转染血管内皮生长因子基因神经干细胞移植对大鼠脑缺血损伤的修复作用

目的 探讨转染血管内皮生长因子（VEGF）基因神经干细胞移植对大鼠脑缺血损伤的修复作用。方法 建立大鼠大脑中动脉梗塞（tMCAO）模型，将tMCAO模型随机分为对照组、注射磷酸盐缓冲液（PBS液）的PBS液对照组、接受神经干细胞（NSCs）移植的NSCs组、接受转染VEGF基因的NSCs移植的NSCs-VEGF组，采用立体定向法将相应移植物注射到tMCAO模型的右侧纹状体缺血半暗区。各组移植后2、4、6、8、10、12周进行神经功能损害程度（NSS）评分；移植后7d，采用免疫荧光染色法观察NSCs-VEGF组移植细胞的VEGF基因表达情况；12周时，采用免疫荧光染色法追踪NSCs-VEGF组移植细胞向神经元方向分化情况，并同时行各组移植区周围血管内皮细胞半定量计数。结果 移植后2～12周，NSCs-VEG组的NSS评分均低于其它3组，第12周时的NSS评分与其它3组比较，差异有统计学意义（P〈0．01）；移植后7d，NSCs-VEGF组的移植细胞从移植点向周围迁徙，部分表达VEGF基因；移植后12周，NSCs-VEGF组部分移植细胞分化成神经元，其移植区血管内皮细胞数显著高于其它3组（P〈0．05）。结论 转染VEGF基因的神经干细胞移植对脑缺血所致的损伤具有一定的修复作用。     

转染血管内皮生长因子基因的小鼠NIH3T3细胞移植促进皮瓣早期血运重建的研究

目的探讨转染血管内皮生长因子（VEGF）基因的小鼠NIH3T3细胞移植对缺血皮瓣的血管新生和皮瓣存活率的影响。方法体外PcDNA3．1（-）／VEGF165质粒转染小鼠NIH3T3细胞,免疫组化方法检测小鼠NIH3T3细胞体外表达VEGF的情况,CM-DiI标记小鼠NIH3T3细胞。将小鼠随机分为3组：A组[PcDNA3．1（-）／VEGF165质粒转染的NIH3T3细胞移植]、B组（单纯NIH3T3细胞移植）、C组（单纯DMEM培养基注射）。每只小鼠背侧皮下按组分别注射细胞悬液和培养基,注射后酶联免疫吸附（ELISA）法连续检测大鼠血浆VEGF浓度,注射后第4天掀起一个蒂在尾侧的4．0cm×1．5cm的随意皮瓣。术后第7天分别观察皮瓣的存活率、血流灌注、皮瓣毛细血管密度、NIH3T3细胞在皮瓣内的分布和存活情况。结果转染VEGF165基因的小鼠NIH3T3细胞体外和体内检测均高表达VEGF165蛋白。A组的皮瓣存活率、毛细血管密度、血流灌注比值均显著高于另外两组（P〈0．05）。结论转染VEGF基因的小鼠NIH3T3细胞皮下移植可促进缺血皮瓣的血管新生,提高存活率。     

血管内皮生长因子促进大鼠的移植胰岛再血管化并提高其存活率

目的探讨血管内皮生长因子（VEGF）对大鼠的移植胰岛再血管化及对其存活率和功能的影响。方法构建质粒pIRES2-EGFP／VEGF165，以脂质体法在体外转染大鼠（供者）的血管内皮细胞。流式细胞术检测转染效率；免疫组织化学染色检测VEGF的表达。将糖尿病大鼠（受者）随机分为3组，每组10只。对照组：于肾被膜下单纯移植供者的300当量胰岛；实验组和空白转染组除移植供者的300当量胰岛外，分别加入供者的1×10^6个转染了质粒pIRES2-EGFP／vEGF165的血管内皮细胞和未经转染的正常血管内皮细胞。移植后监测受者的血糖及血清胰岛素水平。术后第14天，取受者肾脏，行HE染色及Insulin-6、VEGF和CD34免疫组织化学染色。结果血管内皮细胞中VEGFm的转染效率为13．06％。实验组供者的血管内皮细胞胞核和胞浆中均有VEGF表达。实验组受者于移植术后第3天血糖及胰岛素水平恢复正常；对照组和空白转染组虽有所改善，但未恢复到正常水平，与实验组相比，差异有统计学意义。实验组受者肾被膜下可见成团胰岛，Insulin-6免疫组织化学染色呈阳性，周围及内部有大量内皮细胞；VEGFm及CD34免疫组织化学染色呈阳性。对照组和空白转染组肾被膜下的细胞团中心细胞较少，部分被纤维组织代替，内部仅有少量CD34染色阳性的内皮细胞；Insulin-6免疫组织化学染色仅有少量细胞染成棕黄色；VEGF165免疫组织化学染色呈阴性。结论供者的胰岛与转染了VEGF165的血管内皮细胞共同移植给受者可以促进移植胰岛的再血管化，提高其存活率，并使其功能恢复正常。     

