Interleukin-1-stimulated secretion of interleukin-8 and growth-related oncogene-alpha demonstrates greatly enhanced keratinocyte growth in human raft cultured epidermis

Cold Atmospheric Pressure Plasma: A Growing Paradigm in Diabetic Wound Healing-Mechanism and Clinical Significance

Diabetes is one of the most significant causes of death all over the world. This illness, due to abnormal blood glucose levels, leads to impaired wound healing and, as a result, foot ulcers. These ulcers cannot heal quickly in diabetic patients and may finally result in amputation. In recent years, different research has been conducted to heal diabetic foot ulcers: one of them is using cold atmospheric pressure plasma. Nowadays, cold atmospheric pressure plasma is highly regarded in medicine because of its positive effects and lack of side effects. These conditions have caused plasma to be considered a promising technology in medicine and especially diabetic wound healing because studies show that it can heal chronic wounds that are resistant to standard treatments. The positive effects of plasma are due to different reactive species, UV radiation, and electromagnetic fields. This work reviews ongoing cold atmospheric pressure plasma improvements in diabetic wound healing. It shows that plasma can be a promising tool in treating chronic wounds, including ones resulting from diabetes.

The response of soft tissue cells to Ti implants is modulated by blood-implant interactions

Titanium-based dental implants have been highly optimized to enhance osseointegration, but little attention has been given to the soft tissue-implant interface, despite being a major contributor to long term implant stability. This is strongly linked to a lack of model systems that enable the reliable evaluation of soft tissue-implant interactions. Current in vitro platforms to assess these interactions are very simplistic, thus suffering from limited biological relevance and sensitivity to varying implant surface properties. The aim of this study was to investigate how blood-implant interactions affect downstream responses of different soft tissue cells to implants in vitro, thus taking into account not only the early events of blood coagulation upon implantation, but also the multicellular nature of soft tissue. For this, three surfaces (smooth and hydrophobic; rough and hydrophobic; rough and hydrophilic with nanostructures), which reflect a wide range of implant surface properties, were used to study blood-material interactions as well as cell-material interactions in the presence and absence of blood. Rough surfaces stimulated denser fibrin network formation compared to smooth surfaces and hydrophilicity accelerated the rate of blood coagulation compared to hydrophobic surfaces. In the absence of blood, smooth surfaces supported enhanced attachment of human gingival fibroblasts and keratinocytes, but limited changes in gene expression and cytokine production were observed between surfaces. In the presence of blood, rough surfaces supported enhanced fibroblast attachment and stimulated a stronger anti-inflammatory response from macrophage-like cells than smooth surfaces, but only smooth surfaces were capable of supporting long-term keratinocyte attachment and formation of a layer of epithelial cells. These findings indicate that surface properties not only govern blood-implant interactions, but that this can in turn also significantly modulate subsequent soft tissue cell-implant interactions.

Enhanced growth factor expression in chronic diabetic wounds treated by cold atmospheric plasma

AIMS

Cold atmospheric plasma (CAP) has been proven to enhance wound healing in superficial, chronically infected, diabetic foot ulcers. We aimed to investigate the molecular drivers responsible for this macroscopically observed improvement in diabetic wound healing.

METHODS

Wound exudate was available from each change of dressing within a prospective, randomised, patient-blinded clinical trial. Specific protein level analyses were conducted via multiplex ELISA for wound samples of a representative subcohort (placebo: n = 13; CAP: n = 14). Expression of fibroblast growth factor 2 (FGF-2), vascular endothelial growth factor A (VEGF-A), cytokines and matrix metalloproteinases (MMPs) were evaluated over a treatment period of about 14 days.

RESULTS

Analysis revealed increased levels of the growth factors FGF-2 (placebo: median 46.9 range [32.0-168.6] AU vs. CAP: 113.7[55.8-208.1] AU) and VEGF-A (placebo: 79.7 [52.4-162.7] AU vs. CAP: 120.8 [51.1-198.1] AU) throughout the treatment period and in head-to-head comparison in a daily assessment. CAP-treated wounds showed increased levels of tumour necrosis factor-alpha, interleukins 1α and 8. However, the total protein amounts were not significantly elevated. The total protein amounts of MMPs were not altered by CAP.

CONCLUSIONS

Induction of crucial growth factors, like FGF-2 and VEGF-A, and interleukins appears to be an important component of CAP-mediated promotion of granulation, vascularisation and reepithelialisation in the diabetic foot. These findings demonstrate for the first time that CAP-mediated growth factor induction also occurs in persons with diabetes, as previously described only in several in vitro and rodent experiments. Clinical Trial registration KPWTRIAL: NCT04205942, ClinicalTrials.gov.

Identification of Keratinocyte Mitogens: Implications for Hyperproliferation in Psoriasis and Atopic Dermatitis

Psoriasis and atopic dermatitis are chronic inflammatory skin diseases characterized by keratinocyte (KC) hyperproliferation and epidermal acanthosis (hyperplasia). The milieu of disease-associated cytokines and soluble factors is considered a mitogenic factor; however, pinpointing the exact mitogens in this complex microenvironment is challenging. We employed organotypic human epidermal equivalents, faithfully mimicking native epidermal proliferation and stratification, to evaluate the proliferative effects of a broad panel of (literature-based) potential mitogens. The KC GF molecule, the T-helper 2 cytokines IL-4 and IL-13, and the psoriasis-associated cytokine IL-17A caused acanthosis by hyperplasia through a doubling in the number of proliferating KCs. In contrast, IFN-γ lowered proliferation, whereas IL-6, IL-20, IL-22, and oncostatin M induced acanthosis not by hyperproliferation but by hypertrophy. The T-helper 2‒cytokine‒mediated hyperproliferation was Jak/signal transducer and activator of transcription 3 dependent, whereas IL-17A and KC GF induced MAPK/extracellular signal‒regulated kinase kinase/extracellular signal‒regulated kinase‒dependent proliferation. This discovery that key regulators in atopic dermatitis and psoriasis are direct KC mitogens not only adds evidence to their crucial role in the pathophysiological processes but also highlights an additional therapeutic pillar for the mode of action of targeting biologicals (e.g., dupilumab) or small-molecule drugs (e.g., tofacitinib) by the normalization of KC turnover within the epidermal compartment.

