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Stem Cell Reports Dec 2023Recently, the murine cornea has reemerged as a robust stem cell (SC) model, allowing individual SC tracing in living animals. The cornea has pioneered seminal... (Review)
Review
Recently, the murine cornea has reemerged as a robust stem cell (SC) model, allowing individual SC tracing in living animals. The cornea has pioneered seminal discoveries in SC biology and regenerative medicine, from the first corneal transplantation in 1905 to the identification of limbal SCs and their transplantation to successfully restore vision in the early 1990s. Recent experiments have exposed unexpected properties attributed to SCs and progenitors and revealed flexibility in the differentiation program and a key role for the SC niche. Here, we discuss the limbal SC model and its broader relevance to other tissues, disease, and therapy.
Topics: Mice; Animals; Epithelium, Corneal; Limbus Corneae; Cornea; Stem Cells; Cell Differentiation; Stem Cell Transplantation
PubMed: 38039972
DOI: 10.1016/j.stemcr.2023.10.023 -
Cells Oct 2023Continuous replenishment of the corneal epithelium is pivotal for maintaining optical transparency and achieving optimal visual perception. This dynamic process is... (Review)
Review
Continuous replenishment of the corneal epithelium is pivotal for maintaining optical transparency and achieving optimal visual perception. This dynamic process is driven by limbal epithelial stem cells (LESCs) located at the junction between the cornea and conjunctiva, which is otherwise known as the limbus. In patients afflicted with diabetes, hyperglycemia-induced impairments in corneal epithelial regeneration results in persistent epithelial and other defects on the ocular surface, termed diabetic keratopathy (DK), which progressively diminish vision and quality of life. Reports of delayed corneal wound healing and the reduced expression of putative stem cell markers in diabetic relative to healthy eyes suggest that the pathogenesis of DK may be associated with the abnormal activity of LESCs. However, the precise role of these cells in diabetic corneal disease is poorly understood and yet to be comprehensively explored. Herein, we review existing literature highlighting aberrant LESC activity in diabetes, focusing on factors that influence their form and function, and emerging therapies to correct these defects. The consequences of malfunctioning or depleted LESC stocks in DK and limbal stem cell deficiency (LSCD) are also discussed. These insights could be exploited to identify novel targets for improving the management of ocular surface complications that manifest in patients with diabetes.
Topics: Humans; Quality of Life; Limbus Corneae; Cornea; Corneal Diseases; Stem Cells; Diabetes Mellitus
PubMed: 37887302
DOI: 10.3390/cells12202458 -
Cell Death and Differentiation Jun 2023The cell fate decisions of stem cells (SCs) largely depend on signals from their microenvironment (niche). However, very little is known about how biochemical niche cues...
The cell fate decisions of stem cells (SCs) largely depend on signals from their microenvironment (niche). However, very little is known about how biochemical niche cues control cell behavior in vivo. To address this question, we focused on the corneal epithelial SC model in which the SC niche, known as the limbus, is spatially segregated from the differentiation compartment. We report that the unique biomechanical property of the limbus supports the nuclear localization and function of Yes-associated protein (YAP), a putative mediator of the mechanotransduction pathway. Perturbation of tissue stiffness or YAP activity affects SC function as well as tissue integrity under homeostasis and significantly inhibited the regeneration of the SC population following SC depletion. In vitro experiments revealed that substrates with the rigidity of the corneal differentiation compartment inhibit nuclear YAP localization and induce differentiation, a mechanism that is mediated by the TGFβ-SMAD2/3 pathway. Taken together, these results indicate that SC sense biomechanical niche signals and that manipulation of mechano-sensory machinery or its downstream biochemical output may bear fruits in SC expansion for regenerative therapy.
Topics: Cell Differentiation; Epithelium, Corneal; Limbus Corneae; Mechanotransduction, Cellular; Stem Cell Niche; Stem Cells; Humans; YAP-Signaling Proteins
PubMed: 37095157
DOI: 10.1038/s41418-023-01156-7 -
The British Journal of Ophthalmology Nov 2023The purpose of this double-masked, parallel randomised controlled trial was to compare the recurrence rate and other outcomes between conjunctival-limbal autograft... (Randomized Controlled Trial)
Randomized Controlled Trial
PURPOSE
The purpose of this double-masked, parallel randomised controlled trial was to compare the recurrence rate and other outcomes between conjunctival-limbal autograft (CLAu) and mini-simple limbal epithelial transplantation (mini-SLET) after excision of pterygium.
METHODS
Eligibility criteria for participants was the presence of a primary nasal pterygium extending equally to or greater than two millimetres on the cornea on its horizontal axis from the nasal limbus. The participants were allocated into two groups (CLAu and mini-SLET) using simple randomisation with a table of random numbers. Participants and the outcome assessor were masked to the intervention. The study protocol is listed and available on https://clinicaltrials.gov (Identifier: NCT03363282).
