Physiological Cyclic Stretch Inhibits Vascular Smooth Muscle Cell Migration via Activating AMPK Phosphorylation / 医用生物力学

Objective To explore the role of adenosine monophosphate-activated protein kinase (AMPK), a key regulator of cellular energy metabolism, in vascular smooth muscle cell (VSMC) migration in response to physiological cyclic stretch. Methods The Flexcell-5000T mechanical loading system was applied with a physiological cyclic stretch at 10% amplitude and 1.25 Hz frequency to primary rat VSMCs, to simulate mechanical stimulation of VSMCs in vivo. The protein expression of p-AMPK in VSMCs was detected by Western blotting, and VSMC migration was detected by wound healing test. Results Compared with the static group, physiological cyclic stretch loading for 24 h significantly decreased the area of wound healing, indicating that physiological cyclic stretch inhibited VSMC migration. The protein expression of p-AMPK in VSMCs was increased significantly after physiological cyclic stretch loading for 3 h, and was decreased significantly after 24 h. Under physiological cyclic stretch loading conditions, incubating AMPK inhibitor could significantly reduce the protein expression of p-AMPK after 3 h, and promote VSMC migration after 24 h; incubating AMPK activator AICAR under static conditions significantly increased the protein expression of p-AMPK after 3 h, and weakened VSMC migration after 24 h. Conclusions Physiological cyclic stretch inhibits VSMC migration by increasing the protein expression of p-AMPK, indicating that VSMC migration regulated by physiological cyclic stretch is of great significance for maintaining vascular homeostasis.

Preliminary study on the mechanism of spontaneous rhythmic contraction in rabbit portal vein / 生物医学工程学杂志

This study sought to probe into the mechanism of spontaneous contraction of portal vein. The morphological and electrophysiological characteristics of the freshly isolated interstitial cells (ICs) of rabbit portal vein were investigated by using immunohistochemical and conventional whole-cell patch clamp techniques. The isolated interstitial cells exhibited stellate-shaped or spindle-shaped bodies with a variable number of thin processes projecting from cell bodies, and these cells were noted to be c-Kit immunopositive. Under conventional whole-cell patch clamp configuration, the membrane potential was held at -60 mV, the spontaneous rhythmic inward currents were recorded in ICs, and the frequencies of which were similar to those of spontaneous contraction of portal vein. The inward currents were insensitive to nicardipine (an L-type calcium channel blocker) but could be abolished by gadolinium (a non-selective cation channel blocker). The results suggested that the spontaneous rhythmic inward currents recorded in freshly isolated ICs may be pacemaker currents which elicit the spontaneous contraction of portal vein.

Expression of RhoGDIα in aortae of hypertensive rats / 解剖学报

Objective To evaluate the role of angiotensin Ⅱ(AngⅡ) signal passway on the expression of Rho GDP dissociation inhibitor alpha (RhoGDIα) in hypertensive rats. Methods Protein and mRNA expressions of RhoGDIα in aortae of 4, 12 and 18 week-old spontaneously hypertensive rats (SHR, n = 4) and Wistar Kyoto rats (WKY, n= 4) were examined by Western blotting and real-time PCR. Aortas from SHR and WKY were analyzed using immonuchemical staining to locate the RhoGDIα in the aorta. The RhoGDIα expression in aorta of hypertensive rat model of aorta coarctation (ACR, n = 6) was also analyzed using Western blotting. Furthermore, The effect of mechanical strain at 10 % elongation on expression of RhoGDIα in vascular smoothmuscle cells (VSMCs) in the presence or absence of L-158809, an antagonist for AngⅡ type 1 receptor, was also evaluated by Western blotting. Results No significant difference of RhoGDIα expression was found between SHR and WKY at 4-week-old and 12-week-old. However, in 18-week-old group, RhoGDIα was significantly highly expressed in SHR than that of WKY at both mRNA and protein levels. RhoGDIα was located in the media of the aorta. Expression of RhoGDIα protein was upregulated in aortas of ACR at 2 and 4 weeks as compared with the controls. The expression of RhoGDIα in VSMCs was inhibited by mechanicalstrain at 10 % elongation, and further decreased by treatment of L-158809. Conclusion RhoGDIα is upregulated in aortae of the hypertensive rats. AngⅡ signal passway may be involved in the process of regulating expression of RhoGDIα.

