Isolation of pig bone marrow mesenchymal stem cells suitable for one-step procedures in chondrogenic regeneration

Large animals such as pigs are good models for skeletal tissue engineering, since they provide physical forces similar to those of humans. Porcine bone marrow mesenchymal stem cells (BMSCs) have shown regenerative capacity similar to those of human BMSCs and can therefore be preclinically applied in settings corresponding to autologous transplantation in patients. Aiming at a one-step procedure for cartilage regeneration with autologous BMSCs, three straightforward isolation methods for BMSCs of Göttingen minipigs were compared. For this purpose, the BMSC fraction was enriched by red blood cell (RBC) lysis, dextran sedimentation or density gradient centrifugation. Isolated BMSCs were evaluated with regard to cell yield, proliferation capacity, phenotype and ability to differentiate to the chondrogenic lineage. Highest cell yields determined at the time of subcultivation were obtained using RBC lysis. In comparison, dextran sedimentation was less efficient but superior to density gradient centrifugation, which yielded significantly lower cell numbers than RBC lysis. The evaluated isolation methods resulted in cultures with equal proliferative capacity, with constant population doubling times of 50-55 h for at least 100 days (approximating to 40 cumulative population doublings) in vitro. Chondrogenic differentiation in micromass pellet cultures was evaluated by glycosaminoglycan quantification, histological staining with Alcian blue and safranin O and immunohistochemical analysis for collagen type II. These evaluations demonstrated that all three isolation methods yielded cells capable of generating cartilaginous tissue in vitro. According to our data, RBC lysis can be used to efficiently isolate porcine BMSCs in a short time frame which would allow for intraoperative one-step procedures in preclinical cartilage regeneration studies.