Cancer-associated fibroblasts induce an aggressive phenotypic shift in non-malignant breast epithelial cells via interleukin-8 and S100A8

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment have been associated with tumor progression in breast cancer. Although crosstalk between breast cancer cells and CAFs has been studied, the effect of CAFs on non-neoplastic breast epithelial cells is not fully understood to date. Here, we investigated the effect of CAFs on aggressive phenotypes in non-neoplastic MCF10A breast epithelial cells. CAFs induced epithelial-to-mesenchymal transition (EMT) and invasive phenotype in MCF10A cells. S100A8, a potential prognostic marker in several cancers, was markedly increased in MCF10A cells by CAFs. S100A8 was crucial for CAFs-induced invasive phenotype of MCF10A cells. Among cytokines increased by CAFs, interleukin (IL)-8 induced S100A8 through transcription factors p65 NF-κB and C/EBPβ. In a xenograft mouse model with MCF10A cells and CAFs, tumor was not developed, suggesting that coinjection with CAFs may not be sufficient for in vivo tumorigenicity of MCF10A cells. Xenograft mouse tumor models with MDA-MB-231 breast carcinoma cells provided an in vivo evidence for the effect of CAFs on breast cancer progression as well as a crucial role of IL-8 in tumor growth and S100A8 expression in vivo. Using a tissue microarray of human breast cancer, we showed that S100A8 expression was correlated with poor outcomes. S100A8 expression was more frequently detected in cancer-adjacent normal human breast tissues than in normal breast tissues. Together, this study elucidated a novel mechanism for the acquisition of invasive phenotype of non-neoplastic breast cells induced by CAFs, suggesting that targeting IL-8 and S100A8 may be an effective strategy against breast cancer.

Peroxisomal Fatty Acid Oxidation and Glycolysis Are Triggered in Mouse Models of Lesional Atopic Dermatitis

Alterations of the lipid profile of the stratum corneum have an important role in the pathogenesis of atopic dermatitis (AD) because they contribute to epidermal barrier impairment. However, they have not previously been envisioned as a cellular response to altered metabolic requirements in AD epidermis. In this study, we report that the lipid composition in the epidermis of flaky tail, that is, ft/ft mice mimics that of human lesional AD (ADL) epidermis, both showing a shift toward shorter lipid species. The amounts of C24 and C26 free fatty acids and C24 and C26 ceramides-oxidized exclusively in peroxisomes-were reduced in the epidermis of ft/ft mice despite increased lipid synthesis, similar to that seen in human ADL edpidermis. Increased ACOX1 protein and activity in granular keratinocytes of ft/ft epidermis, altered lipid profile in human epidermal equivalents overexpressing ACOX1, and increased ACOX1 immunostaining in skin biopsies from patients with ADL suggest that peroxisomal β-oxidation significantly contributes to lipid signature in ADL epidermis. Moreover, we show that increased anaerobic glycolysis in ft/ft mouse epidermis is essential for keratinocyte proliferation and adenosine triphosphate synthesis but does not contribute to local inflammation. Thus, this work evidenced a metabolic shift toward enhanced peroxisomal β-oxidation and anaerobic glycolysis in ADL epidermis.

Clinical and Instrumental Exploration of Sensitive Skin in a Pediatric Population

Studies on sensitive skin pathophysiology in infants are challenging because most assessment methods require self-reporting of signs. In this study, we aimed to identify and characterize sensitive skin in children for the first time. A newly developed parent-reported questionnaire was used to recruit children with sensitive skin. This questionnaire was also tested on an adult group. Hydration, transepidermal water loss (TEWL), and inflammatory markers (cytokines, and polyunsaturated fatty acids (PUFAs)) were quantified. A total of 77 children and 20 adults (33 and 10 with sensitive skin, respectively) were recruited. The groups with sensitive skin had more clinical signs of skin dryness. Skin hydration was lower in children in the sensitive compared with the nonsensitive skin group. TEWL levels were similar between sensitive and nonsensitive subjects in both infant and adult groups. Sensitive skin exhibited higher levels of cytokines and proinflammatory PUFAs as well as lower levels of anti-inflammatory PUFAs. Sensitive skin syndrome was associated with normal skin barrier function but lower hydration in infants and children. The higher levels of proinflammatory markers suggest that sensitive skin is associated with low-level inflammation. It is hypothesized, for the first time, that PUFAs are involved in sensitive skin syndrome in infants.

Paracrine Interaction of Cancer Stem Cell Populations Is Regulated by the Senescence-Associated Secretory Phenotype (SASP)

Dyskeratosis congenita is a telomere DNA damage syndrome characterized by defective telomere maintenance, bone marrow failure, and increased head and neck cancer risk. The Pot1b^-/-;Terc^+/- mouse exhibits some features of dyskeratosis congenita, but head and neck cancer was not reported in this model. To model the head and neck cancer phenotype, we created unique Pot1b- and p53-null-mutant models which allow genetic lineage tracing of two distinct stem cell populations. Loss of Pot1b expression depleted stem cells via ATR/Chk1/p53 signaling. Tumorigenesis was inhibited in Pot1b^-/-;p53^+/+ mice due to cellular senescence. Pot1b^-/-;p53^-/- tumors also exhibited senescence, but proliferated and metastasized with expansion of Lgr6⁺ stem cells indicative of senescence-associated secretory phenotype. Selective depletion of the small K15⁺ stem cell fraction resulted in reduction of Lgr6⁺ cells and inhibition of tumorigenesis via senescence. Gene expression studies revealed that K15⁺ cancer stem cells regulate Lgr6⁺ cancer stem cell expansion via chemokine signaling. Genetic ablation of the chemokine receptor Cxcr2 inhibited cancer stem cell expansion and tumorigenesis via senescence. The effects of chemokines were primarily mediated by PI3K signaling, which is a therapeutic target in head and neck cancer. IMPLICATIONS: Paracrine interactions of cancer stem cell populations impact therapeutic options and patient outcomes.

