Enikő Bodó

Thyroid-stimulating hormone, a novel, locally produced modulator of human epidermal functions, is regulated by thyrotropin-releasing hormone and thyroid hormones

Several elements of the hypothalamic-pituitary-thyroid axis (HPT) reportedly are transcribed by human skin cell populations, and human hair follicles express functional receptors for TSH. Therefore, we asked whether the epidermis of normal human skin is yet another extrathyroidal target of TSH and whether epidermis even produces TSH. If so, we wanted to clarify whether intraepidermal TSH expression is regulated by TRH and/or thyroid hormones and whether TSH alters selected functions of normal human epidermis in situ. TSH and TSH receptor (TSH-R) expression were analyzed in the epidermis of normal human scalp skin by immunohistochemistry and PCR. In addition, full-thickness scalp skin was organ cultured and treated with TSH, TRH, or thyroid hormones, and the effect of TSH treatment on the expression of selected genes was measured by quantitative PCR and/or quantitative immunohistochemistry. Here we show that normal human epidermis expresses TSH at the mRNA and protein levels in situ and transcribes TSH-R. It also contains thyrostimulin transcripts. Intraepidermal TSH immunoreactivity is up-regulated by TRH and down-regulated by thyroid hormones. Although TSH-R immunoreactivity in situ could not be documented within the epidermis, but in the immediately adjacent dermis, TSH treatment of organ-cultured human skin strongly up-regulated epidermal expression of involucrin, loricrin, and keratins 5 and 14. Thus, normal human epidermis in situ is both an extrapituitary source and (possibly an indirect) target of TSH signaling, which regulates defined epidermal parameters. Intraepidermal TSH expression appears to be regulated by the classical endocrine controls that determine the systemic HPT axis.

Human hair follicles are an extrarenal source and a nonhematopoietic target of erythropoietin

Erythropoietin primarily serves as an essential growth factor for erythrocyte precursor cells. However, there is increasing evidence that erythropoietin (EPO)/EPO receptor (EPO‐R) signaling operates as a potential tissue‐protective system outside the bone marrow. Arguing that growing hair follicles (HF) are among the most rapidly proliferating tissues, we have here explored whether human HFs are sources of EPO and targets of EPO‐R‐mediated signaling. Human scalp skin and microdissected HFs were assessed for EPO and EPO‐R expression, and the effects of EPO on organ‐cultured HFs were assessed in the presence/ absence of a classical apoptosis‐inducing chemothera‐peutic agent. Here, we show that human scalp HFs express EPO on the mRNA and protein level in situ, up‐regulate EPO transcription under hypoxic conditions, and express transcripts for EPO‐R and the EPO‐stimulatory transcriptional cofactor hypoxia‐inducible factor‐1α. Although EPO does not significantly alter human hair growth in vitro, it significantly down‐regulates chemotherapy‐induced intrafollicular apoptosis and changes the gene expression program of the HFs. The current study points to intriguing targets of EPO beyond the erythropoietic system: human HFs are an extrarenal site of EPO production and an extrahema‐topoietic site of EPO‐R expression. They may recruit EPO/EPO‐R signaling e.g., for modulating HF apopto‐sis under conditions of hypoxia and chemotherapy‐induced stress.—Bodó, E., Kromminga, A., Funk, W., Laugsch, M., Duske, U., Jelkmann, W., Paus, R. Human hair follicles are an extrarenal source and a non‐hematopoietic target of erythropoietin. FASEB J. 21, 3346–3354 (2007)

Thyrotropin releasing hormone (TRH): a new player in human hair-growth control

Thyrotropin‐releasing hormone (TRH) is the most proximal component of the hypothalamic‐pituitary‐thyroid axis that regulates thyroid hormone synthesis. Since transcripts for members of this axis were detected in cultured normal human skin cells and since human hair follicles (HFs) respond to stimulation with thyrotropin we now have studied whether human HF functions are also modulated by TRH. Here we report that the epithelium of normal human scalp HFs expresses not only TRH receptors (TRH‐R) but also TRH itself at the gene and protein level. Stimulation of microdissected organ‐cultured HFs with TRH promotes hair‐shaft elongation prolongs the hair cycle growth phase (anagen) and antagonizes its termination by TGF‐β2. It also increases proliferation and inhibits apoptosis of hair matrix keratinocytes. These TRH effects may be mediated in part by reducing the ATM/Atr‐dependent phosphorylation of p53. By microarray analysis several differentially up‐ or down‐regulated TRH‐target genes were detected (e.g., selected keratins). Thus human scalp HFs are both a source and a target of TRH which operates as a potent hair‐growth stimulator. Human HFs provide an excellent discovery tool for identifying and dissecting nonclassical functions of TRH and TRH‐mediated signaling in situ, which emerge as novel players in human epithelial biology.—Gáspár, E., Hardenbicker, C., Bodó, E., Wenzel B. Ramot Y. Funk W. Kromminga A. Paus R. Thyrotropin releasing hormone (TRH): a new player in human hair‐growth control. FASEB J. 24, 393–403 (2010). www.fasebj.org

