Human Skin Physiology Research Articles

Genome-wide transcriptome analysis of human epidermal melanocytes

Because human epidermal melanocytes (HEMs) provide critical protection against skin cancer, sunburn, and photoaging, a genome-wide perspective of gene expression in these cells is vital to understanding human skin physiology. In this study we performed high throughput sequencing of HEMs to obtain a complete data set of transcript sizes, abundances, and splicing. As expected, we found that melanocyte specific genes that function in pigmentation were among the highest expressed genes. We analyzed receptor, ion channel and transcription factor gene families to get a better understanding of the cell signaling pathways used by melanocytes. We also performed a comparative transcriptomic analysis of lightly versus darkly pigmented HEMs and found 16 genes differentially expressed in the two pigmentation phenotypes; of those, only one putative melanosomal transporter (SLC45A2) has known function in pigmentation. In addition, we found 166 transcript isoforms expressed exclusively in one pigmentation phenotype, 17 of which are genes involved in signal transduction. Our melanocyte transcriptome study provides a comprehensive view and may help identify novel pigmentation genes and potential pharmacological targets.

Zinc, its biological role and use in dermatology

This literature review detines the biological role ot zinc in the human body, immune homeostasis and skin physiology as well as pathophysiology ot skin diseases. It describes the current range ot systemic and topical zinc preparations and their pharmacological characteristics. The review also describes skin diseases that may be treated with the use ot zinc preparations on a grounded basis, and discloses the clinical experience ot the use ot these drugs described in the world literature. It sets out certain recommendations tor using zinc preparations in clinical practice.

Antimicrobial peptides and pro‐inflammatory cytokines are differentially regulated across epidermal layers following bacterial stimuli

The skin is a natural barrier between the body and the environment and is colonised by a large number of microorganisms. Here, we report a complete analysis of the response of human skin explants to microbial stimuli. Using this ex vivo model, we analysed at both the gene and protein level the response of epidermal cells to Staphylococcus epidermidis (S. epidermidis) and Pseudomonas fluorescens (P. fluorescens), which are present in the cutaneous microbiota. We showed that both bacterial species affect the structure of skin explants without penetrating the living epidermis. We showed by real-time quantitative polymerase chain reaction (qPCR) that S. epidermidis and P. fluorescens increased the levels of transcripts that encode antimicrobial peptides (AMPs), including human β defensin (hBD)2 and hBD3, and the pro-inflammatory cytokines interleukin (IL)-1α and (IL)-1-β, as well as IL-6. In addition, we analysed the effects of bacterial stimuli on the expression profiles of genes related to innate immunity and the inflammatory response across the epidermal layers, using laser capture microdissection (LCM) coupled to qPCR. We showed that AMP transcripts were principally upregulated in suprabasal keratinocytes. Conversely, the expression of pro-inflammatory cytokines was upregulated in the lower epidermis. These findings were confirmed by protein localisation using specific antibodies coupled to optical or electron microscopy. This work underscores the potential value of further studies that use LCM on human skin explants model to study the roles and effects of the epidermal microbiota on human skin physiology.

Tumour Necrosis Factor Alpha, Interferon Gamma and Substance P Are Novel Modulators of Extrapituitary Prolactin Expression in Human Skin