同时携带人血管内皮生长因子和血管生成素基因的内皮祖细胞血管再生研究

目的用腺相关病毒（adeno-associated virus,AAV）载体将人血管内皮生长因子165 （vascular endothelial growth factors,VEGF165）和血管生成素-1（angiopoietin-1,Angl）基因同时转入骨髓源性内皮祖细胞（endothelial progenitor cells,EPCs）中,观察外源基因的表达并评价其促血管再生的能力。方法用同时携带人VEGF165和Angl基因的AAV载体AAV2-hAngl/VEGF165转染体外培养的兔骨髓源EPCs,用RT-PCR和细胞免疫化学法检测外源基因的表达。实验用新西兰大白兔24只,制作成右下肢缺血模型,随机分成3组：PBS、EPC和EPC/AV组。造模后第10天,向缺血肌组织中分别注射PBS、EPCs和AAV2-hAngl/VEGF165转染的EPCs,用免疫组织化学法评价其血管再生效应。结果EPCs可高效地被AAV2-hAngl/VEGF165转染而表达Angl和VEGF165。细胞移植4周后,EPC/AV组存活的EPCs密度（283±137）/mm^-2明显高于EPC组（191±88）/mm^-2;EPC/AV组的毛细血管密度（856±212）/mm^-2明显高于EPC组（564±177/mm^-2）和PBS组（308±112）/mm^-2;α-SMA阳性血管密度（6.9±3.0）/mm^-2明显高于PBS组（3.6±1.8）/mm^-2,P〈0.05。结论AAV载体可同时将人VEGF165和Angl基因转入EPCs中,转染后的EPCs具有更强的促血管再生能力。     

人血管内皮细胞生长因子基因转染大鼠骨髓间充质干细胞对脂肪颗粒移植存活率的影响

目的 检测大鼠骨髓间充质干细胞(BMSCs)经人血管内皮细胞生长因子(VEGF165)基因转染后,对脂肪颗粒移植存活率的影响.方法　利用FuGENE HD介导VEGF165基因体外转染SD大鼠BMSCs,与取自SD大鼠的脂肪组织混合后移植于大鼠背部,类似方法设立未转染组及DMEM液空白对照组.检测脂肪组织存活率及再生血管密度.结果　转染组存在外源性基因和蛋白的表达,脂肪组织存活率及再生血管密度高于未转染组,且两者均高于对照组.结论　转染VEGF165基因的BMSCs具有更强的促血管再生作用,可提高游离移植脂肪的存活率.     

移植物转染血红素氧合酶-1基因抑制慢性移植物血管病

目的探讨移植物转染血红素氧合酶-1（HO-1）基因对慢性移植物血管病的影响。方法克隆HO-1基因，并构建含有HO-1基因的重组腺病毒载体（Ad-HO-1），实验分为4组：A组为同系移植对照组，供、受者均为Lewis大鼠，无特殊处理；B组为同种移植对照组，Lewis大鼠接受未经处理的BN大鼠胸主动脉移植；C组为同种移植空载体对照组，Lewis大鼠接受以空载体（不含HO-1基因）处理的BN大鼠的胸主动脉移植；D组为同种移植实验组，Lewis大鼠接受转染HO-1基因的BN大鼠的胸主动脉移植。于移植后60d取移植动脉，进行组织形态学观察，测量内膜厚度；免疫组化和逆转录聚合酶链反应检测HO-1在移植动脉中的表达。结果A组移植动脉形态正常；B组、C组移植动脉呈移植物血管病表现，血管内膜显著增厚，D组移植动脉呈内膜炎改变，内膜厚度与B组、C组相比，差异有统计学意义（P〈0．01）。免疫组化及RT-PCR检测显示，与A组、B组和C组相比，D组移植动脉可以检测到HO-1基因及其蛋白表达。结论在移植血管中预先转染HO-1基因，能明显缓解移植动脉的纤维化进程以及内膜的增生，对慢性排斥反应所致的移植物血管病具有抑制作用。     