RESULTS
A total of 61 eyes were enrolled in the study, 33 underwent CLAu (group 1) and 28 mini-SLET (group 2), all eyes were analysed in each group. At 2, 3, 6 and 12 months the CLAu group exhibited a recurrence of 0%, 6.1%, 8.1% and 8.1%, while the mini-SLET exhibited a recurrence of 0%, 17.9%, 50% and 53.5% (p<0.05). There were no intraoperative or postoperative complications in either of the two groups.
CONCLUSION
The findings of this study suggest that mini-SLET has a higher recurrence rate and provides no advantage over CLAu in the treatment of primary pterygium.
Topics: Humans; Pterygium; Autografts; Conjunctiva; Transplantation, Autologous; Limbus Corneae; Recurrence; Treatment Outcome; Follow-Up Studies
PubMed: 37739769
DOI: 10.1136/bjo-2021-320707 -
Cells Oct 2023Epithelial and stromal/mesenchymal limbal stem cells contribute to corneal homeostasis and cell renewal. Extracellular vesicles (EVs), including exosomes (Exos), can be...
Epithelial and stromal/mesenchymal limbal stem cells contribute to corneal homeostasis and cell renewal. Extracellular vesicles (EVs), including exosomes (Exos), can be paracrine mediators of intercellular communication. Previously, we described cargos and regulatory roles of limbal stromal cell (LSC)-derived Exos in non-diabetic (N) and diabetic (DM) limbal epithelial cells (LECs). Presently, we quantify the miRNA and proteome profiles of human LEC-derived Exos and their regulatory roles in N- and DM-LSC. We revealed some miRNA and protein differences in DM vs. N-LEC-derived Exos' cargos, including proteins involved in Exo biogenesis and packaging that may affect Exo production and ultimately cellular crosstalk and corneal function. Treatment by N-Exos, but not by DM-Exos, enhanced wound healing in cultured N-LSCs and increased proliferation rates in N and DM LSCs vs. corresponding untreated (control) cells. N-Exos-treated LSCs reduced the keratocyte markers ALDH3A1 and lumican and increased the MSC markers CD73, CD90, and CD105 vs. control LSCs. These being opposite to the changes quantified in wounded LSCs. Overall, N-LEC Exos have a more pronounced effect on LSC wound healing, proliferation, and stem cell marker expression than DM-LEC Exos. This suggests that regulatory miRNA and protein cargo differences in DM- vs. N-LEC-derived Exos could contribute to the disease state.
Topics: Humans; MicroRNAs; Exosomes; Limbus Corneae; Cornea; Diabetes Mellitus; Epithelial Cells; Stromal Cells; Cell Communication
PubMed: 37947602
DOI: 10.3390/cells12212524 -
PLoS Biology Oct 2023The transparent corneal epithelium in the eye is maintained through the homeostasis regulated by limbal stem cells (LSCs), while the nontransparent epidermis relies on...
The transparent corneal epithelium in the eye is maintained through the homeostasis regulated by limbal stem cells (LSCs), while the nontransparent epidermis relies on epidermal keratinocytes for renewal. Despite their cellular similarities, the precise cell fates of these two types of epithelial stem cells, which give rise to functionally distinct epithelia, remain unknown. We performed a multi-omics analysis of human LSCs from the cornea and keratinocytes from the epidermis and characterized their molecular signatures, highlighting their similarities and differences. Through gene regulatory network analyses, we identified shared and cell type-specific transcription factors (TFs) that define specific cell fates and established their regulatory hierarchy. Single-cell RNA-seq (scRNA-seq) analyses of the cornea and the epidermis confirmed these shared and cell type-specific TFs. Notably, the shared and LSC-specific TFs can cooperatively target genes associated with corneal opacity. Importantly, we discovered that FOSL2, a direct PAX6 target gene, is a novel candidate associated with corneal opacity, and it regulates genes implicated in corneal diseases. By characterizing molecular signatures, our study unveils the regulatory circuitry governing the LSC fate and its association with corneal opacity.
Topics: Humans; Limbus Corneae; Cornea; Epithelium, Corneal; Transcription Factors; Cell Differentiation; Corneal Opacity
PubMed: 37856539
DOI: 10.1371/journal.pbio.3002336 -
Aging Sep 2023This study aimed to investigate the senescent phenotypes of human corneal and conjunctival epithelial cells.
PURPOSE
This study aimed to investigate the senescent phenotypes of human corneal and conjunctival epithelial cells.
METHODS
We examined cell morphology, senescence-associated β-galactosidase (SA-β-gal) activity, cell proliferation, and expression of senescence markers (p16 and p21). RNA sequencing analysis was conducted to compare gene expression profiles between senescent and non-senescent cells. Finally, the potential involvement of senescent cells in the pathogenesis of ocular surface diseases was investigated.
RESULTS
X-irradiated corneal and conjunctival epithelial cells exhibited typical senescence phenotypes, i.e., flattened morphologies, increased SA-β-gal activity, decreased cell proliferation, and increased expression of senescence markers, p16 and p21. RNA-seq analysis revealed substantial differences in gene expression profiles between senescent corneal (SCo) and conjunctival epithelial cells (SCj). Moreover, SCj were detected in pathological conjunctival tissues associated with limbal stem cell deficiency (LSCD) due to Stevens-Johnson syndrome or chemical burns, potentially being involved in abnormal differentiation.