Effect of frequency of cyclic tensile strain on extracellular matrix of rat vascular smooth muscle cells in vitro / 生物医学工程学杂志

To investigate the effect of different frequencies of cyclic tensile strain on extracellular matrix (ECM) of vascular smooth muscle cells (VSMCs) and to research the relationship between tensile strain and vascular remodeling, the aortic vascular smooth muscle cells of rats grown on dishes coated with collagen I were subjected to 10% elongation and various frequencies of mechanical strain using the Flexercell 4000 Strain Unit. The expression of extracellular matrix including fibronectin, collagen I and collagen III was detected by Real-time RT-PCR, and p38 activity by western blot. The result showed that the expression of extracellular matrix was induced by mechanical strain in a nonlinear frequency-dependent manner, which was mediated by p38 pathway. These results demonstrate that the variety of frequencies of cyclic tensile strain could modulate the expression of ECM. It may have important influence on vascular remodeling.

Stresses in portal venous system of pre-hepatic portal hypertension (PHT) rabbits / 生物医学工程学杂志

Portal hypertension is a common physiopathological change in liver cirrhosis. In this study, rabbits were used and the model of pre-hepatic portal hypertension (PHT) was induced by partial ligation of portal vein in two steps. We measured the diameters of portal vein and small mesenteric vein at different time-points. Then we detected the stress forces induced by blood flow in varicose veins and in portal vein; such forces included hydrostatic pressure, shear stress and circumferential stress. With the increase of the diameter of varicose small mesenteric vein, the hydrostatic pressure and circumferential stress gradually elevated and shear stress descended markedly in both the portal vein and the small mesenteric vein of PHT rabbits, between which there was a positive linear correlation. The findings in our study indicate that the complications of PHT are partially attributable to the environment of lower shear stress and higher circumferential stress in which the blood vessels of portal venous system live.

Primary research of reconstruction of complete biological tissue engineered blood vessel / 生物医学工程学杂志

To explore primarily the reconstruction of biological tissue engineered blood vessel in vitro, the decellularised scaffolds were obtained from swine common carotid arteries by enzyme digestion, and vascular smooth muscle cells (VSMCs) were isolated from canine thoracic aorta and subcultured and purified. The VSMCs were seeded into the inner surface of scaffolds and they were cocultured in vitro for 4 weeks. Histological staining and transmission electron microscopy were used to observe the growth of canine VSMCs on swine decellularized arterial scaffolds. The results showed the seeded VSMCs grew well on the decellularized scaffold throughout the duration of 4 weeks, which suggests that the method in this article is practicable for reconstructing complete biological tissue engineering blood vessel.

Effects of low shear stress on expression of platelet derived growth factor (PDGF) of organ-cultured artery in vitro / 生物医学工程学杂志

To explore the biological effects of shear stress on intact artery and the change of growth factor during stress-induced vascular remodeling, we established an artery organ-cultured system under stress in vitro, and the common carotid arteries of pigs were cultured under shear stress of 20, 5 and 0 dyn/cm2. PDGF-A synthesis of vascular smooth muscle cells (VSMCs) cultured for 1, 4 and 7 days were studied by immunohistochemical and computer image processing methods, and PDGF-B secretion of endothelial cells (ECs) cultured within 12 h were studied by ELISA. Results showed that PDGF-B increased obviously under shear stress of 5 dyn/cm2, and reached the highest point at about 3 h; PDGF-A synthesis also obviously increased under low shear stress in 7 days. Increasing of PDGF synthesis promotes phenotype switch and proliferation of VSMC. It may have important influence on artery remodeling under low shear stress.

