Antisense basic fibroblast growth factor alters the time course of mitogen-activated protein kinase in arterialized vein graft remodeling

PURPOSE: Neointimal hyperplasia (NIH) is complete by 3 weeks in rabbit vein grafts implanted into the arterial circulation. Activation of the mitogen-activated protein kinase (MAPK) family of protein kinases is thought to be critical in remodeling events such as cellular proliferation, differentiation, and migration, as found in NIH. We previously demonstrated that antisense basic fibroblast growth factor (ASbFGF) inhibited the synthesis of basic fibroblast growth factor (bFGF) in the balloon injury model of NIH. We examined the effect of ASbFGF on NIH and the time course of MAPK, extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal protein kinase (JNK), and p38 kinase activation in arterialized vein grafts. METHODS: Carotid interposition of a vein bypass graft was performed in 75 New Zealand White rabbits. Segments of the external jugular vein were transfected with a replication-deficient adenovirus containing the messenger RNA sequence for rat ASbFGF at 1 x 10(10) plaque-forming units per milliliter; control animals were given phosphate-buffered saline solution (PBS) alone. Rabbits were killed at 30 minutes, 4 days, 7 days, and 21 days (n = 8). Four grafts in each group were fixed with formalin and embedded in paraffin, then processed with elastin-collagen and hematoxylin-eosin stains. The other four grafts were individually frozen, and total protein was extracted. Phosphorylation of MAPK, ERK1/2, JNK, and p38, was determined with Western blot analysis and immunohistochemistry. Groups were compared with analysis of variance. RESULTS: The thickness of neointima in the PBS group and the ASbFGF group at 21 days was 60.2 +/- 2.1 and 39.4 +/- 2.1 microm, respectively (P <.01). In both the control and ASbFGF groups, all 3 MAPKs demonstrated activation compared with preimplantation levels. However, when compared with the PBS group the ASbFGF group showed greater than 33% inhibition of all three MAPKs by day 4 and day 7 (P <.05), but no significant difference in any MAPK activation by day 21 (P >.05, all groups). Cells staining positive for activated MAPK were found in the neointima and adventitia of vein grafts in both the PBS and ASbFGF groups. CONCLUSION: MAPKs are activated during the first week after vein graft implantation. Grafts treated with ASbFGF demonstrated reduced MAPK activation and less neointimal thickening. These results suggest that the process of vein graft adaptation to the arterial circulation, and subsequent NIH, may depend on basic fibroblast growth factor activity, which is mediated, at least in part, by a MAPK-dependent mechanism.     

Effect of wall shear stress on intimal thickening of arterially transplanted autogenous veins in dogs

To determine whether or not changes in wall shear stress play a determinant role in the induction of hyperplasia of intimal tissue of arterially transplanted vein grafts, we developed two models of canine femoral arteries. Wall shear stress was defined by variation of wall shear stress (tau-variation) in the cardiac cycle, with the use of a newly designed computational flow waveform analyzer. In the group I model autogenous vein grafts were implanted under flow conditions of 79.7 +/- 3.2 ml/min of the normally high flow rate with 33.1 +/- 1.9 dynes/cm2 of low tau-variation. In the group II model grafts were implanted under conditions of 2.9 +/- 1.8 ml/min of low flow rate with 178.8 +/- 11.0 dynes/cm2 of normally high value of tau-variation. The intimal thickness of 259 +/- 36 microns 4 weeks after implantation in group I was statistically significant compared with that of 31 +/- 14 microns in group II (p less than 0.005). Our study revealed that change in wall shear stress and not the rate of blood flow is the essential hemodynamic factor related to intimal hyperplasia.     

