Leptin is an autocrine/paracrine regulator of wound healing

The Intersection of the Pathogenic Processes Underlying Psoriasis and the Comorbid Condition of Obesity

In the past decade, our understanding of psoriasis pathogenesis has made significant steps forward, leading to the development of multiple game-changing therapies. While psoriasis primarily affects the skin, it is increasingly recognized as a systemic disease that can have effects beyond the skin. Obesity is associated with more severe forms of psoriasis and can potentially worsen the systemic inflammation and metabolic dysfunction seen in psoriatic patients. The exact mechanisms underlying the link between these two conditions are not fully understood, but it is believed that chronic inflammation and immune dysregulation play a role. In this review, we examine the existing body of knowledge regarding the intersection of pathogenic processes responsible for psoriasis and obesity. The ability of biological therapies to reduce systemic and obesity-related inflammation in patients with psoriasis will be also discussed.

White adipocyte dysfunction and obesity-associated pathologies in humans

The prevalence of obesity and associated chronic diseases continues to increase worldwide, negatively impacting on societies and economies. Whereas the association between excess body weight and increased risk for developing a multitude of diseases is well established, the initiating mechanisms by which weight gain impairs our metabolic health remain surprisingly contested. In order to better address the myriad of disease states associated with obesity, it is essential to understand adipose tissue dysfunction and develop strategies for reinforcing adipocyte health. In this Review we outline the diverse physiological functions and pathological roles of human white adipocytes, examining our current knowledge of why white adipocytes are vital for systemic metabolic control, yet poorly adapted to our current obesogenic environment.

The potential effect of leptin co-administration on photodynamic damage using quail chorioallantoic membrane model

BACKGROUND

The chorioallantoic membrane (CAM) of the Japanese quail is an excellent model for studying photodynamic therapy (PDT) due to its rich vascularization. PDT is used not only in oncological treatment but also in infectious diseases, or psoriasis, where it yields significant advantages. This treatment also has its limitations, such as burning, itching, erythema, redness, swelling, and delayed wound healing. The aim of this study was to analyse the potentially protective properties of the tissue hormone leptin during PDT.

METHODS

Japanese quail embryos incubated ex ovo were used in this experiment. On the 9th day of embryonic development, leptin (5 μg) and photosensitiser hypericin (79 μM) were topically applied, followed by irradiation. The effect of leptin co-administration was evaluated from CAM images and histological structure analysis, histological samples, and qPCR, where the expression of genes involved in angiogenesis, apoptosis, and oxidative stress was monitored.

RESULTS

We observed vascular damage in all experimental groups, the highest damage was found after the application of hypericin without leptin coadministration. Histological analysis confirmed the protective effect of leptin. qPCR analysis presented differences in FREK gene expression, but also in genes involved in oxidative stress like SOD, NRF-1, NRF-2, and GPX7. The application of leptin significantly reduced the expression of apoptosis regulatory proteins CASP3, cytochrome C, and APAF1.

CONCLUSIONS

Our results in the CAM model suggest a possible protective effect of leptin to prevent PDT damage and aid in the subsequent regeneration of target tissues after antimicrobial PDT.

LEP and LEPR are possibly a double-edged sword for wound healing

Wound healing is a complex and error-prone process. Wound healing in adults often leads to the formation of scars, a type of fibrotic tissue that lacks skin appendages. Hypertrophic scars and keloids can also form when the wound-healing process goes wrong. Leptin (Lep) and leptin receptors (LepRs) have recently been shown to affect multiple stages of wound healing. This effect, however, is paradoxical for scarless wound healing. On the one hand, Lep exerts pro-inflammatory and profibrotic effects; on the other hand, Lep can regulate hair follicle growth. This paper summarises the role of Lep and LepRs on cells in different stages of wound healing, briefly introduces the process of wound healing and Lep and LepRs, and examines the possibility of promoting scarless wound healing through spatiotemporal, systemic, and local regulation of Lep levels and the binding of Lep and LepRs.

Adipocyte plasticity in tissue regeneration, repair, and disease

Mammalian tissue repair forms a scar that fills the injured area with a fibrotic lesion, limiting tissue function. Adipocytes, lipid-filled cells, well-known for energy storage and endocrine functions, can reside adjacent to or within many tissues, and are emerging as critical regulators of tissue repair. In this review, the plasticity and function of adipocytes to tissue repair and fibrosis in four tissues: skin, heart, skeletal muscle, and mammary gland, will be discussed. The dynamic nature of adipocytes as they release bioactive products, lipids, and adipokines, and their ability to form contractile fibroblasts, is emerging as an essential regulator of wound healing and tumorigenesis in multiple tissues. Thus, modulation of adipocytes may provide therapeutic avenues for regenerative medicine and cancer.

The Head-to-Toe Hormone: Leptin as an Extensive Modulator of Physiologic Systems

Leptin is a well-known hunger-sensing peptide hormone. The role of leptin in weight gain and metabolic homeostasis has been explored for the past two decades. In this review, we have tried to shed light upon the impact of leptin signaling on health and diseases. At low or moderate levels, this peptide hormone supports physiological roles, but at chronically higher doses exhibits detrimental effects on various systems. The untoward effects we observe with chronically higher levels of leptin are due to their receptor-mediated effect or due to leptin resistance and are not well studied. This review will help us in understanding the non-anorexic roles of leptin, including their contribution to the metabolism of various systems and inflammation. We will be able to get an alternative perspective regarding the physiological and pathological roles of this mysterious peptide hormone.

Lipoaspirate Shows In Vitro Potential for Wound Healing

Mesenchymal stem cells (MSCs) are a promising therapy in wound healing, although extensive time and manipulation are necessary for their use. In our previous study on cartilage regeneration, we demonstrated that lipoaspirate acts as a natural scaffold for MSCs and gives rise to their spontaneous outgrowth, together with a paracrine effect on resident cells that overcome the limitations connected to MSC use. In this study, we aimed to investigate in vitro whether the microfragmented adipose tissue (lipoaspirate), obtained with Lipogems^® technology, could promote and accelerate wound healing. We showed the ability of resident cells to outgrow from the clusters of lipoaspirate encapsulated in a 3D collagen substrate as capability of repopulating a culture of human skin. Moreover, we demonstrated that the in vitro lipoaspirate paracrine effect on fibroblasts and keratinocytes proliferation, migration, and contraction rate is mediated by the release of trophic/reparative proteins. Finally, an analysis of the paracrine antibacterial effect of lipoaspirate proved its ability to secrete antibacterial factors and its ability to modulate their secretion in culture media based on a bacterial stimulus. The results suggest that lipoaspirate may be a promising approach in wound healing showing in vitro regenerative and antibacterial activities that could improve current therapeutic strategies.