Human scalp skin and hair follicles (HFs) are extra-pituitary sources of prolactin (PRL). However, the intracutaneous regulation of PRL remains poorly understood. Therefore we investigated whether well-recognized regulators of pituitary PRL expression, which also impact on human skin physiology and pathology, regulate expression of PRL and its receptor (PRLR) in situ. This was studied in serum-free organ cultures of microdissected human scalp HFs and skin, i.e. excluding pituitary, neural and vascular inputs. Prolactin expression was confirmed at the gene and protein level in human truncal skin, where its expression significantly increased (p = 0.049) during organ culture. There was, however, no evidence of PRL secretion into the culture medium as measured by ELISA. PRL immunoreactivity (IR) in female human epidermis was decreased by substance P (p = 0.009), while neither the classical pituitary PRL inhibitor, dopamine, nor corticotropin-releasing hormone significantly modulated PRL IR in HFs or skin respectively. Interferon (IFN) γ increased PRL IR in the epithelium of human HFs (p = 0.044) while tumour necrosis factor (TNF) α decreased both PRL and PRLR IR. This study identifies substance P, TNFα and IFNγ as novel modulators of PRL and PRLR expression in human skin, and suggests that intracutaneous PRL expression is not under dopaminergic control. Given the importance of PRL in human hair growth regulation and its possible role in the pathogenesis of several common skin diseases, targeting intracutaneous PRL production via these newly identified regulatory pathways may point towards novel therapeutic options for inflammatory dermatoses.

Skin Effects of Dioxins

Dioxins is a compound family among persistent organic pollutants toxics produced by industrial wastes. 2,3,7,8-Tetrachlorodibenzo -p-dioxin (TCDD) is a typical representative of dioxins, which not only exhibits systemic carcinogenicity, teratogenicity, immunotoxicity, hepatotoxicity, endocrine disruption and waste syndrome to humans, but also has effects on physiology and pathology of human skin. In general, chloracne is the most sensitive and specific marker for a possible dioxin intoxication. Clinically chloracne is an acneiform dermatosis, characterized by an eruption of multiple comedone-like cysts involving the face and as well as other areas. Atrophy or absence of sebaceous glands and infundibular dilatation or cystic formation of hair follicles could be detected histopathologically. In addition, erythema, oedema, decreased sebum secretion with skin xerosis, pigmentation, porphyrinopathy, hirsutism, skin thickening, palmoplantar hyperhidrosis and palmoplantar hyperkeratotis of sweat gland origin have also been reported after TCDD intoxication. TCDD exhibits various effects on cellular differentiation, inducing melanogenesis and complicated actions on skin inflammation and immunity. The aryl hydrocarbon receptor signaling pathway and epidermal stem cells may be involved in TCDD activity. No effective treatment of TCDD exists

English

Human skin is the largest exposed area of our body. There are number of physiological changes which may occur in response to internal or external sources. Biophysical techniques have been extensively employed to study any changes in human skin physiology. Usually these bioengineering techniques are equipped with non-invasive probes. Visioscan, Corneometer and Tewameter are the most widely used techniques in the characterization parameters of skin physiology, like skin hydration, transepidermal water loss and skin wrinkles. This research covers all aspects of these parameters, in skin analysis.   Key words: Skin, corneometer, tewameter, visioscan, skin hydration, transepidermal water loss (TEWL).

Milestones in Melanocytes/Melanogenesis

Melanocytes and their production of melanin pigment (a process called melanogenesis) have important roles in determining the physiology of human skin. The amount and type of melanin produced, as well as its eventual distribution in the epidermis, dramatically affects visible color, which ultimately determines the various functions of the pigment, such as photoprotection. ‘‘Normal’’ pigmentation is regulated by 4250 genes (as per the latest count), and they function during the development, migration, survival, proliferation, and differentiation of melanocytes and their precursors (melanoblasts). Disruptions of skin pigmentation can occur at all of these stages, and mutations in these pigment-related genes typically lead to characteristic pigmentary diseases. Pigmentation in the lower species is critical for survival (as camouflage), thermal regulation, etc. In humans, however, it is important not only for cosmetic reasons but also to protect the skin from UV damage and the subsequent risk of skin cancers. With respect to susceptibility to skin cancers, melanocyte function seems to be important at many levels in addition to the simple sunscreen effect of the melanin pigment per se. The chemical and enzymatic processes involved in the synthesis of different types of melanins have also been gradually elucidated. The study of genes involved in regulating mammalian pigmentation has had a dramatic advantage owing to the visible effects of mutations in these genes, and pigment variants of mice, fish, birds, and other species have been collected for centuries, providing a rich resource for understanding the complex nature of their interactions. Combined with the dramatic advances in methods for gene sequencing, and functional analysis, our understanding of the complex regulation of human skin pigmentation—and its disruptions in pigmentary diseases—has advanced rapidly.

