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Boero E, Mnich ME, Manetti AGO, Soldaini E, Grimaldi L, Bagnoli F. Human Three-Dimensional Models for Studying Skin Pathogens. Curr Top Microbiol Immunol 2021; 430:3-27. [PMID: 32601967 DOI: 10.1007/82_2020_219] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Skin is the most exposed surface of the human body, separating the microbe-rich external environment, from the sterile inner part. When skin is breached or its homeostasis is perturbed, bacterial, fungal and viral pathogens can cause local infections or use the skin as an entry site to spread to other organs. In the last decades, it has become clear that skin provides niches for permanent microbial colonization, and it actively interacts with microorganisms. This crosstalk promotes skin homeostasis and immune maturation, preventing expansion of harmful organisms. Skin commensals, however, are often found to be skin most prevalent and dangerous pathogens. Despite the medical interest, mechanisms of colonization and invasion for most skin pathogens are poorly understood. This limitation is due to the lack of reliable skin models. Indeed, animal models do not adequately mimic neither the anatomy nor the immune response of human skin. Human 3D skin models overcome these limitations and can provide new insights into the molecular mechanisms of microbial pathogenesis. Herein, we address the strengths and weaknesses of different types of human skin models and we review the main findings obtained using these models to study skin pathogens.
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Affiliation(s)
| | | | | | | | - Luca Grimaldi
- Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
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Kashem SW, Kaplan DH. Skin Immunity to Candida albicans. Trends Immunol 2016; 37:440-450. [PMID: 27178391 DOI: 10.1016/j.it.2016.04.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 04/20/2016] [Accepted: 04/21/2016] [Indexed: 12/20/2022]
Abstract
Candida albicans is a dimorphic commensal fungus that colonizes healthy human skin, mucosa, and the reproductive tract. C. albicans is also a predominantly opportunistic fungal pathogen, leading to disease manifestations such as disseminated candidiasis and chronic mucocutaneous candidiasis (CMC). The differing host susceptibilities for the sites of C. albicans infection have revealed tissue compartmentalization with tailoring of immune responses based on the site of infection. Furthermore, extensive studies of host genetics in rare cases of CMC have identified conserved genetic pathways involved in immune recognition and the response to the extracellular pathogen. We focus here on human and mouse skin as a site of C. albicans infection, and we review established and newly discovered insights into the cellular pathways that promote cutaneous antifungal immunity.
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Affiliation(s)
- Sakeen W Kashem
- Department of Dermatology, Center for Immunology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Daniel H Kaplan
- Departments of Dermatology and Immunology, University of Pittsburgh, Pittsburgh, PA 15216, USA.
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Tapia CV, Falconer M, Tempio F, Falcón F, López M, Fuentes M, Alburquenque C, Amaro J, Bucarey SA, Di Nardo A. Melanocytes and melanin represent a first line of innate immunity against Candida albicans. Med Mycol 2014; 52:445-54. [PMID: 24934806 DOI: 10.1093/mmy/myu026] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Melanocytes are dendritic cells located in the skin and mucosae that synthesize melanin. Some infections induce hypo- or hyperpigmentation, which is associated with the activation of Toll-like receptors (TLRs), especially TLR4. Candida albicans is an opportunist pathogen that can switch between blastoconidia and hyphae forms; the latter is associated with invasion. Our objectives in this study were to ascertain whether C. albicans induces pigmentation in melanocytes and whether this process is dependent on TLR activation, as well as relating this with the antifungal activity of melanin as a first line of innate immunity against fungal infections. Normal human melanocytes were stimulated with C. albicans supernatants or with crude extracts of the blastoconidia or hyphae forms, and pigmentation and TLR2/TLR4 expression were measured. Expression of the melanosomal antigens Melan-A and gp100 was examined for any correlation with increased melanin levels or antifungal activity in melanocyte lysates. Melanosomal antigens were induced earlier than cell pigmentation, and hyphae induced stronger melanization than blastoconidia. Notably, when melanocytes were stimulated with crude extracts of C. albicans, the cell surface expression of TLR2/TLR4 began at 48 h post-stimulation and peaked at 72 h. At this time, blastoconidia induced both TLR2 and TLR4 expression, whereas hyphae only induced TLR4 expression. Taken together, these results suggest that melanocytes play a key role in innate immune responses against C. albicans infections by recognizing pathogenic forms of C. albicans via TLR4, resulting in increased melanin content and inhibition of infection.
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Affiliation(s)
- Cecilia V Tapia
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina Universidad de Chile, Santiago, Chile Servicio de Laboratorio, Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Maryanne Falconer
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina Universidad de Chile, Santiago, Chile
| | - Fabián Tempio
- Programa de Inmunología, ICBM, Facultad de Medicina Universidad de Chile
| | - Felipe Falcón
- Programa de Inmunología, ICBM, Facultad de Medicina Universidad de Chile
| | - Mercedes López
- Programa de Inmunología, ICBM, Facultad de Medicina Universidad de Chile
| | - Marisol Fuentes
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina Universidad de Chile, Santiago, Chile
| | - Claudio Alburquenque
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina Universidad de Chile, Santiago, Chile
| | - José Amaro
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina Universidad de Chile, Santiago, Chile
| | - Sergio A Bucarey
- Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - Anna Di Nardo
- Division of Dermatology, Department of Medicine, University of California, San Diego, and Veterans Administration, San Diego Healthcare System, San Diego, California, USA
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