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Nature Communications Apr 2020In today's clinics, a cell-resolution view of the cornea can be achieved only with a confocal microscope (IVCM) in contact with the eye. Here, we present a common-path...
In today's clinics, a cell-resolution view of the cornea can be achieved only with a confocal microscope (IVCM) in contact with the eye. Here, we present a common-path full-field/spectral-domain OCT microscope (FF/SD OCT), which enables cell-detail imaging of the entire ocular surface in humans (central and peripheral cornea, limbus, sclera, tear film) without contact and in real-time. Real-time performance is achieved through rapid axial eye tracking and simultaneous defocusing correction. Images contain cells and nerves, which can be quantified over a millimetric field-of-view, beyond the capability of IVCM and conventional OCT. In the limbus, palisades of Vogt, vessels, and blood flow can be resolved with high contrast without contrast agent injection. The fast imaging speed of 275 frames/s (0.6 billion pixels/s) allows direct monitoring of blood flow dynamics, enabling creation of high-resolution velocity maps. Tear flow velocity and evaporation time can be measured without fluorescein administration.
Topics: Adult; Angiography; Biomedical Engineering; Blood Flow Velocity; Cornea; Equipment Design; Female; Humans; Limbus Corneae; Male; Microscopy; Optical Imaging; Software; Tomography, Optical Coherence; Young Adult
PubMed: 32313067
DOI: 10.1038/s41467-020-15792-x -
Ophthalmic Research 2013The integrity and normal function of the corneal epithelium are essential for maintaining the cornea's transparency and vision. The existence of a cell population with... (Review)
Review
The integrity and normal function of the corneal epithelium are essential for maintaining the cornea's transparency and vision. The existence of a cell population with progenitor characteristics in the limbus maintains a dynamic of constant epithelial repair and renewal. Currently, cell-based therapies for bio-replacement, such as cultured limbal epithelial transplantation and cultured oral mucosal epithelial transplantation, present very encouraging clinical results for treating limbal stem cell deficiencies. Another emerging therapeutic strategy consists of obtaining and implementing human progenitor cells of different origins using tissue engineering methods. The development of cell-based therapies using stem cells, such as human adult mesenchymal stromal cells, represents a significant breakthrough in the treatment of certain eye diseases and also offers a more rational, less invasive and more physiological approach to ocular surface regeneration.
Topics: Corneal Diseases; Corneal Transplantation; Epithelium, Corneal; Humans; Limbus Corneae; Plastic Surgery Procedures; Stem Cell Transplantation; Stem Cells; Tissue Engineering; Transplantation, Autologous
PubMed: 23257987
DOI: 10.1159/000345257 -
The Ocular Surface Apr 2016The corneal stroma contains a population of mesenchymal cells subjacent to the limbal basement membrane with characteristics of adult stem cells. These 'niche cells'... (Review)
Review
The corneal stroma contains a population of mesenchymal cells subjacent to the limbal basement membrane with characteristics of adult stem cells. These 'niche cells' support limbal epithelial stem cell viability. In culture by themselves, the niche cells display a phenotype typical of mesenchymal stem cells. These stromal stem cells exhibit a potential to differentiate to multiple cell types, including keratocytes, thus providing an abundant source of these rare cells for experimental and bioengineering applications. Stromal stem cells have also shown the ability to remodel pathological stromal tissue, suppressing inflammation and restoring transparency. Because stromal stem cells can be obtained by biopsy, they offer a potential for autologous stem cell treatment for stromal opacities. This review provides an overview of the status of work on this interesting cell population.
Topics: Corneal Stroma; Epithelium, Corneal; Humans; Limbus Corneae; Stem Cells
PubMed: 26804252
DOI: 10.1016/j.jtos.2015.12.006 -
Journal of Cellular and Molecular... Jul 2018Limbal niche cells located in the limbal Palisades of Vogt are mesenchymal stem cells that reside next to limbal basal epithelial cells. Limbal niche cells are... (Review)
Review
Limbal niche cells located in the limbal Palisades of Vogt are mesenchymal stem cells that reside next to limbal basal epithelial cells. Limbal niche cells are progenitors that express embryonic stem cell markers such as Nanog, Nestin, Oct4, Rex1, Sox2 and SSEA4, mesenchymal cell markers such as CD73, CD90 and CD105, and angiogenesis markers such as Flk-1, CD31, CD34, VWF, PDGFRβ and α-SMA, but negative for CD45. In addition, the stemness of limbal niche cells can be maintained during their cell culture in a three-dimension environment. Furthermore, expanded limbal niche cells have the capability to undergo adipogenesis, chondrogenesis, osteogenesis and endogenesis in vitro, indicating that they are in fact a valuable resource of adult progenitors. Furthermore studies on how the limbal niche cells regulate the aforementioned stemness and corneal fate decision are warranted, as those investigations will shed new light on how mesenchymal progenitors reverse limbal stem cell deficiency and lead to new methods for limbal niche cell treatment.
