Deletion variant of hepatocyte growth factor prolongs allograft survival after liver transplantation in rats.

BACKGROUND: Despite continued progress in the development of immunosuppressive agents, allograft rejection remains an important cause of morbidity and mortality after liver transplantation. We examined the effect of the deletion variant of hepatocyte growth factor (dHGF) on allograft rejection after liver transplantation. METHODS: Male Dark Agouti rats (RT1a) were selected as donors and male Lewis rats (RT1l) as recipients for a rejection model. The recipients were divided into 2 groups after orthotopic liver transplantation (OLTx): in the dHGF group dHGF was given intravenously twice a day (1 mg/kg/day) after OLTx, whereas in the control group vehicle buffer was given intravenously daily twice after OLTx. The survival period, serum chemistry studies, and histopathologic findings were then compared between the 2 groups. RESULTS: The mean survival period after OLTx in the dHGF group was significantly longer than that in the control group (21.4 +/- 1.3 days vs 11.8 +/- 0.4 days, P < .001). On the 10th posttransplant day the serum albumin level significantly improved in the dHGF group (P < .01), and the serum total bilirubin and aspartate aminotransferase levels were significantly lower in the dHGF group (P < .01 and P < .05, respectively). On the 10th posttransplant day a histologic examination revealed no apparent difference in the severity of rejection between the 2 groups. The number of proliferating cell nuclear antigen-positive hepatocytes in the dHGF group significantly increased (P < .01), whereas the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling-positive hepatocytes were significantly reduced in the dHGF group (P < .01) in comparison with those in the control group. CONCLUSION: dHGF has an antiapoptotic property as well as a proliferative and protective effect on hepatocytes under allograft rejection. dHGF might serve as a novel agent for reducing the harmful effects of hepatic allograft rejection in rats.     

Beneficial effect of preoperative mycophenolate mofetil in murine corneal transplantation

To investigate the effect of preoperative mycophenolate mofetil (MMF) on allograft survival in a murine corneal transplantation model. Corneal grafting was performed from Brown Norway to Lewis rats. Groups were divided as follows: Rats that received syngeneic or allogeneic grafts without therapy served as controls. MMF treatment was either started 7 days prior to transplantation and continued for 14 postoperative days (POD) or started at the day of corneal grafting until POD 14. MMF (20 mg/kg) administered postoperatively had no significant beneficial effect on corneal graft survival when compared with controls. However, the group receiving 40 mg/kg MMF postoperatively showed a statistically significant prolonged graft survival. A 1-week preoperative administration of 20 mg/kg MMF allowed superior graft survival. Priming the immune system of corneal transplant recipients preoperatively with MMF proved to be a beneficial therapeutic regimen for prolonging corneal allograft survival in rats.     

DA与Lewis大鼠品系组合建立大鼠肝移植排斥与耐受模型

目的 建立大鼠原位肝脏移植急性排斥与自然耐受模型.方法 采用近交系雄性DA大鼠与Lewis大鼠互为供受体,改良"二袖套"法建立大鼠原位肝脏移植(rat orthotopic liver trans-plantation,ROLT)模型84例.实验分为4组:排斥组(DA→Lewis,n=12),FK506处理排斥组[DA→Lewis,n=24,术后1～7 d用FK506 0.2 mg/(kg·d)灌胃],耐受组(Lewis→DA,n=24),同基因组(DA→DA,n=24).各组中随机取6例观察生存期,其余分别于术后7、14、28 d处死6例,收集外周血及肝脏标本.检测血清标本天冬氨酸转氨酶(aspartate aminotransferase,AST)、总胆红素(total bilirubin,TBIL)浓度,病理学检查移植物排斥反应程度.结果 排斥组中位生存时间(median surviv-al time,MST)为12 d,而FK506处理排斥组MST为76 d,较排斥组明显延长(vs排斥组,P<0.01).耐受组与同基因组的MST均>120 d.术后7 d,排斥组血清AST、BILI浓度均明显高于其余3组(P<0.05);术后14 d,FK506处理组、耐受组和同基因组血清AST、TBIL浓度无明显差异.术后28 d,FK506处理组血清AST、TBIL浓度较耐受组和同基因组明显升高(P相似文献   

Apoptosis and allograft rejection in the absence of CD8+ T cells.

