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.

Public Health Relevance

It is estimated that more than 50% of the United States population has vitamin D (Vit D) insufficiency (2, 4, 5). 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. This work will address some of these topics.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
1R01EY021747-01A1
Application #
8292566
Study Section
Anterior Eye Disease Study Section (AED)
Program Officer
Mckie, George Ann
Project Start
2012-05-01
Project End
2016-04-30
Budget Start
2012-05-01
Budget End
2013-04-30
Support Year
1
Fiscal Year
2012
Total Cost
$374,792
Indirect Cost
$124,792
Name
University of Tennessee Health Science Center
Department
Physiology
Type
Schools of Medicine
DUNS #
941884009
City
Memphis
State
TN
Country
United States
Zip Code
38163
Wan, Debin; Yang, Jun; Barnych, Bogdan et al. (2017) A new sensitive LC/MS/MS analysis of vitamin D metabolites using a click derivatization reagent, 2-nitrosopyridine. J Lipid Res 58:798-808
Lu, Xiaowen; Chen, Zhong; Mylarapu, Namratha et al. (2017) Effects of 1,25 and 24,25 Vitamin D on Corneal Epithelial Proliferation, Migration and Vitamin D Metabolizing and Catabolizing Enzymes. Sci Rep 7:16951
Lu, Xiaowen; Elizondo, Rodolfo A; Nielsen, Rikke et al. (2015) Vitamin D in Tear Fluid. Invest Ophthalmol Vis Sci 56:5880-7
Lu, Xiaowen; Watsky, Mitchell A (2014) Effects of vitamin D receptor knockout on cornea epithelium gap junctions. Invest Ophthalmol Vis Sci 55:2975-82
Elizondo, Rodolfo A; Yin, Zhaohong; Lu, Xiaowen et al. (2014) Effect of vitamin D receptor knockout on cornea epithelium wound healing and tight junctions. Invest Ophthalmol Vis Sci 55:5245-51
Lin, Yanping; Ubels, John L; Schotanus, Mark P et al. (2012) Enhancement of vitamin D metabolites in the eye following vitamin D3 supplementation and UV-B irradiation. Curr Eye Res 37:871-8