Effect of Smurf2 on Smad7, a negative regulator of TGF-β1 signaling pathway in hypertrophic scar and its mechanism
10.3760/cma.j.issn.1009-4598.2018.12.016
- VernacularTitle: Smurf2对增生性瘢痕TGF-β1信号通路负向调节因子Smad7的影响及调控机制
- Author:
Changling LIU
1
;
Zhi ZHANG
;
Zhihe LIU
;
Bin CHEN
;
Wenbin TANG
;
Wenjuan CAO
;
Xiaojian LI
Author Information
1. Department of Burn and Plastic Surgery, Guangzhou Red Cross Hospital, Medical College, Ji′nan University, Guangzhou 510220, China
- Publication Type:Journal Article
- Keywords:
Transforming growth factor β
1;
Hyperplastic scar;
Smurf2;
Smad7
- From:
Chinese Journal of Plastic Surgery
2018;34(12):1059-1069
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the effect and regulatory mechanism of Smurf2 on the negative regulator Smad7 of TGF-β1/Smad signaling pathway in hypertrophic scar fibroblasts.
Methods:From January to October 2014, 8 patients with hypertrophic scar after burn were admitted. The age of patients ranged from 1 year 8 months to 7 years, and the time of scar hyperplasia ranged from 2 to 12 months. The residual normal skin of the same patient was used as the control. The fibroblasts were isolated from hypertrophic scar and normal skin respectively and cultured. The third to fifth passage cells were used for the experiments. ① The protein expression of Smad7 in the two groups was detected by Western Blot. ② Hypertrophic scar fibroblasts and normal skin fibroblasts were treated with exogenous TGF-β1 at concentration of 10 ng/ml for 0 min, 5 min, 15 min, 30 min, 1 h, 2 h and 12 h. The expression of Smad7 protein and mRNA were detected by Western Blot and RT-PCR, respectively. ③ The cell lysates of the two groups were collected and incubated with the ubiquitin mixture for 1 h, 2 h and 6 h at 37℃, respectively. The degradation level of Smad7 protein was detected by Western Blot. ④ The cell lysate of hypertrophic scar fibroblasts was collected and incubated with ubiquitin mixture with or without proteasome inhibitor (MG132: MG115=1: 1) to study its inhibitory effect on the degradation of Smad7 in vitro. ⑤ Immunoprecipitation (IP) technique was used to detect the interaction between Smad 7 and E3 ubiquitin ligase Smurf2 in hypertrophic scar fibroblasts. ⑥ The expression of Smad7 protein in hypertrophic scar fibroblasts stimulated by TGF-β1 after Smurf2 silencing by small interference RNA (siRNA) technique were detected by Western blot.
Results:① There was no significant difference in the expression level of Smad7 protein between hypertrophic scar and normal skin fibroblasts(t=0.76, P=0.46). ② Expressions of Smad7 mRNA and protein in normal skin fibroblasts stimulated by exogenous TGF-β1 gradually increased in a time-dependent manner(P<0.05). The expression of Smad7 mRNA in the hypertrophic scar fibroblasts increased at all-time points except at 5min , (P<0.05), while there was no significant difference in the expression level of Smad7 protein at all-time points with or without TGF-β1 stimulation(P>0.05). ③ Degradation of Smad7 protein was enhanced in hypertrophic scar fibroblasts (the expression level of Smad 7 protein at each time point was compared with that of the control group and the last time point, P<0.05), while there was no significant difference in Smad7 protein degradation in normal skin fibroblasts(P=0.162). ④ Enhanced degradation of Smad7 in hypertrophic scar fibroblasts was blocked by the addition of the proteasome inhibitors MG132/MG115. ⑤ In hypertrophic scar fibroblasts, the Smurf2-Smad7 complex was detected, which indicated the interaction between Smurf2 and Smad7 in hypertrophic scar fibroblasts. ⑥ The expression of Smad7 protein was not increased in the hypertrophic scar fibroblasts stimulated by TGF-β1, whereas the stimulation of TGF-β1 increased the expression of Smad7 protein after silencing of Smurf2 gene expression.
Conclusions:In the hypertrophic scar fibroblasts, Smurf 2 attenuates the inhibitory effect of Smad 7 on TGF-β1 signaling pathway through the degradation of Smad7 by ubiquitination, which may be involved in the formation of hypertrophic scar.