Corticotropin-releasing hormone stimulates the in situ generation of mast cells from precursors in the human hair follicle mesenchyme

Hair follicles (HFs) maintain a peripheral, functional equivalent of the hypothalamic-pituitary-adrenal (HPA) axis, whose most proximal element is corticotropin-releasing hormone (CRH). The mast cell (MC)-rich connective-tissue sheath (CTS) of mouse vibrissa HFs harbors MC precursors. Differentiation of these MC precursors into mature MCs can be induced by stem cell factor (SCF). We have investigated whether the MC progenitors of normal human scalp HF CTS respond to stimulation with CRH. Microdissected anagen HFs and full-thickness scalp skin were treated with CRH (10(-7) M). CRH treatment induced the degranulation of CTS MCs, in addition to increasing the number of CTS MCs in full-thickness skin and HF organ cultures in situ. In the latter, cells with characteristic MC features emigrated from the CTS. CRH-receptor protein expression in the CTS was colocalized with Kit expression on some CTS MCs in situ. CRH treatment upregulated SCF mRNA and protein expression within the HF epithelium. In skin organ culture, CRH-induced degranulation of CTS MCs was abolished by anti-SCF antibody. We demonstrate that human skin is an extramedullary reservoir for MC precursors, and we have identified a regulatory loop between CRH and SCF signaling. This highlights a previously unpublished finding about neuroendocrine control of human MC biology.

Leptin and the skin: a new frontier

Abstract:  Here, we examine the currently available information which supports that the adipokine, leptin, is a major player in the biology and pathology of mammalian skin and its appendages. Specifically, the potent metabolic effects of leptin and its mimetics may be utilized to improve, preserve and restore skin regeneration and hair cycle progression, and may halt or even partially reverse some aspects of skin ageing. Since leptin can enhance mitochondrial activity and biogenesis, this may contribute to the wound healing‐promoting and hair growth‐modulatory effects of leptin. Leptin dependent intracellular signalling by the Janus kinase 2 dependent signal transducer and activator of transcription 3, adenosine monophosphate kinase, and peroxisome proliferator‐activated receptor (PPAR) gamma coactivator/PPAR converges to mediate mitochondrial metabolic activation and enhanced cell proliferation which may orchestrate the potent developmental, trophic and protective effects of leptin. Since leptin and leptin mimetics have already been clinically tested, investigative dermatology is well‐advised to place greater emphasis on the systematic exploration of the cutaneous dimensions and dermatological potential of this pleiotropic hormone.

Thyrotropin powers human mitochondria

Here we demonstrate that the neuropeptide hormone thyrotropin (TSH), which controls thyroid hormone production, exerts a major nonclassical function in mitochondrial biology. Based on transcriptional, ultrastructural, immunohistochemical, and biochemical evidence, TSH up‐regulates mitochondrial biogenesis and consequently activity in organ‐cultured normal human epidermis in situ. Mitochondrial activity was assessed by measuring 2 key components of the respiratory chain. The abundance of mitochondria was assessed employing 2 independent morphological techniques: counting their numbers in human epidermis by high‐magnification light microscopy of skin sections immunostained for mitochondria‐selective cytochrome‐c‐oxidase subunit 1 (MTCO1) and transmission electron microscopy (TEM). Treatment with 10 mU/ml of TSH for 6 d strongly up‐regulates the number of light‐microscopically visualized, MTCO1‐demarcated mitochondria. On the ultrastructural level, TEM confirms that TSH indeed stimulates mitochondrial proliferation and biogenesis in the perinuclear region of human skin epidermal keratinocytes. On the transcriptional level, TSH up‐regulates MTCO1 mRNA (quantitative RT‐PCR) and significantly enhances complex I and IV (cytochrome‐c‐oxidase) activity. This study pioneers the concept that mitochondrial energy metabolism and biogenesis in a normal, prototypic human epithelial tissue underlies potent neuroendocrine controls and introduces human skin organ culture as a clinically relevant tool for further exploring this novel research frontier in the control of mitochondrial biology.—Poeggeler, B., Knuever, J., Gáspár, E., Bíró, T., Klinger, M., Bodó, E., Wiesner, R J., Wenzel, B. E., Paus, R. Thyrotropin powers human mitochondria. FASEB J. 24, 1525–1531 (2010). www.fasebj.org

α-Melanocyte-stimulating hormone: a protective peptide against chemotherapy-induced hair follicle damage?