TIMP3 is a CLOCK-dependent diurnal gene that inhibits the expression of UVB-induced inflammatory cytokines in human keratinocytes

As the outermost physical barrier of an organism, the skin is diurnally exposed to UV radiation (UVR). Recent studies have revealed that the skin exhibits a circadian rhythm in various functions, and this oscillation is disturbed and reset via a strong environmental cue, the UVR. However, a molecular link between circadian perturbation by UVR and UVR-induced cellular responses has not been investigated. We identified tissue inhibitor of metalloproteinase (TIMP)-3 as a novel circadian locomotor output cycles kaput (CLOCK)–dependent diurnal gene by using a CLOCK-knockdown strategy in human keratinocytes. Among dozens of identified transcripts down-regulated by CLOCK knockdown, TIMP3 displayed a rhythmic expression in a CLOCK-dependent manner, in which the expression of matrix metalloproteinase (MMP)-1 and inflammatory cytokines, such as TNF-α, chemokine (C-X-C motif) ligand (CXCL)-1, and IL-8, were inversely regulated. Upon UVB exposure, the expression of CLOCK and TIMP3 was down-regulated, which led to an up-regulation of secretion of MMP1 and TNF-α proteins and in the transcription of CXCL1 and IL-8via CCAAT-enhancer binding protein (C/EBP)-α. UVB-induced TNF-α secretion increased further or decreased by knockdown or overexpression of TIMP3, respectively, as well as by CLOCK. As a novel CLOCK-dependent diurnal gene, TIMP3 inhibits the expression of inflammatory cytokines that are up-regulated by UV irradiation in human keratinocytes. Thus, our work suggests a molecular link between circadian perturbation by UVR and UVR-induced inflammation.—Park, S., Kim, K., Bae, I.-H., Lee, S. H., Jung, J., Lee, T. R., Cho, E.-G. TIMP3 is a CLOCK-dependent diurnal gene that inhibits the expression of UVB-induced inflammatory cytokines in human keratinocytes.

CC and CXC Chemokines Patterns in Psoriasis Determined by Protein Array Method Were Influenced by Goeckerman’s Therapy

Goeckerman’s therapy (GT) of psoriasis is based on daily application of pharmacy grade coal tar on affected skin with subsequent exposure to UV light. The aim of this study was to evaluate the influence of Goeckerman’s therapy of psoriasis on the levels of proangiogenic chemokines ENA-78 (CXCL5, Epithelial Cell Derived Neutrophil Attractant- 78), GRO alpha (CXCL1, Growth-Related Oncogene), IL-8 (CXCL8, Interleukin-8), MCP-1 (CCL2, Monocyte Chemotactic (Chemoattractant) Protein 1) and RANTES (CCL5, Regulated on Activation of Normal T Cell Expressed and Secreted) in peripheral blood of 22 children’s patients with psoriasis. 22 otherwise healthy children serve as a control group. The serum levels of chemokines were determined by commercial membrane protein array technique (RayBiotech, USA). Efficacy of Goeckerman’s therapy was delineated by PASI score. Disease activity was significantly diminished by Goeckerman’s therapy (p<0.001). Serum levels of GRO alpha and MCP-1 in patients before GT were significantly higher than those measured in healthy blood donors (GRO alpha: p=0.0128 and MCP-1: p=0.0003). Serum levels of GRO alpha, MCP-1 and RANTES were significantly diminished by GT (GRO alpha: p=0.002, MCP-1: p=0.048 and RANTES: p=0.0131). Compared to the healthy controls, serum level of MCP-1 remained significantly increased in psoriasis patients after GT (p<0.0001). In conclusion, we found that the GT of psoriasis influenced the serum levels of proinflammatory and proangiogenic chemokines, especially GRO alpha, MCP-1 and RANTES. It could be the cause for decreased proangiogenic activity which is described after GT of psoriasis.

Exposure to Carbon Ions Triggers Proinflammatory Signals and Changes in Homeostasis and Epidermal Tissue Organization to a Similar Extent as Photons

The increasing application of charged particles in radiotherapy requires a deeper understanding of early and late side effects occurring in skin, which is exposed in all radiation treatments. We measured cellular and molecular changes related to the early inflammatory response of human skin irradiated with carbon ions, in particular cell death induction and changes in differentiation and proliferation of epidermal cells during the first days after exposure. Model systems for human skin from healthy donors of different complexity, i.e., keratinocytes, coculture of skin cells, 3D skin equivalents, and skin explants, were used to investigate the alterations induced by carbon ions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-B exposure. After exposure to ionizing radiation, in none of the model systems, apoptosis/necrosis was observed. Carbon ions triggered inflammatory signaling and accelerated differentiation of keratinocytes to a similar extent as X-rays at the same doses. High doses of carbon ions were more effective than X-rays in reducing proliferation and inducing abnormal differentiation. In contrast, changes identified following low-dose exposure (≤0.5 Gy) were induced more effectively after X-ray exposure, i.e., enhanced proliferation and change in the polarity of basal cells.

