Renoprotective Mechanism of Remote Ischemic Preconditioning Based on Transcriptomic Analysis in a Porcine Renal Ischemia Reperfusion Injury Model

Ischemic preconditioning (IPC) is a well-known phenomenon in which tissues are exposed to a brief period of ischemia prior to a longer ischemic event. This technique produces tissue tolerance to ischemia reperfusion injury (IRI). Currently, IPC’s mechanism of action is poorly understood. Using a porcine single kidney model, we performed remote IPC with renal IRI and evaluated the IPC mechanism of action. Following left nephrectomy, 15 female Yorkshire pigs were divided into three groups: no IPC and 90 minutes of warm ischemia (control), remote IPC immediately followed by 90 minutes of warm ischemia (rIPCe), and remote IPC with 90 minutes of warm ischemia performed 24 hours later (rIPCl). Differential gene expression analysis was performed using a porcine-specific microarray. The microarray analysis of porcine renal tissues identified 1,053 differentially expressed probes in preconditioned pigs. Among these, 179 genes had altered expression in both the rIPCe and rIPCl groups. The genes were largely related to oxidation reduction, apoptosis, and inflammatory response. In the rIPCl group, an additional 848 genes had altered expression levels. These genes were primarily related to immune response and inflammation, including those coding for cytokines and cytokine receptors and those that play roles in the complement system and coagulation cascade. In the complement system, the membrane attack complex was determined to be sublytic, because it colocalized with phosphorylated extracellular signal-regulated kinase. Furthermore, alpha 2 macroglobulin, tissue plasminogen activator, uterine plasmin trypsin inhibitor, and arginase-1 mRNA levels were elevated in the rIPCl group. These findings indicate that remote IPC produces renoprotective effects through multiple mechanisms, and these effects develop over a long timeframe rather than immediately following IPC.     

MicroRNA and mRNA Signatures in Ischemia Reperfusion Injury in Heart Transplantation

Ischemia reperfusion (I/R) injury is an unavoidable event occurring during heart transplantation, leading to graft failures and lower long-term survival rate of the recipient. Several studies have demonstrated that microRNAs (miRNAs) are vital regulators of signalling pathways involved in I/R injury. The present study aims to quantify the altered expression levels of miRNA and mRNA upon I/R injury in a mouse heart transplantation model, and to investigate whether these miRNA can regulate genes involved in I/R injury. We performed heterotopic heart transplantation on mouse models to generate heart tissue samples with I/R and non-I/R (control). The expression levels of miRNAs as well as genes were measured in heart grafts by microarray and real time RT-PCR. miRNA alteration in cardiomyocytes exposed to hypoxia was also detected by qRT-PCR. We observed significant alterations in miRNA and gene expression profile after I/R injury. There were 39 miRNAs significantly downregulated and 20 upregulated up to 1.5 fold in heart grafts with I/R injury compared with the grafts without I/R. 48 genes were observed with 3 fold change and p<0.05 and 18 signalling pathways were enriched using Keggs pathway library. Additionally, hypoxia/reperfusion induced primary cardiomyocyte apoptosis and altered miRNA expression profiles. In conclusion, this is the first report on miRNA expression profile for heart transplantation associated with I/R injury. These findings provide us with an insight into the role of miRNA in I/R injury in heart transplantation.     

