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Stem Cells Translational Medicine Jul 2021Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first emerged in December 2019 and spread quickly causing the coronavirus disease 2019 (COVID-19) pandemic.... (Review)
Review
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first emerged in December 2019 and spread quickly causing the coronavirus disease 2019 (COVID-19) pandemic. Recent single cell RNA-Seq analyses have shown the presence of SARS-CoV-2 entry factors in the human corneal, limbal, and conjunctival superficial epithelium, leading to suggestions that the human ocular surface may serve as an additional entry gateway and infection hub for SARS-CoV-2. In this article, we review the ocular clinical presentations of COVID-19 and the features of the ocular surface that may underline the overall low ocular SARS-CoV-2 infection. We critically evaluate the studies performed in nonhuman primates, ex vivo organ culture ocular models, stem cell derived eye organoids and the differences in infection efficiency observed in different parts of human ocular surface epithelium. Finally, we highlight the additional work that needs to be carried out to understand the immune response of the ocular surface to SARS-CoV-2 infection, which can be translated into prophylactic treatments that may be applied to other organ systems.
Topics: COVID-19; Conjunctiva; Cornea; Eye Diseases; Humans; SARS-CoV-2; Virus Replication
PubMed: 33710758
DOI: 10.1002/sctm.20-0543 -
Cell Proliferation Aug 2007Epithelial stem cells of the eye surface, of the cornea and of the conjunctiva, have the ability to give rise to self renewal and progeny production of differentiated... (Review)
Review
OBJECTIVES
Epithelial stem cells of the eye surface, of the cornea and of the conjunctiva, have the ability to give rise to self renewal and progeny production of differentiated cells with no apparent limit. The two epithelia are separated from each other by the transition zone of the limbus. The mechanisms adopted by stem cells of the two epithelia to accomplish their different characteristics, and how their survival, replacement and unequal division that generates differentiated progeny formation are controlled, are complex and still poorly understood. They can be learned only by understanding how stem cells/progenitors are regulated by their neighbouring cells, that may themselves be differently unspecialised, forming particular microenvironments, known as 'niches'. Stem cells operate by signals and a variety of intercellular interactions and extracellular substrates with adjacent cells in the niche. Technical advances are now making it possible to identify zones in the corneal limbus and conjunctiva that can house stem cells, to isolate and expand them ex vivo and to control their behaviour creating optimal niche conditions. With improvements in biotechnology, regenerative cornea and conjunctiva transplantation using adult epithelial stem cells becomes now a reality.
RESULTS AND CONCLUSIONS
Here we review our current understanding of stem cell niches and illustrate recent significant progress for identification and characterization of adult epithelial stem cells/progenitors at cellular, molecular and mechanistic levels, improvement in cell culture techniques for their selective expansion ex vivo and prospects for a variety of therapeutic applications.
Topics: Adult; Cell Culture Techniques; Conjunctiva; Epithelial Cells; Epithelium, Corneal; Humans; Keratins; Limbus Corneae; Signal Transduction; Stem Cell Transplantation; Stem Cells
PubMed: 17635514
DOI: 10.1111/j.1365-2184.2007.00450.x -
Indian Journal of Ophthalmology Sep 2017Conjunctival biopsies constitute a fairly large number of cases in a typical busy ophthalmic pathology practice. They range from a single biopsy through multiple mapping... (Review)
Review
Conjunctival biopsies constitute a fairly large number of cases in a typical busy ophthalmic pathology practice. They range from a single biopsy through multiple mapping biopsies to assess the extent of a particular pathological process. Like most anatomical sites, the conjunctiva is subject to a very wide range of pathological processes. This article will cover key, commonly encountered nonneoplastic and neoplastic entities. Where relevant, sections will include recommendations on how best to submit specimens to the ophthalmic pathology laboratory and the relevance of up-to-date molecular techniques.
Topics: Biopsy; Conjunctiva; Conjunctival Diseases; Humans
PubMed: 28905821
DOI: 10.4103/ijo.IJO_364_16 -
Middle East African Journal of... 2015We are currently in the midst of a surge in interest in glaucoma surgery. Novel pathways for reducing intraocular pressure (IOP) have been tried with various levels of... (Review)
Review
We are currently in the midst of a surge in interest in glaucoma surgery. Novel pathways for reducing intraocular pressure (IOP) have been tried with various levels of success over the last few years. While the trabecular bypass and suprachoroidal approaches have captured much of the attention, filtering aqueous into the sub-conjunctival space remains the gold standard for lowering IOP. This review attempts to focus on current research in surgical methods to enhance filtration by potentially improving on tried and tested methods like the trabeculectomy, deep sclerectomy, and tube surgeries.
Topics: Conjunctiva; Glaucoma; Humans; Intraocular Pressure; Sclerostomy; Trabeculectomy
PubMed: 25624674
DOI: 10.4103/0974-9233.148349 -
Stem Cell Research & Therapy Oct 2023T helper 2 (Th2) cells are thought to play critical roles in allergic conjunctivitis (AC). They release inflammatory cytokines to promote an allergic response in AC. Due...