Early adaptation of human lower extremity vein grafts: wall stiffness changes accompany geometric remodeling

OBJECTIVE: To quantitatively describe the temporal changes in elastic properties and wall dimensions in lower-extremity vein grafts after implantation. DESIGN OF STUDY: This is a prospective study of patients (N = 38) undergoing lower extremity bypass grafts (N = 41) with autologous veins. Pulse wave velocity (PWV), luminal diameter, and wall thickness measurements were obtained by duplex ultrasound scan intraoperatively and at 1, 3, and 6 months postoperatively for assessment of graft dimensions and wall stiffness. RESULTS: Lower extremity vein grafts showed an increase in PWV (from 16 +/- 1 to 21 +/- 3 cm/s; mean +/- SEM; P =.08), reflecting an increase in wall stiffness (from 1.2 +/- 0.2 to 2.5 +/- 0.7 x 10(6) dynes/cm; P =.02) and wall thickness (from 0.47 +/- 0.03 to 0.61 +/- 0.004 mm; P =.04) over the first 6 months after implantation. Changes in lumen diameter were positively correlated with changes in external graft diameter (P <.01) and negatively correlated with initial lumen diameter (P <.01) but not with changes in the wall thickness. CONCLUSIONS: These results suggest complex remodeling of vein grafts during the first several months after implantation, with increased wall thickness occurring independent of variable changes in lumen diameter. Simultaneously, a marked increase in wall stiffness over this interval suggests a likely role for collagen deposition.     

Shear stress regulation of artery lumen diameter in experimental atherogenesis

We studied the adaptive response of the arterial wall and intimal thickening under conditions of increased flow in an atherogenic model. Blood flow was increased by construction of an arteriovenous fistula between the right iliac artery and vein in six cynomolgus monkeys fed a diet containing 2% cholesterol and 25% peanut oil. The left iliac artery served as the control. Serum cholesterol increased from 135 +/- 22 mg/dl to 880 +/- 129 mg/dl during the experiment. After 6 months, blood flow in the right iliac artery (420 +/- 95 ml/min) was 10 times greater than in the left iliac artery (44 +/- 9 ml/min, p less than 0.005). Flow velocity in the right iliac artery (31 +/- 6 cm/sec) was more than twofold greater than in the left (12 +/- 1 cm/sec, p less than 0.05). Despite the marked difference in blood flow and flow velocity, calculated wall shear stress was the same in both the right (16 +/- 4 dynes/cm2) and left iliac vessels (15 +/- 2 dynes/cm2) because of a twofold increase in lumen diameter (p less than 0.001) of the right iliac artery. Shear stress in the aorta was also normal (12 +/- 2 dynes/cm2). There was no difference in plaque deposition or mean intimal thickness between the right and left iliac arteries. In the right iliac artery there was a twofold increase in media cross-sectional area (p less than 0.001) but no change in media thickness or total wall thickness. Tangential wall tension and tangential wall stress were two times greater on the right than on the left (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Non-penetrating vascular clips anastomosis inhibited intimal thickening under poor runoff conditions in canine autogenous vein grafts.

OBJECTIVE: Late graft failure is still a significant problem, particularly in cases with poor runoff vessels. The main cause of late graft failure is intimal thickening of the anastomotic region. Vascular closure system (VCS) clips may provide ideal anastomosis, since they do not penetrate the wall. Therefore, we examined whether the VCS clips affect intimal thickening under poor runoff conditions in the canine autogenous vein grafts. METHODS: A canine poor runoff model was prepared at both femoral veins. Four weeks after the first surgical procedure, two groups were established according to the two different methods of anastomosis employed. The right femoral vein graft was performed using polypropylene sutures, conventional surgical anastomosis (control group), while the left femoral vein graft was performed using VCS clips anastomosis (VCS group). Four weeks after grafting, the vein grafts were removed and the intimal thickening of proximal, distal anastomosis and midportion of the vein grafts were examined histologically. RESULTS: In the control group, flow rate and variation were 26+/-8 ml/min and 51+/-10 dynes/cm(2), respectively. In the VCS group, the flow rate and variation were 23+/-11 ml/min and 44+/-14 dynes/cm(2), respectively. There were no significant differences between the two groups. The average value of intimal thickening of both the anastomotic region and the midportion of the vein graft in the VCS group was significantly inhibited compared to that of the control group. The number of positive cells of masson trichrome stain in the VCS group was significantly less than that of the control group. CONCLUSIONS: These experiments indicate that VCS clips significantly inhibit intimal thickening under poor runoff conditions in canine autogenous vein grafts to a greater extent compared to suture-constructed anastomosis. One mechanism that may account for the decreased intimal thickening is the inhibition of the expression of transforming growth factor-beta (TGF-beta), because the number of positive cells of masson trichrome stain in the VCS group was significantly less than that of the control group.     

