Combining BMP-6, TGF-β3 and hydrostatic pressure stimulation enhances the functional development of cartilage tissues engineered using human infrapatellar fat pad derived stem cells

Abstract

The objective of this study was to identify a combination of growth factors that could be used with hydrostatic pressure (HP) stimulation to enhance the functional development of cartilaginous grafts engineered using human infrapatellar fat pad derived stem cells (FPSCs) isolated from osteoarthritic patients. Agarose hydrogels were first seeded with FPSCs at different seeding densities and maintained in a chondrogenic media supplemented with TGF-β3. It was found that chondrogenesis of human FPSCs in hydrogel culture is dependent on the cell seeding density (10 versus 30 million cells per ml), with greater sulphated glycosaminoglycan (sGAG) and collagen synthesis (normalised to DNA content) observed at higher seeding densities. Additional supplementation with BMP-6 was found to augment cartilage-specific matrix synthesis, also in a cell seeding density dependent manner, increasing both cell proliferation and sGAG synthesis in constructs seeded at higher densities, but having no significant effect at lower cell seeding densities. The application of cyclic HP to FPSC seeded constructs cultured in the presence of both TGF-β3 and BMP-6 had no significant effect on DNA content or sGAG accumulation, however it did improve the dynamic modulus of the engineered tissue. These tissues stained strongly for both alcian blue and type II collagen and negatively for type X collagen. The results of this study point to the benefits of combining both biochemical and biophysical stimulation to engineer functional cartilage grafts using diseased human FPSCs.