Effects of temperature steps on human skin physiology and thermal sensation response

Air-conditioning is frequently used as a means of adjusting indoor thermal environment in hot-and-humid areas. However, when entering an air-conditioned building from outdoors people may experience thermal discomfort and risk health consequence if the instantaneous change of air temperature exceeds the thermoregulatory capacity. A study was conducted to investigate the alteration in thermal perception and in thermoregulation that simultaneously occurred in response to temperature step in a thermal transient. In this study, two temperature down-steps from 32/28 to 24 °C and an up-step from 20 to 24 °C were created in a climatic chamber consisting of two microclimate-controlled rooms, and subjects were evaluated for change in thermal sensation as well as in skin physiological properties, including skin capillary blood flow (SCBF), skin moisture, transepidermal water loss (TEWL), and skin temperature over the course of acclimation. As the results show, a cold sensation overshot occurred in thermal sensation vote (TSV), skin temperature, and SCBF in 1 min after the temperature dropped from 32 to 24 °C. TSV correlated the best with skin temperature ( r = 0.60) and moderately with skin moisture and TEWL ( r = 0.42–0.54) when the temperature down-step reached 8 °C. TEWL acclimated in a two-stage pattern, demonstrating a difference between the sensational change and thermoregulation. The gender-specific influence occurred in thermoregulation but not in subjective sensation. The findings of the study suggest that thermoregulatory burden might be adequately controlled when the temperature step in thermal transition zone is limited to 4 °C or lower.

Spatial-temporal modulation of CCN proteins during wound healing in human skin in vivo

CCN proteins are important modulators of development and function of adult organs. In this study, we examined the localization and expression of the six CCN family members in normal adult human skin and during wound healing in vivo. Transcript and protein expression were studied by laser-capture microdissection-coupled real-time PCR and immunohistochemistry, respectively. Our results demonstrate that CCN1, CCN4, and CCN6 are expressed at relatively low levels in normal human skin. CCN2, CCN3, and CCN5 are the most highly expressed transcripts in the epidermis. CCN3 and CCN5 proteins are prominent in epidermal keratinocytes, whereas CCN2 is primarily expressed in melanocytes. Differential expression within epidermal layers suggests that CCN3 and CCN5 are linked with keratinocyte differentiation. CCN2, CCN3 and CCN5, are the three most highly expressed transcripts in the dermis. Their respective proteins are produced to various extents by dermal fibroblasts, blood vessels, eccrine sweat glands and hair follicles. We find that most CCN family members are temporally and specifically regulated during different phases (inflammation, proliferation, and remodeling) of partial thickness wound repair. By highlighting spatial-temporal regulations of CCN family member expression in relation to cell proliferation and differentiation, our results suggest a diverse range of functions for CCN proteins in both epidermal and dermal cells, and provides a solid reference for interpretation of future studies aimed at understanding the role of CCN proteins in human skin physiology and diseases.