BACKGROUND
T helper 2 (Th2) cells are thought to play critical roles in allergic conjunctivitis (AC). They release inflammatory cytokines to promote an allergic response in AC. Due to individual heterogeneity and long-term chronic management, current therapies do not always effectively control AC. Mesenchymal stem cells (MSCs) have been shown to be effective in treating allergy-related disorders, but it is unclear how exactly the Th2-mediated allergic response is attenuated. This study aims to elucidate the therapeutic effect and mechanism of the human umbilical cord MSCs (hUCMSCs) in a mouse model of experimental AC (EAC).
METHODS
A mouse EAC model was established by inoculating short ragweed (SRW) pollen. After the SRW pollen challenge, the mice received a single subconjunctival or tail vein injection of 2 × 10 hUCMSCs, or subconjunctival injection of hUCMSCs conditioned medium (hUCMSC-CM), and dexamethasone eye drops was used as positive control; subsequent scratching behavior and clinical symptoms were assessed. Immunostaining and flow cytometry were carried out to show allergic reactions and the activation of CD4 + T cell subsets in the conjunctiva and cervical lymph nodes (CLNs). Gene expression was determined by RNA-seq and further verified by qRT-PCR and Western blot. Co-culture assays were performed to explore the regulatory role of hUCMSCs in the differentiation of CD4 + naive T cells (Th0) into Th2 cells.
RESULTS
Subconjunctival administration of hUCMSCs resulted in fewer instances of scratching and lower inflammation scores in EAC mice compared to the tail vein delivery, hUCMSC-CM and control groups. Subconjunctival administration of hUCMSCs reduced the number of activated mast cells and infiltrated eosinophils in the conjunctiva, as well as decreased the number of Th2 cells in CLNs. After pretreatment with EAC mouse serum in vitro to mimic the in vivo milieu, hUCMSCs were able to inhibit the differentiation of Th0 into Th2 cells. Further evidence demonstrated that repression of Th2 cell differentiation by hUCMSCs is mediated by CRISPLD2 through downregulation of STAT6 phosphorylation. Additionally, hUMCSCs were able to promote the differentiation of Th0 cells into regulatory T cells in CLNs of EAC mice.
CONCLUSIONS
Subconjunctival injection of hUCMSCs suppressed the Th2-allergic response and alleviated clinical symptoms. This study provides not only a potential therapeutic target for the treatment of AC but also other T cell-mediated diseases.
Topics: Humans; Animals; Mice; Conjunctivitis, Allergic; Conjunctiva; Cytokines; Disease Models, Animal; Mesenchymal Stem Cells; Umbilical Cord
PubMed: 37784129
DOI: 10.1186/s13287-023-03484-4 -
International Journal of... 2012Human pterygium is made up of chronic proliferative fibro-vascular tissue growing on the ocular surface. This disease exhibits both degenerative and hyperplastic... (Review)
Review
Human pterygium is made up of chronic proliferative fibro-vascular tissue growing on the ocular surface. This disease exhibits both degenerative and hyperplastic properties. Some fibroangiogenic factors have recently been shown to play a potential role in fibrovascular diseases via the angiogenesis process. The aim of this study is to evaluate VEGF, TGF-β and PGE₂ expression in the epithelial, endothelial and stromal cells of human pterygium and normal conjunctiva in order to determine whether these factors participate in the development of pterygium. Ten specimens from patients with pterygium and two normal conjunctivas (cadavers) were analyzed by immunohistochemistry using specific antibodies against these growth factors. The technique used was ABC/HRP (Avidin complexed with biotinylated peroxidase). Immunoreactivity of VEGF was significantly increased in the epithelium, vascular endothelium and stromal cells in primary pterygium as compared with normal conjunctiva. A moderate expression of TGF-β in the pterygium was observed in the epithelial and stromal layers. On the contrary, immunolabeling of this growth factor in the human normal conjunctiva was weak. PGE₂ was strongly expressed in the epithelium of patients with pterygium, as in control conjunctival tissues, and the immunolabeling was moderate in the stroma from the same patients. Our results suggest that these growth factors may contribute to the progression of primary pterygium by increasing angiogenesis, thus leading to the formation of new blood vessels from the pre-existing vasculature. We conclude that VEGF, TGF-β and PGE₂ may be potential therapeutic targets in the treatment of this disease although proof of this evidence requires further studies.
Topics: Aged; Aged, 80 and over; Biomarkers; Case-Control Studies; Conjunctiva; Dinoprostone; Endothelial Cells; Epithelial Cells; Female; Humans; Hyperplasia; Immunohistochemistry; Male; Middle Aged; Pterygium; Stromal Cells; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A
PubMed: 23058011
DOI: 10.1177/039463201202500307 -
Indian Journal of Ophthalmology Jul 1980
Topics: Adolescent; Adult; Child; Conjunctiva; Cysticercus; Female; Humans; Male; Taenia
PubMed: 7216352
DOI: No ID Found -
Scientific Reports Dec 2019Micropulse transscleral cyclophotocoagulation (MP-TCP) is increasingly being used as an initial procedure prior to conjunctival filtration surgeries. However, it is...
