الفهرس 
I NTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
the present study was planned to assess the possible protective effects of Stem cells treatment on ischemic/reperfused hearts in hypertensive rats.
This study was carried out on 49 Adult female rats, weighing 170 -270 grams at the start of the study and will be assigned randomly into 3 groups:
1- Control group (n=17):
This group of rats was subjected to oral daily administration of saline for 6 weeks, in addition to IV injection of stem cells buffer in rat tail vein on the third week .After scarification, rats were subjected to ischemia /reperfusion injury on their isolated hearts.
2- Hypertensive untreated group (Ht-u group) (n=16):
This group of rats was subjected to daily oral administration of Nitro-L-arginine methyl ester (L-NAME) drug at a dose of (50 mg/kg/d) for 6 weeks to induce hypertension. Then, on the third week they were injected with stem cells buffer at the rat tail. After sacrifice, rats were subjected to ischemia /reperfusion injury of their isolated hearts.3- Hypertensive Stem cells treated group (Ht-SCs treated group) (n=16):
This group of rats was subjected to daily oral administration of L-NAME at a dose of (50 mg/kg/d) for 6 weeks to induce hypertension. Then, on the third week single dose of bone marrow-derived mesenchymal stem cells (MSCs) was injected at rat tail vein. After sacrifice, rats were subjected to ischemia /reperfusion injury of their isolated hearts.
All rats were subjected to weekly measurement of their body weight and their blood pressure using rat tail cuff technique. At the end of the study, on the sacrifice day, rats were anesthetized using thiopental Na after 12 hour overnight fast. ECG was recorded, blood samples were collected and centrifuged for determination of; plasma nitrites, malondialdehyde (MDA) and super oxide dismutase (SOD)levels and for the assessment of lipid profile by measuring plasma level of triglyceride (TG), total cholesterol (TC), low density lipoproteins (LDL) and high density lipoproteins (HDL).
Then in vitro study of isolated hearts perfused in langendorff preparation was performed to record the intrinsic activity of the heart under baseline condition and the responses of the heart during 5, 15 and 30 minutes of reperfusion following 30 minutes of total ischemia. Cardiac tissues were weighed then stored at -80°C for further measurement of MDA level and SOD enzymatic activity. Then heart, aorta and liver tissues were examined histopathologically. Fluorescence imaging of labeled MSCs in the heart, aorta and liver was performed.
Results of the present study revealed that body weight gain % was significantly increased in Ht-SCs treated rats compared to both control and hypertensive un-treated rats which may be due to multiple growth factors secreted by the stem cells or stem cells-derived exosomes.
In HT-u group, the 6th weeks systolic, diastolic and mean arterial blood pressure values were significantly increased compared to their initial and 3rd week values and compared to the control group owing to No deficiency. No deficiency was induced by L-NAME drug and might lead to vasoconstrictor effect together with activation of renin angiotensin system and ROS generation augmenting its own deficiency. MAP 6th week value showed significant negative correlation with plasma nitrites and significant positive correlations with plasma MDA, elucidating the role of oxidative stress in endothelial dysfunction and hypertension pathogenesis. Endothelial dysfunction was reflected by the Aortic wall thinning and intimal injury. Dyslipidemia detected in Ht-u rats and oxidized LDL might augment endothelial dysfunction.
Non- significant differences between initial and final DBP levels was detected in the Ht-SCs treated rats, which could be attributed to BM-MSCs paracrine secretion of anti-oxidant, anti-inflammatory and vasodilator factors as nitric oxide together with renin angiotensin system suppression. BM-MSCs homing to the aortic endothelial cells evidenced by fluorescent dye may mitigate endothelial dysfunction and lower arterial blood pressure.
In Ht-u rats PR interval significant prolongation denotes ischemia or AV node damage and dysfunction. It may ensue owing to the decrease in connexin- expression in chronic afterload. The significant increase in R voltage and left ventricular weight reflected left ventricular hypertrophy, which could be related to pressure overload, angiotensin II-mediated oxidative stress and calcium overload. Treatment with stem cells ameliorated left ventricular hypertrophy evidenced by the significant decrease in R voltage compared to the hypertensive rats that could be ascribed to the anti-hypertrophy and the anti-remodelling effects of the BMSC.
Ischemia reperfusion injury decreased all recorded values of the isolated heart study in all groups mediated by ATP depletion, oxidative stress, mitochondrial dysfunction and calcium overload.
In Ht-u rats, basal heart rate and all its reperfusion times values were significantly decreased compared to control rats due to nitric oxide deficiency, sinus node dysfunction and damage or down regulated Cx 43. Also, in Ht-u rats, systolic and diastolic dysfunction was evidenced by the significant decrease of basal PT/LVW together with the significant prolongation of both basal TPT and HRT.
Both TPT and HRT reperfusion values were significantly prolonged compared to the control rats denoting that hypertension aggravated the effects of ischemia reperfusion injury. This could be linked to augmented oxidative state that oxidize the sarcomeric proteins, break DNA strands. Dyslipidemia and oxidized LDL could activate inflammatory and apoptotic pathways leading to contractile dysfunction. Ryanodine receptors and SERCA oxidation might predispose to elevated diastolic calcium and diastolic dysfunction. Ventricular hypertrophy, activated renin-angiotensin system and nitric oxide deficiency lead to ventricular stiffness and impair diastolic relaxation. Basal and reperfusion MFR/LVW values showed a significant decrease from control rats which could be attributed to nitric oxide deficiency, endothelial dysfunction and microvascular plug by neutrophils and platelets.
In Ht- SCs trated rats, significant increase in heart rate basal and all reperfusion times values was demonstrated compared to Ht-u rats depending on the ability of mesenchymal stem cells to repair the damage of the cardiac pacemaker cells. Also, basal PT/LVW was non-significantly increased, while basal TPT and HRT were significantly shortened compared to HT-u group, being non-significantly changed from the control. TPT and HRT prolongation after IR injury was significantly lower in Ht-SCs treated rats than Ht-u