Cells In Interfollicular Epidermis Research Articles

Calcitonin gene-related peptide receptor Calcrl is enriched in hair follicles stem cells and differentially expressed in interfollicular epidermis in murine skin.

Calcitonin gene-related peptide (CGRP) and adrenomedullin are structurally similar neuropeptides acting as potent vasodilators of blood pressure and mediator of inflammation in skin. Revealing the expression pattern of their common receptor-Calcitonin gene-related peptide receptor (Calcrl) in their targeted cells is important to explain the functions of CGRP and adrenomedullin in skin. Our immunostaining results showed that Calcrl is enriched in hair follicles bulge stem cells and differentially expressed in basal stem cells of interfollicular epidermis. In addition, Calcrl expression in interfollicular epidermis is dependent on presence of nerve fibers. Long-term ablation of the murine cutaneous nerve leads to loss of Calcrl expression in interfollicular epidermis but not in hair follicle bulge stem cells. Our results demonstrate a tight interaction between neuronal components and epidermis, and indicates potential roles of Calcrl in epidermal stem cells.

Ultraviolet radiation induces Melan-A-expressing cells in interfollicular epidermis in wild-type mice.

Adult wild-type mice are not supposed to be proper models for ultraviolet radiation (UVR)-induced melanoma since melanocytes are confined to hair follicles and cannot be sufficiently reached by UVR. On the other hand, in mutated mouse models used for melanoma research limitations, including an altered immune system and selection of affected pathways, lead to tumors phenotypically quite different from naturally occurring melanomas. We compared the distribution of epidermal melanocytes in UVR and not-UVR-exposed wild-type C57BL/6 mice. Starting at the age of 8weeks, mice were exposed to physiologic doses of UVR three times weekly over 16weeks. Back skin biopsies were taken 4, 8, 12 and 16 weeks after initiation of exposure, and stained for Melan-A, representing a highly selective marker for melanocytes. Surprisingly, after exposure to UVR, Melan-A positive cells were detected also in the interfollicular epidermis of C57BL/6 mice. We conclude that UVR is capable of inducing interfollicular epidermal melanocytes in wild-type mice.

Glutamate transporter Slc1a3 mediates inter-niche stem cell activation during skin growth.

Tissues contain distinct stem cell niches, but whether cell turnover is coordinated between niches during growth is unknown. Here, we report that in mouse skin, hair growth is accompanied by sebaceous gland and interfollicular epidermis expansion. During hair growth, cells in the bulge and outer root sheath temporarily upregulate the glutamate transporter SLC1A3, and the number of SLC1A3+ basal cells in interfollicular epidermis and sebaceous gland increases. Fate mapping of SLC1A3+ cells in mice revealed transient expression in proliferating stem/progenitor cells in all three niches. Deletion of slc1a3 delays hair follicle anagen entry, uncouples interfollicular epidermis and sebaceous gland expansion from the hair cycle, and leads to reduced fur density in aged mice, indicating a role of SLC1A3 in stem/progenitor cell activation. Modulation of metabotropic glutamate receptor 5 activity mimics the effects of SLC1A3 deletion or inhibition. These data reveal that stem/progenitor cell activation is synchronized over distinct niches during growth and identify SLC1A3 as a general marker and effector of activated epithelial stem/progenitor cells throughout the skin.

The Co-Expression Pattern of p63 and HDAC1: A Potential Way to Disclose Stem Cells in Interfollicular Epidermis.

Stem cell markers of interfollicular epidermis (IEF) have not been established thus far. The aim of this study is to suggest a new way to disclose IFE-stem cells by combining the expression of histone deacetylases (HDAC) 1 and p63. Immunohistochemical staining of HDAC1 and p63 was performed in six normal human samples. Moreover, a skin equivalent (SE) model was treated with suberoylanilohydroxamic acid (SAHA, an HDAC inhibitor) to elucidate the role of HDAC1. Finally, rapidly adhering (RA) keratinocytes to a type IV collagen, which have been identified to represent epidermal stem cells, were subjected to Western blot analysis with antibodies against HDAC1. In normal samples, there was a minor subpopulation comprised of p63-positive and HDAC1-negative cells in the basal layers. The proportion of this subpopulation was decreased with age. In the SE model, SAHA treatment increased the epidermal thickness and number of p63-positive cells in a dose dependent manner. After SAHA treatment, the expression of differentiation markers was decreased, while that of basement membrane markers was increased. In a Western blot analysis, HDAC1 was not expressed in RA cells. In conclusion, the combination of p63-positive and HDAC1-negative expressions can be a potential new way for distinguishing epidermal stem cells.

