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Shim J, Park JH, Lee T, Lee D, Jang KT. The concept of onychodermis containing onychofibroblasts has histological (microanatomical), immunohistochemical as well as molecular basis. J Cutan Pathol 2024; 51:911-918. [PMID: 39044464 DOI: 10.1111/cup.14696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 06/02/2024] [Accepted: 07/10/2024] [Indexed: 07/25/2024]
Abstract
The terms "onychofibroblast" (nail-specific fibroblast) and onychodermis (nail-specific dermis) were first introduced in 2006 and 2012, respectively, based on distinctive histologic and immunohistochemical features from the dermis of the surrounding skin and have been demonstrated in multiple studies. Recently, based on molecular research, the definition of onychodermis containing onychofibroblasts has been expanded to encompass the area located between the nail matrix and bed epithelium and periosteum. Single-cell RNA sequencing and in situ hybridization demonstrated that onychofibroblasts within the onychodermis express the genes including RSPO4, MSX1, WIF-1, and BMP5, which are implicated in nail formation and/or in disorders with nail phenotype. A mutation in RSPO4, a component of the Wnt signaling pathway, causes anonychia congenita. Nail matrix onychodermis and nail bed onychodermis share many similar characteristics which differ from the surrounding normal dermis of the skin. Comparative spatial transcriptomic and single-cell analyses of human nail units and hair follicles suggest that onychodermis is the counterpart of follicular dermal papilla, which plays a key role in hair follicle growth and morphogenesis. Onychomatricoma, as a nail-specific tumor, has been demonstrated to be a mesenchymal tumor that originates from onychofibroblasts and is associated with the upregulation of Wnt signaling. Collectively, the onychodermis and onychofibroblasts play crucial roles in nail development and these specialized nail mesenchymal elements are key components in the pathogenesis of onychomatricoma. The concept of onychodermis containing onychofibroblasts is very important for nail biology and pathology.
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Affiliation(s)
- Joonho Shim
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Ji-Hye Park
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Taemin Lee
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Dongyoun Lee
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kee-Taek Jang
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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2
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Lee SH, Platt S, Lim CH, Ito M, Myung P. The development of hair follicles and nail. Dev Biol 2024; 513:3-11. [PMID: 38759942 DOI: 10.1016/j.ydbio.2024.05.010] [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: 11/27/2023] [Revised: 05/06/2024] [Accepted: 05/14/2024] [Indexed: 05/19/2024]
Abstract
The hair follicle and nail unit develop and regenerate through epithelial-mesenchymal interactions. Here, we review some of the key signals and molecular interactions that regulate mammalian hair follicle and nail formation during embryonic development and how these interactions are reutilized to promote their regeneration during adult homeostasis and in response to skin wounding. Finally, we highlight the role of some of these signals in mediating human hair follicle and nail conditions.
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Affiliation(s)
- Soung-Hoon Lee
- The Ronald O. Perelman Department of Dermatology and Department of Cell Biology, New York University School of Medicine, New York, NY, USA
| | - Sarah Platt
- Department of Dermatology, Yale School of Medicine, New Haven, CT, USA
| | - Chae Ho Lim
- The Ronald O. Perelman Department of Dermatology and Department of Cell Biology, New York University School of Medicine, New York, NY, USA
| | - Mayumi Ito
- The Ronald O. Perelman Department of Dermatology and Department of Cell Biology, New York University School of Medicine, New York, NY, USA
| | - Peggy Myung
- Department of Dermatology, Yale School of Medicine, New Haven, CT, USA; Department of Pathology, Yale School of Medicine, New Haven, CT, USA.