Homer1a基因敲除对小鼠局灶性脑缺血再灌注损伤的作用

目的:通过研究homer1a基因敲除小鼠脑缺血再灌注损伤及海马区星形胶质细胞活化、数目形态变化,探讨homer1a基因在脑缺血损伤中的作用及机制。方法:取雄性homer1a基因敲除(Knock Out,KO)小鼠及同窝野生型(Wild Type,WT)小鼠各15只,分为基因敲除假手术组(Sham Knock Out,SKO,n=3)、基因敲除型缺血2 h再灌注24 h组(Model Knock Out,MKO,n=12)、野生型假手术组(Sham Wild Type,SWT,n=3)及野生型缺血2 h再灌24h组(Model Wild Type,MWT,n=12)。线栓法闭塞小鼠大脑中动脉制作脑缺血再灌注损伤模型(middle cerebral artery occlusion and reperfusion,MCAO/R),在缺血再灌注损伤前(0 h)及缺血再灌注后3 h、6 h、12 h、24 h后进行改良版神经损伤严重性评分(modified Neurological severity scores,m NSS)、2,3,5—氯化三苯基四氮唑(2,3,5triphenyltetrazolium chloride,TTC)染色、苏木素—伊红染色(Hematoxylin-eosin staining,HE)、原位末端转移酶标记技术(terminal deoxynucleotidyl transferase(Td T)-mediated deoxyuridine triphosphate(d UTP)nick end labeling,TUNEL)检测及免疫荧光染色观察海马区星形胶质细胞神经纤维酸性蛋白(Glial Fibrillary Acidic Protein,GFAP)改变。结果:SKO组、SWT组行为学m NSS评分均为0分,TTC染色未见梗死灶。TUNLE及GFAP染色阳性细胞数很少且未见统计学差异(P0.05)。脑缺血再灌注24 h后,MKO组m NSS评分较MWT组高;TTC染色MKO组较MWT组梗死百分比高;MKO组较MWT组TUNEL凋亡率高;GFAP免疫荧光染色阳性数MKO组少于MWT组,且均有统计学差异(P0.05)。结论:homer1a基因敲除加重了小鼠脑缺血再灌注损伤,星形胶质细胞可能参与并发挥复杂作用。     

A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ischemia and reperfusion. Immune response includes cytokine expression and release or secretion of endogenous ligands of innate immune receptors. Activation of innate immunity can potentially modulate infarct size. We have modified an existing murine closed-chest model using hanging weights which could be useful for studying myocardial pre- and postconditioning and the role of innate immunity in myocardial ischemia and reperfusion. This model allows animals to recover from surgical trauma before onset of myocardial ischemia.Volatile anesthetics have been intensely studied and their preconditioning effect for the ischemic heart is well known. However, this protective effect precludes its use in open chest models of coronary artery ligation. Thus, another advantage could be the use of the well controllable volatile anesthetics for instrumentation in a chronic closed-chest model, since their preconditioning effect lasts up to 72 hours. Chronic heart diseases with intermittent ischemia and multiple hit models are other possible applications of this model.For the chronic closed-chest model, intubated and ventilated mice undergo a lateral blunt thoracotomy via the 4th intercostal space. Following identification of the left anterior descending a ligature is passed underneath the vessel and both suture ends are threaded through an occluder. Then, both suture ends are passed through the chest wall, knotted to form a loop and left in the subcutaneous tissue. After chest closure and recovery for 5 days, mice are anesthetized again, chest skin is reopened and hanging weights are hooked up to the loop under ECG control.At the end of the ischemia/reperfusion protocol, hearts can be stained with TTC for infarct size assessment or undergo perfusion fixation to allow morphometric studies in addition to histology and immunohistochemistry.     

缺血性肠炎中肠神经肽的实验研究

目的：探讨肠神经系统中肠神经肽在应激状态下缺血性肠炎性反应中的变化。方法：取成年新西兰大白兔40只,随机分为对照组和实验组,各20只。采用夹闭肠系膜上动脉1小时后松夹恢复肠系膜上动脉血流制成肠缺血后再灌流模型,应用免疫组织化学的方法检测结肠壁肠神经组织中ENK（脑啡肽）、NT（神经降压素）、VIP（血管活性肠肽）、NPY（神经肽Y）的表达情况。结果：实验组ENK、NT的表达明显高于对照组（t=-5．542、3．404P〈0．01）,而实验组VIP、NPY的表达与对照组无明显差异（P〉0．05）。结论：在应激状态下缺血性肠炎中,肠神经组织ENK、NT的表达明显升高,而VIP、NPY的表达无明显变化。而ENK、NT为兴奋性神经递质,V1P、NPY为抑制性神经递质,所以在缺血性肠炎性反应中,肠神经系统以兴奋性作用为主。     