Evolutionary conservation of leptin effects on wound healing in vertebrates: Implications for veterinary medicine

In mammals, the cytokine hormone leptin promotes wound healing by increasing inflammation, cellular recruitment, angiogenic regrowth, and re-epithelialization; however, it is not known whether leptin has conserved actions on wound healing in other vertebrates. Here, we tested the hypothesis that leptin promotes both the quality and speed of wound healing in the South African clawed frog, Xenopus laevis. First, fluorescent immunohistochemistry using a polyclonal antibody specific to Xenopus leptin showed that in juvenile dorsal skin, leptin protein is expressed in the dorsal epidermal layer, as well in blood vessel endothelial cells and sensory nerves that run along the base of the dermis. Injection of recombinant Xenopus leptin (rXleptin) stimulates phosphorylated STAT3 (pSTAT3), indicative of leptin-activated JAK/STAT signaling in the epidermis. Similar to mammals, leptin protein expression increases at the wound site after injury of the epidermis. We then cultured "punch-in-a-punch" full-thickness dorsal skin explants in three doses of rXleptin (0, 10, and 100 ng/ml) and showed that leptin treatment doubled the rate of wound closure after 48 h relative to skin punches cultured without leptin. Food restriction prior to wound explant culture reduced the amount of wound closure, but leptin injection prior to euthanasia rescued closure to similar control levels. Leptin treatment also significantly reduced bacterial infection of these epidermal punches by 48 h in culture. This study shows that leptin is likely an endogenous promoter of wound healing in amphibians. Leptin-based therapies have the potential to expedite healing and reduce the incidence of secondary infections without toxicity issues, the threat of antibiotic resistance, or environmental antibiotic contamination. The conservation of leptin's actions on wound healing also suggests that it may have similar veterinary applications for other exotic species.

"Feeding the Foot": Nutritional Influences on Equine Hoof Health

Nutrition plays an important role in equine health, including that of the foot. Deficiencies and excesses of dietary components can affect the growth and function of the foot and have been associated with important podiatric diseases. The recognition, prevention, and treatment of specific notable nutritional diseases of the foot are discussed, as well as information regarding specific ingredients included in supplements meant to improve equine hoof quality. Ensuring provision of a balanced diet, maintaining horses in appropriate body condition, and seeking guidance from an equine nutritionist when creating dietary recommendations will prevent most equine foot disease related to nutrition.

Leptin-Activity Modulators and Their Potential Pharmaceutical Applications

Leptin, a multifunctional hormone primarily, but not exclusively, secreted in adipose tissue, is implicated in a wide range of biological functions that control different processes, such as the regulation of body weight and energy expenditure, reproductive function, immune response, and bone metabolism. In addition, leptin can exert angiogenic and mitogenic actions in peripheral organs. Leptin biological activities are greatly related to its interaction with the leptin receptor. Both leptin excess and leptin deficiency, as well as leptin resistance, are correlated with different human pathologies, such as autoimmune diseases and cancers, making leptin and leptin receptor important drug targets. The development of leptin signaling modulators represents a promising strategy for the treatment of cancers and other leptin-related diseases. In the present manuscript, we provide an update review about leptin-activity modulators, comprising leptin mutants, peptide-based leptin modulators, as well as leptin and leptin receptor specific monoclonal antibodies and nanobodies.

Association of Leptin Receptor Gene Polymorphisms with Keloids in the Chinese Han Population

Background

The association between leptin receptor (LEPR) polymorphisms and keloids is still unclear. Our study aimed to explore the association between LEPR gene polymorphisms and keloids in the Chinese Han population.

Material/Methods

We implemented a case-control study in a cohort of 352 keloid patients and 299 healthy controls to analyze the correlation between 4 SNPs (rs1137101, rs1938496, rs6588147, and rs7555955) and keloids. Genomic DNA was extracted from peripheral blood by using TGuide M16 (Tiangen). Genotyping of LEPR SNPs was performed using an improved multiple ligase detection reaction (iMLDR) by Shanghai Genesky Bio-Tech Co., Ltd.

Results

We found that patients caring the AA genotype of rs1137101 and the CC genotype rs1938496 tend to have the increased risk of keloids (P=0.026, P=0.047). Carrying the GA, AA gene type, and G allele frequencies of rs7555955, patients were more likely to have to keloids (P=0.030, P=0.016, P=0.018, respectively). There were no significant differences in genotype distribution and allele frequencies of rs6588147 between cases and controls. The association of rs1137101 and rs7555955 under dominant, recessive, and allele models exhibited significant differences among family-history keloid patients, no-family-history keloid groups, and normal controls (χ²=6.471, P=0.039; χ²=6.477, P=0.039; χ²=6.197, P=0.045, respectively). Similarly, the OR of rs1137101 in the recessive model was significantly higher in patients with a family history of keloids than those in controls. Nonetheless, there are significant ORs of rs1938496 and rs6588147 among the mild-moderate keloid, severe keloid, and control groups.

Conclusions

The LEPR gene polymorphisms are associated with keloid formation and severity, especially in patients with a positive family history.

The Important Role of Leptin in Modulating the Risk of Dermatological Diseases

It is an indisputable fact that obesity is associated with a series of health problems. One important hallmark of obesity is excessive accumulation of lipids in the adipocyte, especially triglyceride (TG). Currently, the adipocyte has been considered not only as a huge repository of excess energy in the form of fat but also as an important source of multiple hormones and cytokines called adipokines. In obesity, the adipocyte is dysfunctional with excessive production and secretion of pro-inflammatory adipokines, such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and leptin. On the other hand, accumulating evidence has shown that leptin plays a vital role in stimulating angiogenesis, controlling lipid metabolism, and modulating the production of pro-inflammatory cytokines. Furthermore, the various activities of leptin are related to the wide distribution of leptin receptors. Notably, it has been reported that enhanced leptin levels and dysfunction of the leptin signaling pathway can influence diverse skin diseases. Recently, several studies revealed the roles of leptin in wound healing, the hair cycle, and the pathogenic development of skin diseases, such as psoriasis, lupus erythematosus, and dermatological cancers. However, the exact mechanisms of leptin in modulating the dermatological diseases are still under investigation. Therefore, in the present review, we summarized the regulatory roles of leptin in the pathological progression of diverse diseases of skin and skin appendages. Furthermore, we also provided evidence to elucidate the complicated relationship between leptin and different dermatological diseases, such as systemic lupus erythematosus (SLE), psoriasis, hidradenitis suppurativa, and some skin tumors.

Leptin in skin disease modulation

In obesity, adipocytes are dysfunctional with excessive production and secretion of pro-inflammatory hormones and cytokines, ie, adipokines, such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and leptin. Accumulating evidence has shown that leptin possesses pleiotropic functions including stimulation of angiogenesis and production of pro-inflammatory cytokines. Furthermore, various leptin associated activities involve a wide distribution of leptin receptors. For example, increased serum leptin was associated with tissue receptor resistance in metabolic syndrome. Although increased serum leptin, receptor and signaling impairment are involved in wound healing, hair cycle and the pathogenesis of many skin diseases such as psoriasis and lupus erythematosus as well as skin cancer, its exact role remains unclear. In the present article, we discuss the biochemistry of leptin action and its potential role in the pathophysiology of diverse skin diseases.

A novel human ex vivo skin model to study early local responses to burn injuries

Burn injuries initiate numerous processes such as heat shock response, inflammation and tissue regeneration. Reliable burn models are needed to elucidate the exact sequence of local events to be able to better predict when local inflammation triggers systemic inflammatory processes. In contrast to other ex vivo skin culture approaches, we used fresh abdominal skin explants to introduce contact burn injuries. Histological and ultrastructural analyses confirmed a partial-thickness burn pathology. Gene expression patterns and cytokine production profiles of key mediators of the local inflammation, heat shock response, and tissue regeneration were analyzed for 24 h after burn injury. We found significantly increased expression of factors involved in tissue regeneration and inflammation soon after burn injury. To investigate purely inflammation-mediated reactions we injected lipopolysaccharide into the dermis. In comparison to burn injury, lipopolysaccharide injection initiated an inflammatory response while expression patterns of heat shock and tissue regeneration genes were unaffected for the duration of the experiment. This novel ex vivo human skin model is suitable to study the local, early responses to skin injuries such as burns while maintaining an intact overall tissue structure and it gives valuable insights into local mechanisms at the very beginning of the wound healing process after burn injuries.

