Dermatological aspects of angiogenesis

Isookanin Inhibits PGE2-Mediated Angiogenesis by Inducing Cell Arrest through Inhibiting the Phosphorylation of ERK1/2 and CREB in HMEC-1 Cells

Inflammation is increasingly recognized as a critical mediator of angiogenesis, and unregulated angiogenic responses often involve human diseases. The importance of regulating angiogenesis in inflammatory diseases has been demonstrated through some successful cases of anti-angiogenesis therapies in related diseases, including arthritis, but it has been reported that some synthetic types of antiangiogenic drugs have potential side effects. In recent years, the importance of finding alternative strategies for regulating angiogenesis has begun to attract the attention of researchers. Therefore, identification of natural ingredients used to prevent or treat angiogenesis-related diseases will play a greater role. Isookanin is a phenolic flavonoid presented in Bidens extract, and it has been reported that isookanin possesses some biological properties, including antioxidative and anti-inflammatory effects, anti-diabetic properties, and an ability to inhibit α-amylase. However, its antiangiogenic effects and mechanism thereof have not been studied yet. In this study, our results indicate that isookanin has an effective inhibitory effect on the angiogenic properties of microvascular endothelial cells. Isookanin shows inhibitory effects in multiple stages of PGE₂-induced angiogenesis, including the growth, proliferation, migration, and tube formation of microvascular endothelial cells. In addition, isookanin induces cell cycle arrest in S phase, which is also the reason for subsequent inhibition of cell proliferation. The mechanism of inhibiting angiogenesis by isookanin is related to the inhibition of PGE₂-mediated ERK1/2 and CREB phosphorylation. These findings make isookanin a potential candidate for the treatment of angiogenesis-related diseases.

Effectiveness of a 595-nm Pulsed Dye Laser for the Treatment of Basal Cell Carcinoma Using One Double-Stacked Pulse Session: A Randomized, Double-Blinded Controlled Trial

BACKGROUND

Surgical and nonsurgical methods are used for treating basal cell carcinoma (BCC). Few randomized controlled trials exist on the effectiveness of the pulsed dye laser (PDL) on BCC treatment.

OBJECTIVE

We investigated the effectiveness of PDL treatment in a single session for the management of nodular and superficial BCCs on the trunk and extremities of adults using a randomized, double-blind, controlled technique.

METHODS

We used settings of fluence 7.5 J/cm2, 3-ms pulse duration, no dynamic cooling, 10-mm spot size, 10% overlap between pulses, and 2 stacked pulses on a 595-nm wavelength laser. Histopathologic clearance on excision of tumor with 4-mm margins was the primary outcome measure.

RESULTS

Twenty-four patients were included in the study, with 14 in the laser treatment group and 10 patients in the sham/control group. In total, 10/14 (71.4%) of the tumors in the treatment group were successfully treated with no residual tumor on excisional specimen histology, compared with 3/10 (30.0%) of the control group (p = .045).

CONCLUSION

Our study shows that PDL may be an effective treatment for low-risk BCCs of the trunk and extremities, but the cure rate is lower than those of other treatments for BCC. Thus, PDL under the current settings cannot be recommended.

Vascular patterns in basal cell carcinoma: Dermoscopic, confocal and histopathological perspectives

Basal cell carcinoma (BCC) is the most prevalent skin cancer in the Caucasian population. A variety of different phenotypic presentations of BCC are possible. Although BCCs rarely metastasize, these tumors commonly destroy underlying tissues and should therefore be treated promptly. As vascular formation and angiogenesis are indicators of tumor development and progression, the presence of blood vessels, their morphology and architecture are important markers in skin lesions, providing critical information towards pathogenesis and diagnosis. BCC commonly lacks pigmentation, therefore it is important to emphasize the usefulness of vascular feature detection, recognition, quantification and interpretation. To answer the question of whether vascular patterns observed on dermoscopy, reflectance confocal microscopy (RCM) and histopathology might reflect the biologic behavior of BCCs, we undertook this review article. Several studies have sought, by various means, to identify vascular features associated with the more aggressive BCC phenotypes. Dermoscopic vascular pattern assessment can facilitate diagnostic discrimination between BCC subtypes, more aggressive BCCs displaying less or no pink coloration and a relative absence of central tumor vessels. RCM, a novel, non-invasive imaging technique, allows for the quantification of blood vessel size, density, and flow intensity in BCCs. BCCs are distinguished on RCM chiefly by vessels that branch and intertwine between neoplastic aggregates, a pattern strongly reflecting tumor neo-angiogenesis. The analysis of these vascular morphological and distribution patterns can provide further support in the diagnosis, assessment, or monitoring of BCCs. Histopathology shows significantly higher microvessel densities in the peritumoral stroma of BCCs, when compared to normal skin or benign tumors. This angiogenic response in the stroma is associated with local aggressiveness, therefore the quantification of peritumoralmicrovessels may further assist with tumor evaluation. How dermoscopy and RCM vascular patterns in BCC correlate with histopathological subtype and thus help in discriminating aggressive subtypes definitely deserves further investigation.