Chemokines in Wound Healing and as Potential Therapeutic Targets for Reducing Cutaneous Scarring

Significance: Cutaneous scarring is an almost inevitable end point of adult human wound healing. It is associated with significant morbidity, both physical and psychological. Pathological scarring, including hypertrophic and keloid scars, can be particularly debilitating. Manipulation of the chemokine system may lead to effective therapies for problematic lesions. Recent Advances: Rapid advancement in the understanding of chemokines and their receptors has led to exciting developments in the world of therapeutics. Modulation of their function has led to clinically effective treatments for conditions as diverse as human immunodeficiency virus and inflammatory bowel disease. Potential methods of targeting chemokines include monoclonal antibodies, small-molecule antagonists, interference with glycosaminoglycan binding and the use of synthetic truncated chemokines. Early work has shown promising results on scar development and appearance when the chemokine system is manipulated. Critical Issues: Chemokines are implicated in all stages of wound healing leading to the development of a cutaneous scar. An understanding of entirely regenerative wound healing in the developing fetus and how the expression of chemokines and their receptors change during the transition to the adult phenotype is central to addressing pathological scarring in adults. Future Directions: As our understanding of chemokine/receptor interactions and scar formation evolves it has become apparent that effective therapies will need to mirror the complexities in these diverse biological processes. It is likely that sophisticated treatments that sequentially influence multiple ligand/receptor interactions throughout all stages of wound healing will be required to deliver viable treatment options.

Wnt-3a-activated human fibroblasts promote human keratinocyte proliferation and matrix destruction

Aberrant Wnt regulation, detectable by nuclear translocation of beta-catenin, is a hallmark of many cancers including skin squamous cell carcinomas (SCCs). By analyzing primary human skin SCCs, we demonstrate that nuclear beta-catenin is not restricted to SCC cells but also detected in stromal fibroblasts, suggesting an important role for aberrant Wnt regulation also in the tumor microenvironment. When human keratinocytes and fibroblasts were treated with Wnt-3a, fibroblasts proved to be more responsive. Accordingly, Wnt-3a did not alter HaCaT cell functions in a cell-autonomous manner. However, when organotypic cultures (OTCs) were treated with Wnt-3a, HaCaT keratinocytes responded with increased proliferation. As nuclear beta-catenin was induced only in the fibroblasts, this argued for a Wnt-dependent, paracrine keratinocyte stimulation. Global gene expression analysis of Wnt-3a-stimulated fibroblasts identified genes encoding interleukin-8 (IL-8) and C-C motif chemokine 2 (CCL-2) as well as matrix metalloproteinase-1 (MMP-1) as Wnt-3a targets. In agreement, we show that IL-8 and CCL-2 were secreted in high amounts by Wnt-3a-stimulated fibroblasts also in OTCs. The functional role of IL-8 and CCL-2 as keratinocyte growth regulators was confirmed by directly stimulating HaCaT cell proliferation in conventional cultures. Most important, neutralizing antibodies against IL-8 and CCL-2 abolished the Wnt-dependent HaCaT cell hyperproliferation in OTCs. Additionally, MMP-1 was expressed in high amounts in Wnt-3a-stimulated OTCs and degraded the stromal matrix. Thus, our data show that Wnt-3a stimulates fibroblasts to secrete both keratinocyte proliferation-inducing cytokines and stroma-degrading metalloproteinases, thereby providing evidence for a novel Wnt deregulation in the tumor-stroma directly contributing to skin cancer progression.

Novel findings of Langerhans cells and interleukin-17 expression in relation to the acrosyringium and pustule in palmoplantar pustulosis

BACKGROUND

Palmoplantar pustulosis (PPP) is a chronic and intensely inflammatory skin disease with pustules, erythema and scaling localized to the palms and soles. To date, no specific treatment is known. Earlier findings indicate the acrosyringium as the target for the inflammation.

OBJECTIVES

To identify specific features of the PPP inflammatory cell infiltrate and mediators of inflammation, which might provide insight into the pathogenesis and possible future treatment of the disease.

METHODS

Skin biopsies were taken from 23 patients with typical PPP (23 from involved skin and seven from noninvolved skin) and from 18 healthy controls (10 nonsmokers, eight smokers). Cell infiltrates and inflammation mediators were studied with immunohistochemistry.

RESULTS

A strong inflammation was observed in lesional skin of PPP. Our main findings of Langerhans cells and interleukin-17 close to or in the acrosyringium differs from findings in psoriasis vulgaris. Other inflammatory cells such as CD4+, CD8+, regulatory T cells and CD11a+ cells were also accumulated close to the sweat duct in epidermis and papillary dermis. More CD4+, CD8+, Langerhans cells, plasmacytoid dendritic cells and a higher proportion of regulatory T cells/CD3+ cells were seen in noninvolved palmar skin from patients with PPP compared with healthy controls.

CONCLUSIONS

Our novel findings indicate that the inflammation in PPP is initiated by the 'stand-by' innate immune system at the acrosyringium.

Gene expression profiling defines the role of ATP-exposed keratinocytes in skin inflammation

BACKGROUND

Various environmental stimuli, e.g., mechanical stress, osmolarity change, oxidative stress, and microbial products trigger ATP release from cells. It is well known that ATP regulates cell growth, differentiation, terminal differentiation, and cell-to-cell communication in keratinocytes. Moreover, extracellular ATP stimulates the expression and release of IL-6 and modulates the production several chemokines by keratinocytes.

OBJECTIVE

To investigate the role of ATP-stimulated keratinocytes in skin inflammation and immune response.

METHODS

We identified genes whose expression is augmented in ATP-stimulated human keratinocytes by DNA microarray. These microarray data were validated by quantitative real-time RT-PCR. Furthermore, we confirmed the observed mRNA change at protein level by ELISA and Western blotting.

