Different biomechanical properties of medial and adventitial layers of thoracic aorta in Wistar-Kyoto and spontaneously hypertensive rats

Uniaxial Tensile Properties of Atherosclerotic Carotid Artery After Mobilization of Pushing on Qiao-Gong: A Safety Study Using an Animal Model of Carotid Atherosclerosis

OBJECTIVES

This study aimed to preliminarily explore the effects of the soft tissue mobilization of pushing on Qiao-Gong (MPQ) on biomechanical properties of the carotid artery using an animal model of carotid atherosclerosis (CAS).

METHODS

Fifty rabbits were randomly divided into 4 groups: animals with CAS treated with MPQ (CAS-MPQ [n = 15]); animals with CAS treated without MPQ (CAS [n = 15]); normal animals treated with MPQ (normal-MPQ [n = 10]); and a blank control group (n = 10). The MPQ procedure consisted of soft tissue mobilization of the Qiao-Gong acupoint on the front edge of the sternocleidomastoid muscle applied from top to bottom, by flat pushing with the thumb repeatedly for 20 times. Disease in the CAS models was induced by carotid artery balloon injury combined with a high-fat diet for 12 weeks. At the end of modeling, carotid color Doppler ultrasonography examination was performed to confirm which animal models were successfully induced with CAS, excluding model rabbits without typical CAS at the same time. Then, MPQ was applied on rabbits in the CAS-MPQ and the normal-MPQ groups for 3 weeks. By contrast, rabbits in the other 2 groups were fed normally without MPQ. Uniaxial failure tests were later performed on carotid arteries in all 4 groups, and at the end of the study, a 2-way factorial analysis of variance of the results was conducted.

RESULTS

(1) At the end of modeling, 10 rabbits in the CAS-MPQ group and 9 in the CAS group were included with typical carotid atherosclerotic characteristics. (2) Young's elastic modulus of the rabbit carotid artery increased more significantly in the CAS-MPQ group than the CAS group. (3) Compared with normal rabbit carotid arteries, atherosclerotic carotid arteries had lower levels of ultimate stress and ultimate strain but higher levels of ultimate load.

CONCLUSIONS

The uniaxial tensile mechanical properties of the rabbit atherosclerotic carotid artery were impaired after MPQ.

Comparative in vivo analysis of the role of the adventitia and the endothelium on arterial mechanical function: relevance for aortic counterpulsation

PURPOSE

The comparative effect of the intimal and adventitial layers on arterial biomechanics control, in basal and altered conditions, remains to be elucidated. This study aimed (1) to characterize the arterial conduit (CF) and buffering (distensibility) function of the iliac arteries in in vivo animals, in which the intimal and adventitial layers were removed; (2) to determine the effects of intra-aortic ballon pumping (IABP) on simultaneously de-adventitialized (DA) and de-endothelialized (DE) iliac arteries before and after induced heart failure.

METHODS

Pressure and diameter signals were measured in the iliac arteries of sheep (n = 7) in which the adventitial and intima layer were removed. Intra-aortic balloon pump (IABP) assistance was used in a control state and after heart failure induction.

RESULTS

Both DE and DA determined significant changes in arterial diameter, distensibility and CF. Changes were higher after DA than after DE in terms of distensibility and CF (p<0.05). DA followed by DE (DA + DE) showed significant increases in arterial diameter and CF, accompanied by a decrease in distensibility (p<0.05) with respect to intact arteries. Heart failure induction caused significant hemodynamic changes without modifying the already impaired local biomechanical parameters. Nonsignificant improvements in the biomechanical parameters of DA + DE iliac arteries were observed during IABP before and after heart failure induction.

CONCLUSIONS

Biomechanical changes caused by DA of iliac arteries were more important than those observed after DE. The DA + DE arteries showed significant differences with respect to intact arteries and with DA or DE arteries. IABP-related effects on arterial mechanics were absent in DA + DE arteries.

Cervical Rotatory Manipulation Decreases Uniaxial Tensile Properties of Rabbit Atherosclerotic Internal Carotid Artery

Objective. To investigate the effects of one of the Chinese massage therapies, cervical rotatory manipulation (CRM), on uniaxial tensile properties of rabbit atherosclerotic internal carotid artery (ICA). Methods. 40 male purebred New Zealand white rabbits were randomly divided into CRM-Model group, Non-CRM-Model group, CRM-Normal group, and Non-CRM-Normal group. After modeling (atherosclerotic model) and intervention (CRM or Non-CRM), uniaxial tensile tests were performed on the ICAs to assess the differences in tensile mechanical properties between the four groups. Results. Both CRM and modeling were the main effects affecting physiological elastic modulus (PEM) of ICA. PEM in CRM-Model group was 1.81 times as much as Non-CRM-Model group, while the value in CRM-Model group was 1.34 times as much as CRM-Normal group. Maximum elastic modulus in CRM-Model group was 1.80 times as much as CRM-Normal group. Max strains in CRM-Model group and Non-CRM-Model group were 30.98% and 28.71% lower than CRM-Normal group and Non-CRM-Normal group, respectively. However, whether treated with CRM or not, the uniaxial tensile properties of healthy ICAs were not statistically different. Conclusion. CRM may decrease the uniaxial tensile properties of rabbit arteriosclerotic ICA, but with no effect on normal group. The study will aid in the meaningful explanation of the controversy about the harmfulness of CRM and the suitable population of CRM.

