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Di Girolamo N. Biologicals and Biomaterials for Corneal Regeneration and Vision Restoration in Limbal Stem Cell Deficiency. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2401763. [PMID: 38777343 DOI: 10.1002/adma.202401763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/15/2024] [Indexed: 05/25/2024]
Abstract
The mammalian cornea is decorated with stem cells bestowed with the life-long task of renewing the epithelium, provided they remain healthy, functional, and in sufficient numbers. If not, a debilitating disease known as limbal stem cell deficiency (LSCD) can develop causing blindness. Decades after the first stem cell (SC) therapy is devised to treat this condition, patients continue to suffer unacceptable failures. During this time, improvements to therapeutics have included identifying better markers to isolate robust SC populations and nurturing them on crudely modified biological or biomaterial scaffolds including human amniotic membrane, fibrin, and contact lenses, prior to their delivery. Researchers are now gathering information about the biomolecular and biomechanical properties of the corneal SC niche to decipher what biological and/or synthetic materials can be incorporated into these carriers. Advances in biomedical engineering including electrospinning and 3D bioprinting with surface functionalization and micropatterning, and self-assembly models, have generated a wealth of biocompatible, biodegradable, integrating scaffolds to choose from, some of which are being tested for their SC delivery capacity in the hope of improving clinical outcomes for patients with LSCD.
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Affiliation(s)
- Nick Di Girolamo
- Mechanisms of Disease and Translational Research, School of Biomedical Sciences, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, 2052, Australia
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2
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Altshuler A, Amitai-Lange A, Nasser W, Dimri S, Bhattacharya S, Tiosano B, Barbara R, Aberdam D, Shimmura S, Shalom-Feuerstein R. Eyes open on stem cells. Stem Cell Reports 2023; 18:2313-2327. [PMID: 38039972 PMCID: PMC10724227 DOI: 10.1016/j.stemcr.2023.10.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 12/03/2023] Open
Abstract
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.
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Affiliation(s)
- Anna Altshuler
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel.
| | - Aya Amitai-Lange
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel
| | - Waseem Nasser
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel
| | - Shalini Dimri
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel
| | - Swarnabh Bhattacharya
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel
| | - Beatrice Tiosano
- Department of Ophthalmology, Hillel Yaffe Medical Center, Hadera, Israel
| | - Ramez Barbara
- Department of Ophthalmology, Hillel Yaffe Medical Center, Hadera, Israel
| | - Daniel Aberdam
- Université Paris-Cité, INSERM U1138, Centre des Cordeliers, 75270 Paris, France
| | - Shigeto Shimmura
- Department of Clinical Regenerative Medicine, Fujita Medical Innovation Center, Tokyo, Japan
| | - Ruby Shalom-Feuerstein
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, Haifa 31096, Israel.
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3
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Bonnet C, González S, Deng SX, Zheng JJ. Wnt activation as a potential therapeutic approach to treat partial limbal stem cell deficiency. Sci Rep 2023; 13:15670. [PMID: 37735479 PMCID: PMC10514048 DOI: 10.1038/s41598-023-42794-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 09/14/2023] [Indexed: 09/23/2023] Open
Abstract
Limbal epithelial stem/progenitor cells (LSCs) are adult stem cells located at the limbus, tightly regulated by their niche involving numerous signaling pathways, such as Wnt. Wnt proteins are secreted morphogens that play critical roles in embryonic development, stem cell proliferation, self-renewal, tissue regeneration, and remodeling in adults. It has been shown that a small molecule Wnt mimic could improve LSCs expansion ex vivo. Damage to the LSCs and/or their niche can lead to limbal stem cell deficiency (LSCD), a condition that can cause corneal blindness and is difficult to treat. This study explored if repopulating residual LSCs in partial LSCD through Wnt activation could be a novel therapeutic approach. To mimic LSCD due to a chemical injury, single cultured LSCs were exposed to various concentrations of sodium hydroxide. A progressive loss of the LSCs phenotype was observed: the percentage of p63bright cells and cytokeratin (K)14+ cells decreased while the percentage of K12+ increased. Wnt activation was attained by treating the LSCs with lithium chloride (LiCl) and a small-molecule Wnt mimic, respectively. After 18 h of treatment, LSCs proliferation was increased, and the LSCs phenotype was recovered, while the untreated cells did not proliferate and lost their phenotype. The percentage of p63bright cells was significantly higher in the Wnt mimic-treated cells compared with untreated cells, while the percentage of K12+ cells was significantly lower. These findings suggest that local Wnt activation may rescue LSCs upon alkaline injury.
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Affiliation(s)
- Clémence Bonnet
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA, 90095, USA
- INSERM, UMRS1138, Team 17, From Physiopathology of Ocular Diseases to Clinical Development, Cordeliers Research Center, Ophthalmology Department, Cochin Hospital, AP-HP, Université Paris Cité, 75005, Paris, France
| | - Sheyla González
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA, 90095, USA
| | - Sophie X Deng
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA, 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Jie J Zheng
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA, 90095, USA.
- Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA.
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4
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Bhattacharya S, Mukherjee A, Pisano S, Dimri S, Knaane E, Altshuler A, Nasser W, Dey S, Shi L, Mizrahi I, Blum N, Jokel O, Amitai-Lange A, Kaganovsky A, Mimouni M, Socea S, Midlij M, Tiosano B, Hasson P, Feral C, Wolfenson H, Shalom-Feuerstein R. The biophysical property of the limbal niche maintains stemness through YAP. Cell Death Differ 2023:10.1038/s41418-023-01156-7. [PMID: 37095157 DOI: 10.1038/s41418-023-01156-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 03/23/2023] [Accepted: 03/28/2023] [Indexed: 04/26/2023] Open
Abstract
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.
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Affiliation(s)
- Swarnabh Bhattacharya
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel.
- Department of Medical Oncology and Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.
- Departments of Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, 02115, USA.
| | - Abhishek Mukherjee
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Sabrina Pisano
- Université Côte d'Azur, INSERM, CNRS, IRCAN, 06107, Nice, France
| | - Shalini Dimri
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Eman Knaane
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Anna Altshuler
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Waseem Nasser
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Sunanda Dey
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Lidan Shi
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Ido Mizrahi
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Noam Blum
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Ophir Jokel
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Aya Amitai-Lange
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Anna Kaganovsky
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Michael Mimouni
- Department of Ophthalmology, Rambam Health Care Campus, 31096, Haifa, Israel
| | - Sergiu Socea
- Department of Ophthalmology, Rambam Health Care Campus, 31096, Haifa, Israel
| | - Mohamad Midlij
- Department of Ophthalmology, Hilel Yafe Medical Center, Hadera, Israel
| | - Beatrice Tiosano
- Department of Ophthalmology, Hilel Yafe Medical Center, Hadera, Israel
| | - Peleg Hasson
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel
| | - Chloe Feral
- Université Côte d'Azur, INSERM, CNRS, IRCAN, 06107, Nice, France
| | - Haguy Wolfenson
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel.
| | - Ruby Shalom-Feuerstein
- Department of Genetics & Developmental Biology, The Rappaport Faculty of Medicine & Research Institute, Technion Integrated Cancer Center, Technion - Israel Institute of Technology, 31096, Haifa, Israel.
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5
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Lin JB, Shen X, Pfeifer CW, Shiau F, Santeford A, Ruzycki PA, Clark BS, Liu Q, Huang AJW, Apte RS. Dry eye disease in mice activates adaptive corneal epithelial regeneration distinct from constitutive renewal in homeostasis. Proc Natl Acad Sci U S A 2023; 120:e2204134120. [PMID: 36595669 PMCID: PMC9926235 DOI: 10.1073/pnas.2204134120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 11/28/2022] [Indexed: 01/05/2023] Open
Abstract
Many epithelial compartments undergo constitutive renewal in homeostasis but activate unique regenerative responses following injury. The clear corneal epithelium is crucial for vision and is renewed from limbal stem cells (LSCs). Using single-cell RNA sequencing, we profiled the mouse corneal epithelium in homeostasis, aging, diabetes, and dry eye disease (DED), where tear deficiency predisposes the cornea to recurrent injury. In homeostasis, we capture the transcriptional states that accomplish continuous tissue turnover. We leverage our dataset to identify candidate genes and gene networks that characterize key stages across homeostatic renewal, including markers for LSCs. In aging and diabetes, there were only mild changes with <15 dysregulated genes. The constitutive cell types that accomplish homeostatic renewal were conserved in DED but were associated with activation of cell states that comprise "adaptive regeneration." We provide global markers that distinguish cell types in homeostatic renewal vs. adaptive regeneration and markers that specifically define DED-elicited proliferating and differentiating cell types. We validate that expression of SPARC, a marker of adaptive regeneration, is also induced in corneal epithelial wound healing and accelerates wound closure in a corneal epithelial cell scratch assay. Finally, we propose a classification system for LSC markers based on their expression fidelity in homeostasis and disease. This transcriptional dissection uncovers the dramatically altered transcriptional landscape of the corneal epithelium in DED, providing a framework and atlas for future study of these ocular surface stem cells in health and disease.