大鼠急性肾缺血再灌注损伤模型的建立与评估

目的：对现有的经腹部切口建立急性肾缺血再灌注损伤动物模型进行改良,探索建立急性肾缺血再灌注损伤模型的新方法。方法：实验组大鼠16例,经背部切口进入腹膜后间隙,游离钳夹双侧肾动脉45min后开放血流,建立急性肾缺血再灌注损伤模型;伪手术组8例,不夹闭肾动脉,余步骤与实验组相同;对照组8例无处理。术后通过建模成功率、组织病理检查、血肌酐和血尿素氮及氧化应激水平对模型进行评估。结果：实验组15只成功建立急性肾缺血再灌注损伤模型。术后1天病理检查显示实验组肾组织出现广泛损伤,术后实验组’肾小管坏死评分、肾MDA水平、血肌酐及血尿素氮值明显高于对照组（P〈0．05）。结论：经背部切口钳夹双侧肾动脉可建立稳定的大鼠急性肾缺血再灌注损伤模型。该造模方法简便易行,成功率高,且具备手术切口小、手术时间短及并发症少的优点,建立的模型适合于急性肾损伤的研究。     

大鼠急性肾缺血再灌注损伤模型的建立与评估

目的:对现有的经腹部切口建立急性肾缺血再灌注损伤动物模型进行改良,探索建立急性肾缺血再灌注损伤模型的新方法。方法:实验组大鼠16例,经背部切口进入腹膜后间隙,游离钳夹双侧肾动脉45min后开放血流,建立急性肾缺血再灌注损伤模型;伪手术组8例,不夹闭肾动脉,余步骤与实验组相同;对照组8例无处理。术后通过建模成功率、组织病理检查、血肌酐和血尿素氮及氧化应激水平对模型进行评估。结果:实验组15只成功建立急性肾缺血再灌注损伤模型。术后1天病理检查显示实验组肾组织出现广泛损伤,术后实验组肾小管坏死评分、肾MDA水平、血肌酐及血尿素氮值明显高于对照组(P<0.05)。结论:经背部切口钳夹双侧肾动脉可建立稳定的大鼠急性肾缺血再灌注损伤模型。该造模方法简便易行,成功率高,且具备手术切口小、手术时间短及并发症少的优点,建立的模型适合于急性肾损伤的研究。     

Catestatin Improves Post-Ischemic Left Ventricular Function and Decreases Ischemia/Reperfusion Injury in Heart

The Chromogranin A (CgA)-derived anti-hypertensive peptide catestatin (CST) antagonizes catecholamine secretion, and is a negative myocardial inotrope acting via a nitric oxide-dependent mechanism. It is not known whether CST contributes to ischemia/reperfusion injury or is a component of a cardioprotective response to limit injury. Here, we tested whether CST by virtue of its negative inotropic activity improves post-ischemic cardiac function and cardiomyocyte survival. Three groups of isolated perfused hearts from adult Wistar rats underwent 30-min ischemia and 120-min reperfusion (I/R, Group 1), or were post-conditioned by brief ischemic episodes (PostC, 5-cycles of 10-s I/R at the beginning of 120-min reperfusion, Group 2), or with exogenous CST (75 nM for 20 min, CST-Post, Group-3) at the onset of reperfusion. Perfusion pressure and left ventricular pressure (LVP) were monitored. Infarct size was evaluated with nitroblue-tetrazolium staining. The CST (5 nM) effects were also tested in simulated ischemia/reperfusion experiments on cardiomyocytes isolated from young-adult rats, evaluating cell survival with propidium iodide labeling. Infarct size was 61 ± 6% of risk area in hearts subjected to I/R only. PostC reduced infarct size to 34 ± 5%. Infarct size in CST-Post was 36 ± 3% of risk area (P < 0.05 respect to I/R). CST-Post reduced post-ischemic rise of diastolic LVP, an index of contracture, and significantly improved post-ischemic recovery of developed LVP. In isolated cardiomyocytes, CST increased the cell viability rate by about 65% after simulated ischemia/reperfusion. These results suggest a novel cardioprotective role for CST, which appears mainly due to a direct reduction of post-ischemic myocardial damages and dysfunction, rather than to an involvement of adrenergic terminals and/or endothelium.     

