The keratinocyte in epidermal renewal and defence

Traditionally, keratinocytes have been considered inert constituents of the multilayered epidermis. Today's understanding has fundamentally changed. The keratinocyte is now recognized as an active player in epidermal renewal with key functions in the skin's immune defence. Under homeostatic conditions, keratinocyte progenitor cells are believed to divide symmetrically or asymmetrically, that is they continue to proliferate or go on to terminally differentiate and build up the overlaying epidermis. The fine-tuned process of epidermal renewal relies on an extraordinary network of signalling cascades which are governed by keratinocyte-receptor interactions with the environment through paracrine and autocrine circuits. Opposing this coordinated homeostatic process are signals of wounding and inflammation. They alter the fate of the keratinocyte and its response to the environment through changes in adhesion molecules and surface receptors, in addition to triggering an immediate inflammatory keratinocyte response in terms of secretion of cytokines, chemokines and antimicrobial peptides. If uncontrolled, the fundamental changes imposed by wounding and inflammation upon the homeostatic programme can lead to severe skin lesions including chronic inflammatory disorders. This review will describe the current knowledge of the regulatory signalling network which allows the keratinocyte to actively impact both epidermal homeostasis and the inflammatory response.

Inhibition of Notch signaling induces extensive intussusceptive neo-angiogenesis by recruitment of mononuclear cells

Notch is an intercellular signaling pathway related mainly to sprouting neo-angiogenesis. The objective of our study was to evaluate the angiogenic mechanisms involved in the vascular augmentation (sprouting/intussusception) after Notch inhibition within perfused vascular beds using the chick area vasculosa and MxCreNotch1(lox/lox) mice. In vivo monitoring combined with morphological investigations demonstrated that inhibition of Notch signaling within perfused vascular beds remarkably induced intussusceptive angiogenesis (IA) with resultant dense immature capillary plexuses. The latter were characterized by 40 % increase in vascular density, pericyte detachment, enhanced vessel permeability, as well as recruitment and extravasation of mononuclear cells into the incipient transluminal pillars (quintessence of IA). Combination of Notch inhibition with injection of bone marrow-derived mononuclear cells dramatically enhanced IA with 80 % increase in vascular density and pillar number augmentation by 420 %. Additionally, there was down-regulation of ephrinB2 mRNA levels consequent to Notch inhibition. Inhibition of ephrinB2 or EphB4 signaling induced some pericyte detachment and resulted in up-regulation of VEGFRs but with neither an angiogenic response nor recruitment of mononuclear cells. Notably, Tie-2 receptor was down-regulated, and the chemotactic factors SDF-1/CXCR4 were up-regulated only due to the Notch inhibition. Disruption of Notch signaling at the fronts of developing vessels generally results in massive sprouting. On the contrary, in the already existing vascular beds, down-regulation of Notch signaling triggered rapid augmentation of the vasculature predominantly by IA. Notch inhibition disturbed vessel stability and led to pericyte detachment followed by extravasation of mononuclear cells. The mononuclear cells contributed to formation of transluminal pillars with sustained IA resulting in a dense vascular plexus without concomitant vascular remodeling and maturation.

Everolimus dual effects of an area vasculosa angiogenesis and lymphangiogenesis

Recently approved as treatment for astrocytoma, kidney and pancreatic cancer, everolimus acts on tumor cells by inhibiting tumor cell growth and proliferation, as well as by inhibition of angiogenic activity by both direct effects on vascular cell proliferation and indirect effects on growth factor production. The effects of everolimus on early stages of normal vasculogenesis, angiogenesis and lymphangiogenesis are not yet available. We found increased development of intravascular pillars by using area vasculosa of the chick chorioallantoic membrane treated with everolimus. An active lymphangiogenic response was highlighted by the expression of Prospero homeobox protein 1 (Prox1) and podoplanin, together with vascular endothelial growth factor receptor C (Vegf-C) and vascular endothelial growth factor receptor 3 (Vegfr-3) expression on day 4 in the treated group. These findings suggest a potential role of everolimus in the activation of lymphangiogenesis.

