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In JoVE (1)
Other Publications (6)
Articles by Walter L. Murfee in JoVE
JoVE General
Rat Mesentery Exteriorization: A Model for Investigating the Cellular Dynamics Involved in Angiogenesis
1Department of Biomedical Engineering, Tulane University, 2Department of Biomedical Engineering, University of Virginia, 3Center for Stem Cell Research and Regenerative Medicine, Tulane University
This article describes a simple model for stimulating angiogenesis in the rat mesentery. The model produces dramatic increases in capillary sprouting, vascular area and vascular density over a relatively short time course in a tissue that allows en face visualization of entire microvascular networks down to the single cell level.
Other articles by Walter L. Murfee on PubMed
Enhanced Smooth Muscle Cell Coverage of Microvessels Exposed to Increased Hemodynamic Stresses in Vivo
During vascular remodeling in adult organisms, new capillary growth is often coupled with the adaptation of arterioles and venules, a process that requires the recruitment and differentiation of precursor cells into smooth muscle. We studied the in vivo adaptation of microvessels in the presence of elevated pressure and circumferential wall stress using a ligation strategy for mesenteric microvascular networks. Acute pressure increases of 42.6+/-18% and 17.1+/-2.3% were respectively elicited in the 25- to 30-microm-diameter venules and arterioles supplying the networks. Wall shear rates were not significantly changed; however, diameters were increased in >10-microm-diameter venules and >20-microm-diameter arterioles. Smooth muscle cell contractile phenotype was determined in all microvessels by observing the expression of smooth muscle myosin heavy chain (SM-MHC; a marker of fully differentiated smooth muscle) and smooth muscle alpha-actin (a marker for all smooth muscle, including immature smooth muscle of fibroblast/pericyte lineage). The ratio of SM-MHC positive vessel length to smooth muscle alpha-actin-positive vessel length increased >2-fold after 5 and 10 days of the ligation treatment. Smooth muscle proliferation was studied by bromodeoxyuridine incorporation, and the increase in SM-MHC-labeled microvessel length density was accompanied by no measurable change in proliferation of SM-MHC-labeled cells 5 and 10 days after ligation. These results indicate that after a period of 5 or 10 days, mesenteric microvessels <40 microm in diameter exposed to elevated pressure and wall strain exhibit an enhanced coverage of mature, fully differentiated smooth muscle cells.
Cell Proliferation in Mesenteric Microvascular Network Remodeling in Response to Elevated Hemodynamic Stress
The objective of this study was to quantify the proliferation of existing vascular and perivascular cells during a specific form of microvascular remodeling characterized by increased coverage by smooth muscle cells (SMCs), in response to increased mechanical stress. Coordinated ligations of artery/vein pairs in the rat mesentery resulted in hemodynamic stress elevations within the targeted microvascular network. BRDU incorporation per unit length of smooth muscle (SM) alpha-actin positive vessel was evaluated following ligation at 2, 5, and 10 days. At 2 days, BRDU incorporation was significantly increased for both sham and ligated treatments, but the ligated response was not elevated over the sham response. After 5 days, proliferation for both groups returned to unstimulated levels. The results indicate that moderate elevations in hemodynamic stress do not cause perivascular cell proliferation along rat mesenteric microvessels, therefore, the increased coverage of differentiated SMCs along the same microvessels does not involve proliferation of vascular or perivascular cells.
Differential Arterial/venous Expression of NG2 Proteoglycan in Perivascular Cells Along Microvessels: Identifying a Venule-specific Phenotype
Similar to other vascular pericyte markers, including smooth muscle (SM) alpha-actin, desmin, and PDGF-beta-receptor, NG2 proteoglycan is not pericyte specific. Therefore, the use of NG2 as a pericyte marker, especially in cell lineage studies, in comparison to other nonspecific pericyte markers requires an understanding of how its expression varies spatially within a microvascular network. The objective of this study was to characterize NG2 expression along vessels within rat microvascular networks and compare this to SM alpha-actin expression.
Perivascular Cells Along Venules Upregulate NG2 Expression During Microvascular Remodeling
Recently the authors have shown that neuron-glial antigen 2 (NG2) is expressed by perivascular cells along arterioles and capillaries, but not along venules in quiescent rat mesenteric microvascular networks. To investigate how the spatial distribution of this proteoglycan changes during microvascular remodeling, the objective of this study was to characterize the expression of NG2 in adult rat mesenteric microvascular networks undergoing active remodeling.
Computational Network Model Prediction of Hemodynamic Alterations Due to Arteriolar Remodeling in Interval Sprint Trained Skeletal Muscle
Exercise training is known to enhance skeletal muscle blood flow capacity, with high-intensity interval sprint training (IST) primarily affecting muscles with a high proportion of fast twitch glycolytic fibers. The objective of this study was to determine the relative contributions of new arteriole formation and lumenal arteriolar remodeling to enhanced flow capacity and the impact of these adaptations on local microvascular hemodynamics deep within the muscle.
EphB4 Expression Along Adult Rat Microvascular Networks: EphB4 is More Than a Venous Specific Marker
EphrinB2 and EphB4 are considered to be markers of arterial/venous identity during embryonic development. However, the expression patterns of these arterial/venous-specific markers in adult microvascular networks remain unclear. The objective of this study was to characterize the cellular distribution of EphB4 expression along the hierarchy of unstimulated and remodeling adult rat mesenteric microvascular networks.