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3
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Perrin C. Nail Telocytes: Identification, Potential Physiological Function, and Role in Pathology: A Reappraisal of the So-Called Onychofibroblasts/Onychodermis. Am J Dermatopathol 2024; 46:346-352. [PMID: 38574066 DOI: 10.1097/dad.0000000000002704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
ABSTRACT Some authors have suggested that the fibroblasts of the nail mesenchyme (onychofibroblasts) can be distinguished from skin fibroblasts by their high expression of CD10. My 2015 study documented the presence of a relatively sparse CD34 + /CD10 + dendritic subpopulation in the dermis and hypodermis of the matrix. For some time now, my hypothesis has been that these interstitial dendritic mesenchymal cells of the matrix correspond to telocytes. Telocytes have been described as peculiar interstitial dendritic cells present in the mesenchymal tissue of numerous organs, including the skin, but their presence and characteristics in the nail unit have not been explored. This study was undertaken to more comprehensively investigate the existence and characteristics of nail telocytes. A series of 20 normal adult nail units were examined with a combination of morphological and immunohistochemical analyses. The matrix dermis contained a sparse subpopulation of CD34 + /CD10 + elongated telocytes with a higher density in the lunular region and, at this distal level, a change in their immunohistochemical profile, resulting in a progressive loss of CD34 expression. The matrix hypodermis showed CD34 + /CD10 + telocytes in their classical elongated aspect, which acquired, especially in the distal fibromyxoid area of the thumb, an oval to round morphology with multiple intracytoplasmic vacuoles. The characteristic dynamic immunophenotypic profile of the dermal telocytes with a progressive distal loss of the defining molecule CD34 was equally observed in the distal hypodermis. The nail bed dermis was thick with a dense fibrous connective tissue. A reticular network of CD34 - /CD10 + telocytes was present in the superficial dermis of the proximal nail bed. The mesenchymal cells of the deep part of the proximal nail bed dermis and the entire distal nail bed dermis were CD34 - /CD10 - . The adult nail mesenchyme is composed of 3 microanatomically distinct regions. Only the thumb has a distal hypodermis rich in mucinous material. The population of telocytes is relatively sparse compared with the fibroblastic population of the entire nail mesenchyme. The concept of onychodermis/onychofibroblasts is not valid. Nail telocytes have a dynamic immunohistochemical profile depending on whether they are located proximally or distally. The CD34 + /CD10 + profile correlates with the onychogenic epithelial region, while the CD34 - /CD10 + profile correlates with a spatial rearrangement of the nail epidermal bed.
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Affiliation(s)
- Christophe Perrin
- Laboratoire Central d'Anatomie Pathologique, University Hospital of Nice, Nice, France
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4
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Castilla-Ibeas A, Zdral S, Galán L, Haro E, Allou L, Campa VM, Icardo JM, Mundlos S, Oberg KC, Ros MA. Failure of digit tip regeneration in the absence of Lmx1b suggests Lmx1b functions disparate from dorsoventral polarity. Cell Rep 2023; 42:111975. [PMID: 36641754 DOI: 10.1016/j.celrep.2022.111975] [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: 05/04/2022] [Revised: 11/07/2022] [Accepted: 12/22/2022] [Indexed: 01/15/2023] Open
Abstract
Mammalian digit tip regeneration is linked to the presence of nail tissue, but a nail-explicit model is missing. Here, we report that nail-less double-ventral digits of ΔLARM1/2 mutants that lack limb-specific Lmx1b enhancers fail to regenerate. To separate the nail's effect from the lack of dorsoventral (DV) polarity, we also interrogate double-dorsal double-nail digits and show that they regenerate. Thus, DV polarity is not a prerequisite for regeneration, and the nail requirement is supported. Transcriptomic comparison between wild-type and non-regenerative ΔLARM1/2 mutant blastemas reveals differential upregulation of vascularization and connective tissue functional signatures in wild type versus upregulation of inflammation in the mutant. These results, together with the finding of Lmx1b expression in the postnatal dorsal dermis underneath the nail and uniformly in the regenerative blastema, open the possibility of additional Lmx1b roles in digit tip regeneration, in addition to the indirect effect of mediating the formation of the nail.
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Affiliation(s)
- Alejandro Castilla-Ibeas
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Sofía Zdral
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Laura Galán
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Endika Haro
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Lila Allou
- RG Development & Disease, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Víctor M Campa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Jose M Icardo
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria, Santander, Spain
| | - Stefan Mundlos
- RG Development & Disease, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Kerby C Oberg
- Department of Pathology and Human Anatomy, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Marian A Ros
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain.
