HGF/SF increases number of skin melanocytes but does not alter quality or quantity of follicular melanogenesis

Adiponectin negatively regulates pigmentation, Wnt/β-catenin and HGF/c-Met signalling within human scalp hair follicles ex vivo

Adiponectin reportedly stimulates proliferation and elongation of human scalp hair follicles (HFs) ex vivo. In the current study, we investigated how adiponectin oligomers produced by perifollicular dermal white adipose tissue (dWAT), a potent source of adiponectin isoforms, influence human HF proliferation and pigmentation. To do so, we treated microdissected, organ-cultured HFs in the presence or absence of dWAT with a recombinant human adiponectin oligomer mix, or inhibited dWAT-derived adiponectin using a neutralizing antibody. Multiplex qPCR (Fluidigm) revealed that adiponectin oligomers downregulated pigmentation genes KITLG, PMEL and TYRP1 and Wnt genes AXIN2, LEF1 and WNT10B. In situ hybridization showed that adiponectin downregulated AXIN2 and LEF1, and up-regulated DKK1 within the dermal papilla (DP), a highly unusual transcriptional profile for a putative hair growth-promoting agent. Adiponectin oligomers also downregulated protein expression of the HGF receptor c-Met within the matrix and DP. However, adiponectin did not alter hair matrix keratinocyte proliferation within 48 h ex vivo, irrespective of the presence/absence of dWAT; HF pigmentation (Masson-Fontana histochemistry, tyrosinase activity) was also unchanged. In contrast, neutralizing adiponectin isoforms within HF + dWAT increased proliferation, melanin content and tyrosinase activity but resulted in fewer melanocytes and melanocytic dendrites, as assessed by gp100 immunostaining. These seemingly contradictory effects suggest that adiponectin exerts complex effects upon human HF biology, likely in parallel with the pro-pigmentation effects of dWAT- and DP-derived HGF. Our data suggest that dWAT-derived ratios of adiponectin isoforms and the cleaved, globular version of adiponectin may in fact determine how adiponectin impacts upon follicular pigmentation and growth.

Steroidogenic factor-1 lineage origin of skin lesions in Carney complex syndrome

Carney complex (CNC) is a rare familial multi-neoplastic syndrome predisposing to endocrine and non-endocrine tumors due to inactivating mutations of PRKAR1A leading to perturbations of the cAMP protein kinase A (PKA) signaling pathway. Skin lesions are the most common manifestation of CNC, including lentigines, blue nevi and cutaneous myxomas, in unusual locations such as oral and genital mucosa. Unlike endocrine disorders, the pathogenesis of skin lesions remains unexplained. Here, we show that embryonic invalidation of the Prkar1a gene in Steroidogenic Factor-1-expressing cells, leads to the development of familial skin pigmentation alterations reminiscent of those in patients. Immunohistological and molecular analyses coupled with genetic monitoring of recombinant cell lineages in mouse skin, suggest that familial lentiginosis and myxomas occurs in skin areas specifically enriched in dermal melanocytes. In lentigines and blue nevi-prone areas from mutant mice and patients, Prkar1a/PRKAR1A invalidation occurs in a subset of dermal fibroblasts capable of inducing, under the influence of PKA signaling, the production of pro-melanogenic EDN3 and HGF signals. Our model strongly suggests that the origin of the typical CNC cutaneous lesions is the result of non-cell-autonomous pro-melanogenic activity of a dermal fibroblast population sharing a community of origin with SF-1 lineage.

Facial Fat Fitness: A New Paradigm to Understand Facial Aging and Aesthetics

Traditionally, facial adipose tissue has been perceived and treated as a homogenous volume-occupying subcutaneous depot. However, recent research from across disciplines is converging to reveal a far more anatomically organized and functionally dynamic role of facial adipose tissue. In this narrative review, we will discuss new insights into adipocyte function and facial adipose anatomy that have far-reaching implications for the practice of aesthetic facial plastic surgery. These concepts are synthesized into a "facial fat fitness" model which can be used to explain clinical observations in facial aging and aesthetic surgery. Fat fitness relates to the quality of facial adipose tissue, as opposed to quantity, and describes whether adipose tissue is in a predominantly healthy hyperplastic or unhealthy hypertrophic state. Fat fitness is modulated by lifestyle factors, and may be impacted positively or negatively by facial aesthetic treatments. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Dermal Adipose Tissue Secretes HGF to Promote Human Hair Growth and Pigmentation