BACKGROUND: The requirement for cytotoxic T lymphocytes during allograft rejection is controversial. We previously demonstrated that CD8+ T cells are not necessary for allograft rejection or for the induction of apoptosis in rat small intestinal transplantation. In this study, we examined the mechanisms of apoptosis and rejection after liver transplantation in the absence of CD8+ T cells. METHODS: Either Lewis or dark agouti rat liver grafts were transplanted into Lewis recipients to create syngeneic and allogeneic combinations. CD8+ T cells were depleted in an additional allogeneic group by treatment with OX-8 mAb on day -1 and day 1 after liver transplant. RESULTS: Apoptosis and rejection were observed in both the CD8+ T cell-depleted allogeneic and allogeneic grafts by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, and radiolabeled-annexin V in vivo imaging. Granzyme B and FasL were expressed in all allogeneic transplants, including those depleted of CD8+ T cells, indicating that a mononuclear cell other than a CD8+ T cell can be the source of these molecules during allograft rejection. Activation of the caspase cascade was detected in all rejecting allografts. Caspases 3, 8, and 9 were activated at similar significantly elevated levels in both allogeneic and CD8+ T cell-depleted liver grafts. CONCLUSION: These data indicate that in the absence of CD8+ T cells an alternative pathway, associated with granzyme B and FasL expression and activation of the caspase cascade, can mediate apoptosis and graft rejection.     

Telomerase activity in rat liver allografts

BACKGROUND: Telomerase activity in grafts may be involved in the alteration of cellular senescence after transplantation or its relevant immunological events. METHODS: At the age of 20 weeks, donor livers harvested from DA (RT1a) were orthotopically transplanted into PVG (RT1c) or LEW (RT1(1)) rats. Rats having undergone orthotopic liver transplantation (OLT; DA-PVG) naturally overcome rejection, whereas all OLT (DA-LEW) rats die from acute rejection within 14 days. Telomerase activity in liver allografts was measured at various intervals post OLT. RESULTS: At day 7 when the most severe rejection episode was observed in OLT (DA-LEW) and OLT (DA-PVG), the telomerase activity was significantly higher than in syngeneic OLT (DA-DA) rats, in which no rejection occurred. Telomerase activity in tolerogenic OLT (DA-PVG) livers remained elevated for at least 2 months. CONCLUSION: These results suggest that telomerase activity in allogeneic OLT livers may reflect regenerating hepatocytes or activation of lymphocytes and/or hematopoietic stem cells associated with rejection or tolerance.     

Assessment of 18F-FDG-leukocyte imaging to monitor rejection after pancreatic islet transplantation

AIM: We sought to investigate the feasibility of 18F-FDG-leukocyte imaging to detect islet rejection. METHODS: Two thousand Sprague-Dawley (SD, syngeneic group) or Lewis (allogeneic group) islet equivalents were intraportally injected into SD rat recipients. Four and 7 days after transplantation, 10(8) 18F-FDG-labeled splenocytes were injected into the jugular vein. Splenocytes were harvested from na?ve or sensitized (12 days after intraportal transplantation of 2000 Lewis IEQ) SD rats. Positron emission tomography (PET) imaging was started 5 minutes after splenocyte infusion and performed hourly for 4 hours. RESULTS: One hour after splenocyte injection, FDG was mainly detected in the heart and lungs. It was then further distributed to other organs, and from the second hour, the highest tracer concentration was located in the abdomen. Liver FDG uptake was similar between syngeneic, allogeneic, and sensitized allogeneic groups at 4 and 7 days after islet transplantation. DISCUSSION: No islet rejection was detected by 18F-FDG-leukocyte imaging. The amount of transplanted tissue was only few millilitres and the additional related inflammation in case of rejection is small and difficult to detect. The liver showed a relatively high spontaneous tracer uptake; the related background prevented detection of a potential increase in tracer uptake in cases of islet rejection.     

