Bone Marrow-Derived Buffy Coat Can Supplement the Bone Marrow Stimulation Technique for Articular Cartilage Repair
Bone marrow stimulation (BMS) has been used as a popular operating technique to repair defect of knee articular cartilage. However, the regenerated tissue from BMS is known as a fibrocartilage rather than a hyaline cartilage and thinner than native cartilage. The objective of this study was to investigate the feasibility of autologous bone marrow-derived buffy coat transplantation in the regeneration of large full-thickness cartilage defect. Rabbits were divided into four groups: the defect was remained untreated as a negative control (Group 1), performed with BMS only using a drill (diameter: 5 mm) and a 17 gauge needle (Group 2), injected with concentrated autologous buffy coat isolated from the iliac crest after BMS (Group 3) and implanted with autologous osteochondral graft (AOG) as a positive control (Group 4). The cartilage defect was finally covered with a thin membrane made of cartilage matrix material using cross suture method in groups 1, 2 and 3. Bone marrow aspirated from iliac crest was diluted with phosphate-buffered saline. Buffy coat was isolated by centrifugation through a Ficoll density gradient at 2000 rpm for 30 min. The repaired cartilages in each experimental group were evaluated by macroscopic observation, histology with Safranin-O staining, immunohistochemistry for collagen type IIand ICRS scoring at 4 and 8 weeks post-operation. In the results of gross observation and Safanin-O staining, the fibrous/hyaline cartilage was regenerated in groups 1 and 2, while the hyaline cartilage tissues with mature matrix and columnar organization of chondrocytes were observed in groups 3 and 4. In the immunohistochemical staining, expression of type II collagen was gradually increased along with time at the pericellular region in the repaired tissues of groups 2, 3 and 4. In the total ICRS, histological score increased significantly along with time in all groups. The ICRS score was higher in groups 3 and 4 than in other groups. This study demonstrated that injection of autologous bone marrow buffy coat after BMS effectively regenerated cartilage defect in rabbit model, being more effective than the BMS alone and similar to AOG. It is speculated that the buffy coat could probably provide more mesenchymal stem cells to regenerate the articular cartilage defect. In addition the extracellular matrix membrane used to cover the defect efficiently prevented leakage of injected cells and blood clots from cartilage defect into the knee joint cavity. In conclusion, the injection of autologous bone marrow-derived buffy coat in case of BMS arthroplasty could be a useful clinical protocol for cartilage repair.
