Three-dimensional Capillary Network Research Articles

Undernutrition Promotes Oxidative Stress & Capillary Regression In Skeletal Muscle

PURPOSE: An undernutrition condition results in muscle atrophy and mitochondrial dysfunction. However, it is still not well-known that the characteristics of the skeletal muscle capillary network during undernutrition. The purpose of the present study was to verify the effects of undernutrition on the capillary network in skeletal muscle. METHODS: Male Wistar rats were assigned randomly to control and undernutrition groups. The rats in the undernutrition group fed low protein and limited 50% diets daily for 12 weeks. Plantaris and soleus muscle were analyzed. The three-dimensional capillary network of skeletal muscle was visualized using a confocal laser scanning technique. The capillary volume, mean luminal diameter and capillary-to-fiber ratio were measured in both skeletal muscles. In addition, the levels of VEGF and thrombospondin-1 proteins, lipid peroxidation and SOD-2 proteins were determined. RESULTS: The muscle mass decreased only plantaris muscle in the undernutrition group. The level of lipid peroxidation was increased, and the expression levels of SOD-2 in plantaris and soleus muscles were decreased. In addition, the capillary volume, mean luminal diameter and capillary-to-fiber ratio were decreased in both muscles of the undernutrition group. Furthermore, the level of VEGF protein was decreased, and thrombospondin-1 was increased in both muscles of undernutrition group. CONCLUSIONS: These results suggest that undernourished skeletal muscle induces capillary regression with increased oxidative stress, which also occurs in slow muscle without atrophy.

Enterococcus Faecium Strain R30 Attenuates Capillary Regression In Type 2 Diabetic Muscle

It is widely accepted that diabetes affects the peripheral vascular bed. We found that Enterococcus faecium strain R30 (R30) supplementation caused increased velocity of red blood cells in capillaries of skeletal muscle. PURPOSE: We determined the effects of R30 supplementation on the three-dimensional capillary structure in the soleus muscle of Goto-Kakizaki (GK) diabetic rats. R30 supplementation was chosen, because it may be beneficial in management of skeletal muscle and to be safe for individuals with cardiovascular complications such as those associated with diabetes. METHODS: Thirty-six male (Wistar or GK) rats were assigned randomly either to a control (Con), control with R30 supplementation (Con+R30), diabetes (GK) or diabetes with R30 supplementation (GK+R30) group for 8 weeks. The capillaries of soleus muscle were stained with alkaline phosphatase. In addition, the three-dimensional capillary network of soleus muscle was visualized using a confocal laser scanning technique, and the capillary volume and diameter were measured. RESULTS: The blood glucose levels were higher in the GK and GK+R30 groups than in the Con and Con+R30 groups. There were no significant differences in the capillary-to-fiber ratio between the Con and GK+R30 although the ratio was lower in the GK group than in the Con group. The capillary volume and diameter in the muscle of GK group were lower than those in Con group. Meanwhile, R30 supplementation attenuated the decrease of capillary volume and diameter in diabetic muscle. CONCLUSION: These data suggest that R30 supplementation may be an effective treatment to counter the detrimental effects of type 2 diabetic complications in skeletal muscle.

Computational simulations of nanoparticle transport in a three-dimensional capillary network

Objective(s): Multifunctional nanomedicine is the new generation of medicine, which is remarkably promising and associated with the minimum toxicity of targeted therapy. Distribution and transport of nanoparticles (NPs) in the blood flow are essential to the evaluation of delivery efficacy. Materials and Methods: In the present study, we initially designed a phantom based on Murray’s minimum work law using the AutoCAD software. Afterwards, the phantom was fabricated using lithography and imaged using a Siemens Magnetom 3T Prisma MRI scanner at the National Brain Mapping Laboratory, Iran. Finally, the velocity and pressure in the capillary network were simulated using the COMSOL software. Moreover, three-dimensional Navier-Stokes equations were applied to model the NP transport and dispersion in blood suspension. Results: According to the findings, particle size, vessel geometry, and vascular flow rate affected the delivery efficacy and NP distribution. Cerebral blood flow, cerebral blood volume, mean transit time, and curves for the capillary network were obtained at different times. The simulations indicated that the velocity and pressure in the capillary network were within the ranges of 0.0001-0.0005 m/s and 5-25 mm/Hg, respectively. Higher particle concentration was also observed in the non-uniform NP distribution profile near the vessel wall. Conclusion: We investigated the effects of the vessel size and geometry and particulate nature of blood on the delivery and distribution of NPs. For targeted drug delivery applications, a mechanistic understanding on the nanomedicine design was provided as well.

