Mouse Epidermis Research Articles

Thy1 marks a distinct population of slow-cycling stem cells in the mouse epidermis

The presence of distinct stem cells that maintain the interfollicular epidermis is highly debated. Here, we report a population of keratinocytes, marked by Thy1, in the basal layer of the interfollicular epidermis. We find that epidermal cells expressing differential levels of Thy1 display distinct transcriptional signatures. Thy1+ keratinocytes do not express T cell markers, express a unique transcriptional profile, cycle significantly slower than basal epidermal progenitors and display significant expansion potential in vitro. Multicolor lineage tracing analyses and mathematical modeling reveal that Thy1+ basal keratinocytes do not compete neutrally alike interfollicular progenitors and contribute long-term to both epidermal replenishment and wound repair. Importantly, ablation of Thy1+ cells strongly impairs these processes, thus indicating the non-redundant function of Thy1+ stem cells in the epidermis. Collectively, these results reveal a distinct stem cell population that plays a critical role in epidermal homeostasis and repair.

712 UV-induced reduction in polycomb repression promotes epidermal pigmentation

Ultraviolet (UV) radiation is a prime environmental stressor that our epidermis is exposed to on a daily basis. To avert UV-induced damage, epidermal stem cells (EpSCs) become pigmented via a process of heterotypic interaction between melanocytes and EpSCs, however the molecular mechanisms of this interaction are not well understood. In this study we show that the function of a key chromatin regulator, the Polycomb complex, was reduced upon UV exposure in human and mouse epidermis. Genetic ablation of key Polycomb subunits in murine EpSCs, mimicking depletion upon UV exposure, results in an increased number of epidermal melanocytes and subsequent epidermal pigmentation.

620 Inflammasome activation in human keratinocytes and mouse epidermis by ultraviolet radiation

Ultraviolet B radiation (UVB) is a ubiquitous environmental toxin that causes extensive skin damage resulting in inflammation, photoaging and cancer. UVB is known to induce inflammasome activation and a sterile inflammation associated with cytokine release (e.g. IL-1β, IL-18) and immune cell infiltration. We developed circularly permutated luciferase reporters for caspase-1 activation to assess inflammasome activation by UVB in vitro and in vivo. HaCaT keratinocytes transduced with caspase-1 reporters encoding either the caspase-7 or Gasdermin D cleavage sequence became active after exposure to UVB, with maximum caspase-1 activation 9 hours post-UVB with 15 mJ/cm2.

035 Blocking IL-7, but not TLR7, signaling prevents the development of lupus-like autoimmunity in mice

Systemic lupus erythematosus (SLE) is a female-biased multisystem inflammatory disease with substantial morbidity and mortality and limited treatment options. Our lab previously found that VGLL3, a putative transcription co-factor with increased activity in female cells, can drive lupus-like systemic inflammation when overexpressed in mouse epidermis under the K5 promoter. IL-7 signaling was found to be elevated in the skin of lupus patients and K5-Vgll3+ mice alike. Our current results demonstrate that deleting peripheral Il7r in these mice prevents the development of disease phenotype, with amelioration of dermatitis, splenomegaly, lymphadenopathy, and kidney damage.

398 Comparison of epidermal gene expression profiles in mice aged 1 to 20 months

Although it is well known that epidermal function changes with aging, the transcriptomic basis and possible signaling pathways for aging-associated functional changes remain largely unknown. Here we employed RNA sequencing technique to assess epidermal gene expression profiles in the epidermis of mice aged 1, 2, 6, 12 and 20 months old. Our results showed that a total of 132 genes displayed reductions in expression levels with aging while expression levels of 406 genes increased with aging. Epidermal gene expression was prominently upregulated in 2 months vs.

Methods to Identify Immune Cells in Tissues With a Focus on Skin as a Model.