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Mahmud N, Eisner C, Purushothaman S, Storer MA, Kaplan DR, Miller FD. Nail-associated mesenchymal cells contribute to and are essential for dorsal digit tip regeneration. Cell Rep 2022; 41:111853. [PMID: 36543145 DOI: 10.1016/j.celrep.2022.111853] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 10/05/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Here, we ask why the nail base is essential for mammalian digit tip regeneration, focusing on the inductive nail mesenchyme. We identify a transcriptional signature for these cells that includes Lmx1b and show that the Lmx1b-expressing nail mesenchyme is essential for blastema formation. We use a combination of Lmx1bCreERT2-based lineage-tracing and single-cell transcriptional analyses to show that the nail mesenchyme contributes cells for two pro-regenerative mechanisms. One group of cells maintains their identity and regenerates the new nail mesenchyme. A second group contributes specifically to the dorsal blastema, loses their nail mesenchyme phenotype, acquires a blastema transcriptional state that is highly similar to blastema cells of other origins, and ultimately contributes to regeneration of the dorsal but not ventral dermis and bone. Thus, the regenerative necessity for an intact nail base is explained, at least in part, by a requirement for the inductive nail mesenchyme.
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Affiliation(s)
- Neemat Mahmud
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5G 1A8, Canada
| | - Christine Eisner
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada; Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Sruthi Purushothaman
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada; Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Mekayla A Storer
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada
| | - David R Kaplan
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z, Canada
| | - Freda D Miller
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, ON M5G 1A8, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z, Canada.
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6
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Lee D, Abudureyimu G, Park JH, Jang KT, Kwon GY, Shim JS. Characterization of the Onychomatricodermis Containing Onychofibroblasts of the Nail Unit : Histology, Immunohistochemistry, and Electron Microscopic Study. Ann Dermatol 2021; 33:108-115. [PMID: 33935451 PMCID: PMC8082007 DOI: 10.5021/ad.2021.33.2.108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/14/2020] [Accepted: 06/18/2020] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND We recently discovered the presence of specialized nail mesenchyme below the nail matrix and designated it as onychomatricodermis. OBJECTIVE We did further research to characterize the histologic, histochemical, immunohistochemical and ultrastructural features of the onychomatricodermis containing onychofibroblasts in the nail unit. METHODS Ten polydactyly nail unit specimens and 8 nail matrix biopsies were included. H&E-stained slides were reviewed. We did Alcian blue staining and Masson Trichrome staining, as well as immunohistochemical staining for type I collagen, CD10, CD13 and CD34. In addition, polydactyly nail units were examined by transmission electron microscopy. RESULTS In H&E staining, the specialized mesenchyme called onychomatricodermis was observed to be slightly distant from the undersurface of the nail matrix and be less eosinophilic area. Onychomatricodermal onychofibroblasts showed light purple abundant cytoplasm. Masson Trichrome staining revealed fewer collagen fibers within the onychomatricodermis. In Alcian blue staining the onychomatricodermis showed mucin deposition within the onychofibroblasts and around them. Immunohistochemically, type I collagen was expressed much less in the onychomatricodermis while it was strongly expressed elsewhere in the nail unit. In nail matrix biopsy specimens onychomatricodermal onychofibroblasts expressed CD10 and CD13 strongly, and expressed CD34 as well. Ultrastructurally, collagen fibrils were found sparsely within the onychomatricodermis, whereas collagen fibrils were densely distributed in the dermis of other parts of the nail unit. CONCLUSION We demonstrated that there was less collagen expression in the onychomatricodermis containing onychofibroblasts. In addition, we found morphological and immunohistochemical features of onychomatricodermal onychofibroblasts (onychofibroblasts of Dongyoun). These findings support the presence of onychomatricodermis containing onychofibroblasts in the nail unit.