低氧反应元件对低氧复氧状态下心肌细胞转染人血管内皮生长因子165基因表达的调控作用

目的研究9拷贝低氧反应元件（HRE）对低氧、复氧心肌细胞转染人血管内皮生长因子（hVEGF165）基因表达的调控作用。方法分离新生SD大鼠心肌细胞进行培养，将在HEK293T细胞进行包装后获得的腺相关病毒转染培养的心肌细胞。心肌细胞分为8组，采用无血清培养基，分别在低氧（氧浓度5％）、正常氧（氧浓度21％）条件进行培养．取低氧／复氧不同时段的心肌细胞或培养液，采用细胞免疫荧光法、ELISA法分别测定心肌细胞及培养液中hVEGF165蛋白表达情况；逆转录．聚合酶链反应（RT-PCR）法测定心肌细胞hvEGF165 mRNA的表达。结果病毒转染率约为87％；转基因低氧1组（A组）、2组（B组）及复氧1组（E组）培养液中hVEGF165蛋白含量显著升高（P〈0．01），细胞免疫荧光hVEGF165蛋白染色呈阳性；RT-PCR结果亦显示，转基因低氧1组（A组）、2组（B组）及复氧1组（E组）可见484bp目的条带。结论在低氧状态下，9拷贝HRE作为氧敏感调控开关，可促使心肌细胞转染的hVEGF165基因高度表达，而在复氧（正常氧浓度）状态下，hVEGF165因的表达即行中止。     

血管内皮生长因子基因转染血管内皮祖细胞治疗肢体缺血的实验研究

目的利用血管内皮生长因子（vascular endothelial growth factor,VEGF-165）基因转染体外诱导的血管内皮祖细胞（endothelial progenitor cells,EPCs）,并移植到下肢缺血的新西兰兔体内,观测其促进血管新生,改善肢体缺血的效果。方法（1）梯度离心法分离兔骨髓单个核细胞,然后用含有VEGF、bFGF、IGF-1的M199培养液诱导培养EPCs。并以免疫荧光、透射电镜等方法进行鉴定。（2）用携带VEGF165基因的腺病毒质粒（Adv-GFP-VEGF165）转染所培养的细胞,ELISA法检测上清液中VEGF蛋白的表达。（3）制作兔下肢缺血模型,并将其随机分为A、B、C 3组,分别移植EPCs、VEGF165基因转染后的EPCs、M199培养基,多种方法检测移植效果及局部整合情况。结果（1）自兔骨髓诱导出梭形贴壁细胞,免疫荧光及电镜检测证实为EPCs。（2）Adv-GFP-VEGF165成功转染EPCs,ELISA法检测转染VEGF165后的EPCs其上清液中VEGF蛋白浓度明显升高。（3）Brdu示踪显示移植细胞整合到缺血局部,CTA及免疫组化检查显示VEGF-165基因转染后的EPCs移植后其改善肢体缺血效果优于其他两组。结论VEGF基因转染EPCs后能改进EPCs质量,移植后促血管新生能力增强,其效果优于未转染组。     

腺病毒介导人VEGF_(165)和ANG-1双基因转染大鼠BMSCs及对其增殖的影响

[目的]探讨携带人血管内皮细胞生长因子165(VEGF165)和血管生成素-1(ANG-1)双基因的腺病毒表达载体pAd-VIA转染大鼠骨髓基质干细胞(BMSCs)的体外表达及对BMSCs增殖的影响。[方法]将本室构建的编码人VEGF165和ANG-1双基因的腺病毒质粒pAd-VIA在QBI-293A细胞内进行包装和扩增,体外转染大鼠BMSCs,通过绿色荧光蛋白(GFP)表达、Western-blotting、酶联免疫吸附分析(ELISA)方法检测外源基因的表达,利用MTT法检测MOI(multiplicity of infection)=50、100、200、400 pfu/cell不同浓度腺病毒转染后对BMSCs增殖活性的影响。[结果]重组腺病毒质粒pAd-VIA在QBI-293A细胞内成功包装和扩增,体外转染BMSCs后,有大量的GFP表达,Western-blotting检测显示,转染组与VEGF165和ANG-1抗体结合,在45 KD和14.4 KD左右出现印迹条带;ELISA结果显示:转染组第1、2、3 d,上清中的VEGF165浓度和ANG-1浓度持续增加,未转染组均未检测到外源基因的表达,差异...     