Protection of Reduced-Size Liver for Transplantation

The shortage of available organs for liver transplantation has motivated the development of new surgical techniques such as reduced-size liver transplantation. Ischemia-reperfusion (I/R) associated with liver transplantation impairs liver regeneration. Ischemic preconditioning is effective against I/R injury in clinical practice of liver tumour resections. The present study evaluated the effect of ischemic preconditioning on reduced-size liver for transplantation and attempted to identify the underlying protective mechanisms. Hepatic injury and regeneration (transaminases, proliferating cell nuclear antigen [PCNA] labeling index, and hepatocyte growth factor [HGF]) were assessed after reduced-size orthotopic liver transplantation (ROLT). Energy metabolism, oxidative stress, tumor necrosis factor-alpha (TNF) and interleukin-6 (IL-6) were examined as possible mechanisms involved in liver regeneration. Ischemic preconditioning reduced transaminase levels and increased HGF levels and the percentage of PCNA-positive hepatocytes after ROLT. This was associated with a decrease in oxidative stress following ROLT, whereas energy metabolism and hepatic IL-6 and TNF release were unchanged. The benefits of ischemic preconditioning on hepatic injury and liver regeneration could be mediated, at least partially by nitric oxide. These results suggest a new potential application of ischemic preconditioning in reduced-size liver transplantation.     

阻断B7/CD28共刺激通路抑制大鼠肝移植急性排斥反应的研究

目的:建立大鼠原位肝移植(ROLT)急性排斥反应模型,观察细胞毒淋巴细胞抗原4免疫球蛋白(CTLA-4Ig)在大鼠肝移植术后对共刺激分子B7-1/B7-2的影响及其抗排斥反应的作用。方法:采用"二袖套管"法先行建立DA-Lewis大鼠组合肝移植急性排斥反应模型,随机分为对照组(A组)与实验组(B组)两组,于肝移植术后48h每只受体大鼠腹腔内一次性注射CTLA-4Ig 75μg,分别于术后3、5、7和10d采用RT-PCR检测B7-1和B7-2 mRNA在两组肝脏组织中的表达情况,并同时观察其肝功能变化。结果:1)B7-1和B7-2 mRNA在A组高水平表达,而在B组表达明显降低(P<0.01);2)B组动物术后未见明显排斥反应,血清ALT、TBIL和DBIL水平明显低于对照组(P<0.01)。结论:移植术后应用CTLA-4Ig可以降低肝组织中B7-1和B7-2的表达;动态检测B7分子的表达有助于观察肝移植排斥反应的进程。     

Role of the bcl-2/bax pathway in hepatocyte apoptosis during acute rejection after rat liver transplantation

Abstract It is well established that hepatocytes undergo apoptotic cell death in the course of rejection of liver grafts. The present study was designed to investigate the role of the bcl-2/bax pathway in liver allograft tissue. Orthotopic liver transplantation was performed in three groups of rats: group 1, a syngeneic combination (Lewis to Lewis), group 2, an allogeneic combination (ACI to Lewis), and group 3, an allogeneic combination (ACI to Lewis) treated with 15-deoxyspergualin. The number of apoptotic cells identified by the TUNEL method in the grafted liver reflected the severity of acute rejection. In group 1, both bcl-2 mRNA and bax mRNA were expressed in trace amounts. In group 2, bcl-2 mRNA was slightly expressed while the expression of bax mRNA rose steadily. In group 3, bcl-2 mRNA expression levels remained similar to group 1, while bax expression levels exceeded those in group 1, but were less than in group 2. Expression of bcl-2 mRNA was stationary in comparison with expression of bax mRNA. Significantly higher levels of bax mRNA were expressed from day 4 in group 2 than in group 1 (on postoperative days 4, 6, and 8, P < 0.05, group 2 vs group 1). We also investigated bax protein and results consistent with the mRNA analysis data were obtained. These findings suggest that apoptotic cell death in liver allograft rejection is regulated, at least in part, by bax.     

