A central role of estrogen is regulating hydration balance in the body. Decreases in body (systemic) hydration,
cause systemic vocal fold dehydration. Systemic vocal fold dehydration alters the biology of the tissue.
Nevertheless, the importance of estrogens in regulating these biological changes of systemic vocal fold
dehydration remain unknown. We address this important clinical and theoretical issue by investigating the
transcriptome, proteome, tissue morphology, and ultrasonic vocalization outcomes in a study design that
carefully manipulates hormonal state and hydration state. We will also examine the effects of estrogen on the
vascular geometry and blood flow to the larynx following the interaction of systemic dehydration with altered
hormonal states. We use the rat animal model for these studies since this model allows for robust and rigorous
control of hydration and hormonal levels. Because estrogen is important irrespective of biological sex, both
male and female rats will be included. To examine the effects of hormonal loss and replacement, we will
measure outcomes when reproductive organs have been surgically removed (ovariectomized and
orchiectomized rats) and when estrogen replacement with estradiol is delivered. Systemic dehydration will be
induced by a translational paradigm of water restriction for 5 days. Animals with free access to water will serve
as controls for dehydration. Across 16 animal groups, our first goal is to quantify the effects of hormonal loss
on the molecular and histologic signatures of vocal fold dehydration and the influence of estradiol replacement
on these signatures. Because hormone receptors are differentially located across vocal fold mucosa and
muscle, and these tissue layers have distinct cellular organization and biomechanical properties, the vocal fold
mucosa and muscle are examined separately. Our second goal is to investigate the interaction of hormonal
status and dehydration on ultrasonic vocalizations. Our third goal is to examine the influence of hormonal
status and dehydration on vascular geometry, blood flow, and the physiologic consequences of these changes.
By combining molecular, histological, and functional studies, and mechanistic investigations of hemodynamic
modifications, this comprehensive proposal seeks to shed fundamental insight into the effects of estrogens on
vocal fold dehydration biology. These data are needed to drive clinical recommendations pertaining to vocal
fold physiology under conditions of altered hydration and hormonal states.