Human mesenchymal stem cells (MSCs) are present in most of the tissue matrix, taking part in their regeneration when injury or damage occurs. The aim of this study was to investigate the presence of cells with pluripotential characteristics in synovial membranes from osteoarthritic (OA) patients and the capacity of these cells to differentiate to chondrocytes.
Synovial membranes (n = 8) from OA patients were digested with collagenase. Isolated cells were cultured with DMEM, 20% FBS, and FGFb10 ng/mL. Cells from second subculture were used to carry out phenotypic characterization experiments (flow cytometry analysis with 11 monoclonal antibodies) and chondrogenic differentiation experiments(micropellet cultured in chondrogenic medium). Chondrogenic differentiation of cells was assessment by quantification of cartilage extracellular matrix components by following techniques: Safranin O, Toluidine Blue, and Alcian Blue stains to detect proteoglycans and immunohistochemistry to detect type I and II collagen.
Flow cytometry analyses showed that in our population more than 90% of cells were positive for MSC markers: CD29 (95%), CD44 (90%), CD73 (95%), CD90 (98%). Cells were negative for hematopoietic markers (CD11b, CD34, and CD45). Furthermore, cells showed positive stain to multipotent markers such as CD117 (c-kit) (98%), CD166 (74%), and STRO-1 (88%) and to quiescent satellite cells like PAX-7 (35%). The micropellet analyses showed that the culture of these cells with TGFbeta-3 for 2 and 3 weeks stimulates proteoglycan and collagen type II synthesis. Both molecules are characteristic of hyaline articular cartilage.
In this work, we demonstrate the presence of a cellular population with MSC characteristics in synovial tissue from OA patients. As MSC takes part in reparative processes of adult tissues, these cells could play an important role in OA pathogenesis and treatment.