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Affiliation(s)
- Joseph B. Lin
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
- Division of Biology and Biomedical Sciences Neurosciences Graduate Program, Washington University School of Medicine, St. Louis, MO63110
| | - Xiaolei Shen
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, St. Louis, MO63110
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO63110
| | - Charles W. Pfeifer
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
- Division of Biology and Biomedical Sciences Neurosciences Graduate Program, Washington University School of Medicine, St. Louis, MO63110
| | - Fion Shiau
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
| | - Andrea Santeford
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
| | - Philip A. Ruzycki
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
| | - Brian S. Clark
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO63110
- Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO63110
| | - Qin Liu
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, St. Louis, MO63110
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO63110
| | - Andrew J. W. Huang
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
| | - Rajendra S. Apte
- John F. Hardesty, MD Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO63110
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO63110
- Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO63110
- Department of Medicine, Washington University School of Medicine, St. Louis, MO63110
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Lee V, Rompolas P. Corneal regeneration: insights in epithelial stem cell heterogeneity and dynamics. Curr Opin Genet Dev 2022; 77:101981. [PMID: 36084496 PMCID: PMC9938714 DOI: 10.1016/j.gde.2022.101981] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 01/27/2023]
Abstract
The discovery of slow-cycling cells at the corneal periphery three decades ago established the limbus as the putative corneal stem cell niche. Since then, studies have underscored the importance of the limbal stem cells in maintaining the health and function of the ocular surface. Advancements in our understanding of stem cell biology have been successfully translated into stem cell therapies for corneal diseases. Here, we review recent developments in mouse genetics, intravital imaging, and single-cell genomics that have revealed an underappreciated complexity of the limbal stem cells, from their molecular identity, function, and interactions with their niche environment. Continued efforts to elucidate stem cell dynamics of this extraordinary tissue are critical for not only understanding stem cell biology but also for advancing therapeutic innovation and development.
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Affiliation(s)
- Vivian Lee
- Department of Ophthalmology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Dermatology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Panteleimon Rompolas
- Department of Ophthalmology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Dermatology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
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Ikkala K, Raatikainen S, Koivula H, Michon F. Zebrafish cornea formation and homeostasis reveal a slow maturation process, similarly to terrestrial vertebrates' corneas. Front Physiol 2022; 13:906155. [PMID: 36388116 PMCID: PMC9663661 DOI: 10.3389/fphys.2022.906155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 10/14/2022] [Indexed: 01/30/2024] Open
Abstract
Corneal blindness is the fourth leading cause of blindness worldwide. The superficial position of cornea on the eye makes this tissue prone to environmental aggressions, which can have a strong impact on sight. While most corneal pathology studies utilize terrestrial models, the knowledge on zebrafish cornea is too scarce to comprehend its strategy for the maintenance of a clear sight in aquatic environment. In this study, we deciphered the cellular and molecular events during corneal formation and maturation in zebrafish. After describing the morphological changes taking place from 3 days post fertilization (dpf) to adulthood, we analyzed cell proliferation. We showed that label retaining cells appear around 14 to 21dpf. Our cell proliferation study, combined to the study of Pax6a and krtt1c19e expression, demonstrate a long maturation process, ending after 45dpf. This maturation ends with a solid patterning of corneal innervation. Finally, we demonstrated that corneal wounding leads to an intense dedifferentiation, leading to the recapitulation of corneal formation and maturation, via a plasticity period. Altogether, our study deciphers the maturation steps of an aquatic cornea. These findings demonstrate the conservation of corneal formation, maturation and wound healing process in aquatic and terrestrial organisms, and they will enhance the use of zebrafish as model for corneal physiology studies.
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Affiliation(s)
- Kaisa Ikkala
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Sini Raatikainen
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Henri Koivula
- Zebrafish Unit, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Frederic Michon
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
- Institute for Neurosciences of Montpellier, University Montpellier, INSERM, Montpellier, France
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8
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Di Girolamo N, Park M. Cell identity changes in ocular surface Epithelia. Prog Retin Eye Res 2022:101148. [DOI: 10.1016/j.preteyeres.2022.101148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/13/2022] [Accepted: 11/09/2022] [Indexed: 11/21/2022]
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Park M, Zhang R, Pandzic E, Sun M, Coulson-Thomas VJ, Di Girolamo N. Plasticity of ocular surface epithelia: Using a murine model of limbal stem cell deficiency to delineate metaplasia and transdifferentiation. Stem Cell Reports 2022; 17:2451-2466. [DOI: 10.1016/j.stemcr.2022.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 09/25/2022] [Accepted: 09/26/2022] [Indexed: 11/06/2022] Open
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Puri S, Moreno IY, Sun M, Verma S, Lin X, Gesteira TF, Coulson-Thomas VJ. Hyaluronan supports the limbal stem cell phenotype during ex vivo culture. Stem Cell Res Ther 2022; 13:384. [PMID: 35907870 PMCID: PMC9338506 DOI: 10.1186/s13287-022-03084-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/21/2022] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Hyaluronan (HA) has previously been identified as an integral component of the limbal stem cell niche in vivo. In this study, we investigated whether a similar HA matrix is also expressed in vitro providing a niche supporting limbal epithelial stem cells (LESCs) during ex vivo expansion. We also investigated whether providing exogenous HA in vitro is beneficial to LESCs during ex vivo expansion. METHOD Human LESCs (hLESCs) were isolated from donor corneas and a mouse corneal epithelial progenitor cell line (TKE2) was obtained. The HA matrix was identified surrounding LESCs in vitro using immunocytochemistry, flow cytometry and red blood exclusion assay. Thereafter, LESCs were maintained on HA coated dishes or in the presence of HA supplemented in the media, and viability, proliferation, cell size, colony formation capabilities and expression of putative stem cell markers were compared with cells maintained on commonly used coated dishes. RESULTS hLESCs and TKE2 cells express an HA-rich matrix in vitro, and this matrix is essential for maintaining LESCs. Further supplying exogenous HA, as a substrate and supplemented to the media, increases LESC proliferation, colony formation capabilities and the expression levels of putative limbal stem cell markers. CONCLUSION Our data show that both exogenous and endogenous HA help to maintain the LESC phenotype. Exogenous HA provides improved culture conditions for LESC during ex vivo expansion. Thus, HA forms a favorable microenvironment for LESCs during ex vivo expansion and, therefore, could be considered as an easy and cost-effective substrate and/or supplement for culturing LESCs in the clinic.
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Affiliation(s)
- Sudan Puri
- College of Optometry, University of Houston, Houston, TX, USA
| | - Isabel Y Moreno
- College of Optometry, University of Houston, Houston, TX, USA
| | - Mingxia Sun
- College of Optometry, University of Houston, Houston, TX, USA
| | - Sudhir Verma
- College of Optometry, University of Houston, Houston, TX, USA
- Department of Zoology, Deen Dayal Upadhyaya College, University of Delhi, New Delhi, India
| | - Xiao Lin
- College of Optometry, University of Houston, Houston, TX, USA
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Richardson A, Fok S, Lee V, Rye KA, Di Girolamo N, Cochran BJ. Use of High-Refractive Index Hydrogels and Tissue Clearing for Large Biological Sample Imaging. Gels 2022; 8:gels8010032. [PMID: 35049567 PMCID: PMC8774797 DOI: 10.3390/gels8010032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/23/2021] [Accepted: 01/01/2022] [Indexed: 01/03/2023] Open
Abstract
Recent advances in tissue clearing and light sheet fluorescence microscopy have improved insights into and understanding of tissue morphology and disease pathology by imaging large samples without the requirement of histological sectioning. However, sample handling and conservation of sample integrity during lengthy staining and acquisition protocols remains a challenge. This study overcomes these challenges with acrylamide hydrogels synthesised to match the refractive index of solutions typically utilised in aqueous tissue clearing protocols. These hydrogels have a high-water content (82.0 ± 3.7% by weight). The gels are stable over time and FITC-IgG readily permeated into and effluxed out of them. Whilst the gels deformed and/or swelled over time in some commonly used solutions, this was overcome by using a previously described custom refractive index matched solution. To validate their use, CUBIC cleared mouse tissues and whole embryos were embedded in hydrogels, stained using fluorescent small molecule dyes, labels and antibodies and successfully imaged using light sheet fluorescence microscopy. In conclusion, the high water content, high refractive index hydrogels described in this study have broad applicability to research that delves into pathophysiological processes by stabilising and protecting large and fragile samples.