Ultrastructural evidence of the effects of shear stress variation on intimal thickening in dogs with arterially transplanted autologous vein grafts

Based on our findings that changes in wall shear stress, not the rate of blood flow, were the main hemodynamic factor related to intimal hyperplasia of autologous vein grafts, we further investigated the effect of wall shear stress variation on sequential ultrastructural changes in the intimal hyperplasia of arterially transplanted autovein grafts, using canine models. As noted, wall shear stress variation (tau-variation) could be defined by the variation in wall shear stress within a cardiac cycle, using a desktop flow waveform analyzer. In Group I, which had a high flow rate of 78.4 +/- 4.6 ml/min and low tau-variation of 36.1 +/- 2.2 dynes/cm2, intimal hyperplasia was significant. Ultrastructurally, there was a marked transformation of intimal smooth muscle cells to secretory cells 2 to 4 weeks after implantation. The surface of the intima was lined with modified smooth muscle cells at 2 weeks after implantation. In Group II, which had a low flow rate of 5.6 +/- 2.2 ml/min and normal tau-variation value (174.6 +/- 13.0 dynes/cm2), intimal hyperplasia was minimal, and there were several layers of contractile type smooth muscle cells, with characteristic myofibrillae. The surface of the intima was lined with endothelial cells at 2 weeks after implantation. These findings suggest that, in regions of low wall shear stress variation, intimal smooth muscle cells of autovein grafts may well become secretory cells, and enhanced platelet adherence could occur during early intimal repair, causing intimal hyperplasia to develop.     

The variation in vein graft flow velocity with luminal diameter and outflow level.

Duplex scanning has recently been used to monitor the patency of infrainguinal vein grafts. Empirically derived criteria that have been used for identifying the failing graft have never accounted for the effect of vein graft diameter or varying outflow resistance, despite the fact that they are major determinants of flow. We prospectively examined the variation in graft peak systolic flow velocity with graft diameter and outflow level in a consecutive series of 68 patients with 72 normally functioning vein grafts returning for routine follow-up. Images were obtained of vein grafts with a duplex scanner throughout their lengths, and the distal peak systolic flow velocity and intraluminal diameters were recorded. There were 15 popliteal, 26 tibial, and 21 inframalleolar grafts. The mean ankle-brachial index of inframalleolar grafts was 1.01 +/- 0.04 and did not differ significantly from tibial (0.96 +/- 0.03) or popliteal (0.93 +/- 0.06) grafts (p = 0.32). Grafts to the three outflow levels differed significantly in diameter, with inframalleolar grafts measuring 3.95 +/- 0.17 mm, tibial grafts 4.78 +/- 0.21 mm, and popliteal grafts 5.65 +/- 0.38 mm (p = 0.0001). In a similar manner inframalleolar grafts had significantly lower peak systolic flow velocities (59.1 +/- 3.4 cm/sec) than tibial (77.2 +/- 5.6 cm/sec) or popliteal (71.0 +/- 7.6 cm/sec) grafts (p = 0.04). Inframalleolar grafts did not demonstrate a significant correlation (r = -0.21, p = 0.29) between peak systolic flow velocity and graft diameter. Conversely, both tibial (r = -0.49, p = 0.005) and popliteal (r = -0.73, p = 0.002) grafts demonstrated significant inverse correlations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic profiles during piggyback liver grafts using arterial or portal revascularization

BACKGROUND: The order of revascularization in human liver grafts is still discussed. This study tries to answer this question in terms of hemodynamic data. STUDY DESIGN: Fifty-nine patients were randomized in this study to compare hemodynamic data just before and 15 minutes after revascularization of liver grafts in relation to first hepatic artery (n = 29) or first portal vein (n = 30) revascularization procedure. RESULTS: Hemodynamic variations were significantly greater in the portal vein group than in the hepatic artery group in terms of mean arterial pressure, cardiac index, central venous pressure, pulmonary capillary pressure, and systemic vascular resistance. The latter decreased from 741.8 +/- 390.3 to 659.9 +/- 411.1 dynes/ cm5 (NS) in the hepatic artery group versus 807.7 +/-336.7 to 439.7 +/- 215 dynes/cm5 (p < 0.05) in the portal vein group. Clinical results and postoperative complications, graft characteristics, patient survival, and graft survival were not significantly different between the groups. CONCLUSIONS: Initial arterial revascularization of the liver graft leads to a more stable hemodynamic profile during revascularization of the liver graft after vascular unclamping. This technique is always feasible and has become our reference procedure.     

