Investigating Fucosylation as a Mediator of Limbal Stem Cell Viability

ABSTRACT Limbal stem cells (LSCs) are crucial for maintaining vision. Limbal Stem Cell Deficiency (LSCD) is a potentially blinding condition caused by the death or dysfunction of LSCs. Pronounced local inflammation is a key component of all LSCD etiologies, and recent work has emphasized a key role for Tumor Necrosis Factor Alpha (TNF-α) in LSCD pathophysiology. LSCD has limited treatment options, generally necessitating transplantation which has variable outcomes. To develop novel therapies a more thorough understanding of factors that regulate LSC viability in inflammatory conditions is needed. Among these factors, the glycocalyx, a diverse mixture of cell surface glycans, may significantly influence LSC survival. Fucose, a monosaccharide in the glycocalyx, is abundant in mature, differentiated ocular surface cell types but is remarkably low in LSCs. The relevance of low fucosylation to LSC biology is unknown. I have generated strong preliminary results that suggest low fucose protects LSCs from inflammatory stress and cell death. My preliminary data indicate that fucose synthesis increases in LSCs during inflammatory disease, potentially increasing LSC susceptibility towards cell death. TNF-α receptor 1 (TNFR1), a conditional death receptor, is known to be fucosylated in many cell types. Emerging evidence suggests the receptor relies on fucose modification for cell death induction. Mechanistically, we hypothesize that low fucose in healthy LSCs renders TNFR1 and related molecules inefficient as death receptors, thereby protecting this vital cell type from extrinsic cell death. We will integrate these hypotheses and achieve the goals of this proposal by employing established in vitro and in vivo models of fucose deficiency to assess LSC viability and corneal regeneration in human and mouse limbal epithelial cells (Aim 1). Additionally, we will describe how fucose deficiency affects TNF-α:TNFR1 promoted death signaling in limbal epithelial cells (Aim 2). The proposed work will determine a role for fucose in LSC viability and corneal wound healing. Additionally, it will shed light on the role of fucose on TNFR1 function. Successful completion of the proposal will result in knowledge that would enrich the current understanding of LSC viability and the cornea’s regenerative function, potentially providing a valuable foundation for developing novel therapeutics for LSCD and other ocular inflammatory diseases.