Repair of full-thickness articular cartilage defects by cultured mesenchymal stem cells transfected with the transforming growth factor β1 gene

Articular cartilage repair remains a clinical and scientific challenge with increasing interest focused on the combined techniques of gene transfer and tissue engineering. Transforming growth factor beta 1 (TGF-beta(1)) is a multifunctional molecule that plays a central role in promotion of cartilage repair, and inhibition of inflammatory and alloreactive immune response. Cell mediated gene therapy can allow a sustained expression of TGF-beta(1) that may circumvent difficulties associated with growth factor delivery. The objective of this study was to investigate whether TGF-beta(1) gene modified mesenchymal stem cells (MSCs) could enhance the repair of full-thickness articular cartilage defects in allogeneic rabbits. The pcDNA(3)-TGF-beta(1) gene transfected MSCs were seeded onto biodegradable poly-L-lysine coated polylactide (PLA) biomimetic scaffolds in vitro and allografted into full-thickness articular cartilage defects in 18 New Zealand rabbits. The pcDNA(3) gene transfected MSCs/biomimetic scaffold composites and the cell-free scaffolds were taken as control groups I and II,respectively. The follow-up times were 2, 4, 12 and 24 weeks. Macroscopical, histological and ultrastructural studies were performed. In vitro SEM studies found that abundant cartilaginous matrices were generated and completely covered the interconnected pores of the scaffolds two weeks post-seeding in the experimental groups. In vivo, the quality of regenerated tissue improved over time with hyaline cartilage filling the chondral region and a mixture of trabecular and compact bone filling the subchondral region at 24 weeks post-implantation. Joint repair in the experimental groups was better than that of either control group I or II, with respect to: ( 1) synthesis of hyaline cartilage specific extracellular matrix at the upper portion of the defect; ( 2) reconstitution of the subchondral bone at the lower portion of the defect and ( 3) inhibition of inflammatory and alloreactive immune responses. The transfected MSCs overexpressed their TGF-beta(1) gene products for at least 4 weeks in vivo. The control defects were filled with a mixture of fibrous and fibrocartilaginous tissue. The TGF-beta(1) gene transfected MSCs/poly-L-lysine coated PLA composite allografts used in this study are effective for articular cartilage repair. This novel TGF-beta(1) gene enhanced tissue engineering strategy may be of potential benefit to enhancing the repair of damaged articular cartilage, especially such damage caused by degenerative disease.