The Constitutive Expression of Type X Collagen in Mesenchymal Stem Cells from Osteoarthritis Patients Is Reproduced in a Rabbit Model of Osteoarthritis

The expression of type X collagen (COL X), a late-stage chondrocyte hypertrophy marker in human mesenchymal stem cells (MSCs) from osteoarthritis (OA) patients poses a major setback to current cartilage and intervertebral disc tissue engineering efforts. However, it is not yet clear whether COL X is expressed by all human bone marrow stem cells or if it is related to age, gender, site, disease status, or drug therapy. In the current study, we report that COL X expression is upregulated in MSCs from rabbits in a surgical instability model of OA (anterior cruciate ligament transection (ACLT)) when compared to control rabbit MSCs. Thus COL X expression in OA is a common phenomenon that is due to the disease process itself and not to other environmental factors. It is, therefore, critical to understand MSC phenotype in OA patients, as these cells are essential clinically for biological repair of cartilage lesions using autologous stem cells.