Hair follicles (HFs) are immersed within dermal white adipose tissue (dWAT), yet human adipocyte‒HF communication remains unexplored. Therefore, we investigated how perifollicular adipocytes affect the physiology of human anagen scalp HFs. Quantitative immunohistomorphometry, X-ray microcomputed tomography, and transmission electron microscopy showed that the number and size of perifollicular adipocytes declined during anagen‒catagen transition, whereas fluorescence-lifetime imaging revealed increased lipid oxidation in adipocytes surrounding the bulge and/or sub-bulge region. Ex vivo, dWAT tendentially promoted hair shaft production, and significantly stimulated hair matrix keratinocyte proliferation and HF pigmentation. Both dWAT pericytes and PREF1/DLK1⁺ adipocyte progenitors secreted HGF during human HF‒dWAT co-culture, for which the c-Met receptor was expressed in the hair matrix and dermal papilla. These effects were reproduced using recombinant HGF and abrogated by an HGF-neutralizing antibody. Laser-capture microdissection‒based microarray analysis of the hair matrix showed that dWAT-derived HGF upregulated keratin (K) genes (K27, K73, K75, K84, K86) and TCHH. Mechanistically, HGF stimulated Wnt/β-catenin activity in the human hair matrix (increased AXIN2, LEF1) by upregulating WNT6 and WNT10B, and inhibiting SFRP1 in the dermal papilla. Our study demonstrates that dWAT regulates human hair growth and pigmentation through HGF secretion, and thus identifies dWAT and HGF as important novel molecular and cellular targets for therapeutic intervention in human hair growth and pigmentation disorders.

Antifibrogenic Activities of CYP11A1-derived Vitamin D3-hydroxyderivatives Are Dependent on RORγ

Previous studies showed that noncalcemic 20(OH)D3, a product of CYP11A1 action on vitamin D3, has antifibrotic activity in human dermal fibroblasts and in a bleomycin mouse model of scleroderma. In this study, we tested the role of retinoic acid-related orphan receptor γ (RORγ), which is expressed in skin, in the action of CYP11A1-derived secosteroids using murine fibroblasts isolated from the skin of wild-type (RORγ +/+), knockout (RORγ -/-), and heterozygote (RORγ +/-) mice. CYP11A1-derived 20(OH)D3, 20,23(OH)2D3, 1,20(OH)2D3, and 1,20,23(OH)3D3 inhibited proliferation of RORγ +/+ fibroblasts in a dose-dependent manner with a similar potency to 1,25(OH)2D3. Surprisingly, this effect was reversed in RORγ +/- and RORγ -/- fibroblasts, with the most pronounced stimulatory effect seen in RORγ -/- fibroblasts. All analogs tested inhibited TGF-β1-induced collagen synthesis in RORγ +/+ fibroblasts and the expression of other fibrosis-related genes. This effect was curtailed or reversed in RORγ -/- fibroblasts. These results show that the antiproliferative and antifibrotic activities of the vitamin D hydroxy derivatives are dependent on a functional RORγ. The dramatic changes in the transcriptomes of fibroblasts of RORγ -/- versus wild-type mice following treatment with 20(OH)D3 or 1,20(OH)2D3 provide a molecular basis to explain, at least in part, the observed phenotypic differences.

Forensic determination of hair deposition time in crime scenes using electron paramagnetic resonance

Several types of biological samples, including hair strands, are found at crime scenes. Apart from the identification of the value and the contributor of the probative evidence, it is important to prove that the time of shedding of hair belonging to a suspect or victim matches the crime window. To this end, to estimate the ex vivo aging of hair, we evaluated time-dependent changes in melanin-derived free radicals in blond, brown, and black hairs by using electron paramagnetic resonance spectroscopy (EPR). Hair strands aged under controlled conditions (humidity 40%, temperature 20-22°C, indirect light, with 12/12 hour of light/darkness cycles) showed a time-dependent decay of melanin-derived radicals. The half-life of eumelanin-derived radicals in hair under our experimental settings was estimated at 22 ± 2 days whereas that of pheomelanin was about 2 days suggesting better stabilization of unpaired electrons by eumelanin. Taken together, this study provides a reference for future forensic studies on determination of degradation of shed hair in a crime scene by following eumelanin radicals by utilizing the non-invasive, non-destructive, and highly specific EPR technique.