RESULTS

The statistical analysis of the microarray data revealed that, besides IL-6, the expression of several novel genes such as IL-20, CXCL1-3, and ATF3 was significantly augmented in ATP-stimulated keratinocytes. These data was validated by quantitative real-time RT-PCR. We also confirmed the augmented production of IL-6, IL-20, CXCL1 by ELISA and that of ATF3 by Western blotting. Since both IL-6 and IL-20 that can stimulate STAT3 were produced by the ATP-stimulated keratinocytes, we examined their phosphorylation of STAT3. The study demonstrated biphasic activation of STAT3 after ATP stimulation, which was composed of a first peak at 1-2 h and a second peak at 12-24 h. The latter peak was significantly suppressed by anti-IL-6 antibody.

CONCLUSION

These studies characterized (1) STAT3 activation, (2) chemotaxis for neutrophils via CXCL1-3, and (3) ATF3 activation as possible roles of ATP-stimulated keratinocytes in skin inflammation and immune response.

Regulation of epithelial-mesenchymal IL-1 signaling by PPARbeta/delta is essential for skin homeostasis and wound healing

Skin morphogenesis, maintenance, and healing after wounding require complex epithelial–mesenchymal interactions. In this study, we show that for skin homeostasis, interleukin-1 (IL-1) produced by keratinocytes activates peroxisome proliferator–activated receptor β/δ (PPARβ/δ) expression in underlying fibroblasts, which in turn inhibits the mitotic activity of keratinocytes via inhibition of the IL-1 signaling pathway. In fact, PPARβ/δ stimulates production of the secreted IL-1 receptor antagonist, which leads to an autocrine decrease in IL-1 signaling pathways and consequently decreases production of secreted mitogenic factors by the fibroblasts. This fibroblast PPARβ/δ regulation of the IL-1 signaling is required for proper wound healing and can regulate tumor as well as normal human keratinocyte cell proliferation. Together, these findings provide evidence for a novel homeostatic control of keratinocyte proliferation and differentiation mediated via PPARβ/δ regulation in dermal fibroblasts of IL-1 signaling. Given the ubiquitous expression of PPARβ/δ, other epithelial–mesenchymal interactions may also be regulated in a similar manner.

Bombesin: a possible role in wound repair

During tissue regeneration and wound healing of the skin, migration, proliferation and differentiation of keratinocytes are important processes. Here we assessed the effect of a neuropeptide, bombesin, on keratinocytes during regeneration from scratch wounding. Bombesin purified from amphibian skin, is homologous of mammalian gastrin-releasing peptide and is active in mammals. Its pharmacological effects mediate various physiological activities: hypertensive action, stimulating action on gastric secretion, hyperglycemic effect or increased insulin secretion. In vitro it shows a hyperproliferative effect on different experimental models and is involved in skin repair. The aim of this study was to elucidate the effect of Bombesin in an in vitro experimental model on a mechanically injured human keratinocyte monolayer. We evaluated different mediators involved in wound repair such as IL-8, TGFbeta, IL-1, COX-2, VEGF and Toll-like receptors 2 and 4 (TLR2 and TLR4). We also studied the effects of bombesin on cell proliferation and motility and its direct effect on wound repair by observing the wound closure after mechanical injury. The involvement of the bombesin receptors neuromedin receptor (NMBR) and gastrin-releasing peptide receptor (GRP-R) was also evaluated. Our data suggest that bombesin may have an important role in skin repair by regulating the expression of healing markers. It enhanced the expression of IL-8, TGFbeta, COX-2 and VEGF. It also enhanced the expression of TLR2, while TLR4 was not expressed. Bombesin also increased cell growth and migration. In addition, we showed that NMBR was more involved in our experimental model compared to GRP-R.

Transcriptional responses of human epidermal keratinocytes to cytokine interleukin-1

Interleukin-1 is a proinflammatory and immunomodulatory cytokine that plays a crucial role in inflammatory diseases of the skin, including bacterial infections, bullous diseases, UV damage, and especially psoriasis. To characterize the molecular effects of IL-1 in epidermis, we defined the transcriptional changes in human epidermal keratinocytes 1, 4, 24, and 48 h after treatment with IL-1alpha. IL-1 significantly regulated 388 genes, including genes associated with proteolysis, adhesion, signal transduction, proliferation, and epidermal differentiation. IL-1 induces many genes that have antimicrobial function. Secreted cytokines, chemokines, growth factors, and their receptors are the prominent targets of IL-1 regulation, including IL-8, IL-19, elafin, C3, and S100A proteins, which implicate IL-1 in the pathogenesis of inflammatory diseases. IL-1 induced not only proliferation-associated genes but also differentiation marker genes such as transglutaminase-1 and involucrin, which suggests that IL-1 plays an important role in the aberrant proliferation and differentiation seen in psoriasis. Correlation of IL-1 regulated genes with the TNFalpha and IFNgamma regulated ones showed more similarities between IL-1 and TNFalpha than IL-1 and IFNgamma, whereas Oncostatin-M (OsM) affected a largely unrelated set of genes. IL-1 regulates many genes previously shown to be specifically over-expressed in psoriasis. In summary, IL-1 regulates a characteristic set of genes that define its specific contribution to inflammation and aberrant differentiation in skin diseases.

