Thrombomodulin activity on human saphenous vein grafts prepared for coronary artery bypass.

Thrombomodulin, a membrane glycoprotein present on normal vascular endothelium, binds circulating thrombin and is important in protein C activation. These functions contribute to the nonthrombogenic nature of endothelium. Damage during harvest and ex vivo storage of vein grafts may result in dysfunction of this endothelial anticoagulant barrier and possibly contribute to early graft thrombosis. We studied the functional activity and antigenic expression of thrombomodulin on saphenous veins before (initial) and after (harvested) harvest and storage for coronary artery bypass grafting in 15 patients. Also, fresh saphenous vein was studied after mechanical endothelial stripping. After storage for 2.7 +/- 0.6 hours at room temperature in heparinized saline, thrombomodulin functional activity in harvested vein segments was 28% less than initial segments (p = 0.08). Endothelial stripping resulted in a 79% reduction in thrombomodulin activity compared with initial segments (p = 0.04). Immunohistochemical staining confirmed thrombomodulin antigen on vein grafts after harvest and storage, but not on segments stripped of endothelium. Thrombomodulin functional activity and antigenic expression on human saphenous vein grafts is not significantly changed by harvest and relatively short periods of storage at room temperature in heparinized saline.     

RNA干扰沉默蛋白激酶B基因表达对移植静脉内膜增生的影响

摘要：目的:观察纳米粒子包载的靶向蛋白激酶B(PKB)基因的shRNA表达载体局部转染对大鼠移植静脉内膜增生的影响。方法:应用聚乳酸聚乙醇酸共聚物(PLGA)和聚乙烯醇(PVA)包载PKB的RNA干扰基因载体，制备纳米级粒子混合物。建立自体颈静脉-颈总动脉移植模型共72只，随机分成转基因组、空载体组和对照组。分别于术后3，7，14，28 d取材；常规HE及Verhoeff 染色,用Northern blot和Western blot检测PKB基因的mRNA及蛋白的变化，HE和Verhoeff 染色观察内膜厚度，TUNEL法观察血管平滑肌细胞(VSMC)凋亡的动态变化。结果:转基因组内膜中PKB基因的mRNA及蛋白产物表达较其他两组明显减少(P＜0.05)；术后7，14，28 d转基因组静脉内膜增生厚度较其他组明显减少(P＜0.01)；转基因组细胞凋亡率较其他组明显增高(P＜0.05)。结论:纳米粒子可以作为转基因载体；沉默PKB基因表达能有效地抑制自体移植静脉内膜的增生，促进VSMC的凋亡。     

反义雷帕霉素靶蛋白基因局部转染对移植静脉内膜增生的影响

目的:观察以纳米粒子为载体的反义雷帕霉素靶蛋白(mTOR)基因局部转染对移植静脉内膜增生的影响。方法:应用聚乳酸聚乙醇酸共聚物(PLGA)和聚乙烯醇(PVA)包载mTOR基因,制备纳米级粒子混合物。检测其包埋率、体外释放情况及粒子大小。建立自体静脉移植模型,随机分成转基因组、空载体组、对照组。转基因组移植静脉转染以纳米粒子为载体的反义mTOR基因,空载体组单纯转染纳米粒子包载的空载体,对照组不予特殊处理。分别于术后3d、7d、14d、28d取材,常规HE、Verhoeff染色,RT-PCR、Westernblot检测mTOR基因的mRNA及蛋白的变化,TUNEL法观察血管平滑肌细胞(VSMC)凋亡的动态变化。结果:转基因组内膜中mTOR基因的mRNA及蛋白产物表达较其他两组明显减少(P<0.05);转基因组内膜增生厚度7d、14d、28d较其他组明显减少(P<0.01);转基因组凋亡细胞较其他组明显增高(P<0.05)。结论:纳米粒子可以作为转基因载体,反义mTOR基因的表达能够有效抑制自体移植静脉内膜的增生,促进VSMC的凋亡。     