The skin protects our body from external challenges, insults, and pathogens and consists of two layers, epidermis and dermis. The immune cells of the skin are an integral part of protecting the body and essential for mediating skin immune homeostasis. They are distributed in the epidermal and dermal layers of the skin. Under homeostatic conditions, the mouse and human skin epidermis harbors immune cells such as Langerhans cells and CD8+ T cells, whereas the dermis contains dendritic cells (DCs), mast cells, macrophages, T cells, and neutrophils. Skin immune homeostasis is maintained through communication between epidermal and dermal cells and soluble factors. This communication is important for proper recruitment of immune cells in the skin to mount immune responses during infection/injury or in response to external/internal insults that alter the local cellular milieu. Imbalance in this crosstalk that occurs in association with inflammatory skin disorders such as psoriasis and atopic dermatitis can lead to alterations in the number and type of immune cells contributing to pathological manifestation in these disorders. Profiling changes in the immune cell type, localization, and number can provide important information about disease mechanisms and help design interventional therapeutic strategies. Toward this end, skin cells can be detected and characterized using basic techniques like immunofluorescence, immunohistochemistry, and flow cytometry, and recently developed methods of multiplexing. This article provides an overview on the basic techniques that are widely accessible to researchers to characterize immune cells of the skin. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC.

110. A Multi-Species Approach to Limb Regeneration, From Fins to Feet

Purpose: The study of limb and appendage regeneration, which is prevalent in various forms in the animal kingdom, may inform novel strategies for wound healing and regenerative medicine. The first critical step in appendage regeneration is re-epithelialization to form a specialized epidermis, known as the regeneration epidermis, which functions as a signaling center to induce reformation of the structure from underlying mesenchyme in the amputation stump. Despite its universal necessity in appendage regeneration among different species, widely conserved factors defining the regeneration epidermis have not been identified. Methods: Zebrafish caudal fin and mouse digit were used as models for appendage regeneration. The regeneration epidermis of zebrafish caudal fin was profiled with single-cell RNA sequencing. Immunofluorescence and in situ hybridization were used to characterize gene expression. Zebrafish null mutants were generated with the CRISPR/Cas-9 system. Epidermal-specific, inducible deletion mouse mutants were produced by crossing mice expressing CreER driven by the Krt14 promoter to others harboring floxed alleles of the target genes. Discarded leg segments from staged human amputations were obtained to assay for Sp expression. Results: Single-cell RNA sequencing in regenerating zebrafish fin revealed an enriched cell cluster marked by the Sp transcription factor family. Immunofluorescence and in situ hybridization confirmed the expression of Sp family members in the basal epidermis of regenerating caudal fin as well as regenerating mouse digits. CRISPR/Cas-9 was used to generate null mutants in zebrafish for several Sp genes, which demonstrate a variety of skeletal defects. Mice deficient for Sp genes exhibit distal limb defects, while induced deletion of in the basal epidermis of adult mice before digit amputation display impaired bone outgrowth, suggesting a critical role in this process. Intriguingly, we also detected Sp transcripts in the wound epidermis of human leg amputations. Upcoming work will identify transcriptional targets of Sp genes in regenerating mouse digits and human leg amputation wounds with CUT&RUN sequencing. Conclusion: Sp transcription factors may represent conserved genes that participate in appendage regeneration across various species. Future work will define the role of these factors in regeneration-linked gene expression, as well as explore the idea that their expression may be remnants of an incomplete limb regeneration program in humans.