Bacteriology of humans: an ecological perspective

Preface. Abbreviations of genera. 1. The human-microbe symbiosis . 1.1. Overview of the nature and distribution of the microbial communities inhabiting humans. 1.2. Environmental determinants that affect the distribution and composition of microbial communities. 1.3. Host characteristics that affect the indigenous microbiota. 1.4. Techniques used to characterize the microbial communities inhabiting humans. 1.5. The epithelium - site of host-microbe interactions. 1.6. Further reading. 2. The indigenous microbiota of the skin . 2.1. Anatomy and physiology of human skin. 2.2. Cutaneous antimicrobial defense systems. 2.3. Environmental determinants operating at different skin regions. 2.4. The indigenous microbiota of the skin. 2.5. Overview of the cutaneous microbiota. 2.6. Sources of data used to compile figures. 2.7. Further reading. 3 . The indigenous microbiota of the eye. 3.1. Anatomy and physiology of the eye. 3.2. Antimicrobial defense systems of the eye. 3.3. Environmental determinants on the conjunctival surface. 3.4. The indigenous microbiota of the eye. 3.5. Overview of the ocular microbiota. 3.6. Sources of data used to compile figures. 3.7. Further reading. 4. The indigenous microbiota of the respiratory tract. 4.1. Anatomy and physiology of the respiratory tract. 4.2. Antimicrobial defense systems of the respiratory tract. 4.3. Environmental determinants within the respiratory tract. 4.4. Indigenous microbiota of the respiratory tract. 4.5. Overview of the respiratory microbiota 4.6. Sources of data used to compile figures 4.7. Further reading. 5 . The indigenous microbiota of the urinary system of females . 5.1. Anatomy and physiology of the urinary system of females. 5.2. Antimicrobial defenses of the female urinary system. 5.3. Environmental determinants within the female urethra. 5.4. The indigenous microbiota of the female urethra. 5.5. Overview of the microbiota of the urinary tract of females. 5.6. Sources of data used to compile figures. 5.7. Further reading. 6 . The indigenous microbiota of the reproductive system of females . 6.1. Anatomy and physiology of the female reproductive system. 6.2. Antimicrobial defense systems of the female reproductive system. 6.3. Environmental determinants at different regions of the reproductive system. 6.4. The indigenous microbiota of the female reproductive system. 6.5. Overview of the microbiota of the female reproductive system. 6.6. Sources of data used to compile figures. 6.7. Further reading. 7. The indigenous microbiota of the urinary and reproductive systems of males. 7.1. Anatomy and physiology. 7.2. Antimicrobial defenses of the male urinary and reproductive systems. 7.3. Environmental determinants within the male urinary and reproductive systems. 7.4. The indigenous microbiota of the male urinary and reproductive systems. 7.5. Overview of the microbiota of the male urinary and reproductive systems. 7.6. Sources of data used to compile figures. 7.7. Further reading. 8 . The indigenous microbiota of the oral cavity . 8.1. Anatomy and physiology of the oral cavity. 8.2. Antimicrobial defense systems of the oral cavity. 8.3. Environmental determinants at the various sites within the oral cavity. 8.4. The indigenous microbiota of the oral cavity. 8.5. Overview of the oral microbiota. 8.6. Sources of data used to compile figures. 8.7. Further reading. 9 . The indigenous microbiota of the gastrointestinal tract . 9.1. Anatomy and physiology of the gastrointestinal tract. 9.2. Antimicrobial defense systems of the gastrointestinal tract. 9.3. Environmental determinants within different regions of the gastrointestinal tract. 9.4. The indigenous microbiota of the gastrointestinal tract. 9.5. Overview of the indigenous microbiota of the gastrointestinal tract. 9.6. Sources of data used to compile figures. 9.7. Further reading. 10 . The future . 10.1. Further reading. Index

A new redox-dependent mechanism of MMP-1 activity control comprising reduced low-molecular-weight thiols and oxidizing radicals

