The role of Smads in skin development

Conserved regulatory switches for the transition from natal down to juvenile feather in birds

The transition from natal downs for heat conservation to juvenile feathers for simple flight is a remarkable environmental adaptation process in avian evolution. However, the underlying epigenetic mechanism for this primary feather transition is mostly unknown. Here we conducted time-ordered gene co-expression network construction, epigenetic analysis, and functional perturbations in developing feather follicles to elucidate four downy-juvenile feather transition events. We report that extracellular matrix reorganization leads to peripheral pulp formation, which mediates epithelial-mesenchymal interactions for branching morphogenesis. α-SMA (ACTA2) compartmentalizes dermal papilla stem cells for feather renewal cycling. LEF1 works as a key hub of Wnt signaling to build rachis and converts radial downy to bilateral symmetry. Novel usage of scale keratins strengthens feather sheath with SOX14 as the epigenetic regulator. We show that this primary feather transition is largely conserved in chicken (precocial) and zebra finch (altricial) and discuss the possibility that this evolutionary adaptation process started in feathered dinosaurs.

Regulation of signaling pathways in hair follicle stem cells

Hair follicle stem cells (HFSCs) reside in the bulge region of the outer root sheath of the hair follicle. They are considered slow-cycling cells that are endowed with multilineage differentiation potential and superior proliferative capacity. The normal morphology and periodic growth of HFSCs play a significant role in normal skin functions, wound repair and skin regeneration. The HFSCs involved in these pathophysiological processes are regulated by a series of cell signal transduction pathways, such as lymphoid enhancer factor/T-cell factor, Wnt/β-catenin, transforming growth factor-β/bone morphogenetic protein, Notch and Hedgehog. The mechanisms of the interactions among these signaling pathways and their regulatory effects on HFSCs have been previously studied, but many mechanisms are still unclear. This article reviews the regulation of hair follicles, HFSCs and related signaling pathways, with the aims of summarizing previous research results, revealing the regulatory mechanisms of HFSC proliferation and differentiation and providing important references and new ideas for treating clinical diseases.

A probabilistic Boolean model on hair follicle cell fate regulation by TGF-β

Hair follicles (HFs) are mini skin organs that undergo cyclic growth. Various signals regulate HF cell fate decisions jointly. Recent experimental results suggest that transforming growth factor beta (TGF-β) exhibits a dual role in HF cell fate regulation that can be either anti- or pro-apoptosis. To understand the underlying mechanisms of HF cell fate control, we develop a novel probabilistic Boolean network (pBN) model on the HF epithelial cell gene regulation dynamics. First, the model is derived from literature, then refined using single-cell RNA sequencing data. Using the model, we both explore the mechanisms underlying HF cell fate decisions and make predictions that could potentially guide future experiments: 1) we propose that a threshold-like switch in the TGF-β strength may necessitate the dual roles of TGF-β in either activating apoptosis or cell proliferation, in cooperation with Bmp and tumor necrosis factor (TNF) and at different stages of a follicle growth cycle; 2) our model shows concordance with the high-activator-low-inhibitor theory of anagen initiation; 3) we predict that TNF may be more effective in catagen initiation than TGF-β, and they may cooperate in a two-step fashion; 4) finally, predictions of gene knockout and overexpression reveal the roles in HF cell fate regulations of each gene. Attractor and motif analysis from the associated Boolean networks reveal the relations between the topological structure of the gene regulation network and the cell fate regulation mechanism. A discrete spatial model equipped with the pBN illustrates how TGF-β and TNF cooperate in initiating and driving the apoptosis wave during catagen.

Lagerstroemia indica extract regulates human hair dermal papilla cell growth and degeneration via modulation of β-catenin, Stat6 and TGF-β signaling pathway

BACKGROUND

Lagerstroemia indica (L. indica) is reported to have diverse biological activities including anti-inflammatory, anti-cancer, neuro-regulatory, antidiabetic and antioxidant activity.

AIMS

The purpose of the present study is to examine the potential of hair growth promotion and/or hair loss prevention by L. indica extract.

PATIENTS/METHODS

The effects of L. indica on hair growth have been studied in human hair follicle dermal papillary (hHFDP) cells and follicular organ culture ex vivo by cell proliferation assay, PCR, western blot analysis and reporter gene activity assay. Moreover, a clinical trial was conducted in healthy volunteers.

RESULTS

L. indica significantly promoted the proliferation of hHFDP cells, which was associated with increased expression of TCF/LEF, VEGF and Gli1 mRNA, and inhibition of STAT6 and Smad2 mRNA. Treatment with L. indica also increased the TCF/LEF reporter gene activity but downregulated the SBE- and STAT6-luciferase activities. The expression of total β-catenin, CDK4 and CDK2 were elevated, while that of STAT6 and SMAD2/3 was suppressed upon treatment with L. indica. In human hair follicles organ culture, L. indica significantly inhibited hair follicular degeneration. The clinical trial showed a statistically significant rise in total hair count in test group (n=24) after 24 weeks of applying the hair tonic enriched with L. indica (141.46 ± 21.27 number/cm² , p < 0.05).

CONCLUSION

We suggest that L. indica extract prevents hair loss as well as stimulate hair growth by regulating the Wnt-β-catenin, JAK3-STAT6 and TGF-β1-Smad signaling pathways, and may be further developed as a novel functional cosmetic for preventing hair loss.

Epidermal Stem Cell in Wound Healing of Gliricidia sepium Leaves from Indonesia and the Philippines in Rats (Rattus norvegicus)

AIM: This study intended to investigate the regenerate wound, due to the ointment therapy containing Gliricidia sepium leaves that has potential-induced epidermal stem cells producing. It determined its effect on the expression of transforming growth factor-β1 (TGF-β1), Smad-3, β-catenin, LGR-6. MATERIALS AND METHODS: About 16 Wistar male rats aged approximately 2 months (150–200g) were used and were divided into four treatment groups (T1, positive control; T2, negative control; T3, wounds treated with G. sepium from Indonesia; and T4, wounds treated with G. sepium from the Philippines). The treatment of ointment was applied to the wound for 3 days. The expression of TGF-β1, Smad-3, β-catenin, and LGR-6 was observed by immunohistochemistry staining. RESULTS: G. sepium leaves significantly (p < 0.05) upregulated the expression of TGF-β1, Smad-3, β-catenin, and LGR-6 in the group treated with Indonesian G. sepium leaves were higher than that in the group treated with G. sepium leaves from the Philippines. CONCLUSIONS: Both leaves Varian contain flavonoids, saponins, and tannins, which act as producing epidermal stem cell agents to enhance the wound healing process. It can be concluded that both Gl. sepium Varian Indonesia and the Philippines have a potential effect on wound healing.