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Affiliation(s)
- Dongyoun Lee
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Gulimila Abudureyimu
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ji-Hye Park
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kee-Taek Jang
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ghee Young Kwon
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jong Sup Shim
- Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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7
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Affiliation(s)
- Eckart Haneke
- Department of Dermatology, Inselspital, University Bern, Bern, Switzerland.,Dermatology Practice Dermaticum, Freiburg, Germany.,Centro Dermatologia Epidermis, Instituto CUF, Porto, Portugal.,Department of Dermatology, University Hospital, Gent, Belgium
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8
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Park JH, Lee DY, Ha SY, Jang KT, Kwon GY, Lee KH, Shim JS. The Concept of Onychodermis (Specialized Nail Mesenchyme) Is Applicable in Normal Adult Nail Unit. Ann Dermatol 2017; 29:234-236. [PMID: 28392657 PMCID: PMC5383755 DOI: 10.5021/ad.2017.29.2.234] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/30/2016] [Accepted: 04/06/2016] [Indexed: 11/17/2022] Open
Affiliation(s)
- Ji-Hye Park
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Dong-Youn Lee
- Department of Dermatology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Sang-Yun Ha
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kee-Taek Jang
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ghee Young Kwon
- Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kyung-Hoon Lee
- Department of Anatomy, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jong Sup Shim
- Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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9
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Gerhards NM, Sayar BS, Origgi FC, Galichet A, Müller EJ, Welle MM, Wiener DJ. Stem Cell-Associated Marker Expression in Canine Hair Follicles. J Histochem Cytochem 2016; 64:190-204. [PMID: 26739040 DOI: 10.1369/0022155415627679] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 12/28/2015] [Indexed: 01/01/2023] Open
Abstract
Functional hair follicle (HF) stem cells (SCs) are crucial to maintain the constant recurring growth of hair. In mice and humans, SC subpopulations with different biomarker expression profiles have been identified in discrete anatomic compartments of the HF. The rare studies investigating canine HF SCs have shown similarities in biomarker expression profiles to that of mouse and human SCs. The aim of our study was to broaden the current repertoire of SC-associated markers and their expression patterns in the dog. We combined analyses on the expression levels of CD34, K15, Sox9, CD200, Nestin, LGR5 and LGR6 in canine skin using RT-qPCR, the corresponding proteins in dog skin lysates, and their expression patterns in canine HFs using immunohistochemistry. Using validated antibodies, we were able to define the location of CD34, Sox9, Keratin15, LGR5 and Nestin in canine HFs and confirm that all tested biomarkers are expressed in canine skin. Our results show similarities between the expression profile of canine, human and mouse HF SC markers. This repertoire of biomarkers will allow us to conduct functional studies and investigate alterations in the canine SC compartment of different diseases, like alopecia or skin cancer with the possibility to extend relevant findings to human patients.
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Affiliation(s)
- Nora M Gerhards
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW)
| | - Beyza S Sayar
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW),Molecular Dermatology and Stem Cell Research, Institute of Animal Pathology and DermFocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (BSS, AG, EJM)
| | - Francesco C Origgi
- Center for Fish and Wildlife Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland (FCO)
| | - Arnaud Galichet
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW),Molecular Dermatology and Stem Cell Research, Institute of Animal Pathology and DermFocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (BSS, AG, EJM)
| | - Eliane J Müller
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW),Molecular Dermatology and Stem Cell Research, Institute of Animal Pathology and DermFocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (BSS, AG, EJM),Department of Dermatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland (EJM)
| | - Monika M Welle
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW)
| | - Dominique J Wiener
- Institute of Animal Pathology, Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland (NMG, BSS, AG, EJM, MMW, DJW)
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10
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Lgr6 marks nail stem cells and is required for digit tip regeneration. Proc Natl Acad Sci U S A 2015; 112:13249-54. [PMID: 26460010 DOI: 10.1073/pnas.1518874112] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The tips of the digits of some mammals, including human infants and mice, are capable of complete regeneration after injury. This process is reliant on the presence of the overlaying nail organ and is mediated by a proliferative blastema. Epithelial Wnt/β-catenin signaling has been shown to be necessary for mouse digit tip regeneration. Here, we report on Lgr5 and Lgr6 (leucine-rich repeat-containing G protein-coupled receptor 5 and 6), two important agonists of the Wnt pathway that are known to be markers of several epithelial stem cell populations. We find that Lgr5 is expressed in a dermal population of cells adjacent to the specialized epithelia surrounding the keratinized nail plate. Moreover, Lgr5-expressing cells contribute to this dermis, but not the blastema, during digit tip regeneration. In contrast, we find that Lgr6 is expressed within cells of the nail matrix portion of the nail epithelium, as well as in a subset of cells in the bone and eccrine sweat glands. Genetic lineage analysis reveals that Lgr6-expressing cells give rise to the nail during homeostatic growth, demonstrating that Lgr6 is a marker of nail stem cells. Moreover, Lgr6-expressing cells contribute to the blastema, suggesting a potential direct role for Lgr6-expressing cells during digit tip regeneration. This role is confirmed by analysis of Lgr6-deficient mice, which have both a nail and bone regeneration defect.