Blood flow and transport in the human placenta.

The placenta is a multi-functional organ that exchanges blood gases and nutrients between a mother and her developing fetus. In humans, fetal blood flows through intricate networks of vessels confined within villous trees, the branches of which are bathed in pools of maternal blood. Fluid mechanics and transport processes play a central role in understanding how these elaborate structures contribute to the function of the placenta, and how their disorganization may lead to disease. Recent advances in imaging and computation have spurred significant advances in simulations of fetal and maternal flows within the placenta, across a range of lengthscales. Models describe jets of maternal blood emerging from spiral arteries into a disordered and deformable porous medium, and solute uptake by fetal blood flowing through elaborate three-dimensional capillary networks. We survey recent developments and emerging challenges in modeling flow and transport in this complex organ.

Computational Simulations of Flow and Oxygen/Drug Delivery in a Three-Dimensional Capillary Network

A computational fluid dynamics (CFD) model is developed to simulate the flow and delivery of oxygen and other substances in a capillary network. A three-dimensional capillary network has been constructed to replicate the one studied by Secomb et al. (2000), and the computational framework features a non-Newtonian viscosity model of blood and the oxygen transport model including in-stream oxygen-hemoglobin dissociation and wall flux due to tissue absorption, as well as an ability to study delivery of drugs and other materials in the capillary streams. The model is first run to compute the volumetric flow rates from the velocity profiles in the segments and compared with Secomb’s work with good agreement. Effects of abnormal pressure and stenosis conditions, as well as those arising from different capillary configurations, on the flow and oxygen delivery are investigated, along with a brief look at the unsteady effects and drug dispersion in the capillary network. The current approach allows for inclusion of oxygen and other material transports, including drugs, nutrients, or contaminants based on the flow simulations. Also, three-dimensional models of complex circulatory systems ranging in scale from macro- to microvascular vessels, in principle, can be constructed and analyzed in detail using the current method.

Regressed three-dimensional capillary network and inhibited angiogenic factors in the soleus muscle of non-obese rats with type 2 diabetes

Based on findings obtained using two-dimensional capillary analyses on tissue cross-sections, diabetes has been shown to be associated with a high risk for microangiopathy and capillary regression in skeletal muscles. We visualized the three-dimensional architecture of the capillary networks in the soleus muscle of non-obese Goto-Kakizaki (GK) rats with type 2 diabetes and compared them with those of control Wistar rats to provide novel information, e.g., capillary volume, on the capillary networks. In addition, we examined pro- and anti-angiogenic gene expression levels in the soleus muscle of GK rats using TaqMan probe-based real-time PCR. As expected, plasma glucose levels were higher and insulin levels lower in GK than control rats. The three-dimensional architecture of the capillary networks was regressed and capillary volume was smaller in the soleus muscle of GK compared to control rats. The mRNA expression levels of the pro-angiogenic factors HIF-1α, KDR, Flt-1, ANG-1, and Tie-2 were lower, whereas the level of the anti-angiogenic factor TSP-1 was higher in GK than control rats. These data suggest that a decrease in pro-angiogenic and increase in anti-angiogenic factors may play an important role in type 2 diabetes-induced muscle circulatory complications.