早期炎性反应对移植静脉中外源基因表达效率的影响

目的: 探讨早期炎性反应对移植静脉中腺病毒载体转染的外源基因表达效率的影响。方法:通过颈外静脉将携lacZ基因的腺病毒载体注入大鼠的颈总静脉中，使其自然充盈。室温下孵育30min后，将转基因静脉间置移植于颈总动脉。在静脉转基因后3，14，21d取材。经X-Gal(5-溴-4-氯-3-吲哚-D-半乳糖苷)染色检测静脉中标记基因的表达，测定β-半乳糖酶的活性。常规免疫组化染色观察静脉中细胞内黏附分子-1(ICAM-1)及血管细胞黏附分子-1(VCAM-1)的表达。结果:外源基因在体表达14d时β-半乳糖酶活性下降,至21d时活性近消失。静脉移植后3d，VCAM-1和ICAM-1表达上调，白细胞浸润，内皮细胞脱落，内皮层不完整。而未进行移植的转基因静脉，内皮细胞无VCAM-1及ICAM-1的表达，血管壁无炎性细胞浸润，内皮细胞完整。在移植静脉中，阳性内皮细胞数比未移植静脉明显减少（P<0.05），平滑肌细胞数则与未移植静脉相比无明显差别。结论:移植静脉早期炎性反应造成的内皮细胞损伤与转基因表达迅速下降有关。     

Adenoviral-mediated Gene Transfer in Human and Animal Vein Grafts Using Clinically Relevant Exposure Times, Pressures, and Viral Concentrations

This study examined the efficiency of adenoviral-mediated gene transfer in experimental vein grafts and cultured human saphenous vein under physiologic conditions using clinically relevant exposure times, pressures, and viral concentrations. The external jugular veins of 25 male New Zealand White rabbits were exposed to 0.5 mL of replication-deficient adenovirus vectors encoding beta-galactosidase (AdlacZ), control adenovirus (AdBg/II), or vehicle at pressures ranging from 0 to 120 mmHg for 10 min. Veins were excised and grafted into the carotid circulation. After 5 days, the vessels were reexposed, excised, and stained with X-gal chromagen for beta-galactosidase (beta-gal) activity. Gene transfer was also performed in 13 segments of human saphenous vein discarded at the time of bypass grafting. The veins were cultured for 0-21 days and assayed for beta-gal activity as above. Rabbit vein grafts exposed to high-pressure AdlacZ transfection showed significant transgene expression in 100% of grafts (39 +/- 2% positive cells/hpf) while only 60% of those transfected at low pressure expressed beta-gal (9 +/- 3% positive cells/hpf). All human veins exposed to AdlacZ expressed beta-gal to a variable degree (range 10-50% positive cells/hpf). No control grafts or veins expressed the transgene. Efficient adenoviral-mediated gene transfer in experimental vein grafts and human saphenous vein segments can be achieved using clinically feasible parameters of exposure time, pressure, and viral concentration.     

纳米粒子介导反义mTOR基因转染抑制移植静脉内膜增生

目的:观察以纳米粒子为载体的外源性反义雷帕霉素靶蛋白(mTOR)基因局部转染对移植静脉内膜增生的影响。方法:应用聚乳酸聚乙醇酸共聚物(PLGA)和聚乙烯醇(PVA)包载mTOR基因，制备纳米级粒子混合物。建立自体静脉移植模型72只，随机分成转基因组(转染以纳米粒子为载体的反义mTOR基因)，空载体组(单纯转染纳米粒子包载的空载体)和对照组(不予特殊处理)。分别于术后3，7，14，28d取材。检测mTOR基因的mRNA及蛋白产物表达，以及血管平滑肌细胞(VSMC)凋亡的动态变化。 结果:转基因组内膜中mTOR基因的mRNA及蛋白产物表达较其他两组明显减少(P<0.05)；转基因组内膜增生厚度于7，14，28d较其他组明显减少(P<0.01)；转基因组凋亡细胞较其他组明显增高(P<0.05)。结论:纳米粒子可以作为转基因载体。反义mTOR基因的表达能有效抑制自体移植静脉内膜的增生及促进VSMC凋亡。     