hVEGF165基因转染大鼠BMSCs的实验研究

目的构建携带hVEGF165基因的重组腺病毒载体pAdxsi-增强型绿色荧光蛋白(enhanced green fluorescent protein,EGFP)-hVEGF165,体外转染大鼠BMSCs,观察转染后hVEGF165的表达情况以及对BMSCs生长增殖的影响,为进行血管再生的基因治疗奠定实验基础。方法将hVEGF165从原始质粒切下连接到pShuttle-巨细胞病毒-EGFP重组穿梭载体,并转移至pAdxsi载体上,获得重组腺病毒载体质粒pAdxsi-EGFP-hVEGF165,进行酶切鉴定及基因测序。采用PacI限制性内切酶线性化pAdxsi-EGFP-hVEGF165,并转染人胚肾细胞HEK293,收获重组腺病毒,测定病毒滴度。贴壁法培养Wistar大鼠BMSCs,体外转染携带EGFP基因的重组腺病毒(pAdxsi-EGFP),荧光倒置相差显微镜及流式细胞术确定最佳病毒感染复数(multiplicities of infection,MOI)。依据最佳MOI转染pAdxsi-EGFP-hVEGF165至BMSCs,采用Western blot、RT-PCR及ELISA法检测转染后hVEGF165的表达;MTT法评价转染后BMSCs生长增殖情况。结果酶切鉴定及基因测序提示重组腺病毒载体质粒含有hVEGF165 cDNA;经多轮感染、扩增后,病毒滴度可达1×1010 pfu/mL。荧光倒置相差显微镜观察转染pAdxsi-EGFP后MOI为150 pfu/cell时转染效果最佳,流式细胞仪检测转染效率约88%。Western blot和RT-PCR检测示,pAdxsi-EGFP-hVEGF165转染BMSCs 48 h后在蛋白质和基因水平均可有效表达hVEGF165;ELISA检测示其含量在7 d达高峰,在20 d时仍有表达,1、3、5、7、9、11、13、15、20 d各时间点hVEGF165含量均显著高于EGFP基因转染组及未转染组(P<0.05)。MTT结果显示,各时间点转染pAdxsi-EGFP-hVEGF165的BMSCs与未转染组细胞的吸光度(A)值比较差异无统计学意义(P>0.05)。结论 BMSCs是一种较理想的基因载体细胞,成功制备的重组腺病毒载体质粒可在MOI值为150时将hVEGF165基因有效转染至BMSCs;转染后hVEGF165表达水平较高、持续时间较长,且对BMSCs的生长增殖无明显影响。     

Angiopoietin-1 production in islets improves islet engraftment and protects islets from cytokine-induced apoptosis

Successful islet transplantation depends on the infusion of sufficiently large quantities of islets, but only a small fraction of implanted islets become engrafted. The underlying mechanisms remain elusive. To probe the mechanism of islet revascularization, we determined the effect of angiopoietin-1 (Ang-1), a proangiogenic and antiapoptotic factor, on the survival, function, and revascularization of transplanted islets using a syngeneic model. Islets were transduced with adenoviruses expressing Ang-1 or control LacZ, followed by transplantation under the renal capsule. Diabetic mice receiving a marginal mass of 150 islets pretransduced with Ang-1 vector exhibited near normoglycemia posttransplantation. In contrast, diabetic mice receiving an equivalent islet mass pretransduced with control vector remained hyperglycemic. At 30 days posttransplantation, mice were killed and islet grafts retrieved for immunohistochemistry. Islet grafts with elevated Ang-1 production retained significantly increased microvascular density, improved glucose profiles, and increased glucose-stimulated insulin release. Cultured islets expressing Ang-1 displayed improved viability and enhanced glucose-stimulated insulin secretion in the presence of cytokines. In contrast, control islets exhibited increased apoptosis and diminished glucose-stimulated insulin release in response to cytokine treatment. These results indicate that Ang-1 confers a cytoprotective effect on islets, enhancing islet engraftment and preserving functional islet mass in transplants.     