Cell-demanded liberation of VEGF121 from fibrin implants induces local and controlled blood vessel growth

Although vascular endothelial growth factor (VEGF) has been described as a potent angiogenic stimulus, its application in therapy remains difficult: blood vessels formed by exposure to VEGF tend to be malformed and leaky. In nature, the principal form of VEGF possesses a binding site for ECM components that maintain it in the immobilized state until released by local cellular enzymatic activity. In this study, we present an engineered variant form of VEGF, alpha2PI1-8-VEGF121, that mimics this concept of matrix-binding and cell-mediated release by local cell-associated enzymatic activity, working in the surgically-relevant biological matrix fibrin. We show that matrix-conjugated alpha2PI1-8-VEGF121 is protected from clearance, contrary to native VEGF121 mixed into fibrin, which was completely released as a passive diffusive burst. Grafting studies on the embryonic chicken chorioallantoic membrane (CAM) and in adult mice were performed to assess and compare the quantity and quality of neovasculature induced in response to fibrin implants formulated with matrix-bound alpha2PI1-8-VEGF121 or native diffusible VEGF121. Our CAM measurements demonstrated that cell-demanded release of alpha2PI1-8-VEGF121 increases the formation of new arterial and venous branches, whereas exposure to passively released wild-type VEGF121 primarily induced chaotic changes within the capillary plexus. Specifically, our analyses at several levels, from endothelial cell morphology and endothelial interactions with periendothelial cells, to vessel branching and network organization, revealed that alpha2PI1-8-VEGF121 induces vessel formation more potently than native VEGF121 and that those vessels possess more normal morphologies at the light microscopic and ultrastructural level. Permeability studies in mice validated that vessels induced by alpha2PI1-8-VEGF121 do not leak. In conclusion, cell-demanded release of engineered VEGF121 from fibrin implants may present a therapeutically safe and practical modality to induce local angiogenesis.

3D scaffolds co-seeded with human endothelial progenitor and mesenchymal stem cells: evidence of prevascularisation within 7 days

Blood supply is a critical issue in most tissue engineering approaches for large defect healing. As vessel ingrowth from surrounding tissues is proven to be insufficient, current strategies are focusing on the neo-vascularisation process. In the present study, we developed an in vitro pre-vascularised construct using 3D polyurethane (PU) scaffolds, based on the association of human Endothelial Progenitor Cells (EPC, CD34+ and CD133+) with human Mesenchymal Stem Cells (MSC). We showed the formation of luminal tubular structures in the co-seeded scaffolds as early as day 7 in culture. These tubular structures were proven positive for endothelial markers von Willebrand Factor and PECAM-1. Of special significance in our constructs is the presence of CD146-positive cells, as a part of the neovasculature scaffolding. These cells, coming from the mesenchymal stem cells population (MSC or EPC-depleted MSC), also expressed other markers of pericyte cells (NG2 and αSMA) that are known to play a pivotal function in the stabilisation of newly formed pre-vascular networks. In parallel, in co-cultures, osteogenic differentiation of MSCs occurred earlier when compared to MSCs monocultures, suggesting the close cooperation between the two cell populations. The presence of angiogenic factors (from autologous platelet lysates) in association with osteogenic factors seems to be crucial for both cell populations' cooperation. These results are promising for future clinical applications, as all components (cells, growth factors) can be prepared in an autologous way.