Hemagglutinating virus of Japan-liposome–mediated gene transfer of endothelial cell nitric oxide synthase inhibits intimal hyperplasia of canine vein grafts under conditions of poor runoff

Purpose: Late graft failure is a critical problem, particularly in the presence of poor runoff vessels. Intimal hyperplasia is considered to be the main cause of graft failure. We have already reported that intimal thickening of experimental vein grafts in dogs with poor runoff vessels is more pronounced than that in dogs with normal vessels. We and others also have reported that production of nitric oxide (NO) in the endothelium of canine vein grafts is impaired. In the present study, we asked whether in vivo gene transfer of endothelial cell NO synthase (ecNOS) would inhibit intimal hyperplasia of autogenous vein grafts implanted in limbs with poor distal runoff in dogs. Methods: After exposing femoral veins, the nuclear-targeted lac Z gene, bovine ecNOS cDNA, or control vector plasmid encapsulated in the hemagglutinating virus of Japan-liposomes was infused intraluminally, followed by incubation for 10 minutes at room temperature under a distending pressure of 100 mm Hg. Twenty reversed vein grafts were implanted under normal runoff conditions, and 4 days later these were used to confirm gene transfer to the vein grafts. Twelve reversed vein grafts were implanted under conditions of poor runoff, and 4 weeks after the operation intimal thickening was evident. Results: In vein grafts under normal runoff conditions, lac Z gene transfer exhibited diffuse and frequent X-Gal-positive signals in both medial and adventitial layers 4 days after implantation (n = 3). In case of the ecNOS gene–transferred vein grafts, bovine ecNOS protein was mainly detected in medial smooth muscle cells and adventitial cells 4 days after implantation, determined using immunohistochemical techniques and bovine ecNOS specific antibody (n = 3). In addition, ecNOS-transferred vessels showed intense purple signals by reduced nicotinamide adenine dinucleotide phosphate diaphorase and nitroblue tetrazolium reaction, in both medial and adventitial layers, whereas weak NOS activity was recognized at the adventitial vasa vasorum of the untreated veins or control vector transferred veins (n = 3, respectively). In vein grafts under poor runoff conditions, the intimal thickness at 4 weeks after implantation was significantly reduced by ecNOS gene transfer (n = 4; 90.0 ± 7.6 μm and 1.18 ± 0.07 mm²) in comparison with buffer-treated vessels (n = 4; 195.8 ± 25.7 μm and 2.62 ± 0.48 mm²) or vector vehicle–treated vessels (n = 4; 193.0 ± 15.8 μm and 2.65 ± 0.22 mm²). Conclusions: Our findings show that gene transfer of ecNOS inhibited intimal hyperplasia of canine vein grafts caused by poor runoff conditions, as a result of an increased local production of NO. Thus ecNOS gene transfer warrants further study as a possible approach to prevent late graft failure. (J Vasc Surg 1998;27:135-44.)     

The impairment of endothelium-dependent relaxations in reversed vein grafts is associated with a reduced production of cyclic guanosine monophosphate.

The present study investigated the underlying mechanisms associated with the loss of responsiveness of veins grafted into the arterial circulation. In particular, the possibility that the altered response is related to modifications of the biologic properties of the vascular smooth muscle, of the endothelial cells or both was tested. Segments of jugular veins were grafted in the reverse position into the carotid arteries in rabbits. After 4 weeks the patent vein grafts and unoperated veins were removed, and endothelium-dependent (acetylcholine) and endothelium-independent (nitric oxide, SIN-1 [the active metabolite of molsidomine32]) relaxations were studied in vitro. In unoperated veins, acetylcholine, nitric oxide, and SIN-1 induced a concentration-dependent relaxation in the presence and absence of the endothelium, respectively. These relaxations were associated with a time-dependent accumulation of guanosine 3':5'-cyclic monophosphate (cyclic GMP). Both relaxation and production of cyclic GMP were inhibited by methylene blue and hemoglobin. Unstimulated veins with endothelium had a significantly higher content of cyclic GMP than did preparations without endothelial cells. This difference was abolished by hemoglobin and methylene blue. In vein grafts acetylcholine induced only minor endothelium-dependent relaxations, whereas nitric oxide and SIN-1 evoked concentration-dependent relaxations in preparations without endothelium, which were shifted significantly to the right compared to unoperated veins. In vein grafts the endothelium-mediated production of cyclic GMP (basal and stimulated by acetylcholine) was significantly reduced when compared to that in unoperated veins, and that evoked by SIN-1 was not different.(ABSTRACT TRUNCATED AT 250 WORDS)     

Functional abnormalities of experimental autogenous vein graft neoendothelium.