Peroxisome proliferator-activated receptor α (PPARα) contributes to control of melanogenesis in B16 F10 melanoma cells

Recent studies revealed the cooperation between peroxisome proliferator-activated receptor gamma (PPARγ) and α-MSH signaling, which results in enhanced melanogenesis in melanocytes and melanoma cells. However, the agonists of PPARα, such as fenofibrate, exert depigmenting effect. Therefore, we aimed to check how the PPARα expression level affects the antimelanogenic activity of fenofibrate and whether PPARα modulates melanogenesis independently of its agonist. To answer these questions, we used three B16 F10-derived cell lines, which varied in the PPARα expression level and were developed by stable transfection with plasmids driving shRNA-based PPARα silencing or overexpression of PPARα-emerald GFP fusion protein. Melanin contents were assessed with electron paramagnetic resonance spectroscopy along with color component image analysis-a novel approach to pigment content characteristics in melanoma cells. B16 F10 wt and Ctrl shRNA lines showed intermediate pigmentation, whereas the pigmentation of the B16 F10-derived cell lines was inversely correlated with the PPARα expression level. We observed that cells overexpressing PPARα were almost amelanotic and cells with reduced PPARα protein level were heavily melanized. Furthermore, fenofibrate down-regulated the melanogenic apparatus (MITF, tyrosinase, and tyrosinase-related proteins) in the cells with the regular PPARα expression level resulting in their visibly lower total melanin content in all the cell lines. From these observations, we conclude that fenofibrate works as a strong depigmenting agent, which acts independently of PPARα, but in an additive fashion. Our results also indicate that alterations in PGC-1a acetylation and expression level might contribute to the regulation of melanogenesis by PPARα and fenofibrate.

Expression and tissue distribution of hepatocyte growth factor (HGF) and its receptor (c-Met) in alpacas (Vicugna pacos) skins associated with white and brown coat colors

Hepatocyte growth factor (HGF)/c-Met signaling has been considered as a key pathway in both melanocyte development and melanogenesis. To understand better the expression patterns and tissue distribution characterization of HGF and its receptor c-Met in skin of white versus brown alpaca (Vicugna pacos), we detected the tissue distribution of HGF and c-Met using immunohistochemistry and analyzed the expression patterns by using Western blot and quantitative real time PCR (qPCR). Immunohistochemistry analysis demonstrated that HGF staining robustly increased in the dermal papilla and mesenchymal cells of white alpaca skin compared with that of brown. However, c-Met staining showed strongly positive result, particularly inhair matrix and root sheath in brown alpaca skin. Western blot and qPCR results suggested that HGF and c-Met were expressed at significantly high levels in white and brown alpaca skins, respectively, and protein and transcripts possessed the same expression pattern in white and brown alpaca skins. The results suggested that HGF/c-Met signaling functions in alpaca coat color formation offer essential theoretical basis for further exploration of the role of HGF/c-Met signaling in pigment formation.

A melanin-independent interaction between Mc1r and Met signaling pathways is required for HGF-dependent melanoma