Development of a bead-based multiplex assay for the simultaneous detection of porcine inflammation markers using xMAP technology

Commercially available assays for the simultaneous detection of multiple inflammatory and cardiac markers in porcine blood samples are currently lacking. Therefore, this study was aimed at developing a bead-based, multiplexed flow cytometric assay to simultaneously detect porcine cytokines [interleukin (IL)-1β, IL-6, IL-10, and tumor necrosis factor alpha], chemokines (IL-8 and monocyte chemotactic protein 1), growth factors [basic fibroblast growth factor (bFGF), vascular endothelial growth factor, and platelet-derived growth factor-bb], and injury markers (cardiac troponin-I) as well as complement activation markers (C5a and sC5b-9). The method was based on the Luminex xMAP technology, resulting in the assembly of a 6- and 11-plex from the respective individual singleplex situation. The assay was evaluated for dynamic range, sensitivity, cross-reactivity, intra-assay and interassay variance, spike recovery, and correlation between multiplex and commercially available enzyme-linked immunosorbent assay as well as the respective singleplex. The limit of detection ranged from 2.5 to 30,000 pg/ml for all analytes (6- and 11-plex assays), except for soluble C5b-9 with a detection range of 2-10,000 ng/ml (11-plex). Typically, very low cross-reactivity (<3% and <1.4% by 11- and 6-plex, respectively) between analytes was found. Intra-assay variances ranged from 4.9 to 7.4% (6-plex) and 5.3 to 12.9% (11-plex). Interassay variances for cytokines were between 8.1 and 28.8% (6-plex) and 10.1 and 26.4% (11-plex). Correlation coefficients with singleplex assays for 6-plex as well as for 11-plex were high, ranging from 0.988 to 0.997 and 0.913 to 0.999, respectively. In this study, a bead-based porcine 11-plex and 6-plex assay with a good assay sensitivity, broad dynamic range, and low intra-assay variance and cross-reactivity was established. These assays therefore represent a new, useful tool for the analysis of samples generated from experiments with pigs.

THE EXPRESSION AND CELLULAR LOCALIZATION OF CC-CHEMOKINE RECEPTOR 5 (CCR5) AFTER TRAUMATIC BRAIN INJURY

Traumatic brain injury results from a primary insult and secondary events that together result in tissue injury. This primary injury occurs at the moment of impact and damage can include scalp laceration, skull fraction, cerebral contusions and lacerations as well as intracranial hemorrhage. Following the initial insult, a delayed response occurs and is characterized by hypoxia, ischemia, cerebral edema, and infection. During secondary brain injury, a series of neuroinflammatory events are triggered that can produce additional damage but may also help to protect nervous tissue from invading pathogens and help to repair the damaged tissue. Brain microglia and astrocytes become activated and migrate to the site of injury where these cells secrete immune mediators such as cytokines and chemokines. CC-chemokine receptor 5 (CCR5) is a member of the CC chemokine receptor family of seven transmembrane G protein coupled receptors. CCR5 is expressed in the immune system and is found in monocytes, leukoctyes, memory T cells, and immature dendritic cells. Upon binding to its ligands, CCR5 functions in the chemotaxis of these immune cells to the site of inflammation. In the CNS, CCR5 and its ligands are expressed in multiple cell types. In this study, I investigated whether CCR5 expression is altered in brain after traumatic brain injury. I examined the time course of CCR5 protein expression in cortex and hippocampus using quantitative western analysis of tissues from injured rat brain after mild impact injury. In addition, I also investigated the cellular localization of CCR5 before and after brain injury using confocal microscopy. I have observed that after brain injury CCR5 is upregulated in a time dependent manner in neurons of the parietal cortex and hippocampus. The absence of CCR5 expression in microglia and its delayed expression in neurons after injury suggests a role for CCR5 in neuronal survival after injury.

Reduced neutrophil count in people of African descent is due to a regulatory variant in the Duffy antigen receptor for chemokines gene.

Persistently low white blood cell count (WBC) and neutrophil count is a well-described phenomenon in persons of African ancestry, whose etiology remains unknown. We recently used admixture mapping to identify an approximately 1-megabase region on chromosome 1, where ancestry status (African or European) almost entirely accounted for the difference in WBC between African Americans and European Americans. To identify the specific genetic change responsible for this association, we analyzed genotype and phenotype data from 6,005 African Americans from the Jackson Heart Study (JHS), the Health, Aging and Body Composition (Health ABC) Study, and the Atherosclerosis Risk in Communities (ARIC) Study. We demonstrate that the causal variant must be at least 91% different in frequency between West Africans and European Americans. An excellent candidate is the Duffy Null polymorphism (SNP rs2814778 at chromosome 1q23.2), which is the only polymorphism in the region known to be so differentiated in frequency and is already known to protect against Plasmodium vivax malaria. We confirm that rs2814778 is predictive of WBC and neutrophil count in African Americans above beyond the previously described admixture association (P = 3.8 x 10(-5)), establishing a novel phenotype for this genetic variant.

