Objective: To explore the effects of Gremlin on transdifferentiation and extracellular matrix synthesis in cultured human lens epithelium cells (HLEC).
Methods: This is an experimental research. HLEC were incubated with different concentrations of Gremlin (0, 100, 200 and 400 µg/L) for 24 h. The morphological changes of HLEC were observed by inverted microscope. Real-time PCR and Western-Blot were used to evaluate the expression of α-smooth muscle actin (α-SMA) (as a landmark protein of epithelial mesenchymal transition), fibronectin (Fn) and collagen type 1 (COL-1) (as major components of extracellular matrix) after stimulation with different time (0, 12, 24, 48, 72 h) by 200 µg/L Gremlin. The same parameters were observed in Gremlin. siRNA transfected HLEC which treated with 1.0 µg/L TGF-β2. α-SMA, Fn and COL-1 protein and mRNA expressions comparison with control group were analyzed using one-way and two-way ANOVA, while the difference between groups were compared using Turkey HSD and LSD-t test.
Results: The normal morphology of HLEC showed polygonal and anchorage-dependent. After the incubation of different concentrations of Gremlin for 24 h, morphological feature of HLEC were changed from monolayer and polygonal to multilayer and spindle fibroblast-like cells, and the intercellular space widened. The expression of α-SMA, Fn and COL-1 were increased with prolonging of Gremlin treatment time (α-SMA gene induction: 1.00 ± 0.00, 1.62 ± 0.57, 3.40 ± 0.83, 5.90 ± 0.49, 7.97 ± 0.91; F = 61.64, P < 0.05, q = 6.43, 13.13, 18.66, P < 0.05; Fn gene induction: 1.00 ± 0.00, 3.26 ± 0.23, 5.86 ± 0.90, 10.17 ± 2.16, 12.89 ± 1.63; F = 42.03, P < 0.05, q = 6.45, 12.18, 15.79, P < 0.05; COL-1 gene induction: 1.00 ± 0.00, 1.78 ± 0.88, 6.80 ± 0.44, 12.76 ± 2.46, 21.12 ± 3.66; F = 51.79, P < 0.05, q = 4.97, 10.08, 17.26, P < 0.05) (α-SMA protein expression: 0.13 ± 0.02, 0.26 ± 0.02, 0.29 ± 0.09, 0.47 ± 0.06, 0.68 ± 0.05; F = 45.14, q = 5.11, 10.67, 17.40, P < 0.05; Fn protein expression: 0.16 ± 0.04, 0.26 ± 0.07, 0.65 ± 0.03, 0.82 ± 0.04, 0.73 ± 0.02; F = 144.4, q = 20.09, 26.78, 23.12, P < 0.05; COL-1 protein expression: 0.11 ± 0.02, 0.23 ± 0.09, 0.41 ± 0.05, 0.61 ± 0.03, 0.74 ± 0.03; F = 75.47, q = 9.99, 16.60, 21.07, P < 0.05). Gremlin. siRNA transfection effectively suppressed TGF-β2-induced expression of α-SMA, Fn, and COL-I (α-SMA gene induction: F = 81.89, P < 0.05, t = 3.234, 4.346, 10.35; t = 2.252, 7.272, 19.11, P < 0.05; Fn gene induction: F = 83.61, P < 0.05, t = 2.538, 8.202, 11.99; t = 6.316, 7.304, 14.80, P < 0.05; COL-1 gene induction: F = 73.64, P < 0.05, t = 3.385, 7.942, 11.64; t = 4.794, 9.006, 13.75, P < 0.05; Gremlin gene induction: F = 46.11, P < 0.05, t = 5.08, 7.24, 8.27; t = 6.27, 8.27, 12.14, P < 0.05) (α-SMA protein expression: F = 129.6, P < 0.05, t = 4.34, 4.85; 3.83, 4.34; 13.03, 14.82, P < 0.05; Fn protein expression: F = 26.18, P < 0.05, t = 5.68, 5.95; 3.10, 4.06; 4.19, 4.73, P < 0.05; COL-1 protein expression: F = 41.37, P < 0.05, t = 6.93, 5.51; 7.82, 6.93; 8.71, 7.64, P < 0.05; Gremlin protein expression: F = 59.52, P < 0.05, t = 2.24, 3.49; 5.74, 6.23; 6.98, 9.98, P < 0.05).
Conclusions: Gremlin could induce HLEC to express α-SMA, Fn and COL-1 in a time-dependent manner and promote transdifferentiation and extracellular matrix synthesis. Specifically silencing the expression of Gremlin could effectively block the TGF-β2-induced EMT and ECM synthesis in HLEC.