Expression changes of inflammatory cytokines of tendon-derived stem cells in response to uniaxial stretching / 中华创伤杂志

ABSTRACT

Objective To observe the expression changes of inflammatory cytokines of human tendon-derived stem cells (TDSCs) under uniaxial stretching.Methods TDSCs were isolated from human gracilis tendon by collagenase digestion at very low density.Cells were detected for surface markers by flow cytometry,and tested for multi-differentiation potential in vitro.Repetitive uniaxial stretching was applied on the cells at 0％,4％,8％ or 10％ strain.Under the microscopy,cell alignment was observed after mechanical stretching.Expressions of inflammation factors COX-2 and MMP-1 were detected by qPCR and western blotting.Results TDSCs were successfully isolated from human gracilis tendon.Inflammatory cytokines CD29,CD44 and CD105 were positive,but CD45 and CD14 were negative.TDSCs could differentiate into osteocytes,adipocytes and chondrocytes in vitro.Cells were not realigned4 hours after mechanical stretching.MMP-1 mRNA expression was significantly down-regulated at 4％ strain (0.090 ± 0.007) compared to that at 0％ strain (0.247 ± 0.032,P ＜ 0.05).No significant difference was found in COX-2 mRNA expression at 4％ and 8％ strain (both was 0.005 ±0.001,P ＞0.05).MMP-1 and COX-2 mRNA expressions at 8％ strain (0.168 ± 0.040 and 0.007 ± 0.001)revealed no significant differences from those at 0％ strain (0.134 ±0.075 and 0.006 ±0.003) (P ＞0.05),whereas at 10％ strain MMP-1 and COX-2 mRNA expressions were significantly up-regulated (0.047 ± 0.003 and 0.496 ± 0.036) compared to those at 0％ strain (0.011 ± 0.003 and 0.005 ± 0.003)(P ＜ 0.05).Changes in MMP-1 and COX-2 protein expressions revealed similar trend as their mRNA expressions.In contrast to the setting of 0％ strain,4％ strain induced down-regulated MMP-1 and COX-2 proteins,8％ strain induced no significant changes in MMP-1 and COX-2 proteins,and 10％ strain induced up-regulated COX-2 protein despite minor increase in MMP-1 protein.Conclusions Mechanical stretching can affect the secretion of inflammatory cytokines.Low tensile stretch is associated with decreased expression of inflammatory cytokines while high tensile stretch promotes secretion of inflammatory cytokines.