THE EXPRESSION AND CELLULAR LOCALIZATION OF CC-CHEMOKINE RECEPTOR 5 (CCR5) AFTER TRAUMATIC BRAIN INJURY

Traumatic brain injury results from a primary insult and secondary events that together result in tissue injury. This primary injury occurs at the moment of impact and damage can include scalp laceration, skull fraction, cerebral contusions and lacerations as well as intracranial hemorrhage. Following the initial insult, a delayed response occurs and is characterized by hypoxia, ischemia, cerebral edema, and infection. During secondary brain injury, a series of neuroinflammatory events are triggered that can produce additional damage but may also help to protect nervous tissue from invading pathogens and help to repair the damaged tissue. Brain microglia and astrocytes become activated and migrate to the site of injury where these cells secrete immune mediators such as cytokines and chemokines. CC-chemokine receptor 5 (CCR5) is a member of the CC chemokine receptor family of seven transmembrane G protein coupled receptors. CCR5 is expressed in the immune system and is found in monocytes, leukoctyes, memory T cells, and immature dendritic cells. Upon binding to its ligands, CCR5 functions in the chemotaxis of these immune cells to the site of inflammation. In the CNS, CCR5 and its ligands are expressed in multiple cell types. In this study, I investigated whether CCR5 expression is altered in brain after traumatic brain injury. I examined the time course of CCR5 protein expression in cortex and hippocampus using quantitative western analysis of tissues from injured rat brain after mild impact injury. In addition, I also investigated the cellular localization of CCR5 before and after brain injury using confocal microscopy. I have observed that after brain injury CCR5 is upregulated in a time dependent manner in neurons of the parietal cortex and hippocampus. The absence of CCR5 expression in microglia and its delayed expression in neurons after injury suggests a role for CCR5 in neuronal survival after injury.

Effects of Combined Bevacizumab and Paclitaxel on Tumor Interstitial Fluid Pressure in a Preclinical Breast Cancer Model

Effects of Combined Bevacizumab and Paclitaxel on Tumor Interstitial Fluid Pressure in a Preclinical Breast Cancer Model by Ricardo H. Alvarez Several mechanisms of cell resistance are often accountable for unsuccessful chemotherapy against cancer. Another reason, which has received increased attention, is the inefficient transport of anticancer drugs into tumor tissue. These impaired transports of chemotherapy into the tumor have been attributed to abnormal microvasculature and to pathologically increased tumor hypertension also called: interstitial fluid pressure (IFP). The pathophysiological processes leading to elevated tumor IFP are poorly understood. Here, in a preclinical breast cancer model, it is argued that a condition of raised IFP is a major factor in preventing optimal access of systemically administered chemotherapy agents. In our experimental model, we used a GILM2 human breast cancer in xenografts; mice were treated with different doses of paclitaxel –a widely used antimicrotubular agent, and bevacizumab –monoclonal antibody against vascular endothelial growth factor (VEGF). The proposed research project is designed to test the hypothesis that paclitaxel in combination with bevacizumab decreases the tumor IPF by restoring tumor permeability and increasing chemotherapy delivery. We demonstrated that the combination of paclitaxel and bevacizumab produced greater tumor control than either agent given alone and this combination reduced the IFP, producing an increment of 75% of apoptosis compared with the control arm. In addition, the intra-tumor paclitaxel quantification by liquid chromatography/Mass Spectrometry (LC/MS) demonstrated that lower dose of both agents showed a synergistic effect compared with high dose of treatment, where there is no significantly increase of paclitaxel into the tumor. These preclinical results are likely to have broad implications for the utility of anti-angiogenic therapies alone and in combination with chemotherapeutic agents.