Approaches for Regenerative Healing of Cutaneous Wound with an Emphasis on Strategies Activating the Wnt/β-Catenin Pathway

Significance: In adult mammals, spontaneous repair of a cutaneous wound occurs slowly and leaves a scar with skin adnexa deficiencies. To accelerate cutaneous wound-healing rates and avoid scar formation, current studies have focused on regenerative therapies. Recent Advances: Emerging therapeutics for regenerative wound healing often focus on the use of growth factors and stem cells. However, these therapeutic approaches have limited routine clinical use due to high costs and technical requirements. Critical Issue: Understanding the molecular mechanisms involved in the signaling pathways for cutaneous wound healing and neogenic synthesis of the skin components is important for identification of novel targets for the development of regenerative wound-healing agents. Future Directions: The Wnt/β-catenin pathway is a well-known key player for enhancement of the overall healing process involving tissue regeneration via crosstalk with other signaling pathways. Strategies that activate the Wnt/β-catenin pathway via modulation of the pathway-controlling regulatory factors could provide effective therapeutic approaches for regenerative wound healing.

Eisenia bicyclis Extract Repairs UVB-Induced Skin Photoaging In Vitro and In Vivo: Photoprotective Effects

Chronic exposure to ultraviolet B (UVB) is a major cause of skin aging. The aim of the present study was to determine the photoprotective effect of a 30% ethanol extract of Eisenia bicyclis (Kjellman) Setchell (EEB) against UVB-induced skin aging. By treating human dermal fibroblasts (Hs68) with EEB after UVB irradiation, we found that EEB had a cytoprotective effect. EEB treatment significantly decreased UVB-induced matrix metalloproteinase-1 (MMP-1) production by suppressing the activation of mitogen-activated protein kinase (MAPK)/activator protein 1 (AP-1) signaling and enhancing the protein expression of tissue inhibitors of metalloproteinases (TIMPs). EEB was also found to recover the UVB-induced degradation of pro-collagen by upregulating Smad signaling. Moreover, EEB increased the mRNA expression of filaggrin, involucrin, and loricrin in UVB-irradiated human epidermal keratinocytes (HaCaT). EEB decreased UVB-induced reactive oxygen species (ROS) generation by upregulating glutathione peroxidase 1 (GPx1) and heme oxygenase-1 (HO-1) expression via nuclear factor erythroid-2-related factor 2 (Nrf2) activation in Hs68 cells. In a UVB-induced HR-1 hairless mouse model, the oral administration of EEB mitigated photoaging lesions including wrinkle formation, skin thickness, and skin dryness by downregulating MMP-1 production and upregulating the expression of pro-collagen type I alpha 1 chain (pro-COL1A1). Collectively, our findings revealed that EEB prevents UVB-induced skin damage by regulating MMP-1 and pro-collagen type I production through MAPK/AP-1 and Smad pathways.

Perspectives on miRNAs Targeting DKK1 for Developing Hair Regeneration Therapy

Androgenetic alopecia (AGA) remains an unsolved problem for the well-being of humankind, although multiple important involvements in hair growth have been discovered. Up until now, there is no ideal therapy in clinical practice in terms of efficacy and safety. Ultimately, there is a strong need for developing a feasible remedy for preventing and treating AGA. The Wnt/β-catenin signaling pathway is critical in hair restoration. Thus, AGA treatment via modulating this pathway is rational, although challenging. Dickkopf-related protein 1 (DKK1) is distinctly identified as an inhibitor of canonical Wnt/β-catenin signaling. Thus, in order to stimulate the Wnt/β-catenin signaling pathway, inhibition of DKK1 is greatly demanding. Studying DKK1-targeting microRNAs (miRNAs) involved in the Wnt/β-catenin signaling pathway may lay the groundwork for the promotion of hair growth. Bearing in mind that DKK1 inhibition in the balding scalp of AGA certainly makes sense, this review sheds light on the perspectives of miRNA-mediated hair growth for treating AGA via regulating DKK1 and, eventually, modulating Wnt/β-catenin signaling. Consequently, certain miRNAs regulating the Wnt/β-catenin signaling pathway via DKK1 inhibition might represent attractive candidates for further studies focusing on promoting hair growth and AGA therapy.

Liposomal honokiol promotes hair growth via activating Wnt3a/β-catenin signaling pathway and down regulating TGF-β1 in C57BL/6N mice

Liposomal honokiol isolated from the genus Magnolia has been found to have antiangiogenic, anti-inflammatory and antitumor properties. However, there has no report on its role in hair growth. Hair follicles are life-long cycled organelles that go through from anagen, catagen and telogen stages and are regulated by diverse signaling pathways, including Wnt/β-catenin, Notch, Epidermal growth factor (EGF) and Sonic hegehog (SHH). Wnt signals are essential for the initiation of hair follicle placode development and a new potential target of hair loss treatment. This study was designed to investigate the effect of liposomal honokiol (Lip-honokiol) on inducing hair anagen. We identified the hair grew out in advance in the shaving area of C57BL/6N mice after the treatment of liposomal honokiol (Lip-honokiol) by daily abdominal injection. We first demonstrated that Lip-Honokiol activated the Wnt3a/β-catenin pathway and downregulated the transforming growth factor-β1 (TGF-β1) to promote hair growth in mice via immunohistochemistry and immunofluorescence staining. These findings suggest that Lip-honokiol activated the Wnt/β-catenin pathway and accelerated the transfer from the telogen to anagen stage and finally promoted the hair growth.

Smad7 in psoriasis vulgaris patients: A clinical and immunohistochemical study

BACKGROUND

Psoriasis is an inflammatory disease that is mostly immune-derived. It causes proliferation of skin cells, forming plaques. Psoriasis etiology is unknown. It might be multifactorial.

AIMS

This work aimed to study Smad7 expression in psoriasis vulgaris patients in comparison with normal skin.

PATIENTS/METHODS

Thirty patients with psoriasis vulgaris in comparison with 20 age- and sex-matched seemingly healthy individuals were selected. We used psoriasis area and severity index (PASI) to evaluate psoriasis severity. Skin biopsies were prepared from skin lesions (30), perilesions (30) and control (20) groups for histopathological and immunostaining evaluation of Smad7.

RESULTS

Smad7 was progressively upregulated in proliferating keratinocytes from controls (58.18 ± 30.93) to perilesional (106 ± 38.93) and lesional (156.33 ± 62.01) skin (P < .001). Also, dermal inflammatory cells showed upregulation of Smad7 expression from control skin (40 ± 28.28) to skin lesions (137.33 ± 73.86) (P < .010). Smad7 expression showed a positive significant correlation with psoriasis severity (r = .452; P < .012).

CONCLUSION

Smad7 may be involved in increased keratinocyte proliferation as well as skin inflammation in psoriasis vulgaris patients.