When a vein is grafted into the arterial circulation, the endothelium of the graft is damaged. Regeneration of an intact neoendothelium occurs, but the functional properties of this surface have not been clarified. In this study, the functional integrity of the neoendothelium of veins grafted into the carotid artery of the rabbit was assessed through the use of acetylcholine and histamine to stimulate the production of the important endothelium-derived relaxing factor (EDRF). Control veins, precontracted with norepinephrine [10(-5) M], relaxed after exposure to acetylcholine [( 10(-7) M], 42.4% +/- 6.4%, p = 0.008) and histamine [( 10(-6) M], 30.6% +/- 4.3%, p = 0.03). This relaxation response was abolished after mechanical removal of the endothelium. By contrast, neither acetylcholine nor histamine caused an endothelium-dependent relaxation in the vein grafts, even though scanning electron microscopy demonstrated the presence of a morphologically intact endothelium. However, addition of stabilized EDRF purified from cultured endothelial cells induced relaxation of the vein grafts (35.8% +/- 3.6%, p = 0.002). These data indicate that vein graft endothelium is unable to produce EDRF in response to exposure to acetylcholine or histamine. The inability to produce this potent smooth muscle cell relaxing factor and anti-aggregatory substance may be a predisposition to vein graft failure.     

Atherogenic effect of barotrauma on in situ saphenous veins in monkeys

The objectives of this study were to determine whether veins subjected to barotrauma in situ undergo lipid uptake and morphologic changes to the same extent as veins grafted into the arterial circulation. Saphenous veins in seven stump-tailed macaque monkeys were exposed bilaterally and were circumferentially dissected free from surrounding tissue only at isolated sites. Segments of the veins were distended for 1 minute at hydrostatic pressures of 125 or 350 mm Hg. An undistended segment served as control. A cephalic vein graft was interposed in the femoral artery for comparison with in situ veins. The animals were fed a diet that sustains plasma cholesterol levels of approximately 225 mg/dl. Saphenous veins and the cephalic vein grafts were explanted at 3 months for biochemical and histologic analyses. Cholesterol content in undistended saphenous veins was similar to that in veins distended at 125 or 350 mm Hg--105 +/- 15, 122 +/- 14, and 109 +/- 30 micrograms/100 mg wet tissue weight, respectively. Cholesterol content in cephalic vein grafts, 473 +/- 122 micrograms/100 mg, was greater (p less than 0.001) than in saphenous veins at all distention pressures studied. There was no difference among the distention pressures in the intimal fraction of saphenous vein wall, with the pooled value being 20% +/- 12%. This contrasted with the value of 59% +/- 11% in cephalic vein grafts (p less than 0.01). Endothelial coverage of the luminal surface in saphenous veins was similar among the levels of barotrauma, with the pooled value being 83% +/- 15%. Less of the lumen was covered with endothelium in cephalic vein grafts, 46% +/- 18% (p less than 0.01). Slightly more medial fibrosis was observed in cephalic vein grafts as compared with saphenous veins (p less than 0.05). These data demonstrate that barotrauma alone does not cause veins that remain in the venous system to undergo the lipid uptake or morphologic changes that occur in veins grafted into the arterial circulation in nonhuman primates.     