Effect of hypoxia‐inducible VEGF gene expression on revascularization and graft function in mouse islet transplantation

For gene transfer strategies to improve islet engraftment, vascular endothelial growth factor (VEGF) expression should be regulated in a way that matches the transient nature of revascularization with simultaneously avoiding undesirable effects of overexpression. The aim of this study was to investigate the effects of hypoxia‐inducible VEGF gene transfer using the RTP801 promoter on islet grafts. We implanted pSV‐hVEGF transfected, pRTP801‐hVEGF transfected or nontransfected mouse islets under the kidney capsule of streptozotocin‐induced diabetic syngeneic mice. Human VEGF immunostaining of day 3 grafts revealed that the pRTP801‐hVEGF transfected group had higher hVEGF expression compared with the pSV‐hVEGF transfected group. BS‐1 staining of day 3 grafts from the pRTP801‐hVEGF transfected group showed the highest vascular density, which was comparable with day 6 grafts from the nontransfected group. In 360 islet equivalent (IEQ)‐transplantation which reverted hyperglycemia in all mice, the area under the curve of glucose levels during intraperitoneal glucose tolerance test 7 weeks post‐transplant was lower in mice transplanted with pRTP801‐hVEGF transfected grafts compared with mice transplanted with nontransfected grafts. In 220 IEQ‐transplantations, diabetic mice transplanted with pRTP801‐hVEGF islets became normoglycemic more rapidly compared with mice transplanted with pSV‐hVEGF or nontransfected islets, and diabetes reversal rate after 50 days was 90%, 68%, and 50%, respectively. In conclusion, our results indicate that regulated overexpression of hVEGF in a hypoxia‐inducible manner enhances islet vascular engraftment and preserves islet function overtime in transplants.     

Revascularization of transplanted pancreatic islets following culture with stimulators of angiogenesis

BACKGROUND: Insufficient revascularization of transplanted islets may result in chronic hypoxia and loss of islet function. This study investigated whether simple culture of islets with angiogenic substances before transplantation could improve graft revascularization. METHODS: Mouse islets were cultured with vascular endothelial growth factor (VEGF; 20 ng/ml), fibroblast growth factor 2 (FGF-2; 20 ng/ml) or matrix metalloproteinase 9 (MMP-9; 1 mug/ml). Thereafter, 250 islets were implanted beneath the renal capsule of syngeneic C57Bl/6 mice. One month posttransplantation, blood flow (laser-Doppler flowmetry), oxygen tension (Clark microelectrodes), and vascular density were measured and correlated to graft function. RESULTS: Treatment of islets with VEGF during culture caused islet blood vessels to dilate, whereas FGF-2 treatment induced endothelial cell proliferation. However, the number of capillaries in both cases decreased during culture. When investigated one month posttransplantation, both VEGF and FGF-2 pretreated islets had similar or worse vascular engraftment when compared to transplanted control islets. MMP-9 pretreatment of islets increased vascular density, blood flow and oxygen tension within the grafts. Animals receiving MMP-9 pretreated islets returned, however, more slowly to normoglycemia than control animals, and performed worse than controls in a glucose tolerance test one month posttransplantation. CONCLUSIONS: Treatment of islets during culture with VEGF or FGF-2 changed the islet vascular phenotype, but capillaries were still lost. Notably, the number of capillaries in the grafted islets one month posttransplantation was in all cases strikingly similar to that observed prior to transplantation. MMP-9 pretreatment of islets elicited an angiogenic response, which improved revascularization of the transplanted islets.     

Elevated vascular endothelial growth factor production in islets improves islet graft vascularization

Successful islet transplantation depends on the infusion of sufficiently large quantities of islets, of which only approximately 30% become stably engrafted. Rapid and adequate revascularization of transplanted islets is important for islet survival and function. Delayed and insufficient revascularization can deprive islets of oxygen and nutrients, resulting in islet cell death and early graft failure. To improve islet revascularization, we delivered human vascular endothelial growth factor (VEGF) cDNA to murine islets, followed by transplantation under the renal capsule in diabetic mice. Diabetic animals receiving a marginal mass of 300 islets that were pretransduced with a VEGF vector exhibited near normoglycemia. In contrast, diabetic mice receiving an equivalent number of islets that were transduced with a control vector remained hyperglycemic. Immunohistochemistry with anti-insulin and anti-CD31 antibodies revealed a relatively higher insulin content and greater degree of microvasculature in the VEGF vector-transduced islet grafts, which correlated with significantly improved blood glucose profiles and enhanced insulin secretion in response to glucose challenge in this group of diabetic recipient mice. These results demonstrate that VEGF production in islets stimulates graft angiogenesis and enhances islet revascularization. This mechanism might be explored as a novel strategy to accelerate islet revascularization and improve long-term survival of functional islet mass posttransplantation.     