Cytokine and chemokine release upon prolonged mechanical loading of the epidermis

At this moment, pressure ulcer risk assessment is dominated by subjective measures and does not predict pressure ulcer development satisfactorily. Objective measures are, therefore, needed for an early detection of these ulcers. The current in vitro study evaluates cytokines and chemokines [interleukin 1alpha (IL-1alpha), interleukin 1 receptor antagonist (IL-1RA), tumor necrosis factor alpha (TNF-alpha) and interleukin 8 (CXCL8/IL-8)] as early markers for mechanically-induced epidermal damage. Various degrees of epidermal damage were induced by subjecting commercially available epidermal equivalents (EpiDerm) to increasing pressures (0, 50, 75, 100, 150, and 200 mmHg) for 24 h, using a loading device. At the end of the loading experiment, tissue damage was assessed by histological examination and by evaluation of the cell membrane integrity. Cytokines and chemokines were determined in the culture supernatant. Sustained epidermal loading resulted in an increased release of IL-1alpha, IL-1RA, TNF-alpha and CXCL8/IL-8. This was first observed at 75 mmHg, when the tissue was only slightly damaged. Swollen cells, vacuoles, necrosis and affected cell membranes were observed at pressures higher than 75 mmHg. Furthermore, at 150 and 200 mmHg, the cells in the lower part of the epidermis were severely compressed. In conclusion, IL-1alpha, IL-1RA, TNF-alpha and CXCL8/IL-8 are released in vitro as a result of sustained mechanical loading of the epidermis. The first increase in cytokines and chemokines was observed when the epidermal tissue was only slightly damaged. Therefore, these cytokines and chemokines are potential markers for the objective, early detection of mechanically-induced skin damage, such as pressure ulcers.

Transcriptional signature of epidermal keratinocytes subjected to in vitro scratch wounding reveals selective roles for ERK1/2, p38, and phosphatidylinositol 3-kinase signaling pathways

Covering denuded dermal surfaces after injury requires migration, proliferation, and differentiation of skin keratinocytes. To clarify the major traits controlling these intermingled biological events, we surveyed the genomic modifications occurring during the course of a scratch wound closure of cultured human keratinocytes. Using a DNA microarray approach, we report the identification of 161 new markers of epidermal repair. Expression data, combined with functional analysis performed with specific inhibitors of ERK, p38(MAPK) and phosphatidylinositol 3-kinase (PI3K), demonstrate that kinase pathways exert very selective functions by precisely controlling the expression of specific genes. Inhibition of the ERK pathway totally blocks the wound closure and inactivates many early transcription factors and EGF-type growth factors. p38(MAPK) inhibition only delays "healing," probably in line with the control of genes involved in the propagation of injury-initiated signaling. In contrast, PI3K inhibition accelerates the scratch closure and potentiates the scratch-dependent stimulation of three genes related to epithelial cell transformation, namely HAS3, HBEGF, and ETS1. Our results define in vitro human keratinocyte wound closure as a repair process resulting from a fine balance between positive signals controlled by ERK and p38(MAPK) and negative ones triggered by PI3K. The perturbation of any of these pathways might lead to dysfunction in the healing process, similar to those observed in pathological wounding phenotypes, such as hypertrophic scars or keloids.

Regulation of UVB-Induced IL-8 and MCP-1 Production in Skin Keratinocytes by Increasing Vitamin C Uptake via the Redistribution of SVCT-1 from the Cytosol to the Membrane

It is well known that UVB (290-320 nm) induces inflammation in skin by the transcription and release of cytokines and chemokines from skin keratinocytes. In addition, it is considered that intracellular reactive oxygen species (ROS) plays an important role in UVB-induced inflammatory response in the skin. Therefore, we investigated the effect of vitamin C, a potent antioxidant, on the regulation of UVB-induced skin inflammation via the modulation of chemokines production. Vitamin C uptake into keratinocytes is increased by UVB irradiation in a time- and dose-dependent manner through the translocation of sodium-dependent vitamin C transporter-1 (SVCT-1), a vitamin C-specific transporter, from the cytosol to the membrane. To evaluate the effect of vitamin C on the chemokine mRNA expression, we performed RNase protection assay. As a result, there was a remarkable change in chemokine mRNA expression, especially IL-8 and monocyte chemoattractant protein (MCP)-1 expression. In addition, increased IL-8 and MCP-1 mRNA expressions were suppressed by vitamin C treatment. We also confirmed the results of protein levels measured by ELISA. Taken together, vitamin C uptake is increased in UVB-irradiated keratinocytes through the translocation of SVCT-1 and regulates inflammatory response in the skin via the downregulation of IL-8 and MCP-1 production.

Serine Protease Signaling of Epidermal Permeability Barrier Homeostasis

Evidence is growing that protease-activated receptor-2 (PAR-2) plays a key role in epithelial inflammation. We hypothesized here that PAR-2 plays a central role in epidermal permeability barrier homeostasis by mediating signaling from serine proteases (SP) in the stratum corneum (SC). Since the SC contains tryptic- and chymotryptic-like activity, we assessed the influence of SP activation/inhibition on barrier function. Acute barrier disruption increases SP activity and blockade by topical SP inhibitors (SPI) accelerates barrier recovery after acute abrogation. This improvement in barrier function is due to accelerated lamellar body (LB) secretion. Since tryptic SP signal certain downstream responses through PAR-2, we assessed its potential role in mediating the negative effects of SP on permeability barrier. Firstly, PAR-2 is expressed in the outer nucleated layers of the epidermis and most specifically under basal condition to the lipid raft (LR) domains. Secondly, tape stripping-induced barrier abrogation provokes PAR-2 activation, as shown by receptor internalization (i.e. receptor movement from LR to cytolpasmic domains). Thirdly, topical applications of PAR-2 agonist peptide, SLIGRL, delay permeability barrier recovery and inhibit LB secretion, while, conversely, PAR-2 knockout mice display accelerated barrier recovery kinetics and enhanced LB secretion, paralleled by increased LR formation and caveolin-1 expression. These results demonstrate first, the importance of SP/SPI balance for normal permeability barrier homeostasis, and second, they identify PAR-2 as a novel signaling mechanism of permeability barrier, that is, of response linked to LB secretion.