TLR7-expressing cells comprise an interfollicular epidermal stem cell population in murine epidermis.

Normal interfollicular epidermis (IFE) homeostasis is maintained throughout the entire life by its own stem cells that self-renew and generate progeny that undergo terminal differentiation. However, the fine markers of the stem cells in interfollicular epidermis are not well defined yet. Here we found that TLR7 identified the existence of progenitors and interfollicular epidermal stem cells in murine skin. In vitro, TLR7-expressing cells comprised of two subpopulations that were competent to proliferate and exhibited distinct differentiation potentials. Three-dimensional (3D) organotypic culture and skin reconstitution assays showed that TLR7-expressing cells were able to reconstruct the interfollicular epidermis. Finally, TLR7-expressing cells maintained the intact interfollicular epidermal structures revealed in serial transplantation assays in vivo in mice. Taken together, our results suggest that TLR7-expressing cells comprise an interfollicular epidermal stem cell population.

Immunohistochemical Study of Melanocyte–Melanocyte Stem Cell lineage in Vitiligo; A Clue to Interfollicular Melanocyte Stem Cell Reservoir

ABSTRACTThere has been a long lasting controversy over whether melanocytes (MCs) in vitiligo are actually lost or still present but functionally inactive. We aimed to evaluate the MC cell lineage in follicular and interfollicular vitiliginous epidermis through immunohistochemical localization of Human Melanoma Black-45 (HMB-45) and Tyrosinase Related Protein 2 (TRP2) and to correlate it with clinicopathologic parameters. Using immunohistochemical techniques, skin biopsies from 50 vitiligo patients and 20 age- and gender-matched healthy subjects were examined. Differentiated active MCs were detected in 44% of interfollicular epidermis (IFE) and 46.7% of follicular epidermis (FE) in lesional skin. Melanocyte precursors/stem cells were detected in 54% of IFE and 63.3% of FE in lesional skin. Melanocyte precursors/stem cells of IFE were significantly associated with residual melanin pigment (p = 0.007) and with absence of angiogenesis (p = 0.05). HMB-45 percentage of expression in IFE was positively correlated with MC precursors/stem cells percentage in FE (r = +0.65, p < 0.001) and IFE (r = +0.33, p = 0.01). Melanocyte precursors/stem cells positivity (p < 0.001) was progressively decreasing with advanced histopathologic grading. There was no significant association between interfollicular or follicular expression of HMB-45, TRP2 or MC precursors/stem cells and the clinical type of vitiligo or its duration. In conclusion, functioning MCs may exist in vitiligo. The presence of MC precursors/stem cells in IFE may provide an additional reservoir needed for repigmentation.

1123. Adenovirus-Mediated Expression of Sonic Hedgehog Increases the Number of CD34+ Cells in the Epidermal Stem Cell Niche in Hair Follicles