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Affiliation(s)
- Alexander Richardson
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (A.R.); (V.L.); (K.-A.R.); (N.D.G.)
| | - Sandra Fok
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Centre, UNSW Sydney, Sydney, NSW 2052, Australia;
| | - Victoria Lee
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (A.R.); (V.L.); (K.-A.R.); (N.D.G.)
| | - Kerry-Anne Rye
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (A.R.); (V.L.); (K.-A.R.); (N.D.G.)
| | - Nick Di Girolamo
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (A.R.); (V.L.); (K.-A.R.); (N.D.G.)
| | - Blake J. Cochran
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; (A.R.); (V.L.); (K.-A.R.); (N.D.G.)
- Correspondence:
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METTL3-Mediated m 6A RNA Modification Regulates Corneal Injury Repair. Stem Cells Int 2021; 2021:5512153. [PMID: 34721590 PMCID: PMC8556082 DOI: 10.1155/2021/5512153] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 09/06/2021] [Indexed: 12/13/2022] Open
Abstract
Limbal stem cells are essential for continuous corneal regeneration and injury repair. METTL3-catalyzed N6-methyladenosine (m6A) mRNA modifications are involved in many biological processes and play a specific role in stem cell regeneration, while the role of m6A modifications in corneal injury repair remains unknown. In this study, we generated a limbal stem cell-specific METTL3 knockout mouse model and studied the role of m6A in repairing corneal injury caused by alkali burn. The results showed that METTL3 knockout in the limbal stem cells promotes the in vivo cell proliferation and migration, leading to the fast repair of corneal injury. In addition, m6A modification profiling identified stem cell regulatory factors AHNAK and DDIT4 as m6A targets. Our study reveals the essential functions of m6A RNA modification in regulating injury repair and provides novel insights for clinical therapy of corneal diseases.
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13
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Bonnet C, González S, Roberts JS, Robertson SYT, Ruiz M, Zheng J, Deng SX. Human limbal epithelial stem cell regulation, bioengineering and function. Prog Retin Eye Res 2021; 85:100956. [PMID: 33676006 PMCID: PMC8428188 DOI: 10.1016/j.preteyeres.2021.100956] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 02/21/2021] [Accepted: 02/26/2021] [Indexed: 12/13/2022]
Abstract
The corneal epithelium is continuously renewed by limbal stem/progenitor cells (LSCs), a cell population harbored in a highly regulated niche located at the limbus. Dysfunction and/or loss of LSCs and their niche cause limbal stem cell deficiency (LSCD), a disease that is marked by invasion of conjunctival epithelium into the cornea and results in failure of epithelial wound healing. Corneal opacity, pain, loss of vision, and blindness are the consequences of LSCD. Successful treatment of LSCD depends on accurate diagnosis and staging of the disease and requires restoration of functional LSCs and their niche. This review highlights the major advances in the identification of potential LSC biomarkers and components of the LSC niche, understanding of LSC regulation, methods and regulatory standards in bioengineering of LSCs, and diagnosis and staging of LSCD. Overall, this review presents key points for researchers and clinicians alike to consider in deepening the understanding of LSC biology and improving LSCD therapies.
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Affiliation(s)
- Clémence Bonnet
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA; Cornea Department, Paris University, Cochin Hospital, AP-HP, F-75014, Paris, France
| | - Sheyla González
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA
| | - JoAnn S Roberts
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA
| | - Sarah Y T Robertson
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA
| | - Maxime Ruiz
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA
| | - Jie Zheng
- Basic Science Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA
| | - Sophie X Deng
- Cornea Division, Stein Eye Institute, University of California, Los Angeles, CA, 90095, USA.
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14
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Evaluating the clinical translational relevance of animal models for limbal stem cell deficiency: A systematic review. Ocul Surf 2021; 23:169-183. [PMID: 34583088 DOI: 10.1016/j.jtos.2021.09.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 09/20/2021] [Accepted: 09/23/2021] [Indexed: 12/13/2022]
Abstract
PURPOSE Animal models are pivotal for elucidating pathophysiological mechanisms and evaluating novel therapies. This systematic review identified studies that developed or adapted animal models of limbal stem cell deficiency (LSCD), assessed their reporting quality, summarized their key characteristics, and established their clinical translational relevance to human disease. METHODS The protocol was prospectively registered (PROSPERO CRD42020203937). Searches were conducted in PubMed, Ovid EMBASE and Web of Science in August 2020. Two authors screened citations, extracted data, assessed the reporting quality of eligible studies using the ARRIVE guidelines, and judged the clinical translational relevance of each model using a custom matrix. RESULTS 105 studies were included. Rabbits were the most common animal species. Overall, 97% of studies recapitulated LSCD to a clinical etiology, however 62% did not provide sufficient methodological detail to enable independent reproduction of the model. Adverse events and/or exclusion of animals were infrequently (20%) reported. Approximately one-quarter of studies did not produce the intended severity of LSCD; 34% provided insufficient information to assess the fidelity of disease induction. Adjunctive diagnostic confirmation of LSCD induction was performed in 13% of studies. CONCLUSIONS This is the first systematic review to assess the reporting quality and clinical translational relevance of animal models of LSCD. Models of LSCD have evolved over time, resulting in variable reporting of the characteristics of animals, experimental procedures and adverse events. In most studies, validation of LSCD was made using clinical tests; newer adjunctive techniques would enhance diagnostic validation. As most studies sought to evaluate novel therapies for LSCD, animal models should ideally recapitulate all features of the condition that develop in patients.
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15
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Latta L, Figueiredo FC, Ashery-Padan R, Collinson JM, Daniels J, Ferrari S, Szentmáry N, Solá S, Shalom-Feuerstein R, Lako M, Xapelli S, Aberdam D, Lagali N. Pathophysiology of aniridia-associated keratopathy: Developmental aspects and unanswered questions. Ocul Surf 2021; 22:245-266. [PMID: 34520870 DOI: 10.1016/j.jtos.2021.09.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 07/19/2021] [Accepted: 09/08/2021] [Indexed: 12/13/2022]
Abstract
Aniridia, a rare congenital disease, is often characterized by a progressive, pronounced limbal insufficiency and ocular surface pathology termed aniridia-associated keratopathy (AAK). Due to the characteristics of AAK and its bilateral nature, clinical management is challenging and complicated by the multiple coexisting ocular and systemic morbidities in aniridia. Although it is primarily assumed that AAK originates from a congenital limbal stem cell deficiency, in recent years AAK and its pathogenesis has been questioned in the light of new evidence and a refined understanding of ocular development and the biology of limbal stem cells (LSCs) and their niche. Here, by consolidating and comparing the latest clinical and preclinical evidence, we discuss key unanswered questions regarding ocular developmental aspects crucial to AAK. We also highlight hypotheses on the potential role of LSCs and the ocular surface microenvironment in AAK. The insights thus gained lead to a greater appreciation for the role of developmental and cellular processes in the emergence of AAK. They also highlight areas for future research to enable a deeper understanding of aniridia, and thereby the potential to develop new treatments for this rare but blinding ocular surface disease.
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Affiliation(s)
- L Latta
- Dr. Rolf. M. Schwiete Center for Limbal Stem Cell and Aniridia Research, Saarland University, Homburg, Saar, Germany; Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany.
| | - F C Figueiredo
- Department of Ophthalmology, Royal Victoria Infirmary, Newcastle Upon Tyne, United Kingdom
| | - R Ashery-Padan
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - J M Collinson
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
| | - J Daniels
- Cells for Sight, UCL Institute of Ophthalmology, University College London, London, EC1V 9EL, UK
| | - S Ferrari
- The Veneto Eye Bank Foundation, Venice, Italy
| | - N Szentmáry
- Dr. Rolf. M. Schwiete Center for Limbal Stem Cell and Aniridia Research, Saarland University, Homburg, Saar, Germany
| | - S Solá
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - R Shalom-Feuerstein
- Department of Genetics and Developmental Biology, The Rappaport Faculty of Medicine and Research Institute, Technion - Israel Institute of Technology, Haifa, Israel
| | - M Lako
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - S Xapelli
- Instituto Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - D Aberdam
- Centre de Recherche des Cordeliers, INSERM U1138, Team 17, France; Université de Paris, 75006, Paris, France.
| | - N Lagali
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden; Department of Ophthalmology, Sørlandet Hospital Arendal, Arendal, Norway.