Morpho-regulation in diverse chicken feather formation: Integrating branching modules and sex hormone-dependent morpho-regulatory modules

Many animals can change the size, shape, texture and color of their regenerated coats in response to different ages, sexes, or seasonal environmental changes. Here, we propose that the feather core branching morphogenesis module can be regulated by sex hormones or other environmental factors to change feather forms, textures or colors, thus generating a large spectrum of complexity for adaptation. We use sexual dimorphisms of the chicken to explore the role of hormones. A long-standing question is whether the sex-dependent feather morphologies are autonomously controlled by the male or female cell types, or extrinsically controlled and reversible. We have recently identified core feather branching molecular modules which control the anterior-posterior (bone morphogenetic orotein [BMP], Wnt gradient), medio-lateral (Retinoic signaling, Gremlin), and proximo-distal (Sprouty, BMP) patterning of feathers. We hypothesize that morpho-regulation, through quantitative modulation of existing parameters, can act on core branching modules to topologically tune the dimension of each parameter during morphogenesis and regeneration. Here, we explore the involvement of hormones in generating sexual dimorphisms using exogenously delivered hormones. Our strategy is to mimic male androgen levels by applying exogenous dihydrotestosterone and aromatase inhibitors to adult females and to mimic female estradiol levels by injecting exogenous estradiol to adult males. We also examine differentially expressed genes in the feathers of wildtype male and female chickens to identify potential downstream modifiers of feather morphogenesis. The data show male and female feather morphology and their color patterns can be modified extrinsically through molting and resetting the stem cell niche during regeneration.

Dynamic transcriptome profiling towards understanding the morphogenesis and development of diverse feather in domestic duck

Background

Feathers with complex and fine structure are hallmark avian integument appendages, which have contributed significantly to the survival and breeding for birds. Here, we aimed to explore the differentiation, morphogenesis and development of diverse feathers in the domestic duck.

Results

Transcriptome profiles of skin owing feather follicle from two body parts at three physiological stages were constructed to understand the molecular network and excavate the candidate genes associated with the development of plumulaceous and flight feather structures. The venn analysis of differentially expressed genes (DEGs) between abdomen and wing skin tissues at three developmental stages showed that 38 genes owing identical differentially expression pattern. Together, our data suggest that feather morphological and structural diversity can be possibly related to the homeobox proteins. The key series-clusters, many candidate biological processes and genes were identified for the morphogenesis, growth and development of two feather types. Through comparing the results of developmental transcriptomes from plumulaceous and flight feather, we found that DEGs belonging to the family of WNT, FGF and BMP have certain differences; even the consistent DEGs of skin and feather follicle transcriptomes from abdomen and wing have the different expression patterns.

Conclusions

Overall, this study detected many functional genes and showed differences in the molecular mechanisms of diverse feather developments. The findings in WNT, FGF and BMP, which were consistent with biological experiments, showed more possible complex modulations. A correlative role of HOX genes was also suggested but future biological verification experiments are required. This work provided valuable information for subsequent research on the morphogenesis of feathers.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4778-7) contains supplementary material, which is available to authorized users.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.

MicroRNAs in the skin: role in development, homoeostasis and regeneration

The skin is the largest organ of the integumentary system and possesses a vast number of functions. Due to the distinct layers of the skin and the variety of cells which populate each, a tightly regulated network of molecular signals control development and regeneration, whether due to programmed cell termination or injury. MicroRNAs (miRs) are a relatively recent discovery; they are a class of small non-coding RNAs which possess a multitude of biological functions due to their ability to regulate gene expression via post-transcriptional gene silencing. Of interest, is that a plethora of data demonstrates that a number of miRs are highly expressed within the skin, and are evidently key regulators of numerous vital processes to maintain non-aberrant functioning. Recently, miRs have been targeted as therapeutic interventions due to the ability of synthetic 'antagomiRs' to down-regulate abnormal miR expression, thereby potentiating wound healing and attenuating fibrotic processes which can contribute to disease such as systemic sclerosis (SSc). This review will provide an introduction to the structure and function of the skin and miR biogenesis, before summarizing the literature pertaining to the role of miRs. Finally, miR therapies will also be discussed, highlighting important future areas of research.

Potential mechanisms underlying ectodermal differentiation of Wharton's jelly mesenchymal stem cells

Wharton's jelly mesenchymal stem cells (WJMSCs) are being increasingly recognized for their ectodermal differentiation potential. Previously, we demonstrated that when WJMSC were seeded onto an acellular matrix material derived from Wharton's jelly and cultured in osteogenic induction media, generated CK19 positive cells and hair-like structures indicative of ectodermal differentiation of WJMSCs. In this manuscript, we examine the underlying mechanism behind this observation using a variety of microscopy and molecular biology techniques such as western blotting and qPCR. We demonstrate that these hair-like structures are associated with live cells that are positive for epithelial and mesenchymal markers such as cytokeratin-19 and α-smooth muscle actin, respectively. We also show that up-regulation of β-catenin and noggin, along with the expression of TGF-β and SMAD and inhibition of BMP4 could be the mechanism behind this ectodermal differentiation and hair-like structure formation.

Identification of a novel LEMD3 Y871X mutation in a three-generation family with osteopoikilosis and review of the literature

INTRODUCTION

Osteopoikilosis is a rare and benign autosomal dominant genetic disorder, characterized by a symmetric but unequal distribution of multiple hyperostotic areas in different parts of the skeleton. Recent studies have reported loss-of-function mutations in the LEM domain containing 3 (LEMD3) gene, encoding an inner nuclear membrane protein, as a cause of osteopoikilosis.

METHODS

We investigated LEMD3 gene in a three-generation family from China, with six patients affected with osteopoikilosis. Peripheral blood samples were collected from family members and 100 healthy controls. All exons of the LEMD3 gene and adjacent exon-intron sequences were amplified by PCR and subsequently sequenced.

RESULTS

A novel heterozygous c.2612_2613insA (p.Y871X) mutation in exon 13 of LEMD3 was identified, which resulted in a frame shift predicted to generate a premature stop codon at amino acid position 871. The mutation co-segregates with the osteopoikilosis phenotype and was not found in 100 ethnically matched controls.

CONCLUSION

We identified a new mutation in LEMD3 gene, accounting for the familial case of osteopoikilosis. In addition we also review the clinical manifestation, diagnosis and treatment of osteopoikilosis.

TGF-beta-induced early gene-1 overexpression promotes oxidative stress protection and actin cytoskeleton rearrangement in human skin fibroblasts

BACKGROUND

Transforming growth factor beta inducible early gene-1 (TIEG-1), a member of the Krüppel-like factor, was identified as a primary response gene for TGF-β. The role of TIEG-1 in skin repair has been mainly addressed in vivo on TIEG-1 null mice model and the mechanism remains unexplored.