Pressure-induced expression of immediate-early gene product c-Jun of the common carotid arteries in rats / 生物医学工程学杂志

In order to investigate the mechanism of mechanical stress-mediated arterial remodeling, we studied the pressure-induced expression of immediate-early response gene product c-Jun in common carotid arteries in rats. The common carotid arteries were perfused with both high pressure (160 mmHg) and normal pressure (80 mmHg) for 0.5, 1, 3 and 6 hours. Expression of immediate-early response gene product c-Jun in the arteries was examined by immunohistochemistry and computer image processing. c-Jun was weakly expressed at 1 h, then increased at 3 h and 6 h after exposure of the arteries to normal pressure. Positive immunohistochemical product of c-Jun appeared in the arteries at 0.5 h after the onset of high pressure, then it increased markedly till 6 h. There was significant difference between the two groups. These results indicate that expression of c-Jun of the arteries can be induced by pressure, which may play an important role in mechanical stress-mediated arterial remodeling.

Effect of captopril on expression of PTEN in aorta of aortic-induced hypertensive rats / 生物医学工程学杂志

This study inquired about the role of tumor suppressor PTEN in the arterial remodeling of Ang II induced hypertension. The expression of PTEN of aorta was examined in the aortic-constricted hypertensive rats (hypertension group), in the aortic-constricted hypertensive rats treated with captopril(hypertension and captopril group), and in the rats having undergone sham operation (control group). At day 28 after surgery, the aortas were collected from the groups. The expression of PTEN mRNA was detected by RT-PCR. The expression and location of PTEN protein were determined by immunohistochemistry. The results showed that the expression of PTEN in aorta of the hypertension group was significantly lower than that of the hypertension and captopril group, and similarly lower than that of the control group. The intensity of PTEN-positive immunohistochemical production in aorta of the hypertension group was weaker than that of the hypertension and captopril group, and likewise, it was weaker than the control. PTEN-positive immunohistochemical production was located in VSMC of aorta. The findings indicated that the expression of PTEN is reduced in hypertensive aorta, that the reduced PTEN experession can be reversed by captopril treatment, that AngII and the increased mechanical strain may participate in regulating expression of PTEN, and that PTEN may play a role in the arterial remodeling induced by hypertension.

The effect of high pressure on morphology, expression of alpha-actin and proliferating cell nuclear antigen of vascular smooth muscle cells--a new model of common carotid artery exposed to stress in vivo / 生物医学工程学杂志

To investigate the role and mechanism of mechanical stress on arterial remodeling, a new model of common carotid artery exposed to stress in vivo was established in rat, in which the change of pressure is the only influencing factor. The effect of high pressure on the morphology and expression of alpha-actin and proliferating cell nuclear antigen (PCNA) of vascular smooth muscle cells (VSMCs) in the artery was assessed. The arteries were perfused by both high pressure (160 mmHg) and normal pressure (80 mmHg) for 6 hours. The changes of morphology, expression of alpha-actin and PCNA in VSMCs were studied by histology and immunohistochemistry. The results showed that the new model could be controlled well in pressure and frequency. The euchromatin was increased and PCNA-positive particles were observed in the nuclei of VSMCs, but the expression of alpha-actin was decreased when the arteries were exposed to the high pressure. The new model has been successfully established, which provides a new tool for studying the effect of mechanical stress on arterial remodeling. In this experiment, VSMCs underwent a transformation from contractile phenotype into synthetic phenotype and tended to proliferate in response to the high pressure.

IDENTIFICATION OF PI3K/Akt PATHWAY RELATED GENES IN VASCULAR SMOOTH MUSCLE CELLS SUBJECTED TO CYCLIC STRAIN / 解剖学报

Objective To screen out the PI3K/Akt pathway related genes in vascular smooth muscle cells (VSMCs) subjected to cyclic strain. Method VSMCs of rat aorta were subjected to cyclic strain (10 %, 1 Hz) by using a FX-4000T system. Phosphorylation of Akt was examined by Western blotting. Suppression subtractive hybridization (SSH) method was employed to analyze the differently expressed cDNA sequence between the strained VSMCs pretreated with and without wortmannin, a specific inhibitor of PI3K. These fragments were ligated with T vectors, screened through the blue-white screening system to establish cDNA library, and was sequenced and analyzed in GenBank with BLASTN search.Result Level of Akt phosphorylation of VSMCs was significantly enhanced by the mechanical strain compared with the control. Ten different expressed sequence tags (EST) were gained after sequencing 30 clones randomly selected from 54 white clones. There may be six genes related with the mechanical strain and cell signal PI3K/Akt, such as High mobility group box 1 (HMGB1), Neural precursor cells expressed (Nedd4a), Cyclin-dependent kinase 5 (CDK5), Histone deacetylase 3 (HDAC3), Ubiquitin-like 1 (Uble1a) and Heterogeneous nuclear ribonucleoprotein H1 (hnRNP). Conclusion SSH is an effective and reliable approach to screen out the genes related with the mechanical strain and PI3K/Akt pathway in VSMCs.