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16
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Ligocki AJ, Fury W, Gutierrez C, Adler C, Yang T, Ni M, Bai Y, Wei Y, Lehmann GL, Romano C. Molecular characteristics and spatial distribution of adult human corneal cell subtypes. Sci Rep 2021; 11:16323. [PMID: 34381080 PMCID: PMC8357950 DOI: 10.1038/s41598-021-94933-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 07/19/2021] [Indexed: 12/13/2022] Open
Abstract
Bulk RNA sequencing of a tissue captures the gene expression profile from all cell types combined. Single-cell RNA sequencing identifies discrete cell-signatures based on transcriptomic identities. Six adult human corneas were processed for single-cell RNAseq and 16 cell clusters were bioinformatically identified. Based on their transcriptomic signatures and RNAscope results using representative cluster marker genes on human cornea cross-sections, these clusters were confirmed to be stromal keratocytes, endothelium, several subtypes of corneal epithelium, conjunctival epithelium, and supportive cells in the limbal stem cell niche. The complexity of the epithelial cell layer was captured by eight distinct corneal clusters and three conjunctival clusters. These were further characterized by enriched biological pathways and molecular characteristics which revealed novel groupings related to development, function, and location within the epithelial layer. Moreover, epithelial subtypes were found to reflect their initial generation in the limbal region, differentiation, and migration through to mature epithelial cells. The single-cell map of the human cornea deepens the knowledge of the cellular subsets of the cornea on a whole genome transcriptional level. This information can be applied to better understand normal corneal biology, serve as a reference to understand corneal disease pathology, and provide potential insights into therapeutic approaches.
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Affiliation(s)
- Ann J Ligocki
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Wen Fury
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | | | | | - Tao Yang
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Min Ni
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Yu Bai
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Yi Wei
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | | | - Carmelo Romano
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA.
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17
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Wu J, Wu T, Zheng S, Huang Y, Wang L. Low-dose repeated exposure to chemical surfactant impairs corneal epithelium: When personal cleaning products entering the eye. Exp Eye Res 2021; 210:108696. [PMID: 34228968 DOI: 10.1016/j.exer.2021.108696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 06/17/2021] [Accepted: 06/30/2021] [Indexed: 02/03/2023]
Abstract
Studies have reported that the incidence of ocular discomfort in people who often wear makeup is higher than that in the normal population. The incidence of ocular discomfort of these people may be also related to the daily ocular exposure to chemical surfactants during cleaning. The objectives of this study were to explore morphological and pathological changes in the murine ocular surface after low-dose repeated exposure to disodium cocoamphodiacetate (DC), a kind of chemical surfactant widely used in personal cleaning products, and to investigate the possible mechanisms. DC was administered in low dose (0.1%) to the ocular surface of C56BL/6 once daily for two weeks. We found that there were an increase of sodium fluorescein staining on the cornea, a significant thinning of corneal epithelial thickness, and increased TUNEL-positive cells in corneal epithelium in vivo. DC treatment also modulated the distribution of K14+ and P63+ epithelia from the limbal to the center on the cornea. In cultured murine corneal epithelial progenitor cell line (TKE2), DC treatment induced cell detachment and decreased the activation of Ak strain transforming protein (AKT), and extracellular signal-regulated kinase (ERK). And DC increased TUNEL-positive cells in vitro with increased expression of cleaved Caspase3 and B-cell lymphoma-2 associated X protein (Bax). Our results indicated that repeated low-dose DC exposure on ocular surface caused significant impairment on the structure and viability of the corneal epithelium by inhibiting epithelial proliferation and inducing apoptosis. It provides the foundations to understand the harmful effects of cleaning products daily exposure on the ocular surface.
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Affiliation(s)
- Jie Wu
- Medical School of Chinese PLA, Beijing, 100089, China; Department of Ophthalmology, The Third Medical Center, Chinese PLA General Hospital, Beijing, 100089, China
| | - Tengyun Wu
- Medical School of Chinese PLA, Beijing, 100089, China; Department of Ophthalmology, The Third Medical Center, Chinese PLA General Hospital, Beijing, 100089, China
| | - Shuo Zheng
- Medical School of Chinese PLA, Beijing, 100089, China; Department of Ophthalmology, The Third Medical Center, Chinese PLA General Hospital, Beijing, 100089, China
| | - Yifei Huang
- Department of Ophthalmology, The Third Medical Center, Chinese PLA General Hospital, Beijing, 100089, China
| | - Liqiang Wang
- Department of Ophthalmology, The Third Medical Center, Chinese PLA General Hospital, Beijing, 100089, China.
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18
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Farrelly O, Suzuki-Horiuchi Y, Brewster M, Kuri P, Huang S, Rice G, Bae H, Xu J, Dentchev T, Lee V, Rompolas P. Two-photon live imaging of single corneal stem cells reveals compartmentalized organization of the limbal niche. Cell Stem Cell 2021; 28:1233-1247.e4. [PMID: 33984283 DOI: 10.1016/j.stem.2021.02.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 11/18/2020] [Accepted: 02/16/2021] [Indexed: 12/11/2022]
Abstract
The functional heterogeneity of resident stem cells that support adult organs is incompletely understood. Here, we directly visualize the corneal limbus in the eyes of live mice and identify discrete stem cell niche compartments. By recording the life cycle of individual stem cells and their progeny, we directly analyze their fates and show that their location within the tissue can predict their differentiation status. Stem cells in the inner limbus undergo mostly symmetric divisions and are required to sustain the population of transient progenitors that support corneal homeostasis. Using in situ photolabeling, we captured their progeny exiting the niche before moving centripetally in unison. The long-implicated slow-cycling stem cells are functionally distinct and display local clonal dynamics during homeostasis but can contribute to corneal regeneration after injury. This study demonstrates how the compartmentalized organization of functionally diverse stem cell populations supports the maintenance and regeneration of an adult organ.
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Affiliation(s)
- Olivia Farrelly
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Yoko Suzuki-Horiuchi
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Megan Brewster
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Paola Kuri
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Sixia Huang
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Gabriella Rice
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Hyunjin Bae
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Jianming Xu
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Tzvete Dentchev
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Vivian Lee
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Panteleimon Rompolas
- Department of Dermatology, Department of Cell and Developmental Biology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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19
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Tuck H, Park M, Carnell M, Machet J, Richardson A, Jukic M, Di Girolamo N. Neuronal-epithelial cell alignment: A determinant of health and disease status of the cornea. Ocul Surf 2021; 21:257-270. [PMID: 33766739 DOI: 10.1016/j.jtos.2021.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 02/22/2021] [Accepted: 03/16/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE How sensory neurons and epithelial cells interact with one another, and whether this association can be considered an indicator of health or disease is yet to be elucidated. METHODS Herein, we used the cornea, Confetti mice, a novel image segmentation algorithm for intraepithelial corneal nerves which was compared to and validated against several other analytical platforms, and three mouse models to delineate this paradigm. For aging, eyes were collected from 2 to 52 week-old normal C57BL/6 mice (n ≥ 4/time-point). For wound-healing and limbal stem cell deficiency, 7 week-old mice received a limbal-sparing or limbal-to-limbal epithelial debridement to their right cornea, respectively. Eyes were collected 2-16 weeks post-injury (n=4/group/time-point), corneas procured, immunolabelled with βIII-tubulin, flat-mounted, imaged by scanning confocal microscopy and analyzed for nerve and epithelial-specific parameters. RESULTS Our data indicate that nerve features are dynamic during aging and their curvilinear arrangement align with corneal epithelial migratory tracks. Moderate corneal injury prompted axonal regeneration and recovery of nerve fiber features. Limbal stem cell deficient corneas displayed abnormal nerve morphology, and fibers no longer aligned with corneal epithelial migratory tracks. Mechanistically, we discovered that nerve pattern restoration relies on the number and distribution of stromal-epithelial nerve penetration sites. CONCLUSIONS Microstructural changes to innervation may explain corneal complications related to aging and/or disease and facilitate development of new assays for diagnosis and/or classification of ocular and systemic diseases.
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Affiliation(s)
- Hugh Tuck
- School of Medical Sciences, Mechanisms of Disease and Translational Research, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Mijeong Park
- School of Medical Sciences, Mechanisms of Disease and Translational Research, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Michael Carnell
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Joshua Machet
- School of Medical Sciences, Mechanisms of Disease and Translational Research, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Alexander Richardson
- School of Medical Sciences, Mechanisms of Disease and Translational Research, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Marijan Jukic
- Melbourne School of Population and Global Health, Centre for Health Policy, University of Melbourne, Melbourne, Victoria, 3053, Australia
| | - Nick Di Girolamo
- School of Medical Sciences, Mechanisms of Disease and Translational Research, University of New South Wales, Sydney, New South Wales, 2052, Australia.