Matrix metalloproteinases (MMPs), a family of zinc-dependent proteinases, participate in remodeling and degradation of the extracellular matrix proteins. The activity of MMPs is thought to be predominately posttranslationally regulated via proteolytic activation of precursor zymogens or via their naturally occurring endogenous inhibitors. Here, using recombinant MMP-1, we investigated new redox-dependent mechanisms of proteinase activity regulation by low-molecular-weight thiols. We find that glutathione (GSH), cysteine, homocysteine, and N-acetylcysteine at physiological concentrations competitively reduce MMP-1 activity up to 75% with an efficiency of cysteine > or = GSH > homocysteine > N-acetylcysteine. In contrast, S-derivatized thiols completely lack this inhibitory activity. Interestingly, the competitive GSH-mediated inhibition of MMP-1-activity can be fully reversed abrogated by oxidizing radicals like (*)NO(2) or Trolox radicals, here generated by UVA irradiation of nitrite or Trolox, two relevant agents in human skin physiology. This redox-dependent reactivation of the inactive GSH-MMP-1-complex comprises GSH oxidation and is significantly inhibited in the presence of ascorbic acid, an effective (*)NO(2) and Trolox radical scavenger. We here offer a new concept of redox-sensitive control of MMP-1 activity based on the inhibitory effect of reduced thiols and reactivation by a mechanism comprising derivatization or oxidation of the MMP-1-bound inhibitory-acting thiol.

Evidence for a physiological role of intracellularly occurring photolabile nitrogen oxides in human skin fibroblasts

Nitric oxide (NO) plays a pivotal role in human skin biology. Cutaneous NO can be produced enzymatically by NO synthases (NOS) as well as enzyme independently via photodecomposition of photolabile nitrogen oxides (PNOs) such as nitrite or nitroso compounds, both found in human skin tissue in comparably high concentrations. Although the physiological role of NOS-produced NO in human skin is well defined, nothing is known about the biological relevance or the chemical origin of intracellularly occurring PNOs. We here, for the first time, give evidence that in human skin fibroblasts (FB) PNOs represent the oxidation products of NOS-produced NO and that in human skin fibroblasts intracellularly occurring PNOs effectively protect against the injurious effects of UVA radiation by a NO-dependent mechanism. In contrast, in PNO-depleted FB cultures an increased susceptibility to UVA-induced lipid peroxidation and cell death is observed, whereas supplementation of PNO-depleted FB cultures with physiological nitrite concentrations (10 μM) or with exogenously applied NO completely restores UVA-increased injuries. Thus, intracellular PNOs are biologically relevant and represent an important initial shield functioning in human skin physiology against UVA radiation. Consequently, nonphysiological low PNO concentrations might promote known UVA-related skin injuries such as premature aging and carcinogenesis.

The impact of nitrite and antioxidants on ultraviolet-A-induced cell death of human skin fibroblasts

Nitrite (NO 2 −) occurs ubiquitously in biological fluids such as blood and sweat. Ultraviolet A-induced nitric oxide formation via decomposition of cutaneous nitrite, accompanied by the production of reactive oxygen (ROS) or nitrogen species (RNS), represents an important source for NO in human skin physiology. Examining the impact of nitrite and the antioxidants glutathione (GSH), Trolox (TRL), and ascorbic acid (ASC) on UVA-induced toxicity of human skin fibroblasts (FB) we found that NO 2 − concentration-dependently enhances the susceptibility of FB to the toxic effects of UVA by a mechanism comprising enhanced induction of lipid peroxidation. While ASC completely protects FB cultures from UVA/NO 2 −-induced cell damage, GSH or TRL excessively enhances UVA/NO 2 −-induced cell death by a mechanism comprising nitrite concentration-dependent TRL radical formation or GSH-derived oxidative stress. Simultaneously, in the presence of GSH or TRL the mode of UVA/NO 2 −-induced cell death changes from apoptosis to necrosis. In summary, during photodecomposition of nitrite, ROS or RNS formation may act as strong toxic insults. Although inhibition of oxidative stress by NO and other antioxidants represents a successful strategy for protection from UVA/NO 2 −-induced injuries, GSH and TRL may nitrite-dependently aggravate the injurious impact by TRL or GSH radical formation, respectively.