Opposing changes in thoracic and abdominal aortic biomechanical properties in rodent models of vascular calcification and hypertension

This study investigated the effects of hypertension on regional aortic biomechanical and structural properties in three rat models of vascular calcification: the hypertensive Lewis polycystic kidney (LPK; n = 13) model of chronic kidney disease, spontaneously hypertensive rats (SHRs; n = 12), and calcification in normotensive Lewis rats induced by vitamin D3 and nicotine (VDN; n = 8). Lewis and Wistar-Kyoto rats were controls. Thoracic and abdominal aortic stiffness parameters were assessed by tensile testing. In models where aortic stiffness differences compared with controls existed in both thoracic and abdominal segments, an additional cohort was quantified by histology for thoracic and abdominal aortic elastin, collagen, and calcification. LPK and VDN animals had higher thoracic breaking strain than control animals ( P < 0.01 and P < 0.05, respectively) and lower energy absorption within the tensile curve of the abdominal aorta ( P < 0.05). SHRs had a lower abdominal breaking stress than Wistar-Kyoto rats. LPK and VDN rats had more elastic lamellae fractures than control rats ( P < 0.001), which were associated with calcium deposition (thoracic R = 0.37, P = 0.048; abdominal: R = 0.40, P = 0.046). LPK rats had higher nuclear density than control rats ( P < 0.01), which was also evident in the thoracic but not abdominal aorta of VDN rats ( P < 0.01). In LPK and VDN rats, but not in control rats, media thickness and cross-sectional area were at least 1.5-fold greater in thoracic than abdominal regions. The calcification models chronic kidney disease and induced calcification in normotension caused differences in regional aortic stiffness not seen in a genetic form of hypertension. Detrimental abdominal aortic remodeling but lower stiffness in the thoracic aorta with disease indicates possible compensatory mechanisms in the proximal aorta.

Eicosapentaenoic acid/docosahexaenoic acid 1:1 ratio improves histological alterations in obese rats with metabolic syndrome

Background

Marine polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with improvement in the Metabolic Syndrome (MS). The aim of this study is to evaluate how three fish-oil diets with different eicosapentaenoic acid/docosahexaenoic acid ratios (EPA/DHA ratio) affect the histology of liver, kidney, adipose tissue and aorta in a preliminary morphological study. This work uses an animal model of metabolic syndrome in comparison with healthy animals in order to provide information about the best EPA:DHA ratio to prevent or to improve metabolic syndrome symptoms.

Methods

35 Wistar rats, as a control, and 35 spontaneously hypertensive obese rats (SHROB) were fed for 13 weeks with 3 different suplemmentation of fish oil containing EPA and DHA ratios (1:1, 2:1 and 1:2, respectively). All samples were stained with haematoxylin/eosin stain, except aorta samples, which were stained also with Verhoeff and van Gieson’s stain. A histological study was carried out to evaluate changes. These changes were statistically analyzed using SPSS IBM 19 software. The quantitative data were expressed by mean ± SD and were compared among groups and treatments using ANOVA with post-hoc tests for parametric data and the U-Mann–Whitney for non-parametric data. Qualitative data were expressed in frequencies, and compared with contingency tables using χ² statistics.

Results

EPA:DHA 1:1 treatment tended to improve the density and the wrinkling of elastic layers in SHROB rats. Only Wistar rats fed with EPA:DHA 1:1 treatment did not show mast cells in adipose tissue and has less kidney atrophy. In both strains EPA:DHA 1:1 treatment improved inflammation related parameters in liver and kidney.

Conclusions

EPA:DHA 1:1 treatment was the most beneficial treatment since improved many histological parameters in both groups of rats.

Remodeling of elastic layer of aortic artery after training by swimming in spontaneously hypertensive rats

Hypertension is a major risk factor for cardiovascular diseases, in which the elastic properties of arteries are subjected to high pressure levels, and networks of elastic fibers may develop cleft longitudinal, transverse, breaks and fragmentation, and such structural changes (fibrosis and degradation of elastin) may lead to a decrease in the elasticity of the artery. The descending thoracic aortas of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs) subjected to physical training through swimming or those of sedentary rats were prepared with hematoxylin-eosin and Verhoff to assess the artery medial. The images were captured with a videocamera coupled to an ordinary light microscope and the images were analyzed with the same program. SHRs showed a larger area of the medial layer of the thoracic aorta (F = 25,764, P < 0.001), and it was observed that rats submitted to physical training through swimming showed a larger area of the thoracic aorta (t = 3.206, P = 0.011). There was a higher percentage of elastic trained (F = 6.536, P = 0.019). To conclude, this study aimed to determine the elastic component of the aortic artery in animals that underwent exercise when compared with those that did not perform the activity, and analyze the relationship between the area of the aortic wall in trained and sedentary animals. The principal conclusion is that the rigidity of the aorta is not increased in SHRs subjected to physical training compared with that of trained WKY animals; however, when sedentary SHRs were analyzed there was a decrease in the elasticcomponent, which can characterize the aortic arterial stiffness in SHRs.