Low‐Intensity Exercise Training Prevents Muscular Microangiopathy in Non‐obese Type 2 Diabetic Rats

PURPOSEThe purpose of the present study was to investigate the effects of low‐intensity exercise training on the angiopathy of skeletal muscle by type 2 diabetes.METHODSMale Goto‐Kakizaki (GK) non‐obese type 2 diabetic rats (6 weeks old) and wild‐type Wistar rats (Con) were used. GK rats divided into 2 groups: diabetes (GK) and diabetes plus low‐intensity exercise training (GK+Ex). The low‐intensity exercise training was conducted during 60 min, 5 times per week, for 3 weeks. The three‐dimensional capillary network of soleus muscle was visualized using a confocal laser microscopy. The mRNA expression levels of angiogenic factors (VEGF, KDR, Flt‐1, Ang‐1, Ang‐2, Tie‐2, and HIF‐1 alpha) in the soleus muscle were determined by TaqMan probe‐based real‐time PCR.RESULTSThe capillary volume in the muscle was lower in GK than in Con rats. However, the capillary volume in the muscle of GK+Ex was increased toward to the level of Con rats. Although the expression levels of angiogenic factors in the muscle were lower in GK than in Con, those were increased toward to the levels of those in GK+Ex rats.CONCLUSIONThe present results provide evidence of the effectiveness of endurance exercise training that reduces the muscle circulatory complications associated with type 2 diabetes. Supported by Grants‐in‐Aid for Science Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology, no. 22300189.

SNS-032 Prevents Tumor Cell-Induced Angiogenesis By Inhibiting Vascular Endothelial Growth Factor

Cell proliferation, migration, and capillary network formation of endothelial cells are the fundamental steps for angiogenesis, which involves the formation of new blood vessels. The purpose of this study is to investigate the effect of a novel aminothiazole SNS-032 on these critical steps for in vitro angiogenesis using a coculture system consisting of human umbilical vein endothelial cells (HUVECs) and human glioblastoma cells (U87MG). SNS-032 is a potent selective inhibitor of cyclin-dependent kinases 2, 7, and 9, and inhibits both transcription and cell cycle. In this study, we examined the proliferation and viability of HUVECs and U87MG cells in the presence of SNS-032 and observed a dose-dependent inhibition of cellular proliferation in both cell lines. SNS-032 inhibited threedimensional capillary network formations of endothelial cells. In a coculture study, SNS-032 completely prevented U87MG cell-mediated capillary formation of HUVECs. This inhibitor also prevented the migration of HUVECs when cultured alone or cocultured with U87MG cells. In addition, SNS-032 significantly prevented the production of vascular endothelial growth factor (VEGF) in both cell lines, whereas SNS-032 was less effective in preventing capillary network formation and migration of endothelial cells when an active recombinant VEGF was added to the medium. In conclusion, SNS-032 prevents in vitro angiogenesis, and this action is attributable to blocking of VEGF.

Prevention of mammary cancer with conjugated linoleic acid: role of the stroma and the epithelium.

Conjugated linoleic acid (CLA), found naturally in dairy products and ruminant meats, refers to isomers of octadecadienoic acid with conjugated double bonds. CLA inhibits both DMBA- and NMU-induced rat mammary carcinogenesis, and its antitumor efficacy is similar whether it is fed only during puberty, or continuously during promotion. Pubertal feeding is associated with a reduced proliferation of the epithelial cells within the terminal end buds (TEBs) and lobular epithelium, and results in a decrease in the epithelial density, suggesting a reduction in the carcinogen-sensitive target population. During promotion, CLA feeding induces apoptosis of preneoplastic lesions. The effects of CLA are mediated by a direct action on the epithelium, as well as by an indirect effect through the stroma. CLA is incorporated into the neutral lipids of mammary adipocytes, where it can serve as a local reservoir of CLA. Additionally, CLA induces the adipogenic differentiation of multipotent mammary stromal cells in vitro, and inhibits their development into three-dimensional capillary networks. This suggested that CLA might inhibit angiogenesis in vivo, a hypothesis that was subsequently confirmed. The antiangiogenic effect is mediated, in part, through a CLA-induced decrease in serum VEGF (vascular endothelial growth factor) and mammary gland VEGF and flk-1. Together, the data suggest that CLA may be an excellent candidate for prevention of breast cancer.

Modeling advection and diffusion of oxygen in complex vascular networks.