Hamster (Mesocricetus auratus) cheek pouch as an experimental model to investigate human skin and keloid heterologous graft

To describe the integration process of grafts of total human skin and keloid in hamster (Mesocricetus auratus) cheek pouch, whose sub-epithelium is naturally an "Immunologically Privileged Site". Fragments of human normal skin and keloid from the breast region of mulatto female patients were transplanted into the cheek pouch subepithelium in situ. Surgical procedure and grafted pouches for microscopic exam at several time points of the transplantation were standardized. The integration of grafted fragments of human skin and keloid was seen in late periods (84 days) since the microscopic assessment showed the presence of blood vases within the conjunctive tissue of grafted fragments. It was also possible to see among the grafted fragments the epithelium, the appearing of early cellular infiltrated, epithelial secretion of keratin, the presence of melanocytes, and delayed changes on the aspect of collagen fibers of conjunctive tissue. Pooled results allow to define hamster cheek pouch sub-epithelium as an experimental model to investigating heterologous graft physiology of human total skin and keloid with epithelium.

Integração do enxerto heterólogo de pele humana no subepitélio da bolsa jugal do hamster (Mesocricetus auratus)

OBJETIVO: Descrever a integração de enxertos de pele total humana no subepitélio da bolsa jugal do hamster (Mesocricetus auratus). MÉTODOS: A amostragem consistiu de 18 hamsters machos, exogâmicos, com 10 a 14 semanas de idade. Fragmentos de pele humana normal foram obtidos de pele excedente de mastoplastia redutora de paciente parda. Cada hamster foi enxertado em ambas as bolsas com fragmentos de pele, perfazendo um total de 36 fragmentos enxertados. Os animais foram distribuídos, em 6 grupos, para exame dos fragmentos enxertados com 5, 12, 21, 42, 84 e 168 dias. Uma avaliação macroscópica foi realizada comparando a bolsa contendo o fragmento enxertado em cada período com a mesma bolsa no pós-operatório imediato, mediante fotografias padronizadas. Na avaliação microscópica foi adotado como critério de integração a presença de vasos sangüíneos na derme dos enxertos. Observou-se também a presença de queratina, melanócitos, infiltrado celular e aspecto do tecido conjuntivo. RESULTADOS: Na avaliação macroscópica foi observada uma reação vascular em torno dos fragmentos até 12 dias do implante, e a presença de pigmentação castanho-escura a partir de 42 dias. À microscopia, integraram-se 80,64% dos fragmentos enxertados, inclusive no grupo de 168 dias. Observou-se infiltrado celular inflamatório até 12 dias, a presença de melanócitos a partir de 42 dias e uma hialinização do tecido conjuntivo após 84 dias. CONCLUSÕES: Fragmentos de pele humana integram-se no tecido celular subcutâneo da bolsa jugal do hamster, mantêm-se vascularizados por 168 dias, e conservam o epitélio íntegro até 21 dias. O subepitélio da bolsa representa modelo experimental de investigação da fisiologia de pele humana ex vivo.

In this Issue

In this Issue

Assessing the Bioactivity of Cosmetic Products and Ingredients

Cosmetic ingredients can produce physical effects on the skin as well as positive and negative bioactive effects. Such effects have now been identified, categorized and interpreted. Because of this ongoing research and increased understanding, cosmetics, especially skin care products, are being improved. Targeting specific bioactive effects from newly developed cosmetic products is now possible. This development is aided by refining and expanding existing instrumental analysis which is now capable of elucidating more detailed and statistically significant differences from the use of certain ingredients in cosmetics. However, the ultimate proof of these changes will remain the consumer response to such products. Physical effects and the positive and negative bioactive effects from specific cosmetic ingredients will be discussed in relationship to the anatomy, physiology and condition of human skin. Examples of selected cosmetic ingredients in relationship to the anatomy, physiology and condition of human skin will be given. Demonstrations of selected cosmetic ingredient effects will be by way of clinical observation, instrumental analysis and consumer evaluation.

