Vitamin D metabolism and function in the cornea and anterior segment

描述（由申请人提供）：据估计，超过50%的美国人口患有维生素D（Vit D）不足。在成千上万的已发表的关于维生素D的研究中，只有少数研究了角膜和眼前节中的维生素D，并且这些研究都没有测量这些部位的维生素D浓度，代谢或活性。全身性维生素D缺乏症可导致或加重眼前节维生素D缺乏症。这可能是角膜损伤后的问题，因为我们的初步数据显示缺乏维生素D受体会导致伤口愈合延迟。我们还证明了维生素D增强角膜上皮屏障功能。除了其在眼睛中可能的免疫作用外，还表明维生素D在眼内压控制和年龄相关性黄斑变性中起作用。在过去的2年里，我们已经进入了这个新的和令人兴奋的研究领域，即检查眼睛前段的维生素D（Vit D）。拟议的项目将继续为未来所有角膜和眼睛的维生素D工作奠定基础。我们的主要假设是，维生素D促进眼睛中的细胞分化，并且维生素D存在于整个眼睛中，并且特异性地转运到泪液中，在泪液中可以影响上皮分化。基于这些假设，本提案的三个具体目的是（1）确定维生素D是否影响角膜上皮分化;（2）检查VDR敲除对角膜上皮伤口愈合的影响;以及（3）确定维生素D如何转运到泪液中。对于目标1，体内实验将检查维生素D受体（VDR）敲除小鼠中的分化标志物。体外实验将检查暴露于不同浓度的25（OH）D3和1，25（OH）2D 3的培养角膜上皮细胞中的分化标志物。我们还将研究occludin和其他维生素D代谢产物在角膜上皮生理学中的作用。对于目标2，将在出生后的不同时间在-/-和-/+ VDR敲除小鼠中检查角膜上皮伤口愈合。相同的组将喂食特殊的补充饮食，并检查角膜上皮伤口愈合。还将在所有这些小鼠中检查连接复合物和分化标志物。在目标3中，将从喂食正常或高维生素D饮食的兔中收集泪液，并测量维生素D代谢产物。将在所有样本中测定维生素D结合蛋白以及megalin和cubilin（其他重要的维生素D蛋白载体），以确定可能的维生素D转运途径进入眼室。

DESCRIPTION (provided by applicant): It is estimated that more than 50% of the United States population has vitamin D (Vit D) insufficiency. Of the tens of thousands of published studies devoted to Vit D, less than a handful have examined Vit D in the cornea and anterior segment and none of these measured Vit D concentrations, metabolism, or activity at those sites. Systemic hypovitaminosis D could lead to or exacerbate anterior segment hypovitaminosis D. This may be of concern following corneal injury given that our preliminary data showing that lack of the vitamin D receptor leads to delayed wound healing. We have also demonstrated that Vit D enhances corneal epithelial barrier function. Apart from its likely immune role in the eye, it has also been suggested that Vit D plays a role in intraocular pressure control and age related macular degeneration. Over the last 2 years we have entered into this new and exciting area of research, namely examining vitamin D (Vit D) in the anterior segment of the eye. The proposed project will continue to lay the foundation for all future Vit D work in te cornea and eye. Our primary hypotheses are that Vit D promotes cell differentiation in the eye, and that Vit D is present throughout the eye and is specifically transported into tear fluid where t can influence epithelial differentiation. The three Specific Aims of this proposal, based on these hypotheses, are (1) Determine if Vit D affects corneal epithelial differentiation; (2) Examine the effects VDR knockout on corneal epithelial wound healing; and (3) Determine how Vit D is transported into the tear fluid. For Aim 1, in-vivo experiments will examine differentiation markers in Vit D Receptor (VDR) knockout mice. In-vitro experiments will examine differentiation markers in cultured corneal epithelial cells exposed to different concentrations of 25(OH)D3 and 1,25(OH)2D3. We will also examine the role of occludin and other Vit D metabolites in corneal epithelial physiology. For Aim 2, corneal epithelial wound healing will be examined in -/- and -/+ VDR knockout mice at different times after birth. Identical groups will be fed a special replenishment diet and corneal epithelial wound healing will be examined. Junctional complexes and differentiation markers will also be examined in all of these mice. In Aim 3, lacrimal fluid wil be collected from the rabbits fed a normal or high Vit D diet and Vit D metabolites will be measured. Vit D binding protein as well as megalin and cubilin (additional significant Vit D protein carriers) will be assayed in all samples to determine possible Vit D transport pathways into the ocular compartments.