Leptin System in Obese Dog Skin: A Pilot Study

Simple Summary

Obesity is a widespread phenomenon in pets and its growing trend is similar to the human one. It can be associated with skin pathologies but there is little information on this field in domestic animals. Since in obesity adipokine plasmatic levels changes, in this study leptin (LEP) system was evaluated in the skin of obese dogs to observe changes in peripheral tissue. LEP is a hormone produced mainly by the adipose tissue and its serum level may reflect body mass index and BCS. LEP is also expressed in the skin and it has a prominent role in the biology of this tissue promoting cell proliferation and regulating the wound healing process. Investigation performed in obese and normal-weight dogs evidenced LEP and leptin receptor (LEPR) immunostaining in several skin structures. As LEP expression regards, differences were non-significant, while the LEPR transcripts appeared 10 fold higher in obesedogs. No differences were observed in the composition of skin associated immune system. The obese group-increased LEPR expression suggests that the receptor modulates the system control. The LEP system changes in the skin under obesity conditions however, the exact role of LEP in obese dog skin needs further insights.

Abstract

Obesity predisposes to several health problems including skin diseases. However, information on the relationship between obesity and skin disorders in pets is very scarce. Leptin (LEP) is mainly produced by adipose tissue and has a prominent role in skin biology. This study evaluated the LEP system in the skin of obese dogs compared to normal-weight animals. The investigation was carried out on 10 obese (Obese group) and 10 normal-weight (Normal-weight group) dogs through Real-time PCR and immunohistochemistry. Cells of skin associated immune system were also evaluated. No differences were evidenced between the two groups as well as skin inflammation. LEP differences were no significant, while LEPR transcript appeared 10-fold higher in obesedogs than in normal-weight ones. Immunostaining for both molecules was observed in several skin structures such as the epidermis, hair follicles, and glands. No differences appeared in the skin associated immune system composition. This study is a preliminary report showing that LEP system changes in obese dog skin. The increased LEPR expression observed in the obese group suggests that the receptor plays a modulating role in the system control. However, the exact role of LEPin the skin under obesity conditions needs further elucidation.

Adipokines in the Skin and in Dermatological Diseases

Adipokines are the primary mediators of adipose tissue-induced and regulated systemic inflammatory diseases; however, recent findings revealed that serum levels of various adipokines correlate also with the onset and the severity of dermatological diseases. Importantly, further data confirmed that the skin serves not only as a target for adipokine signaling, but may serve as a source too. In this review, we aim to provide a complex overview on how adipokines may integrate into the (patho) physiological conditions of the skin by introducing the cell types, such as keratinocytes, fibroblasts, and sebocytes, which are known to produce adipokines as well as the signals that target them. Moreover, we discuss data from in vivo and in vitro murine and human studies as well as genetic data on how adipokines may contribute to various aspects of the homeostasis of the skin, e.g., melanogenesis, hair growth, or wound healing, just as to the pathogenesis of dermatological diseases such as psoriasis, atopic dermatitis, acne, rosacea, and melanoma.

The effects of obesity on the human body, part I: Skin and musculoskeletal

Obesity is a worldwide issue that many global health authorities consider a growing epidemic. Having a positive correlation between increases in the industrialization of processed foods and sedentary occupations as well as a lack of access to healthcare in poorer socioeconomic areas, obesity is a multifactorial disease affecting several organ systems. The tendency for obesity to cause detrimental changes to the human body is a focal point for healthcare providers to establish more effective clinical treatment and management plans. Implementing comprehensive global educational programs to decrease the prevalence of this unforgiving disease is imperative for a healthier future. Herein, we have provided a comprehensive review of the health effects of obesity upon the human body for the interest of many practicing clinicians managing this health crisis.

The role of leptin in selected skin diseases

Leptin is an adipokine, adipocyte-derived compound, which acts both as a hormone and cytokine. It is mainly synthesized by adipocytes of white adipose tissue. Leptin possesses pleiotropic functions including, among others, stimulation of angiogenesis and production of proinflammatory cytokines. The various types of leptin activity are related to the wide distribution of leptin receptors. This adipokine acts by activating intracellular signaling cascades such as JAKs (Janus kinases), STATs (signal transducers and activators of transcription), and others.In a course of obesity, an increased serum level of leptin coexists with tissue receptor resistance. It has been reported that enhanced leptin levels, leptin receptor impairment, and dysfunction of leptin signaling can influence skin and hair. The previous studies revealed the role of leptin in wound healing, hair cycle, and pathogenesis of skin diseases like psoriasis, lupus erythematosus, and skin cancers. However, the exact mechanism of leptin's impact on the skin is still under investigation. Herein, we present the current knowledge concerning the role of leptin in psoriasis and selected skin diseases.

Deciphering the functional heterogeneity of skin fibroblasts using single-cell RNA sequencing

Though skin fibroblasts (FB) are the main cell population within the dermis, the different skin FB subsets are not well characterized and the traditional classification into reticular and papillary FBs has little functional relevance. To fill the gap of knowledge on FB diversity in human skin, we performed single-cell RNA sequencing. Investigation of marker genes for the different skin cell subtypes revealed a heterogeneous picture of FBs. When mapping reticular and papillary FB markers, we could not detect cluster specificity, suggesting that these two populations show a higher transcriptional heterogeneity than expected. This finding was further confirmed by in situ hybridization, showing that DPP4 was expressed in both dermal layers. Our analysis identified six FB clusters with distinct transcriptional signatures. Importantly, we could demonstrate that in human skin DPP4⁺ FBs are the main producers of factors involved in extracellular matrix (ECM) assembly. In conclusion, we provide evidence that hitherto considered FB markers are not ideal to characterize skin FB subpopulations in single-cell sequencing analyses. The identification of DPP4⁺ FBs as the main ECM-producing cells in human skin will foster the development of anti-fibrotic treatments for the skin and other organs.

Endocrine Regulation of Epimorphic Regeneration

Studies aiming to uncover primary mechanisms of regeneration have predominantly focused on genetic pathways regulating specific stages in the regeneration process: wound healing, blastema formation, and pattern formation. However, studies across organisms show that environmental conditions and the physiological state of the animal can affect the rate or quality of regeneration, and endocrine signals are likely the mediators of these effects. Endocrine signals acting directly on receptors expressed in the tissue or via neuroendocrine pathways can affect regeneration by regulating the immune response to injury, allocation of energetic resources, or by enhancing or inhibiting proliferation and differentiation pathways involved in regeneration. This review discusses the cumulative knowledge in the literature about endocrine regulation of regeneration and its importance in future research to advance biomedical research.

Endocrine regulation of regeneration: Linking global signals to local processes

Regeneration in amphibians and reptiles has been explored since the early 18th century, giving us a working in vivo model to study epimorphic regeneration in vertebrates. Studies aiming to uncover primary mechanisms of regeneration have predominantly focused on genetic pathways regulating specific stages of the regeneration process: wound healing, blastema formation and growth, and pattern formation. However, studies across organisms show that environmental conditions and physiological state of the animal can affect the rate or quality of regeneration, and endocrine signals are likely the mediators of these effects. Endocrine signals working/acting directly on receptors expressed in the structure or via neuroendocrine pathways can affect regeneration by modulating immune response to injury, allocation of energetic resources, or by enhancing or inhibiting proliferation and differentiation pathways in regenerating tissue. This review discusses the cumulative knowledge known about endocrine regulation of regeneration and important future research directions of interest to both ecological and biomedical research.