FoxM1B transcriptionally regulates vascular endothelial growth factor expression and promotes the angiogenesis and growth of glioma cells.

We previously found that FoxM1B is overexpressed in human glioblastomas and that forced FoxM1B expression in anaplastic astrocytoma cells leads to the formation of highly angiogenic glioblastoma in nude mice. However, the molecular mechanisms by which FoxM1B enhances glioma angiogenesis are currently unknown. In this study, we found that vascular endothelial growth factor (VEGF) is a direct transcriptional target of FoxM1B. FoxM1B overexpression increased VEGF expression, whereas blockade of FoxM1 expression suppressed VEGF expression in glioma cells. Transfection of FoxM1 into glioma cells directly activated the VEGF promoter, and inhibition of FoxM1 expression by FoxM1 siRNA suppressed VEGF promoter activation. We identified two FoxM1-binding sites in the VEGF promoter that specifically bound to the FoxM1 protein. Mutation of these FoxM1-binding sites significantly attenuated VEGF promoter activity. Furthermore, FoxM1 overexpression increased and inhibition of FoxM1 expression suppressed the angiogenic ability of glioma cells. Finally, an immunohistochemical analysis of 59 human glioblastoma specimens also showed a significant correlation between FoxM1 overexpression and elevated VEGF expression. Our findings provide both clinical and mechanistic evidence that FoxM1 contributes to glioma progression by enhancing VEGF gene transcription and thus tumor angiogenesis.

Janus kinases 1 and 2 regulate chemokine-mediated integrin activation and naïve T-cell homing.

Janus kinases (JAKs) are central signaling molecules in cytokine receptor cascades. Although they have also been implicated in chemokine receptor signaling, this function continues to be debated. To address this issue, we established a nucleofection model in primary, nonactivated mouse T lymphocytes to silence JAK expression and to evaluate the ability of these cells to home to lymph nodes. Reduced JAK1 and JAK2 expression impaired naïve T-cell migration in response to gradients of the chemokines CXCL12 and CCL21. In vivo homing of JAK1/JAK2-deficient cells to lymph nodes decreased, whereas intranodal localization and motility were unaffected. JAK1 and JAK2 defects altered CXCL12- and CCL21-triggered ezrin/radixin/moesin (ERM) dephosphorylation and F-actin polymerization, as well as activation of lymphocyte function-associated Ag-1 and very late Ag-4 integrins. As a result, the cells did not adhere firmly to integrin substrates in response to these chemokines. The results demonstrate that JAK1/JAK2 participate in chemokine-induced integrin activation and might be considered a target for modulation of immune cell extravasation and therefore, control of inflammatory reactions.

Role of A2B adenosine receptor signaling in adenosine-dependent pulmonary inflammation and injury.

Adenosine has been implicated in the pathogenesis of chronic lung diseases such as asthma and chronic obstructive pulmonary disease. In vitro studies suggest that activation of the A2B adenosine receptor (A2BAR) results in proinflammatory and profibrotic effects relevant to the progression of lung diseases; however, in vivo data supporting these observations are lacking. Adenosine deaminase-deficient (ADA-deficient) mice develop pulmonary inflammation and injury that are dependent on increased lung adenosine levels. To investigate the role of the A2BAR in vivo, ADA-deficient mice were treated with the selective A2BAR antagonist CVT-6883, and pulmonary inflammation, fibrosis, and airspace integrity were assessed. Untreated and vehicle-treated ADA-deficient mice developed pulmonary inflammation, fibrosis, and enlargement of alveolar airspaces; conversely, CVT-6883-treated ADA-deficient mice showed less pulmonary inflammation, fibrosis, and alveolar airspace enlargement. A2BAR antagonism significantly reduced elevations in proinflammatory cytokines and chemokines as well as mediators of fibrosis and airway destruction. In addition, treatment with CVT-6883 attenuated pulmonary inflammation and fibrosis in wild-type mice subjected to bleomycin-induced lung injury. These findings suggest that A2BAR signaling influences pathways critical for pulmonary inflammation and injury in vivo. Thus in chronic lung diseases associated with increased adenosine, antagonism of A2BAR-mediated responses may prove to be a beneficial therapy.