METHODS

We investigated the modulation of TIEG-1 expression in normal human skin fibroblasts by either down-expressing or overexpressing the gene. We evaluated reactive oxygen species production and the cell viability of treated cells. The effect of TIEG-1 overexpression was monitored by wound healing assay and immunofluorescence staining of actin fibers organization and alpha-smooth muscle actin (α-SMA). Western blots were carried out to identify the level of expression or phosphorylation of key proteins such as cofilin, Rho GTPases, and p38 mitogen-activated protein kinase (p38 MAPK).

RESULTS

TIEG-1 down-regulation had a deleterious effect on the cell viability. It was significantly reduced (65±5%) and exposure to ultraviolet further increased this effect (47±3%). By contrast, cells overexpressing TIEG-1 had a reduced reactive oxygen species production (75%) compared to control and mock-transfected cells. This overexpression also resulted in formation of actin stress fibers and increased α-SMA expression and an enhanced wound healing feature. RhoB GTPase was upregulated and phosphorylation of cofilin and p38 MAPK was observed.

CONCLUSION

TIEG-1 overexpression in normal human skin fibroblasts results in improved resistance to oxidative stress, myofibroblast-like conversion that involved RhoB signaling pathway with cofilin and p38 MAPK proteins activation.

GENERAL SIGNIFICANCE

This study enlightens the role of TIEG-1 role in skin biology.

High concentrations of mast cell chymase facilitate the transduction of the transforming growth factor-β1/Smads signaling pathway in skin fibroblasts

The aim of the present study was to investigate the effect of different concentrations of mast cell chymase on the transforming growth factor (TGF)-β1/Smad signaling pathway in skin fibroblasts. Cultured skin fibroblasts were treated with various concentrations of chymase for different time periods. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to assess the rate of cell proliferation. In addition, protein expression in the fibroblasts was measured using western blot analysis. Chymase was shown to enhance the proliferation of skin fibroblasts following incubation for 48, 72 and 96 h (P<0.01). Furthermore, high concentrations of mast cell chymase were shown to enhance the mRNA and protein expression levels of TGF-β1 after long-term (≥6 h) incubation. In addition, high concentrations of mast cell chymase increased P-Smad2/3 and Smad2/3 protein expression. By contrast, low concentrations of mast cell chymase increased Smad7 protein expression. Therefore, the results demonstrated that high concentrations of mast cell chymase facilitated the transduction of the TGF-β1/Smad signaling pathway in skin fibroblasts.

The Role of TGFβ Signaling in Wound Epithelialization

Significance: Transforming growth factor β (TGFβ) has a crucial role in maintaining skin homeostasis. TGFβ signaling is important for re-epithelialization, inflammation, angiogenesis, and granulation tissue formation during wound healing. This review will discuss the most important findings regarding the role of TGFβ in epidermal maintenance and its restoration after injury. Recent Advances: Latest findings on the role of TGFβ signaling in normal and impaired wound healing, including the role of TGFβ pathway in tissue regeneration observed in super-healer animal models, will be reviewed. Critical Issues: The TGFβ pathway is attenuated in nonhealing wounds. Observed suppression of TGFβ signaling in chronic ulcers may contribute to the loss of tissue homeostasis and the inability of keratinocytes to migrate and close a wound. Future Directions: A better understanding of TGFβ signaling may provide new insights not only in the normal epithelialization process, but also in tissue regeneration. Future studies focused on TGFβ-mediated crosstalk between multiple cell types involved in wound healing may lead to development of novel therapeutic advances for chronic wounds.

New experimental models of skin homeostasis and diseases

Homeostasis, whose regulation at the molecular level is still poorly understood, is intimately related to the functions of epidermal stem cells. Five research groups have been brought together to work on new in vitro and in vivo skin models through the SkinModel-CM program, under the auspices of the Spanish Autonomous Community of Madrid. This project aims to analyze the functions of DNA methyltransferase 1, endoglin, and podoplanin in epidermal stem cell activity, homeostasis, and skin cancer. These new models include 3-dimensional organotypic cultures, immunodeficient skin-humanized mice, and genetically modified mice. Another aim of the program is to use skin-humanized mice to model dermatoses such as Gorlin syndrome and xeroderma pigmentosum in order to optimize new protocols for photodynamic therapy.

Effects of parafibromin expression on the phenotypes and relevant mechanisms in the DLD-1 colon carcinoma cell line

BACKGROUND

Parafibromin is a protein encoded by the HRPT2 (hyperparathyroidism 2) oncosuppressor gene and its down-regulated expression is involved in pathogenesis of parathyroid, breast, gastric and colorectal carcinomas. This study aimed to clarify the effects of parafibromin expression on the phenotypes and relevant mechanisms of DLD-1 colon carcinoma cells.

METHODS

DLD-1 cells transfected with a parafibromin-expressing plasmid were subjected to examination of phenotype, including proliferation, differentiation, apoptosis, migration and invasion. Phenotype-related proteins were measured by Western blot. Parafibromin and ki-67 expression was detected by immunohistochemistry on tissue microarrays.

RESULTS

The transfectants showed higher proliferation by CCK-8, better differentiation by electron microscopy and ALP activity and more apoptotic resistance to cisplatin by DNA fragmentation than controls. There was no difference in early apoptosis by annexin V, capase-3 activity, migration and invasion between DLD-1 cells and their transfectants. Ectopic parafibromin expression resulted in down-regulated expression of smad4, MEKK, GRP94, GRP78, GSK3β-ser9, and Caspase-9. However, no difference was detectable in caspase-12 and -8 expression. A positive relationship was noted between parafibromin and ki-67 expression in colorectal carcinoma.

CONCLUSIONS

Parafibromin overexpression could promote cell proliferation, apoptotic resistance, and differentiation of DLD-1 cells.

New molecular medicine-based scar management strategies

Keloids and hypertrophic scars are prevalent disabling conditions with still suboptimal treatments. Basic science and molecular-based medicine research have contributed to unravel new bench-to-bedside scar therapies and to dissect the complex signalling pathways involved. Peptides such as the transforming growth factor beta (TGF-β) superfamily, with Smads, Ski, SnoN, Fussels, endoglin, DS-Sily, Cav-1p, AZX100, thymosin-β4 and other related molecules may emerge as targets to prevent and treat keloids and hypertrophic scars. The aim of this review is to describe the basic complexity of these new molecular scar management strategies and point out new fibrosis research lines.

Effects and mechanisms of a microcurrent dressing on skin wound healing: a review

The variety of wound types has resulted in a wide range of wound dressings, with new products frequently being introduced to target different aspects of the wound healing process. The ideal wound dressing should achieve rapid healing at a reasonable cost, with minimal inconvenience to the patient. Microcurrent dressing, a novel wound dressing with inherent electric activity, can generate low-level microcurrents at the device-wound contact surface in the presence of moisture and can provide an advanced wound healing solution for managing wounds. This article offers a review of the effects and mechanisms of the microcurrent dressing on the healing of skin wounds.