Functional Relationship between Leptin and Nitric Oxide in Metabolism

Leptin, the product of the ob gene, was originally described as a satiety factor, playing a crucial role in the control of body weight. Nevertheless, the wide distribution of leptin receptors in peripheral tissues supports that leptin exerts pleiotropic biological effects, consisting of the modulation of numerous processes including thermogenesis, reproduction, angiogenesis, hematopoiesis, osteogenesis, neuroendocrine, and immune functions as well as arterial pressure control. Nitric oxide (NO) is a free radical synthesized from L-arginine by the action of the NO synthase (NOS) enzyme. Three NOS isoforms have been identified: the neuronal NOS (nNOS) and endothelial NOS (eNOS) constitutive isoforms, and the inducible NOS (iNOS). NO mediates multiple biological effects in a variety of physiological systems such as energy balance, blood pressure, reproduction, immune response, or reproduction. Leptin and NO on their own participate in multiple common physiological processes, with a functional relationship between both factors having been identified. The present review describes the functional relationship between leptin and NO in different physiological processes.

Epithelial expression of the hormone leptin by bovine skin

Leptin (Lep) stimulates keratinocytes to proliferate, intervenes in the wound healing and participates to hair follicle morphogenesis and cycle. While it is secreted by skin structures including epidermis and hair follicles, intradermal adipose tissue also seems to have a role in Lep secretion and accordingly in the control of hair follicle growth in mice and humans. Lep was investigated in the skin of humans and laboratory animals but there are not data regarding bovine species. The aim of this work was to study the expression of Lep and its receptor (LepR) in the skin of bovine and, at the same time, to investigate the presence and extension of intradermal adipose tissue. A morphological evaluation of the skin was performed while the presence and localization of Lep and LepR were analyzed by RT-PCR and immunohistochemistry. A high and thick dermis without adipocytes was observed. Hair follicles and sebaceous and sweat glands were located in the proximal part of the skin while a thick layer of connective tissue, lacking adipose cells, separated these structures by subcutis. RT-PCR evidenced the transcripts for both molecules. By immunohistochemistry, Lep and LepR were observed in the epidermis and hair follicles. Based on the absence of intradermal adipose tissue and the presence of both Lep and LepR in the epidermis and in the hair follicle epithelium, it can be posited that in bovine skin Lep participates to the control of epidermis growth and hair follicle cycle through a paracrine and autocrine mechanisms.

Characterization of thoracal fat depots - expression of adipokines and remodeling factors and impact of adipocyte conditioned media in fibroblast scratch assays

Adipose tissue is not only a connective tissue but also an endocrine organ secreting adipokines like Leptin and Adiponectin, lipokines such as palmitoileic acid and extracellular vesicles. These factors and the expression of matrix remodeling enzymes impact surrounding tissues via paracrine effects. The expression of selected secretion factors and the effect of adipocyte conditioned media from four thoracal adipose tissue origins - subcutaneous, perivascular, pericardial and epicardial adipose tissues - in a fibroblast proliferation/wound healing scratch assay model were investigated. Results were compared directly and according to the type 2 diabetic mellitus (T2DM) status of the patients the tissues are originated from. Adipocyte conditioned media from non-diabetic patients resulted in a significant higher scratch closure rate compared to the media with T2DM background. Linoleic acid incubation in scratch assay resulted in a reduced scratch closure rate. Leptin, Adiponectin and Visfatin/Nampt expression and MMP2, MMP9 and FSTL1 mRNA levels did not vary according to T2DM subgroups directly, leading to the assumption that these factors are not causal for scratch assay effects observed. In contrast significant mRNA expression differences were monitored between the thoracal tissue origins implying variations in the local effects of the different adipose tissue depots.

Are hair follicle stem cells promising candidates for wound healing?

INTRODUCTION

With the continued focus on in-depth investigations of hair follicle stem cells (HFSCs), the role of HFSCs in wound healing has attracted increasing attention from researchers. This review may afford meaningful implications for HFSC treatment of wounds.

AREAS COVERED

We present the properties of HFSCs, analyze the possibility of HFSCs in wound healing, and sum up the recent studies into wound repair with HFSCs. The details of HFSCs in wound healing have been discussed. The possible mechanisms of wound healing with HFSCs have been elaborated. Additionally, the factors that influence HFSCs in wound healing are also summarized.

EXPERT OPINION

Hair follicle stem cells are promising sources for wound healing. However, a further understanding of human HFSCs and the safety use of HFSCs in clinical practice still remain in relative infancy.

Expression of Three Adipokines (Adiponectin, Leptin and Resistin) in Normal Canine Skin: a Pilot Study

Adipokines are biologically active cytokines that are mainly produced in adipose tissue. There is evidence, in man and mice, that some adipokines may be secreted in other tissues including the vascular endothelium, epithelia and sebaceous glands. Moreover, modified serum levels of adipokines have been detected in people with acne vulgaris or psoriasis; it is suspected that adipokines could contribute to local and systemic inflammatory conditions. We aimed to evaluate the expression of three adipokines (i.e. leptin, adiponectin and resistin) in normal canine skin. Formalin-fixed, paraffin wax-embedded punch biopsy samples were obtained from the sparsely-haired skin of the caudal ventral abdomen of a single clinically healthy dog with no history of skin disease. Immunohistochemistry was applied, using rabbit polyclonal primary antibodies specific for leptin, adiponectin and resistin. Adipokines were not expressed in normal canine dermis or hypodermis. In contrast, they were detected in the keratinocytes of all epidermal layers and hair follicle segments, sebocytes, apocrine gland cells and in the vascular endothelium. This is the first report on the expression of adipokines in normal canine skin, a first step in studying their role in the skin physiology and inflammatory skin diseases of dogs.

Prevalence and clinicopathological characteristics of lipomatous neurofibromas in neurofibromatosis 1: An investigation of 229 cutaneous neurofibromas and a systematic review of the literature

BACKGROUND

Lipomatous neurofibroma (Lnf) is a histopathological variant with adipocytes noted among cells of cutaneous neurofibromas. We aimed to investigate the prevalence and clinicopathological features of Lnfs of neurofibromatosis 1 (NF1)-associated cutaneous neurofibromas and to review the literature systematically. We also evaluated the expression of leptin (a hormone involved in lipid metabolism) in neurofibromas to better understand the pathogenesis of Lnfs.

METHODS

A prospective histologic study was conducted on 229 cutaneous neurofibromas from 85 NF1 individuals. Leptin expression was immunohistochemically evaluated in 111 cutaneous neurofibromas. To systematically review the literature, two authors independently performed literature searches without year restriction.

RESULTS

Forty (17.5%) neurofibromas were lipomatous. Lnfs were significantly larger lesions and associated with females. Eighteen (7.9%) of all neurofibromas had multinucleated floret-like giant cells, and these were associated with Lnfs. All neurofibromas expressed leptin. We systematically reviewed 13 articles. Three large studies investigated Lnfs mainly in sporadic neurofibromas and suggested that 0.3% to 8.0% of tumors (NF1 and sporadic) are Lnfs.