Induction of Rejection After Small-for-Size Liver Transplantation: Size Matters

Background: Reduced-size liver transplantation is associated with liver regeneration. This study was designed to analyze the influence of graft size on liver rejection and liver regeneration. Methods: Reduced-size liver transplantations were performed in the rejecting ACI to Lewis and the graft acceptance BN to Lewis strain combination. The BN to Lewis control group was treated with the immunosuppressive drug FK506. Results: An accelerated liver rejection in the ACI to Lewis strain combination was found in small-for-size partial liver grafts. Graft weight to recipient liver weight ratio (GW/RLW) showed a positive correlation with survival time. In the BN to Lewis strain combination, lethal rejection was seen in small-for-size partial liver grafts. A critical immunologic GW/RLW of 33% was calculated. In rats dying from lethal rejection, GW/RLW and survival time showed a positive correlation. However, GW/RLW showed a negative correlation with hepatocellular proliferation. In regenerating livers, MHC II upregulation was also observed in the control group. All control animals survived small-for-size liver transplantation. Conclusions: The relative graft size seems to be a decisive factor influencing the kinetic of liver rejection and the induction of liver rejection. Relative critical immunologic liver mass was determined to be 33%.     

大鼠移植心脏的细胞凋亡及其与急性排斥反应的关系

目的 观察移植心脏的细胞凋亡现象及其与急性排斥反应的关系。方法 建立大鼠异位心脏移植模型,用ＨＥ梁色和原位末端标记（ＴＵＮＥＬ）技术检测移植心脏切片,进行排斥反应的病理分级,计算凋亡指数（ＡＩ）。结果 发生凋亡的细胞主要是心肌细胞,在各级排斥反应中均可见凋亡细胞存在,且ＡＩ与急性排斥发生的分级成正相关;各级的ＡＩ与０级（无排斥反应）比较,差异均有显著性。结论 细胞凋亡与移植心脏急性排斥反应的严重程     

Patchy distribution of rejection changes in small intestinal transplantation.

The aim of this study is to determine the distribution of histological changes of rejection in small intestinal transplantation. Thirty-nine rats were randomized into two groups: group I (n = 15), syngeneic transplants and group II (n = 24), allogeneic transplants. Grafts were excised and examined on days 2, 4, and 8 after transplantation. All grafts of the syngeneic group showed normal mucosa by day 4. However, by this time, all grafts of the allogeneic group demonstrated rejection changes with a patchy distribution in the mucosa. Therefore, with a biopsy from the stoma site there is a risk of missing early rejection.     

Magnetic resonance imaging of pancreatic islets in tolerance and rejection

BACKGROUND: We have recently described a magnetic resonance (MR) method for detection of rat pancreatic islets transplanted into the liver after labeling with superparamagnetic iron oxide nanoparticles. The aim of this work was to study whether this technique could be applicable over a longer period after transplantation and whether it could help to detect islet rejection. METHODS: Islets from Lewis and Wistar rats were cultured in the presence of iron oxide nanoparticles. Two thousand of Lewis (n=6) or Wistar (n=8) iron-labeled islets were transplanted into the portal vein of Lewis diabetic animals. Serial MR imaging of the liver were performed at 1, 2, 3, 4, 5, and 6 weeks. RESULTS: Although all allogeneic islets were rejected by 12 days, syngeneic animals remained normoglycemic throughout the study. At week 1, the labeled islets were visualized on MR scans as distinct hypointense spots homogeneously distributed in the liver. While their number declined only insignificantly in the syngeneic group, in the allogeneic group the number of spots gradually decreased until approximately 35% of their initial count. Although syngeneic islets showed a normal histology, the allogeneic islets were completely rejected. Iron particles, localized in macrophages, were detected only in the syngeneic islets and were absent in the rejected islet structures. In vitro incubation tests did not reveal any differences in insulin secretion between labeled and nonlabeled islets. CONCLUSIONS: MR imaging of iron-labeled pancreatic islets can be used for verification of the technical success of the transplantation procedure itself and for the detection of the decreasing relative islet mass due to rejection.     

