Effect of inflammatory stimulation on biological function of human umbilical cord mesenchymal stem cells and its mechanism

Objective To investigate the effect of inflammatory stimulation on the biological function of human umbilical cord mesenchymal stem cells (MSCs) and its mechanism. Methods Under sterile condition, 40-60 ml cord blood of normal full-term caesarean section was taken, and the cells were separated by Ficoll Hypaque gradient centrifugation. After 24 hours of conventional culture, the cells were divided into 4 groups: C group (control group), LPSL group, LPSM group and LPSH group. Group C was added with complete culture medium. Group LPSL, group LPSM and group LPSH were added with equal amount of culture medium containing 12.5, 25, 50 μg/ml lipopolysaccharides (LPS) respectively. The effects of different concentrations of LPS on the proliferation and osteogenic differentiation of mesenchymal stem cells were observed. Results After incubation for 24 and 48 hours, the proliferation activity of MSCs in LPSL, LPSM and LPSH groups was higher than that in group C (P<0.05), and the proliferation ability of MSCs induced by low dose LPS for 48 h was the strongest (P<0.05). With the increase of culture time, the expression of nuclear factor kappa B (NF-κB) and Toll-like receptor 4 (TLR4) protein in the four groups increased gradually. The expression of NF-κB and TLR4 protein in the LPSL, LPSM and LPSH groups were higher than that in the control group (P<0.05). With the increase of LPS concentration, the expression of NF-κB and TLR4 protein increased gradually, with statistically significant difference (P<0.05). Alkaline phosphatase (ALP) activity and calcium nodule number in LPSL, LPSM and LPSH group were higher than those in group C; ALP activity and calcium nodule number in LPSM group were higher than those in LPSH group; ALP activity and calcium nodule number in LPSL group were higher than those in LPSM and LPSH, group with statistically significant difference (P<0.05). Conclusions Inflammatory response can stimulate the proliferation and osteogenic differentiation of human umbilical cord mesenchymal stem cells. Low concentration of LPS may be an ideal factor for the osteogenic differentiation of umbilical cord mesenchymal stem cells. It has certain significance and application prospect in the actual clinical disease treatment, but the detailed mechanism of action and whether the effect of lower dose is better still to be further studied. Key words: Lipopolysaccharides; Umbilical cord; Mesenchymal stromal cells; Cell proliferation; In vitro