Persea americana Mill. Seed: Fractionation, Characterization, and Effects on Human Keratinocytes and Fibroblasts

Methanolic avocado (Persea americana Mill., Lauraceae) seed extracts were separated by preparative HSCCC. Partition and HSCCC fractions were principally characterized by LC-ESI-MS/MS analysis. Their in vitro influence was investigated on proliferation, differentiation, cell viability, and gene expression on HaCaT and normal human epidermal keratinocytes (NHEK) and normal human dermal fibroblasts (NHDF). The methanol-water partition (M) from avocado seeds and HSCCC fraction 3 (M.3) were mostly composed of chlorogenic acid and its isomers. Both reduced NHDF but enhanced HaCaT keratinocytes proliferation. HSCCC fraction M.2 composed of quinic acid among chlorogenic acid and its isomers inhibited proliferation and directly induced differentiation of keratinocytes as observed on gene and protein level. Furthermore, M.2 increased NHDF proliferation via upregulation of growth factor receptors. Salidrosides and ABA derivatives present in HSCCC fraction M.6 increased NHDF and keratinocyte proliferation that resulted in differentiation. The residual solvent fraction M.7 contained among low concentrations of ABA derivatives high amounts of proanthocyanidins B1 and B2 as well as an A-type trimer and stimulated proliferation of normal cells and inhibited the proliferation of immortalized HaCaT keratinocytes.

Galvanic microparticles increase migration of human dermal fibroblasts in a wound-healing model via reactive oxygen species pathway

Electrical signals have been implied in many biological mechanisms, including wound healing, which has been associated with transient electrical currents not present in intact skin. One method to generate electrical signals similar to those naturally occurring in wounds is by supplementation of galvanic particles dispersed in a cream or gel. We constructed a three-layered model of skin consisting of human dermal fibroblasts in hydrogel (mimic of dermis), a hydrogel barrier layer (mimic of epidermis) and galvanic microparticles in hydrogel (mimic of a cream containing galvanic particles applied to skin). Using this model, we investigated the effects of the properties and amounts of Cu/Zn galvanic particles on adult human dermal fibroblasts in terms of the speed of wound closing and gene expression. The collected data suggest that the effects on wound closing are due to the ROS-mediated enhancement of fibroblast migration, which is in turn mediated by the BMP/SMAD signaling pathway. These results imply that topical low-grade electric currents via microparticles could enhance wound healing.

Molecular and cellular mechanisms of bone morphogenetic proteins and activins in the skin: potential benefits for wound healing

Bone morphogenetic proteins (BMPs) and activins are phylogenetically conserved proteins, belonging to the transforming growth factor-β superfamily, that signal through the phosphorylation of receptor-regulated Smad proteins, activating different cell responses. They are involved in various steps of skin morphogenesis and wound repair, as can be evidenced by the fact that their expression is increased in skin injuries. BMPs play not only a role in bone regeneration but are also involved in cartilage, tendon-like tissue and epithelial regeneration, maintain vascular integrity, capillary sprouting, proliferation/migration of endothelial cells and angiogenesis, promote neuron and dendrite formation, alter neuropeptide levels and are involved in immune response modulation, at least in animal models. On the other hand, activins are involved in wound repair through the regulation of skin and immune cell migration and differentiation, re-epithelialization and granulation tissue formation, and also promote the expression of collagens by fibroblasts and modulate scar formation. This review aims at enunciating the effects of BMPs and activins in the skin, namely in skin development, as well as in crucial phases of skin wound healing, such as inflammation, angiogenesis and repair, and will focus on the effects of these proteins on skin cells and their signaling pathways, exploring the potential therapeutic approach of the application of BMP-2, BMP-6 and activin A in chronic wounds, particularly diabetic foot ulcerations.

OxymiRs in cutaneous development, wound repair and regeneration

The state of tissue oxygenation is widely recognized as a major microenvironmental cue that is known to regulate the expression of coding genes. Recent works have extended that knowledge to demonstrate that the state of tissue oxygenation may potently regulate the expression of microRNAs (miRs). Collectively, such miRs that are implicated in defining biological outcomes in response to a change in the state of tissue oxygenation may be referred to as oxymiRs. Broadly, oxymiRs may be categorized into three groups: (A) the existence (expression and/or turnover) of which is directly influenced by changes in the state of tissue oxygenation; (B) the existence of which is indirectly (e.g. oxygen-sensitive proteins, metabolites, pH, etc.) influenced by changes in the state of tissue oxygenation; and (C) those that modify biological outcomes to changes in the state of tissue oxygenation by targeting oxygen sensing pathways. This work represents the first review of how oxymiRs may regulate development, repair and regeneration. Currently known oxymiRs may affect the functioning of a large number of coding genes which have hitherto fore never been linked to oxygen sensing. Many of such target genes have been validated and that number is steadily growing. Taken together, our understanding of oxymiRs has vastly expanded the implications of changes in the state of tissue oxygenation. This emerging paradigm has major implications in untangling the complexities underlying diseases associated with ischemia and related hypoxic insult such as chronic wounds.

Expression patterns of MDA-9/syntenin during development of the mouse embryo

Melanoma differentiation associated gene-9 (MDA-9)/syntenin is a PDZ domain-containing adaptor protein involved in multiple diverse cellular processes including organization of protein complexes in the plasma membrane, intracellular trafficking and cell surface targeting, synaptic transmission, and cancer metastasis. In the present study, we analyzed the expression pattern of MDA-9/syntenin during mouse development. MDA-9/syntenin was robustly expressed with tight regulation of its temporal and spatial expression during fetal development in the developing skin, spinal cord, heart, lung and liver, which are regulated by multiple signaling pathways in the process of organogenesis. Recent studies also indicate that MDA-9/syntenin is involved in the signaling pathways crucial during development such as Wnt, Notch and FGF. Taken together, these results suggest that MDA-9/syntenin may play a prominent role during normal mouse development in the context of cell proliferation as well as differentiation through modulating multiple signaling pathways as a crucial adaptor protein. Additionally, temporal regulation of MDA-9/syntenin expression may be required during specific stages and in specific tissues during development.

Cutaneous wound healing: recruiting developmental pathways for regeneration

Following a skin injury, the damaged tissue is repaired through the coordinated biological actions that constitute the cutaneous healing response. In mammals, repaired skin is not identical to intact uninjured skin, however, and this disparity may be caused by differences in the mechanisms that regulate postnatal cutaneous wound repair compared to embryonic skin development. Improving our understanding of the molecular pathways that are involved in these processes is essential to generate new therapies for wound healing complications. Here we focus on the roles of several key developmental signaling pathways (Wnt/β-catenin, TGF-β, Hedgehog, Notch) in mammalian cutaneous wound repair, and compare this to their function in skin development. We discuss the varying responses to cutaneous injury across the taxa, ranging from complete regeneration to scar tissue formation. Finally, we outline how research into the role of developmental pathways during skin repair has contributed to current wound therapies, and holds potential for the development of more effective treatments.