CONCLUSION
This study highlights the cellular and molecular characteristics of senescent ocular surface cells, particularly in SCj that show abnormal keratin expression, and their potential roles in severe ocular surface diseases and pathology.
Topics: Humans; Transcriptome; Limbus Corneae; Cornea; Epithelial Cells; Conjunctiva
PubMed: 37770232
DOI: 10.18632/aging.205113 -
Life Science Alliance Sep 2023Impaired development and maintenance of Schlemm's canal (SC) are associated with perturbed aqueous humor outflow and intraocular pressure. The angiopoietin (ANGPT)/TIE2...
Impaired development and maintenance of Schlemm's canal (SC) are associated with perturbed aqueous humor outflow and intraocular pressure. The angiopoietin (ANGPT)/TIE2 signaling pathway regulates SC development and maintenance, whereas the molecular mechanisms of crosstalk between SC and the neural crest (NC)-derived neighboring tissue, the trabecular meshwork (TM), are poorly understood. Here, we show NC-specific forkhead box ( deletion in mice results in impaired SC morphogenesis, loss of SC identity, and elevated intraocular pressure. Visible-light optical coherence tomography analysis further demonstrated functional impairment of the SC in response to changes in intraocular pressure in NC- mice, suggesting altered TM biomechanics. Single-cell RNA-sequencing analysis identified that this phenotype is predominately characterized by transcriptional changes associated with extracellular matrix organization and stiffness in TM cell clusters, including increased matrix metalloproteinase expression, which can cleave the TIE2 ectodomain to produce soluble TIE2. Moreover, endothelial-specific deletion impaired SC morphogenesis because of reduced TIE2 expression, which was rescued by deleting the TIE2 phosphatase VE-PTP. Thus, Foxc2 is critical in maintaining SC identity and morphogenesis via TM-SC crosstalk.
Topics: Animals; Mice; Aqueous Humor; Glaucoma; Intraocular Pressure; Schlemm's Canal; Trabecular Meshwork
PubMed: 37414529
DOI: 10.26508/lsa.202201721 -
Scientific Reports Jun 2023In the normal eye, most of the aqueous humor drains through the trabecular meshwork (TM) and Schlemm's canal (SC). The concentration of transforming growth factor beta 2...
In the normal eye, most of the aqueous humor drains through the trabecular meshwork (TM) and Schlemm's canal (SC). The concentration of transforming growth factor beta 2 (TGF-β2) is increased in the aqueous humor of primary open angle glaucoma patients. TGF-β2 increases outflow resistance by affecting the TM and SC, and endothelial-mesenchymal transition (EndMT) of SC cells is involved in these changes. Here, we investigated the effect of a ROCK inhibitor on TGF-β2-induced EndMT in SC cells. The ROCK inhibitor Y-27632 suppressed the TGF-β2-induced increase in the trans-endothelial electrical resistance (TER) and proliferation of SC cells. Y-27632 suppressed the expression of α-SMA, N-cadherin, and Snail, which are upregulated by TGF-β2. Moreover, TGF-β2 decreased mRNA levels of bone morphogenetic protein (BMP) 4 and increased those of the BMP antagonist gremlin (GREM1), but Y-27632 significantly suppressed these changes. Y-27632 also inhibited TGF-β2-induced phosphorylation of p-38 mitogen-activated protein kinase (MAPK). BMP4 and the p-38 MAPK inhibitor SB203580 suppressed the TGF-β2-induced TER elevation in SC cells. Moreover, SB203580 suppressed TGF-β2-induced upregulation of fibronectin, Snail, and GREM1. These results indicate that a ROCK inhibitor inhibited the TGF-β2-induced EndMT in SC cells, implying the involvement of p38 MAPK and BMP4 signaling.
Topics: Humans; Endothelial Cells; rho-Associated Kinases; Transforming Growth Factor beta2; Glaucoma, Open-Angle; Schlemm's Canal; Transforming Growth Factors
PubMed: 37316554
DOI: 10.1038/s41598-023-36808-8 -
Cells Jul 2023The structure and major cell types of the multi-layer human cornea have been extensively studied. However, various cell states in specific cell types and key genes that... (Review)
Review
The structure and major cell types of the multi-layer human cornea have been extensively studied. However, various cell states in specific cell types and key genes that define the cell states are not fully understood, hindering our comprehension of corneal homeostasis, related diseases, and therapeutic discovery. Single-cell RNA sequencing is a revolutionary and powerful tool for identifying cell states within tissues such as the cornea. This review provides an overview of current single-cell RNA sequencing studies on the human cornea, highlighting similarities and differences between them, and summarizing the key genes that define corneal cell states reported in these studies. In addition, this review discusses the opportunities and challenges of using single-cell RNA sequencing to study corneal biology in health and disease.
Topics: Humans; Epithelium, Corneal; Limbus Corneae; Stem Cells; Cornea; Sequence Analysis, RNA; Biology
PubMed: 37443842
DOI: 10.3390/cells12131808