Genetic Modification of Human Peripheral Blood Aspirates Using Recombinant Adeno-Associated Viral Vectors for Articular Cartilage Repair With a Focus on Chondrogenic Transforming Growth Factor-β Gene Delivery.

: Transplantation of genetically modified peripheral blood aspirates that carry chondrogenically competent progenitor cells may offer new, convenient tools to treat articular cartilage lesions compared with the more complex and invasive application of bone marrow concentrates or of bone marrow-derived mesenchymal stem cells. Here, we show that recombinant adeno-associated viral (rAAV) vectors are powerful gene vehicles capable of successfully targeting primary human peripheral blood aspirates in a stable and safe manner, allowing for an efficient and long-term transgene expression in such samples (up to 63 days with use of a lacZ reporter gene and for at least 21 days with application of the pleiotropic, chondrogenic factor transforming growth factor-β [TGF-β]). rAAV-mediated overexpression of TGF-β enhanced both the proliferative and metabolic properties of the peripheral blood aspirates, also increasing the chondrogenic differentiation processes in these samples. Hypertrophy and osteogenic differentiation events were also activated by production of TGF-β via rAAV, suggesting that translation of the current approach in vivo will probably require close regulation of expression of this candidate gene. However, these results support the concept of directly modifying peripheral blood as a novel approach to conveniently treat articular cartilage lesions in patients.

SIGNIFICANCE: The present study evaluated a novel, clinically relevant approach based on the use of genetically modified peripheral blood aspirates as a potent, less invasive source of chondroreparative progenitor cells (compared with isolated mesenchymal stem cells or bone marrow aspirates) to further improve the healing of cartilage injuries in patients. The results demonstrate that gene transfer in human peripheral blood aspirates can be successfully performed by using clinically adapted recombinant adeno-associated viral vectors, leading to the stimulation of chondrogenic events upon overexpression of the chondrogenic TGF-β. This approach forms a promising basis for the further development of novel therapeutic options to treat articular cartilage defects by transplantation of genetically modified blood in vivo upon controlled regulation of gene expression.