Inhibitory effect and biological mechanism of Dickkopf-1 on the proliferation of human lens epithelial cells

Objective

To investigate the effects of Dickkopf-1(DKK1) on the proliferation of human lens epithelial cells (LECs) and its possible mechanism in order to search a new target for the treatment of posterior capsular opacification (PCO).

Methods

Human LECs line (SRA 01/04 cells )were divided into Wnt3a overexpression group, DKK1 group and control group.Wnt3a gene expression vector was transfected into SRA 01/04 cells by liposome mediated transfection to establish a PCO model in the Wnt3a overexpression group, DKK1 of 100 μg/ml was added into the medium 48 hours after transfection of Wnt3a gene vector in the DKK1 group, and only pcDNA3-HA vector was transfected in the control group.The survival rate of SRA 01/04 cells was detected with a cell counting kit-8 (CCK-8) assay.The expression rate of proliferating cell nuclear antigen (PCNA) in the cells was detecteds by immunocytochemistry.The expression of β-catenin in the cells was detected and located by immunofluorescence.The expression of Wnt3a CyclinD1 and C-Myc were detected by Western blot assay.

Results

The relative expression of Wnt3a protein in the control group was 0.49±0.07, which was significantly lower than that in the Wnt3a overexpression group (0.84±0.06) (t=3.704, P=0.02). The survival rate in the Wnt3a overexpression group, DKK1 group and control group showed significant difference over time (F_group=10.910, P<0.05; F_time=6.041, P<0.05). The survival rate in the Wnt3a overexpression group was significantly increased in comparison with the control group and that in the DKK1 group was significantly reduced in comparison with the Wnt3a overexpression group(all at P<0.05). β-Catenin was expressed mainly in cytoplasm and cell nucleus in the Wnt3a overexpression group and only in cytoplasm in the DKK1 group. in the control group, β-catenin showed a weaked expression in the cytoplasm and nucleus in comparison with the Wnt3a overexpression group.The expression rates of PCNA protein were (9.4±1.4)%, (43.4±5.4)%, and (14.2±2.3)% in the control group, Wnt3a overexpression group and DKK1 group, respectively, with a significant difference among the groups (F=28.250, P<0.05), and the expression rates of PCNA protein were significantly reduced in the control group and DKK1 group compared with the Wnt3a overexpression group (both at P<0.05). β-Catenin protein were expressed mainly in the cytoplasm and nucleus in the Wnt3a overexpression group and only in the cytoplasm in the control group.In the DKK1 group, the expression of β-catenin protein was weakened in the cytoplasm and nucleus in comparison with the Wnt3a overexpression group.The relative expressions of CyclinD1 were 0.64±0.07、0.84±0.03 and 0.55±0.10, C-Myc were 0.59±0.05、0.93±0.02 and 0.47±0.08 in the control group, Wnt3a overexpression group and the DKK1 group, respectively with significant differences among the groups (F=20.580, 5.040, both at P<0.05). The relative expressions of CyclinD1 and C-Myc in the Wnt3a overexpression group were significantly higher than those in the DKK1 group and the control group (all at P<0.05).

Conclusions

DKK1 inhibits activation of Wnt/β-catenin signaling pathway induced by Wnt3a overexpression in SRA01/04 cells, and down-regulation of downstream target proteins cyclin D1 and C-Mgc may be the biological mechanism of Dkk1 inhibiting human LECs proliferation.

Dickkopf family; Lens epithelial cells; Wnt/β-catenin signal pathway; Cell proliferation; Posterior capsular opacification