Tideglusib promotes wound healing in aged skin by activating PI3K/Akt pathway

BackgroundAging disturbs the skin morphology and function, manifested as thinned epithelium and impaired wound healing. As a major type of skin cells, epidermal stem cells (EpiSCs) are inevitably affected by aging. The effect of age on EpiSCs and wound healing needs to be further explored.MethodsSkin RNA-seq data of young (5 months) and old (30 months) CB6F1 mice were obtained from GEO Series GSE35322 with 10 in each age group. Differentially expressed genes were analyzed, and EpiSCs-related pathways were enriched by KEGG. The age-related changes of the screened PI3K/Akt pathway were validated by Western Blot and immunofluorescence of epidermis of SD rats (2, 17, and 23 months, n = 6). The expression of upstream protein EGFR was assessed by immunofluorescence in skin of mice (4, 13, and 23 months, n = 6) and human (respectively, 23, 28, 30 years old in the young group and 69, 73, 78 years old in the old group) skin. Inhibitors of EGFR were used to verify its effects on EpiSCs and wound healing. The small molecule drug Tideglusib was tested for its effects on signaling pathways of EpiSCs and wound healing of aged rats. Western Blot was used for the detection of signaling pathways in in vitro experiments. Cell migration assays were used to assess cell migration ability. Flow cytometry was used to detect changes in cell cycle and apoptosis levels. Sulforhodamine B assay and CCK-8 assay were used to evaluate cell proliferation and viability, respectively. Student’s t test and one-way analysis of variance (ANOVA) followed by the multiple comparisons Bonferroni test were used for statistical analysis. The 0.05 level of confidence was accepted as a significant difference.ResultsEpiSCs-related PI3K/Akt pathway was enriched by KEGG and verified by decreased phosphorylation of Akt (32.1 ± 13.8%, P < 0.01) and mTOR (38.9 ± 11.8%, P < 0.01) in aged epidermis of rats. Furthermore, the expression of PI3K/Akt-upstream EGFR decreased with age in the epidermis of mouse (27.6 ± 5.5%, P < 0.01) and human (25.8 ± 9.3%, P < 0.01). With EGFR blocked by Erlotinib, EpiSCs showed reduced phosphorylation of Akt (30.4 ± 10.6%, P < 0.01) and mTOR (39.8 ± 12.8%, P < 0.01), impaired proliferation and migration after incubated for 24 h and 36 h (P < 0.05), and higher levels of apoptosis (11.9 ± 1.7%, P < 0.05), and rats showed slower wound healing from d7 to d14 after wounding (P < 0.01). In addition to slower wound healing rates, aged rats also showed a decrease in the efficacy of EGF, partly due to the downregulated EGFR expression. By activating PI3K/Akt pathway, Tideglusib promoted the proliferation and migration of EpiSCs with apoptosis inhibited (P < 0.01) and accelerated wound healing in aged rats from d7 to d14 after wounding (P < 0.05). Notably, the combined use of Tideglusib and EGF could further enhance wound healing in aged rats.ConclusionsThe decreased expression of EGFR in epidermis with age resulted in decreased activity of the PI3K/Akt pathway and limited EGF efficacy. Tideglusib could assist wound healing in aged rats via activating PI3K/Akt pathway, which may be considered as an ingredient for medical and cosmetics use.

Topical VX-509 attenuates psoriatic inflammation through the STAT3/FABP5 pathway in keratinocytes

BackgroundPsoriasis is a chronic inflammatory disease, with lesions mainly manifesting as scaly erythematous plaques. The mild or moderate of psoriasis is the main type of patients in hospital, and topical application remains the preferred treatment option for psoriasis therapy, therefore, the development of novel topical agents has an essential role in psoriasis therapy. ObjectiveTo identify potential drugs for psoriasis topical treatment. MethodsWe performed drug screening by Imiquimod (IMQ)-induced psoriatic like inflammation in mouse model, followed mouse epidermis by RNA-seq to find the key molecules affecting the drug. The qRT-PCR, WB were performed to test mRNA and protein expression, and Chip assay had been conducted to examine Stat3 bound to promoter of FABP5. ResultsIn this study, we identified VX-509, which topical application significantly attenuated IMQ-induced psoriatic like inflammation in mouse model. And then, we verified Epidermal Fatty acid binding protein (E-FABP/FABP5) was significantly decreased in VX-509 treated mouse epidermis by RNA-seq. FABP5 is a key molecule in lipid metabolism, administration of FABP5 inhibitor or knock down of FABP5 expression remarkably abrogated psoriatic inflammation as well as lipid metabolism. Mechanistically, our finding showed that VX-509 blocked IL-22 induced signaling pathway, particular in activation of Stat3. Furthermore, we identified Stat3 is a transcriptional factor associated with FABP5 promoters and VX-509 treatment remarkably attenuated IL-22-induced FABP5 expression through Stat3 in KCs. ConclusionsThis study demonstrated administration of VX-509 is a potential promising topical drug for treatment of psoriasis, FABP5 is a critical targeted molecule in psoriasis therapy.