Expression of the neural stem cell markers NG2 and L1 in human angiomyolipoma: are angiomyolipomas neoplasms of stem cells?

Angiomyolipomas are benign tumors of the kidney which express phenotypes of smooth muscle, fat, and melanocytes. These tumors appear with increased frequency in the autosomal dominant disorder tuberous sclerosis and are the leading cause of morbidity in adults with tuberous sclerosis. While benign, these tumors are capable of provoking life threatening hemorrhage and replacement of the kidney parenchyma, resulting in renal failure. The histogenesis of these tumors is currently unclear, although currently, we believe these tumors arise from "perivascular epithelioid cells" of which no normal counterpart has been convincingly demonstrated. Recently, stem cell precursors have been recognized that can give rise to smooth muscle and melanocytes. These precursors have been shown to express the neural stem cell marker NG2 and L1. In order to determine whether angiomyolipomas, which exhibit smooth muscle and melanocytic phenotypes, express NG2 and L1, we performed immunocytochemistry on a cell line derived from a human angiomyolipoma, and found that these cells are uniformly positive. Immunohistochemistry of human angiomyolipoma specimens revealed uniform staining of tumor cells, while renal cell carcinomas revealed positivity only of angiogenic vessels. These results support a novel histogenesis of angiomyolipoma as a defect in differentiation of stem cell precursors.

APPLICATIONS OF EPHB4 RECEPTOR SPECIFIC PEPTIDES IN TARGETED CANCER IMAGING AND THERAPY

EphB4 receptors, a member of the largest family of receptor tyrosine kinases, are found over-expressed in a variety of tumors cells including glioma cells as well as angiogenic blood vessels. Noninvasive imaging of EphB4 could potentially increase early detection rates, monitor response to therapy directed against EphB4, and improve patient outcomes. Targeted delivery of EphB4 receptor specific peptide conjugated hollow gold nanoshells (HAuNS) into tumors has great potential in cancer imaging and photothermal therapy. In this study, we developed an EphB4 specific peptide named TNYL-RAW and labeled with radioisotope 64Cu and Cy5.5 dye. We also conjugate this specific peptide with hollow gold nanoshells (HAuNS) to evaluate targeted photothermal therapy of cancers. In vitro, 64Cu-DOTA-TNYL- RAW specifically bind to CT26 and PC-3M cells but not to A549 cells. In vivo, Small-animal PET/CT clearly showed the significant uptake of 64Cu-DOTA-TNYL-RAW in CT26 and PC-3M tumors but not in A549 tumors. Furthermore, µPET/CT and near-infrared optical imaging clearly showed the uptake of the dual labeled TNYL-RAW peptide in both U251 and U87 tumors in the brains of nude mice. In U251 tumors, Cy5.5-labeled peptide can bind to EphB4-expressing tumor blood vessels and tumors cells. But in U87 models, dual labeled peptide only could bind to tumor associated blood vessels. Also, Irradiation of PC-3M and CT-26 cell treated with TNYL-PEG-HAuNS nanopatilces with near-infrared (NIR) laser resulted in selective destruction of these cells in vitro. EphB4 targeted TNYL-PEG-HAuNS showed more photothermal killing effect on CT26 tumor model than PEG-HAuNS did. In summary, tumors with overexpression of EphB4 receptors can be noninvasively visualized by micro PET/CT with 64Cu labeled or dual labeled TNYL-RAW peptide. Targeted delivery of TNYL-RAW conjugated HAuNS into tumors can greatly improve the treatment effect of photothermal therapy. The information acquired with this study should be advantageous in improving diagnostics and future applications in photothermal ablation therapy in clinical.