An Anoxia-starvation Model for Ischemia/Reperfusion in C. elegans

Protocols for anoxia/starvation in the genetic model organism C. elegans simulate ischemia/reperfusion. Worms are separated from bacterial food and placed under anoxia for 20 hr (simulated ischemia), and subsequently moved to a normal atmosphere with food (simulated reperfusion). This experimental paradigm results in increased death and neuronal damage, and techniques are presented to assess organism viability, alterations to the morphology of touch neuron processes, as well as touch sensitivity, which represents the behavioral output of neuronal function. Finally, a method for constructing hypoxic incubators using common kitchen storage containers is described. The addition of a mass flow control unit allows for alterations to be made to the gas mixture in the custom incubators, and a circulating water bath allows for both temperature control and makes it easy to identify leaks. This method provides a low cost alternative to commercially available units.     

后适应缺血时间窗的选择对小鼠心肌再灌注损伤的影响

目的 探讨后适应对小鼠心肌再灌注损伤的影响以及不同缺血时间窗的后适应心脏保护作用的差异 .方法 96只成年C57/BL小鼠随机分为缺血时间30、45 min和60 min的三组,每组又分为后适应和缺血再灌注两种处理.通过开胸结扎左冠状动脉造成急性心肌梗死 ,在完全再灌注早期给予反复短暂再通/闭塞的缺血后适应.采用Evans blue和TTC染色的方法确定缺血心肌和梗死心肌面积,并测定血清的心肌酶含量、心肌超氧化物歧化酶 (SOD) 活性与丙二醛 (MDA) 水平以及血流动力学指标.结果 缺血30 min后适应组、缺血45 min后适应组心肌梗死面积分别比相同缺血时间的再灌注对照组减少53.1%和31.2%,差异均具有统计学意义(P<0.01),缺血后适应可明显降低血清心肌酶、提高心肌SOD的活性以及改善血流动力学的恶化;缺血60 min后适应组梗死心肌面积无明显降低, 差异无统计学意义(P＞0.05).结论 小鼠心肌处于轻中度水平的缺血损伤,在恢复冠脉血流的早期施行缺血后适应可以有效地减少心肌再灌注损伤,但随着缺血时间的延长,心肌保护作用就明显减弱或消失.     

Glucocorticoid Modulates Angiotensin II Receptor Expression Patterns and Protects the Heart from Ischemia and Reperfusion Injury

Glucocorticoid regulates angiotensin II receptor (ATR) expression via activating glucocorticoid receptors and binding to glucocorticoid response elements. The regulation of ATR by glucocorticoids in the context of myocardial injury from ischemia/reperfusion (I/R) is yet to be elucidated. The present study determined the role of ATR in glucocorticoid-induced cardiac protection. Adult male rats were administered once a day i.p. 1 mg/kg/day dexamethasone or dexamethasone plus 10 mg/kg/day RU486 for 5 days. Hearts were then isolated and subjected to I/R injury in a Langendorff preparation. Dexamethasone treatment significantly decreased I/R injury and improved post-ischemic recovery of cardiac function. Dexamethasone increased glucocorticoid receptor binding to glucocorticoid response elements at AT_1aR and AT₂R promoters, resulting in a significant increase in expression of AT₁R protein but a decrease in AT₂R expression in the heart. In addition, dexamethasone treatment significantly increased PKCε expression and p-PKCε protein abundance. These dexamethasone-mediated effects were blocked by RU486. More importantly, blockade of AT₁R and AT₂R with losartan and PD123319 abrogated dexamethasone-induced protection of the heart from I/R injury. The results indicate that glucocorticoid promotes a cardioprotective phenotype associated with the upregulation of AT₁R and PKCε and downregulation of AT₂R in the heart.     

Local Delivery of Polarized Macrophages Improves Reperfusion Recovery in a Mouse Hind Limb Ischemia Model

Aims

Enhancement of collateral development in coronary or peripheral artery disease is a therapeutic target, but it has proven difficult to achieve. Macrophages are key players in collateral remodeling, yet the effect of different macrophage subsets on arteriogenesis has not been investigated.

