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

Abstract

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. Stem Cells Translational Medicine 2017;6:249–260

Gene therapy for chondral and osteochondral regeneration: is the future now?

“…On the other hand, sc-AAV produces higher levels of protein more quickly and, for this reason, it could become the preferred choice for gene therapy trials [60]. rAAV is used for the delivery of IGF-1 [61][62][63], TGF-β [2,64], FGF-2 [65], SOXs [59,64,66] and IL1ra genes [67]. scAVV is used for the delivery of IL1ra [68] (Table 1).…”

“…The critical actor in this pathophysiological process is the osteochondral unit. The activation of inflammatory cascades within the joint leads to a gradual deterioration of cartilaginous extracellular matrix (ECM) and activation of osteoclasts, with consequent degradation of subchondral bone [2]. Focal chondral and osteochondral defects are usually considered to have limited spontaneous healing or regenerative potential.…”

“…Focal chondral and osteochondral defects are usually considered to have limited spontaneous healing or regenerative potential. This is due to cartilage characteristics, including low chondrocyte density, slow ECM production and cartilage aneural and avascular structure [2]. Synoviocytes intervene in repairing chondral defects, but their action is often inadequate and larger defects can arise [3].…”

“…The treatment of generalized OA lesions is more complex. Progressively worsening of the joint microenvironment towards chronic inflammation limits the possibility of cartilage to repair or regenerate [2].…”

Peripheral blood aspirates overexpressing IGF‐I via rAAV gene transfer undergo enhanced chondrogenic differentiation processes

“…Damaged adult hyaline articular cartilage, the tissue that is essential for weight absorption and smooth gliding of the articulating surfaces in diarthroidal joints, does not naturally undergo competent repair processes in the absence of blood vessels and lymphatic drainage that may provide regenerative progenitor cells in sites of injury . Lesions such as traumatic focal defects or occurring in osteoarthritis (OA) are infiltrated by cells migrating from the synovial membrane that fail to produce high‐quality repair tissue, leading to progression of the injury over time .…”