Confluence switch signaling regulates ECM composition and the plasmin proteolytic cascade in keratinocytes

In culture, cell confluence generates signals that commit actively growing keratinocytes to exit the cell cycle and differentiate to form a stratified epithelium. Using a comparative proteomic approach, we studied this 'confluence switch' and identified a new pathway triggered by cell confluence that regulates basement membrane (BM) protein composition by suppressing the uPA-uPAR-plasmin pathway. Indeed, confluence triggers adherens junction maturation and enhances TGF-β and activin A activity, resulting in increased deposition of PAI-1 and perlecan in the BM. Extracellular matrix (ECM)-accumulated PAI-1 suppresses the uPA-uPAR-plasmin pathway and further enhances perlecan deposition by inhibiting its plasmin-dependent proteolysis. We show that perlecan deposition in the ECM strengthens cell adhesion, inhibits keratinocyte motility and promotes additional accumulation of PAI-1 in the ECM at confluence. In agreement, during wound-healing, perlecan concentrates at the wound-margin, where BM matures to stabilize keratinocyte adhesion. Our results demonstrate that confluence-dependent signaling orchestrates not only growth inhibition and differentiation, but also controls ECM proteolysis and BM formation. These data suggest that uncontrolled integration of confluence-dependent signaling, might favor skin disorders, including tumorigenesis, not only by promoting cell hyperproliferation, but also by altering protease activity and deposition of ECM components.

Implications of TGFβ on Transcriptome and Cellular Biofunctions of Palatal Mesenchyme

Development of the palate comprises sequential stages of growth, elevation, and fusion of the palatal shelves. The mesenchymal component of palates plays a major role in early phases of palatogenesis, such as growth and elevation. Failure in these steps may result in cleft palate, the second most common birth defect in the world. These early stages of palatogenesis require precise and chronological orchestration of key physiological processes, such as growth, proliferation, differentiation, migration, and apoptosis. There is compelling evidence for the vital role of TGFβ-mediated regulation of palate development. We hypothesized that the isoforms of TGFβ regulate different cellular biofunctions of the palatal mesenchyme to various extents. Human embryonic palatal mesenchyme (HEPM) cells were treated with TGFβ1, β2, and β3 for microarray-based gene expression studies in order to identify the roles of TGFβ in the transcriptome of the palatal mesenchyme. Following normalization and modeling of 28,869 human genes, 566 transcripts were detected as differentially expressed in TGFβ-treated HEPM cells. Out of these altered transcripts, 234 of them were clustered in cellular biofunctions, including growth and proliferation, development, morphology, movement, cell cycle, and apoptosis. Biological interpretation and network analysis of the genes active in cellular biofunctions were performed using IPA. Among the differentially expressed genes, 11 of them are known to be crucial for palatogenesis (EDN1, INHBA, LHX8, PDGFC, PIGA, RUNX1, SNAI1, SMAD3, TGFβ1, TGFβ2, and TGFβR1). These genes were used for a merged interaction network with cellular behaviors. Overall, we have determined that more than 2% of human transcripts were differentially expressed in response to TGFβ treatment in HEPM cells. Our results suggest that both TGFβ1 and TGFβ2 orchestrate major cellular biofunctions within the palatal mesenchyme in vitro by regulating expression of 234 genes.

Ontogeny and Homeostasis of Adult Epithelial Skin Stem Cells

Mouse epithelial skin stem cells constitute an important model system for understanding the dynamics of stem cell emergence and behavior in an intact vertebrate tissue. Recent published work defined discrete populations of epithelial stem cells in the adult skin epithelium, which reside in the hair follicle bulge and germ, isthmus, sebaceous gland and inter-follicular epidermis. Adult epidermal and hair follicle stem cells seem to adopt mostly symmetric or unidirectional fate decisions of either one of two possible fates: (1) differentiate and be lost from the tissue or (2) expand symmetrically to self-renew. Asymmetric divisions appear to be mostly implicated in differentiation and stratification of the epidermis. While mechanisms of adult stem cell homeostasis begin to be unraveled, the embryonic origin of the adult epithelial skin stem cells is poorly understood. Recent studies reported Sox9, Lgr6, and Runx1 expression in subpopulations of cells in the embryonic hair placode. These subpopulations seem to act as precursors of different classes of adult epithelial stem cells. In particular, Runx1 regulates a Wnt-mediated cross-talk between the nascent adult-type hair follicle stem cells and their environment, which is essential for timely stem cell emergence, proper maturation, long-term differentiation potential, and maintenance. The new data begin to define the basic dynamics and regulatory pathways governing the ontogeny of adult epithelial stem cells.

Meta-analysis of genome-wide association studies identifies three new risk loci for atopic dermatitis

Atopic dermatitis (AD) is a commonly occurring chronic skin disease with high heritability. Apart from filaggrin (FLG), the genes influencing atopic dermatitis are largely unknown. We conducted a genome-wide association meta-analysis of 5,606 affected individuals and 20,565 controls from 16 population-based cohorts and then examined the ten most strongly associated new susceptibility loci in an additional 5,419 affected individuals and 19,833 controls from 14 studies. Three SNPs reached genome-wide significance in the discovery and replication cohorts combined, including rs479844 upstream of OVOL1 (odds ratio (OR) = 0.88, P = 1.1 × 10(-13)) and rs2164983 near ACTL9 (OR = 1.16, P = 7.1 × 10(-9)), both of which are near genes that have been implicated in epidermal proliferation and differentiation, as well as rs2897442 in KIF3A within the cytokine cluster at 5q31.1 (OR = 1.11, P = 3.8 × 10(-8)). We also replicated association with the FLG locus and with two recently identified association signals at 11q13.5 (rs7927894; P = 0.008) and 20q13.33 (rs6010620; P = 0.002). Our results underline the importance of both epidermal barrier function and immune dysregulation in atopic dermatitis pathogenesis.

Transforming Growth Factor-β and Endoglin Signaling Orchestrate Wound Healing

Physiological wound healing is a complex process requiring the temporal and spatial co-ordination of various signaling networks, biomechanical forces, and biochemical signaling pathways in both hypoxic and non-hypoxic conditions. Although a plethora of factors are required for successful physiological tissue repair, transforming growth factor beta (TGF-β) expression has been demonstrated throughout wound healing and shown to regulate many processes involved in tissue repair, including production of ECM, proteases, protease inhibitors, migration, chemotaxis, and proliferation of macrophages, fibroblasts of the granulation tissue, epithelial and capillary endothelial cells. TGF-β mediates these effects by stimulating signaling pathways through a receptor complex which contains Endoglin. Endoglin is expressed in a broad spectrum of proliferating and stem cells with elevated expression during hypoxia, and regulates important cellular functions such as proliferation and adhesion via Smad signaling. This review focuses on how the TGF-β family and Endoglin, regulate stem cell availability, and modulate cellular behavior within the wound microenvironment, includes current knowledge of the signaling pathways involved, and explores how this information may be applicable to inflammatory and/or angiogenic diseases such as fibrosis, rheumatoid arthritis and metastatic cancer.

