海藻酸-壳聚糖-聚乙烯乙二醇微囊化异种胰岛移植治疗小鼠糖尿病

目的比较海藻酸-聚赖氨酸-海藻酸微囊化(APA)大鼠胰岛和海藻酸-壳聚糖-聚乙烯乙二醇微囊化(ACP)大鼠胰岛移植对小鼠糖尿病的治疗作用.方法链脲霉素220 mg/kg体重腹腔内注射制作小鼠糖尿病动物模型.成模后分成APA微囊组、ACP微囊组和未微囊化胰岛组,每只小鼠腹腔内分别植入200个相应胰岛,检测监测移植前后小鼠的血糖.结果移植后第1天,3组小鼠血糖均较移植前明显降低.未微囊化胰岛移植组小鼠术后第2天血糖均恢复到术前水平;APA微囊组和ACP微囊组小鼠血糖分别维持正常(57.00±14.61)d和(41.67±16.73)d,此两组间差异无显著性(P＞0.05),但均较未微囊化胰岛移植组明显延长(P＜0.05).结论 ACP微囊与APA微囊一样具有免疫隔离作用;ACP微囊化异种胰岛移植可纠正小鼠糖尿病.     

BPA微囊与APA微囊机械强度和生物相容性的比较研究

目的 比较海藻酸钡-多聚赖氨酸-海藻酸(BPA)微囊与海藻酸-多聚赖氨酸-海藻酸(APA)微囊的生物相容性和机械强度的生物物理特性.方法 用静电微囊发生仪制备BPA和APA微囊,通过机械振荡法和肌肉下移植来检测微囊的机械强度.通过微囊大鼠腹腔移植来观察BPA和APA微囊的生物相容性.结果 机械振荡48h后APA微囊的破损率为4.3%,BPA微囊仅为1.5%;肌肉下移植1个月后,组织切片H&E染色显示,APA和BPA微囊均保持完整,仅有轻度纤维化包裹;腹腔移植4、8和10周后,从大鼠腹腔内取出的微囊中95%～98%为结构完整,呈圆形,表面光滑,光镜下无明显的结缔组织包绕.结论 所制备的BPA微囊的生物相容性河机械强度优于APA微囊.     

血红素氧合酶-1基因转染对大鼠胰岛培养的影响

目的 探讨血红素氧合酶-1基因（HO-1）转染对培养的大鼠胰岛功能的影响。方法 用携带人HO-1基因和增强型绿色荧光蛋白基因（EGFP）的腺病毒载体转染大鼠胰岛，转染后48h，以EGFP及人HO-1蛋白的表达来确定转染结果，放免法测定各组胰岛在低糖（2．8mmol／L）、高糖（16．7mmol／L）刺激下胰岛素释放量，并计算刺激指数（SI）。结果 大鼠胰岛培养7d后，其低糖、高糖刺激下胰岛素释放量明显低于新鲜胰岛[（4．57±0．40比（6．47±0．55）mIU／L／30IEQ，（9．63±0．71）比（14．93±1．17）mIU／L／30IEQ，P〈0．05]；培养7d的各组胰岛在低糖刺激时胰岛素释放量差异无统计学意义（P〉0．05），但HO-1组胰岛在高糖刺激时胰岛素释放量明显高于EG．FP组和对照组[（12．50±2．17）mIU／L／30IEQ，（8．87±0．65）mIU／L／30IEQ，（9．63±0．71）mlU／L／30IEQ，P〈0．05]；HO-1组SI也高于EGFP组和对照组[（2．21±0．02），（2．08±0．05），（2．11±0．03），P〈0．05]。结论 HO-1基因转染能对体外培养的大鼠胰岛功能起到保护作用。     

微囊化异种甲状旁腺组织移植的研究

目的探讨微囊化异种甲状旁腺(PTG)组织移植对Wistar大鼠甲状旁腺功能低下的治疗作用及微囊的通透性。方法 40只去甲状旁腺Wistar大鼠随机分为微囊组、非微囊组、空囊组、空白对照组。用海藻酸-钡交联微囊包裹兔甲状旁腺组织,移植至Wistar大鼠肾包囊。移植后每隔2周取血测血钙,移植后第16周取移植物进行透射电镜检查及T淋巴细胞、大鼠IgG抗体的免疫组织化学染色。结果微囊组移植后第4周血清钙由(1．62±0．04)mmol／L恢复至正常水平 (2．2～2．6)mmol／L,9例维持至观察期结束(P<0．01),非微囊组、空囊组及空白对照组血清钙差异无统计学意义(P>0．05)。第16周取出移植物检测显示移植物活性良好,微囊周围可见较多T 淋巴细胞浸润,囊壁及囊内IgG抗体染色阳性。结论海藻酸-钡交联微囊可对甲状旁腺组织起到有效的保护作用,使甲状旁腺组织较长时间存活并发挥正常功能。但海藻酸-钡交联微囊并未减轻受体免疫排斥反应的激活且未有效的免疫隔离IgG抗体。     

