ABSTRACT
Objective To study the mechanical properties and degradation behavior of biodegradable silicon-covered magnesium alloy stent in vitro,to investigate the technical feasibility of its implantation into rabbit esophagus and to observe the tissue reaction in vivo.Methods The mechanical compression recovery properties and the degradation behavior of biodegradable silicon-covered magnesium alloy stent were tested in vitro.A total of 30 healthy Holland rabbits were randomly divided into silicon-covered magnesium alloy stent group (n=15) and control group (n=15).For rabbits in the silicon-covered magnesium alloy stent group fluoroscopy-guided insertion of the stent into the lower third segment of esophagus was conducted,while for rabbits in the control group no intervention was adopted.One,2 and 4 weeks after the implantation of the stent,esophagography was performed for all rabbits of both groups,and each time every 5 rabbits from both groups were sacrificed,the specimens were collected and sent for histological examinations.Results In vitro test indicated that biodegradable silicon-covered magnesium alloy stent had good flexibility and elasticity,and in phosphate-buffered saline with pH 4.0 or pH 7.4 it degraded more slowly than bare magnesium alloy stent.In vivo test showed that the stent implantation could be well tolerated by all experimental rabbits.Before stent insertion the esophageal diameter was(9.2±0.8) mm,and at one,2 and 4 weeks after stent insertion the esophageal diameters were (9.7±0.7) mm,(9.6±0.8) mm and (9.6±0.5) mm respectively (P＞0.05).In the silicon-covered magnesium alloy stent group,stent displacement occurred in 6 rabbits in one week (n=l),2weeks (n=1) and 4 weeks (n=4).After stent implantation,the tissue reactions such as esophageal wall injury,collagen deposition,etc.were not obviously different from those in the control group (P＞0.05).Conclusion It is technically feasible to insert silicon-covered magnesium alloy stent into the rabbit's esophagus,the stent can provide sufficient support for at least 2 weeks,the stent displacement rate is low and acceptable,and no severe esophageal wall injury and collagen deposition are observed.
ABSTRACT
Objective To investigate the regulatory effect of miR-21 on ADAMTS-1 expression in pulmonary fibrosis model. Methods A mouse model of pulmonary fibrosis was established using bleomycin (BLM) anda model of pulmonary fibrosis was constructed in vitro , the expression level of miR-21 was measured by quantitative real-time polymerase chain reaction (qRT-PCR), while the protein expression of ADAMTS-1 was measured by Western blot. NIH3T3 were transfected with miR-21 mimics and inhibitor in vitro and the cellular expression of ADAMTS-1 was measured by Western blot. Results Compared with the blank group , in mouse models of pulmonary fibrosis , the miR-21 expressions in lung tissues at three time points after BLM-treatment were significantly up-regulated while an evident decrease in ADAMTS-1 expressions were observed (P < 0.01). In vitro pulmonary fibrosis model , NIH3T3 cells after TGF-β1 in concentration 5 μg/L stimulation down-regulated ADAMTS-1 expression and up-regulated miR-21 expression (P < 0.01). NIH3T3 transfected with miR-21 mimics and inhibitor, up-regulated miR-21 expression, while down-regulated ADAMTS-1 protein expression. Conclusions Up-regulation of miR-21 and Down-regulation of ADAMTS-1 might be involved in the progression of pulmonary fibrosis model; miR-21 could negatively regulate ADAMTS-1 expression.