Bioimaging of dexamethasone and TGF β-1 and its biological activities of chondrogenic differentiation in hydrogel constructs

This study examined the efficacy of poly(Ni-PAAm-co-AAc) as an injectable drug delivery vehicle and a cell therapeutic agent in the form of a supporting matrix for the chondrogenic differentiation of rabbit chondrocytes. The hydrogel constructs, which consisted of embedded cells co-encapsulating dexamethasone (Dex) and TGF β-1 or unloaded Dex, were used as controls to determine the effects of Dex and TGF β-1 on chondrogenic differentiation. The level of Dex and TGF β-1 released was monitored using a bioimaging method. The amount of Dex released from hydrogel was faster than that of TGF β-1. TGF β-1 was present in hydrogel for more than 4 weeks after the injection. The level of the cartilage associated ECM proteins was examined by immunohistochemical staining for collagen type II as well as by Safranin-O and Alcian blue (GAG) staining. These results highlight the potential of a thermo-reversible hydrogel mixed with the chondrocytes and differentiation delivery material for applications in neocartilage formation.