Full-thickness cartilage defects present a substantial clinical challenge. People are remaining active longer, and orthopaedic surgeons need techniques that effectively produce repair tissue that can withstand the test of time. The challenge is to find a way to achieve filling of cartilage defects with sufficiently cartilage-like tissue that is able to withstand repetitive loads without degeneration and loss of function. To date, efforts have failed to achieve good long-term results, at least in part because of the inability to recapitulate the type-II-collagen and aggrecan content of normal hyaline cartilage. Recent efforts have focused on cellular therapies—using chondrocytes or mesenchymal stem cells—as the basis for regeneration of repair tissue and for gene therapy approaches to enhance healing. Chondrocytes are ideally suited for the production of hyaline cartilage but challenging to obtain without donor site morbidity or the potential for inciting an immune response to allogenic cells. Bone-marrow-derived mesenchymal stem cells (BMDMSCs) provide an appealing alternative cell source with the potential to differentiate into chondrocytes following implantation and ease of collection with acceptable morbidity. Platelet-rich plasma has also gained recent attention as a readily available source of anabolic growth factors and cytokines with the potential to drive chondrogenesis.

The paper by Goodrich et al. describes the use of culture-expanded BMDMSCs combined with platelet-rich plasma in the form of an autologous platelet-enhanced fibrin (APEF) scaffold to enhance cartilage repair in a full-thickness cartilage defect model in the horse. APEF alone served as the control in the paired, contralateral limb of each horse. The horse provides an excellent model for cartilage healing because the large articular surface enables creation of a critical-size defect (15 mm in diameter) that does not heal simply by flow of normal cartilage from the healthy margin and because of the relatively high loads comparable with those in people. The technique investigated has the advantages of being deliverable by minimally invasive techniques using an arthroscope and of being autologous in nature. Lesions were evaluated in the short term (at three months with arthroscopy) and long term (at twelve months with arthroscopy, histological analysis, magnetic resonance imaging, micro-computed tomography, and biomechanical testing).