Project description: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.
Project description:It is widely recognized that the glycocalyx has significant implications in regulating the self-renewal and differentiation of adult stem cells; however, 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 epithelium, 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 clonogenic capacity. Further analyses revealed that AALlow epithelial cells had reduced expression of GDP-mannose-4,6-dehydratase, an enzyme catalyzing the first and limiting step in the de novo biosynthesis of GDP-fucose, and that inhibition of fucosylation using a small-molecule fucose analog stimulated the proliferative potential of limbal epithelial cells ex vivo. These results provide crucial insights into the distinctive composition of the glycocalyx in adult stem cells and underscore the significance of fucose modulation in the therapeutic regeneration of the human limbal stem cell niche.
Project description:Comprehensive transcriptome analysis of four distinct human limbal compartments, including basal limbal crypts (BLCs), superficial limbal crypts (SLCs), cornea, and the supporting stroma, with the aid of laser capture microdissection and deep RNA sequencing.
Project description:Limbal epithelial stem cell (LESC) deficiency represents a significant clinical problem especially in bilateral cases. Induced pluripotent stem cells (iPSC) may be a promising source of LESC, allowing standardized and continual propagation and banking. The objective of this study was to generate iPSC from human limbal epithelial cultures and differentiate them back into limbal epithelial cells using substrata mimicking the natural LESC niche. Using Yamanaka’s episomal vectors limbal-derived iPSC were reprogrammed from LESC cultured from donor corneoscleral rims and from human skin fibroblasts. A clone from limbal-derived iPSC expressed stemness markers, had a diploid karyotype, and produced teratomas in nude mice representing three germ layers. Compared to parental LESC, this clone had fewer specific gene methylation changes revealed using the Illumina Infinium Methylation 450k Beadchips than compared to skin fibroblasts. The expression of putative LESC markers was examined by quantitative RT-PCR and immunostaining in limbal-derived and fibroblast-derived iPSC cultured on denuded human amniotic membrane or denuded cornea. Limbal-derived iPSC had markedly stronger expression of PAX6, ABCG2, Np63, keratins 14, 15, 17, and N-cadherin than fibroblast-derived iPSC. On denuded corneas, limbal-derived iPSC showed the expression of differentiated corneal keratins 3 and 12. The data suggest that iPSC differentiation to a desired lineage may be facilitated by their generation from the same tissue. This may be related to preservation of parental tissue epigenetic methylation signatures in iPSC and use of biological substrata similar to the natural niche of parental cells. The data pave the way for generating transplantable LESC from limbal-derived iPSC. Bisulphite converted DNA from the 12 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:We profiled over 400 spots within each sample and spatially located major cell types through the integration with reference the single-cell RNA sequencing data. Based on Robust Cell Type Decomposition (RCTD) technology, limbal epithelial stem cells (LESCs) were mainly localized in the basement membrane, and limbal niche cells were predominantly situated within the stromal area. Following, the limbus was divided into 4 regions based on histological structure, and the differential expressed genes among the four regions were analyzed. Notably, our investigation revealed significantly higher levels of GPHB5 and PERP within the epithelium of the middle region, precisely where LESCs predominantly reside. Concurrently, the activation of critical pathways such as "Protein Binding" and "ECM-receptor interaction" were discovered in this same region, underscoring its pivotal role in maintaining the limbal niche. Subsequently, cell-cell communication analysis was conducted on essential cells inside the niche microenvironment. Remarkably, we observed that limbal mesenchymal stem cells exhibit the largest amounts of ligands associated with LESCs, with melanocytes closely trailing behind. The widespread activity of COL6A2/CD44 signaling among limbal mesenchymal stem cells, melanocytes, immune cells, and LESCs, indicate its essential role in mediating bidirectional communication via the Collagen pathway. Additionally, a myriad of ligand-receptor interactions and pathways regulatory crosstalk among diverse cell types were exhibited.
