Characterization and immunogenicity of bone marrow-derived mesenchymal stem cells under osteoporotic conditions

Mesenchymal stem cells (MSCs) are characterized by their multilineage potential and low immunogenicity.However,the properties of MSCs under pathological conditions are unclear.The current study investigated the differentiation potential and immunological characteristics of bone marrow-derived MSCs from ovariectomized-osteoporotic rats (OP-BMSCs).Although the expression of cell morphology-and sternness-related surface markers was similar between OP-BMSCs and BMSCs from healthy rats (H-BMSCs),the proliferation rate was significantly decreased compared with that of H-BMSCs.Regarding multilineage potential,osteogenesis and chondrogenesis abilities of OP-BMSCs decreased,but the adipogenesis ability was significantly enhanced compared with that of H-BMSCs.As expected,decreased osteogenesis following osteogenic induction resulted in reduced expression of p-catenin,osteocalcin,and runt-related transcription factor 2 in OP-BMSCs.Remarkably,the expression of the co-stimulatory proteins CD40 and CD80 was significantly higher,whereas the expression of the negative costimulatory molecule programmed cell death ligand 1 was significantly lower in the OP-BMSCs than that in H-BMSCs.Consequently,H-BMSCs inhibited the proliferation and secretion of inflammatory cytokines from anti-CD3 antibody-activated T cells,whereas OP-BMSCs did not.These results indicate that decreased osteogenesis and increased immunogenicity of OPBMSCs contribute to bone loss in osteoporosis.

Substrate stiffness modulates bone marrow-derived macrophage polarization through NF-κB signaling pathway

The stiffness of the extracellular matrix(ECM)plays an important role in regulating the cellular programming.However,the mechanical characteristics of ECM affecting cell differentiation are still under investigated.Herein,we aimed to study the effect of ECM substrate stiffness on macrophage polarization.We prepared polyacrylamide hydrogels with different substrate stiffness,respectively.After the hydrogels were confirmed to have a good biocompatibility,the bone marrow-derived macrophages(BMMs)from mice were incubated on the hydrogels.With simulated by the low substrate stiffness,BMMs displayed an enhanced expression of CD86 on the cell surface and production of reactive oxygen species(ROS)in cells,and secreted more IL-1βand TNF-αin the supernatant.On the contrary,stressed by the medium stiffness,BMMs expressed more CD206,produced less ROS,and secreted more IL-4 and TGF-β.In vivo study by delivered the hydrogels subcutaneously in mice,more CD68+CD86+cells around the hydrogels with the low substrate stiffness were observed while more CD68+CD206+cells near by the middle stiffness hydrogels.In addition,the expressions of NIK,phosphorylated p65(pi-p65)and phosphorylated IκB(pi-IκB)were significantly increased after stimulation with low stiffness in BMMs.Taken together,these findings demonstrated that substrate stiffness could affect macrophages polarization.Low substrate stiffness promoted BMMs to shift to classically activated macrophages(M1)and the middle one to alternatively activated macrophages(M2),through modulating ROS-initiated NF-κB pathway.Therefore,we anticipated ECM-based substrate stiffness with immune modulation would be under consideration in the clinical applications if necessary.