Tissue-engineered cartilage using fibrin/hyaluronan composite gel and its in vivo implantation

The importance of scaffold biomaterials has been emphasized for in vitro culture of tissue-engineered cartilage in a three-dimensional (3D) environment. In this study, we examined the feasibility of fibrin glue, mixed with hyaluronic acid (HA) as a composite scaffold. Fibrin glue has been a useful cell delivery matrix for cartilage tissue engineering and HA is a key component of normal articular cartilage. Our hypothesis is that compared to fibrin itself, a fibrin/HA composite can have significantly enhanced properties, due mainly to the added benefits of HA in the matrix. Pieces of cartilage were isolated from rabbit knees and the chondrocytes were harvested through enzymatic digestion. Both fibrin and fibrin/HA composite were prepared and subsequently implanted in nude mice (n = 9, each group) for 1, 2, and 4 weeks, respectively. The retrieved specimens were then analyzed and the results were compared. Cartilage-like tissue formation was detected earlier with fibrin/HA specimens. They produced significantly higher amounts of the extracellular matrix (ECM) molecules, GAG, and collagen at each time point than those in fibrin. Interestingly, the fibrin/HA composite was also competent in maintaining its initial size. Histology--Safranin O/fast green and Alcian blue--of the retrieved specimens found more intense, uniform staining in the fibrin/HA composites. Analysis of the gene expression of the ECM molecules also confirmed the benefits of the composite with added HA in the maintenance of phenotypic stability. The present study suggests that fibrin/HA composite may serve as a dependable cell delivery vehicle as well as a structural basis for tissue-engineered cartilage.