骨形态发生蛋白在形觉剥夺性近视眼后巩膜中表达的变化

Expression of bone morphogenetic protein in sclera of form deprivation myopic eye

背景眼球伸长过程伴随着巩膜的广泛重塑，而这种重塑受多种生长因子的调控。以往的研究证实转化生长因子-β（TGF-β）在近视形成和发展过程中发挥作用。骨形态发生蛋白（BMPs）属于TGF-β超家族，其在近视的发生中是否发挥作用及如何发挥作用尚不清楚。目的观察豚鼠形觉剥夺性近视（FDM）眼后巩膜中BMPs的表达变化，探讨其在近视后巩膜重塑中的作用。方法1～2周龄花色豚鼠30只，以随机数字表法随机分为实验组和正常对照组，每组15只。任意选择实验组豚鼠的一侧眼作为实验眼，应用半透明眼罩连续遮盖14d以建立FDM动物模型，另一侧眼作为对照眼。形觉剥夺前后所有动物眼经检影验光获得屈光度，用A型超声法测量眼轴长度。造模后第15天取豚鼠后巩膜组织，分别用逆转录PCR（RT—PCR）和Westernblot法检测各组豚鼠后巩膜中BMPsmRNA及其蛋白的表达。结果实验14d后，豚鼠遮盖眼的屈光度为（一0．48±0．51）D，与对侧眼的（3．22±0．34）D比较，差异有统计学意义（t=-12．814，P=0．000），与正常对照眼的（2．97±0．70）D比较，差异有统计学意义（t=-11．878，P=0．000）。豚鼠遮盖眼的眼轴长度为（8．30±0．05）mm，明显长于对侧眼的（8．11±0．06）mm和正常对照组（8．06±0．06）mm，差异均有统计学意义（t=7．230、9．084，均P=0．000）。正常豚鼠后巩膜可表达BMP-2、BMP-4、BMP-5mRNA，豚鼠遮盖眼后巩膜中BMP-2mRNA和BMP-5mRNA的相对表达值分别为0．41-±0．11和0．65±0．06，较对侧眼的0．62-±0．07和0．84±0．03分别下降了34．48％和23．67％，差异均有统计学意义（t=2．838，P=0．017；t=2．524，P=0．028）；豚鼠遮盖眼后巩膜中BMP-2和BMP-5蛋白表达的相对值分别为0．44±0．06和0．70-±0．05，较对侧眼的0．61±0．05和0．824-0．03分别下降了23．42％和15．21％，差异均有统计学意义（t=2．465，P=0．030；t=2．445，P=0．031），而形觉剥夺眼与对侧眼后巩膜中BMP-4mRNA及其蛋白相对表达量的差异均无统计学意义（mRNA：t=0．704，P=0．460；蛋白：t=0．987，P=0．365）。结论FDM眼后巩膜中BMP-2和BMP-5的表达下调，提示BMPs在实验性近视后巩膜重塑中可能发挥作用。

Background It is well known that sclera remodeling occurs during axial elongation in myopia under the control of growth hormone or its downstream effectors. The role of transforming growth faetor-~ （TGF-~） in myopia has been determined in previous studies. Bone morphogenetie protein （BMP） is one of members of the TGF-[~ superfamily,hut if it plays an important role in the genesis and development of myopia is not completely clear. Objective This study was to identify the presence of BMPs in normal guinea pigs sclera and investigate the change of BMPs in the sclera in form-deprivation myopia （FDM） of guinea pigs. Methods Thirty young guinea pigs were randomized into normal control group and experimental group using table of random number. FDM models were established by occluding unilateral eyes of guinea pigs with a translucent lens for 14 days in the experimental group, and the fellow eyes served as the controls. Diopter of all eyes was tested by retinoscopy optometry, and ocular axial length was measured by A-sonography before and after modeling. Posterior sclera tissue of the animals was obtained on 14 days,and the relative expression level of BMPs mRNA and protein were assayed by reverse transcription PCR （RT-PCR） and Western blot. The use and care of the animals complied with ARVO Statement. Results On 14 days after occluding of unilateral eyes, the refraction diopter of the experimental group was （ -0.48-±0.51 ） D, and that of the fellow eyes was （3.22-±0.34）D, showing a significant difference between them （t =-12. 814,P = 0. 000）. Also,a significant difference in the diopter was seen between the experimental group and normal control group （[-0.48-±0.51]D vs. [ 2.97-±0.70] D,t = -11.878,P=0.000）. Axial length was （8.30_±0.05）mm in the experimental group, （ 8. 11 _±0.06 ） mm in the fellow eyes and （ 8.06-±0.06 ） mm in the normal control group, showing a significant increase in the experimental group compared with the fellow eyes and normal control group （t = 7. 230,P = 0. 000 ; t = 9. 084, P = 0. 000）. The expressions of BMP-2 mRNA, BMP-4 mRNA, BMP-5 mRNA in posterior sclera were detected in the normal guinea pigs. Fourteen days after the induction of myopia, the relative levels of BMP-2 mRNA and BMP-5 mRNA in sclera were 0.41-± 0.11 and 0.65-± 0.06 in the experimental eyes, which were significantly lower than 0. 62 -± 0. 07 and 0.84 -± 0.03 in the fellow eyes with the descent range of 34.48% and 23.67 % respectively （ t = 2. 838, P = 0.017 ; t = 2. 524, P = 0. 028 ）. The relative values of BMP-2 protein and BMP-5 protein were 0.44-±0.06 and 0.70-±0.05 in the experimental eyes,and those of the fellow eyes were 0. 61-±0. 05 and 0. 82-±0. 03, showing significant decline in the experimental eyes with the lowing range of 23.42% and 15.21%, respectively （t = 2. 465 ,P = 0. 030;t = 2. 445, P = 0. 031 ）. No significant differences were found in the expression of BMP-4 mRNA and protein in posterior selera between the experimental eyes and the normal control eyes （mRNA ：t= 0.704,P=0.460;protein：t= 0.987,P=0.365）. Conclusions The expressions of the BMP-2 and BMP-5 in selera down-regulate significantly in FDM eyes,which suggest that BMP-2 and BMP-5 participate in sclera remodeling during myopia induction.