Abstract:AIM: To investigate the effects of electroacupuncture on scleral remodeling in guinea pigs with experimental myopia based on bone morphogenetic protein 2(BMP2)/Smad signaling pathway.
METHODS:A total of 80 two-week-old healthy guinea pigs were randomly divided into four groups: normal control(NC)group, lens-induced myopia(LIM)group, electroacupuncture(EA)group,and shame electroacupuncture(SHAM)group, with 20 guinea pigs in each group. The right eyes of guinea pigs in the LIM, SHAM, and EA groups had covered with -6.00 D lens to induce myopia. The EA group received electroacupuncture stimulation at the Taiyang and Hegu acupoints, while the SHAM group underwent stimulation at bilateral gluteal non-meridian areas. No intervention was performed on the NC group. Retinoscopy was used to measure the refractive error, and A-scan ultrasonography was used to measure the axial length. The changes in scleral structure were observed using hematoxylin-eosin(HE)staining. Real-time fluorescent quantitative polymerase chain reaction(qPCR)and Western blot(WB)were used to detect the mRNA and protein expression levels of BMP2/Smad signaling pathway-related molecules in the sclera of guinea pigs in each group.
RESULTS: After modeling for 2 and 4 wk, compared with the NC group, the degree of myopia and the axial length were increased in the LIM group(both P<0.05); compared with the LIM group, the degree of myopia and the axial length were decreased in the EA group(both P<0.05). HE staining showed thinned posterior scleral thickness in the LIM group, with a loose and disordered arrangement of collagen fibers. Compared with the LIM group, the posterior scleral thickness in EA group was increased and the collagen fibers were arranged relatively tightly and regularly.qPCR and WB results showed that, at both mRNA and protein relative expression levels, compared with the NC group, the LIM group exhibited significantly decreased expression of Collagen I, BMP2, bone morphogenetic protein type IA receptor(BMPRIA), bone morphogenetic protein type IB receptor(BMPRIB), bone morphogenetic protein type II receptor(BMPRII), Smad family member 1(Smad1), Smad family member 5(Smad5), Smad family member 9(Smad9), Smad family member 4(Smad4), and tissue inhibitor of metalloproteinase-2(TIMP-2), while the expression of matrix metalloproteinase-2(MMP-2)and alpha-smooth muscle actin(α-SMA)was significantly increased. Compared with the LIM group, the EA group showed significantly increased expression of Collagen I, BMP2, BMPRIA, BMPRIB, BMPRII, Smad1, Smad5, Smad9, Smad4, and TIMP-2, and significantly decreased expression of MMP-2 and α-SMA.
CONCLUSION:Electroacupuncture can improve scleral remodeling and histomorphological changes, and inhibit axial elongation by regulating the expression levels of molecules related to the BMP2/Smad signaling pathway in the sclera of guinea pigs with experimental myopia, thereby delaying the onset and progression of myopia.