Comparison of gene expression of umbilical cord vein and bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) give origin to the marrow stromal environment that supports hematopoiesis. These cells present a wide range of differentiation potentials and a complex relationship with hematopoietic stem cells (HSCs) and endothelial cells. In addition to bone marrow (BM), MSCs can be obtained from other sites in the adult or the fetus. We isolate MSCs from the umbilical cord (UC) veins that are morphologically and immunophenotpically similar to MSCs obtained from the BM. In culture, these cells are capable of differentiating in vitro into adipocytes, osteoblasts, and condrocytes. The gene expression profiles of BM-MSCs and of UC-MSCs were compared by serial analysis of gene expression, then validated by reverse transcription polymerase chain reaction of selected genes. The two lineages shared almost all of the first thousand most expressed transcripts, including vimentin, galectin 1, osteonectin, collagens, transgelins, annexin A2, and MMP2. Nevertheless, a set of genes related to antimicrobial activity and to osteogenesis was more expressed in BM-MSCs, whereas higher expression in UC-MSCs was observed for genes that participate in pathways related to matrix remodeling via metalloproteinases and angiogenesis. Finally, cultured endothelial cells, CD34+ HSCs, MSCs, blood leukocytes, and bulk BM clustered together, separated from seven other normal nonhematopoietic tissues, on the basis of shared expressed genes. MSCs isolated from UC veins are functionally similar to BM-MSCs, but differentially expressed genes may reflect differences related to their sites of origin: BM-MSCs would be more committed to osteogenesis, whereas UC-MSCs would be more committed to angiogenesis.

Induction of cytokine (interleukin-1alpha and tumor necrosis factor-alpha) and chemokine (CCL20, CCL27, and CXCL8) alarm signals after allergen and irritant exposure

The immune system is called into action by alarm signals generated from injured tissues. We examined the nature of these alarm signals after exposure of skin residential cells to contact allergens (nickel sulfate and potassium dichromate) and a contact irritant [sodium dodecyl sulfate (SDS)]. Nickel sulfate, potassium dichromate, and SDS were applied topically to the stratum corneum of human skin equivalents. A similar concentration-dependent increase in chemokine (CCL20, CCL27, and CXCL8) secretion was observed for all three chemicals. Exposure to nickel sulfate and SDS was investigated in more detail: similar to chemokine secretion, no difference was observed in the time- and concentration-dependent increase in pro-inflammatory cytokine [interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha)] secretion. Maximal increase in IL-1alpha secretion occurred within 2 h after exposure to both nickel sulfate and SDS and prior to increased chemokine secretion. TNF-alpha secretion was detectable 8 h after chemical exposure. After allergen or irritant exposure, increased CCL20 and CXCL8, but not CCL27, secretion was inhibited by neutralizing human antibodies to either IL-1alpha or TNF-alpha. Our data show that alarm signals consist of primary and secondary signals. IL-1alpha and TNF-alpha are released as primary alarm signals, which trigger the release of secondary chemokine (CCL20 and CXCL8) alarm signals. However, some chemokines, for example, CCL27 can be secreted in an IL-1alpha and TNF-alpha independent manner. Our data suggest that skin residential cells respond to both allergen and irritant exposure by releasing mediators that initiate infiltration of immune responsive cells into the skin.

Cathepsin D is involved in the regulation of transglutaminase 1 and epidermal differentiation

We previously demonstrated that the aspartate protease cathepsin D is activated by ceramide derived from acid sphingomyelinase. Increased expression of cathepsin D in the skin has been reported in wound healing, psoriasis and skin tumors. We explored specific functions of cathepsin D during epidermal differentiation. Protein expression and enzymatic activity of cathepsin D increased in differentiated keratinocytes in both stratified organotypic cultures and in mouse skin during epidermal barrier repair. Treatment of cultured keratinocytes with exogenous cathepsin D increased the activity of transglutaminase 1, known to cross-link the cornified envelope proteins involucrin and loricrin during epidermal differentiation. Inhibition of cathepsin D by pepstatin A suppressed the activity of transglutaminase 1. Cathepsin D-deficient mice revealed reduced transglutaminase 1 activity and reduced protein levels of the cornified envelope proteins involucrin and loricrin. Also, amount and distribution of cornified envelope proteins involucrin, loricrin, filaggrin, and of the keratins K1 and K5 were significantly altered in cathepsin D-deficient mice. Stratum corneum morphology in cathepsin D-deficient mice was impaired, with increased numbers of corneocyte layers and faint staining of the cornified envelope only, which is similar to the human skin disease lamellar ichthyosis. Our findings suggest a functional link between cathepsin D activation, transglutaminase 1 activity and protein expression of cornified envelope proteins during epidermal differentiation.

Eicosapentaenoic Acid and Docosahexaenoic Acid Reduce UVB- and TNF-α-induced IL-8 Secretion in Keratinocytes and UVB-induced IL-8 in Fibroblasts

Omega-3 polyunsaturated fatty acids (n-3 PUFA) inhibit ultraviolet B (UVB)-induced inflammation and other inflammatory states, in vivo. We examined whether this may be mediated by modulation of interleukin (IL)-8, a chemokine pivotal to skin inflammation induced by UVB, in epidermal and dermal cells. We also explored the ability of n-3 PUFA to protect against tumor necrosis factor (TNF)-alpha induction of IL-8, and assessed relative potencies of the principal dietary n-3 PUFA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Pre-supplementation, both HaCaT keratinocyte and CCD922SK fibroblast cell lines showed dose-responses for UVB-induced IL-8 release (p<0.001), assessed 48 h post-irradiation. Cells were supplemented with > or =90% purified EPA, DHA, oleic acid (OA) or vehicle control, for 4.5 d. EPA and DHA supplements were bioavailable to keratinocytes and fibroblasts. In keratinocytes, EPA and DHA were shown to reduce basal secretion of IL-8 by 66% and 63%, respectively (p<0.05), and UVB-induced levels by 66% and 65% at 48 h after 100 mJ per cm2, respectively, (p<0.01). A similar pattern occurred in fibroblasts, whereas OA had no influence on IL-8 release in either cell line. In addition, TNF-alpha-induced IL-8 secretion by keratinocytes was reduced by 54% and 42%, respectively, by EPA and DHA (p<0.001). Hence both n-3 PUFA inhibit production of UVB- and TNF-alpha-induced IL-8 in skin cells; this may be important in the photoprotective and other anti-inflammatory effects conferred by these agents.