UVB irradiation differential regulate miRNAs expression in skin photoaging

BackgroundUVB irradiation can cause acute damage such as sunburn, or photoaging and melanoma, all of which are major health threats. ObjectiveThis study was designed to investigate the mechanism of skin photoaging induced by UVB radiation in mice through the analysis of the differential expression of miRNAs. MethodsA UVB irradiation photoaging model was constructed. HE and Masson special stains were used to examine the modifications in the epidermis and dermis of mice. The miRNA expression profiles of the mouse skin model exposed to UVB radiation and the normal skin of mice were analyzed using miRNA-sequence analysis. GO and Pathway analysis were employed for the prediction of miRNA targets. ResultsA total of 23 miRNAs were evaluated for significantly different expressions in comparison to normal skin. Among them, 7 miRNAs were up-regulated and 16 were down-regulated in the skin with photoaging of mice exposed to UVB irradiation. The differential expression of miRNA is related to a variety of signal transduction pathways, among which mmu-miR-195a-5p and mitogen-activated protein kinase (MAPK) signal pathways are crucial. There was a significant differential expression of miRNA in the skin of normal mice in comparison with the skin with photoaging induced by UVB irradiation. Study limitationsDue to time and energy constraints, the specific protein level verification, MAPK pathway exploration, and miR-195a-5p downstream molecular mechanism need to be further studied in the future. ConclusionsUVB-induced skin photoaging can be diagnosed and treated using miRNA.

Effect of ultraviolet C emitted from KrCl excimer lamp with or without bandpass filter to mouse epidermis

It has been reported that 222-nm ultraviolet C (UVC) exerts a germicidal effect on bacteria and viruses as well as UV radiation emitted from a conventional germicidal lamp but is less toxic to the mammalian cells than that from a germicidal lamp. An excimer lamp filled with krypton chloride (KrCl) gas principally emits 222-nm UVC. However, the lamp also emits a wide band of wavelengths other than 222 nm, especially UVC at a longer wavelength than 222 nm and ultraviolet B, which cause DNA damage. There are some reports on the critical role of bandpass filters in reducing the harmful effect of UVC emitted from a KrCl excimer lamp in a human skin model and human subjects. However, the effectiveness of a bandpass filter has not been demonstrated in animal experiments. In the present study, mice were irradiated with UVC emitted from a KrCl excimer lamp with or without a bandpass filter. UVC emitted from an unfiltered KrCl lamp at doses of 50, 150 and 300 mJ/cm2 induced cyclobutyl pyrimidine dimer (CPD)-positive cells, whereas UVC emitted from a filtered lamp did not significantly increase CPD-positive cells in the epidermis. The present study suggested that the bandpass filter serves a critical role in reducing the harmful effect of emission outside of 222 nm to mouse keratinocytes.

