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Low fucosylation defines the glycocalyx of progenitor cells and melanocytes in the limbal epithelial stem cell niche

ABSTRACT: It is widely recognized that the glycocalyx has significant implications in regulating the self-renewal and differentiation of adult stem cells. Yet, its composition remains poorly understood. Here, we show that the fucose-binding Aleuria aurantia lectin (AAL) binds differentially to basal cells in the stratified epithelium of the human limbus, hair follicle and meibomian gland duct. Using fluorescence-activated cell sorting in combination with single-cell transcriptomics, we find that most epithelial progenitor cells and melanocytes in the limbus display low AAL staining (AALlow) on their cell surface, an attribute that is gradually lost in epithelial cells as they differentiate into mature corneal cells. AALlow epithelial cells were enriched in putative limbal stem cell markers and displayed high proliferative potential. Further analyses revealed that AALlow epithelial cells had reduced expression of GDP-mannose-4,6-dehydratase, an enzyme catalyzing the first and regulatory steps in the de novo biosynthesis of GDP-fucose, and that inhibition of fucosylation using a small-molecule fucose analogue stimulated the proliferative potential of limbal epithelial cells ex vivo. These results provide critical insights into the composition of the glycocalyx in adult stem cells and could thereby have implications to the regeneration of the human limbal stem cell niche.

ORGANISM(S): Homo sapiens

PROVIDER: GSE250294 | GEO | 2024/12/19

REPOSITORIES: GEO

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Project description:Limbal stem cells including epithelial and stromal/Mesenchymal stem cells that contribute to sustained corneal homeostasis, maintain their ability to act as self-renewal progenitor cells by virtue of their limbal niche and intercellular communication. Extracellular vehicles (EVs), including exosomes (Exos), are important paracrine mediators through their cargo transfer for intercellular communication in various stem cell niches. Previously we have shown the differential cargos and regulatory roles of limbal stromal cell (LSC)-derived Exos, in limbal epithelial cells (LEC) in normal (N) and diabetic (DM) limbal niche. In the present study, to have a comprehensive knowledge of reciprocal LEC-LSC crosstalk, we investigated the proteomics and miRNA profile of exosomes derived from LEC and their regulatory roles in LSC in N and DM limbus. Our study showed wound healing and proliferation rates in primary N-LSC were significantly enhanced upon treatment by normal LEC-derived Exos (N-Exos), but not by diabetic Exos (DM-Exos). Further, N-Exos treated LSC showed downregulation of keratocyte markers, ALDH3A1 and lumican, but not keratocan, and upregulation of MSC markers, CD105, CD90, and CD73 compared to the DM-Exos treated LSC. Using next generation sequencing (NGS) and proteomics analysis, we revealed some miRNAs and proteins in the Exos that affect the cellular crosstalk and the function of the cornea. We also documented differences in DM vs. normal LEC-derived Exo’s cargos. Overall, DM-Exos have less effect on LSC proliferation, wound healing, and stem cell maintenance than N-Exos, likely by transferring their cargo proteins and/or regulatory miRNAs targeting cell cycle, ERK/MAPK, TGF-β, EMT, PI3K-Akt-mTOR signaling molecules. This suggests that the small RNA and protein cargo differences in DM vs. N LEC-derived Exos could contribute to the disease state. Our study revealed a complex contribution of Exos to health and diabetic state of corneal homeostasis and suggests the potential of EV therapeutics for diabetic cornea regenerative medicine

Project description:Limbal stem cells (LSCs), known as corneal epithelial stem cells, are located at the basal epithelial layer of the corneal limbus and serve an important function in maintaining the homeostasis of the corneal epithelium. Several putative molecular markers of LSCs have been previously identified. However, the specificity of these markers remains largely controversial. To address this gap in the current understanding of LSCs, we performed a transcriptome profiling of heterogeneous corneal limbal basal cells using single-cell transcriptomics technology to identify LSCs and their exclusive markers. We isolated limbal basal cells from two young donors, constructed scRNA-seq libraries, generated RNA-sequencing data using the 10x Genomics platform, and then finally obtained the transcriptome of about 18,000 individual single-cells using Cell ranger (https://10xgenomics.com). Next, we performed quality control, filtering and data integration using Seurat package (https://satijalab.org/seurat), about 16,400 cells were retained for further downstream analysis such as dimensional reduction, unsupervised clustering, and Differentially expressed gene selection, trajectory analysis and visualization. We identified 11 unique clusters of cells assigned to a putative cell type based on published known biomarkers for differentiation, proliferation and putative epithelial stem cells. As a results, we found 2 Terminally Differentiated Cell (TDC), 3 Post-Mitotic Cell (PMC), 1 Transient Amplifying Cell (TAC), 2 Limbal Progenitor Cell (LPC), Putative Limbal Stem Cell (LSC) and 2 Melanocyte (MC) sub-cell type clusters. Furthermore, we confirmed the trajectory order of LSC differentiation for 9 clusters using Pseudotemporal and Functional PCA analysis. Lastly, we validated each assigned cell subtypes and determined their location in human corneal limbus tissue with 9 markers using RNAscope We were able to reveal the heterogeneity of corneal limbal basal epithelium by defining novel dynamic trajectories for cell types in a pseudotemporal manner. This approach allowed us to identify the distinct clusters of LSCs and progenitors with exclusively expressed markers, and might apply for translational research on regenerating a normal corneal epithelium and restoring vision.

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Low fucosylation defines the glycocalyx of progenitor cells and melanocytes in the limbal epithelial stem cell niche

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