Expression of proopiomelanocortin (POMC)-derived melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH) peptides in skin of basal cell carcinoma patients

We proposed that local expression and production of proopiomelanocortin (POMC) peptides may play a role in human skin physiology and pathology, including the development and progression of skin cancers. Reverse transcription polymerase chain reaction (RT-PCR) and Northern blotting hybridization techniques were used to study gene expression. Reversed-phase (RP) high-pressure liquid chromatography (HPLC) separation with subsequent radioimmunoassays were used to identify alpha-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH) peptides. Immunocytochemistry (IHC) was used to localize ACTH, α-MSH, and β-MSH antigens in skin. RT-PCR, RP-HPLC, and IHC analyses documented the expression of POMC mRNA and production of ACTH and α-MSH peptides in lesional and perilesional skin of basal cell carcinoma (BCC) patients and in cultured keratinocytes, which was accompanied by the expression of the MC1-R gene encoding the receptor activated by MSH and ACTH. Thirty specimens were analyzed by IHC. Immunoreactive α-MSH, β-MSH, and ACTH were detected, in 21 of 21, in 11 of 20, and in 6 of 8 of lesional skin, and in 6 of 6, in 5 of 7, and in 6 of 8 perilesional skin specimens analyzed, respectively. Antigen distribution was heterogenous and present in BCC, epidermis, hair follicles, dermal mononuclear cells, and extra-cellular matrix. We conclude that messenger RNA for POMC, MC1-R, and the peptides MSH and ACTH are produced in skin of BCC patients. Because keratinocytes are a target for MSH and ACTH bioregulation, the production of these peptides is stimulated by UVB, and the peptides can act as immunosupressors, we suggest that MSH and ACTH may facilitate development of BCC.

Does interleukin-1 induce hair loss?

Cytokines play an important role in both physiology and pathophysiology of human skin, and the possibility that they coordinate the cyclical hair growth cannot be excluded. Several clinical and experimental data point towards interleukin-1 which might be a crucial inducer of hair loss in various hair disease. An aberrant expression of interleukin-1 beta was detected in affected areas of the scalp in alopecia areata. On the other hand, interleukin-1 has been shown to be a potent inhibitor of human hair growth in vitro. Mice showing an overexpression of the interleukin-1 alpha gene develop patchy hair loss. Taking all of the presently available data together, we hypothesize that interleukin-1 is a crucial mediator inducing cessation of hair growth.

Localization of messenger ribonucleic acid for insulin-like growth factor-binding proteins in human skin by in situ hybridization.

The role of the insulin-like growth factors (IGFs) in human skin physiology has been increasingly recognized, although relatively little is known about the cell types involved or the cellular mechanisms that mediate these responses. Epidermal keratinocytes and dermal fibroblasts both possess IGF-I receptors and are responsive to IGF-I. IGF-binding proteins (IGFBPs), known modulators of IGF action, may also be responsible for targeting IGF-I to its receptors and are produced by both cultured keratinocytes and fibroblasts. To demonstrate sites of production of IGFBPs in human skin, we have used in situ hybridization to localize messenger ribonucleic acid (mRNA) for the six IGFBPs. Antisense and sense RNA probes for the IGFBPs (IGFBP-1 to -6) were produced, and 5-microns sections of normal adult human male chest skin were probed. The control probe used was keratin-5, which is known to hybridize to the basal keratinocytes of the epidermis. mRNAs for human IGFBP-2, -3, -4, and -5 were identified, with mRNAs for IGFBP-2 and IGFBP-4 localized in sebaceous glands and eccrine sweat glands (epidermal origin), IGFBP-3 mRNA in the basal layer of the epidermis and mRNAs for IGFBP-4, and IGFBP-5 found throughout the dermis. mRNAs for IGFBP-1 and -6 were not identified in human skin. These studies demonstrate specific localization of IGFBP mRNAs in adult human skin, suggesting that each IGFBP may play a specific role in targeting IGF-I to its receptor on responsive cells and, ultimately, in modulation of IGF-I action in skin.