EFFECTS OF LOW SHEAR STRESS ON DEVEIOPMENT AND EXPRESSION OF ?-ACTIN AND c-Myc OF VASCULAR SMOOTH MUSCLE CELLS OF COMMON CAROTID ATHEROSCLEROSIS / 解剖学报

Objective To investigate effects of low shear stress on atherosclerosis,the development of atherosclerosis and expression of ?actin and cMyc proteins were studied in VSMC of common carotid artery under low shear stress. Methods We established the atherosclerotic model of left common carotid artery that presented low shear stress by the operation of ligating the left external carotid artery in rabbits.The histomorphology of the carotid arteries was examined by light microscopy.The expression of ?actin and cMyc was studied by immunohistochemistry. Results The typical atherosclerosis was observed and the atherosclerotic lesion was obviously accelerated under low shear stress.The expression of ?actin was downregulated and the phenotype of VSMC converted from contractile phenotype into synthetic phenotype,and expression of cMyc increased in VSMC of the artery under low shear stress.Conclusion This new model of atherosclerosis under low shear stress was successfully established,which provides a new tool for studying the effects of low shear stress on atherosclerosis.The results show that the atherosclerotic lesion is obviously accelerated and VSMC tends to proliferate in response to low shear stress.

Changes in extracellular matrix of endothelial cells co-cultured with VSMC under shear stress / 生物医学工程学杂志

The construction and amount of fibronectin (Fn), laminin (Ln) and collagen type IV (ColIV) in the extracellular matrix of endothelial cells (EC) co-cultured with vascular smooth muscle cells (VSMC) under shear stress were studied by immuno-fluoro-cytochemistry, laser confocal scanning microscopy and image analysis methods to detect the effect of shear stress on adhesion of EC for vascular tissue engineering. One group of EC was maintained under static conditions as a control. In the control, both Fn and Ln exhibited as a granular pattern in perinuclear area and a fibrillar pattern localized underneath EC, and Col IV exhibited mainly as the granular in the perinuclear area, but the fibrillar was fewer. On exposure of EC to shear stress in physiological range, Fn grouped into fibril tracts, and there was a tendency for some of these tracts of fibrils to align with direction of shear stress. Ln and Col IV also grouped into fibril tracts, which, in contrast to Fn, were randomly oriented, Simultaneously, all contents of the extracellular matrix had different quantitative alterations. These results suggest that the capability of adhesion of EC co-cultured with VSMC may be strengthened under shear stress.

Effects of angiotensin II receptor antagonist on remodeling of renal arterioles in hypertension / 中国病理生理杂志

AIM: To investigate the effects of angiotensin II receptor antagonist on remodeling of renal arterioles in hypertension. METHODS: Eighteen 4 weeks old male rats were divided into three groups: Wistar-Kyoto rats (WKY) for normotensive group, and spontaneously hypertensive rats (SHR) for hypertensive group, and SHR treated with losartan orally (15 mg?kg -1 ?d -1 ). The rats were raised to 16 weeks old. The morphometric parameters of the renal arterioles, and the widths of vascular smooth muscle cells (VSMC) and intercellular space were studied on kidney slices by light microscope and electromicroscope respectively, combined with computer-assistant image analysis system. The minimal renal vascular resistance (RVR min ) was studied by isolated kidney perfusion system. RESULTS: The systolic blood pressure of the tail artery, wall thickness, wall area, ratio of wall thickness to inner diameter, width of VSMC of renal arterioles and RVR min were all smaller or lower in losartan group than those of SHR. CONCLUSION: Ang II receptor antagonist losartan can prevent the remodeling of renal arterioles in SHR.

