Subchondral bone derived mesenchymal stem cells display enhanced osteo-chondrogenic differentiation, self-renewal and proliferation potentials

Abstract

Rabbit mesenchymal stem cells (MSCs) are important seed cells in regenerative medicine research, particularly in translational research. In the current study, we showed that rabbit subchondral bone is a reliable source of MSCs. First, we harvested subchondral bone (SCB) from the rabbit knee-joint and initiated the MSC culture by cultivating enzyme-treated SCB. Adherent fibroblast-like cells that outgrew from SCB fulfill the common immuno-phenotypic criteria for defining MSCs, but with low contamination of CD45+ hematopoietic cells. Interestingly, differentiated SCB-MSCs expressed osteogenic and chondrogenic markers at significantly higher levels than those in bone marrow cell suspension-derived MSCs (BMS-MSCs) (P<0.05). No differences in the expression of adipogenic markers between SCB-MSC and BMS-MSC (P>0.05) were observed. Moreover, the results of the colony forming unit-fibroblast assay and sphere formation assay demonstrated that the SCB-MSCs had increased self-renewal potential. SCB-MSCs expressed higher levels of the stemness markers Nanog, OCT4, and Sox-2 compared to in BMS-MSCs (P<0.05). Furthermore, the results of both the CCK-8-based assay and CFSE dilution assay showed that SCB-MSCs exhibited enhanced proliferative capacity. In addition, SCB-MSCs exhibited higher phosphorylation of extracellular signal-related kinase/mitogen-activated protein kinase signaling, which is closely related to MSC proliferation. In conclusion, we identified SCB-MSCs as a novel stem cell population that met the requirements of MSCs; the unique properties of SCB-MSC are important for the potential treatment of tissue damage resulting from disease and trauma.