Correlation Between Microvessel Density and Morphological Features in Skin Squamous Cell Carcinoma

INTRODUCTION

Abnormal angiogenesis is described in tumor growth and it facilitates its metastatic spread. Tumors with high angiogenic activity belong to the category of aggressive tumors with poor prognosis for patients. The aim of this study was to determine the blood vessels density (BVD), i.e. neovascularization at the tumor invasive front in skin squamous cell carcinoma (SCC) in order to determine its possible role in the tumor progression, and to correlate it to the blood vessels density of healthy skin and with the prognostic parameters of the TNM classification: T status, depth of tumor invasion (DI) and tumor histological grade (G), which were also correlated between each other.

MATERIAL AND METHODS

The material consisted of surgical specimens obtained from 30 patients with skin SCC, who underwent surgery. Tissue samples were routinely processed by standard paraffin technique stained by Hematoxilin-Eosin and immunohistochemically with antibodies against smooth muscle actin (SMA) and CD34. The BVD in the invasive front of the neoplasms was correlated to the healthy skin, tumor status (pT), depth of invasion and grade of histological differentiation (pG).

RESULTS

The histological analysis has shown a high statistical difference in the density of blood vessels in SCC compared to the healthy skin and statistical difference in BVD in neoplasms with different depth of invasion and different grade of differentiation. The density of neovascularzation increased with the deeper invasion and the worse differentiation.

CONCLUSION

The increased vascularization at the invasive front of SCC with deeper invasion and worse differentiation has pointed out to its possible role in neoplasm progression.

Cost of Cutaneous Melanoma by Tumor Stage: A Descriptive Analysis

BACKGROUND AND OBJECTIVE

The basis for optimal resource allocation is an understanding of requirements during the diagnostic and treatment phases. Costs associated with the rising incidence of cutaneous melanoma are considerable. We undertook an up-to-date analysis of the cost of diagnosis, treatment, and follow-up according to tumor stage.

METHODS

We constructed descriptive tables following a theoretical model of direct costs based on amounts published in directives for the Spanish national health system and in international guidelines for managing cutaneous melanoma according to stage at diagnosis and clinical course. The tables allowed us to calculate the cost of treating individual patients as well as the expected cost for all patients with tumors in the same stage.

RESULTS

Individual patients would generate costs ranging from €1689 (for a stage I tumor) to €88, 268 (stage IV). The largest differences were between stages IA and IB-IIA and between stages III and IV. Costs differed greatly between patients with early-stage tumors and favorable outcomes and those with recurring tumors, which cost 50-fold more in the first year and 20-fold more after 10 years of follow-up.

CONCLUSIONS

The high cost of diagnosing advanced-stage cutaneous melanoma calls attention to the need to promote primary prevention and early detection. Our findings provide the knowledge base for cost-effectiveness studies in this disease.

Immunohistochemical Expression of Vascular Endothelial Growth Factor (VEGF) and C-KIT in Cutaneous Melanocytic Lesions

Vascular endothelial growth factor (VEGF) and C-KIT are involved in tumor progression in several human neoplasms. The aim of the present study has been to investigate their immunohistochemical expression in melanocytic lesions. We examined 11 compound nevi, 12 dysplastic nevi, and 18 melanomas. Immunostaining for VEGF was observed only in melanomas; c-kit expression was detected in melanomas (higher in radial than in vertical growth phase) and in nevi (predominantly in the junctional component). Our data indicate that assessment of VEGF expression might aid in the differential diagnosis between dysplastic nevi and melanomas. Moreover, VEGF might be a candidate for targeted therapy. The loss of c-kit expression might contribute to melanoma progression.