Typha latifolia L. fruit polysaccharides induce the differentiation and stimulate the proliferation of human keratinocytes in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

In Northern America Typha latifolia L. (Typhaceae) fruits are used for more than 4000 years for treatment of skin disorders, burns and as wound dressing to absorb the ichors.

AIM OF THE STUDY

The following studies attempted to characterize water-soluble polysaccharides from aqueous Typha latifolia extracts and to investigate the influence of the polymers on cell physiology of human dermal fibroblasts (NHDF) and epidermal keratinocytes (NHEK).

MATERIALS AND METHODS

Water-soluble raw polysaccharides (RPS) were isolated from Typha latifolia fruits and fractionated by anion exchange chromatography (AEC) and size exclusion chromatography (GPC). Fractions obtained were characterized concerning monosaccharide composition by HPAEC-PAD. The bioactivity of the polysaccharides was investigated on cell viability, proliferation, differentiation and gene expression NHDF of NHEK.

RESULTS

RPS was fractionated into 5 heterodisperse fractions (TL1-TL5). The polysaccharides were composed mainly of glucose (more than 50% in RPS and TL4), galactose, xylose, mannose, glucuronic acid, galacturonic acid, arabinose, ribose, fucose, rhamnose, and fructose with differing amounts concerning to RPS and AEC-fractions. Proteins were detected in the RPS (10%) and to a less extend in TL1-TL3 (1-3%). TL1-TL3 significantly increased the proliferation of keratinocytes, whereas TL4 was shown to be a potent inductor of the early differentiation process of keratinocytes. Gene expression analysis supported these results since Smad3 and PKC-α, known to be part of signal pathways leading to cell differentiation, were significantly up regulated. Effects on fibroblasts were not observed, indicating cell specific activity of the polysaccharides.

CONCLUSION

The results clearly indicate a rationale for the traditional use of Typha latifolia fruits extracts for wound healing to the strong stimulatory activity of the polysaccharides on keratinocytes proliferation and early differentiation, major activities necessary for potent wound-healing agents.

A decisive function of transforming growth factor-β/Smad signaling in tissue morphogenesis and differentiation of human HaCaT keratinocytes

By interfering with the TGFβ/Smad pathway in the human HaCaT keratinocytes, this study provides novel insights into the role of Smad signaling for regular tissue homeostasis and demonstrates its crucial role in terminal epidermal differentiation and in the decision between alternative epithelial differentiation programs.

 The mechanism by which transforming growth factor-β (TGFβ) regulates differentiation in human epidermal keratinocytes is still poorly understood. To assess the role of Smad signaling, we engineered human HaCaT keratinocytes either expressing small interfering RNA against Smads2, 3, and 4 or overexpressing Smad7 and verified impaired Smad signaling as decreased Smad phosphorylation, aberrant nuclear translocation, and altered target gene expression. Besides abrogation of TGFβ-dependent growth inhibition in conventional cultures, epidermal morphogenesis and differentiation in organotypic cultures were disturbed, resulting in altered tissue homeostasis with suprabasal proliferation and hyperplasia upon TGFβ treatment. Neutralizing antibodies against TGFβ, similar to blocking the actions of EGF-receptor or keratinocyte growth factor, caused significant growth reduction of Smad7-overexpressing cells, thereby demonstrating that epithelial hyperplasia was attributed to TGFβ-induced “dermis”-derived growth promoting factors. Furthermore impaired Smad signaling not only blocked the epidermal differentiation process or caused epidermal-to-mesenchymal transition but induced a switch to a complex alternative differentiation program, best characterized as mucous/intestinal-type epithelial differentiation. As the same alternative phenotype evolved from both modes of Smad-pathway interference, and reduction of Smad7-overexpression caused reversion to epidermal differentiation, our data suggest that functional TGFβ/Smad signaling, besides regulating epidermal tissue homeostasis, is not only essential for terminal epidermal differentiation but crucial in programming different epithelial differentiation routes.

Conditional activin receptor type 1B (Acvr1b) knockout mice reveal hair loss abnormality

The in vivo functions of the activin A receptor type 1b (Acvr1b) have been difficult to study because Acvr1b(-/-) mice die during embryogenesis. To investigate the roles of Acvr1b in the epithelial tissues, we created mice with a conditional disruption of Acvr1b (Acvr1b(flox/flox)) and crossed them with K14-Cre mice. Acvr1b(flox/flox); K14-Cre mice displayed various degrees of hairlessness at postnatal day 5, and the phenotype is exacerbated by age. Histological analyses showed that those hair follicles that developed during morphogenesis were later disrupted by delays in hair cycle reentry. Failure in cycling of the hair follicles and regrowth of the hair shaft and the inner root sheath resulted in subsequent severe hair loss. Apart from previous reports of other members of the transforming growth factor-β/activin/bone morphogenic protein pathways, we demonstrate a specialized role for Acvr1b in hair cycling in addition to hair follicle development. Acvr1b(flox/flox); K14-Cre mice also had a thicker epidermis than did wild-type mice, which resulted from persistent proliferation of skin epithelial cells; however, no tumor formation was observed by 18 months of age. Our analysis of this Acvr1b knockout mouse line provides direct genetic evidence that Acvr1b signaling is required for both hair follicle development and cycling.

Requirement of TGFbeta signaling for SMO-mediated carcinogenesis

Hedgehog (Hh) signaling, via the key signal transducer Smoothened (SMO) and Gli transcription factors, is essential for embryonic development and carcinogenesis. At present, the molecular mechanism of Hh signaling-mediated carcinogenesis is not completely understood. Using a mouse model (K14cre/R26SmoM2) of SMO-mediated basal cell carcinoma development, we identified TGFβ2 as a major Hh-regulated gene. TGFβ2 expression was high in the keratinocytes, with activated TGFβ signaling (indicated by elevated expression of phosphorylated SMAD2/3) detected in both tumor and stroma. The significance of TGFβ signaling for SMO function was demonstrated in two assays. Down-regulation of TGFβ2 expression prevented Hh signaling-dependent osteoblast differentiation and motor neuron differentiation. Furthermore, inhibition of TGFβ signaling by TGFβ receptor I inhibitor SD208 significantly reduced tumor area in K14cre/R26SmoM2 mice. Tumor shrinkage in mice was associated with an increased number of lymphocytes, suggesting an immune suppression role of TGFβ signaling. The relevance of our results to human cancer is reflected by the fact that human basal cell carcinomas, which almost always harbor activated Hh signaling, have activated TGFβ signaling, as indicated by high levels of phosphorylated SMAD2 and SMAD3 in tumor and stroma. Together, our data indicate that TGFβ signaling is critical for Hh signaling-mediated carcinogenesis.

