ECM590 Sigma-AldrichBlood Vessel Staining Kit

Mesenchymal stem cells (MSCs) seeded in composite implants formed of hydroxyapatite (HA) and poly (lactide-co-glycolide) (PLG) exhibit increased osteogenesis and enhanced angiogenic potential. Endothelial colony-forming cells (ECFCs) can participate in de novo vessel formation when implanted in vivo. The aim of this study was to determine the capacity of HA-PLG composites to cotransplant MSCs and ECFCs, with the goal of accelerating vascularization and resultant bone formation. The incorporation of HA into PLG scaffolds improved the efficiency of cell seeding and ECFC survival in vitro. We observed increases in mRNA expression and secretion of potent angiogenic factors by MSCs when cultured on HA-PLG scaffolds compared to PLG controls. Upon implantation into an orthotopic calvarial defect, ECFC survival on composite scaffolds was not increased in the presence of MSCs, nor did the addition of ECFCs enhance vascularization beyond increases observed with MSCs alone. Microcomputed tomography (micro-CT) performed on explanted calvarial tissues after 12 weeks revealed no significant differences between treatment groups for bone volume fraction (BVF) or bone mineral density (BMD). Taken together, these results provide evidence that HA-containing composite scaffolds seeded with MSCs can enhance neovascularization, yet MSC-secreted trophic factors do not consistently increase the persistence of co-transplanted ECFCs.

The neurotransmitter dopamine and its dopamine receptor D2 (D2DR) agonists are known to inhibit vascular permeability factor/vascular endothelial growth factor (VPF/VEGF)-mediated angiogenesis and vascular permeability. Lung injury is a clinical syndrome associated with signs of increased microvascular permeability. However, the effects of dopamine on pulmonary edema, a phenomenon critical to the pathophysiology of both acute and chronic lung injuries, have yet to be established. Therefore, we sought to determine the potential therapeutic effects of dopamine in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compared with sham-treated controls, pre-treatment with dopamine (50 mg/kg body weight) ameliorated LPS-mediated edema formation and lowered myeloperoxidase activity, a measure of neutrophil infiltration. Moreover, dopamine significantly increased survival rates of LPS-treated mice, from 0% to 75%. Mechanistically, we found that dopamine acts through the VEGF-VEGFR2 axis to reduce pulmonary edema, as dopamine pre-treatment in LPS-treated mice resulted in decreased serum VEGF, VEGFR2 phosphorylation, as well endothelial nitric oxide synthase (eNOS) phosphorylation. To confirm that dopamine blocks vascular permeability in our lung injury model by acting through D2DR, we used D2DR knockout mice for further analysis. As expected, D2DR agonist failed to reduce pulmonary edema in D2DR(-/-) mice. Taken together, our results suggest that dopamine acts through D2DR to inhibit pulmonary edema-associated vascular permeability mediated through VEGF-VEGFR2 signaling and conveys protective effects in an ALI model.

Brain-derived neurotrophic factor (BDNF) has emerged as a novel angiogenic factor, and yet its impact on tumorigenesis is unclear. This study aimed at investigating the roles of BDNF in angiogenesis and tumor development.

Brain angiogenesis inhibitor 1 (BAI1) is a transmembrane protein expressed on glial cells within the brain. Its expression is dramatically down-regulated in many glioblastomas, consistent with its functional ability to inhibit angiogenesis and tumor growth in vivo. We have shown that the soluble anti-angiogenic domain of BAI1 (termed Vstat120) requires CD36, a cell surface glycoprotein expressed on microvascular endothelial cells (MVECs), for it to elicit an anti-angiogenic response. We now report that Vstat120 binding to CD36 on MVECs activates a caspase-mediated pro-apoptotic pathway, and this effect is abrogated by histidine-rich glycoprotein (HRGP). HRGP is a circulating glycoprotein previously shown to function as a CD36 decoy to promote angiogenesis in the presence of thrombospondin-1 or -2. Data here show that Vstat120 specifically binds HRGP. Under favorable MVEC growth conditions this interaction allows chemotactic-directed migration as well as endothelial tube formation to persist in in vitro cellular systems, and increased tumor growth in vivo as demonstrated in both subcutaneous and orthotopic brain tumor models, concomitant with an increase in tumor vascularity. Finally, we show that HRGP expression is increased in human brain cancers, with the protein heavily localized to the basement membrane of the tumors. These data help define a novel angiogenic axis that could be exploited for the treatment of human cancers and other diseases where excess angiogenesis occurs.

The aim of this study was to investigate an in vivo tissue response to a biodegradable polyesterurethane, specifically the cellular and angiogenic response evoked by varying implant architectures in a subcutaneous rabbit implant model. A synthetic biodegradable polyesterurethane was synthesized and processed into three different configurations: a non-porous film, a porous mesh and a porous membrane. Glutaraldehyde cross-linked bovine pericardium was used as a control. Sterile polyesterurethane and control samples were implanted subcutaneously in six rabbits (n=12). The rabbits were killed at 21 and 63 days and the implant sites were sectioned and histologically stained using haemotoxylin and eosin (HE), Masson's trichrome, picosirius red and immunostain CD31. The tissue-implant interface thickness was measured from the HE slides. Stereological techniques were used to quantify the tissue reaction at each time point that included volume fraction of inflammatory cells, fibroblasts, fibrocytes, collagen and the degree of vascularization. Stereological analysis inferred that porous scaffolds with regular topography are better tolerated in vivo compared to non-porous scaffolds, while increasing scaffold porosity promotes angiogenesis and cellular infiltration. The results suggest that this biodegradable polyesterurethane is better tolerated in vivo than the control and that structural variants of biodegradable polyesterurethane in vivo evoke a cellular and angiogenic response that is dictated by architecture.

