The Role Of BMP-2 During Refractive Development And Form-deprivation Myopia Development In The C57BL/6 Mice

PURPOSE This study was to identify the presence of BMPs in normal C57BL/6 mouse sclera and retina investigate the role of BMP-2 in sclera during FDM development and refractive development.METHODS Ninety-eight 21 days C57BL/6 mouse were divided into 7d FDM group (n=16),7d normal control group(n=16); 21d FDM gourp(n=16),21d normal control group (n= 16); 28d FDM group (n= 16),28d normal control group (n=16) and 2 normal mouse were used for immunofluorescence. FDM models were established by sutured 0.5-ml PCR plastic tubes to the skin surrounding the right eye for 7 days、21 days and 28 days. In FDM group, and the fellow eyes served as the control eyes. The normal control groups were free of all the treatment, but the same measurements were performed at the same time-point. Diopter and axial of all eyes was tested by retinoscopy optometry and vernier calipers at the end of the time-points, immunofluorescence, immunohistochemical staining and quantitative real-time (QRT-PCR) were applied to investigate the expression of BMP-2 protein and mRNA of retina and sclera.RESULTS On 7 days, there is no significant difference between each group in refraction diopter and axial length (P>0.05). On 21 days after occluding of unilateral eyes, the refraction diopter of the experimental group was(+1.93±0.68)D, and that of the fellow eyes was(+6.76±0.62)D, showing a significant difference between them(t=2.514, P=0.018). Axial length was(3.16±0.028)Film in the experimental group, (3.13±0.032)mm in the fellow eyes and(3.12±0.031)mm in the normal control group, showing a significant increase in the experimental group compared with the fellow eyes and normal control group(t=2.230, P=0.023; t=2.084, P =0.013). On 28days the experimental group developed (-7.40D±0.27) D myopia compare to the control group, and the axial length increased (21±13) μm. The morphological observation of sclera found that the sclera collagen fiber arrangement of FDM eyes was disorderd and the sclera became thinner. The result of immunofluorescence showed that the retin and scleral express BMP-2. The expression of BMP-2 in the retina and sclera in exprimental eyes were significantly decreased than those in the controls after monocular deprived 28 days(P< 0.05).CONCLUSION. The normal eyes of C57BL/6 mice progressed to more hyperopic refractive errors with age, and the expression of BMP-2 shows no changes in normal refractive development. While in form-deprivation myopia, the expression of BMP-2 in experiment eyes was down-regulated, suggested that BMP-2 likely to be involved in the development of myopia as a protective signal transduction factor. It may participate in the progress of sclera remodeling process by regulated the synthesis of collagen. Form-deprivation myopia may influence the BMP/TGF-β signaling pathways to limited the protective effect of BMP-2 in sclera remodeling. Further study still needs to be done on the mechanism of BMP-2 in refractive development and the sclera remodeling in form-deprivation myopia development...