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Verma S, Moreno IY, Trapp ME, Ramirez L, Gesteira TF, Coulson-Thomas VJ. Meibomian gland development: Where, when and how? Differentiation 2023; 132:41-50. [PMID: 37202278 PMCID: PMC11259229 DOI: 10.1016/j.diff.2023.04.005] [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: 10/31/2022] [Revised: 04/10/2023] [Accepted: 04/30/2023] [Indexed: 05/20/2023]
Abstract
The Meibomian gland (MG) is an indispensable adnexal structure of eye that produces meibum, an important defensive component for maintaining ocular homeostasis. Normal development and maintenance of the MGs is required for ocular health since atrophic MGs and disturbances in composition and/or secretion of meibum result in major ocular pathologies, collectively termed as Meibomian gland dysfunction (MGD). Currently available therapies for MGD merely provide symptomatic relief and do not treat the underlying deficiency of the MGs. Hence, a thorough understanding of the timeline of MG development, maturation and aging is required for regenerative purposes along with signaling molecules & pathways controlling proper differentiation of MG lineage in mammalian eye. Understanding the factors that contribute to the development of MGs, developmental abnormalities of MGs, and changes in the quality & quantity of meibum with developing phases of MGs are essential for developing potential treatments for MGD. In this review, we compiled a timeline of events and the factors involved in the structural and functional development of MGs and the associated developmental defects of MGs during development, maturation and aging.
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Affiliation(s)
- Sudhir Verma
- College of Optometry, University of Houston, Houston, TX, USA; Department of Zoology, Deen Dayal Upadhyaya College, University of Delhi, New Delhi, India
| | - Isabel Y Moreno
- College of Optometry, University of Houston, Houston, TX, USA
| | - Morgan E Trapp
- College of Optometry, University of Houston, Houston, TX, USA
| | - Luis Ramirez
- College of Optometry, University of Houston, Houston, TX, USA
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Bonnet C, Ruiz M, Gonzalez S, Tseng CH, Bourges JL, Behar-Cohen F, Deng SX. Single mRNA detection of Wnt signaling pathway in the human limbus. Exp Eye Res 2023; 229:109337. [PMID: 36702232 DOI: 10.1016/j.exer.2022.109337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/02/2022] [Accepted: 11/23/2022] [Indexed: 01/24/2023]
Abstract
Limbal epithelial stem/progenitor cells (LSCs) are adult stem cells located at the limbus, tightly regulated by their close microenvironment. It has been shown that Wnt signaling pathway is crucial for LSCs regulation. Previous differential gene profiling studies confirmed the preferential expression of specific Wnt ligands (WNT2, WNT6, WNT11, WNT16) and Wnt inhibitors (DKK1, SFRP5, WIF1, FRZB) in the limbal region compared to the cornea. Among all frizzled receptors, frizzled7 (Fzd7) was found to be preferentially expressed in the basal limbal epithelium. However, the exact localization of Wnt signaling molecules-producing cells in the limbus remains unknown. The current study aims to evaluate the in situ spatial expression of these 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7. Wnt ligands, DKK1, and Fzd7 expression were scattered within the limbal epithelium, at a higher abundance in the basal layer than the superficial layer. SFRP5 expression was diffuse among the limbal epithelium, whereas WIF1 and FRZB expression was clustered at the basal limbal epithelial layer corresponding to the areas of high levels of Fzd7 expression. Quantitation of the fluorescence intensity showed that all 4 Wnt ligands, 3 Wnt inhibitors (WIF1, DKK1, FRZB), and Fzd7 were highly expressed at the basal layer of the limbus, then in a decreasing gradient toward the superficial layer (P < 0.05). The expression levels of all 4 Wnt ligands, FRZB, and Fzd7 in the basal epithelial layer were higher in the limbus than the central cornea (P < 0.05). All 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7 were also highly expressed in the limbal stroma immediately below the epithelium but not in the corneal stroma (P < 0.05). In addition, Fzd7 had a preferential expression in the superior limbus compared to other limbal quadrants (P < 0.05). Taken together, the unique expression patterns of the Wnt molecules in the limbus suggests the involvement of both paracrine and autocrine effects in LSCs regulation, and a fine balance between Wnt activators and inhibitors to govern LSC fate.
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Affiliation(s)
- Clémence Bonnet
- Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA; INSERM, UMRS1138, Team 17, From Physiopathology of Ocular Diseases to Clinical Development, Centre de Recherche des Cordeliers, Paris University, And Cornea Departement, Cochin Hospital, AP-HP, F-75014, Paris, France
| | - Maxime Ruiz
- Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Sheyla Gonzalez
- Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Chi-Hong Tseng
- David Geffen School of Medicine, Division of General Internal Medicine and Health Services Research, University of California, Los Angeles, USA
| | - Jean-Louis Bourges
- INSERM, UMRS1138, Team 17, From Physiopathology of Ocular Diseases to Clinical Development, Centre de Recherche des Cordeliers, Paris University, And Cornea Departement, Cochin Hospital, AP-HP, F-75014, Paris, France
| | - Francine Behar-Cohen
- INSERM, UMRS1138, Team 17, From Physiopathology of Ocular Diseases to Clinical Development, Centre de Recherche des Cordeliers, Paris University, And Cornea Departement, Cochin Hospital, AP-HP, F-75014, Paris, France
| | - Sophie X Deng
- Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles, CA, USA.
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Expression of R-spondins/Lgrs in development of movable craniofacial organs. Gene Expr Patterns 2021; 41:119195. [PMID: 34126267 DOI: 10.1016/j.gep.2021.119195] [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: 02/13/2021] [Revised: 04/26/2021] [Accepted: 06/02/2021] [Indexed: 01/26/2023]
Abstract
Wnt signaling plays a critical role in the development of many organs, including the major movable craniofacial organs tongue, lip, and eyelid. Four members of the R-spondin family (Rspo1-4) bind to Lgr4/5/6 to regulate the activation of Wnt signaling. However, it is not fully understood how Rspos/Lgrs regulate Wnt signaling during the development of movable craniofacial organs. To address this question, we examined the expression of Rspos, Lgrs, and Axin2 (major mediator of canonical Wnt signaling) during tongue, lip, and eyelid development. The expression of Axin2, Rspos and Lgrs was observed in many similar regions, suggesting that Rspos likely activate canonical Wnt signaling through the Lgr-dependent pathway in these regions. Lgr expression was not detected in regions where Axin2 and Rspos were expressed, suggesting that Rspos might activate canonical Wnt signaling through the Lgr-independent pathway in these regions. In addition, the expression of Rspos and Lgrs were observed in some other regions where Axin2 was not expressed, suggesting the possibility that Rspos and/or Lgrs are involved in non-canonical Wnt signaling or the Wnt-independent pathway. Thus, we identified a dynamic spatiotemporal expression pattern of Rspos and Lgrs during the development of the eyelid, tongue, and lip.
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