Transforming growth factor β‐3 bound with sulfate polysaccharide in synthetic extracellular matrix enhanced the biological activities for neocartilage formation in vivo

The thermoreversible hydrogel of poly( N ‐isopropylacrylamide‐ co ‐acrylic acid) [p(NiPAAm‐ co ‐AAc)] was utilized in an injectable protein (growth factor) delivery system for use in tissue regeneration protocols. The transforming growth factor β (TGF β) proteins, which have been shown to bind to heparin, have been well established to induce chondrogenic differentiation in chondrocytes. In this study, we assessed the effects of heparin on the TGF β‐3 activities in rabbit chondrocytes embedded in thermoreversible hydrogel. The hydrogels embedded with chondrocytes and heparin‐bound TGF β‐3 were injected subcutaneously into nude mice, which were monitored for up to 8 weeks after injection. P(NiPAAm‐ co ‐AAc) hydrogels with TGF β‐3 were compared with the hydrogels with heparin bound to TGF β‐3 for the assessment of the effects of heparin binding on chondrogenic differentiation. To monitor the release of growth factor via in vivo analysis, we assessed the Cy5.5‐NHS‐conjugated growth factors via the bioimaging method. In terms of the release of growth factors, the release of heparin‐binding growth factor was slower than that of the growth factor itself. Additionally, the proliferation rate and cartilage‐specific ECM production were both found to be significantly higher in the presence of heparin binding than was observed with the controls. The quantity of cartilage‐associated ECM proteins was assessed via immunohistochemical staining (collagen type II) and safranin‐ O staining. These data indicate the potential use of heparin‐binding TGF β‐3 for the reconstruction of neocartilage formation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009