The preocular tear film plays a critical role in maintaining ocular surface integrity, protecting against microbial challenge and preserving visual acuity. Tear film dysfunction, in turn, may severely impact the eye and lead to desiccation of the corneal epithelium, ulceration and perforation of the cornea, an increased incidence of infectious disease, and pronounced visual impairment and blindness. Countless people suffer from tear film disorders, which are termed dry eye syndromes and are classified into 2 major types: aqueous-deficient and evaporative. Aqueous-deficient dry eye is due to decreased tear secretion from the lacrimal gland. An example is Sjogren's syndrome, a common autoimmune disease that afflicts primarily women and destroys the lacrimal gland. Evaporative dry eye is typically caused by meibomian gland dysfunction and may be a major cause of dry eye during menopause, use of estrogen hormone replacement therapy (HRT) and aging. The long range objectives of this grant application are to test our hypotheses that: (1) sex steroids are extremely important in the physiological regulation of the lacrimal and meibomian glands, as well as the production of the tear film; and (2) gender, sex steroid hormones, and in particular androgen deficiency, are critical etiologic factors in the pathogenesis of both aqueous-deficient and evaporative dry eye syndromes. Experimental procedures include mouse models, DNA hybridization arrays (i.e. gene chips), RT-PCR, ribonuclease protection assays, Northern, slot and Southern blots, in situ hybridization, cell cultures, immunoassays, HPLC/mass spectrometry, enzyme assays, histology, image analysis, hormone reconstitution experiments, as well as clinical studies with humans.
Our specific aims are to: (1) identify the genes and proteins that mediate the gender-related differences in, and the sex steroid control of, lacrimal glands in normal and autoimmune (i.e. Sjogren's syndrome) mice; (2) identify the genes and proteins involved in the gender-associated variations in, and the sex steroid regulation of, the mouse meibomian gland; and (3) determine the specific effects of HRT use (estrogen, or estrogen plus progesterone), with or without androgen supplementation, on the ocular surface of postmenopausal women. Results from the studies should significantly advance our understanding of the processes by which gender and sex steroids influence the anterior segment of the eye. In addition, findings may have health relatedness for the eye, because they: (1) explore the regulation of the tear film; and (2) may lead to the development of specific therapies for the clinical treatment of dry eye syndromes.
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