Methods and Results

Murine macrophages were cultured from bone marrow and polarized into M1 (IFNγ), M2a (IL-4) or M2c (IL-10) subsets. C57BL/6 mice underwent femoral artery ligation followed by intramuscular injection of macrophage subsets. Using eGFP expressing macrophages, cells could be detected at least 6 days after ligation and were located in the perivascular space of collateral vessels. After 14 days, perfusion ratio was increased in animals treated with M1 as well as M2a and M2c macrophages compared to control. Depletion of circulating monocytes by clodronate liposome injections did not hamper reperfusion recovery, however, treatment with exogenous polarized macrophages improved perfusion ratio after 14 days again. We used IL10R^fl/fl/LysMCre⁺ mice to study the effect of inhibition of endogenous polarization towards specifically M2c macrophages on arteriogenesis. Deletion of the IL10-receptor (IL10R) in the myeloid lineage did not affect reperfusion recovery, yet the pro-arteriogenic effect of exogenously injected M2c macrophages was still present.

Conclusions

Local injection of polarized macrophages promotes reperfusion recovery after femoral artery ligation and is not influenced by depletion of circulatory monocytes. Preventing endogenous M2c polarization did not affect reperfusion recovery suggesting that M2c’s are not required for collateralization, but are sufficient to induce collateral formation upon exogenous administration. This is the first study using local injection of macrophage subsets showing the pro-arteriogenic effect of polarized macrophages.     

Ly6Clow and Not Ly6Chigh Macrophages Accumulate First in the Heart in a Model of Murine Pressure-Overload

Cardiac tissue remodeling in the course of chronic left ventricular hypertrophy requires phagocytes which degrade cellular debris, initiate and maintain tissue inflammation and reorganization. The dynamics of phagocytes in left ventricular hypertrophy have not been systematically studied. Here, we characterized the temporal accumulation of leukocytes in the cardiac immune response by flow cytometry and fluorescence microscopy at day 3, 6 and 21 following transverse aortic constriction (TAC). Cardiac hypertrophy due to chronic pressure overload causes cardiac immune response and inflammation represented by an increase of immune cells at all three time points among which neutrophils reached their maximum at day 3 and macrophages at day 6. The cardiac macrophage population consisted of both Ly6C^low and Ly6C^high macrophages. Ly6C^low macrophages were more abundant peaking at day 6 in response to pressure overload. During the development of cardiac hypertrophy the expression pattern of adhesion molecules was investigated by qRT-PCR and flow cytometry. CD11b, CX3CR1 and ICAM-1 determined by qRT-PCR in whole cardiac tissue were up-regulated in response to pressure overload at day 3 and 6. CD11b and CX3CR1 were significantly increased by TAC on the surface of Ly6C^low but not on Ly6C^high macrophages. Furthermore, ICAM-1 was up-regulated on cardiac endothelial cells. In fluorescence microscopy Ly6C^low macrophages could be observed attached to the intra- and extra-vascular vessel-wall. Taken together, TAC induced the expression of adhesion molecules, which may explain the accumulation of Ly6C^low macrophages in the cardiac tissue, where these cells might contribute to cardiac inflammation and remodeling in response to pressure overload.     

Penehyclidine Hydrochloride Preconditioning Provides Cardioprotection in a Rat Model of Myocardial Ischemia/Reperfusion Injury