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11
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Exploring the biology of the nail: An intriguing but less-investigated skin appendage. J Dermatol Sci 2015; 79:187-93. [PMID: 25999148 DOI: 10.1016/j.jdermsci.2015.04.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/25/2015] [Accepted: 04/28/2015] [Indexed: 02/04/2023]
Abstract
The nail is a highly keratinized structure covering the tip of the digit, and considered to have several important functions in our daily life. In recent years, as biological aspects of the nail organ have been characterized, we realize that the nail unit and the hair follicle share various biological and immunological features. In particular, development and homeostasis of the nail unit also requires intimate epithelial-mesenchymal interactions that involve signaling pathways such as Wnt. There is also a striking immunological resemblance between both appendages, since the nail matrix, like the anagen hair bulb and the bulge, was shown to present unique characteristics of an immune privileged site. On the other hand, considerable progress in identifying nail stem cells has succeeded in locating putative stem cell niches in the nail unit. In this context, it is intriguing that nail stem cells residing in the nail matrix were recently shown to possess the ability to organize the process leading to digit regeneration. Further elucidation of signaling pathways governing epithelial-mesenchymal interactions in the nail unit seems to be a key to develop a novel therapeutic tool to treat amputees using nail epithelium. However, it is at least certain that the nail unit has a promising potential for the future of regenerative medicine. This review explores the biology of the nail organ by focusing on intriguing knowledge gained from recent studies.
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12
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Perrin C. The nail dermis: from microanatomy to constitutive modelling. Histopathology 2015; 66:864-72. [PMID: 25387989 DOI: 10.1111/his.12608] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/05/2014] [Indexed: 12/01/2022]
Abstract
AIMS The nail mesenchyme, as ligamentous connective tissue, is classically described as a single compartment. Some authors have even suggested the concept of the nail as a musculoskeletal appendage. Recent studies conducted on supernumerary digits surgically removed for polydactyly or on the developing nail organ have introduced into the literature a new concept: the onychodermis and its onychofibroblasts that are CD10-positive/CD34-negative. The aim of this study was to explore the nail mesenchyme more comprehensively. METHODS AND RESULTS A series of 10 normal adult nail units were examined with a combination of morphological and immunohistochemical analysis. This study demonstrates that the nail mesenchyme has two distinct compartments, with a complex microanatomy of matrical dermis and its hypoderm. The matrical dermis is a relatively independent substructure, and comprises two parts: a thin papillary dermis, and a relatively thick reticular dermis. The matrical hypoderm corresponds to a cushion-like layer of adipose tissue, which distally intermingles with an area of loose connective tissue. The nail bed dermis comprises a single, relatively homogeneous compartment. CONCLUSION The matrical nail mesenchyme is a modified dermis. The concept of onychodermis is not applicable in the normal adult nail. Underrecognized non-pathological structures may pose diagnostic problems. The chameleon matrical hypoderm is one such structure.
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Affiliation(s)
- Christophe Perrin
- Laboratoire Central d'Anatomie Pathologique, Hôpital L. Pasteur, University of Nice, Nice, France
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