 million people worldwide. Intraarticular injection of mesenchymal stromal cells (MSCs) shows promise for the clinical treatment of OA, but the lack of consistency in MSC preparation and application makes it difficult to further optimize MSC therapy and to properly evaluate the clinical outcomes. In this study, we used Sox9 activation and RelA inhibition, both mediated by the CRISPR-dCas9 technology simultaneously, to engineer MSCs with enhanced chondrogenic potential and downregulated inflammatory responses. We found that both Sox9 and RelA could be fine-tuned to the desired levels, which enhances the chondrogenic and immunomodulatory potentials of the cells. Intraarticular injection of modified cells significantly attenuated cartilage degradation and palliated OA pain compared with the injection of cell culture medium or unmodified cells. Mechanistically, the modified cells promoted the expression of factors beneficial to cartilage integrity, inhibited the production of catabolic enzymes in osteoarthritic joints, and suppressed immune cells. Interestingly, a substantial number of modified cells could survive in the cartilaginous tissues including articular cartilage and meniscus. Together, our results suggest that CRISPR-dCas9-based gene regulation is useful for optimizing MSC therapy for OA.