Direct adenovirus-mediated insulin-like growth factor I gene transfer enhances transplant chondrocyte function

Cell-based cartilage-resurfacing procedures may be enhanced by the addition of insulin-like growth factor I (IGF-I) to the transplant biomatrix. Given the relatively short half-life of IGF-I in biological systems, however, ma intenance of effective concentrations of this peptide necessitates either h igh initial doses, or repeated treatment. This study investigated IGF-I del ivery via adenoviral gene therapy, targeting graftable articular chondrocyt es, Cultured articular chondrocytes were infected with an E1-deleted adenov iral vector containing IGF-I-coding sequence under CMV promoter control. In creased adenovirus-IGF-I concentrations resulted in coordinate increase in IGF-I mRNA and ligand expression; however, chondrocyte matrix synthesis was maximized by the lower adenovirus-IGF-I concentration (100 MOI) without ad ditional increase at 200 or 500 MOI. Using 100 MOI, infected monolayers pro duced medium IGF-I content of at least 10 ng/ml in each 48-hr period for 28 days, reaching a day 4 peak concentration of 66 +/- 4.0 ng/ml. These conce ntrations were sufficient to produce significant stimulation of normal cart ilage matrix gene expression. The concentration of secreted matrix products in medium from infected monolayers was increased up to 8-fold over uninfec ted control cultures. Moreover, compared with uninfected cultures, cells in infected cultures mere more resistant to dedifferentiation over time under serum-starved conditions, maintaining a normal chondrocyte molecular pheno type for at least 28 days. These data indicate that cultured chondrocytes a re readily transduced by recombinant adenoviral vectors. The adenoviral-IGF transgene is abundantly expressed and its product secreted at therapeutic concentrations for at least 28 days, resulting in increased matrix biosynth esis and maintenance of the chondrocytic phenotype. Combined, this informat ion suggests that there may be significant value in preimplantation adenovi ral-IGF gene therapy for chondrocytes destined for cartilage resurfacing.