CONCLUSION

In NF1, Lnfs are common, mainly in larger tumors and women. All cutaneous NF1-neurofibromas express leptin. It is unknown if the expression of leptin accounts for the lipomatous variant, but it may have a role in the pathogenesis of cutaneous neurofibroma.

Leptin regulates the pro-inflammatory response in human epidermal keratinocytes

The role of leptin in cutaneous wound healing process has been suggested in genetically obese mouse studies. However, the molecular and cellular effects of leptin on human epidermal keratinocytes are still unclear. In this study, the whole-genome-scale microarray analysis was performed to elucidate the effect of leptin on epidermal keratinocyte functions. In the leptin-treated normal human keratinocytes (NHKs), we identified the 151 upregulated and 53 downregulated differentially expressed genes (DEGs). The gene ontology (GO) enrichment analysis with the leptin-induced DEGs suggests that leptin regulates NHKs to promote pro-inflammatory responses, extracellular matrix organization, and angiogenesis. Among the DEGs, the protein expression of IL-8, MMP-1, fibronectin, and S100A7, which play roles in which is important in the regulation of cutaneous inflammation, was confirmed in the leptin-treated NHKs. The upregulation of the leptin-induced proteins is mainly regulated by the STAT3 signaling pathway in NHKs. Among the downregulated DEGs, the protein expression of nucleosome assembly-associated centromere protein A (CENPA) and CENPM was confirmed in the leptin-treated NHKs. However, the expression of CENPA and CENPM was not coupled with those of other chromosome passenger complex like Aurora A kinase, INCENP, and survivin. In cell growth kinetics analysis, leptin had no significant effect on the cell growth curves of NHKs in the normal growth factor-enriched condition. Therefore, leptin-dependent downregulation of CENPA and CENPM in NHKs may not be directly associated with mitotic regulation during inflammation.

The Effects of Adipose-Derived Stem Cell-Differentiated Adipocytes on Skin Burn Wound Healing in Rats

Both adipose-derived stem cells (ADSCs) and fat grafting promote burn wound healing, but whether adipogen-derived cells using various inducers such as 3-isobutyl-1-methylxanthine (IBMX) and insulin affect wound healing is unknown. Herein, ADSC-differentiated adipogenic lineages were used in rat burn wounds to evaluate wound healing potential. ADSCs were cultivated using six different adipogenic differentiation conditions (IBMX ± insulin, IBMX for 5 days, high and low Dulbecco's modified Eagle's medium) and in vitro morphological changes and cell proliferations during adipogenic differentiation were recorded. Intermediate burn wounds were inflicted in 15 Wistar male rats. Afterwards, the rats were divided into five groups for subcutaneous injections under the wounds: control; ADSCs; differentiated adipocytes (-IBMX+INSULIN and +IBMX[D1-5]+INSULIN) and fat prepared by Coleman technique. Macroscopic changes and histology were documented for 3 weeks. Repeated measures analysis of variance was performed to analyze cell growth and wound healing with a statistical level set of P < .05. Induction cocktails significantly reduced proliferation and induced lipid droplet accumulation. Conditioning without insulin induced the least lipid accumulation, while discontinuing IBMX generated larger adipocytes (P < .001). Adipogenic differentiated ADSCs had similar wound healing abilities with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerated the early healing process relative to ADSC (P < .001). Reduced fibrosis and mild inflammatory infiltration limited to superficial dermis were observed in +IBMX(D1-5)+INSULIN and fat injection groups, while those reactions were mild to moderate in ADSC group. Differentiated adipocytes achieve similar wound healing results compared with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerate early healing relative to ADSC.

Angiotensin-(1-7) protects cardiomyocytes against high glucose-induced injuries through inhibiting reactive oxygen species-activated leptin-p38 mitogen-activated protein kinase/extracellular signal-regulated protein kinase 1/2 pathways, but not the leptin-c-Jun N-terminal kinase pathway in vitro

Aims/Introduction

Angiotensin‐(1–7) (Ang‐[1–7]), recognized as a new bioactive peptide in the renin–angiotensin system, shows biological and pharmacological properties in diabetic cardiovascular diseases. The leptin‐induced p38 mitogen‐activated protein kinase (MAPK) pathway has been reported to contribute to high glucose (HG)‐induced injury. In the present study, we showed the mechanism of how Ang‐(1–7) can protect against HG‐stimulated injuries in H9c2 cells.

Materials and Methods

H9c2 cells were treated with 35 mmol/L glucose (HG) for 24 h to establish a model of HG‐induced damage. Apoptotic cells were observed by Hoechst 33258 staining. Cell viability was analyzed by cell counter kit‐8. The expression of protein was detected by western blot. Reactive oxygen species was tested by 2′,7′‐dichlorodihydrofluorescein diacetate staining. Mitochondrial membrane potential was measured by 5,5′,6,6′‐Tetrachloro‐1,1′,3,3′‐tetraethyl‐imidacarbocyanine iodide staining.

Results

The present results showed that treating H9c2 cells with HG obviously enhanced the expressions of both the leptin and phosphorylated (p)‐MAPK pathway. However, the overexpression levels of leptin and p‐p38 MAPK/p‐extracellular signal‐regulated protein kinase 1/2 (ERK1/2), but not p‐c‐Jun N‐terminal kinase, were significantly suppressed by treatment of the cells with Ang‐(1–7). Additionally, leptin antagonist also markedly suppressed the overexpressions of p38 and ERK1/2 induced by HG, whereas leptin antagonist had no influence on the overexpression of c‐Jun N‐terminal kinase. More remarkable, Ang‐(1–7), leptin antagonist, SB203580 or SP600125, respectively, significantly inhibited the injuries induced by HG, such as the increased cell viability, decreased apoptotic rate, reduction of ROS production and increased mitochondrial membrane potential. Furthermore, the overexpressions of p38 MAPK, ERK1/2 and leptin were suppressed by N‐actyl‐L‐cystine.

Conclusions

The present findings show that Ang‐(1–7) protects from HG‐stimulated damage as an inhibitor of the reactive oxygen species–leptin–p38 MAPK/ERK1/2 pathways, but not the leptin–c‐Jun N‐terminal kinase pathway in vitro.

Vascular Endothelial Growth Factor A and Leptin Expression Associated with Ectopic Proliferation and Retinal Dysplasia in Zebrafish Optic Pathway Tumors

In the central nervous system injury induces cellular reprogramming and progenitor proliferation, but the molecular mechanisms that limit regeneration and prevent tumorigenesis are not completely understood. We previously described a zebrafish optic pathway tumor model in which transgenic Tg(flk1:RFP)is18/+ adults develop nonmalignant retinal tumors. Key pathways driving injury-induced glial reprogramming and regeneration contributed to tumor formation. In this study, we examine a time course of proliferation and present new analyses of the Tg(flk1:RFP)is18/+ dysplastic retina and tumor transcriptomes. Retinal dysplasia was first detected in 3-month-old adults, but was not limited to a specific stem cell or progenitor niche. Pathway analyses suggested a decrease in cellular respiration and increased expression of components of Hif1-α, VEGF, mTOR, NFκβ, and multiple interleukin pathways are associated with early retinal dysplasia. Hif-α targets VEGFA (vegfab) and Leptin (lepb) were both highly upregulated in dysplastic retina; however, each showed distinct expression patterns in neurons and glia, respectively. Phospho-S6 immunolabeling indicated that mTOR signaling is activated in multiple cell populations in wild-type retina and in the dysplastic retina and advanced tumor. Our results suggest that multiple pathways may contribute to the continuous proliferation of retinal progenitors and tumor growth in this optic pathway tumor model. Further investigation of these signaling pathways may yield insight into potential mechanisms to control the proliferative response during regeneration in the nervous system.

