Dry eyes and contact lens wear often cause foreign body sensation. This abnormal mechanosensation is associated with ?Lid Wiper Epitheliopathy? (LWE), a condition induced by the mechanical damage to the marginal palpebral conjunctiva (also known as ?lid wiper?). However, the underlying neurosensory mechanism remains elusive. We recently found that a population of primary sensory neurons defined by the expression of MrgprD selectively innervates the lid wiper and is sensitive to shear force. This proposal aims to determine whether MrgprD-expressing sensory fibers mediate ocular mechanosensation and regulate lacrimation.
In Aim 1, we will characterize the innervations and mechanosensitivity of MrgprD-expressing sensory fibers in the lid wiper. Using genetic labeling and axonal tracing approaches, we will perform detailed anatomical analysis of organization and terminal ultrastructure of MrgprD-expressing sensory fibers in the lid wiper. In addition, we will test whether MrgprD-expressing sensory fibers in the lid wiper can be activated by shear force by conducting ex vivo calcium imaging. These studies will shed light on the role of MrgprD-expressing sensory fibers in ocular mechanosensation.
In Aim 2, we will further determine whether MrgprD-expressing sensory fibers sense shear force during eye movements. We will determine whether genetic ablation or pharmacological silencing of MrgprD-expressing neurons alleviates the ocular mechanosensation induced by enhanced shear force. This study will provide insight on the neurosensory mechanism of the lid wiper mechanosensation.
In Aim 3, we will determine whether the lid wiper mechanosensation regulates lacrimation to maintain the lubrication of the ocular surface. Specifically, we will examine whether ablation of MrgprD-expressing sensory fibers affects basal lacrimation and mechanically-induced lacrimation. Furthermore, we will test whether chemogenetic activation of MrgprD-expressing sensory fibers in the lid wiper promotes lacrimation. Finally, we will determine whether pharmacological activation of MrgprD-expressing sensory fibers is a potential therapeutic strategy for promoting lacrimation under dry eye conditions. These studies will reveal the neural basis of ocular mechanosensation associated with physiological tear evaporations and pathological dryness of the ocular surface, which will have a significant impact in our understanding of ocular mechanosensation as a protective mechanism and its clinical implication in dry eye treatments.

Public Health Relevance

Despite the clinical importance, the neural mechanisms of abnormal mechanosensation associated with dry eyes or contact lens wear remain unknown due to a lack of knowledge about primary mechanosensitive fibers involved. This proposal will characterize the role of MrgprD-expressing sensory fibers in mediating ocular mechanosensation and their regulation of lacrimation. These studies will not only advance our understanding of ocular sensation of dryness at the molecular and cellular levels, but will also provide a new neuronal target for promoting lacrimation under dry eye conditions.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY024704-06A1
Application #
10051912
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Mckie, George Ann
Project Start
2014-07-01
Project End
2025-06-30
Budget Start
2020-08-01
Budget End
2021-06-30
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Washington University
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Huang, Cheng-Chiu; Yang, Weishan; Guo, Changxiong et al. (2018) Anatomical and functional dichotomy of ocular itch and pain. Nat Med 24:1268-1276
Espino, Samuel S; Robinson, Samuel D; Safavi-Hemami, Helena et al. (2018) Conopeptides promote itch through human itch receptor hMgprX1. Toxicon 154:28-34
Luo, Jialie; Feng, Jing; Yu, Guang et al. (2018) Transient receptor potential vanilloid 4-expressing macrophages and keratinocytes contribute differentially to allergic and nonallergic chronic itch. J Allergy Clin Immunol 141:608-619.e7
Yang, Jee Myung; Li, Fengxian; Liu, Qin et al. (2017) A novel TRPM8 agonist relieves dry eye discomfort. BMC Ophthalmol 17:101
Dong, Peter; Guo, Changxiong; Huang, Shengxiang et al. (2017) TRPC3 Is Dispensable for ?-Alanine Triggered Acute Itch. Sci Rep 7:13869
Sun, Shuohao; Xu, Qian; Guo, Changxiong et al. (2017) Leaky Gate Model: Intensity-Dependent Coding of Pain and Itch in the Spinal Cord. Neuron 93:840-853.e5
Oetjen, Landon K; Mack, Madison R; Feng, Jing et al. (2017) Sensory Neurons Co-opt Classical Immune Signaling Pathways to Mediate Chronic Itch. Cell 171:217-228.e13
Huang, Cheng-Chiu; Kim, Yu Shin; Olson, William P et al. (2016) A histamine-independent itch pathway is required for allergic ocular itch. J Allergy Clin Immunol 137:1267-1270.e6
Liu, Qin; Dong, Xinzhong (2015) The role of the Mrgpr receptor family in itch. Handb Exp Pharmacol 226:71-88