Anti-angiogenic activity of thienopyridine derivative LCB03-0110 by targeting VEGFR-2 and JAK/STAT3 Signalling

Vascular endothelial growth factor receptor-2 (VEGFR-2) and Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signalling are important for tumor angiogenesis and metastasis. In this study, we identified (3-(2-(3-(morpholinomethyl)phenyl)thieno[3,2-b]pyridin-7-ylamino)phenol (LCB03-0110) as a potent angiogenesis inhibitor. LCB03-0110 inhibited VEGFR-2 and JAK/STAT3 signalling in primary cultured human endothelial cells and cancer cells. An in vitro kinase assay and molecular modelling revealed that LCB03-0110 inhibited VEGFR-2, c-SRC and TIE-2 kinase activity via preferential binding at the ATP-binding site of their kinases. LCB03-0110 successfully occupied the hydrophobic pocket of VEGFR-2, c-SRC and TIE-2. LCB03-0110 also inhibited hypoxia-induced HIF/STAT3 and EGF- or angiopoietin-induced signalling cascades. In addition, LCB03-0110 inhibited VEGF-induced proliferation, viability, migration and capillary-like tube formation. LCB03-0110 also suppressed the sprouting of endothelial cells in the rat aorta and the formation of new blood vessels in the mouse Matrigel plug assay, but also suppressed pulmonary metastasis and tumor xenograft in mice. Our results suggest that LCB03-0110 is a potential candidate small molecule for blocking angiogenesis mediated by aberrant activation of VEGFR-2 and JAK/STAT3 signalling.

Quantitative comparison of angiogenesis and lymphangiogenesis in cutaneous lichen planus and psoriasis: immunohistochemical assessment

Recent experimental studies revealed that angiogenesis and lymphangiogenesis are closely related to chronic inflammation. The present study aims to evaluate quantitative changes of blood and lymphatic microcirculatory beds in cutaneous lichen planus (CLP) and psoriatic lesions using immunohistochemical analysis with antibodies to CD34, D2-40 and VEGF. Morphometric software was used to determine the area of blood and lymphatic vessels (BVA and LVA) and also the VEGF positive area. Statistical analysis of these parameters confirmed a significant enlargement of both the blood and lymphatic microcirculatory beds in psoriatic and CLP lesions. BVA in CLP lesions was increased by 56% however this augmentation was not as great as in psoriatic lesions where BVA was increased by 123%. Interestingly, LVA in psoriatic and CLP lesions was increased equally by 85%. The strongest VEGF expression was detected in psoriatic lesions, with lower, but still significant, overexpression in CLP lesions. VEGF-C was significantly increased in both psoriatic and CLP lesions in comparable level. Noticeably higher VEGF and VEGF-C expression was observed in the epidermis than in the dermis. Finally, our results indicate that the level of angiogenesis is considerably greater in psoriatic lesions than in CLP lesions, but the level of lymphangiogenesis is equal in both psoriatic and CLP lesions.

A novel role for microphthalmia-associated transcription factor-regulated pigment epithelium-derived factor during melanoma progression

Microphthalmia-associated transcription factor (MITF) acts via pigment epithelium-derived factor (PEDF), an antiangiogenic protein, to regulate retinal pigment epithelium migration. PEDF expression and/or regulation during melanoma development have not been investigated previously. Using immunohistochemistry, we determined expression of PEDF in common and dysplastic melanocytic nevi, melanoma in situ, invasive melanoma, and metastatic melanoma (n = 102). PEDF expression was consistently decreased in invasive and metastatic melanoma, compared with nevi and melanoma in situ (P < 0.0001). PEDF was lost in thicker melanomas (P = 0.003), and correlated with depth of invasion (P = 0.003) and distant metastasis (P = 0.0331), but only marginally with mitotic index, AJCC stage, nodal metastasis, or blood vascular density (0.05 < P < 0.10). Quantitative real-time PCR and microarray analyses confirmed PEDF down-regulation at the mRNA level in several melanoma lines, compared with melanocytes. MITF positively correlated with PEDF expression in invasive melanomas (P = 0.0003). Searching for PEDF regulatory mechanisms revealed two occupied conserved E-boxes (DNA recognition elements) in the first intron of the human and mouse PEDF promoter regions, confirmed by binding assays. Dominant-negative and siRNA approaches in vivo demonstrated direct transcriptional influence of MITF on PEDF, establishing the PEDF gene (SERPINF1) as a MITF target in melanocytes and melanoma cells. These findings suggest that loss of PEDF expression promotes early invasive melanoma growth.

