[Effects of Wnt/beta-catenin signaling on the phenotype change of human dermal fibroblasts and its mechanism].

OBJECTIVE: To study the role of Wnt/beta-catenin signaling in the phenotype change of normal skin fibroblasts (NFb) into myofibroblasts and the underlying mechanism.

METHODS: NFb were isolated by collagenase digestion and cultured. (1) Experiment one. NFb were divided into four groups according to the random number table. Cells in control group were cultured with serum-free DMEM nutrient solution (briefly called nutrient solution). Cells in TGF-beta1 group were cultured with nutrient solution containing 10 ng/mL recombinant human TGF-beta1 (the same concentration for following experiments). Cells in Wnt3a group were cultured with nutrient solution containing 150 ng/mL Wnt3a (the same concentration for following experiments). Cells in TGF-beta1 + Wnt3a group were cultured with nutrient solution containing TGF-beta1 and Wnt3a. The mRNA and protein expression levels of beta-catenin and alpha-smooth muscle actin (alpha-SMA) were determined by real-time fluorescent quantitative PCR and Western blotting at post culture hour (PCH) 48. (2) Experiment two. NFb were divided into four groups according to the random number table. Cells in control group and TGF-beta1 group were treated as those in the corresponding groups in experiment one. Cells in SB415286 (glycogen synthase kinase-3beta inhibitor) group were cultured with nutrient solution containing 10 micromol/L SB415286 (the same concentration for following experiments). Cells in TGF-beta1 + SB415286 group were cultured with nutrient solution containing TGF-beta1 and SB415286. The mRNA and protein expression levels of alpha-SMA were determined by real-time fluorescent quantitative PCR and Western blotting, and the alpha-SMA-positive myofibroblasts were detected by immunofluorescence cytochemical staining at PCH 48. The experiments were all repeated for three times. Data were processed with analysis of variance and LSD- t test.

RESULTS: (1) Experiment one. There was no statistically significant difference among four groups in beta-catenin mRNA level (F = 0.302, P = 0.823). There were statistically significant differences among four groups in beta-catenin protein level (F = 16.713, P = 0.001). The protein level of beta-catenin was higher in TGF-beta1 group (0.73 +/- 0.12) and Wnt3a group (0.82 +/- 0.17) than in control group (0.34 +/- 0.11, with t values respectively 3.028, 3.727, P < 0.05 or P < 0.01). The protein level of beta-catenin in TGF-beta1 + Wnt3a group (1.23 +/- 0.21) was higher than that of the other three groups (with t values respectively 6.911, 3.883, 3.184, P values all below 0.01). There were statistically significant differences among four groups in alpha-SMA mRNA level (F = 31.830, P = 0.001). Compared with that of control group, the expression level of alpha-SMA mRNA was up-regulated in TGF-beta1 group and down-regulated in Wnt3a group (with t values respectively 6.759, 2.535, P < 0.05 or P < 0.01). The expression level of alpha-SMA mRNA in TGF-beta1 + Wnt3a group was lower than that of TGF-beta1 group (t = 4.532, P < 0.01). The protein levels of alpha-SMA in control, TGF-beta1, Wnt3a, and TGF-beta1 + Wnt3a groups were respectively 0.83 +/- 0.17, 1.43 +/- 0.20, 0.53 +/- 0.12, and 0.89 +/- 0.14 (F = 16.597, P = 0.001). Compared with that of control group, the protein level of alpha-SMA was up-regulated in TGF-beta1 group and down-regulated in Wnt3a group (with t values respectively 4.582, 2.291, P < 0.05 or P < 0.01). The protein level of alpha-SMA in TGF-beta1 + Wnt3a group was lower than that of TGF-beta1 group (t = 4.123, P < 0.01). (2) Experiment two. There were statistically significant differences among four groups in alpha-SMA mRNA level (F = 34.101, P = 0.001). The alpha-SMA mRNA level in SB415286 group was lower than that of control group (t = 2.511, P < 0.05). The alpha-SMA mRNA level in TGF-beta1 + SB415286 group was lower than that of TGF-beta1 group (t = 3.587, P < 0.01). There were statistically significant differences among four groups in alpha-SMA protein level (F = 11.381, P = 0.003). The alpha-SMA protein level was lower in SB415286 group than in control group (t = 2.364, P < 0.05). The alpha-SMA protein level was down-regulated in SB415286 +TGF-beta1 group as compared with that of TGF-beta1 group (t = 2.556, P < 0.05). There were few alpha-SMA-positive fibroblasts in control group. Compared with that of control group, the expression of alpha-SMA was significantly increased in TGF-beta1 group (t =11.198, P < 0.01), and the expression of alpha-SMA was down-regulated in SB415286 group. Meanwhile, the expression of alpha-SMA in TGF-beta1 + SB415286 group were significantly lower than that of TGF-beta1 group (t = 5.902, P < 0.01).

CONCLUSIONS: The Wnt/beta-catenin signaling might be involved in the fibroblasts-myofibroblasts transition, and it negatively regulate the TGF-beta1 -mediated profibrotic effects.