Adenoviral delivery of a constitutively active retinoblastoma mutant inhibits neointima formation in a human explant model for vein graft disease

Studies on the Tumor Vasculature and Coagulant Microenvironment

Angiogenesis represents one aspect in the complex process that leads to the generation of the vascular tumor stroma. The related functional constituents include responses of endothelial, mural, bone marrow-derived, and resident inflammatory cells as well as activation of coagulation and fibrinolytic systems in blood. Multiple molecular and cellular effectors participate in these events, often in a tumor-specific manner and with changes enforced through the microenvironment, genetic evolution, and responses to anticancer therapies. To capture various elements of these interactions several surrogate assays have been devised, which can be mechanistically useful and are amenable to quantification, but are individually insufficient to describe the underlying complexity and are best used in a targeted and combinatorial manner. Below, we present a survey of angiogenesis assays and experimental approaches to analyze vascular events in cancer. We also provided specific examples of validated protocols, which are less described, but enable the straightforward analysis of vascular structures and coagulant properties of cancer cells in vivo and in vitro.

Techniques and assays for the study of angiogenesis

The importance of studying angiogenesis, the formation of new blood vessels from pre-existing vessels, is underscored by its involvement in both normal physiology, such as embryonic growth and wound healing, and pathologies, such as diabetes and cancer. Treatments targeting the molecular drive of angiogenesis have been developed, but many of the molecular mechanisms that mediate vascularization, as well as how these mechanisms can be targeted in therapy, remain poorly understood. The limited capacity to quantify angiogenesis properly curtails our molecular understanding and development of new drugs and therapies. Although there are a number of assays for angiogenesis, many of them strip away its important components and/or limit control of the variables that direct this highly cooperative and complex process. Here we review assays commonly used in endothelial cell biology and describe the progress toward development of a physiologically realistic platform that will enable a better understanding of the molecular and physical mechanisms that govern angiogenesis.

Mechanisms of vein graft adaptation to the arterial circulation: insights into the neointimal algorithm and management strategies

For patients with coronary artery disease or limb ischemia, placement of a vein graft as a conduit for a bypass is an important and generally durable strategy among the options for arterial reconstructive surgery. Vein grafts adapt to the arterial environment, and the limited formation of intimal hyperplasia in the vein graft wall is thought to be an important component of successful vein graft adaptation. However, it is also known that abnormal, or uncontrolled, adaptation may lead to abnormal vessel wall remodeling with excessive neointimal hyperplasia, and ultimately vein graft failure and clinical complications. Therefore, understanding the venous-specific pathophysiological and molecular mechanisms of vein graft adaptation are important for clinical vein graft management. Of particular importance, it is currently unknown whether there exist several specific distinct molecular differences in the venous mechanisms of adaptation that are distinct from arterial post-injury responses; in particular, the participation of the venous determinant Eph-B4 and the vascular protective molecule Nogo-B may be involved in mechanisms of vessel remodeling specific to the vein. This review describes (1) venous biology from embryonic development to the mature quiescent state, (2) sequential pathologies of vein graft neointima formation, and (3) novel candidates for strategies of vein graft management. Scientific inquiry into venous-specific adaptation mechanisms will ultimately provide improvements in vein graft clinical outcomes.

Effectiveness of narrow-band ultraviolet-B phototherapy for prevention of intimal hyperplasia in a rat carotid balloon injury model

BACKGROUND AND OBJECTIVE

Narrow-band ultraviolet-B light (NBUVB) (313 nm) is known to have anti-proliferative effects, implying a potential treatment for intimal hyperplasia, but it remains to be ascertained. We assessed the effects of NBUVB irradiation for prevention of intimal hyperplasia.

STUDY DESIGN/MATERIALS AND METHODS

The rat carotid arteries were irradiated with NBUVB after balloon injury (BI), and the degree of intimal hyperplasia was histopathologically assessed. The anti-proliferative effects using cultured human smooth muscle cells were evaluated by flow cytometry and immunoblot analysis.

RESULTS

NBUVB (0.3-4.5 J/cm(2)) irradiation immediately after BI reduced the degree of intimal hyperplasia at 14 and 28 days after BI (P<0.001) without any obvious complications. Neither an increase in the number of medial cells nor upregulation of proliferating cell nuclear antigen was observed in the irradiated arteries. NBUVB irradiation at 2 or 14 days after BI significantly suppressed further intimal hyperplasia (P<0.01). NBUVB-irradiated cultured cells showed inhibited proliferation involved with G(1) and G(2)/M arrests. Increased expression of p53 and inhibition of retinoblastoma protein (pRB) phosphorylation were also seen in the NBUVB-irradiated cells.

CONCLUSIONS

These data suggest that NBUVB irradiation is an effective method for preventing intimal hyperplasia. The anti-proliferative effect is partly due to the cell cycle arrest caused by p53 expression and inhibited pRB phosphorylation.

Anti-MCP-1 gene therapy inhibits vascular smooth muscle cells proliferation and attenuates vein graft thickening both in vitro and in vivo

OBJECTIVE

Because late vein graft failure is caused by intimal hyperplasia (IH) and accelerated atherosclerosis, and these processes are thought to be inflammation driven, influx of monocytes is one of the first phenomena seen in IH, we would like to provide direct evidence for a role of the MCP-1 pathway in the development of vein graft disease.

METHODS AND RESULTS

MCP-1 expression is demonstrated in various stages of vein graft disease in a murine model in which venous interpositions are placed in the carotid arteries of hypercholesterolemic ApoE3Leiden mice and in cultured human saphenous vein (HSV) segments in which IH occurs. The functional involvement of MCP-1 in vein graft remodeling is demonstrated by blocking the MCP-1 receptor CCR-2 using 7ND-MCP-1. 7ND-MCP1 gene transfer resulted in 51% reduction in IH in the mouse model, when compared with controls. In HSV cultures neointima formation was inhibited by 53%. In addition, we demonstrate a direct inhibitory effect of 7ND-MCP-1 on the proliferation of smooth muscle cell (SMC) in HSV cultures and in SMC cell cultures.

CONCLUSIONS

These data, for the first time, prove that MCP-1 has a pivotal role in vein graft thickening due to intimal hyperplasia and accelerated atherosclerosis.