Expression patterns of astrocyte elevated gene-1 (AEG-1) during development of the mouse embryo

Expression of astrocyte elevated gene-1 (AEG-1) is elevated in multiple human cancers including brain tumors, neuroblastomas, melanomas, breast cancers, non-small cell lung cancers, liver cancers, prostate cancers, and esophageal cancers. This gene plays crucial roles in tumor cell growth, invasion, angiogenesis and progression to metastasis. In addition, over-expression of AEG-1 protects primary and transformed cells from apoptosis-inducing signals by activating PI3K-Akt signaling pathways. These results suggest that AEG-1 is intimately involved in tumorigenesis and may serve as a potential therapeutic target for various human cancers. However, the normal physiological functions of AEG-1 require clarification. We presently analyzed the expression pattern of AEG-1 during mouse development. AEG-1 was expressed in mid-to-hindbrain, fronto-nasal processes, limbs, and pharyngeal arches in the early developmental period from E8.5 to E9.5. In addition, at stages of E12.5-E18.5 AEG-1 was localized in the brain, and olfactory and skeletal systems suggesting a role in neurogenesis, as well as in skin, including hair follicles, and in the liver, which are organ sites in which AEG-1 has been implicated in tumor development and progression. AEG-1 co-localized with Ki-67, indicating a role in cell proliferation, as previously revealed in tumorigenesis. Taken together, these results suggest that AEG-1 may play a prominent role during normal mouse development in the context of cell proliferation as well as differentiation, and that temporal regulation of AEG-1 expression may be required during specific stages and in specific tissues during development.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-β (TGF-β) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-β signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-β pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-β signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-β signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-β signaling for the treatment of human cancers.

A role for TGFbeta signaling in the pathogenesis of psoriasis

Deregulation of transforming growth factor-beta (TGFbeta) signaling has been reported in human psoriasis. Our recent study using a keratin 5 promoter (K5.TGFbeta1(wt)) showed that transgenic mice expressing wild-type TGFbeta1 in the epidermis developed severe skin inflammation. Additional experimental data further support a direct role for TGFbeta1 overexpression in skin inflammation. First, we temporally induced TGFbeta1 expression in keratinocytes in our gene-switch TGFbeta1(wt) transgenic mice and found inflammation severity correlated with TGFbeta1(wt) transgene expression. Second, deletion of T cells in K5.TGFbeta1(wt) mice significantly delayed skin inflammation and associated epidermal hyperplasia/hyperkeratosis. Third, therapeutic approaches effective for human psoriasis, that is, Etanercept and Rosiglitazone, are effective in alleviating the symptoms observed in K5.TGFbeta1(wt) mice. Future studies will analyze specific mechanisms and identify key factors in TGFbeta1-induced skin inflammation. Our mouse models will provide a useful tool for understanding the molecular mechanisms of inflammatory skin disorders in which TGFbeta1 is overexpressed.

Bone morphogenetic protein antagonist noggin promotes skin tumorigenesis via stimulation of the Wnt and Shh signaling pathways

Bone morphogenetic proteins (BMPs) play pivotal roles in the regulation of skin development. To study the role of BMPs in skin tumorigenesis, BMP antagonist noggin was used to generate keratin 14-targeted transgenic mice. In contrast to wild-type mice, transgenic mice developed spontaneous hair follicle-derived tumors, which resemble human trichofolliculoma. Global gene expression profiles revealed that in contrast to anagen hair follicles of wild-type mice, tumors of transgenic mice showed stage-dependent increases in the expression of genes encoding the selected components of Wnt and Shh pathways. Specifically, expression of the Wnt ligands increased at the initiation stage of tumor formation, whereas expression of the Wnt antagonist and tumor suppressor Wnt inhibitory factor-1 decreased, as compared with fully developed tumors. In contrast, expression of the components of Shh pathway increased in fully developed tumors, as compared with the tumor placodes. Consistent with the expression data, pharmacological treatment of transgenic mice with Wnt and Shh antagonists resulted in the stage-dependent inhibition of tumor initiation, and progression, respectively. Furthermore, BMP signaling stimulated Wnt inhibitory factor-1 expression and promoter activity in cultured tumor cells and HaCaT keratinocytes, as well as inhibited Shh expression, as compared with the corresponding controls. Thus, tumor suppressor activity of the BMPs in skin epithelium depends on the local concentrations of noggin and is mediated at least in part via stage-dependent antagonizing of Wnt and Shh signaling pathways.

Characterization of mammary epithelial cell line HC11 using the NIA 15k gene array reveals potential regulators of the undifferentiated and differentiated phenotypes

Differentiation of undifferentiated mammary epithelial stem and/or progenitor cells results in the production of luminal-ductal and myoepithelial cells in the young animal and upon pregnancy, the production of luminal alveolar cells. A few key regulators of differentiation have been identified, though it is not known yet how these proteins function together to achieve their well-orchestrated products. In an effort to identify regulators of early differentiation, we screened the NIA 15k gene array of 15,247 developmentally expressed genes using mouse mammary epithelial HC11 cells as a model of differentiation. We have confirmed a number of genes preferentially expressed in the undifferentiated cells (Lgals1, Ran, Jam-A and Bmpr1a) and in those induced to undergo differentiation (Id1, Nfkbiz, Trib1, Rps21, Ier3). Using antibodies to the proteins encoded by Lgals1, and Jam-A, we confirmed that their proteins levels were higher in the undifferentiated cells. Although the amounts of bone morphogenetic protein receptor-1A (BMPR1A) protein were present at all stages, we found the activity of its downstream signal transduction pathway, as measured by the presence of phosphorylated-SMAD1, -SMAD5, and -SMAD8, is elevated in undifferentiated cells and decreases in fully differentiated cells. This evidence supports that the BMPR1A pathway functions primarily in undifferentiated mammary epithelial cells. We have identified a number of genes, of known and unknown function, that are candidates for the maintenance of the undifferentiated phenotype and for early regulators of mammary alveolar cell differentiation.

Signal transduction molecules as targets for cancer prevention

Environmental and life-style aspects are major contributors to human carcinogenesis and, therefore, many human cancers may be preventable. Cancer is the end result of defects in cellular signaling processes that play a key role in the control of cell growth, survival, division, and differentiation. Therefore, identifying molecular and cellular targets critical in cancer development and prevention is an area of intensive research, driving the development of highly specific small-molecule inhibitors. A major idea today is that cancer may be prevented or treated by targeting the products of specific cancer-related genes, frequently encoding signaling proteins or transcription factors. Participants in these joint conferences discussed their latest findings in the identification of promising molecular targets and the development of agents directed against these targets with the goal of effectively transitioning these into the clinical setting.