异种移植免疫排斥的研究进展

异种移植是解决人体器官严重短缺的重要思路.随着对异种移植排斥和人畜共患感染性疾病的深入研究,以及α-1,3-半乳糖苷转移酶基因敲除猪的成功构建,以猪为供体的异种移植与临床应用之间的距离正在逐渐缩短.阻碍异种移植发展的主要障碍仍是免疫排斥反应.本文试就目前异种免疫排斥的研究进展进行综述,希望对未来的临床异种移植研究提供参...     

异种肝移植的历史与发展

异种移植是解决同种供体器官短缺的重要途径。以α-1,3-半乳糖基转移酶基因敲除(GTKO)小型猪为供体、非人灵长类动物为受体的心脏和肾移植,最长存活达945 d和136 d,但肝移植尚无长期存活报道。国内外研究表明,免疫排斥和凝血调节障碍仍是阻碍移植肝和受体长期存活的主要原因。本文总结异种肝移植的发展历程,分析目前存在的问题,为未来的临床异种移植研究提供参考。     

异种移植临床试验的有关问题

异种移植的发展有望缓解供体器官短缺的状况。目前, 基因编辑猪被认为是临床异种移植的理想供体器官来源。在相关技术的推动下, 异种移植临床前研究取得了实质性成果, 这为开启早期临床试验创造了良好条件。特别是近两年, 国外该领域的临床研究取得了突破性进展。本文简要概述了国内外异种移植的临床应用进展, 从供体猪基因编辑、受试者全程管理原则、伦理和社会心理学三方面讨论异种移植临床试验的关键问题。相信在多学科交叉融合的背景下, 未来异种移植将逐步转入临床应用, 更好地造福人类。     

异种器官移植研究的主要问题与对策

器官移植是目前治疗器官功能衰竭的主要手段,但供者器官严重短缺使大部分患者不能及时接受治疗.据美国器官资源共享网络报道,近13年来约有30 000例肝病患者因缺乏合适的供肝而死亡.在美国,患者等待肝移植的平均时间为6d,但部分病情较重的患者必需在24～36 h内接受肝移植治疗,否则将失去手术机会.因此,开展异种器官移植研究,以动物器官桥接或替代人类器官进行移植,对解决供者短缺具有重大意义.尽管非人灵长类动物在系统发育方面比别的物种都更接近于人类,但它们并不适合成为临床异种移植的器官来源,主要原因有伦理学问题、种间交叉感染的风险、繁殖困难及器官体积不匹配等.目前大部分研究者都认为,猪比非人灵长类动物更适于成为临床异种移植的供者.猪具有器官体积和生理指标与人类接近、繁殖速度快、适于进行基因改造和修饰等优势[1].当前,以转基因猪为标志的异种移植研究已取得重要突破,使异种移植向临床应用迈出了重要的一步,但移植排斥反应、生理屏障和安全问题等仍限制着异种移植发展.本文就目前阻碍异种移植进入临床应用的主要问题和可能的解决方法作一综述,希望对未来的临床异种移植研究提供参考.     

异种移植临床前研究进展

猪是人体异种器官移植的理想供体,但由于种属差异,猪-人异种移植面临着巨大的免疫学障碍及动物病原体跨种传播的危险,使之难以应用于临床。但随着移植免疫学、基因工程学以及转基因技术的迅速发展,异种移植领域的研究也取得了显著进展,本文就近年来猪-非人灵长类动物异种移植的研究进展做一综述。     

异种移植临床前研究进展

猪是人体异种器官移植的理想供体，但由于种属差异，猪一人异种移植面临着巨大的免疫学障碍及动物病原体跨种传播的危险，使之难以应用于临床。但随着移植免疫学、基因工程学以及转基因技术的迅速发展，异种移植领域的研究也取得了显著进展，本文就近年来猪一非人灵长类动物异种移植的研究进展做一综述。     

异种移植中的排斥反应及其对策研究进展

随着器官移植技术在临床的广泛应用 ,同种异基因器官供体远不能满足受体的需要 ,异种移植有可能解决这一矛盾。非灵长类动物 ,特别是猪 ,因其易于饲养 ,且器官大小及免疫学、生理学特性与人类有一定的相似性 ,作为最适的异种移植器官供体已日益引起人们的关注[1,2 ] 。但由于人类和猪两种源间存在巨大的抗原差异 ,针对异种移植物的免疫应答比对同种移植物更加强烈。本文现对近年来有关异种移植排斥机制及其防治策略作一简要回顾。一、异种移植排斥机制1.超急性排斥反应 (hyperacuterejection,HAR):HAR以血栓形成、出血及异种移植物破坏为…     

异种胰岛移植

胰岛移植可以使糖尿病患者血糖稳定并能预防严重并发症,由于人类同种胰岛移植存在着供体不足,大量糖尿病患者因此得不到及时治疗。在实验研究基础上,国内外均进行了异种胰岛移植的临床研究,证实了胰岛移植在血糖控制及延缓并发症的发生发展是有效的,但是异种移植的排斥、长期应用免疫抑制剂的安全性、仍是干扰此项研究的障碍。尽管异种移植面临众多困难,但对供体器官和组织的极大需求促使克服种间移植的组织特异性不断取得进展。     

异种移植的细胞免疫排斥反应

现代外科技术和免疫抑制治疗的发展,使同种器官移植受体的存活时间越来越长,而供体短缺成为阻碍同种移植发展的首要难题。开展异种移植研究,用来源广泛且功能完备的动物器官代替人体器官进行移植治疗,是解决供体短缺的有效方法[1]。猪的繁殖速度快,各项生理指标与人类近似,且伦理学争论较小,因而目前大多数研究者倾向将小型猪作为异种器官移植研究的供体[2]。然而,以猪作为供体的异种移植术后存在免疫排斥反应、生理     

基因修饰猪在异种器官移植中的研究进展

器官移植是治疗终末期器官衰竭的最有效手段,但供器官严重匮乏已成为器官移植发展的最大障碍,异种器官移植为解决这一问题开辟了新思路。猪在遗传学、解剖学及生理特性等方面与人具有较大的相似性,因此被认为是异种器官移植最理想的供体来源。随着基因编辑技术的发展,基因修饰猪在异种器官移植领域中的研究与应用已取得较大进展。本文就基因修饰猪在猪-灵长类动物异种器官移植中的研究与应用进行综述。     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

A comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.