To investigate the impacts and related mechanisms of penehyclidine hydrochloride (PHC) on ischemia/reperfusion (I/R)-induced myocardial injury. A rat model of myocardial I/R injury was established by the ligation of left anterior descending coronary artery for 30 min followed by 3 h perfusion. Before I/R, the rats were pretreated with or without PHC. Cardiac function was measured by echocardiography. The activities/levels of myocardial enzymes, oxidants and antioxidant enzymes were detected. Evans blue/TTC double staining was performed to assess infarct size. Cardiomyocyte apoptosis was evaluated by TUNEL assay. The release of inflammatory cytokines and inflammatory mediators was detected by ELISA. Western blot was performed to analyze the expression of COX-2, IκB, p-IκB and NF-κB. Meanwhile, the rats were given a single injection of H-PHC before I/R. The effects of PHC on myocardial infarct and cardiac function were investigated after 7 days post-reperfusion. We found that PHC remarkably improved cardiac function, alleviated myocardial injury by decreasing myocardial enzyme levels and attenuated oxidative stress in a dose-dependent manner. Additionally, PHC preconditioning significantly reduced infarct size and the apoptotic rate of cardiomyocytes. Administration of PHC significantly decreased serum TNF-α, IL-1β, IL-6 and PGE₂ levels and myocardium COX-2 level. Meanwhile, the expression levels of p-IκB and NF-κB were downregulated, while IκB expression was upregulated. H-PHC also exerted long-term cardioprotection in a rat model of I/R injury by decreasing infarct size and improving cardiac function. These results suggest that PHC can efficiently protect the rats against I/R-induced myocardial injury.     

Secreted Frizzled-related Protein 5 Diminishes Cardiac Inflammation and Protects the Heart from Ischemia/Reperfusion Injury

Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted frizzled-related protein 5 (Sfrp5) has been shown to function as an extracellular inhibitor of non-canonical Wnt signaling that is expressed at relatively high levels in white adipose tissue. The aim of this study was to investigate the role of Sfrp5 in the heart under ischemic stress. Sfrp5 KO and WT mice were subjected to ischemia/reperfusion (I/R). Although Sfrp5-KO mice exhibited no detectable phenotype when compared with WT control at baseline, they displayed larger infarct sizes, enhanced cardiac myocyte apoptosis, and diminished cardiac function following I/R. The ischemic lesions of Sfrp5-KO mice had greater infiltration of Wnt5a-positive macrophages and greater inflammatory cytokine and chemokine gene expression when compared with WT mice. In bone marrow-derived macrophages, Wnt5a promoted JNK activation and increased inflammatory gene expression, whereas treatment with Sfrp5 blocked these effects. These results indicate that Sfrp5 functions to antagonize inflammatory responses after I/R in the heart, possibly through a mechanism involving non-canonical Wnt5a/JNK signaling.     

Keratinocyte Growth Factor Improves Epithelial Structure and Function in a Mouse Model of Intestinal Ischemia/Reperfusion

Background

Intestinal ischemia/reperfusion (I/R) induces the desquamation of the intestinal epithelium, increases the intestinal permeability, and in patients often causes fatal conditions including sepsis and multiple organ failure. Keratinocyte growth factor (KGF) increases intestinal growth, although little is known about KGF activity on intestinal function after intestinal I/R. We hypothesized that KGF administration would improve the intestinal function in a mouse model of intestinal I/R.

Methods

Adult C57BL/6J mice were randomized to three groups: Sham, I/R group and I/R+KGF group. Mice were killed on day 5, and the small bowel was harvested for histology, wet weight, RNA and protein content analysis. Epithelial cell (EC) proliferation was detected by immunohistochemistry for PCNA, and apoptosis was determined by TUNEL staining. The expressions of Claudin-1 and ZO-1 were detected by immunohistochemistry. Epithelial barrier function was assessed with transepithelial resistance (TER).

Results

KGF significantly increased the intestinal wet weight, contents of intestinal protein and RNA, villus height, crypt depth and crypt cell proliferation, while KGF resulted in the decrease of epithelial apoptosis. KGF also stimulated the recovery of mucosal structures and attenuated the disrupted distribution of TJ proteins. Moreover, KGF attenuated the intestinal I/R-induced decrease in TER and maintained the intestinal barrier function.

Conclusion

KGF administration improves the epithelial structure and barrier function in a mouse model of intestinal I/R. This suggests that KGF may have clinical applicability.     