Effective, safe and well‐tolerated therapeutic and/or preventive regimens for chemotherapy‐induced alopecia (CIA) still remain to be developed. Because α‐melanocyte‐stimulating hormone (α‐MSH) exerts a number of cytoprotective effects and is well tolerated, we hypothesized that it may be a candidate CIA‐protective agent.

Modulation of Chemotherapy-Induced Human Hair Follicle Damage by 17-β Estradiol and Prednisolone: Potential Stimulators of Normal Hair Regrowth by “Dystrophic Catagen” Promotion?

DNA repair deficiency in human xeroderma pigmentosum group a and C cells by recombinant adenovirusmediated gene transfer. Hum Gene Ther 13:1833–44 Uchida A, Sugasawa K, Masutani C, Dohmae N, Araki M, Yokoi M et al. (2002) The carboxyterminal domain of the XPC protein plays a crucial role in nucleotide excision repair through interactions with transcription factor IIH. DNA Repair 1:449–61 Zeng L, Quilliet X, Chevallier-Lagente O, Eveno E, Sarasin A, Mezzina M (1997) Retrovirusmediated gene transfer corrects DNA repair defect of xeroderma pigmentosum cells of complementation groups A, B and C. Gene Ther 4:1077–84

Immunomodulatory effects of the α-melanocyte-stimulating hormone-related tripeptide K(D)PT on human scalp hair follicles under proinflammatory conditions

Remarkably, the mother of the family examined by Westerhof et al. also had discrete lesions. Male subjects are somewhat retarded in growth and may have low intelligence. A relationship between Westerhof syndrome and TSC has been suggested. Genetic studies in our patients are not definitive because TSC1 and TSC2 are large genes and molecular analysis fails to identify a mutation in approximately 15% of patients with TSC. Moreover, the rate of gonadal or somatic mosaicism is very high and genetic testing on peripheral lymphocytes is not always able to detect mosaicism for the TSC1 or TSC2 genes. However, café-au-lait spots are not found in TSC in greater numbers than in the normal population. Thus, when multiple light and dark macules occur from birth in a patient, one should suspect Westerhof syndrome, not TSC. Westerhof et al. suggested the most probable mode of inheritance to be autosomal dominant. However, the present cases could also be autosomal recessive. Otherwise, the few hyperpigmented spots in the mother should be taken as an example of gonadal and somatic mosaicism. Until we know what the Westerhof phenotype is, the twin spotting phenomenon could be the most likely explanation for it. Cutis tricolor is a term introduced in 1997 by Happle et al. to describe the coexistence of congenital hyperand hypopigmented macules that tend to show a spatial proximity in a background of normal skin. Subsequently some other patients have been reported, as cases of an isolated skin disorder or as part of a neurocutaneous malformation syndrome. Most cases have occurred sporadically and have tentatively been explained by the mechanism of didymosis or twin spotting, a manifestation of skin mosaicism. During embryogenesis, somatic recombination of two genetically different clones of neighbouring cells leads phenotypically to two different lesions in close proximity to each other. The extent of lesions depends on the time of the somatic crossing-over (the earlier the event, the larger the area involved). Moreover, the embryonic (lateralization) movements of the trunk region could well explain the lack of strictly spatial proximity in some phenotypes (as Westerhof syndrome could be). Familial cutis tricolor has been reported in two sisters. It has been suggested that these cases may represent an example of paradominant inheritance. Such a non-Mendelian form of inheritance may imitate an autosomal dominant mode of transmission. Heterozygous individuals are phenotypically normal, and the mutation can therefore be transmitted unperceived through many generations. The trait becomes manifest only when a somatic mutation occurs at an early developmental stage, giving rise to loss of heterozygosity and forming a homozygous or hemizygous population of cells. As a result, the embryo will become a mosaic. Although speculative, a similar pathogenic mechanism could have occurred in our patients. As the number of reported cases of Westerhof syndrome is small it seems too early to determine the real incidence of systemic involvement, although growth retardation appears to be a clear association. This should be borne in mind for providing appropriate genetic counselling.

Does erythropoietin modulate human hair follicle melanocyte activities in situ

Abstract:  Erythropoietin (EPO) is now appreciated for not only drive erythopoiesis, but also to exert additional functions. Since we had previously shown that human hair follicles (HFs) are both an extra‐renal source and an extra‐medullary target of EPO, we have now studied whether one such function is the regulation of HF pigmentation. Human anagen VI HFs were treated with EPO (100 IU/ml) in serum‐free organ culture. Unexpectedly, we noticed greatly divergent pigmentary effects of EPO, since both up‐ and down‐regulation of HF melanin content and tyrosinase activity in situ was seen in HF derived from different individuals. These divergent effects could not be attributed to differences in skin regions, the total HF melanocyte number or specific traits of individual HF donors. Our pilot study provides first evidence suggesting that EPO may modulate normal human melanocyte functions under physiologically relevant conditions in situ.