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20
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Li Y, Ge L, Chen X, Mao Y, Gu X, Ren B, Zeng Y, Chen M, Chen S, Liu J, Yang Y, Xu H. The common YAP activation mediates corneal epithelial regeneration and repair with different-sized wounds. NPJ Regen Med 2021; 6:16. [PMID: 33772031 PMCID: PMC7997881 DOI: 10.1038/s41536-021-00126-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 02/01/2021] [Indexed: 02/01/2023] Open
Abstract
Regeneration/repair after injury can be endowed by adult stem cells (ASCs) or lineage restricted and even terminally differentiated cells. In corneal epithelium, regeneration after a large wound depends on ASCs (limbal epithelial stem cells, LESCs), whereas repair after a small wound is LESCs-independent. Here, using rat corneal epithelial wounds with different sizes, we show that YAP activation promotes the activation and expansion of LESCs after a large wound, as well as the reprogramming of local epithelial cells (repairing epithelial cells) after a small wound, which contributes to LESCs-dependent and -independent wound healing, respectively. Mechanically, we highlight that the reciprocal regulation of YAP activity and the assembly of cell junction and cortical F-actin cytoskeleton accelerates corneal epithelial healing with different-sized wounds. Together, the common YAP activation and the underlying regulatory mechanism are harnessed by LESCs and lineage-restricted epithelial cells to cope with corneal epithelial wounds with different sizes.
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Affiliation(s)
- Yijian Li
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Lingling Ge
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Xia Chen
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China ,grid.263906.8Southwest University, Chongqing, China
| | - Yumei Mao
- grid.449525.b0000 0004 1798 4472North Sichuan Medical College, Sichuan, China
| | - Xianliang Gu
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Bangqi Ren
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Yuxiao Zeng
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Min Chen
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Siyu Chen
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Jinhua Liu
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Yuli Yang
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
| | - Haiwei Xu
- grid.410570.70000 0004 1760 6682Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China ,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, China
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21
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Guo ZH, Jia YYS, Zeng YM, Li ZF, Lin JS. Transcriptome analysis identifies the differentially expressed genes related to the stemness of limbal stem cells in mice. Gene 2021; 775:145447. [PMID: 33482278 DOI: 10.1016/j.gene.2021.145447] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 12/28/2020] [Accepted: 01/13/2021] [Indexed: 10/22/2022]
Abstract
Limbal stem cells (LSCs) reside in the basal layer of limbal epithelial cells (LECs). They are crucial for maintenance of corneal epithelium homeostasis and corneal wound healing. Their stemness is determined by their gene expression pattern. Despite of several positive identifiers have been reported, the unique biomarker for LSCs still remain elusive. Differentially expressed genes (DEGs) between stem cells and differentiated cells affect the fate of stem cells via specific signaling pathway. In order to understand the DEGs in the LSCs, RNA-seq was firstly conducted using a mouse model. A total of 1907 up-regulated DEGs and 395 down-regulated DEGs were identified in the limbus (L) compared to central cornea (CC) and conjunctiva (Cj). Reliability of the expression of genes from RNA-seq analysis was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence staining. The expression pattern of putative biomarkers was considered to be age-related. In up-regulated DEGs GO analysis, 570 gene ontology (GO) terms were significantly enriched. Five groups of genes related with biological processes from these significantly enriched GO terms comprised ionic transport, regulation of tissue development, muscle contraction, visual perception, and cell adhesion, which were clustered as a weighted similar network. Whereas, in down-regulated DEGs GO analysis, 61 GO terms were significantly enriched and only one group of ATP biosynthesis and metabolic process were clustered. Furthermore, we identified 55 signaling pathways by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database based on up-regulated genes and 14 KEGG pathways based on down-regulated genes. In this study, we provide a landscape of the expression of putative LSCs biomarkers and stemness-related signaling pathways in a mouse model. Our findings could aid in the identification of LSC niche factors that may be related to the stemness of the LSCs.
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Affiliation(s)
- Zhi Hou Guo
- School of Medicine, Huaqiao University, Quanzhou, Fujian 362021, China; Stem Cell Laboratory, The Second Affiliated Hospital of Fujian Medical University, China
| | | | - Yi Ming Zeng
- The Second Affiliated Hospital of Fujian Medical University, China
| | - Zhao Fa Li
- School of Medicine, Huaqiao University, Quanzhou, Fujian 362021, China
| | - Jun Sheng Lin
- School of Medicine, Huaqiao University, Quanzhou, Fujian 362021, China.
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22
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Strinkovsky L, Havkin E, Shalom-Feuerstein R, Savir Y. Spatial correlations constrain cellular lifespan and pattern formation in corneal epithelium homeostasis. eLife 2021; 10:56404. [PMID: 33433326 PMCID: PMC7803374 DOI: 10.7554/elife.56404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 12/08/2020] [Indexed: 02/06/2023] Open
Abstract
Homeostasis in adult tissues relies on the replication dynamics of stem cells, their progenitors and the spatial balance between them. This spatial and kinetic coordination is crucial to the successful maintenance of tissue size and its replenishment with new cells. However, our understanding of the role of cellular replicative lifespan and spatial correlation between cells in shaping tissue integrity is still lacking. We developed a mathematical model for the stochastic spatial dynamics that underlie the rejuvenation of corneal epithelium. Our model takes into account different spatial correlations between cell replication and cell removal. We derive the tradeoffs between replicative lifespan, spatial correlation length, and tissue rejuvenation dynamics. We determine the conditions that allow homeostasis and are consistent with biological timescales, pattern formation, and mutants phenotypes. Our results can be extended to any cellular system in which spatial homeostasis is maintained through cell replication.
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Affiliation(s)
- Lior Strinkovsky
- Department of Physiology, Biophysics and System Biology, Faculty of Medicine, Technion, Haifa, Israel
| | - Evgeny Havkin
- Department of Physiology, Biophysics and System Biology, Faculty of Medicine, Technion, Haifa, Israel
| | - Ruby Shalom-Feuerstein
- Department of Genetics & Developmental Biology, Faculty of Medicine, Technion, Haifa, Israel.,The Rappaport Family Institute for Research in the Medical Sciences, Technion, Haifa, Israel
| | - Yonatan Savir
- Department of Physiology, Biophysics and System Biology, Faculty of Medicine, Technion, Haifa, Israel.,The Rappaport Family Institute for Research in the Medical Sciences, Technion, Haifa, Israel
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23
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Puri S, Sun M, Mutoji KN, Gesteira TF, Coulson-Thomas VJ. Epithelial Cell Migration and Proliferation Patterns During Initial Wound Closure in Normal Mice and an Experimental Model of Limbal Stem Cell Deficiency. Invest Ophthalmol Vis Sci 2021; 61:27. [PMID: 32790859 PMCID: PMC7441334 DOI: 10.1167/iovs.61.10.27] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Purpose Establishing the dynamics of corneal wound healing is of vital importance to better understand corneal inflammation, pathology, and corneal regeneration. Numerous studies have made great strides in investigating multiple aspects of corneal wound healing; however, some aspects remain to be elucidated. This study worked toward establishing (1) if epithelial limbal stem cells (LSCs) are necessary for healing all corneal wounds, (2) the mechanism by which epithelial cells migrate toward the wound, and (3) if centrifugal epithelial cell movement exists. Methods To establish different aspects of corneal epithelial wound healing we subjected mice lacking hyaluronan synthase 2 (previously shown to lack LSCs) and wild-type mice to different corneal debridement injury models. Results Our data show that both LSCs and corneal epithelial cells contribute toward closure of corneal wounds. In wild-type mice, removal of the limbal rim delayed closure of 1.5-mm wounds, and not of 0.75-mm wounds, indicating that smaller wounds do not rely on LSCs as do larger wounds. In mice shown to lack LSCs, removal of the limbal rim did not affect wound healing, irrespective of the wound size. Finally, transient amplifying cells and central epithelial cells move toward a central corneal wound in a centripetal manner, whereas central epithelial cells may move in a centrifugal manner to resurface peripheral corneal wounds. Conclusions Our findings show the dimensions of the corneal wound dictate involvement of LSCs. Our data suggest that divergent findings by different groups on the dynamics of wound healing can be in part owing to differences in the wounding models used.