Effect of pulsating pressure on secretion of angiotensin Ⅱ by common carotid artery in rats in vivo / 第二军医大学学报

Objective: To study the effect of pulsating pressure on secretion of angiotensin Ⅱ(AngⅡ) by common carotid artery. Methods: The common carotid arteries of rats were perfused with both high pulsating pressure (160 mmHg,1 mmHg=0.133 kPa) and normal pulsating pressure (80 mmHg) for 0.5, 1, 3 and 6 h in vivo respectively. The concentration of AngⅡ in the perfusion medium were determined by radioimmunoassay (RIA). Results: The concentration of AngⅡ in the perfusion medium of the common carotid artery increased with perfusion time. Secretion of AngⅡ was higher in 160 mmHg group than that in 80 mmHg group( P

Effect of angiotensin Ⅱ on the remodeling of aorta in spontaneously hypertensive rats / 中国病理生理杂志

AIM: To investigate the effects of a 10-weeks treatment with angiotensin Ⅱ (Ang Ⅱ) subtype I receptor antagonist losartan on vascular remodeling of thoracic aorta in male spontaneously hypertensive rats (SHR). METHODS: SHR were treated from 16 to 26 weeks of age with losartan at 15 mg/kg?d -1 or 0.75 mg/kg?d -1. RESULTS: Losartan (15 mg/kg?d -1) treatment significantly decreased systolic blood pressure compared with the control group, while losartan (0.75 mg/kg?d -1) had no the effect, losartan(15 mg) prevents the development of aortic hypertrophy by preventing hypertrophy of vascular smooth muscle cells (VSMC). In the losartan 0.75 group, these parameters were not changed. But in the losartan 15 and losartan 0.75 groups, the collagen content of the aortic media decreased significantly. CONCLUSION: It is inferred that the effect of Ang Ⅱ on stimulating VSMC growth of the aorta in SHR is dependent on arterial pressure, while the effect on collagen fibers is through pressure independent mechanism.

Geometrical Morphology of the Human Coronary Arteries / 第三军医大学学报

Five resin casts of the coronary arteries and the hislological sections of three hesrts with the arteries injected Chinese ink were prepared in human adult autopsy subjec s . 3187 branches of the coronary arterial trees were counted and measured . By Strahler's system the branch pattern of the coronary arterial tree was described . According to the analysis of the geometrical morphology data, the relationships between the diameter , the length and the number of branches in each order and the branch order show the exponential function respectively , which have high correlation significance (p

Bio mechanical Properties of Coronary Aiteries in Human Ⅱ.The Stress-Strain Relationship under Biaxial Loading / 第三军医大学学报

For the first pt.see ibid vol.11 no.4,p.241 (1989).The anterior interven-tricular branch aad the circumflex branch of the left coronary artery,and the right coronary were excised from 7 autopsy adult subjects without heart diseases.A biaxial loading test for the vascular specimens was completed,which was simultaneously finished in the internal thoracic artery(ITA) and the great saphenous vein (GSV) of the same subjects in order to compare with the coronary arteries.Stress-strain relationships of the vessels were expressed by the exponential strain energy function.The meaning of the two-dimensional material constants for the vessels are discussed.

Biomechanical Properties of Coronary Arteries in Human.Ⅲ.Static Elastic Moduli,Microstructure and Clinical Significance / 第三军医大学学报

For the 1st and 2nd pts.see ibid vol.11,no.4t p.241 & p.251 (1989).The anterior interventricular branch and the circumflex branch of the left coronary artery and the right coronary artery were excised from 7 autopsy adult subjects without heart diseases.A biaxial loading test lor the vascular specimens was completed,which was simultaneously finished in the internal thoracic artery (ITA) and the great saphenous vein (GSV) of the same subjects in order to compare with the coronary arteries.Elastic moduli of the vessels increased with increasing pressure in the vessels.As compared with GSV the mechanical properties of ITA ap-proach the coronary arteries.It is assumed that the coronary artery bypass grafting choose ITA before GSV in view of the mechanical properties of the vascular walls.A ratio of collagen per elastin may be used as an index of the arterial elasticity.It is discussed that the biomechanical properties of the arteries may influence the pathogenesis of the arteriosclerosis.

Quantitative Analysis of Microstructural Components in Human Coronary Arteries / 第三军医大学学报

0.05). ITA contains elastin a relatively higher than the other two (P