BACKGROUND. Angiogenesis is reportedly correlated with metastasis, relapse, and prognosis in some types of tumors. Hematogenous or lymph node metastasis and local recurrence are the main elements related to the death of patients with colorectal carcinoma. Thus, the authors examined the microvessel count in colorectal carcinoma to determine how angiogenesis correlates with clinicopathologic factors and prognosis. METHODS. Paraffin embedded sections from 166 patients with primary colorectal carcinomas that had been completely removed were analyzed for angiogenesis. Vessels were stained with anti-factor VIII polyclonal antibody, and areas with the most discrete microvessels were counted in a 400x field. RESULTS. Tumor size was significantly correlated with microvessel count. Microvessel counts from patients with lymph node metastasis, lymphatic vessel invasion, venous vessel invasion, or relapse were significantly higher than those without. Furthermore, microvessel count was an independent prognostic factor (P = 0.007), whereas the Dukes stage had more significant prognostic value (P < 0.001) according to the multivariate Cox hazard analysis. CONCLUSIONS. This study suggested that angiogenesis assessed by the microvessel count was a marker of relapse and prognosis of patients with colorectal carcinoma.

Tumour angiogenesis is an important factor for tumour growth and metastasis. Although some recent reports suggest that microvessel counts in non-small cell lung cancer are related to a poor disease outcome, the results were not conclusive and were not compared with other molecular prognostic markers. In the present study, the vascular grade was assessed in 107 (T1,2-N0,1) operable non-small cell lung carcinomas, using the JC70 monoclonal antibody to CD31. Three vascular grades were defined with appraisal by eye and by Chalkley counting: high (Chalkley score 7-12), medium (5-6), and low (2-4). There was a significant correlation between eye appraisal and Chalkley counting (P < 0.0001). Vascular grade was not related to histology, grade, proliferation index (Ki67), or EGFR or p53 expression. Tumours from younger patients had a higher grade of angiogenesis (P = 0.05). Apart from the vascular grade, none of the other factors examined was statistically related to lymph node metastasis (P < 0.0001). A univariate analysis of survival showed that vascular grade was the most significant prognostic factor (P = 0.0004), followed by N-stage (P = 0.001). In a multivariate analysis, N-stage and vascular grade were not found to be independent prognostic factors, since they were strongly related to each other. Excluding N-stage, vascular grade was the only independent prognostic factor (P = 0.007). Kaplan-Meier survival curves showed a statistically significant worse prognosis for patients with high vascular grade, but no difference was observed between low and medium vascular grade. These data suggest that angiogenesis in operable non-small cell lung cancer is a major prognostic factor for survival and, among the parameters tested, is the only factor related to cancer cell migration to lymph nodes. The integration of vascular grading in clinical trials on adjuvant chemotherapy and/or radiotherapy could substantially contribute in defining groups of operable patients who might benefit from cytotoxic treatment.

The growth of solid tumors to a clinically relevant size is dependent upon an adequate blood supply. This is achieved by the process of tumor stroma generation where the formation of new capillaries is a central event. Progressive recruitment of blood vessels to the tumor site and reciprocal support of tumor expansion by the resulting neovasculature are thought to result in a self-perpetuating loop helping to drive the growth of solid tumors. The development of new vasculature also allows an 'evacuation route' for metastatically-competent tumor cells, enabling them to depart from the primary site and colonize initially unaffected organs. Several molecular and cellular mechanisms have been identified by which tumor parenchyma may exert its angiogenic effect on host endothelial cells. As a result of this paracrine influence, tumor-associated endothelial cells acquire an 'immature' phenotype manifested by rapid proliferation, migration, release of proteases and expression of cytokines, endothelial-specific tyrosine kinases (e.g. flk-1, tek and others) as well as numerous other molecular alterations. Consequently a network of structurally and functionally aberrant blood vessels is formed within the tumor mass. There is also evidence that endothelial cells themselves, and likewise other stromal cells, may act reciprocally to alter the behavior of adjacent tumor cells in a paracrine or cell contact mediated fashion. For example, production of interleukin 6(IL-6) by endothelial cells may have a differential effect on human melanoma cells expressing different degrees of aggressiveness. In this manner endothelial derived cytokines could conceivably contribute to tumor progression by suppressing the growth of the less aggressive tumor cells and promoting dominance of their malignant counterparts in 'strategic' perivascular zones. Distinct biological features expressed by tumor-associated vasculature may serve as potential prognostic markers of disease progression as well as novel targets for therapeutic intervention.

Metastasis is one of the most devastating aspects of cancer. It is a complex multistep processes that results in spread of tumorigenic cells to secondary sites in various organs. The actual events that are involved in metastasis are the subject of several recent reviews [1-3]. Upon growth of neoplastic cells beyond a certain mass (2 mm in diameter) an extensive vascularization through angiogenesis occurs. The new capillary network provides a supply of nutrients and gas exchange that allows further growth and development of the tumor mass. The network of the blood vessels also provides an entry site into the circulation for the neoplastic cells that detach from the tumor mass. Only a small percentage of circulating tumor cells (< 0.01%) survive travel in the circulation and arrest in the capillary beds of distant organs, extravasate and proliferate within the organ parenchyma producing a successful metastasis [1]. Vasculature plays an important role in several steps of the metastatic process; 1) at the site of metastasis, vessels capture the cancer cell and provide the entry route into the secondary organ, and 2) through angiogenesis, vascular endothelial cells provide the supply of nutrients for the growth of the primary tumor mass and the route of intravasation. The lining of all blood vessels are covered with endothelial cells which play an active role in both processes. The metastatic properties of cancer cells have been extensively studied. Here, we will discuss the role of endothelial cells in the metastatic process with focus on their interaction with cancer cells at the site of extravasation.