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Affiliation(s)
- Sudan Puri
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Mingxia Sun
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Kazadi N Mutoji
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Tarsis F Gesteira
- College of Optometry, University of Houston, Houston, Texas, United States
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24
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Ishii R, Yanagisawa H, Sada A. Defining compartmentalized stem cell populations with distinct cell division dynamics in the ocular surface epithelium. Development 2020; 147:dev197590. [PMID: 33199446 PMCID: PMC7758628 DOI: 10.1242/dev.197590] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/04/2020] [Indexed: 12/11/2022]
Abstract
Adult tissues contain label-retaining cells (LRCs), which are relatively slow-cycling and considered to represent a property of tissue stem cells (SCs). In the ocular surface epithelium, LRCs are present in the limbus and conjunctival fornix; however, the character of these LRCs remains unclear, owing to lack of appropriate molecular markers. Using three CreER transgenic mouse lines, we demonstrate that the ocular surface epithelium accommodates spatially distinct populations with different cell division dynamics. In the limbus, long-lived Slc1a3CreER-labeled SCs either migrate centripetally toward the central cornea or slowly expand their clones laterally within the limbal region. In the central cornea, non-LRCs labeled with Dlx1CreER and K14CreER behave as short-lived progenitor cells. The conjunctival epithelium in the bulbar, fornix and palpebral compartment is regenerated by regionally unique SC populations. Severe damage to the cornea leads to the cancellation of SC compartments and conjunctivalization, whereas milder limbal injury induces a rapid increase of laterally expanding clones in the limbus. Taken together, our work defines compartmentalized multiple SC/progenitor populations of the mouse eye in homeostasis and their behavioral changes in response to injury.
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Affiliation(s)
- Ryutaro Ishii
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba 305-8577, Japan
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Hiromi Yanagisawa
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba 305-8577, Japan
- Faculty of Medicine, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Aiko Sada
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba 305-8577, Japan
- International Research Center for Medical Sciences (IRCMS), Kumamoto University, Kumamoto 860-0811, Japan
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25
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Kao WWY. Keratin expression by corneal and limbal stem cells during development. Exp Eye Res 2020; 200:108206. [PMID: 32882212 DOI: 10.1016/j.exer.2020.108206] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 08/24/2020] [Accepted: 08/26/2020] [Indexed: 12/15/2022]
Abstract
Keratins are the forming units of intermediate filaments (IF) that provide mechanical support, and formation of desmosomes between cells and hemi desmosomes with basement membranes for epithelium integrity. Keratin IF are polymers of obligate heterodimer consisting one type I keratin and one type II keratin molecules. There are 54 functional keratin genes in human genome, which are classified into three major groups, i.e., epithelial keratins, hair follicle cell-specific epithelial keratins and hair keratins. Their expression is cell type-specific and developmentally regulated. Corneal epithelium expresses a subgroup of keratins similar to those of epidermal epithelium. Limbal basal stem cells express K5/K14, and K8/K18 and K8/K19 IF suggesting that there probably are two populations of limbal stem cells (LSCs). In human, LSCs at limbal basal layer can directly stratify and differentiate to limbal suprabasal cells that express K3/K12 IF, or centripetally migrate then differentiate to corneal basal transient amplifying cells (TAC) that co-express both K3/K12 and K5/K14 prior to moving upward and assuming suprabasal cells phenotype of only K3/K12 expression that signifies corneal type epithelium differentiation. In rodent, the differentiated cornea epithelial cells express K5/K12 in lieu of K3/K12, because K3 allele exists as a pseudogene and does not encode a functional K3 protein. The basal corneal cells of new-born mice originate from surface ectoderm during embryonic development slowly commit to differentiation of becoming TAC co-expressing K5/K12 and K5/K14 IF. However, the centripetal migration may still occur at a slower rate in young mice, which is accelerated during wound healing. In this review, we will discuss and compare the cornea-specific keratins expression patterns between corneal and epidermal epithelial cells during mouse development, and between human and mouse during development and homeostasis in adult, and pathology caused by a mutation of keratins.
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Affiliation(s)
- Winston W-Y Kao
- Departments of Ophthalmology, University of Cincinnati, Cincinnati, OH, 45267-0838, USA.
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26
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Prina E, Amer MH, Sidney L, Tromayer M, Moore J, Liska R, Bertolin M, Ferrari S, Hopkinson A, Dua H, Yang J, Wildman R, Rose FRAJ. Bioinspired Precision Engineering of Three-Dimensional Epithelial Stem Cell Microniches. ACTA ACUST UNITED AC 2020; 4:e2000016. [PMID: 32329968 DOI: 10.1002/adbi.202000016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/22/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
Maintenance of the epithelium relies on stem cells residing within specialized microenvironments, known as epithelial crypts. Two-photon polymerization (2PP) is a valuable tool for fabricating 3D micro/nanostructures for stem cell niche engineering applications. Herein, biomimetic gelatin methacrylate-based constructs, replicating the precise geometry of the limbal epithelial crypt structures (limbal stem cell "microniches") as an exemplar epithelial niche, are fabricated using 2PP. Human limbal epithelial stem cells (hLESCs) are seeded within the microniches in xeno-free conditions to investigate their ability to repopulate the crypts and the expression of various differentiation markers. Cell proliferation and a zonation in cell phenotype along the z-axis are observed without the use of exogenous signaling molecules. Significant differences in cell phenotype between cells located at the base of the microniche and those situated towards the rim are observed, demonstrating that stem cell fate is strongly influenced by its location within a niche and the geometrical details of where it resides. This study provides insight into the influence of the niche's spatial geometry on hLESCs and demonstrates a flexible approach for the fabrication of biomimetic crypt-like structures in epithelial tissues. This has significant implications for regenerative medicine applications and can ultimately lead to implantable synthetic "niche-based" treatments.
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Affiliation(s)
- Elisabetta Prina
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Mahetab H Amer
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Laura Sidney
- Academic Ophthalmology, Division of Clinical Neuroscience, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Maximilian Tromayer
- Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163, Vienna, 1060, Austria
| | - Jonathan Moore
- School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Robert Liska
- Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163, Vienna, 1060, Austria
| | - Marina Bertolin
- Fondazione Banca degli Occhi del Veneto Onlus, Padiglione Rama, Via Paccagnella 11, Zelarino-Venezia, 30174, Italy
| | - Stefano Ferrari
- Fondazione Banca degli Occhi del Veneto Onlus, Padiglione Rama, Via Paccagnella 11, Zelarino-Venezia, 30174, Italy
| | - Andrew Hopkinson
- Academic Ophthalmology, Division of Clinical Neuroscience, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Harminder Dua
- Academic Ophthalmology, Division of Clinical Neuroscience, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Jing Yang
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Ricky Wildman
- Institute of Advanced Manufacturing, Faculty of Engineering, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Felicity R A J Rose
- Division of Regenerative Medicine and Cellular Therapies, School of Pharmacy, Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, NG7 2RD, UK
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27
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Guo ZH, Zeng YM, Lin JS. Dynamic spatiotemporal expression pattern of limbal stem cell putative biomarkers during mouse development. Exp Eye Res 2020; 192:107915. [PMID: 31911164 DOI: 10.1016/j.exer.2020.107915] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 12/20/2019] [Accepted: 01/02/2020] [Indexed: 02/07/2023]
Abstract
Limbal stem cells (LSCs), a subpopulation of limbal epithelial basal cells, are crucial to the homeostasis and wound healing of corneal epithelium. The identification and isolation of LSCs remains a challenge due to lack of specific LSCs biomarkers. In this study, Haematoxylin-eosin (HE), 4', 6-diamidino-2-phenylindole (DAPI), and immunohistochemistry (IHC) stains were performed on the pre- and post-natal limbus tissues of mice which has the advantage of more controllable in term of sampling age relative to human origin. By morphological analysis, we supported that there is an absence of the Palisades of Vogt (POV) in the mouse. The development of prenatal and neonatal cornea was dominated by its stroma, whereas after eyelids opened at P14, the corneal epithelial cells (CECs) quickly go stratification in response to the liquid-air interface. Based on IHC staining, we found that the expression of LSCs putative biomarkers in limbal epithelial basal cells appeared in chronological order as follows: Vim = p63 > CK14 > CK15 (where = represents same time; > represents earlier), and in corneal epithelial basal cells were weakened in chronological order as follows: Vim > p63 > CK15 > CK14, which might also represent the stemness degree. Furthermore, the dynamic spatial expression of the examined LSCs putative biomarkers during mouse development also implied a temporal restriction. The expression of Vim in epithelial cells of mouse ocular surface occurred during E12-E19 only. The expression of CK15 was completely undetectable in CECs after P14, whereas the others putative molecular markers of LSCs, such as p63 and CK14, still remained weak expression, suggesting that CK15 was suitable to serve as the mouse LSCs biomarkers after P14. In this study, our data demonstrated the dynamic spatiotemporal expression pattern of LSCs putative biomarkers in mouse was age-related and revealed the time spectrum of the expression of LSCs in mouse, which adds in our knowledge by understanding the dynamic expression pattern of biomarkers of stem cells relate to maintenance of their stemness.
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Affiliation(s)
- Zhi Hou Guo
- School of Medicine, Huaqiao University, Quanzhou, 362021, Fujian, China; Stem Cell Laboratory, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, 362000, China.
| | - Yi Ming Zeng
- The Second Affiliated Hospital of Fujian Medical University, China.
| | - Jun Sheng Lin
- School of Medicine, Huaqiao University, Quanzhou, 362021, Fujian, China.