Progesterone Attenuates Aquaporin-4 Expression in an Astrocyte Model of Ischemia/Reperfusion

Previous studies have suggested that progesterone may be involved in neuroprotection by preventing brain edema. In this study, we assessed the effects of progesterone on aquaporin-4 (AQP4) expression in an ischemia/reperfusion model of cultured rat astrocytes, and further explored the possible role of the protein kinase C (PKC) pathway in this course. We evaluate primary culture astrocytes exposed to 4 h oxygen–glucose deprivation (OGD) followed by 24 h reperfusion (OGD4h/R24h) as a means of simulating cortex ischemia and reperfusion, and test the effect of progesterone on AQP4 expression in response to OGD4h/R24h. Besides, the cell viability was assessed by MTT reduction and lactate dehydrogenase release assay, accompanied by cell morphology survey. At a concentration of 1 and 2 μM, progesterone significantly attenuated AQP4 at the level of both protein and mRNA and ameliorated the cell viability of astrocytes from OGD/reperfusion injury. Moreover, this effect was blocked by the PKC inhibitor Ro31-8220, which was employed before the OGD. These results indicate that progesterone exerts the protective effects and attenuates AQP4 expression in an astrocyte model of ischemia/reperfusion depending on the PKC signal pathway.     

Delayed Contrast Enhancement Imaging of a Murine Model for Ischemia Reperfusion with Carbon Nanotube Micro-CT

We aim to demonstrate the application of free-breathing prospectively gated carbon nanotube (CNT) micro-CT by evaluating a myocardial infarction model with a delayed contrast enhancement technique. Evaluation of murine cardiac models using micro-CT imaging has historically been limited by extreme imaging requirements. Newly-developed CNT-based x-ray sources offer precise temporal resolution, allowing elimination of physiological motion through prospective gating. Using free-breathing, cardiac-gated CNT micro-CT, a myocardial infarction model can be studied non-invasively and with high resolution. Myocardial infarction was induced in eight male C57BL/6 mice aged 8–12 weeks. The ischemia reperfusion model was achieved by surgically occluding the LAD artery for 30 minutes followed by 24 hours of reperfusion. Tail vein catheters were placed for contrast administration. Iohexol 300mgI/mL was administered followed by images obtained in diastole. Iodinated lipid blood pool contrast agent was then administered, followed with images at systole and diastole. Respiratory and cardiac signals were monitored externally and used to gate the scans of free-breathing subjects. Seven control animals were scanned using the same imaging protocol. After imaging, the heart was harvested, cut into 1mm slices and stained with TTC. Post-processing analysis was performed using ITK-Snap and MATLAB. All animals demonstrated obvious delayed contrast enhancement in the left ventricular wall following the Iohexol injection. The blood pool contrast agent revealed significant changes in cardiac function quantified by 3-D volume ejection fractions. All subjects demonstrated areas of myocardial infarct in the LAD distribution on both TTC staining and micro-CT imaging. The CNT micro-CT system aids straightforward, free-breathing, prospectively-gated 3-D murine cardiac imaging. Delayed contrast enhancement allows identification of infarcted myocardium after a myocardial ischemic event. We demonstrate the ability to consistently identify areas of myocardial infarct in mice and provide functional cardiac information using a delayed contrast enhancement technique.     

Quercetin Protects Against Oxidative Stress Associated Damages in a Rat Model of Transient Focal Cerebral Ischemia and Reperfusion

Experimental studies have demonstrated that oxidative stress and apoptosis play an important role in cerebral ischemic pathogenesis and may represent a target for treatment. The purpose of this study was to determine whether the quercetin dihydrate (Q) protects against cerebral ischemia neuronal damage. Male Wistar rats were subjected to transient middle cerebral artery occlusion (MCAO) for 2?h and reperfused for 72?h. Quercetin (30?mg/kg, i.p) was administrated 30?min before the onset of ischemia and after the ischemia at interval of 0, 24, 48, and 72?h. The administration of Q showed marked reduction in infarct size, reduced the neurological deficits in terms of behaviors, suppressed neuronal loss and diminished the p53 expression in MCAO rats. Q was found to be successful in upregulating the antioxidant status and lowering the TBARS level. Conversely, the elevated activity of poly (ADP-ribose) polymerase (PARP), and activity of caspase-3 in MCAO group was attenuated significantly in Q treated group when compared with MCAO group. Our study reveals that Q, as a powerful antioxidant, could prevent free radicals associated oxidative damage and morphological changes in the MCAO rats. Thus, it may have a therapeutic value for the treatment of stroke.