CRISPR-engineered mesenchymal stromal cells for cartilage and bone repair

Mesenchymal stromal cells (MSCs) are among the best-characterized cell types in regenerative medicine. They can be readily expanded in culture and differentiated into various tissues and cells, while also exhibiting immunomodulatory characteristics. However, MSCs have limited therapeutic efficacy because they have low survival rates, are heterogeneous, and lose their ability to function after transplantation. New advances in genome editing with CRISPR-Cas9 have opened the door to targeted genetic manipulation of MSCs, ushering in an era of improved regenerative potential, particularly for bone and cartilage repair. This review focuses on recent advances in using CRISPR-modified MSCs for musculoskeletal regeneration, with particular emphasis on promoting osteogenesis, chondrogenesis, angiogenesis, immunomodulation, and extracellular matrix remodeling. Preliminary studies have identified several key targets, including the transcription factor RUNX2, which is associated with positive differentiation outcomes; CXCR4, which is linked to tissue-specific homing; IL-10 as an anti-inflammatory target; and PD-L1 as an immunomodulatory target with promising therapeutic potential. Furthermore, cell-free therapeutic approaches, based on the secretome and extracellular vesicles (EVs) engineered with MSCs, have gained increasing attention. Recently, studies have also focused on enhancing tissue regeneration by using genetically engineered MSCs in biomaterials and hydrogel systems, as well as scaffold-based systems. Although preclinical results are encouraging, challenges such as off-target effects, genomic stability, delivery efficiency, manufacturing standardization, and long-term safety concerns still hinder clinical translation. More importantly, no clinical trials have registered the use of engineered MSCs using the CRISPR for cartilage and/or bone regeneration, indicating a disconnect between experimental progress and clinical use. Overall, this CRISPR-based “genetic modification” approach to MSCs is a promising strategy to enhance their therapeutic potential and develop the next generation of regenerative treatments for skeletal diseases.