Videocapillaroscopic alterations in alopecia areata

Alopecia areata (AA) is a common hair disorder observed in dermatological practice; however, the exact mechanisms that lead to the hair loss are still unknown. Disturbances in the blood supply of hair follicles may be one of the elements in the complex pathogenesis of AA. Nailfold videocapillaroscopy is a noninvasive technique that allows analysis of skin microcirculation in vivo. The aim of the study was the videocapillaroscopic assessment of skin microcirculation in AA patients. The study included 44 patients with patchy alopecia areata, 27 with alopecia universalis or totalis, and 40 healthy volunteers. Nailfold videocapillaroscopy was performed in all participants according to a standard protocol. Obtained images were assessed qualitatively and quantitatively. Two types of videocapillaroscopic images were distinguished in the study. Abnormal videocapillaroscopic images were found in 42% of patients. Tortuous and branching capillaries (P = 0.013, P = 0.001), decreased density of capillaries (P = 0.009), enlargement of the efferent limb (P < 0.017), or top part of the loop (P = 0.009) were observed significantly more often than in the control group. Only some patients with AA presented with microvascular abnormalities characterised by altered videocapillaroscopic images. More studies, including larger group of patients with AA, are required to determine the role of observed videocapillaroscopic alterations in AA.

Role of hyaluronan in angiogenesis and its utility to angiogenic tissue engineering

Angiogenesis represents the outgrowth of new blood vessels from existing ones, a physiologic process that is vital to supply nourishment to newly forming tissues during development and tissue remodeling and repair (wound healing). Regulation of angiogenesis in the healthy body occurs through a fine balance of angiogenesis-stimulating factors and angiogenesis inhibitors. When this balance is disturbed, excessive or deficient angiogenesis can result and contribute to development of a wide variety of pathological conditions. The therapeutic stimulation or suppression of angiogenesis could be the key to abrogating these diseases. In recent years, tissue engineering has emerged as a promising technology for regenerating tissues or organs that are diseased beyond repair. Among the critical challenges that deter the practical realization of the vision of regenerating functional tissues for clinical implantation, is how tissues of finite size can be regenerated and maintained viable in the long-term. Since the diffusion of nutrients and essential gases to cells, and removal of metabolic wastes is typically limited to a depth of 150-250 microm from a capillary (3-10 cells thick), tissue constructs must mandatorily permit in-growth of a blood capillary network to nourish and sustain the viability of cells within. The purpose of this article is to provide an overview of the role and significance of hyaluronan (HA), a glycosaminoglycan (GAG) component of connective tissues, in physiologic and pathological angiogenesis, its applicability as a therapeutic to stimulate or suppress angiogenesis in situ within necrotic tissues in vivo, and the factors determining its potential utility as a pro-angiogenic stimulus that will enable tissue engineering of neo-vascularized and functional tissue constructs for clinical use.

Matrix Metalloproteinases and Bladder Cancer: What is New?

Urothelial bladder cancer represents a heterogeneous disease with divergent pathways of tumorigenesis. Tumor invasion and progression are a multifactorial process promoted by microenvironmental changes that include overexpression of matrix metalloproteinases (MMPs). Recent data clearly challenge the classic dogma that MMPs promote metastasis only by modulating the remodeling of extracellular matrix. Indeed, MMPs have also been attributed as an impact on tumor cell behavior in vivo as a consequence of their ability to cleave growth factors, cell surface receptors, cell adhesion molecules, and chemokines/cytokines. Levels of the different MMPs can be measured in several sample types, including tissue, blood (serum and plasma), and urine, and using different methodologies, such as immunohistochemistry, real-time PCR, western and northern blot analyses, enzyme-linked immunosorbent assay, and zymography. Several MMPs have been identified as having potential diagnostic or prognostic utility, whether alone or in combination with cytology. Although MMP inhibitors have shown limited efficacy, advances in the understanding of the complex physiologic and pathologic roles of MMPs might permit the development of new MMP-specific and tumor-specific therapies. In this paper we update the understanding of MMPs based on a systematic PubMed search encompassing papers published up to December 2011.

Therapies using anti-angiogenic peptide mimetics of thrombospondin-1

INTRODUCTION

The role of hrombospondin-1 (TSP1) as a major endogenous angiogenesis inhibitor has been confirmed by numerous studies and subsequent mechanistic discoveries. It has yielded a new class of potential drugs against cancer and other angiogenesis-driven diseases.