Cryopreserved Vein Transplantation

There have been numerous attempts to develop prosthetic conduits or utilize allograft saphenous veins for arterial bypass. This article summarizes our experimental and clinical experience with cryopreserved allograft saphenous veins. During these studies, particular attention was paid to vein donor postmortem ischemia time, vein procurement technique, and tissue storage methods. Experimental cryopreserved autograft studies demonstrated that cryopreservation of the veins does not alter subsequent graft patency, the arterialization process, blood flow, or platelet deposition in vein grafts. Endothelium-derived relaxing and contractile factors are produced by the endothelium of explanted cryopreserved autografts, and smooth muscle contractions and relaxations can be induced. In experimental cryopreserved allografts, the endothelium appears to be removed by an immune response during the first 10 days after transplantation, fibrin deposition is minimal, and re-endothelialization occurs over 6-9 months. Early clinical results using cryopreserved allograft saphenous veins are encouraging with 1-year patency rates of 79% for peripheral grafts and 86% for coronary bypass grafts.     

Optimization of ex vivo inducible nitric oxide synthase gene transfer to vein grafts.

BACKGROUND: Vein graft failure as the result of intimal hyperplasia (IH) remains a significant clinical problem. Ex vivo modification of vein grafts using gene therapy is an attractive approach to attenuate IH. Gene transfer of the inducible nitric oxide synthase (iNOS) gene effectively reduces IH. However, iNOS activity after gene transfer may be impaired by the availability of cofactor, such as tetrahydrobiopterin (BH4). The purpose of this study is to determine the optimal conditions for ex vivo adenoviral-mediated iNOS gene transfer into arterial and venous vessels. METHODS: Porcine internal jugular veins and carotid arteries were infected ex vivo with the adenoviral iNOS vector (AdiNOS) and with an adenovirus carrying the cDNA encoding guanosine triphosphate cyclohydrolase I (AdGTPCH), the rate-limiting enzyme for BH4 synthesis. The production of nitrite, cyclic guanosine monophosphate (cGMP), and biopterin were assessed daily. RESULTS: Nitric oxide (NO) production after iNOS gene transfer was maximal when vessels were cotransduced with AdGTPCH. NO production in these vessels persisted for more than 10 days. Vein segments generated approximately 2-fold more nitrite, cGMP, and biopterin than arterial segments infected with AdiNOS/AdGTPCH. Submerging vein segments into adenoviral solution resulted in improved gene transfer with greater nitrite and cGMP release compared with infections carried out under pressure intraluminally. Similarly, injury to the vein segments before infection with AdiNOS resulted in less nitrite production. CONCLUSIONS: These data demonstrate that AdiNOS can efficiently transduce vein segments ex vivo and that the cotransfer of GTPCH can optimize iNOS enzymatic activity. This cotransfer technique may be used to engineer vein grafts before coronary artery bypass to prevent IH.     

Pro-UK基因抑制静脉移植物细胞增生的实验研究

目的：探讨Ｐｒｏ－ｕｋ基因对静脉桥移植物细胞增生的影响。方法：３００￣３５０ｇ Ｗｉｓｔａｒ大鼠４２只,取下双鼠颈静脉,两端阻断后,用含Ａｄｖ５－ＣＭＶ／Ｐｒｏ－ＵＫ质粒（治疗组,２１只）的溶液扩张静脉,使溶液在静脉 腔内滞留３０分钟降温末然后置于同一大鼠的颈总动脉。术后２８天,取静脉移植物行尿激酶原活性测定,观察Ｐｒｏ－ＵＫ表达（２６５ｉｕ／ｇｔｉｓｓｕｅ）,对照组未测到Ｐｒｏ－ＵＫ活性。虽然两     

Intraluminal gene transfer of endothelial cell-nitric oxide synthase suppresses intimal hyperplasia of vein grafts in cholesterol-fed rabbit: a limited biological effect as a result of the loss of medial smooth muscle cells

