Fibroblast-mediated delivery of growth factor complementary DNA into mousejoints induces chondrogenesis but avoids the disadvantages of direct viralgene transfer

Objective. To assess the advantages and disadvantages of a direct adenovira l and a cell-mediated approach to the induction of cartilage formation in j oints by transfer of growth factor genes. Methods. Adenoviral vectors carrying insulin-like growth factor 1 (IGF-1) o r bone morphogenetic protein 2 (BMP-2) complementary DNA were constructed a nd applied to primary human and murine chondrocytes or fibroblasts. Transge ne expression was quantified by enzyme-linked immunosorbent assay. Direct i njection of these vectors or AdLacZ, a reporter gene vector, into mouse kne e joints was compared with the transplantation of syngeneic fibroblasts (in fected ex vivo with the same vectors) with respect to virus spread, immune response, and cartilage formation by use of histologic, immunohistochemical , and molecular analyses. Results. AdIGF-1 and AdBMP-2 efficiently infected all cell types tested. Hu man cells secreted biologically relevant levels of protein over a period of at least 28 days. Direct transfer of AdLacZ into mouse knee joints resulte d in positively stained synovial tissues, whereas AdLacZ-infected fibroblas ts settled on the surface of the synovial membranes. Inadvertent spread of vector DNA into the liver, lung, and spleen was identified by nested polyme rase chain reaction in all mice that had received the vector directly; this rarely occurred following fibroblast-mediated gene transfer. Direct inject ion of AdBMP-2 induced the synthesis of new cartilage in periarticular mese nchyme, accompanied by extensive osteophyte formation. When AdBMP-2 was adm inistered by injecting ex vivo-infected fibroblasts, cartilage formation wa s observed only in regions near the injected cells. AdIGF-1 treatment did n ot lead to morphologic changes. Importantly, fibroblast-mediated gene trans fer avoided the strong immune response to adenovirus that was elicited foll owing direct application of the vector. Conclusion. Our results indicate that cell-mediated gene transfer provides sufficient BMP-2 levels in the joint to induce cartilage formation while av oiding inadvertent vector spread and immune reactions.