Electrospinning of Bioactive Wound-Healing Nets

The availability of appropriate dressings for treatment of wounds, in particular chronic wounds, is a task that still awaits better solutions than provided by currently applied materials. The method of electrospinning enables the fabrication of novel materials for wound dressings due to the high surface area and porosity of the electrospun meshes and the possibility to include bioactive ingredients. Recent results show that the incorporation of biologically active inorganic polyphosphate microparticles and microspheres and synergistically acting retinoids into electrospun polymer fibers yields biocompatible and antibacterial mats for potential dressings with improved wound-healing properties. The underlying principles and the mechanism of these new approaches in the therapy wounds, in particular wounds showing impaired healing, as well as for further applications in skin regeneration/repair, are summarized.

Immunohistochemical Evaluation of Leptin Expression in Wound Healing: A Clue to Exuberant Scar Formation

Leptin has been recognized as an important factor for promoting normal cutaneous wound healing. The aim of this work was to explore leptin expression in keloid and hypertrophic scars (HS) compared with surgical scars and normal skin. The relationship of this expression with clinicopathologic parameters of studied cases was also evaluated. Using immunohistochemical techniques, leptin was analyzed in skin biopsies of 60 nonobese subjects without metabolic syndrome who presented with keloids (20), HS (20), and surgical scars (20). Twenty normal skin samples, from age-matched, sex-matched, and body mass index-matched subjects, were enrolled as a control group. Leptin showed positive immunoreactivity in epidermis in all cases of surgical scars and keloids and in 75% of HS cases. Dermal expression in fibroblasts, inflammatory cells, and endothelial cells was positive in all cases of surgical scars and keloids and in 70% of HS cases. Leptin was overexpressed in keloids and HS compared with normal skin in epidermis (P<0.001 for both) and dermis (P<0.001 for both) and to surgical scars both in epidermis (P=0.0006, P=0.01, respectively) and dermis (P=0.0001, P=0.001, respectively). Higher leptin H score was significantly associated with older age (P=0.02) and positive family history (P=0.002) in keloid cases and with axial site in keloid and HS cases (P=0.001, P=0.02, respectively). Significant positive correlation was noted between epidermal and dermal leptin H scores in keloids (r=+0.37, P=0.04) and HS (r=+0.39, P=0.02). This may be due to epithelial-mesenchymal interactions in scar pathogenesis. In conclusion, in situ leptin overexpression may increase the possibility of keloid and HS occurrence through altered cytokine production and prolonged healing phases with excessive deposition and delayed collagen degradation. This may open an avenue for research for new therapeutic modalities based on its inhibition.

Immunohistochemical Expression of Leptin in Non Melanoma Skin Cancer

INTRODUCTION

Obesity in adults is associated with numerous health disorders including some forms of cancer. Various epidemiological studies have found a link between excess adiposity and malignant melanoma; however, the association with non melanoma skin cancer is questionable. Leptin is a hormone produced mainly by the adipose tissue and its serum level may reflect body mass index. Leptin is reported to promote proliferation and angiogenesis and deregulate apoptosis, therefore facilitates the process of carcinogenesis.

AIM

The current study tried to assess leptin localization and expression in non melanoma skin cancer to verify its possible role in pathogenesis of this cancer.

MATERIALS AND METHODS

This study was carried out on 13 Basal Cell Carcinoma (BCC) cases and 14 Squamous Cell Carcinoma (SCC) cases together with 19 normal skin biopsies as a control group using immunohistochemical method.

RESULTS

Leptin was expressed in 52.6% of the normal epidermis with pure cytoplasmic and both cytoplasmic and nuclear staining patterns. All cases of SCC (100%) and two cases of BCC (15.4%) showed leptin expression in tumour cells whereas nuclear expression was in favour of SCC. Stromal expression of leptin was seen in both SCC (57.1%) and BCC (38.5%) without significant differences. Percentage of leptin expression by tumour cells in SCC showed positive linear correlation with tumour size (p=0.02) and microvessel density (p=0.000). Stromal expression of leptin in SCC was associated with large tumour size (p=0.04), advanced stage (p=0.01) and tumours arising in sites other than head and neck (p=0.01).

CONCLUSION

Leptin could have a more important role in pathogenesis of cutaneous SCC rather than BCC that may reflect the trivial role of obesity in induction of BCC. The expression of leptin by tumour and stromal cells of SCC could co-operate in its progression by promoting angiogenesis with subsequently acquiring large tumour size and then advanced stage.

Compromised Wound Healing in Ischemic Type 2 Diabetic Rats

Ischemia is one of the main epidemic factors and characteristics of diabetic chronic wounds, and exerts a profound effect on wound healing. To explore the mechanism of and the cure for diabetic impaired wound healing, we established a type 2 diabetic rat model. We used an 8weeks high fat diet (HFD) feeding regimen followed by multiple injections of streptozotocin (STZ) at a dose of 10mg/kg to induce Wister rat to develop type 2 diabetes. Metabolic characteristics were assessed at the 5th week after the STZ injections to confirm the establishment of diabetes mellitus on the rodent model. A bipedicle flap, with length to width ratio 1.5, was performed on the back of the rat to make the flap area ischemic. Closure of excisional wounds on this bipedicle flap and related physiological and pathological changes were studied using histological, immunohistochemical, real time PCR and protein immunoblot approaches. Our results demonstrated that a combination of HFD feeding and a low dose of STZ is capable of inducing the rats to develop type 2 diabetes with noticeable insulin resistance, persistent hyperglycemia, moderate degree of insulinemia, as well as high serum cholesterol and high triglyceride levels. The excision wounds on the ischemic double pedicle flap showed deteriorative healing features comparing with non-ischemic diabetic wounds, including: delayed healing, exorbitant wound inflammatory response, excessive and prolonged ROS production and excessive production of MMPs. Our study suggested that HFD feeding combined with STZ injection could induce type 2 diabetes in rat. Our ischemic diabetic wound model is suitable for the investigation of human diabetic related wound repair; especically for diabetic chronic wounds.

Sebocytes differentially express and secrete adipokines

In addition to producing sebum, sebocytes link lipid metabolism with inflammation at a cellular level and hence, greatly resemble adipocytes. However, so far no analysis was performed to identify and characterize the adipocyte-associated inflammatory proteins, the members of the adipokine family in sebocytes. Therefore, we determined the expression profile of adipokines [adiponectin, interleukin (IL) 6, resistin, leptin, serpin E1, visfatin, apelin, chemerin, retinol-binding protein 4 (RBP4) and monocyte chemoattractant protein 1 (MCP1)] in sebaceous glands of healthy and various disease-affected (acne, rosacea, melanoma and psoriasis) skin samples. Sebaceous glands in all examined samples expressed adiponectin, IL6, resistin, leptin, serpin E1 and visfatin, but not apelin, chemerin, RBP4 and MCP1. Confirming the presence of the detected adipokines in the human SZ95 sebaceous gland cell line we further characterized their expression and secretion patterns under different stimuli mimicking bacterial invasion [by using Toll-like receptor (TLR)2 and 4 activators], or by 13-cis retinoic acid (13CRA; also known as isotretinoin), a key anti-acne agent. With the exception of resistin, the expression of all of the detected adipokines (adiponectin, IL6, leptin, serpin E1 and visfatin) could be further regulated at the level of gene expression, showing a close correlation with the secreted protein levels. Besides providing further evidence on similarities between adipocytes and sebocytes, our results strongly suggest that sebocytes are not simply targets of inflammation but may exhibit initiatory and modulatory roles in the inflammatory processes of the skin through the expression and secretion of adipokines.

