The Role of Hyaluronan in the Ocular Surface

Purpose: The extracellular matrix (ECM) has a vital role in all tissues of the body, including maintaining ocular surface homeostasis. Hyaluronan (HA) is found in the extracellular matrices of the corneal limbus and meibomian gland (MG). This dissertation evaluated the role of hyaluronan in ocular tissues, particularly in the limbal stem cell niche and the meibomian gland. Methods: (1) To determine the role of HA in the limbal stem cell niche, primary human limbal epithelial stem/progenitor cells were isolated and expanded onto differently coated cultures with or without HA and the yield of limbal epithelial stem cells assessed. (2) To characterize the limbal stem cells niche, the ECM of the mouse corneal buttons and limbal rims was analyzed by various proteomics approaches. (3) To assess the role of HA in age-related meibomian gland dysfunction (ARMGD), Has1-/-;Has3-/- (hyaluronan synthase 1 and 3) knockout mouse Meibomian glands (MGs) were examined as they aged and glandular area, dropout, and atrophy assessed. (4) In order to provide a more translational model of ARMGD to humans, non-human primate (NHP) eyelids at varying ages were assessed and compared to human eyelids. Results: (1) Limbal stem cells cultured onto HA retained their stem cell characteristics such as putative stem cell markers, cell size and roundness, holoclone colony formation capability, and showed decreased senescence over time compared to other coatings. (2) There are differentially expressed ECM genes between the central cornea and limbal region, including higher expression of HA binding proteins TSG-6 and IaI heavy chains in the limbal region. (3) Has1-/-;Has3-/- knockout mice did not show signs of ARMGD at 1yr. of age and minor gland atrophy and dropout at 2yrs. of age in comparison to the wild type mice. (4) The non-human primate presented with symptoms of ARMGD as they aged and present with gland tortuosity and hooking in the lower eyelids. Conclusions: HA was able to maintain limbal stem cell stemness during ex vivo expansion and a specialized HA-rich stem cell niche was found in the limbus. There is also a HA matrix surrounding the MGs of mice which prevented ARMGD. NHPs develop ARMGD similar to humans.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Physiological Optics and Vision Science

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Moreno, Isabel Yi

Advisor dc:contributor.advisor

• Coulson-Thomas, Vivien J

Committee members dc:contributor.committeemember

• Liu, Chia-Yang
• Gesteira, Tarsis F
• O'Brien, John
• Redfern, Rachel

• Physiological optics

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/19953

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/19953