Melanocortin 1 receptor (MC1R) signaling stimulates black eumelanin production through a cAMP-dependent pathway. MC1R polymorphisms can impair this process, resulting in a predominance of red phaeomelanin. The red hair, fair skin and UV sensitive phenotype is a well-described melanoma risk factor. MC1R polymorphisms also confer melanoma risk independent of pigment. We investigated the effect of Mc1r deficiency in a mouse model of UV-induced melanoma. C57BL/6-Mc1r+/+-HGF transgenic mice have a characteristic hyperpigmented black phenotype with extra-follicular dermal melanocytes located at the dermal/epidermal junction. UVB induces melanoma, independent of melanin pigmentation, but UVA-induced and spontaneous melanomas are dependent on black eumelanin. We crossed these mice with yellow C57BL/6-Mc1re/e animals which have a non-functional Mc1r and produce predominantly yellow phaeomelanin. Yellow C57BL/6-Mc1re/e-HGF mice produced no melanoma in response to UVR or spontaneously even though the HGF transgene and its receptor Met were expressed. Total melanin was less than in C57BL/6-Mc1r+/+-HGF mice, hyperpigmentation was not observed and there were few extra-follicular melanocytes. Thus, functional Mc1r was required for expression of the transgenic HGF phenotype. Heterozygous C57BL/6-Mc1re/+-HGF mice were black and hyperpigmented and, although extra-follicular melanocytes and skin melanin content were similar to C57BL/6-Mc1r+/+-HGF animals, they developed UV-induced and spontaneous melanomas with significantly less efficiency by all criteria. Thus, heterozygosity for Mc1r was sufficient to restore the transgenic HGF phenotype but insufficient to fully restore melanoma. We conclude that a previously unsuspected melanin-independent interaction between Mc1r and Met signaling pathways is required for HGF-dependent melanoma and postulate that this pathway is involved in human melanoma.

Curcumin does not switch melanin synthesis towards pheomelanin in B16F10 cells

Melanin, the basic skin pigment present also in the majority of melanomas, has a huge impact on the efficiency of photodynamic, radio- or chemotherapies of melanoma. Moreover, the melanoma cells produce more melanin than normal melanocytes in adjacent skin do. Thus, attention has been paid to natural agents that are safe and effective in suppression of melanogenesis. B16F10 cells were studied by electron paramagnetic resonance (EPR) spectroscopy. The cells were cultured for 24-72 h in RPMI or DMEM with or without curcumin. The results confirmed that curcumin has no significant effect on B16F10 cells viability at concentrations of 1-10 µM. Curcumin at concentration of 10 µM significantly inhibited their proliferation and stimulated differentiation. We have not stimulated melanogenesis hormonally but we found a strong increase in melanogenesis in DMEM, containing more L-Tyr, as compared to RPMI. The EPR studies revealed that the effect of curcumin on melanogenesis in RPMI-incubated cells was not significant, and only in DMEM was curcumin able to inhibit melanogenesis. The effect of curcumin was only quantitative, as it did not switch eumelanogenesis towards pheomelanogenesis under any conditions. Interestingly, we observed elevation of production of hydrogen peroxide in DMEM-incubated cells, in parallel to the facilitation of melanogenesis. Curcumin significantly but transiently intensified the already pronounced generation of H2O2 in DMEM. We conclude that the quantitative effect of curcumin on melanogenesis in melanoma is intricate. It depends on the basic melanogenetic efficiency of the cells, and can be observed only in strongly pigmented cells. Qualitatively, curcumin does not switch melanogenesis towards pheomelanogenesis, either in strongly, or in weakly melanized melanoma cells.

Pheomelanin-induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma

The complex interplay of genetic and epigenetic factors linking sun exposure to melanoma in the red hair phenotype hinges on the peculiar physical and chemical properties of pheomelanins and the underlying biosynthetic pathway, which is switched on by the effects of inactivating polymorphisms in the melanocortin 1 receptor gene. In addition to the long recognized UV-dependent pathways of toxicity and cell damage, a UV-independent pro-oxidant state induced by pheomelanin within the genetically determined background of the red hair phenotype has recently been disclosed. This review provides a detailed discussion of the possible UV-dependent and UV-independent chemical mechanisms underlying pheomelanin-mediated oxidative stress, with special reference to the oxygen-dependent depletion of glutathione and other cell antioxidants. The new concept of pheomelanin as a 'living' polymer and biocatalyst that may grow by exposure to monomer building blocks and may trigger autooxidative processes is also discussed. As a corollary, treatment of inflammatory skin diseases in RHP patients is briefly commented. Finally, possible concerted strategies for melanoma prevention in the red hair phenotype are proposed.