Connective tissue changes in a mouse model of vein graft disease

AIM: The extracellular matrix plays an important physiological role in the architecture of the vascular wall. In arterialized vein grafts severe early changes, such as thrombosis and neointimal hyperplasia occur. Paclitaxel is in clinical use as antiproliferative coating of coronary stents. We aimed to investigate the early connective tissue changes in arterialized vein grafts and the influence of perivascular paclitaxel treatment in an in vivo model. METHODS: C57 black mice underwent interposition of the vena cava into the carotid artery. Neointimal hyperplasia, thrombosis, acid mucopolysaccharides (Alcian), collagen fibers (trichrome Masson), elastic fibers, and apoptosis rate (TUNEL) were quantified in paclitaxel treated veins and controls. RESULTS: In both, controls and paclitaxel treated vein grafts acid mucopolysaccharides and elastic fibers were found predominantly in the neointima, whereas collagen fibers were found mainly in the media and adventitia. At 4 weeks postoperatively the neointimal thickness in controls was 52 (13-130) microm, whereas in 0.6 mg/mL l paclitaxel treated veins it was 103 (43-318) microm (P=0.094). At 8 weeks postoperatively paclitaxel treated veins showed a significantly increased neointimal thickness of 136 (87-199) microm compared with 79 (62-146) microm in controls (P=0.032). There was no difference in apoptosis rate between the two groups (P=NS). Even with the lowest concentration of 0.008 mg/mL paclitaxel veins showed a neointimal thickness of 67 (46-205) microm at 4 weeks postoperatively (P=NS vs controls). CONCLUSION: Early vein graft disease is characterised by an accumulation of acid mucopolysaccharides and elastic fibers in the thickened neointima. Paclitaxel treatment increases the neointimal hyperplasia in mouse vein grafts in vivo.     

Perivascular application of C-type natriuretic peptide attenuates neointimal hyperplasia in experimental vein grafts.

OBJECTIVE: C-type natriuretic peptide (CNP), which is produced by vascular endothelial cells, exhibits anti-proliferative and anti-inflammatory effects. Cytotoxic T-lymphocytes may be involved in vein graft disease. Attenuation of vein graft disease necessitates a remodelling of the arterialized vein towards a more contractile phenotype which is characterized, among other factors, by the calponin amount. We investigated the effects of perivascularly applied CNP in a mouse model of vein graft disease. METHODS: C57BL6J mice underwent interposition of the inferior vena cava from isogenic donor mice into the common carotid artery using a previously described cuff technique. In the treatment group, 10(-6)mol/l of CNP were applied locally in pluronic gel. The control group did not receive local treatment. Grafts were harvested at 1, 2, 4, and 8 weeks and underwent morphometric analysis as well as immunohistochemical analysis. RESULTS: In grafted veins without treatment (controls) median intimal thickness was 10 (6-29), 12 (8-40)microm, was 47 (12-58), and 79 (62-146)microm after 1, 2, 4 and 8 weeks, respectively. In the treatment groups, which received 10(-6)mol/l of CNP, the intimal thickness was 5 (3-6), 6 (4-15), 32 (5-54), and 43 (39-70)microm after 1, 2, 4 and 8 weeks, respectively. This reduction of intimal thickness was significant at 1, 2 and 8 weeks. Immunohistochemically, the reduction of intimal thickness was associated with a decreased infiltration of CD-8 positive cells and an increased amount of calponin in the CNP-treated grafts. CONCLUSION: We conclude that perivascular application of CNP inhibits neointimal hyperplasia of vein grafts in a mouse model. These results suggest that CNP may have a therapeutic potential for the prevention of vein graft disease.     