Topics: Animals; Biomarkers; Cell Separation; Humans; Limbus Corneae; Mesenchymal Stem Cells; Neovascularization, Physiologic
PubMed: 29679460
DOI: 10.1111/jcmm.13635 -
International Journal of Molecular... Jan 2020The corneal surface is an essential organ necessary for vision, and its clarity must be maintained. The corneal epithelium is renewed by limbal stem cells, located in... (Review)
Review
The corneal surface is an essential organ necessary for vision, and its clarity must be maintained. The corneal epithelium is renewed by limbal stem cells, located in the limbus and in palisades of Vogt. Palisades of Vogt maintain the clearness of the corneal epithelium by blocking the growth of conjunctival epithelium and the invasion of blood vessels over the cornea. The limbal region can be damaged by chemical burns, physical damage (e.g., by contact lenses), congenital disease, chronic inflammation, or limbal surgeries. The degree of limbus damage is associated with the degree of limbal stem cells deficiency (partial or total). For a long time, the only treatment to restore vision was grafting part of the healthy cornea from the other eye of the patient or by transplanting a cornea from cadavers. The regenerative medicine and stem cell therapies have been applied to restore normal vision using different methodologies. The source of stem cells varies from embryonic stem cells, mesenchymal stem cells, to induced pluripotent stem cells. This review focuses on the use of oral mucosa epithelial stem cells and their use in engineering cell sheets to treat limbal stem cell deficient patients.
Topics: Clinical Trials as Topic; Epithelial Cells; Humans; Limbus Corneae; Mouth Mucosa; Stem Cells; Tissue Engineering
PubMed: 31936462
DOI: 10.3390/ijms21020411 -
Cells Mar 2019Hyaluronan (HA), also termed hyaluronic acid or hyaluronate, is a major component of the extracellular matrix. This non-sulfated glycosaminoglycan plays a key role in... (Review)
Review
Hyaluronan (HA), also termed hyaluronic acid or hyaluronate, is a major component of the extracellular matrix. This non-sulfated glycosaminoglycan plays a key role in cell proliferation, growth, survival, polarization, and differentiation. The diverse biological roles of HA are linked to the combination of HA's physicochemical properties and HA-binding proteins. These unique characteristics have encouraged the application of HA-based hydrogel scaffolds for stem cell-based therapy, a successful method in the treatment of limbal stem cell deficiency (LSCD). This condition occurs following direct damage to limbal stem cells and/or changes in the limbal stem cell niche microenvironment due to intrinsic and extrinsic insults. This paper reviews the physical properties, synthesis, and degradation of HA. In addition, the interaction of HA with other extracellular matrix (ECM) components and receptor proteins are discussed. Finally, studies employing HA-based hydrogel scaffolds in the treatment of LSCD are reviewed.
Topics: Extracellular Matrix; Humans; Hyaluronic Acid; Hydrogels; Limbus Corneae; Stem Cell Transplantation; Tissue Scaffolds
PubMed: 30875861
DOI: 10.3390/cells8030245 -
Contact Lens & Anterior Eye : the... Aug 2019A healthy corneal epithelium, which is essential for proper vision and protection from external pathogens, is continuously replenished throughout life by stem cells... (Review)
Review
A healthy corneal epithelium, which is essential for proper vision and protection from external pathogens, is continuously replenished throughout life by stem cells located at the limbus. In diseased or injured eyes, however, in which stem cells are deficient, severe ocular problems manifest themselves. These are notoriously difficult to manage and as a result the last 20 or so years has seen a number of therapeutic strategies emerge that aim to recover the ocular surface and restore vision in limbal stem cell deficient eyes. The dominant concept involves the generation of laboratory cultivated epithelial cell sheets expanded from small biopsies of the epithelial limbus (for patient or donors) or another non-corneal epithelial tissue such as the oral mucosa. Typically, cells are grown on sterilised human amniotic membrane as a substrate, which then forms part of the graft, or specially formulated plastic culture dishes from which cells sheets can be released by lowering the temperature, and thus the adherence of the plastic to the cells. Overall, clinical results are promising, as is discussed, with new cultivation methodologies and different cell lineages currently being investigated to augment the treatment options for visual disturbance caused by a corneal epithelial limbal stem cell deficiency.
Topics: Cells, Cultured; Corneal Diseases; Epithelium, Corneal; Humans; Limbus Corneae; Recovery of Function; Stem Cell Transplantation; Stem Cells; Vision, Ocular; Visual Acuity
PubMed: 31047800
DOI: 10.1016/j.clae.2019.04.006 -
PLoS Biology Oct 2023The transparent corneal epithelium in the eye is maintained through the homeostasis regulated by limbal stem cells (LSCs), while the nontransparent epidermis relies on...