Hepatic transplantation into sensitized recipients. Demonstration of hyperacute rejection

Hepatic transplantation into humorally presensitized patients has occasionally been performed without reported accelerated rejection. To study survival of orthotopic hepatic transplants in sensitized recipients a series of studies in rats were performed. Lewis rats sensitized by three successive skin grafts from fully allogeneic ACI strain donors then underwent orthotopic hepatic transplantation from ACI donors. Nine of ten recipients died within 4 hr with bleeding from the liver surface. By comparison, nine unsensitized recipients survived a mean of 10.7 +/- 0.5 days before succumbing with cellular rejection. Death of the sensitized recipients was not due to coagulopathy or technical failure. Histological studies of hyperacutely rejected livers demonstrated marked hemorrhage, edema, congestion, and necrosis within the hepatic parenchyma. There was a relative lack of cellular infiltrate compared with livers rejected by unsensitized recipients. Immunofluorescent staining showed IgG bound to perivascular tissues and sinusoids, and complement bound to perivascular tissue. Serum from presensitized, but not control, recipients showed a high titer of donor-specific, complement-dependent cytotoxic activity. It is concluded that hyperacute rejection of hepatic transplants can occur in sensitized rats and is mediated by a humoral mechanism. The immunohistopathology of this process is described.     

Regeneration of beta cells in the native pancreata after syngeneic and allogeneic pancreas transplantations in spontaneously type 2 diabetic Torii rats

BACKGROUND: We previously demonstrated that syngeneic pancreas transplantation has a potential to reverse diabetes even in a rat model of type 2 diabetes mellitus, namely Spontaneously Diabetic Torii (SDT; RT1a). The onset of diabetes was significantly delayed in the pancreas transplant recipients. We speculated that perfect diabetic control achieved by pancreas transplantation showed a beneficial effect on the native pancreata & recipients. MATERIALS AND METHODS: Twenty-five-week-old diabetic SDT rats were divided into 3 groups: untreated controls and syngeneic and allogeneic transplant recipients. We transplanted pancreaticoduodenal grafts from nondiabetic 10-week-old SDT rats and from 10-week-old allogeneic Dark Agouti (DA; RT1a) rats using daily administration of FK506. RESULTS: Untreated SDT rats showed disappearance of pancreatic and duodenal homeobox-1 (PDX-1) expression in the pancreas and a marked decrease in beta-cell mass. Among syngeneic and allogeneic pancreas transplant recipients, islet-like cell clusters were found in the native pancreata. The beta-cell mass at 40 weeks of age was significantly increased in the native pancreata of recipients compared with age-matched controls. Interestingly, we observed the reexpression of PDX-1 in the nuclei of islet-like cell clusters. CONCLUSIONS: Our results indicated the benefits of avoiding glucose toxicity by pancreas transplantation which induced PDX-1 expression in the native pancreata of type 2 diabetic recipients, resulting in regeneration of beta cells in the native pancreata.     