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28
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Peripheral (not central) corneal epithelia contribute to the closure of an annular debridement injury. Proc Natl Acad Sci U S A 2019; 116:26633-26643. [PMID: 31843909 PMCID: PMC6936562 DOI: 10.1073/pnas.1912260116] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
The well-accepted proposition that central corneal epithelia have limited self-renewal and therefore poor regenerative capacity has recently been challenged. However, methods for real-time monitoring to identify which cells take part in this process are scant. In this study, we visualized and quantified the contribution of central versus peripheral/limbal epithelia during annular wound healing by intravital imaging, through an organ culture system, and via computational modeling. Our results verify the contribution of K14+ limbal-derived stem cells and their early progeny in playing a vital role in this process, while central corneal epithelia contribute minimally to wound closure. Corneal epithelia have limited self-renewal and therefore reparative capacity. They are continuously replaced by transient amplifying cells which spawn from stem cells and migrate from the periphery. Because this view has recently been challenged, our goal was to resolve the conflict by giving mice annular injuries in different locations within the corneolimbal epithelium, then spatiotemporally fate-mapping cell behavior during healing. Under these conditions, elevated proliferation was observed in the periphery but not the center, and wounds predominantly resolved by centripetally migrating limbal epithelia. After wound closure, the central corneal epithelium was completely replaced by K14+ limbal-derived clones, an observation supported by high-resolution fluorescence imaging of genetically marked cells in organ-cultured corneas and via computational modeling. These results solidify the essential role of K14+ limbal epithelial stem cells for wound healing and refute the notion that stem cells exist within the central cornea and that their progeny have the capacity to migrate centrifugally.
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29
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Zhang R, Park M, Richardson A, Tedla N, Pandzic E, de Paiva CS, Watson S, Wakefield D, Di Girolamo N. Dose-dependent benzalkonium chloride toxicity imparts ocular surface epithelial changes with features of dry eye disease. Ocul Surf 2019; 18:158-169. [PMID: 31740391 DOI: 10.1016/j.jtos.2019.11.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/15/2019] [Accepted: 11/13/2019] [Indexed: 02/07/2023]
Abstract
PURPOSE Inclusion of the preservative benzalkonium chloride (BAC) in ophthalmic solutions is prevalent, despite the noted potential for exacerbating dry eye disease (DED). Whilst studies incorporating BAC have assessed its' effects as a mouse model of DED, the impact on limbal epithelia is under-studied. Our investigation aimed to comprehensively assess the impact of different BAC dosing regimens and their suitability as a mouse model of DED. METHODS C57BL/6J mice (n = 72) were administered topical BAC (0.05-0.2%) over 7 days. Fluorescein staining, corneal smoothness index, and immuno-histological analyses were applied to determine architectural and cellular changes on the ocular surface following BAC treatment. The effect of BAC (0.0001-0.01%) on cultivated primary mouse corneo-limbal epithelial cells (CLECs) (n = 6) was examined using morphological and functional assays. RESULTS Whilst 0.2% BAC induced severe corneal epithelial defects, 0.1% BAC dispensed once daily over 7 days, induced punctate fluorescein staining without detriment to corneal smoothness. Histochemical staining revealed disorganized basal corneal epithelial cells with enlarged cytoplasmic halos. Furthermore, PAS+ goblet cells were decreased. BAC treatment also modulated K14 expression and distribution within the limbus. In cultured CLEC, BAC triggered cell contraction and vacuolation, increased LDH release and elevated cell necrosis by 4.1-fold. Concentrations of BAC as low as 0.0001% decreased colony formation. CONCLUSIONS This study describes how exposing C57BL/6 mice to BAC induce some clinicopathological features of DED seen in humans, and therefore provides the foundations to explore the consequences on the ocular surface, particularly on limbal epithelia and its' stem cells.
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Affiliation(s)
- Richard Zhang
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia
| | - Mijeong Park
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia
| | - Alexander Richardson
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia
| | - Nicodemus Tedla
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia
| | - Elvis Pandzic
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Cintia S de Paiva
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, 77030, United States
| | - Stephanie Watson
- Save Sight Institute, Discipline of Ophthalmology, Sydney Medical School, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Denis Wakefield
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia
| | - Nick Di Girolamo
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW, 2052, Australia.
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30
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Park M, Richardson A, Pandzic E, Lobo EP, Whan R, Watson SL, Lyons JG, Wakefield D, Di Girolamo N. Visualizing the Contribution of Keratin-14 + Limbal Epithelial Precursors in Corneal Wound Healing. Stem Cell Reports 2018; 12:14-28. [PMID: 30554917 PMCID: PMC6335450 DOI: 10.1016/j.stemcr.2018.11.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/15/2018] [Accepted: 11/16/2018] [Indexed: 12/16/2022] Open
Abstract
It is thought that corneal epithelial injuries resolve by leading-edge cells “sliding” or “rolling” into the wound bed. Here, we challenge this notion and show by real-time imaging that corneal wounds initially heal by “basal cell migration.” The K14CreERT2-Confetti multi-colored reporter mouse was employed to spatially and temporally fate-map cellular behavior during corneal wound healing. Keratin-14+ basal epithelia are forced into the wound bed by increased population pressure gradient from the limbus to the wound edge. As the defect resolves, centripetally migrating epithelia decelerate and replication in the periphery is reduced. With time, keratin-14+-derived clones diminish in number concomitant with their expansion, indicative that clonal evolution aligns with neutral drifting. These findings have important implications for the involvement of stem cells in acute tissue regeneration, in key sensory tissues such as the cornea. Basal limbal epithelial cell proliferation is increased following a corneal injury Corneal epithelial wounds initially heal by K14+ basal cell migration STICS accurately measures clonal dynamics during wound closure Computational modeling confirms the pivotal role of LESCs in wound repair
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Affiliation(s)
- Mijeong Park
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Alexander Richardson
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Elvis Pandzic
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Erwin P Lobo
- School of Mathematics and Statistics, Faculty of Science, University of Sydney, Sydney, NSW 2006, Australia
| | - Renee Whan
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | | | - J Guy Lyons
- Discipline of Dermatology, Bosch Institute, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia; Immune Imaging, Centenary Institute, Sydney, NSW 2006, Australia; Cancer Services, Royal Prince Alfred Hospital, Sydney, NSW 2006, Australia
| | - Denis Wakefield
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Nick Di Girolamo
- Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia.
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31
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A stochastic model of corneal epithelium maintenance and recovery following perturbation. J Math Biol 2018; 78:1245-1276. [PMID: 30478759 DOI: 10.1007/s00285-018-1308-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 11/01/2018] [Indexed: 01/15/2023]
Abstract
Various biological studies suggest that the corneal epithelium is maintained by active stem cells located in the limbus, the so-called limbal epithelial stem cell hypothesis. While numerous mathematical models have been developed to describe corneal epithelium wound healing, only a few have explored the process of corneal epithelium homeostasis. In this paper we present a purposefully simple stochastic mathematical model based on a chemical master equation approach, with the aim of clarifying the main factors involved in the maintenance process. Model analysis provides a set of constraints on the numbers of stem cells, division rates, and the number of division cycles required to maintain a healthy corneal epithelium. In addition, our stochastic analysis reveals noise reduction as the epithelium approaches its homeostatic state, indicating robustness to noise. Finally, recovery is analysed in the context of perturbation scenarios.
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32
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Bojic S, Hallam D, Alcada N, Ghareeb A, Queen R, Pervinder S, Buck H, Amitai Lange A, Figueiredo G, Rooney P, Stojkovic M, Shortt A, Figueiredo FC, Lako M. CD200 Expression Marks a Population of Quiescent Limbal Epithelial Stem Cells with Holoclone Forming Ability. Stem Cells 2018; 36:1723-1735. [PMID: 30157305 DOI: 10.1002/stem.2903] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 08/02/2018] [Accepted: 08/09/2018] [Indexed: 12/12/2022]
Abstract
One of the main challenges in limbal stem cell (LSC) biology and transplantation is the lack of definitive cell surface markers which can be used to identify and enrich viable LSCs. In this study, expression of 361 cell surface proteins was assessed in ex vivo expanded limbal epithelial cells. One marker, CD200 was selected for further characterization based on expression in a small subset of limbal epithelial cells (2.25% ± 0.69%) and reduced expression through consecutive passaging and calcium induced differentiation. CD200 was localized to a small population of cells at the basal layer of the human and mouse limbal epithelium. CD200+ cells were slow cycling and contained the majority of side population (SP) and all the holoclone forming progenitors. CD200+ cells displayed higher expression of LSCs markers including PAX6, WNT7A, CDH3, CK14, CK15, and ABCB5 and lower expression of Ki67 when compared to CD200- . Downregulation of CD200 abrogated the ability of limbal epithelial cells to form holoclones, suggesting an important function for CD200 in the maintenance and/or self-renewal of LSCs. A second marker, CD109, which was expressed in 56.29% ± 13.96% of limbal epithelial cells, was also found to co-localize with ΔNp63 in both human and mouse cornea, albeit more abundantly than CD200. CD109 expression decreased slowly through calcium induced cell differentiation and CD109+ cells were characterized by higher expression of Ki67, when compared to CD109- subpopulation. Together our data suggest that CD200 expression marks a quiescent population of LSCs with holoclone forming potential, while CD109 expression is associated with a proliferative progenitor phenotype. Stem Cells 2018;36:1723-1735.
