A comparison of fibrin, agarose and gellan gum hydrogels as carriers of stem cells and growth factor delivery microspheres for cartilage regeneration.

The limited intrinsic repair capacity of articular cartilage has led to the investigation of different treatment options to promote its regeneration. The delivery of hydrogels containing stem or progenitor cells and growth factor releasing microspheres represents an attractive approach to cartilage repair. In this study, the influence of the encapsulating hydrogel on the ability of progenitor cells coupled with TGF-β3 releasing microspheres to form cartilaginous tissue was investigated. Fibrin, agarose and gellan gum hydrogels containing TGF-β3 loaded gelatin microspheres and progenitor cells derived from the infrapatellar fat-pad of the knee were cultured for 21 days in a chemically defined media. In the presence of TGF-β3 releasing microspheres, gellan gum hydrogels were observed to facilitate greater cell proliferation than fibrin or agarose hydrogels. Histological and biochemical analysis of the hydrogels indicated that fibrin was the least chondro-inductive of the three hydrogels, while agarose and gellan gum appeared to support more robust cartilage formation as demonstrated by greater sGAG accumulation within these constructs. Gellan gum hydrogels also stained more intensely for collagen type II and collagen type I, suggesting that although total collagen synthesis was higher in these constructs, that the phenotype may be more fibrocartilaginous in nature than normal hyaline cartilage. This study demonstrates how the encapsulating hydrogel can have a significant impact on the ability of stem cells to form cartilage when incorporated into a growth factor delivery system.