A realistic geometric model for the three-dimensional capillary network geometry is used as a framework for studying the transport and consumption of oxygen in cardiac tissue. The nontree-like capillary network conforms to the available morphometric statistics and is supplied by a single arterial source and drains into a pair of venular sinks. We explore steady-state oxygen transport and consumption in the tissue using a mathematical model which accounts for advection in the vascular network, nonlinear binding of dissolved oxygen to hemoglobin and myoglobin, passive diffusion of freely dissolved and protein-bound oxygen, and Michaelis-Menten consumption in the parenchymal tissue. The advection velocity field is found by solving the hemodynamic problem for flow throughout the network. The resulting system is described by a set of coupled nonlinear elliptic equations, which are solved using a finite-difference numerical approximation. We find that coupled advection and diffusion in the three-dimensional system enhance the dispersion of oxygen in the tissue compared to the predictions of simplified axially distributed models, and that no "lethal corner," or oxygen-deprived region occurs for physiologically reasonable values for flow and consumption. Concentrations of 0.5-1.0 mM myoglobin facilitate the transport of oxygen and thereby protect the tissue from hypoxia at levels near its P50, that is, when local oxygen consumption rates are close to those of delivery by flow and myoglobin-facilitated diffusion, a fairly narrow range.

Microvasculature of hydronephrotic kidneys in KK-A(Y) mice.

Spontaneous hydronephrosis in KK-A(Y) mice was studied using light and electron microscopy and scanning electron microscopy of resin casts to evaluate micro vascular changes in the kidney. The renal parenchyma was extremely thin as a result of tubular atrophy. Histologically, varying degrees of glomerulosclerosis were observed. Ultrastructurally, marked thickenings of the glomerular basal lamina, an increase in mesangial cells and matrix, and marked effacement of foot processes were observed. In resin casts, a marked reduction in number of glomeruli was evident. The capillaries were thin, strangulated and tom-off to varying degrees in severely affected glomeruli. In the medulla, the three-dimensional capillary network running along the tubules was lost and changed to a two-dimensional vascular bed. Despite severe hydronephrosis, the glomerular capillary network was relatively well preserved, being either slightly or moderately injured in approximately 60% of surviving glomeruli.

Three-dimensional analysis of the developing pituitary gland in the mouse.

Prenatal development of the mouse pituitary gland was analyzed in three-dimensions by using confocal laser-scanning microscopy. In any wholemount preparation of the fetal pituitary gland from day 10 to day 18, immunofluorescence of laminin was observed in the deeper regions of the organ and demarcated the boundary of the epithelial tissue from the surrounding mesenchyme. Three-dimensional capillary networks in the fetal pituitary gland at day 13, day 15, and day 18 were visualized clearly by perfusing the blood vessels with an fluorescein isothiocyanate-labelled gelatin solution. During days 12-14, cellular plates protruded from the anterior wall of the pituitary anlage and extended toward the base of the infundibulum. At the same time, the mesenchyme situated among the cellular plates separated from the surrounding mesenchyme except at the anteroventral portion of the anlage. In a posterior wall of the anlage, intercellular depositions of laminin were found among the epithelial cells, some of which reached the laminin sheet in the basement membrane of the anlage. From days 15-18, the pituitary gland enlarged, and the mesenchyme spread radially from the median anteroventral portion to the lateral, posterior, and dorsal regions and finally expanded throughout the entire organ. At the periphery, the mesenchyme in the pituitary gland connected with that surrounding the capsule. Laminin was still found in the intercellular spaces between the epithelial cells, and most of the intercellular depositions of laminin were combined with the laminin sheet in the epithelial basement membrane. An abundance of vessels entered the organ from its anteroventral portion, spread, and connected with one another throughout the gland, similar to the distribution of mesenchyme. Intercellular laminin would induce the polarization of the contacting epithelial cells, resulting in rearrangement of the epithelial cells. The mesenchyme might spread in the pituitary gland, providing the intercellular laminin a foothold, in order to cleave the epithelial cell mass into lobules. The development of capillary nets in the adenohypophysis corresponded well with that of the mesenchyme. Because laminin localizes mainly in the basement membrane in the fetal organs, immunostaining of laminin clearly indicates the boundary between epithelial tissue and the mesenchyme. Three-dimensional observation of laminin in wholemount preparation is very useful for studying morphogenesis.