Snail mucin is a functional food ingredient for skin

• Exposure to UVB is a primary reason for skin aging, including wrinkle formation, skin dryness, and loss of elasticity. • Administration of snail mucin displayed anti-wrinkle activity by suppressing MMP-1/-13 expression with collagen restoration in mouse dorsal skin. • Skin hydration activity of snail mucin intake was confirmed by preventing water loss. • UVB-reduced skin elasticity was increased by oral administration of snail mucin in a dose-dependent manner. Recently, the interests about functional ingredients for skin has been increased. Snail mucin has been used to as cosmetic constituent for skin though, the potential of snail mucin for nutricosmetic ingredient has not been fully evaluated. Mucin is a biosynthesized macromolecule which can protect the external damage. The present study investigated the photoprotective effect of the snail mucin against ultraviolet B (UVB)-induced skin photoaging in an animal model. SKH-1 hairless male mice were fed with snail mucin or vehicle for 14 weeks with UVB exposure. Evaluation for the skin damage was analyzed skin replicas, epidermal thickness and collagen fiber integrity, and the moisture contents in the dermal tissue. As well as we studied the effect of snail mucin on the expression of matrix metalloproteinase (MMP)-1/13, hyaluronic acid synthase (HAS) and hyaluronidase (HYAL). The safety of intake of snail mucin is also evaluated in the liver, spleen, and liver damage enzyme level. The results showed that the depth of the wrinkles, relative moisture content, relative elasticity induced by UVB irradiation on the epidermis of mice were obviously improved by supplementation of snail mucin. Furthermore, snail mucin intake did not cause liver size change, body weight change, spleen enlargement, and liver damage enzyme. Taken together, oral administration of snail mucin improved UVB-induced photoaging properties such as wrinkle depth, moisture loss, and loss of elasticity on the skin with no toxicity. Therefore, we suggest potential of ingredient of nutricosmetics.

STING activation promotes inflammatory response and delays skin wound healing in diabetic mice

Sustained inflammatory responses delay wound repair in diabetic skin. The stimulator of interferon genes (STING) plays a vital role in the innate immune responses. However, its function in diabetic skin wound repair, and the underlying mechanism remains unclear. Here, we reported that STING activation is a pathogenic marker that correlates with delayed wound repair in diabetic skin. Firstly, we found that STING expression is enhanced in the epidermis of STZ induced diabetes mouse model and db/db mouse model. Consistently, we also found that STING expression was upregulated in keratinocytes with the high-glucose (HG) treatment. Moreover, silencing of STING accelerated wound healing in vitro. In vivo, inhibition of STING by c176 inhibited inflammatory response in the epidermis and accelerated wound healing in diabetic skin. In addition, we found that autophagy dysfunction is correlated with the expression of STING in epidermis of diabetic mice. Induction of autophagy by rapamycin significantly reduced STING expression in keratinocytes. Collectively, these results indicated that defects of autophagy might lead to the activation of STING and finally delay the diabetic wound healing.

Planar cell polarity protein-dependent basal cell height in the later stage embryonic mouse epidermis impacts on the shape of overlying suprabasal cells.

Background: Complex organ formation requires the coordinated morphogenesis of adjacent tissue layers. Here, a role for the planar cell polarity (PCP) proteins Fz6 and Celsr1 in generating squamous basal cells in the later stage embryonic epidermis of the mouse is reported, which impacts upon the shape of overlying suprabasal cells. Methods: The depth of the epidermis and basal layer as well as cell proliferation index was scored from immunostained wax sections taken from different mouse embryos mutant in planar cell polarity signalling and their wild-type littermates. Orientation of epidermal cell division in Celsr1 Crash/Crash mutants was determined from thick frozen immunostained sections. Immunostained wax sections of wild-type skin explants cultured using the Lumox method enabled any changes in epidermal and basal layer depth to be measured following the release of surface tension upon dissection of skin away from the whole embryo. Results: Increased numbers of columnar and cuboidal basal epidermal cells were observed in fz6 and Celsr1 mouse mutants including Celsr1 Crash/Crash which correlated with more rounded suprabasal cells and a thicker epidermis. Conclusions: Altogether these data support tissue intrinsic roles for PCP proteins in 'outside-in' (radial) skin architecture.

Epidermal 1-O-acylceramides appear with the establishment of the water permeability barrier in mice and are produced by maturating keratinocytes.

