Inhibitory effect of epigallocatechin gallate on human Tenon fibroblasts and its mechanism

Objective

To investigate the effect of epigallocatechin gallate (EGCG) on the activation of human Tenon fibroblasts (HTFs) and its mechanism.

Methods

Tenon capsule tissues from nine eyes of nine advanced primary open angle glaucoma patients during trabeculectomy were obtained for primary cell culture.HTFs harvested were identified by immunofluorescence staining for vimentin and keratin.Cells at passage 4-6 were used for experiment.Viability of HTFs treated with EGCG at 0, 10, 20, 30, 40, 50, 60, 70 and 80 μmol/L was detected by cell counting kit-8 (CCK-8) assay.The cells were divided into blank control group, transforming growth factor (TGF)-β1-induced group, and EGCG-treated group, which were cultured in normal medium, medium containing 10 ng/ml TGF-β, medium containing 10 ng/ml TGF-β+ 50 μmol/L EGCG, respectively.The proliferation rate of HTFs was detected by BrdU labeling assay.Cell migration was observed by scratch wound healing assay.The expression of α-smooth muscle actin (α-SMA) was measured by immunofluorescence staining.The protein relative expression levels of Smad2/3, phosphoinositide-3-kinase (PI3K), protein kinase B (Akt) as well as the phosphorylated Smad2/3 (p-Smad2/3) and phosphorylated Akt (p-Akt) were measured by western blot.This study was approved by the Ethics Committee of Guangdong Provincial People’s Hospital (NO.GDREC2019331H[R1]).

Results

The HTFs harvested had spindle shape, grew regularly and were vimentin-positive.CCK-8 assay showed that there was no significant difference in the variability of HTFs treated with EGCG at 10, 20, 30, 40 and 50 μmol/L in comparison with 0 μmol/L EGCG treatment (all at P<0.05). BrdU labeling assay showed that cell proliferation in the TGF-β1-induced group was (66.37±12.65)%, which was significantly higher than (14.75±12.33)% in EGCG-treated group (P<0.05). Three days after scratch, the relative scratch area in the TGF-β1-induced group was (47.33±12.22)%, which was significantly lower than (92.67±4.04)% in the EGCG-treated group (P<0.05). Immunofluorescence assay showed that α-SMA fluorescence was significantly enhanced in the TGF-β1-induced group in comparison with the blank control group, which was reduced to blank control group level in EGCG-treated group.Western blot analysis showed that there were significant differences in the relative expression levels of p-Smad2/3, PI3K and p-Akt protein among the various groups (F=58.820, 121.153, 69.289; all at P<0.001). The relative expressions of p-Smad2/3, PI3K and p-Akt in the TGF-β1-induced group were significantly higher than those in the blank control group, 10 μmol/L and 50 μmol/L EGCG-treated groups (all at P<0.05).

Conclusions

EGCG can suppress TGF-β1-induced HTFs activation through Smad and PI3K/Akt signaling pathways.

Glaucoma; Trabeculectomy; Epigallocatechin gallate; Tenon fibroblasts; Scarring