AREAS COVERED

An overview of TSP1 functions and molecular mechanisms, including regulation and signaling. Functions in endothelial and non-endothelial cells, with emphasis on the role of TSP1 in the regulation of angiogenesis and inflammation. The utility of duplicating these activities for drug discovery. Past and current literature on endogenous TSP1 and its role in the progression of cancer and non-cancerous pathological conditions is summarized, as well as the research undertaken to identify and optimize short bioactive peptides derived from the two TSP1 anti-angiogenic domains, which bind CD47 and CD36 cell surface receptors. Lastly, there is an overview of the efficacy of some of these peptides in pre-clinical and clinical models of angiogenesis-dependent disease.

EXPERT OPINION

It is concluded that TSP1-derived peptides and peptide mimetics hold great promise as future agents for the treatment of cancer and other diseases driven by excessive angiogenesis. They may fulfill unmet medical needs including neovascular ocular disease and the diseases of the female reproductive tract including ovarian cancer.

Blood vessel density in Basal cell carcinomas and benign trichogenic tumors as a marker for differential diagnosis in dermatopathology

In order to get insight into the density of blood vessels in the stroma of benign and malignant trichogenic neoplasms, immunohistological quantification of CD 31 positive vessels was performed in 112 tumors, comprised of 50 BCCs of nodular (35) or morphoeic (15) growth patterns, 17 Pinkus' tumors, as well as 17 trichoepitheliomas of which 6 were desmoplastic, 8 trichofolliculomas, and 20 trichoblastomas. Methods. Vessel density was counted within the tumors, in the tumor-surrounding stroma, and, as a control, in the normal skin of the operation specimen. The results were compared using statistical methods. Results. Whereas, irrespective of the patients' age and location of tumors, the vessel density in normal skin showed no significant differences (8.8 ± 2.7), the counts in the peritumoral stroma revealed significant differences between the different tumors investigated. The highest counts were obtained in BCC (24.7 ± 6.7) and the lowest in benign trichogenic neoplasms (around 14) Pinkus' tumors revealed intermediate counts (19.7 ± 6.6). The vessel densities within the tumors were generally low, and no correlation to the dignity was found. Conclusion. Determination of blood vessel density in the peritumoral stroma may be an additional parameter for differential diagnosis of trichogenic tumors of uncertain dignity.

Tumor-immune interaction, surgical treatment, and cancer recurrence in a mathematical model of melanoma

Malignant melanoma is a cancer of the skin arising in the melanocytes. We present a mathematical model of melanoma invasion into healthy tissue with an immune response. We use this model as a framework with which to investigate primary tumor invasion and treatment by surgical excision. We observe that the presence of immune cells can destroy tumors, hold them to minimal expansion, or, through the production of angiogenic factors, induce tumorigenic expansion. We also find that the tumor–immune system dynamic is critically important in determining the likelihood and extent of tumor regrowth following resection. We find that small metastatic lesions distal to the primary tumor mass can be held to a minimal size via the immune interaction with the larger primary tumor. Numerical experiments further suggest that metastatic disease is optimally suppressed by immune activation when the primary tumor is moderately, rather than minimally, metastatic. Furthermore, satellite lesions can become aggressively tumorigenic upon removal of the primary tumor and its associated immune tissue. This can lead to recurrence where total cancer mass increases more quickly than in primary tumor invasion, representing a clinically more dangerous disease state. These results are in line with clinical case studies involving resection of a primary melanoma followed by recurrence in local metastases.

Melanoma is a deadly skin cancer that invades into the dermis and metastasizes into the surrounding tissue. In clinical cases, surgical excision of the primary tumor has led to widespread and accelerated growth in metastases. We develop a mathematical model describing the basic process of melanoma invasion, metastatic spread, and the anti-tumor immune response. This model is formulated using partial differential equations that describe the spatial and temporal evolution of a number of different cellular populations, and it uses a realistic skin geometry. Using simulations, we examine the importance of the immune response when a primary tumor is spawning satellite metastases. We find that local metastases can be suppressed by the immune response directed against the primary tumor, but grow aggressively following surgical treatment. We also find that moderately metastatic tumors optimally activate the local immune response against disseminated disease, and in this case tumor excision may have profound effects on metastatic growth. We conclude that surgical perturbation of the immune response controlling local metastases is one mechanism by which cancer can recur. This could have implications as to the appropriate clinical management of melanomas and other solid tumors.

Infrared exposure induces an angiogenic switch in human skin that is partially mediated by heat

BACKGROUND

Angiogenesis plays an important role in physiological and pathological conditions of the skin. Although acute ultraviolet-induced skin angiogenesis has been investigated, little is known about the distinct effects of acute infrared (IR) radiation on angiogenesis in human skin.