Energy metabolism during transplantation rejection

The effect of transplantation rejection on energy metabolism is unknown. In order to investigate energy expenditure changes in this setting, we used an eight-cage rat indirect calorimeter to measure resting energy expenditure (REE) in the well-defined model of rat cardiac transplantation. Preoperative baseline measurements of REE were performed on Lewis recipients of allogeneic (Wistar Furth) or syngeneic (Lewis) heterotopic abdominal cardiac grafts (80.3 +/- 3.3 kcal0.75/day). Postoperatively, REE was measured on days 1 through 10, 15, and 20. An abnormal REE was defined as a greater than 10% change from the preoperative value. All cardiac allografts were rejected on postoperative day 7, whereas syngeneic hearts contracted for more than 100 days. Both groups of animals had a hypermetabolic response to surgery on postoperative day 1 compared with preoperative values (93.0 +/- 7.6 kcal/kg0.75/day, p less than 0.01). On postoperative day 2, REE normalized to preoperative baseline values in the syngeneic group and remained unchanged for the duration of the study (80.4 +/- 1.0, p = 0.49). In the allogeneic group, on postoperative days 3 through 6 an abnormal REE was recorded in 22 of 28 measurements compared with only 3 of 16 in the syngeneic group (p less than 0.001). After transplant rejection, REE normalized to preoperative values in the allogeneic group. Characteristic changes in energy expenditure occur during transplantation rejection. These changes in REE preceded rejection in this animal model.     

Matrix Metalloproteinase 2 in Reduced‐Size Liver Transplantation: Beyond the Matrix

We studied the contribution of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) to the beneficial effects of preconditioning (PC) in reduced‐size orthotopic liver transplantation (ROLT). We also examined the role of c‐Jun N‐terminal kinase (JNK) and whether it regulates MMP2 in these conditions. Animals were subjected to ROLT with or without PC and pharmacological modulation, and liver tissue samples were then analyzed. We found that MMP2, but notMMP9, is involved in the beneficial effects of PC in ROLT. MMP2 reduced hepatic injury and enhanced liver regeneration. Moreover, inhibition of MMP2 in PC reduced animal survival after transplantation. JNK inhibition in the PC group decreased hepatic injury and enhanced liver regeneration. Furthermore, JNK upregulated MMP2 in PC. In addition, we showed that Tissue inhibitors of matrix metalloproteinases 2 (TIMP2) was also upregulated in PC and that JNK modulation also altered its levels in ROLT and PC. Our results open up new possibilities for therapeutic treatments to reduce I/R injury and increase liver regeneration after ROLT, which are the main limitations in living‐donor transplantation.     

Nitrosyl hemoglobin detected by near-infrared spectroscopy in rat liver allografts

Near-infrared spectroscopy (NIRS) is a noninvasive biomeasurement system with rays in the near-infrared region that possess high permeability to biological tissues. NIRS was applied to liver allografts undergoing rejection in rats treated with deoxyspergualin (DSG) or tacrolimus (FK506). The nitrosyl hemoglobin (Hb) levels detected in the liver grafts increased 3 days and 5 days after grafting in both allogeneic and syngeneic transplantation. The levels on day 8 remained high in the allogeneic graft, but markedly decreased in the syngeneic graft. Although the serum levels of nitrite and nitrate were extremely low 8 days after grafting in allografted recipients treated with DSG or FK506, the nitrosyl-Hb level in DSG-treated graft was much higher than that in FK506-treated graft. There was no significant difference in survival time between DSG-treated and FK506-treated recipients. In conclusion, DSG and FK506 have a different effect on NO production in allografted liver with ongoing rejection, and circulating nitrite and /nitrate levels do not reflect the local levels of NO in the graft. Received: 3 November 1998 Received after revision: 6 April 1999 Accepted: 14 July 1999     

DNA synthesis in hepatocytes during liver allograft rejection in rats

We have investigated DNA synthesis in hepatocytes after orthotopic liver transplantation in four rat combinations--DA into DA (isogeneic), DA into PVG (allogeneic, nonrejector), DA into BN (allogeneic, rejector), and DA into (BN X PVG)F1 (allogeneic, intermediate nonrejector). The methods used were assay of thymidine kinase activity in graft homogenate and staining of hepatocytes in liver sections by an antibromodeoxyuridine monoclonal antibody. Both demonstrated increased DNA synthesis in grafts in all combinations except isogeneic, and showed that its intensity and timing paralleled the occurrence of the rejection reaction. The significance of hepatocyte regeneration after liver grafting is discussed.