Early biomechanical changes in lower extremity vein grafts--distinct temporal phases of remodeling and wall stiffness

BACKGROUND: The geometric and biomechanical changes that contribute to vein graft remodeling are not well established. We sought to measure patterns of adaptation in lower extremity vein grafts and assess their correlation with clinical outcomes. METHODS: We conducted a prospective, longitudinal study of patients undergoing infrainguinal reconstruction with autogenous conduit. In addition to standard duplex surveillance, lumen diameter (of a defined index segment of the conduit) and pulse wave velocity (PWV) were assessed by ultrasound imaging at surgery and at 1, 3, and 6 months postoperatively. Graft dimensions and wall stiffness were correlated with clinical outcomes. RESULTS: There were 92 patients and 96 limbs in this study. On average, vein graft lumen diameter increased during the first month of implantation from 0.37 +/- .01 cm to 0.45 +/- 0.02 cm (mean +/- SEM; P = .002), representing a relative change of +21.6% (median +/- 14%; range, -31 to +67%) during this period. Of the entire cohort, 72% of grafts demonstrated appreciable dilation of the index segment during the first month. Index segment lumen diameter did not change appreciably beyond 1 month, with the notable exception of arm vein conduits, which showed continued tendency to dilate. PWV increased during the first 6 months (17.2 +/- 1.2 m/s to 23.2 +/- 2.4 m/s; P = .008), reflecting a nearly 40% increase in conduit stiffness (2.0 +/- .6 Mdynes/cm to 3.3 +/- .8 Mdynes/cm, P = .01). The greatest relative increase (25%) in PWV occurred from months 1 to 3. Loss of primary patency occurred in 24 cases (19 revisions, 5 occlusions), with a mean reintervention time of 7.6 months. Grafts that demonstrated early positive remodeling (lumen dilatation) had a trend of increased primary patency (P = .08, log rank). Among the grafts that failed, a trend was noted toward greater wall stiffness at 1 month, 2.7 vs 1.5 Mdynes (P = .08). CONCLUSION: Vein graft remodeling appears to involve at least two distinct temporal phases. Outward remodeling of the lumen occurs early, and wall stiffness changes occur in a more delayed fashion. Early outward remodeling may be important for successful vein graft adaptation.     

Improved microcirculation of a liver graft by controlled portal vein arterialization

BACKGROUND: The clinical results of portal vein arterialization (PVA) in liver transplantation are controversial without a standardized portal flow regulation. The aim of these experiments was to perform a flow-regulated PVA in liver transplantation, to examine the microcirculation and early graft function after heterotopic auxiliary liver transplantation (HALT) with flow-regulated PVA, and to compare this technique with HALT with porto-portal anastomosis. Using the recently developed orthogonal polarization spectral (OPS) imaging, for the first time the microcirculation of liver grafts with PVA was visualized. MATERIALS AND METHODS: HALT was performed in Lewis rats. The portal vein was either completely arterialized via the right renal artery in a standardized splint-technique (Group I, n = 8) or anastomosed end-to-end to the recipient's portal vein (Group II, n = 8). RESULTS: After reperfusion, the average blood flow in the portal vein was within the normal range in Group I (1.7 +/- 0.4 ml/min/g liver weight) and significantly higher than in Group II (1.2 +/- 0.2 ml/min/g liver weight). The functional sinusoidal density in Group I (335 +/- 48/microm) was significantly higher than in Group II (232 +/- 58/microm), whereas the diameter of the sinusoids and the postsinusoidal venules yielded no significant differences between both groups. The bile production was comparable (27 +/- 8 versus 29 +/- 11 microl/h/g liver weight). CONCLUSIONS: In our experiments it was possible to achieve an adequate flow regulation in the arterialized portal vein with good results concerning microcirculation and early graft function. We recommend that further investigations on liver transplantation with PVA should be performed with portal flow regulation, before PVA is employed in clinical transplantation.     

