Bit1-a potential positive regulator of epithelial-mesenchymal transition in lens epithelial cells.
OBJECTIVE
Posterior capsule opacification (PCO) is a common postoperative complication of cataract surgery. Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is an important initial step of PCO pathogenesis. We have previously shown that Bit1 expresses in rat LECs. In this study, we aim to investigate the role of Bit1 in the EMT of human LECs.


METHODS
The expression of Bit1 was firstly detected in human PCO-attached LECs and human lens cell line SRA01/04 by real-time PCR and immunofluorescence staining. The proliferation and migration of Bit1 knockdown SRA01/04 cells were evaluated by cell counting, wound-healing assay, and transwell migration assay. The EMT of LECs was triggered by TGF-β2, and then the effect of Bit1 on EMT with a key biomarker of α-smooth muscle actin (α-SMA) was analyzed by siRNA knockdown assay, and the reversal of EMT was validated by real-time PCR and western blot.


RESULTS
Bit1 was obviously augmented in LECs derived from PCO tissues and Bit1 expressed with high levels in the cytoplasm of cultured SRA01/04 cells. Cell proliferation, invasion, and migration, as well as α-SMA expression, were significantly decreased in Bit1 knockdown SRA01/04 cells. While TGF-β2 elevated Bit1 and α-SMA expression levels in a dose-dependent manner, with peak levels at 10 ng/ml of TGF-β2 treatment, suppression of Bit1 in SRA01/04 cells reversed the EMT process. TGF-β2 induced elevation of α-SMA expression level, as well as migration, and invasion abilities were all suppressed by Bit1 deficiency.


CONCLUSIONS
These findings reveal that Bit1 promotes TGF-β2 induced α-SMA expression and acts as an positive regulator of EMT. Suppressing Bit1 inhibits the proliferation, migration, and EMT of LECs. Bit1 may be a potential novel therapeutic target for the prevention and treatment of PCO.
Department of Ophthalmology, Shanghai Ninth People's Hospital affiliated Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, China.
Xinhua
X
Wu
Department of Ophthalmology, Shanghai Ninth People's Hospital affiliated Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, China.
Jing
J
Ruan
Department of Ophthalmology, Shanghai Ninth People's Hospital affiliated Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, China. boma1983@hotmail.com.
Bo
B
Ma
Department of Ophthalmology, Shanghai Ninth People's Hospital affiliated Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, China.
Min
M
Luo
D015153:Blotting, Western; D058442:Capsule Opacification / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002265:Carboxylic Ester Hydrolases / Q000096:biosynthesis / Q000235:genetics*; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D004847:Epithelial Cells; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D007903:Lens Capsule, Crystalline / Q000378:metabolism* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics*; D012313:RNA / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction
D024101:Mitochondrial Proteins; D012313:RNA; D002265:Carboxylic Ester Hydrolases; C483418:PTH2 protein, human
Bit1; EMT; LECs; PCO