Electrospun bioactive mats enriched with Ca-polyphosphate/retinol nanospheres as potential wound dressing

Background

While electrospun materials have been frequently used in tissue engineering no wound dressings exist that significantly improved wound healing effectively.

Methods

We succeeded to fabricate three-dimensional (3D) electrospun poly(D,l-lactide) (PLA) fiber mats into which nanospheres, formed from amorphous calcium polyphosphate (polyP) nanoparticles (NP) and encapsulated retinol (“retinol/aCa-polyP-NS” nanospheres [NS]), had been incorporated.

Results

Experiments with MC3T3-E1 cells revealed that co-incubation of the cells with Ca-polyP together with retinol (or incubation with retinol/aCa-polyP-NS) resulted in a significant synergistic effect on cell growth compared with particle-free polyP complexed with Ca²⁺ or amorphous Ca-polyP NPs and retinol alone. Incubation of the cells in the presence of the retinol/aCa-polyP NSs also caused a significant increase of the expression levels of the genes encoding for the fatty acid binding protein 4 (FABP4), as well as of the genes encoding for leptin and the leptin receptor. In contrast, the single components, soluble Na-polyP, complexed to Ca²⁺, or retinol-free aCa-polyP NPs, and retinol, had no significant effect on the expression of these genes.

Conclusions

These results indicate that the PLA fibers, supplemented with aCa-polyP-NP or retinol/aCa-polyP-NS, elicit morphogenetic activity, suggesting that these fiber mats, along with the antibacterial effect of polyP, have a beneficial potential as wound dressings combining antimicrobial and regenerative (wound healing) properties.

General significance

The PLA-based fiber mats, containing retinol and polyP nanoparticles, provide promising bioactive meshes that are urgently needed as dressings for chronic wounds.

• Effect of PLA fiber mats with polyphosphate/retinol nanospheres on gene expression.

• Increased expression of FABP4, leptin and leptin receptor in MC3T3-E1 cells.

• Application as wound dressings, combining antimicrobial and regenerative properties.

Enhancing repair of full-thickness excisional wounds in a murine model: Impact of tissue-engineered biological dressings featuring human differentiated adipocytes

Promotion of skin repair for acute or chronic wounds through the use of tissue-engineered products is an active field of research. This study evaluates the effects mediated by tissue-engineered biological dressings containing human in vitro-differentiated adipocytes and adipose-derived stromal cells (ASCs). Re-epithelialization, granulation tissue formation and neovascularization of full-thickness cutaneous wounds were specifically assessed using a murine model featuring a fluorescent epidermis. In comparison with wounds that did not receive an adipocyte-containing biological dressing, treated wounds displayed a slight but significantly faster wound closure based on macroscopic observations over 18 days. Non-invasive imaging of GFP-expressing keratinocytes determined that the kinetics of re-epithelialization were similar for both groups. Treated wounds featured thicker granulation tissues (1.7-fold, P < 0.0001) enriched in collagens (1.3-fold, P < 0.0104). In addition, wound cryosections labeled for detection of CD31-expressing cells indicated a 2.2-fold (P < 0.0002) increased neovascularization for the treated wounds at the time of terminal biopsy. This is in accordance with the secretion of pro-angiogenic factors detected in media conditioned by the dressings. Taken together, these results establish that a new type of engineered substitutes featuring a mixture of adipocytes and ASCs can promote cutaneous healing when applied as temporary dressings, suggesting their potential relevance for chronic wound management studies.

Leptin promotes wound healing in the skin

INTRODUCTION

Leptin, a 16 kDa anti-obesity hormone, exhibits various physiological properties. Interestingly, skin wound healing was proven to delay in leptin-deficient ob/ob mice. However, little is known on the mechanisms of this phenomenon. In this study, we attempted to elucidate a role of leptin in wound healing of skin.

METHODS

Immunohistochemical analysis was performed to confirm the expression of the leptin receptor (Ob-R) in human and mouse skin. Leptin was topically administered to chemical wounds created in mouse back skin along with sustained-release absorbable hydrogel. The process of wound repair was histologically observed and the area of ulceration was measured over time. The effect of leptin on the proliferation, differentiation and migration of human epidermal keratinocytes was investigated.

RESULTS

Ob-R was expressed in epidermal cells of human and mouse skin. Topical administration of leptin significantly promoted wound healing. Histological analysis showed more blood vessels in the dermal connective tissues in the leptin-treated group. The proliferation, differentiation/function and migration of human epidermal keratinocytes were enhanced by exogenous leptin.

CONCLUSION

Topically administered leptin was proven to promote wound healing in the skin by accelerating proliferation, differentiation/function and migration of epidermal keratinocytes and enhancing angiogenesis around the wounded area. These results strongly suggest that topical administration of leptin may be useful as a treatment to promote wound healing in the skin.

The mRNA expressions and immunohistochemistry of factors involved in angiogenesis and lymphangiogenesis in the early stage of rat skin incision wounds

Wound healing evaluation is important in forensic pathology, in which angiogenesis plays an important role. We have already shown that vascular endothelial growth factor A (VEGF) is produced in the rat skin incision wounds by neutrophils, endothelial cells, and fibroblasts. In this study, we assessed the changes in the mRNA expressions of various factors possibly involved in angiogenesis including angiopoietin (ANGPT) 1 and 2, cadherin 5 (CDH5), granulocyte-macrophage colony stimulating factor (CSF2/GM-CSF), granulocyte colony stimulating factor (CSF3/G-CSF), chemokine (C-X-C motif) ligand 2 (CXCL2), chemokine (C-X-C motif) ligand12 (CXCL12/SDF1), endothelin 1 (ET1), fibroblast growth factor 1 (FGF 1), hepatocyte growth factor (HGF), hypoxia inducible factor 1 alpha (HIF1a), leptin, matrix metallopepitidase 9 (MMP9), serpine/plasminogen activator inhibitor1 (PAI1), platelet-derived growth factor-A (PDGF-A), transforming growth factor alpha and beta 1 (TGFa and b1), tenomodulin (TNMD), and troponin I type 2 (TNNI2) in the early stage of the rat skin incision wounds by real time RT-PCR. Factors reported to be involved in lymphangiogenesis such as fibroblast growth factor 2 (FGF 2), c-fos induced growth factor (FIGF/VEGF-D), forkhead box C2 (FOXC2), and prospero homeobox 1 (PROX1) were also studied. One and 3 days after the dorsal skin incisions, wounds on male Sprague-Dawley rats showed the statistically significant increases in the mRNA expressions for CXCL2, CSF3, MMP9, PAI1, and CSF2, whereas TGFa, TNNI2, FGF1, TNMD, leptin, and CXCL12 showed the statistically significant decreases. Interestingly, lymphgangiogenic factors FOXC2, PROX1, and FGF2 also showed the statistically significant decreases. In situ hybridization and immunohistochemistry showed the mRNA and protein positivity in endothelial cells, fibroblasts, and some leukocytes at the bottom of the wound tissue for PAI1, CSF3, and MMP9, 1 day after the skin incisions. Our novel findings show the possible involvement of several factors involved in angiogenesis and lymphangiogenesis in the early stage of wound healing process, which may be useful for forensic wound evaluations.

