Fiber Cell Junctions in Normal and Cataractous Lenses

描述（由申请人提供）：这项竞争性的持续拨款是为了支持对人类年龄相关的核性白内障的进一步分析，核性白内障是最常见的人类白内障，可导致视力下降和全球失明。手术是目前唯一的治疗方法，虽然非常成功，但对医疗保健系统来说是一个重大负担，并且不能解决老年人群中核性白内障的高发问题。长期目标是了解晶状体核中产生过多光散射的细胞生物学变化，以便制定替代策略来预防晶状体混浊的发生或减缓其进展。重点是纤维细胞连接在白内障形成中的作用。在之前的资助期间，重要的进展包括鉴定了直径1-4 5m的颗粒，这些颗粒似乎是围绕着接近球形的细胞质蛋白球的多个薄脂质双层。用共聚焦显微镜、多光子显微镜、亮场显微镜和电子显微镜对这些粒子进行了检测。这些微粒在核性白内障中比年龄匹配的透明供体晶状体中数量更多。建立了一种定量电子吸收的方法来测量局部蛋白质浓度和粒子内部相对于邻近细胞质的折射率。这个比值给出了散射势的度量。根据米氏散射理论，这些球状粒子可能是非常有效的散射中心，产生正向散射，可能影响黄斑处的图像形成。超微结构分析也显示了纤维细胞连接处的许多变化，包括膜成分的丢失、低密度区域（空洞）、细胞外空间的扩大和细胞外空间内的蛋白质沉积。这些变化可能与衰老和白内障形成过程中蛋白质的修饰和再分配有关。观察到细胞质的纹理，可能是基于高分子量聚集体的形成。傅里叶分析用于将纹理的数量与观察到的核不透明联系起来。印度晚期核性白内障患者的这些特征似乎得到了增强，包括多层颗粒的数量。未来的研究包括在从透明的供体晶状体到完全不透明的核性白内障的整个范围内，对各种类型细胞损伤的预测散射量进行表征，从而导致白内障形成的机制。白内障在世界各地非常常见，每年有数百万例手术摘除以矫正白内障引起的视力缺陷和失明。手术是目前唯一有效的治疗方法。我们的目标是了解晶状体细胞在衰老和白内障形成过程中的变化，以便制定和评估预防和治疗的替代策略。

DESCRIPTION (provided by applicant): This competing continuation grant is a request to support further analysis of human age-related nuclear cataracts, the most common form of human cataract that causes visual decline and worldwide blindness. Surgery is the only current treatment, and, while very successful, is a significant burden on healthcare systems and does not address the high incidence of nuclear cataract in aging populations. The long-range goals are to understand the cell biological changes that produce excess light scattering in lens nuclei so that alternative strategies can be devised to prevent the onset or slow the progression lens opacification. The emphasis is on the role of fiber cell junctions in cataract formation. Important progress in the previous grant period includes the identification of 1-4 5m diameter particles that appear to be multiple thin lipid bilayers surrounding nearly spherical globules of cytoplasmic protein. These particles were detected by confocal, multiphoton and bright field light microscopy and by electron microscopy. The particles were found to be more numerous in nuclear cataracts than age-matched transparent donor lenses. A method of quantitative electron absorption was developed to measure the local protein concentration and refractive index of particle interiors compared to adjacent cytoplasm. The ratio gives a measure of the scattering potential. Using Mie scattering theory, these globular particles are potentially very efficient scattering centers producing forward scatter that could affect image formation at the macula. Ultrastructural analysis also demonstrated numerous changes at fiber cell junctions including loss of membrane components, low-density regions (voids), enlargement of extracellular spaces and protein deposits within extracellular spaces. These changes are probably related to protein modification and redistribution during aging and cataract formation. Texturing of the cytoplasm was observed and is probably based on the formation of high molecular weight aggregates. Fourier analysis was used to relate the amount of texturing to the observed opacification of the nucleus. These features appear to be enhanced, including the number of multlamellar particles, in advanced nuclear cataracts from patients in India. Future studies include the characterization of the amount predicted scattering from various types of cellular damage over the entire range from transparent donor lenses to fully opaque nuclear cataracts, thus leading to the mechanism of cataract formation. PUBLIC HEALTH RELEVANCE Cataracts are very common throughout the world and millions of surgical extractions are performed each year to correct visual deficits and blindness caused by cataracts. Surgery at present is the only effective treatment. Our goal is to understand how cells in the lens change during aging and cataract formation so that alternative strategies for prevention and cure can be devised and evaluated.