Tissue‐engineered composites for the repair of large osteochondral defects

TLDR

The study aimed to determine whether tissue‑engineered cartilage could serve as a mechanically functional template that remodels into osteochondral tissue during repair of large defects in adult rabbits, evaluated by quantitative structural and functional metrics. Engineered cartilage was produced in vitro from rabbit chondrocytes on a biodegradable scaffold, sutured to a subchondral support, and press‑fitted into a 7‑mm long, 5‑mm wide, 5‑mm deep osteochondral defect in the rabbit knee, with control groups including empty defects, cell‑free composites, and composites with or without adsorbed bone marrow. Over six months, the composites endured physiological loading, remodeled into osteochondral tissue with near‑normal Young’s moduli, integrated with host bone in 90 % of cases, and produced repairs in groups with bone marrow that were histologically superior to cell‑free composites yet still inferior to unoperated tissue.

Abstract

Abstract Objective To test the hypothesis that engineered cartilage can provide a mechanically functional template capable of undergoing orderly remodeling during the repair of large osteochondral defects in adult rabbits, as assessed by quantitative structural and functional methods. Methods Engineered cartilage generated in vitro from chondrocytes cultured on a biodegradable scaffold was sutured to a subchondral support and the resulting composite press‐fitted into a 7‐mm long, 5‐mm wide, 5‐mm deep osteochondral defect in a rabbit knee joint. Defects left empty (group 1) or treated with cell‐free composites (group 2) served as controls for defects treated with composites of engineered cartilage and the support, without or with adsorbed bone marrow (groups 3 and 4, respectively). Results Engineered cartilage withstood physiologic loading and remodeled over 6 months into osteochondral tissue with characteristic architectural features and physiologic Young's moduli. Composites integrated well with host bone in 90% of cases but did not integrate well with host cartilage. Structurally, 6‐month repairs in groups 3 and 4 were superior to those in group 2 with respect to histologic score, cartilage thickness, and thickness uniformity, but were inferior to those in unoperated control tissue. At 6 months, Young's moduli in groups 2, 3, and 4 (0.68, 0.80, and 0.79 MPa, respectively) approached that in unoperated control tissue (0.84 MPa), whereas the corresponding modulus in group 1 (0.37 MPa) was significantly lower. Conclusion Composites of tissue‐engineered cartilage and a subchondral support promote the orderly remodeling of large osteochondral defects in adult rabbits.