BACKGROUND: The intimal hyperplasia of vein grafts is a major cause of late graft failure and is more pronounced under hyperlipidemia. We previously reported that endothelial cell (ec)-type nitric oxide synthase (NOS) gene transfer inhibited graft intimal hyperplasia under poor runoff conditions. However, little information is available on either ecNOS gene transfer or intimal thickening under hypercholesterolemia. METHODS: Using the hemagglutinating virus of Japan liposomes, bovine ecNOS complentary DNA (5000 hemagglutinating activity units/mL) was transfected intraluminally to the right jugular vein, and these veins were then implanted as reversed vein grafts in an end-to-side fashion to the ipsilateral carotid artery. RESULTS: The cyclic guanosine 3',5'-monophosphate content of the ecNOS vein significantly increased in the grafts at 4 days after gene transfer, but the levels were only 25% greater than those found in the untreated veins. An immunohistochemical analysis at the same time suggested a large loss of medial smooth muscle cells that might have led to a reduction in the exogenous gene expression. The neointima of the ecNOS grafts was significantly reduced 4 weeks after implantation (P <.05), but the effect of ecNOS was limited to about a 30% inhibition. This reduction was associated with a reduced population of proliferating cells and decreased macrophage accumulation in the graft wall. CONCLUSIONS: These results demonstrated that the ecNOS gene transfer suppressed intimal hyperplasia of the vein grafts under hyperlipidemic conditions. However, this effect may be limited because of the smooth muscle cell loss related to the use of an intraluminal delivery methods. These data lead to speculation that the outcome of ecNOS gene transfer could be improved using different methods of gene delivery.     

Effects of gene transfection of human bcl-2 on concordant cardiac xenografts in hamster to rat model

OBJECTIVES: Concordant cardiac xenografts are known for delayed vascular rejection. Therapy combining with FK506 and cobra venom factor prolongs graft survival. The proposed underlying mechanism holds that cytoprotective proteins such as Bcl-2 play a role here. We studied the effects of gene transfection of human-bcl-2 on graft survival and coronary artery lesions in concordant cardiac xenografts, and discuss the role of cytoprotective genes in vascular xenograft rejection. METHODS: Golden-Syrian-hamster hearts were heterotopically transplanted into Lewis rats given FK506 (1 mg/kg daily) and cobra venom factor (0.2 mg/kg; day 0 and 1) intramuscularly. They were divided into 2 groups--grafts transfected vector with the human-bcl-2 gene (Group-B(+)) and vector without the gene (Group-B(-)) using the HVJ liposome method; 4 or 5 grafts from each group were explanted 1, 2, 3, or 4 weeks and more than 1 month after transplantation and evaluated by H-E, Elastic-Van-Gieson and immunohistochemical staining of Bcl-2. Coronary arterial lesions were examined using a scoring method. RESULTS: Bcl-2 expression in endothelial cells in Group-B(+) was confirmed within 2 weeks after transplantation but not thereafter. The coronary score in Group-B(+) was significantly lower than that in Group-B(-) within 2 weeks after transplantation but not thereafter. CONCLUSIONS: In this hamster-to-rat cardiac xenograft model, the bcl-2 gene was successfully transfected to the coronary endothelium and lasted 2 weeks. During Bcl-2 expression, coronary vascular lesions were suppressed more than in the untransfected group.     

Adenovirus-mediated gene transfer of human inducible nitric oxide synthase in porcine vein grafts inhibits intimal hyperplasia.

