Wnt3a-induced proliferation in human lens epithelial cell and its mechanism

Background Aberrant proliferation of residual lens epithelial cells (LECs) is one of main causes of posterior capsular opacification (PCO).Researches indicated that Wnt3a signaling pathway promote proliferation of epithelial cells,but its effect on LECs is still unclear. Objective The present study was to investigate the effects of Wnt3a on proliferation of human LECs and its mechanism and to provide a new gene target in the prevention and treatment of PCO. Methods Human LECs line (SRA01/04 cells ) was cultured and then incubated to 6-well plate at the density of 4×105/well.A human Wnt3a cDNA expressing vector targeted human LECs was constructed to increase the Wnt3a expression in SRA01/04 cells,and pcDNA3-HA expression vector was used as the control group.The expression of Wnt3a was identified by Western blot assay after transfected.The growth and proliferation of SRA01/04 cells were detected by MTT and flow cytometry (FCM).The expressions of β-catenin,cyclin D1 and c-myc in the cells were detected by Western blot assay.β-Catenin expression was localized using immunofluorescence assay,and the expression and localization of proliferating cell nuclear antigen ( PCNA ) were analyzed by immunocytochemistry for the exploration of the active mechanism of Wnt3a to proliferation of LECs.Results Human Wnt3a cDNA expression vector was designed successfully and transiently transfected to SRA01/04 cells,and Wnt3a/SRA01/04 cells and pcDNA3-HA/SRA01/04 cells were obtained.The expression of Wnt3a was verified in the Wnt3a transfected group compared with the control group.MTT indicated that the cell proliferating rate was significantly different between the Wnt3a transfected group and the control group ( Fgroup =15.235,P =0.005 ;Ftime =369.677,P =0.000),and that in various time points after transfected was significantly different (t =20.843,P=0.001 ;t =26.214,P＜0.001 ;t=25.177,P=0.001 ;t =35.516,P＜0.001 ;t =615.056,P＜0.001 ).The proportion of SRA01/04 cells in G1 phase was 51.74％ in the Wnt3a cDNA transfected group,with a significantly decrease in comparison with 79.44％ of the control group.However,the proportion of SRA01/04 cells in S phase in the Wnt3a cDNA transfected group was higher than that of the control group (36.23％ versus 12.34％ ).The positive expression rate of PCNA protein in SRA01/04 was (47.00％ ±7.58％ ) in the Wnt3a cDNA transfected group and ( 16.00％ ±3.61％ ) in the control group with a significant difference between them (t =8.256,P＜0.01 ).After 48 hours of transfection of the Wnt3a cDNA,the expression amount of β-catenin proteins was higher and the immunofluorescence was stronger in cell nucleus,and the expressions of cyclin D1 and c-myc proteins were elevated in Wnt3a/SRA01/04 cells. Conclusions The overexpression of Wnt3a activates the Wnt/β-catenin signaling pathway and downregulates the expression of a subset of target genes,including cyclin D1 and c-myc,which plays an important role in promoting the proliferation of human LECs. Key words: Wnt signal pathway;  Lens epithelial cell;  Cell proliferation;  Posterior capsular opacification