Leptin controls hair follicle cycling

Leptin is a cytokine well known for its ability to control body weight and energy metabolism. Several lines of evidence have recently revealed that leptin also plays an important role in wound healing and immune modulation in skin. Sumikawa et al. Exp Dermatol 2014 evaluated the effect of leptin on hair follicle cycling using mutant and wild-type mice. They report that leptin is produced in dermal papilla cells in hair follicles and that leptin receptor-deficient db/db mice show an abnormality in hair follicle cycling. Moreover, leptin injection induced the transition into the growth stage of the hair cycle (anagen). On this basis, it now deserves exploration whether leptin-mediated signalling is a key stimulus for anagen induction and whether this may be targeted to manage human hair disorders with defect in the control of hair follicle cycling.

Molecular regulation of the expression of leptin by hypoxia in human coronary artery smooth muscle cells

Background

Leptin, produced mainly by white adipose tissue, is a hormone that promotes vascular smooth muscle cell (VSMC) migration and proliferation, a process involved in the pathophysiology of atherosclerosis. Leptin expression in human coronary artery smooth cell (HCASMC) is induced by hypoxia. However, our understanding of the process of atherosclerosis in HCASMC is only emerging. Since the mechanisms by which hypoxia regulates leptin in HCASMC are as yet unknown, this study aims to investigate the mechanics of molecular regulation of leptin expression in HCASMC under hypoxia. We subjected cultured HCASMCs to hypoxia for varying periods of time. Through use of different signal pathway inhibitors, we were able to sort out and identify the pathway through which hypoxia-induced leptin expression occurs.

Results

Leptin mRNA and protein levels increased after 2.5% hypoxia for 2-to-4 hours, with earlier expression of angiotensin II (AngII) and reactive oxygen species (ROS). The addition before hypoxia of the c-Jun N-terminal kinase (JNK) pathway inhibitor (SP600125), JNK small interfering RNA (siRNA), AngII receptor blockers (ARBs; losartan), or N-acetyl-L-cysteine (NAC, an ROS scavenger), had the effect of inhibiting JNK phosphorylation and leptin expression. Gel shift assay and luciferase promoter study showed that leptin/activator protein 1 (AP-1) binding and transcriptional activity to the leptin promoter increased after hypoxia, and SP600125, JNK siRNA, losartan, and NAC abolished the binding and transcriptional activity induced by hypoxia. The use of SP600125, JNK siRNA, losartan, and NAC effectively inhibited the binding and transcriptional activity induced by hypoxia. Migration and proliferation, ROS generation, and the presence of leptin in the nuclei of HCASMCs also increased under hypoxia.

Conclusion

Hypoxia in HCASMCs increases leptin expression through the induction of AngII, ROS, and the JNK pathway to enhance atherosclerosis in HCASMCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-014-0109-8) contains supplementary material, which is available to authorized users.

Leptin receptor is expressed by epidermis and skin appendages in dog

Leptin is a polypeptide secreted by adipocytes which binds to a specific receptor (Ob-R) that is expressed in various tissues. The wide distribution of the Ob-R suggests that leptin might exert diverse biological functions, not only by regulating energy metabolism and appetite, but also by acting as a mitogen in many cell types, including keratinocytes. In this study, the presence and localization of Ob-R was investigated in the skin of the dog using RT-PCR and immunohistochemical techniques. RT-PCR revealed the presence of Ob-R m-RNA in the skin specimens collected from the dorsal region of two smooth coat breed dogs. Through immunohistochemistry performed on the skin of five dogs, the expression of the receptor was observed in the basal layer of the epidermis, in the hair follicles as well as in the apocrine sweat and sebaceous glands. No staining for Ob-R was detected in the suprabasal epidermis layers. Strong positive signals were observed in many cells of the outer root sheath of hair follicles in growing and in regressive phases. The identification of Ob-R in the above targets suggests that leptin may play a role in the regulation of cyclic renewal of the epidermis and skin appendages in dog. This study represents an important contribution to understand the complex mechanisms that are involved in the skin biology in this species.

Hair cycle control by leptin as a new anagen inducer

Our purpose is to clarify the physiological role of leptin in hair cycle as leptin reportedly causes activation of Stat3, which is indispensable for hair cycling. While hair follicles in dorsal skin of 5-week-old C57/BL6 mice had progressed to late anagen phase, those in dorsal skin of 5-week-old leptin receptor deficient db/db mice remained in the first telogen and later entered the anagen at postnatal day 40, indicating that deficiency in leptin receptor signalling delayed the second hair cycle progression. Next, we shaved dorsal hairs on wild-type mice at postnatal 7 weeks and injected skin with mouse leptin or a mock. After 20 days, although mock injection showed no effect, hair growth occurred around leptin injection area. Human leptin fragment (aa22-56) had similar effects. Although the hair cycle of ob/ob mice was similar to that of wild-type mice, injection of mouse leptin on ob/ob mice at postnatal 7 weeks induced anagen transition. Immunohistochemically, leptin is expressed in hair follicles from catagen to early anagen in wild-type mice, suggesting that leptin is an anagen inducer in vivo. Phosphorylation of Erk, Jak2 and Stat3 in human keratinocytes was stimulated by leptin and leptin fragment. In addition, RT-PCR and ELISA showed that the production of leptin by human dermal papilla cells increased under hypoxic condition, suggesting that hypoxia in catagen/telogen phase promotes leptin production, preparing for entry into the next anagen. In conclusion, leptin, a well-known adipokine, acts as an anagen inducer and represents a new player in hair biology.

Protective effects and mechanisms of total alkaloids of Rubus alceaefolius Poir on non‑alcoholic fatty liver disease in rats

The plant Rubus alceaefolius Poir is used as a hepatic protectant in Traditional Chinese Medicine. The aim of the present study was to confirm the protective effect of the total alkaloids of Rubus alceaefolius Poir (TARAP) on the liver and to evaluate the potential molecular mechanisms associated with adipocytokines underlying non-alcoholic fatty liver disease (NAFLD) in rats. To generate the NAFLD model, Sprague-Dawley rats were administered a high‑fat diet and following 12 weeks of model construction, rats were orally treated with a positive control drug and different doses of TARAP daily for 28 days. The rats were then sacrificed and the livers were collected to evaluate the liver index (LI) and observe histological changes by hematoxylin and eosin (H&E) staining. The secretion levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were examined by ELISA. Finally, the expression levels of leptin (LEP), resistin and adiponectin (APN) in liver tissues were determined by immunohistochemistry (IHC). The results demonstrated that, in the group treated with methionine and choline bitartrate tablets and in the groups treated with different doses of TARAP, there was a significant reduction in the LI (P<0.05 or P<0.01), a downregulation of the secretion levels of ALT and AST, reduced levels of LEP and resistin and an increased expression of APN in the liver of NAFLD rats compared with the model group. Furthermore, the effect of TARAP treatment of NAFLD rats was dose dependent. In conclusion, TARAP is a potential agent for downregulating LEP and resistin and upregulating APN expression in rats with NAFLD. Furthermore, TARAP may be a potential candidate for improving treatment responses in patients with NAFLD.