OBJECTIVES

To elucidate the molecular regulation of the angiogenic switch by acute near-IR radiation or by a single heat treatment in human skin in vivo.

METHODS

We subjected 16 healthy volunteers to near-IR irradiation (six minimal heating doses) and 14 healthy volunteers to heat treatment (43 degrees C for 90 min), and skin specimens were obtained by punch biopsy for immunohistochemical, Western blot and reverse transcription-polymerase chain reaction analyses.

RESULTS

We observed that CD31-stained vessels in the upper dermis were increased after acute near-IR exposure, and that this was associated with the upregulation of vascular endothelial growth factor (VEGF) and the downregulation of thrombospondin (TSP)-2. During the application of near-IR to buttock skin, skin temperatures immediately increased from 32 degrees C up to 42 degrees C, as measured using a digital thermometer. Moreover, the expression of inducible heat shock protein 70 was increased after near-IR irradiation in human skin. Therefore, we investigated the effects of a single heat treatment on angiogenesis and on the expression of VEGF and TSP-2 in skin, and found that vascularization and VEGF expression were increased, whereas TSP-2 expression was reduced.

CONCLUSIONS

Our results suggest that IR radiation plays an important role in skin angiogenesis via regulation of the balance between the angiogenic inducer VEGF and the angiogenic inhibitor TSP-2, and that IR-induced skin angiogenesis might be partially caused by the effects of heat in human skin in vivo.

All-trans retinoic acid antagonizes UV-induced VEGF production and angiogenesis via the inhibition of ERK activation in human skin keratinocytes

Incident UV radiation leads to the upregulation of vascular endothelial growth factor (VEGF), a potent angiogenic factor, in human skin. However, the molecular basis of UV-induced angiogenesis in skin remains to be elucidated. In this study, we investigated the roles of UV exposure on cutaneous angiogenesis, its associated signaling mechanisms, and the effect of all-trans retinoic acid (tRA) on UV-induced vascularization, and VEGF expression. Using a human epidermal cell line, HaCaT, we found that UV induces VEGF mRNA and protein expression via the MAPK/ERK kinase-ERK1/2 (extracellular signal-regulated kinase 1/2) pathway but not via the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, and that tRA pretreatment significantly inhibits UV-induced VEGF overexpression and ERK1/2 activation. In human skin in vivo, we confirmed that skin vascularization significantly increased after a single exposure to UV, as was evidenced by a prominent increase in vessel size, vascular density, and in the cutaneous area occupied by vessels, and we found that these events are associated with VEGF upregulation. Topical pretreatment with tRA under occlusion inhibited not only UV-induced VEGF upregulation and angiogenesis with a significant reduction of vessel density but also UV-induced ERK1/2 activation in human skin. Collectively, our data demonstrate that tRA inhibits the UV-induced angiogenic switch via downmodulation of ERK1/2 activation and consecutive VEGF overexpression. These findings may help us understand the molecular mechanisms that regulate skin angiogenesis due to UV exposure, and provide evidence of the potential of tRA in terms of preventing angiogenesis-associated skin damage following exposure to UV irradiation.

Ultraviolet Radiation Attenuates Thrombospondin 1 Expression via PI3K-Akt Activation in Human Keratinocytes

Thrombospondin 1 (TSP1) is an extracellular glycoprotein and a recognized inhibitor of angiogenesis. Recent studies have demonstrated that UV radiation induces an angiogenic switch, by which it alters the balance between pro- and anti-angiogenic factors in the skin. Here we describe the effects of acute UV exposure on TSP1 expression in human skin epidermis, primary keratinocytes and the epidermal cell line HaCaT. We found that protein and mRNA expressions of TSP1 are significantly reduced in human skin in vivo and in keratinocytes in vitro by a single UV exposure. In human skin and keratinocytes, UV exposure induced the phosphorylation of Akt, a downstream target of the PI3K pathways. Specific inhibitors of PI3K, wortmannin and LY294002, completely blocked Akt activation and UV-induced TSP1 downregulation in keratinocytes. We showed that a specific Akt phosphorylation inhibitor and small interfering RNA-mediated Akt depletion were also blocked by UV-induced TSP1 downregulation in keratinocytes. In conclusion, our findings demonstrate that acute UV exposure downregulates TSP1 expression via PI3K-Akt activation in human keratinocytes. These novel findings may help us understand the regulatory mechanisms of UV-induced skin angiogenesis.