The transparent corneal epithelium in the eye is maintained through the homeostasis regulated by limbal stem cells (LSCs), while the nontransparent epidermis relies on epidermal keratinocytes for renewal. Despite their cellular similarities, the precise cell fates of these two types of epithelial stem cells, which give rise to functionally distinct epithelia, remain unknown. We performed a multi-omics analysis of human LSCs from the cornea and keratinocytes from the epidermis and characterized their molecular signatures, highlighting their similarities and differences. Through gene regulatory network analyses, we identified shared and cell type-specific transcription factors (TFs) that define specific cell fates and established their regulatory hierarchy. Single-cell RNA-seq (scRNA-seq) analyses of the cornea and the epidermis confirmed these shared and cell type-specific TFs. Notably, the shared and LSC-specific TFs can cooperatively target genes associated with corneal opacity. Importantly, we discovered that FOSL2, a direct PAX6 target gene, is a novel candidate associated with corneal opacity, and it regulates genes implicated in corneal diseases. By characterizing molecular signatures, our study unveils the regulatory circuitry governing the LSC fate and its association with corneal opacity.
Topics: Humans; Limbus Corneae; Cornea; Epithelium, Corneal; Transcription Factors; Cell Differentiation; Corneal Opacity
PubMed: 37856539
DOI: 10.1371/journal.pbio.3002336 -
Indian Journal of Ophthalmology Apr 2020The aim of this study is to compare the outcome and complications in patients who underwent double-head pterygium excision with split conjunctival autograft with and...
PURPOSE
The aim of this study is to compare the outcome and complications in patients who underwent double-head pterygium excision with split conjunctival autograft with and without limbus to limbus orientation.
METHODS
In this retrospective, comparative study, 99 eyes with double-head pterygium which underwent split conjunctival autograft with limbus to limbus orientation (Group 1) and 93 eyes which underwent without limbus to limbus orientation (Group 2) during the period of 2011-2016 were included in this study. The primary outcome compared was the recurrence rate. Other complications were included as secondary outcomes.
RESULTS
Mean age in group 1 and group 2 were 46.84 +/- 10.78 years and 54.38 +/- 11.44 years respectively. M:F was 36:63 in group 1 and 45:48 in group 2 with a mean follow up of 18.30 +/- 7.48 months in group 1 and 17.04 +/- 9.98 months in group 2. Recurrence was seen in 4 cases in each of the 2 groups with the mean time of recurrence being 7 +/- 2.34 months in group 1 and 6 +/- 2.01 months in group 2. Other complications included graft edema, SCH, graft retraction, granuloma, dellen and graft loss with only graft loss being statistically significant between 2 groups.
CONCLUSION
This study provides data that recurrence rates are not different among patients who undergo split conjunctival graft with and without limbal orientation. The strict adherence to maintaining limbus to limbus orientation while managing double-headed pterygia may not be necessary in all cases, especially in those with large defects following excision.
Topics: Adult; Autografts; Conjunctiva; Follow-Up Studies; Humans; Limbus Corneae; Middle Aged; Neoplasm Recurrence, Local; Pterygium; Recurrence; Retrospective Studies; Transplantation, Autologous; Treatment Outcome
PubMed: 32174571
DOI: 10.4103/ijo.IJO_1079_19 -
Stem Cells Translational Medicine Feb 2012The cornea is the clear tissue at the front of the eye that transmits light to the retina at the back of the eye. The cornea is covered by an epithelium and surrounded... (Review)
Review
The cornea is the clear tissue at the front of the eye that transmits light to the retina at the back of the eye. The cornea is covered by an epithelium and surrounded by a narrow band of tissue known as the limbus. The limbus has two important roles in maintaining a healthy corneal epithelium. First, stem cells for the corneal epithelium reside at the limbus and not in the cornea. Second, the limbus acts as a barrier separating the clear avascular corneal epithelium from the surrounding vascular conjunctival tissue. A failure of these limbal functions can result in the painful and blinding disease of limbal stem cell deficiency. In this disease, the corneal epithelium cannot be maintained by the stem cells, and the corneal surface becomes replaced by hazy conjunctival tissue. There are many causes of limbal stem cell deficiency, such as burns to the eye, inflammatory diseases, and hereditary diseases. Current understanding of the pathophysiology of the disease is discussed here. In particular, understanding whether the limbal stem cells are lost or become dysfunctional or indeed whether the limbal microenvironment is disturbed is important when developing appropriate management strategies for the disease.
Topics: Animals; Cell Count; Cell Lineage; Conjunctiva; Corneal Transplantation; Epithelium, Corneal; Humans; Limbus Corneae; Stem Cell Niche; Stem Cell Transplantation; Stem Cells; Transplantation, Homologous
PubMed: 23197757
DOI: 10.5966/sctm.2011-0037