Impaired revascularization of transplanted mouse pancreatic islets is chronic and glucose-independent

BACKGROUND: Pancreatic islets are avascular immediately after transplantation and depend on revascularization. Recently, the authors found decreased vascular density in mouse islets 1 month after implantation into nondiabetic recipients. This study investigated possible differences in revascularization between islets implanted into nondiabetic and diabetic recipients, and also evaluated changes in vascular density up to 6 months posttransplantation. METHODS: Islets were syngenically transplanted beneath the renal capsule of normoglycemic or alloxan-diabetic C57BL/6 mice. One to 6 months later, the animals were killed and the grafts removed. Histologic slides were prepared and stained with Bandeiraea simplicifolia. RESULTS: The vascular density in all transplanted islets was decreased compared with native islets. There were no differences in the islet graft vascular density between nondiabetic and diabetic animals. No improvement over time occurred. CONCLUSIONS: The vascular density is decreased in islets implanted to cure diabetic recipients. No improvement occurs in transplanted islets after 1 month posttransplantation.     

Phosphate depletion impairs insulin secretion by pancreatic islets.

Phosphate depletion (PD) is associated with resistance to the peripheral action of insulin and with glucose intolerance. However, data on the effect of PD on insulin secretion are not consistent, and were derived indirectly by measurements of blood levels of insulin during intravenous glucose tolerance test (IVGTT) or with hyperglycemic clamp technique. Direct evidence for an effect of PD on insulin secretion by pancreatic islets is not available, and the potential mechanisms through which PD may affect insulin secretion are not known. We performed IVGTT, examined in vitro insulin secretion by pancreatic islets, and evaluated various factors involved in insulin secretion in PD and pair weighed (PW) rats. PD animals had fasting hyperglycemia and normal plasma insulin levels, and displayed abnormal IVGTT as compared to PW rats. Both initial and late phases of D-glucose-induced insulin secretion from islets were markedly and significantly (P less than 0.01) lower than from islets of PW rats. In contrast, D-glyceraldehyde-induced insulin release in PD rats was similar to that of PW rats. [H3]2-deoxyglucose uptake by islets and their cyclic AMP content after exposure to D-glucose, D-glyceraldehyde or forskolin were not different among the two groups of animals. Insulin content in PD islets was modestly but significantly (P less than 0.01) higher than PW islets. In PD islets, ATP content and the ATP/ADP ratio at basal state and after incubation with 16.7 mM D-glucose were significantly (P less than 0.01) lower and resting cytosolic calcium was significantly (P less than 0.01) higher than in PW islets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modification of allograft immunogenicity in perinatal islets isolated and purified in vitro

Perinatal rat islets of Langerhans, isolated and cultured in vitro, were examined following long-term allotransplantation across a major histocompatibility barrier in nonimmunosuppressed recipients. Islets were isolated to varying degrees of purity without the use of collagenase digestion. Newborn bovine serum was a component of the incubation medium and the atmosphere during culture was air: 5% CO2. Islets transplanted without rigorous purification were fully rejected by 14 days posttransplantation. However, if islets were maintained in subculture, permitting their subsequent meticulous purification, no evidence of rejection was observed after 45 days at the kidney subcapsular site. Grafts consisted of morphologically intact islets. The three major endocrine cell types of the islet were identified by immunocytochemical localization of insulin, glucagon, and somatostatin. These results demonstrate that perinatal islets can exhibit altered immunogenicity, as evidenced by prolonged allograft survival, when isolated and purified by the nonenzymic in vitro method.     

Allotransplantation of rat islets into the cisterna magna of streptozotocin-induced diabetic rats.