移植损伤对移植静脉影响的实验研究

目的探讨移植静脉再狭窄的机制,明确移植损伤对移植静脉的影响。方法健康新西兰大白兔36只,随机选取一侧将股静脉翻转后移植于同侧股动脉缺损(静-动组),另一侧将同等长度股静脉截取后行原位缝合(静-静组),另取正常股静脉作为对照组(取自静-动组移植前静脉的一部分)。均于术后4周取移植静脉段,行HE染色、弹力纤维的维多利亚蓝染色观察移植静脉管壁组织学变化;增殖细胞核抗原(proliferatingcellnuclearantigen,PCNA)免疫组织化学染色观察管壁细胞增殖情况;电镜观察管壁细胞超微结构改变。结果静-静组血管壁中膜平滑肌细胞增殖,但内膜(3.50±0.41μm)、中膜(12.23±1.59μm)厚度无明显变化;静-动组内膜、中膜细胞均增殖,内膜(25.60±3.21μm)、中膜(21.30±2.47μm)厚度较对照组、静-静组均增加,差异有统计学意义(P<0.01)。对照组未见PCNA阳性细胞,静-静组内膜(5.9%±1.3%)、中膜(23.4%±3.4%)PCNA阳性细胞百分比均小于静-动组内膜(16.4%±1.9%)、中膜(36.5%±3.7%),差异有统计学意义(P<0.01)。静-静组透射电镜下可见内皮细胞扁平,游离端有绒毛样突起,细胞排列紧密,中膜平滑肌细胞增殖;静-动组透射电镜下可见内皮细胞增殖明显,增殖的内皮细胞形态不规则,细胞间隙增宽,内膜中可见大量平滑肌细胞,基底膜不完整,中膜平滑肌细胞明显增殖;对照组内皮细胞形态及排列与静-静组相似,只是中膜平滑肌细胞未见增殖。结论静脉移植后可导致血管管壁细胞增殖,如合并血流动力学变化则会发生更严重的细胞增殖和迁移,导致管腔狭窄;减少移植损伤,改善移植静脉的微循环,成为预防移植静脉再狭窄的理论基础之一;静-静移植的动物模型,有助于探寻静脉移植后再狭窄的机制。     

Estimation of intraoperative aortocoronary bypass saphenous vein graft circumference from its preoperative compliance

The aim of this study was to determine if the intraoperative circumference of aortocoronary saphenous vein bypass grafts could be predicted from preoperative measurement with B-mode ultrasound sonography in 50 patients. The circumference of the saphenous vein was measured during stepwise increments of a thigh congestive cuff from 0 to 60 mmHg. The circumference of the corresponding segment of the coronary bypass vein graft was measured intraoperatively with callipers. The intraoperative circumference was higher (11.8+/-2.3 mm) than the preoperative circumference (10.2+/-2.4 mm, P=0.006) matched to its corresponding intraoperative mean arterial pressure (57+/-15 mmHg). The prediction of the intraoperative circumference by estimation from the preoperative pressure-circumference relationship fitted by a linear model (r = 0.412, P = 0.004) did not improve on the preoperative circumference matched by arterial pressure alone (r = 0.429, P = 0.003). The intraoperative circumference of the graft vein exceeded its preoperative circumference by 12%. Prediction of the intraoperative graft vein circumference is underestimated by a linear model of its preoperative compliance.     

Platelet-derived growth factor production by canine aortic grafts seeded with endothelial cells.

The advantages of an endothelial cell surface on a prosthetic graft may be compromised by endothelial cell production of mitogens for smooth muscle cells. To study platelet-derived growth factor (PDGF) production by cells lining prosthetic grafts, 15 beagles underwent placement of 20 to 22 cm long, 8 mm inner diameter, expanded polytetrafluoroethylene thoracoabdominal aortic grafts, of which seven were seeded with autologous jugular vein endothelial cells, and eight were unseeded control grafts. Grafts and adjacent arteries were explanted after 4 weeks, divided into segments, and studied in organ culture. Platelet-derived growth factor production during a 72-hour incubation period was measured by radioreceptor assay. Midgraft segments of seeded grafts produced significantly more PDGF than control grafts, 43 +/- 8 pg/cm2 and 22 +/- 5 pg/cm2, respectively (mean +/- SEM), p less than 0.05. Platelet-derived growth factor production correlated directly with endothelial cell coverage on graft segments as measured by scanning electron microscopy (r = 0.63, p = 0.01), and inversely with platelet deposition (r = -0.48, p = 0.07). For all dogs, PDGF production by the distal aorta was significantly greater than that by the proximal aorta, 89 +/- 6 and 17 +/- 4 pg/cm2, respectively (p less than 0.0001). These results suggest that endothelial cells on prosthetic vascular grafts are a significant source of PDGF. Furthermore, the higher PDGF production by the distal arteries may offer an explanation for the clinical finding of more severe intimal hyperplasia adjacent to the distal anastomosis.     

