Use of bone marrow stromal cells for tendon graft-to-bone healing: histological and immunohistochemical studies in a rabbit model

BACKGROUND: Despite increasing attention on the issue of tendon-to-bone integration, there has been no animal study on the use of cell therapy for promoting the insertion healing of tendon to bone. PURPOSE: To determine the efficacy of using a large number of bone marrow stromal cells (bMSCs) to enhance tendon-to-bone healing. STUDY DESIGN: Controlled laboratory study. METHODS: The hallucis longus tendons were translated into 2.5-mm diameter calcaneal bone tunnels in a New Zealand white rabbit model. The bone tunnels were treated with or without bMSCs. Three specimens from each group were harvested at 2, 4, and 6 weeks postoperatively and evaluated by conventional histological and immunohistochemical methods. RESULTS: At 4 weeks, the specimens with bMSCs exhibited more perpendicular collagen fiber formation and increased proliferation of cartilage-like cells, which was indicated by positive collagen type-II immuno-staining of the tendon-bone interface. In contrast, the specimens without bMSCs demonstrated progressive maturation and reorganization of fibrous tissue aligned along the load axis. CONCLUSION: Introduction of a large number of bone marrow stromal cells to the bone tunnel have shown to improve the insertion healing of tendon to bone in a rabbit model through formation of fibrocartilagenous attachment at early time points.