1-O-Acylceramides (1-OACs) have a fatty acid esterified to the 1-hydroxyl of the sphingosine head group of the ceramide, and recently we identified these lipids as natural components of human and mouse epidermis. Here we show epidermal 1-OACs arise shortly before birth during the establishment of the water permeability barrier in mice. Fractionation of human epidermis indicates 1-OACs concentrate in the stratum corneum. During in vitro maturation into reconstructed human epidermis, human keratinocytes dramatically increase 1-OAC levels indicating they are one source of epidermal 1-OACs. In search of potential enzymes responsible for 1-OAC synthesis in vivo, we analyzed mutant mice with deficiencies of ceramide synthases (Cers2, Cers3, or Cers4), diacylglycerol acyltransferases (Dgat1 or Dgat2), elongase of very long fatty acids 3 (Elovl3), lecithin cholesterol acyltransferase (Lcat), stearoyl-CoA desaturase 1 (Scd1), or acidic ceramidase (Asah1). Overall levels of 1-OACs did not decrease in any mouse model. In Cers3 and Dgat2-deficient epidermis they even increased in correlation with deficient skin barrier function. Dagt2 deficiency reshapes 1-OAC synthesis with an increase in 1-OACs with N-linked non-hydroxylated fatty acids and a 60% decrease compared to control in levels of 1-OACs with N-linked hydroxylated palmitate. As none of the single enzyme deficiencies we examined resulted in a lack of 1-OACs, we conclude that either there is functional redundancy in forming 1-OAC and more than one enzyme is involved, and/or an unknown acyltransferase of the epidermis performs the final step of 1-OAC synthesis, the implications of which are discussed.

IL-17A Promotes Psoriasis-Associated Keratinocyte Proliferation through ACT1-Dependent Activation of YAP–AREG Axis

Psoriasis is a recurrent inflammatory skin disorder characterized by epidermal hyperplasia, which is primarily driven by IL-17A. The Hippo-YAP signaling pathway plays a vital role in cell survival and tissue growth, and its target gene, AREG, has been reported to promote the development of psoriasis. However, whether IL-17A promotes keratinocyte proliferation through regulating Hippo-YAP signaling has not been explored. In this study, we show that the YAP-AREG pathway is activated in human psoriatic skin and is suppressed by IL-17A antagonist secukinumab and that imiquimod and IL-17A administration activates the YAP-AREG axis in mice epidermis. Invitro studies using HaCaT and normal human epidermal keratinocyte cells suggest that IL-17A enhances AREG expression and keratinocyte proliferation by activating Hippo-YAP signaling. Mechanistically, IL-17A stimulates the recruitment of MST1 to ACT1 in keratinocytes, which leads to reduced MST1-LATS1 interaction and YAP dephosphorylation. Together, our findings reveal a previously unknown mechanism in which IL-17A promotes keratinocyte proliferation in psoriasis, namely through activating YAP-AREG signaling.

Targeted deletion of TGFβ1 in basal keratinocytes causes profound defects in stratified squamous epithelia and aberrant melanocyte migration

Transforming Growth Factor Beta 1 (TGFβ1) is a multifunctional cytokine that regulates proliferation, apoptosis, and epithelial-mesenchymal transition of epithelial cells. While its role in cancer is well studied, less is known about TGFβ1 and regulation of epithelial development. To address this, we deleted TGFβ1 in basal keratinocytes of stratified squamous epithelia. Newborn mice with a homozygous TGFβ1 deletion had significant defects in proliferation and differentiation of the epidermis and oral mucosa, and died shortly after birth. Hair follicles were sparse in TGFβ1 depleted skin and had delayed development. Additionally, the Wnt pathway transcription factor LEF1 was reduced in hair follicle bulbs and nearly absent from the basal epithelial layer. Hemizygous knockout mice survived to adulthood but were runted and had sparse coats. The skin of these mice had irregular hair follicle morphology and aberrant hair cycle progression, as well as abnormally high melanin expression and delayed melanocyte migration. In contrast to newborn TGFβ1 null mice, the epidermis was hyperproliferative, acanthotic and inflamed. Expression of p63, a master regulator of stratified epithelial identity, proliferation and differentiation, was reduced in TGFβ1 null newborn epidermis but expanded in the postnatal acanthotic epidermis of TGFβ1 hemizygous mice. Thus, TGFβ1 is both essential and haploinsufficient with context dependent roles in stratified squamous epithelial development and homeostasis.