Islets were isolated from the pancreata of Sprague-Dawley rats and transplanted into streptozotocin-induced diabetic outbred Wistar rats. The effect of transplantation of islets into the cisterna magna on the diabetic state of the recipients was compared with that of the conventional transplantation of islets into liver via the portal vein. After successful intraportal (IP) transplantation, rejection took place between days 7 and 15 in all diabetic recipients. All of the eleven rats surviving after stereotaxic implantation of islets into the cisterna magna returned to normoglycemia within 7 days after transplantation. Nine of the recipients with intra-cisterna magna (IM) islet allografts were still normoglycemic at 210 days after transplantation. The glucose disappearance rate of the IM transplant rats was slower than that of the IP transplant rats, and blood glucose returned to the normal basal level within 5 hr following glucose administration. Although the insulin levels were almost undetectable in cerebrospinal fluid before IM transplantation, the insulin levels were markedly increased after IM transplantation and twice as great in CSF than blood. Thus, these findings indicate that the cisterna magna can serve as an immunologically privileged site for implantation of allogeneic pancreatic islets, and islets in CSF can regulate and maintain normal glucose homeostasis via secretion of insulin across the blood-brain barrier.     

Transplantation of pancreatic islets from hypothalamic obese rats corrects hyperglycemia of diabetic rats

Pancreatic islets isolated from adult obese rats, obtained by neonatal treatment with monosodium L-glutamate (MSG), oversecrete insulin stimulated by glucose concentration. Whereas adult MSG obese rats are hyperinsulinemic, their pancreatic islets still secrete insulin after high glucose demand. This is crucial so that the animals do not become hyperglycemic. Islets from MSG obese rats were implanted in diabetic donor rats so that the capacity of islets in regulating blood glucose concentration could be evaluated. Hyperglycemic (glucose 22 to 34 mmol/L) rats obtained with streptozotocin (STZ) treatment were used as recipients. Islet donors consisted of control adult and MSG obese rats. Only 600 islets were transplanted via the portal vein to diabetic rats. During 4 days after the transplant, fed blood glucose was monitored. After 12 hours of fasting the rats were killed; their blood samples were used to measure glucose and insulin concentration; retroperitoneal fat pads were isolated and weighed to estimate body fat. Transplanted islets from MSG obese rats decreased of fed glucose levels by 34% in diabetic rats (P < .05); however, glucose levels still remained twofold higher than those of intact controls (P < .05). Similar to MSG islets, islets grafts from control rats provoked the same effects in diabetic rats. High fasting blood glucose and low insulin levels of diabetic rats were corrected by islet grafts. Transplantations were able to recover 40% of fat in diabetic rats. The results demonstrated that islets from MSG obese rats may regulate blood glucose concentrations in diabetic rats, and suggesting that their function was not permanently altered by the onset of obesity.     

Survival and function of syngeneic rat islet grafts placed within the thymus versus under the kidney capsule

The role of the thymus in the ongoing acquisition of tolerance to self antigens has made it an attractive site for islet transplantation. Several studies have reported survival of rodent islet allografts in the thymus without requiring the long-term use of immunosuppressive agents; however, the degree of glucose homeostasis in the intrathymic islet transplant recipients has not been examined. We transplanted 500, 1000, or 2000 syngeneic islets into the thymus of streptozotocin-induced diabetic Wistar-Furth rats, and compared the metabolic response of these recipients with animals receiving 2000 syngeneic islets under the kidney capsule. Three of four recipients which received 2000 islets under the kidney capsule achieved normoglycemia (≤8.4 mmol/L) within 1 wk and all animals became normoglycemic within 2 wk posttransplantation. In contrast, intrathymic implantation of 2000 islets induced normoglycemia in only one of six recipients during the same time interval, and when this number was reduced to 1000 or 500 islets, none of the recipients (n = 6) normalized within 1 wk posttransplantation. Animals that received an intrathymic transplant were glucose intolerant compared to normal controls and animals with subcapsular islet transplant. Removal of the graft-bearing organs resulted in hyperglycemia in all cases, and examination of the grafts revealed the presence of numerous well-granulated insulincontaining cells in both sites. The cellular insulin content of the subcapsular grafts (67.4 ± 12.1 μg; n = 4) was significantly higher (p ≤0.05) than what was extracted from intrathymic grafts (9.5 ± 1.2 μg from 1000 islets; n = 3 and 20.0 ± 4.6 μg from 2000 islets; n = 3). We conclude that 2000 syngeneic islets implanted either in the thymus or beneath the kidney capsule can normalize hyperglycemia in streptozotocin-diabetic rats; however, normal glucose tolerance was not established in intrathymic islet recipients, suggesting that a higher number of islets may be necessary to achieve normal glucose homeostasis.