OBJECTIVE: The aim of this study is to determine whether adenoviral inducible nitric oxide synthase (iNOS) gene transfer could inhibit intimal hyperplasia (IH) in porcine internal jugular veins interposed into the carotid artery circulation. METHODS: Porcine internal jugular veins were transduced passively with 1 x 10(11) particles of an adenoviral vector carrying either the human iNOS (AdiNOS) or beta-galactosidase (AdlacZ) cDNA for 30 minutes and then interposed into the carotid artery circulation. Segments of each vein graft were maintained in an ex vivo organ culture to measure nitrite accumulation, a marker of nitric oxide synthesis. The grafts were analyzed immunohistochemically for the presence of neutrophils, macrophages, and leukocytes by staining for myeloperoxidase, ED1, and CD45, respectively, at 3 (n = 4) and 7 (n = 4) days. Morphometric analyses and cellular proliferation (Ki67 staining) were assessed at 3 (n = 4), 7 (n = 4), and 21 days (n = 8). RESULTS: AdlacZ-treated vein grafts demonstrated high levels of beta-galactosidase expression at 3 days with a gradual decline thereafter. Nitrite production from AdiNOS-treated vein grafts was approximately fivefold greater than AdlacZ-treated grafts (P =.00001). AdiNOS or AdlacZ treatment was associated with minimal graft inflammation. Cellular proliferation rates were significantly reduced in AdiNOS-treated grafts as compared with controls at both 3 (41%, P =.000004) and 7 days (32%, P =.0001) after bypass. This early antiproliferative effect was most pronounced at the distal anastomosis (65%, P =.0005). The iNOS gene transfer reduced the intimal/medial area ratio in vein grafts at 7 (36%, P =.009) and 21 days (30%, P =.007) versus controls. This inhibition of IH was again more prominent in the distal segments of the grafts (P =.01). CONCLUSION: Adenovirus-mediated iNOS gene transfer to porcine internal jugular vein grafts effectively reduced cellular proliferation and IH. Although iNOS gene transfer reduced IH throughout the entire vein graft, the most pronounced effect was measured at the distal anastomosis. These results suggest potential for iNOS-based genetic modification of vein grafts to prolong graft patency.     

Optimal techniques for harvesting and preparation of reversed autogenous vein grafts for use as arterial substitutes: a review

Since the first successful use of an autogenous vein graft for arterial reconstruction by Gluck in 1898 and the establishment of the scientific basis for the use of veins as arterial substitutes by Carrell and Guthrie in the early 1900s, reversed autogenous veins have been used extensively in arterial reconstructive operations. Despite being the preferred material for reconstruction, reversed autogenous vein is not an ideal graft material. The primary problem is structural alterations in the implanted vein predisposing to graft failure. Most of these failures occur within the first few months after graft implantation and are though to be due, in part, to endothelial damage incurred during harvesting and preparation of the vein. This review focuses on technical aspects of vein graft harvesting associated with alterations in endothelial morphology including dissection technique, types of irrigation and storage solutions used, temperature of these solutions, distension pressures, and pharmacologic agents. An optimal technique incorporating subcutaneous and perivenous infiltration with papaverine, atraumatic dissection, controlled gradual distension, and storage of the distended vein in cold heparinized blood containing papaverine should produce grafts with improved endothelial preservation and patency rates compared with grafts harvested by techniques in widespread use at present. The importance of morphologically and functionally intact endothelium in reversed vein grafts, a comparison to that produced by in situ vein grafting, and its possible clinical implications are discussed.     

Cryopreservation affects endothelial and smooth muscle function of canine autogenous saphenous vein grafts

Cryopreserved veins used as arterial grafts may be affected by both rejection and the cryopreservation process. Experiments were designed to study changes in endothelial and smooth muscle function after cryopreservation but independent of rejection. One saphenous vein from each of eight dogs was cryopreserved for subsequent use as autografts. After 3 weeks one cryopreserved and one freshly harvested autogenous saphenous vein were implanted as bilateral femoral arterial interposition grafts. Platelet deposition was studied in vivo with indium 111-labeled platelets. At 4 weeks the autografts were removed, and the functional characteristics of the grafts were studied in organ chambers; and the ability of nerve terminals to uptake transmitter was studied with 3H-norepinephrine. Neither patency rates, blood flows, nor platelet deposition were significantly different between freshly harvested and cryopreserved grafts. Uptake of 3H-norepinephrine was significantly reduced in both grafts as compared to unoperated veins. The smooth muscle of the cryopreserved and fresh grafts contracted comparably to alpha-adrenergic agonists and endothelin. In cryopreserved grafts, the maximal tensions that developed to KCl, prostaglandin F2 alpha, and endothelin were greater when the endothelium was present compared to that developed by the smooth muscle alone. Calcium ionophore A23187 caused relaxations only in rings with endothelium; these were not significantly different between graft types. However, relaxations of the smooth muscle to nitric oxide were decreased in the cryopreserved grafts.(ABSTRACT TRUNCATED AT 250 WORDS)