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Affiliation(s)
- Sanja Bojic
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Dean Hallam
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Nuno Alcada
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Ali Ghareeb
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Rachel Queen
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Sagoo Pervinder
- UCL Institute of Immunology and Transplantation, London, United Kingdom
| | - Harley Buck
- UCL Institute of Immunology and Transplantation, London, United Kingdom
| | - Aya Amitai Lange
- Department of Genetics and Developmental Biology, The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Gustavo Figueiredo
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
| | - Paul Rooney
- Tissue Services, NHS Blood and Transplant, Liverpool, United Kingdom
| | - Miodrag Stojkovic
- Faculty of Medical Sciences, Department of Genetics, University of Kragujevac, Serbia.,SPEBO Medical, Leskovac, Kragujevac, Serbia
| | - Alex Shortt
- UCL Institute of Immunology and Transplantation, London, United Kingdom
| | - Francisco C Figueiredo
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom.,Department of Ophthalmology, Royal Victoria Infirmary, Newcastle University, Newcastle, United Kingdom
| | - Majlinda Lako
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom
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33
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Guo ZH, Zhang W, Jia YYS, Liu QX, Li ZF, Lin JS. An Insight into the Difficulties in the Discovery of Specific Biomarkers of Limbal Stem Cells. Int J Mol Sci 2018; 19:ijms19071982. [PMID: 29986467 PMCID: PMC6073450 DOI: 10.3390/ijms19071982] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 06/25/2018] [Accepted: 06/29/2018] [Indexed: 12/13/2022] Open
Abstract
Keeping the integrity and transparency of the cornea is the most important issue to ensure normal vision. There are more than 10 million patients going blind due to the cornea diseases worldwide. One of the effective ways to cure corneal diseases is corneal transplantation. Currently, donations are the main source of corneas for transplantation, but immune rejection and a shortage of donor corneas are still serious problems. Graft rejection could cause transplanted cornea opacity to fail. Therefore, bioengineer-based corneas become a new source for corneal transplantation. Limbal stem cells (LSCs) are located at the basal layer in the epithelial palisades of Vogt, which serve a homeostatic function for the cornea epithelium and repair the damaged cornea. LSC-based transplantation is one of the hot topics currently. Clinical data showed that the ratio of LSCs to total candidate cells for a transplantation has a significant impact on the effectiveness of the transplantation. It indicates that it is very important to accurately identify the LSCs. To date, several putative biomarkers of LSCs have been widely reported, whereas their specificity is controversial. As reported, the identification of LSCs is based on the characteristics of stem cells, such as a nuclear-to-cytoplasm ratio (N/C) ≥ 0.7, label-retaining, and side population (SP) phenotype. Here, we review recently published data to provide an insight into the circumstances in the study of LSC biomarkers. The particularities of limbus anatomy and histochemistry, the limits of the current technology level for LSC isolation, the heterogeneity of LSCs and the influence of enzyme digestion are discussed. Practical approaches are proposed in order to overcome the difficulties in basic and applied research for LSC-specific biomarkers.
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Affiliation(s)
- Zhi Hou Guo
- School of Medicine, Huaqiao University, Quanzhou 362021, China.
| | - Wei Zhang
- School of Medicine, Huaqiao University, Quanzhou 362021, China.
| | | | - Qing Xiu Liu
- School of Medicine, Huaqiao University, Quanzhou 362021, China.
| | - Zhao Fa Li
- School of Medicine, Huaqiao University, Quanzhou 362021, China.
| | - Jun Sheng Lin
- School of Medicine, Huaqiao University, Quanzhou 362021, China.
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34
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West JD, Mort RL, Hill RE, Morley SD, Collinson JM. Computer simulation of neutral drift among limbal epithelial stem cells of mosaic mice. Stem Cell Res 2018; 30:1-11. [PMID: 29777801 PMCID: PMC6049397 DOI: 10.1016/j.scr.2018.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 05/08/2018] [Accepted: 05/10/2018] [Indexed: 02/08/2023] Open
Abstract
The use of mice that are mosaic for reporter gene expression underlies many lineage-tracing studies in stem cell biology. For example, using mosaic LacZ reporter mice, it was shown that limbal epithelial stem cells (LESCs) around the periphery of the cornea maintain radial sectors of the corneal epithelium and that radial stripe numbers declined with age. Originally, the corneal results were interpreted as progressive, age-related loss or irreversible inactivation of some LESC clones. In this study we used computer simulations to show that these results could also be explained by stochastic replacement of LESCs by neighbouring LESCs, leading to neutral drift of LESC populations. This was shown to reduce the number of coherent clones of LESCs and hence would coarsen the mosaic pattern in the corneal epithelium without reducing the absolute number of LESCs. Simulations also showed that corrected stripe numbers declined more slowly when LESCs were grouped non-randomly and that mosaicism was rarely lost unless simulated LESC numbers were unrealistically low. Possible reasons why age-related changes differ between mosaic corneal epithelia and other systems, such as adrenal cortices and intestinal crypts, are discussed. Age-related reduction of corneal stripes in mosaic mice was simulated. Stem cell loss and/or stem cell replacement reduced simulated stripe numbers. Stem cell replacement, without reducing stem cell numbers, caused neutral drift. Clumping of stem cells into larger groups caused slower decline in stripe numbers. Replacement rarely caused loss of mosaicism unless there were few stem cells.
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Affiliation(s)
- John D West
- Centre for Integrative Physiology, University of Edinburgh Medical School, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
| | - Richard L Mort
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Bailrigg, Lancaster LA1 4YG, UK
| | - Robert E Hill
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK
| | - Steven D Morley
- Division of Health Sciences, University of Edinburgh Medical School, Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - J Martin Collinson
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK
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35
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Kalha S, Shrestha B, Sanz Navarro M, Jones KB, Klein OD, Michon F. Bmi1+ Progenitor Cell Dynamics in Murine Cornea During Homeostasis and Wound Healing. Stem Cells 2018; 36:562-573. [PMID: 29282831 DOI: 10.1002/stem.2767] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 11/27/2017] [Accepted: 12/09/2017] [Indexed: 01/06/2023]
Abstract
The outermost layer of the eye, the cornea, is renewed continuously throughout life. Stem cells of the corneal epithelium reside in the limbus at the corneal periphery and ensure homeostasis of the central epithelium. However, in young mice, homeostasis relies on cells located in the basal layer of the central corneal epithelium. Here, we first studied corneal growth during the transition from newborn to adult and assessed Keratin 19 (Krt19) expression as a hallmark of corneal maturation. Next, we set out to identify a novel marker of murine corneal epithelial progenitor cells before, during and after maturation, and we found that Bmi1 is expressed in the basal epithelium of the central cornea and limbus. Furthermore, we demonstrated that Bmi1+ cells participated in tissue replenishment in the central cornea. These Bmi1+ cells did not maintain homeostasis of the cornea for more than 3 months, reflecting their status as progenitor rather than stem cells. Finally, after injury, Bmi1+ cells fueled homeostatic maintenance, whereas wound closure occurred via epithelial reorganization. Stem Cells 2018;36:562-573.
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Affiliation(s)
- Solja Kalha
- Helsinki Institute of Life Science, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Bideep Shrestha
- Helsinki Institute of Life Science, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Maria Sanz Navarro
- Helsinki Institute of Life Science, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Kyle B Jones
- Department of Orofacial Sciences and Program in Craniofacial Biology, University of California San Francisco, San Francisco, California, USA
| | - Ophir D Klein
- Department of Orofacial Sciences and Program in Craniofacial Biology, University of California San Francisco, San Francisco, California, USA.,Department of Pediatrics and Institute for Human Genetics, University of California San Francisco, San Francisco, California, USA
| | - Frederic Michon
- Helsinki Institute of Life Science, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Keele Medical School and Institute for Science and Technology in Medicine, Keele University, Keele, Staffordshire, England, United Kingdom
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