The placenta growth factor in skin angiogenesis

The placenta growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that has been shown to play an important role in promoting adult pathological angiogenesis. Besides inducing its own signaling in endothelial cells, PlGF exerts its angiogenic action by synergising with VEGF. In the skin, PlGF expression is upregulated during wound healing and PlGF-deficient mice show delayed wound closure, indicating that this factor promotes angiogenesis during skin repair. Moreover, PlGF expression by melanoma cells has been linked to tumor growth. The analysis of a transgenic mouse model constitutively expressing high levels of PlGF in basal keratinocytes has shown that this factor has strong angiogenic properties in the skin during both embryonic and post-natal life. Furthermore, PlGF delivery to the skin via an adenoviral vector induces the formation of large and stable blood vessels, but contrary to VEGF application, does not affect lymphatic vessel functionality. Such evidence opens the possibility of employing PlGF for therapeutic modulation of skin angiogenesis.

Pododermal angiogenesis and angioadaptation in the bovine claw

Pododermal microvascularization has been suggested to play a key role in the physiological function of the bovine claw and in the pathogenesis of claw diseases. According to our working hypothesis, angiogenesis plays a central role in the physiological and pathological function of the claw and is induced by the pro-angiogenic vascular endothelial growth factor (VEGF). As a basis for further research, the aim of the present study was to examine the mechanisms of pododermal angiogenesis in the functional adaptation of the microvasculature of the claw in histological serial sections and microcorrosion casts of healthy juvenile and adult claws as well as pathologically altered claws. Scanning electron microscopy of microcorrosion casts allowed assessment of the 3D aspect of pododermal angiogenesis and angioadaptation, and was substantiated by a concomitant examination of a 3D in vitro model of angiogenesis based on cultured bovine microvascular endothelial cells. Particularly in the juvenile, but also in the adult claw, sprouting and intussusceptive angioadaptation was demonstrated and resembled the respective stages of in vitro angiogenesis. Evidence of angiogenic processes was also detected in the pathologically altered claws displaying symptoms of subclinical laminitis and/or the digital dermatitis complex. The detected angioadaptation was visible expression of the increased metabolic demands of the claw caused by the growing body weight load. Angiogenic remodeling of the pododermal angioarchitecture was also the connectional reparative principle in pathologically altered claws. Related research perspectives for prophylaxis and therapy of claw diseases are discussed.

Mast cells and vasculature in atopic dermatitis--potential stimulus of neoangiogenesis

BACKGROUND

Atopic dermatitis skin lesions are characterized by inflammatory changes and epithelial hyperplasia requiring angiogenesis. As mast cells may participate in this process via bidirectional secretion of tissue-damaging enzymes and pro-angiogenic factors, the present study aimed to assess the occurrence and possible function of mast cells in the papillary dermis and in epidermal layers of atopic dermatitis lesions.

METHODS

Semi-thin and serial sections in combination with immunohistochemistry, histochemistry and proliferating cell nuclear antigen (PCNA)-activity assays were used and related to epidermal thickness and targeted gene expression studies.

RESULTS

Mast cells were located in the papillary dermis and migrated through the basal lamina into the epidermis of atopic dermatitis lesions. An increased PCNA-activity in cells of superficial epidermal layers indicated an activation of keratinocytes and stimulation of endothelial growth. Only approximately 30% of the papillary mast cells stained with the tryptase were toluidin-blue-positive, and approximately 80% were chymase positive. A high number of mast cells expressed c-kit. Most papillary and epidermal mast cells were localized close to endothelial cells. Vascular expression of endoglin (CD105) demonstrated neoangiogenic processes. Mast cells stimulation led to the expression of proangiogenic factors. Also, gene expression of tissue-damaging factors such as matrix metalloproteinases was increased.

CONCLUSIONS

These data suggest that in atopic dermatitis, mast cells are abundantly localized close to and within the epidermis where they may stimulate neoangiogenesis. Via the new vessels, inflammatory cells, together with complement components and antibodies, can be transported to the epidermis to aid in the defense against environmental antigens and to maintain chronic inflammation.

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.

Photochemotherapy inhibits angiogenesis and induces apoptosis of endothelial cells in vitro

BACKGROUND

Photochemotherapy has long been used in the treatment of psoriasis; however, its mechanism has not been completely elucidated. Psoriasis is now regarded as an angiogenesis-related disease. Recent studies indicated that the inhibition of angiogenesis by photochemotherapy could be an underlying mechanism. It was found that photochemotherapy can downregulate the expression of angiogenic factors in keratinocytes. However, the direct effect of photochemotherapy on endothelial cells has not been studied.