Project description:Cancer secretome is a reservoir for aberrant glycosylation. How therapies alter this post59 translational cancer hallmark and the consequences thereof remain elusive. Here we show that an elevated secretome fucosylation is a pan-cancer signature of both response and resistance to multiple targeted therapies. Large-scale pharmacogenomics revealed that fucosylation genes display widespread association with resistance to these therapies. In both cancer cell cultures and patients, targeted kinase inhibitors distinctively induced core fucosylation of secreted proteins less than 60 kDa. Label-free proteomics of N-glycomes revealed that fucosylation of the antioxidant PON1 is a critical component of the therapy66 induced secretome. Core fucosylation in the Golgi impacts PON1 stability and folding prior to secretion, promoting a more degradation-resistant PON1. Non-specific and PON1-specific secretome deglycosylation both limited the expansion of resistant clones in a tumor regression model. Our findings demonstrate that core fucosylation is a common modification indirectly induced by targeted therapies that paradoxically promotes resistance.
Project description:Limbal epithelial stem cell (LESC) deficiency represents a significant clinical problem especially in bilateral cases. Induced pluripotent stem cells (iPSC) may be a promising source of LESC, allowing standardized and continual propagation and banking. The objective of this study was to generate iPSC from human limbal epithelial cultures and differentiate them back into limbal epithelial cells using substrata mimicking the natural LESC niche. Using Yamanaka’s episomal vectors limbal-derived iPSC were reprogrammed from LESC cultured from donor corneoscleral rims and from human skin fibroblasts. A clone from limbal-derived iPSC expressed stemness markers, had a diploid karyotype, and produced teratomas in nude mice representing three germ layers. Compared to parental LESC, this clone had fewer specific gene methylation changes revealed using the Illumina Infinium Methylation 450k Beadchips than compared to skin fibroblasts. The expression of putative LESC markers was examined by quantitative RT-PCR and immunostaining in limbal-derived and fibroblast-derived iPSC cultured on denuded human amniotic membrane or denuded cornea. Limbal-derived iPSC had markedly stronger expression of PAX6, ABCG2, Np63, keratins 14, 15, 17, and N-cadherin than fibroblast-derived iPSC. On denuded corneas, limbal-derived iPSC showed the expression of differentiated corneal keratins 3 and 12. The data suggest that iPSC differentiation to a desired lineage may be facilitated by their generation from the same tissue. This may be related to preservation of parental tissue epigenetic methylation signatures in iPSC and use of biological substrata similar to the natural niche of parental cells. The data pave the way for generating transplantable LESC from limbal-derived iPSC.
Project description:The glycocalyx consists of glycoproteins, glycolipids and extracellular polysaccharides at the cell surface which mediate viscoelastic and electrostatic barrier function. In molecular interactions the glycocalyx is thought to segregate locally to facilitate receptor-ligand binding, yet high-resolution maps of glycocalyx domains in cell-cell and cell-matrix interactions are lacking. We here applied TMTH-sulfoximine (THS)-based biorthogonal chemistry in live-cell culture and demonstrate much-enhanced glycocalyx detection, compared to established dibenzocyclooctyne-based labeling. Using superresolution microscopy, we identified micron-scale moderately diminished glycocalyx in cell-cell contacts and subtotal depletion in protrusions at the leading and trailing edges and membrane blebs when cells invaded 3D fibrillar matrix. At contacts to collagen fibrils, focal integrin clusters segregated in outward-protrusive nanodomains from glycocalyx (distance: 350 nm), forming adhesion sites of low glycocalyx content. Thus, THS-based next-generation bioorthogonal labelling of live cells identifies micro- and nanodomains with altered glycocalyx density, implicating local glycocalyx downregulation in functional cell-cell and cell-matrix interactions.
Project description:Limbal and central regoins of the rat cornea epithelium were used to constract 2 SAGE libraries, in order to identify candidate genes to distinguish stem cell from differentiated central cornea epithelium cells. Keywords: gene expression SAGE-based, count cornea epithelium was scraped from central cornea and limbal Epithelium regions of 6 week male Wister rat 16 and 48 eye (respectively).