Use of a Smooth, Resorbable Template for Delivery of Cultured Pellets of Autologous Chondrocytes to Articular Cartilage Defects—Preliminary Report

Background: Autologous chondrocyte transplantation (ACT) is the most commonly used cell-based surgical procedure for repair of articular cartilage defects. The challenges of this technique include dedifferentiation of chondrocytes following several in vitro passages, invasive means of transplantation, and inadequate cell retention leading to washout of transplanted cells. To overcome these obstacles, we developed a novel technique of transplanting high-density chondrocyte pellets seeded on a prefabricated, resorbable, rigid, 2-dimensional template amenable to minimally invasive implantation. Methods: Chondrocytes were obtained from the costal cartilage of New Zealand white rabbits and expanded in vitro in monolayer culture. After 2 passages, chondrocyte suspension was centrifuged and a total of 1 × 10(6) cells condensed on the surface of a prefabricated, resorbable template of LactoSorb plate (0.5-mm thick, 4-mm diameter). The construct was incubated for 24 hours in a culture medium before transplantation into circular 4-mm diameter, 0.5-mm deep defects in a non–weight-bearing part of the femoral condyle. Control defects were left empty or implanted with LactoSorb alone. Macroscopic and histological evaluation was performed 4 weeks posttransplantation. Results: Macroscopically, boundaries of all defects were demarcated and distinguishable from adjacent intact cartilage. Regenerative tissue in experimental group appeared white, smooth, and uniform showing more resemblance to hyaline cartilage. Control groups revealed absent cartilaginous tissue and defects were filled with soft, fibrous tissue with an irregular surface. Histologically, the repair tissue in the control groups was fibroinflammatory with irregular surface and no evidence of continuous chondrocytic regeneration. Cartilage regeneration in the experimental defects revealed a continuous, high-density layer of chondrocytes surrounding the LactoSorb plates. Consistently with chondrocyte pellets grown for 4 weeks only, the amount of extracellular matrix deposition in the transplanted group was less than the normal cartilage. Conclusion: We have developed a novel approach for ACT, utilizing high-density chondrocyte pellets seeded on a prefabricated, rigid, 2-dimensional resorbable carrier. Our study can serve as a model for further minimally invasive development of this technique and evaluating its potential role as an alternative in ACT.