METHODS

In this study, we determined the effect of photochemotherapy on the proliferation of human microvascular endothelial cells through MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and cell cycle analysis. The migration assay and in vitro tube formation assay were used to investigate the migration properties and tube formation ability of human microvascular endothelial cells after psoralen plus UVA (PUVA) treatment. The apoptosis of endothelial cells elicited by photochemotherapy was also analyzed with fluorescence-activated cell sorting analysis (FACS).

RESULTS

UVA (0.8-5.0 J/cm(2)) irradiation with the presence of 8-methoxypsoralen (8-MOP) (300 ng/ml) resulted in a dose-dependent reduction in the cell viabilities of endothelial cells. FACS data showed an accumulation of cells in G0/G1 phase of cell cycle and apoptotic features of cell death after UVA irradiation with psoralen. The migration properties and tube formation ability of endothelial cells were dramatically inhibited by photochemotherapy.

CONCLUSION

Our results showed that photochemotherapy inhibits angiogenesis and induces apoptosis of human microvascular endothelial cells in vitro, which may be a possible mechanism of photochemotherapy in the treatment of psoriasis.

Downregulation of BRCA1 in A375 melanoma cell line increases radio-sensitivity and modifies metastatic and angiogenic gene expression

The participation of BRCA1 (breast cancer 1) in DNA repair is well established, especially in mammary and ovarian cells. Our purpose was to develop a new in vivo radio-sensitizing therapy for melanoma. We therefore investigated the effect of downregulation of BRCA1 on irradiated melanoma cells using an anti-BRCA1 ribozyme. Our results show that BRCA1 downregulation increased radio-sensitivity of the A375 cell line, suggesting that BRCA1 could act as a caretaker in melanoma; however, as BRCA1 functions are not limited to maintaining genomic integrity but also regulate transcription and the cell cycle, we confirmed that the proliferative rate of BRCA1 downregulated clones did not change. We also demonstrate that: (1) among the major pro-angiogenic genes, FGF-2 was not increased before or after irradiation and vascular endothelial growth factor strongly inhibited after irradiation; (2) expression of two important metalloproteinases, matrix metalloproteinase 2 and 9, involved in melanoma metastasis were decreased before and after irradiation; (3) expression of their major inhibitor, tissue inhibitor of metalloproteinase, was mainly upregulated; and (4) that invasion of BRCA1 downregulated cells was modified. Together these data suggest that BRCA1 downregulation in melanoma cells did not make them more aggressive and could lead to new therapeutic strategies for this tumor, which is so difficult to control once metastasized.

In vivo and in situ modulation of the expression of genes involved in metastasis and angiogenesis in a patient treated with topical imiquimod for melanoma skin metastases

There is a growing body of evidence to support the efficacy of topical imiquimod in the treatment of primary skin carcinomas. Conflicting data exist concerning the use of imiquimod for the treatment of skin melanoma metastases. To date, only the impact of imiquimod on cytokines involved in immunological processes has been studied extensively. We report a woman successfully treated with imiquimod (once daily for 8 weeks) for skin melanoma metastases in whom we investigated the expression of molecules involved in metastasis and angiogenesis. Before and after treatment, a skin lesion was biopsied and the expression of the following molecules was investigated using real-time reverse transcription-polymerase chain reaction: matrix metalloproteinase (MMP)-1, 2 and 9 and their inhibitors KiSS-1 and tissue inhibitor of metalloproteinase (TIMP)-1, vascular endothelial growth factor (VEGF), fibroblast growth factor-2, and angiogenesis inhibitors (thrombospondin-1 and 2). Interferon (IFN)-alpha was also investigated as an in vivo marker of imiquimod activity. IFN-alpha was upregulated by the treatment. Under imiquimod, the following molecules were upregulated: TIMP-1, KiSS-1 and MMP-1. MMP-2 expression was not modified. MMP-9 expression was dramatically decreased. The expression of angiogenesis inhibitors was slightly increased but VEGF expression remained at a basal level. These results suggest that imiquimod could downregulate metastasis invasion and angiogenesis. However, these data were obtained at a transcriptional level and from a single case, and further investigations should include migration assays and additional cases in order to confirm that imiquimod may be safely used for treatment of melanoma metastases.