Photodynamic therapy on keloid fibroblasts in tissue-engineered keratinocyte-fibroblast co-culture

BACKGROUND AND OBJECTIVES

Keloids are disfiguring, proliferative scars that are a pathologic response to cutaneous injury. An organotypic tissue culture system (the Raft model 1-10) was used to investigate the feasibility of using photodynamic therapy (PDT) as an adjunctive therapy to treat keloids following surgical excision. The Raft co-culture system mimics skin by layering keratinocytes on top of fibroblasts embedded in a collagen matrix. PDT uses drugs that produce singlet oxygen in situ when irradiated by light, and may lead to a number of effects in living tissues varying from the modulation of growth to apoptosis. PDT is already used to treat several benign and malignant diseases in organs such as the skin, retina, and esophagus.

STUDY DESIGN/MATERIALS AND METHODS

Normal adult, neonatal, and keloid fibroblasts and keratinocytes were isolated from skin obtained from patients undergoing elective procedures and used to construct the Rafts. Mature Rafts (after 4 days) were incubated with 5-amino levulinic acid (5-ALA), a photosensitizer, for 3 hours and were laser-irradiated (635 nm) for total energy delivery of 5 J/cm2, 10 J/cm2, or 20 J/cm2. Rafts were examined 24 hours and 14 days later. Cell viability was determined using confocal imaging combined with live-dead fluorescent dyes. Multi-photon microscope (MPM) imaged collagen structure and density. As Rafts contract over time, surface area was measured using optical micrometry daily.

RESULTS

At 10 and 20 J/cm2, near-total cell death was observed in all constructs, while at 5 J/cm2 cell viability was comparable to controls. Cell viability in keloid and neonatal Rafts was greater than that observed in normal adult Rafts. Treated Rafts contracted less over the 14-day period compared to controls. Contraction and collagen density were greatest in keloid and neonatal Rafts.

CONCLUSIONS

A PDT dosimetry range was established, which reduces tissue contraction and collagen density while minimizing injury to fibroblasts.

The macrophage-activating lipopeptide-2 accelerates wound healing in diabetic mice

Wound healing in healthy individuals proceeds at an optimal rate. However, in patients, with -- e.g.-- locally impaired blood flow or diabetes, chronic wounds develop and often become infected. Chronic wounds mean a low quality of life for the afflicted patients, not to mention enormous costs. Rather than using recombinant growth factors to accelerate wound healing, we employed the toll-like receptor agonist macrophage-activating lipopeptide-2 (MALP-2) to improve the healing of full-thickness excision skin wounds in an animal model with obese, diabetic mice. A gene array experiment suggested that MALP-2 stimulates the release of various mediators involved in wound healing. Further data to be presented in this study will show (i) that MALP-2 is capable of stimulating the appearance of the monocyte chemoattractant protein-1 at the wound site, (ii) that this leads to increased leucocyte and, in particular, macrophage infiltration and (iii) that MALP-2-treated wounds closed 2 weeks earlier than vehicle-treated controls. MALP-2, thus, appears to stimulate the early inflammatory process needed to set in motion the ensuing consecutive natural steps of wound healing resulting in wound closure.

The Development and Characterization of an In Vitro Model of Psoriasis

In this study, the phenotype of psoriatic keratinocytes and fibroblasts in reconstructed skin models was compared to those constructed from normal cells. Characterization of this model by immunohistochemistry showed that classical markers of keratinocyte differentiation exhibited similar patterns of distribution in the psoriatic models to those derived from normal cells and generally reflected in vivo observations. Some crucial differences, however, were observed between normal and psoriatic models when pro-inflammatory gene expression and keratinocyte proliferation were investigated. Notably, the chemokine receptor CXCR2 was overexpressed in the psoriatic models, and, moreover, was localized to the granular layer of keratinocytes as seen in psoriasis in vivo. Pro-inflammatory genes (tumor necrosis factor alpha [TNF-alpha], interferon gamma [IFN-gamma], and interleukin 8 [IL-8]) were expressed at high levels in the psoriatic models, but were only minimally expressed in the normal models. Models derived from uninvolved psoriatic skin showed the same gene expression profile as those derived from involved skin along with an increased proliferation rate when compared to normal models. These results suggest that psoriatic individuals possess an inherent predisposition to develop the disease phenotype even in the absence of T cells. This study represents a comprehensive characterization of psoriatic human skin reconstructed in vitro, and demonstrates the potential of this model as a valuable tool in drug discovery.

New advances on the functions of epidermal growth factor receptor and ceramides in skin cell differentiation, disorders and cancers

Recent advances in understanding of the biological functions of the epidermal growth factor and epidermal growth factor receptor (EGF-EGFR) system and ceramide production for the maintenance of skin integrity and barrier function are reported. In particular, the opposite roles of EGFR and ceramide cascades in epithelial keratinocyte proliferation, migration and terminal differentiation are described. Moreover, the functions of ceramides in the epidermal permeability barrier are reviewed. The alterations in EGFR signaling and ceramide metabolism, which might be involved in the etiopathogenesis of diverse skin disorders and cancers, are described. New progress in understanding of skin organization, which might provide the basis for the design of new transcutaneous drug delivery techniques as well as for the development of new therapies of skin disorders and cancers, are reported.