Micropulse transscleral cyclophotocoagulation (MP-TCP) is increasingly being used as an initial procedure prior to conjunctival filtration surgeries. However, it is uncertain whether MP-TCP may cause inflammation and scarring of the bulbar conjunctiva. Thus, we aimed to study the histological effects of MP-TCP (compared to controls and continuous wave [CW]-TCP) on the conjunctiva. Our study included 10 Dutch Belted Rabbits that underwent TCP in their right eyes (n = 5, MP-TCP; n = 5, CW-TCP), while their left eyes served as controls. The rabbits were euthanised at 4 weeks, and their dissected globes underwent histopathological and immunohistochemical examination. We observed greater conjunctival inflammation in MP-TCP or CW-TCP-treated eyes compared to controls, but not between each other. The majority of the lymphocytic infiltrates were CD4 T-cells. Increased conjunctival fibrosis was evident in MP-TCP or CW-TCP-treated eyes, to similar extents, compared to controls. However, the increased staining for myofibroblasts was not statistically significant in TCP-treated eyes. We concluded that MP-TCP causes significantly greater overall conjunctival inflammation and scarring compared to controls, similar to CW-TCP. As these are risk-factors for fibrosis and failure of the conjunctival bleb, further studies are required to explore the effect, if any, of post-TCP conjunctival changes on future bleb morphology and survival.
Topics: Animals; Cicatrix; Ciliary Body; Conjunctiva; Female; Glaucoma; Intraocular Pressure; Laser Coagulation; Rabbits; Sclera
PubMed: 31822709
DOI: 10.1038/s41598-019-55102-0 -
Cornea Feb 2022The purpose of this article was to describe a modification to the traditional Gundersen flap technique that expands eligible eyes to include those with severe...
PURPOSE
The purpose of this article was to describe a modification to the traditional Gundersen flap technique that expands eligible eyes to include those with severe conjunctival scarring and to report results from a clinical case.
METHODS
A 68-year-old woman with a history of herpes simplex keratitis, multiple failed penetrating keratoplasties, lagophthalmos, persistent epithelial defect, and low visual potential in the left eye presented for the evaluation of a Gundersen flap. Severe superior bulbar conjunctival scarring precluded a traditional approach. A modified Gundersen flap technique using a contiguous flap of inferior palpebral-bulbar conjunctiva extending from the inferior tarsal border to the limbus was devised and performed.
RESULTS
The modified Gundersen flap technique successfully stabilized the ocular surface, obviating the need for a cosmetically disfiguring permanent tarsorrhaphy or an evisceration.
CONCLUSIONS
This modified Gundersen flap technique expands the indications to eyes with severe conjunctival scarring and can be offered in eyes with previous trabeculectomies, glaucoma drainage implants, and scleral buckles, which were previously excluded from the globe-preserving option.
Topics: Aged; Cicatrix; Conjunctiva; Conjunctival Diseases; Female; Humans; Ophthalmologic Surgical Procedures; Postoperative Complications; Surgical Flaps
PubMed: 35037907
DOI: 10.1097/ICO.0000000000002823 -
Transactions of the American... 2004Many ophthalmologists believe that long-term use of topically applied glaucoma medications can adversely affect results of fistulizing surgery. This presentation... (Review)
Review
PURPOSE
Many ophthalmologists believe that long-term use of topically applied glaucoma medications can adversely affect results of fistulizing surgery. This presentation critically analyzes the published studies most often cited in support of this view to determine whether this conclusion is justified.
METHODS
Morphologic effects of long-term treatment with antiglaucoma drugs on the conjunctiva and Tenon's capsule in glaucomatous patients have been studied. The results of these studies encouraged investigators to examine the influence of prior therapy on the success of trabeculectomy performed in patients with open-angle glaucoma. From this work, many have concluded that long-term use of topically applied glaucoma medications can adversely affect the results of fistulizing surgery. These results and conclusions are summarized and critically analyzed to determine whether this conclusion is justified.
RESULTS
Morphologic studies describe increased numbers of macrophages, fibroblasts, lymphocytes, and mast cells in conjunctival and Tenon's capsule specimens taken from patients receiving long-term antiglaucoma drugs. These findings suggest a potential for more inflammation and subsequent scarring following trabeculectomies in these patients. Efforts to confirm the clinical relevance of these histologic findings in open-angle glaucoma patients with a history of long-term antiglaucoma medication prior to surgery have been published. These retrospective, nonrandomized, unmasked studies of open-angle glaucoma patients include treatment groups and surgeries that are not comparable. In addition, the medical treatments within these studies do not reflect our current approaches to the medical management of open-angle glaucoma.
CONCLUSIONS
At present, there is no convincing clinical evidence that long-term medical treatments influence the success of contemporary trabeculectomy surgery performed on open-angle glaucoma patients.
Topics: Aged; Chemotherapy, Adjuvant; Conjunctiva; Connective Tissue; Glaucoma; Humans; Middle Aged; Trabeculectomy; Treatment Outcome
PubMed: 15747760
DOI: No ID Found