ENKD1 promotes epidermal stratification by regulating spindle orientation in basal keratinocytes.

Stratification of the epidermis is essential for the barrier function of the skin. However, the molecular mechanisms governing epidermal stratification are not fully understood. Herein, we demonstrate that enkurin domain-containing protein 1 (ENKD1) contributes to epidermal stratification by modulating the cell-division orientation of basal keratinocytes. The epidermis of Enkd1 knockout mice is thinner than that of wild-type mice due to reduced generation of suprabasal cells from basal keratinocytes through asymmetric division. Depletion of ENKD1 impairs proper orientation of the mitotic spindle and delays mitotic progression in cultured cells. Mechanistic investigation further reveals that ENKD1 is a novel microtubule-binding protein that promotes the stability of astral microtubules. Introduction of the microtubule-binding domain of ENKD1 can largely rescue the spindle orientation defects in ENKD1-depleted cells. These findings establish ENKD1 as a critical regulator of astral microtubule stability and spindle orientation that stimulates epidermal stratification in mammalian cells.

Vγ5Vδ1 TCR signaling is required to different extents for embryonic versus postnatal development of DETCs.

γδ T cells expressing Vγ5Vδ1 TCR originally develop in the embryonic thymus and migrate to the epidermis, forming dendritic epidermal T cells (DETCs) throughout life. It is thought that a TCR signal is essential for their development; e.g., lack of TCR signal-transducer ZAP70 significantly decreases DETC numbers. On the other hand, lack of ZAP70 does not affect Vγ5Vδ1+ T cells in the embryonic thymus; thus, the involvement of TCR signaling remains elusive. Here, we used SKG mice with attenuated TCR signaling rather than gene-knockout mice. In SKG mice, Vγ5+ T cells showed a marked decrease [10% of wild-type (WT)] in adult epidermis; however, there was just a moderate decrease (50% of WT) in the embryonic thymus. In early postnatal epidermis in SKG mice, substantial numbers of Vγ5+ T cells were observed (50% of WT). Their activation markers including CD122, a component of the IL-15 receptor indispensable for DETC proliferation, were comparable to those of WT. However, the Vγ5+ T cells in SKG mice did not proliferate and form DETCs thereafter. Furthermore, in SKG/+ mice, the number of thymic Vγ5Vδ1+ T cells increased, compared to SKG mice; however, the number of DETCs remained significantly lower than in WT, similar to SKG mice. Our results suggest that signaling via Vγ5Vδ1 TCR is indispensable for DETC development, with distinct contributions to embryonic development and postnatal proliferation.

Comparison of Epidermal Gene Expression Profiles in Mice Aged 1 to 20 Months.

IntroductionAlthough it is well known that epidermal function changes with aging, the transcriptomic basis and possible signaling pathways for aging-associated functional changes remain largely unknown.MethodsHere, we employed RNA sequencing techniques to assess epidermal gene expression profiles in the epidermis of mice aged 1, 2, 6, 12 and 20 months.ResultsA total of 132 genes displayed reductions in expression levels with aging, while expression levels of 406 genes increased with aging. Epidermal gene expression was prominently upregulated in 2-month-old vs 1-month-old mice, while more genes were downregulated in 12-month-old mice. Upregulation of genes associated with immune/inflammatory responses was observed in the epidermis of aged mice in comparison to that of young mice, whereas downregulated signaling pathways in the epidermis of aged mice were primarily involved in metabolism, such as fatty acid elongation, glutathione metabolism and biosynthesis of antibiotics. Some signaling pathways, such as chemokine signaling, cytokine/cytokine receptor interaction signaling and IL-17 signaling pathways, were remarkably upregulated in 12-month-old mice. Steroid synthesis, metabolic pathway, thermogenesis and proteasome pathways were steadily downregulated, starting at 2 months old.ConclusionThese results indicate that the epidermis of aged mice displays an upregulation of genes associated with inflammatory signaling pathways, and downregulation of genes related to metabolic signaling pathways.