Influence of ischemic injury on vein graft remodeling: role of cyclic adenosine monophosphate second messenger pathway in enhanced vein graft preservation

OBJECTIVE: Endothelial injury during the harvest of saphenous vein grafts might play an important role in the development of vein graft disease after coronary artery bypass grafting. Using a murine autologous arterialized vein patch model, we tested whether the initial ischemic insult of vein grafts was linked to the later development of graft neointimal hyperplasia and whether the restoration of the cyclic adenosine monophosphate second messenger pathway would attenuate the development of neointimal hyperplasia. METHODS: A segment of the external jugular vein of a mouse was grafted onto its abdominal aorta. Three weeks after the operation, the degree of neointimal hyperplasia of the implanted graft was compared among (1) grafts without preservation, (2) grafts with 2 hours of preservation (25 degrees C) in heparinized saline, and (3) grafts with 2 hours of preservation in heparinized saline in the presence of a cyclic adenosine monophosphate analog. In addition, cyclic adenosine monophosphate contents of vein grafts and leukocyte adherence to the graft endothelium were assessed. RESULTS: Cyclic adenosine monophosphate contents were significantly decreased after 2 hours of preservation (212 +/- 8 vs 156 +/- 5 pmol/L, P < .01). The grafts preserved for 2 hours showed greater neointimal hyperplasia compared with the grafts without preservation (neointimal expansion, 68.7% +/- 9.6% vs 46.1% +/- 4.8%; P < .01). The addition of a cyclic adenosine monophosphate analog to the preservation solution significantly suppressed neointimal hyperplasia of grafts preserved for 2 hours (44.3% +/- 5.0%). Inhibiting the cyclic adenosine monophosphate-dependent protein kinase by adding Rp-cAMPS abrogated the beneficial effects. Furthermore, grafts preserved for 2 hours had significantly more leukocytes adhering to the graft endothelium 24 hours after the operation compared with nonpreserved grafts, which was significantly reduced by the cyclic adenosine monophosphate treatment. CONCLUSIONS: Ischemic insult during vein graft harvest and preservation is a key factor in the development of vein graft neointimal hyperplasia at least in part caused by the depletion of cyclic adenosine monophosphate. We conclude that stimulation of the cyclic adenosine monophosphate second messenger pathway might be a potential strategy for the prevention of vein graft disease.     

Auxiliary liver transplantation with flow-regulated portal vein arterialization offers a successful therapeutic option in acute hepatic failure – investigations in heterotopic auxiliary rat liver transplantation

Heterotopic auxiliary liver transplantation (HALT) with portal vein arterialization (PVA) was proposed in acute hepatic failure (AHF). However, clinical results of PVA are controversial because of lacking standardized flow-regulation. In rats, we examined HALT with flow-regulated PVA in AHF. Group A: HALT with flow-regulated PVA and 85% resection of the native liver to induce AHF [acute experiments (n = 8), killing after 7 days (n = 8) and after 6 weeks (n = 11)]. Group B: 85% liver-resection (n = 10). The average blood-flow in the arterialized portal vein in HALT achieved normal values (1.7 +/- 0.4 ml/min/g liver-weight). After reperfusion, the diameters of the sinusoids (6.4 +/- 0.6 microm), the postsinusoidal venules (31.1 +/- 3.3 microm) and the intersinusoidal distance (17.9+/-0.7 microm) also achieved normal values. The functional sinusoidal density amounted to 335 +/- 48/cm. The 6-week survival was nine of 11 with excellent liver function (Quick's value: 110% +/- 7.8%). The hepatobiliary radioisotope scanning with (99mTc) ethyl hepatic iminodiacetic acid (EHIDA) showed no significant differences between the native livers and grafts. The hepatocellular morphology was regular, apart from low-grade necroses in two grafts. The grafts' sinusoidal endothelial cells did not show any morphological changes. In group B, however, all rats died from AHF within 6 days. HALT with flow-regulated PVA achieved good results regarding microcirculation, morphology and function and can reliably bridge AHF.