Repair of knee joint articular osteochondral defects with collagen complex gradient hydroxyapatite biphasic scaffold loaded with chondrocytes in rabbits

Abstract

Objective To evaluate the effectiveness and feasibility for the treatment of osteochondral defects on the femoral condyles by collagen/hydroxyapatite (Col/HA) biphasic scaffolds loaded with the cultured articular cartilage chondrocytes in rabbit knee joint. Methods Biphasic scaffolds were constructed with collagen complex gradient hydroxyapatite. The chondrocytes of third generation were embedded in the biphasic scaffolds' collagen. After culture for one week in vitro, the complexes of chondrocytesscaffold were transplanted to repair the articular osteochondral defects of the femoral condyle of rabbit knees ( the defects were 4 mm in diameter, 3.5 mm in depth, extending down to the subchondral bone). Healing of defects was assessed by gross and histological examination. Results Biphasic collagen/hydroxyapatite scaffold had good hydrophilia and permeability. Light microscopy and scanning electron microscopy revealed that chondrocytes attaching to the wall of microholes of the scaffold had largely maintained a rounded morphology and could secrete the extracellular matrix on the porous scaffold. Gross and light microscopic examination showed that the treatment of simple Col/HA scaffold improved defect filling compared with that left untreated, while the regenerated tissue was mainly fibrocartilage and showed little bone formation.When implanted with Col/HA scaffold combined with chondrocytes, most of the defects were filled with a well-established layer of cartilage tissue with new bone formation. Wakitani scoring showed that experimental group was superior to control groups in 16 weeks with the difference being significant between them (P ＜0.05). Conclusion The novel biphasic collagen/hydroxyapatite scaffold will possibly be an ideal scaffold for osteochondral tissue engineering. It may induce articular osteochondral regeneration to repair the defects of articular osteochondral in vivo after loaded with chondrocytes. Key words: Collagen; Hydroxyapatite; Tissue engineering; Chondrocyte; Osteochondral defect