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Abstract: Angiogenesis, the process of new blood vessel formation from preexisting capillaries, is a multistep process. The principle cell type in this process is endothelial cells which are required to undergo proliferation, migration, differentiation, and coalescence into cord-like structures with a central lumen. However, the molecular and cellular mechanisms that regulate this process require further investigation. In this study, we have used the fibrin/fibrinogen-based three-dimensional culture to enrich for primary cultured mouse aortic endothelial cells, and to induce endothelial cell capillary morphogenesis. We found among all the cell surface markers examined that only TEM7 expression was up-regulated upon endothelial cells capillary morphogenesis. In addition, inhibition of capillary morphogenesis by serum stimulation completely blocked TEM7 expression. In contrast, stimulation of endothelial cell capillary morphogenesis with PMA enhanced TEM7 expression. Furthermore, incubation of endothelial cells with a recombinant extracellular domain of TEM7 blocked capillary morphogenesis in three-dimensional cultures. These results suggest that TEM7 is a novel protein whose cell surface expression is essential during endothelial cell capillary morphogenesis. [Copyright &y& Elsevier]

The rat aortic ring model is well utilized for evaluation of angiogenesis. We report here an alternative assay employing an ex vivo mouse aorta angiogenesis model that can be extensively manipulated and serially evaluated using digital-assisted image analysis. Mouse aortas were harvested, cut into 2-mm disks, and cultured in fibrin matrix with growth media. Radial vascular outgrowths arose from the cut edge of the aortic disk and were digitally photographed and serially quantified. A variety of culture conditions were evaluated to determine their ability to alter angiogenesis in this model. Vessel outgrowth became apparent on day 3 and continued through day 10 with linear growth occurring between days 3 and 6. Increasing concentrations of serum from 0% to 40% resulted in stimulation of angiogenesis after day 3. Suramin and endostatin dramatically inhibited angiogenesis, which was more profound when applied at day 0 than when linear growth could be identified (day 3). Cells isolated from vessel outgrowths were predominantly endothelial in origin by immunocytochemistry and FACS analysis. We demonstrate that angiogenesis in an ex vivo murine model can be easily quantified using digital image analysis, responds appropriately to stimulation and inhibition, and exhibits differential results based on time of inhibitor administration. Antiangiogenic agents may be most effective if administered before development of accelerated vessel growth. [Copyright &y& Elsevier]

Abstract: We have reexamined the role of endogenous thrombospondin-1 (TSP1) in growth and motility of vascular smooth muscle cells (SMCs). Based on the ability of aortic-derived SMCs isolated from TSP1 null mice and grown in the absence of exogenous TSP1 to grow at comparable rates and to a slightly higher density than equivalent cells from wild-type mice, TSP1 is not necessary for their growth. Low concentrations of exogenous TSP1 stimulate growth of TSP1 null SMCs, but higher doses of TSP1 or its C-terminal domain are inhibitory. However, SMCs from TSP1 null mice are selectively deficient in chemotactic and proliferative responses to platelet-derived growth factor and in outgrowth in three-dimensional cultures. Recombinant portions of the N- and C-terminal domains of TSP1 stimulate SMC chemotaxis through different integrin receptors. Based on these data, the relative deficiency in SMC outgrowth during an ex vivo angiogenic response of muscle tissue from TSP1 null mice is probably due to restriction of platelet-derived growth factor dependent SMC migration and/or proliferation. [Copyright &y& Elsevier]