The hair follicle stem cell niche, also known as the |[ldquo]|bulge,|[rdquo]| contains adult stem cells that give rise to the follicle keratinocytes that generate hair shafts . While epidermal stem cells are utilized cyclically for hair shaft regrowth, epidermal stem cells also contribute progenitor cells of interfollicular epidermis as part of wound repair. Prior work from this laboratory (Sato et al. J Clin Invest 1999; 104:855) showed that exogenous, adenovirus-mediated expression of Sonic hedgehog (Shh) in skin with resting hair follicles (telogen) activated the growth phase of the hair cycle (anagen) leading to the hypothesis that Shh expression would affect the physiology of the cells in the bulge. To test this hypothesis, analysis of the bulge was conducted under normal hair growth conditions and following adenovirus-mediated local delivery of genes to accelerate hair growth. The mouse epidermal stem cell niche was visualized by immunohistochemical staining using anti-CD34+ primary antibodies. In naive mice, the morphology of the stem cell niche was constant throughout the hair follicle cycle (anagen vs telogen) and over a broad range of mouse ages (2 to 24 months). Mouse skin in telogen was examined without treatment (naive) or following intradermal administration of AdNull (control vector) or AdShh, and 2 wk following vector administration, the CD34+ bulge region was evaluated. Naive mouse skin and AdNull-infected mouse skin remained in telogen and did not show evidence of a change in bulge morphology. In contrast, AdShh-treated skin entered anagen and showed increases in CD34+ area per follicle (67 |[plusmn]| 18% increase). In naive and AdNull-treated skin, the area of the CD34+ staining in the bulge did not change as the skin entered anagen, indicating that the increase in the area of CD34+ cells was observed only following AdShh administration. Three-dimensional reconstructions made from serial stained sections of murine skin, showed that the increase in CD34+ area in single sections corresponded with an increase in CD34+ volume per follicle (140 |[plusmn]| 26% increase) as well as the absolute number of CD34+ cells per hair follicle. Similarly, AdShh-treated skin showed an increase in the number of CD34+ cells per follicle bulge (116 |[plusmn]| 33% increase). To determine whether the changes in bulge morphology were specifically related to expression of the Shh transgene, murine skin was treated with an Ad vector expressing the cDNA for Noggin, another secreted protein that initiates the onset of anagen in hair follicles. While AdNoggin, like AdShh, induced early onset of anagen in murine skin, administration of AdNoggin did not result in an increase in CD34+ area, volume, or cell number, indicating that the effect observed using AdShh was a specific property of Shh expression. Taken together, the data suggest that Shh expression modulates the physiology of adult epidermal stem cells in the hair follicle stem cell niche, creating a potential means for therapeutic manipulation of these cells.

Measuring stem cell frequency in epidermis: a quantitative in vivo functional assay for long-term repopulating cells.

Epidermal stem cells play a central role in tissue homeostasis, wound repair, tumor initiation, and gene therapy. A major impediment to the purification and molecular characterization of epidermal stem cells is the lack of a quantitative assay for cells capable of long-term repopulation in vivo, such as exists for hematopoietic cells. The tremendous strides made in the characterization and purification of hematopoietic stem cells have been critically dependent on the availability of competitive transplantation assays, because these assays permit the accurate quantitation of long-term repopulating cells in vivo. We have developed an analogous functional assay for epidermal stem cells, and have measured the frequency of functional epidermal stem cells in interfollicular epidermis. These studies indicate that cells capable of long-term reconstitution of a squamous epithelium reside in the interfollicular epidermis. We find that the frequency of these long-term repopulating cells is 1 in 35,000 total epidermal cells, or in the order of 1 in 104 basal epidermal cells, similar to that of hematopoietic stem cells in the bone marrow, and much lower than previously estimated in epidermis. Furthermore, these studies establish a novel functional assay that can be used to validate immunophenotypic markers and enrichment strategies for epidermal stem cells, and to quantify epidermal stem cells in various keratinocyte populations. Thus further studies using this type of assay for epidermis should aid in the progress of cutaneous stem cell-targeted gene therapy, and in more basic studies of epidermal stem cell regulation and differentiation.

Altered Keratin Expression in Benign and Malignant Skin Diseases Revealed with Monoclonal Antibodies

We studied keratin expression in benign epidermal skin diseases, and in Bowen's disease by using three monoclonal cytokeratin antibodies. In adult normal skin, these antibodies bind only to the follicular epithelium (PKK1), the basal keratinocytes (PKK2), or the suprabasal cells in interfollicular epidermis (KA5). Additionally, in fetal epidermis, the PKK1 antibody reacts with basal keratinocytes. In psoriasis and lichen planus, the PKK2 antibody distinctly revealed all epidermal cell layers by immunostaining. However, a negative basal cell-like layer was revealed in both lesions with the KA5 antibody. In pityriasis rubra pilaris, the basal cell layer was uniformly stained with the PKK2 antibody, but only some keratinocytes in upper cell layers showed fluorescence and, in chronic eczema, the 3-4 lowest epidermal cell layers were reactive. The PKK1 antibody did not stain interfollicular keratinocytes in any of the benign proliferative skin diseases studied. In Bowen's disease, a heterogeneous staining pattern with varying intensity among individual cells was seen with all of the antibodies used. Our results suggest different changes in keratin expression in chronic benign and malignant epidermal diseases that may reflect the mechanisms behind these changes.