骨形态发生蛋白及其信号通路在近视后巩膜重塑中的作用及机制研究

The mechanism of sclera remodeling has long been the focus of myopia investigation. The sclera is now known to undergo constant remodeling throughout life, and this remodeling can be dramatically altered by changes in the visual environment, producing changes in ocular size and refractive state. Therefore, studying the mechanisms of sclera remodeling, reversing myopia-associated scleral extracellular matrix remodeling events would be warranted, particularly in cases of high myopia in humans. Recent studies have found that human sclera still retained chondrogenic potentia and proteoglycan synthesis rate of age-related changes are also consistent with the changes in articular cartilage. Therefore, the growth factors that regulating cartilage may also regulate the growth of sclera. Bone morphogenetic protein (BMP), known as the "body morphogenetic protein", is one of the most powerful growth factor that affect the extracellular matrix remodeling. We have confirmed various of BMPs expressed in human sclera and might play an important role in form-deprivation myopia scleral remodeling. In this study, we continued to investigate its signal pathway, rationship to retinoid acid, and effects on scleral fibroblasts differentiation, proliferation, extracellular matrix and cell biomechanics characters. Finally we implanted BMP pellets around the poterior sclera of guinea pigs to observe its effects on form-deprivation myopia, and to determine the effects by histological, biomechanical and molecular biology methods. The results of our research would open a new way in treatment of myopia.

巩膜重塑的机制一直是近视研究的焦点。最近研究发现人类巩膜仍然保留软骨层的特征,人类巩膜蛋白多糖合成率的年龄相关性变化也与关节软骨的变化一致,提示调节软骨生长的细胞因子可能也在巩膜中表达并调控巩膜的生长。骨形态发生蛋白（BMP）是影响细胞外基质重塑的最有力的生长因子之一,被誉为"体形态发生蛋白"。我们前期研究发现人类巩膜表达多种BMP,并参与了形觉剥夺性近视后巩膜的重塑。在此基础上我们通过动物模型、细胞培养进一步观察骨形态发生蛋白对巩膜成纤维细胞增殖、分化、细胞外基质、细胞生物力学的作用，探讨其信号转导通路以及与视黄酸信号的关系,明确其在巩膜重塑中的机制，并在实验动物中植入BMP缓释片，观察其对巩膜重塑的作用，通过组织学、生物力学以及分子生物学的方法确定其对实验性近视的影响。本研究成果将为近视的治疗开辟新的途径。

骨形态发生蛋白（BMP）是影响细胞外基质重塑的最有力的生长因子之一，被誉为“体形态发生蛋白”。人类巩膜仍然保留软骨层的特征，人类巩膜蛋白多糖合成率的年龄相关性变化也与关节软骨的变化一致,提示调节软骨生长的细胞因子可能也在巩膜中表达并调控巩膜的生长，而近视最显著的变化就是后巩膜发生重塑。我们研究发现人类巩膜表达BMP-2、BMP-4、BMP-5和BMP-7。通过制作豚鼠形觉剥夺动物模型，研究发现BMP-2和BMP-5参与了形觉剥夺近视后巩膜的重塑，其中BMP-2的变化最大。在体外100ng/mlBMP-2通过经典Smad信号通路明显促进巩膜成纤维细胞的增殖和分化，部分成纤维细胞转化为肌纤维母细胞，细胞外基质胶原蛋白Ⅰ（CollagenⅠ）和蛋白聚糖（Aggrecan）的表达也明显升高。已知视黄酸（RA）是促进眼球增长的最有力生长因子之一，在体外，100ng/mlBMP-2作用于巩膜成纤维细胞，细胞中RA合成酶Aldh1a1、Aldh1a2 和Aldh1a3表达明显降低，这说明BMP-2能够抑制RA信号在巩膜成纤维细胞中的表达。鉴于豚鼠基因库不全，我们选择小鼠形觉剥夺近视模型进一步研究视网膜-巩膜信号通路中Smad1的表达，发现Smad1在形觉剥夺豚鼠近视模型视网膜中的表达随时间进行性下降，Smad1可能通过转导视网膜信号参与了近视发生发展过程。基于以上研究结果，我们在生长期豚鼠后巩膜周围注入BMP-2，观察BMP-2对巩膜组织学以及眼球屈光状态的影响和变化，希望能够通过组织工程学的方法对近视的控制和治疗提供新的方法和思路。该项研究在国内外均属于领先水平。