Pathogenesis of Dry Eye in Graft Versus Host Disease (GVHD): Role of Ocular Mucins and Conjunctival Fibrosis
Date of Award
Doctor of Philosophy (PhD)
Surya M. Nauli
Allogenic hematopoietic stem cell transplantation is a procedure that offers a possible cure for hematologic cancers and other hematologic disorders. Unfortunately, despite the increasing survival rate of patients, the quality of their life is adversely affected by the allogeneic bone marrow transplantation’s major side effect i.e Graft vs. Host Disease (GVHD). GVHD is a complex, multi-organ disease resulting from an immunological attack by donor engrafted immune cells to host organs, including the eye surface. Mostly based on the time of disease onset after transplantation, GVHD is divided into the acute and chronic phase. The eyes may be involved in both acute and chronic GVHD, although ocular involvement is more common in the chronic GVHD with a more severe presentation. As high as 40%-60% of patients with chronic GVHD suffer from debilitating ocular surface damage manifesting as severe dry eye and cicatricial conjunctivitis. Several pathological mechanisms likely contribute to the etiology of ocular GVHD-associated dry eye disease. Despite the high frequency of ocular surface involvement in patients experiencing GVHD, little is known about the underlying pathogenesis responsible for ocular GVHD-associated dry eye. In our first manuscript, using a mouse model of allogeneic transplantation, we demonstrated that ocular GVHD causes a decrease in tear film volume and corneal keratopathy. These ocular surfaces changes are accompanied by a significant decrease in the area and thickness of corneal glycocalyx, a decrease in ocular surface mucins, MUC4 and MUC5AC and loss of conjunctival goblet cells. Our data showed that topical treatment by mucin secretagogue, rebamipide, partially attenuates GVHD-associated damage to ocular surface. Hyperosmolar tears are a consistent feature of dry eye disease. Our data demonstrated that hyperosmolar stress increases the gene expression of NFAT5, a tonicity-related transcription factor and pro-inflammatory cytokines (IL1, IL6, TNFα, IFN-γ) in human corneal and conjunctival epithelial cells. Next, we demonstrated that these proinflammatory cytokines differentially modulate the expression of MUC 1, and MUC 4 in ocular surface epithelial cells, but they do not cause any notable change in glycocalyx or apoptotic cell death in stratified human corneal and conjunctival epithelial cells. Immune-mediated ocular surface damage in GVHD can initiate a wound healing response leading to fibrosis in the conjunctiva, a fibroblast-rich tissue. Conjunctival fibrosis may underlie the noted decrease in goblet cells and ocular surface mucins, thus contributing to GVHD-associated dry eye. Our results demonstrated that ocular GVHD causes a significant increase in expression of α-smooth muscle actin (SMA), a marker of myofibroblasts, in the conjunctiva. Immunostaining detected the presence of large number of myofibroblasts in bulbar orbital conjunctiva of GVHD mice. An increase in the components of renin-angiotensin system component (RAS), angiotensinogen and angiotensin converting enzyme, was also noted in the conjunctiva suggesting that ocular GVHD causes conjunctival fibrosis by myofibroblast formation and activation of conjunctival RAS.
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Shamloo, K. Pathogenesis of Dry Eye in Graft Versus Host Disease (GVHD): Role of Ocular Mucins and Conjunctival Fibrosis. [dissertation]. Irvine, CA: Chapman University; 2021. https://doi.org/10.36837/chapman.000230