微囊化大鼠胰岛异种移植的实验研究

目的　通过动物实验明确微囊化胰岛是否具有免疫隔离作用。方法　SD大鼠胰腺原位消化 ,Ficoll间断密度梯度离心法纯化、分离胰岛 ,气流吹喷制作海藻酸钠 /聚赖氨酸 /海藻酸钠(APA)微囊化大鼠胰岛 ,比较微囊化与未微囊化胰岛的胰岛素释放试验 ;将微囊化 (实验组 )与未微囊化 (对照组 )大鼠胰岛植入链脲佐菌素 (STZ)诱导的I型糖尿病小鼠中 ,作两组间血糖正常持续时间比较。结果　实验组与对照组的胰岛素释放试验差异无显著性 (P >0 .0 5 ) ;实验组血糖正常持续时间为 2 3～ 6 5d(平均 48d) ,对照组为 3～ 6d(平均 5d) ,两组差异有极显著性 (P <0 .0 1)。已排斥的实验组小鼠腹腔灌洗发现部分微囊化胰岛存活 ,部分已坏死 ,但微囊膜皆完整 ,囊壁无纤维化。结论　微囊具有良好的免疫隔离作用 ,可使胰岛移植物存活时间明显延长。同时推测微囊内移植物死亡与细胞因子、自由基作用或营养不足等有关。     

肝细胞海藻酸钡微囊生物性能的研究

目的　研究肝细胞海藻酸钡微囊的生物学性能。方法　大鼠肝细胞微囊化后移植于腹腔内 ,1个月后取出行组织学检查。结果　不含肝细胞的空囊移植组微囊大多保持良好的形状 ,囊壁光滑、完整 ,囊外无纤维化反应 ,回收率为 ( 89± 2 3) %。肝细胞微囊大部分呈游离状态 ,部分囊外有一薄层纤维层附着 ,回收率为 ( 78± 2 1) % ;囊内细胞存活率由移植前的 ( 91± 16 ) %降至 ( 79±13) %。结论　肝细胞海藻酸钡微囊的生物相容性及机械稳定性较好 ,但免疫源性有待进一步提高。     

原发性醛固酮增多症(附507例报告)

目的提高原发性醛固酮增多症(PA)的诊治水平。方法回顾性总结507例PA的诊治资料。结果产生醛固酮的肾上腺腺瘤(APA)患者血钾为(2.35±0.53)mmol/L,血和24h尿醛固酮分别为(1027.67±531.84)pmol/L、(69.25±43.77)mmol/L,立位血浆醛固酮增加值为(-17.17±483.37)pmol/L。特发性醛固酮增多症(IHA)血钾为(2.94±0.55)mmol/L,血和24h尿醛固酮分别为(781.14±310.24)pmol/L、(37.12±9.99)mmol/L,立位血浆醛固酮增加值为(170.36±303.59)pmol/L。B超和CT对APA的诊断符合率分别为83.9%和93.1%,IHA主要显示双侧肾上腺增大或小结节变化。肾上腺皮质癌(APC)的特点是皮质醇和去氢异雄酮明显增高,且瘤体直径>5cm。结论APA血和尿醛固酮明显高于IHA,APA血钾明显低于IHA,体位试验、B超和CT能帮助确诊APA。单发APA合并肾上腺萎缩应行肾上腺部分切除,多发APA或合并肾上腺增生者应行患侧肾上腺全切。     

微囊化新生猪胰岛细胞体外培养的研究

海藻酸钠-聚赖氨酸-海藻酸钠生物微胶囊(简称APA微胶囊),具有生物半透膜性,葡萄糖与胰岛素能通过该膜,而抗体与淋巴细胞则不能,避免了机体对移植物的排异反应,使移植物体内生存时间延长。此项技术是目前最具前景的免疫隔离技术。本文利用胶元酶消化和体外培养的方法制备新生猪胰岛细胞,用微囊包膜技术,将胰岛细胞包裹,体外培养。放射免疫法测定培养液中胰岛素的含量,比较微囊化及未微囊化新生猪胰岛细胞胰岛素分泌能力和胰岛素刺激释放试验、组织学检查。证实二者差异不显著,均具有良好的生物活性。胰岛细胞团在微囊内分化发育良好,并不断分泌胰岛素,囊内外均未见纤维细胞生长。APA微囊及其制备技术对胰岛细胞活性和分泌功能无明显影响。微囊包膜后胰岛细胞的活性和分泌功能良好,微囊包膜新生猪将为临床异种移植提供良好的供体来源。     

微囊化胰岛与滋养细胞对鼠胰岛功能和活性的影响

目的 研究微囊化滋养细胞对胰岛功能和活性的影响.方法 对单独、分别和联合微囊组胰岛素含量及不同条件(5.6、16.7mmol/L葡萄糖、16.7mmol/L葡萄糖+10mmol/L茶碱)下胰岛素释放试验进行检测;监测3组(每组8例)小鼠平均空腹血糖(FIG),将胰岛的功能和活性进行对照.结果 体外,联合组胰岛素含量(288±25)、(292±29)、(203±21)mmol/L及在胰岛素释放试验中的反应性(306±25)、(335±26)、(378±32)mmol/L均好于另两组,差异有统计学意义(P<0.01);移植后,单独组(27.3 d)、分别组(30.5 d)维持FPG<6.0的时间明显少于联合组(66.8 d),联合组恢复高血糖状态的平均时间为91.7 d,差异有统计学意义(P<0.01).结论 滋养细胞与胰岛联合微囊化能够改善胰岛的存活状况,提高其生物活性,并维持其分泌功能.     

转化生长因子-β1对大鼠同种胰岛移植物的影响

目的　研究转化生长因子 β1 (TGF β1 )对大鼠同种胰岛移植物体内外的内分泌功能及存活的影响。方法　构建TGF β1的真核表达载体 pcDNA3 TGF ,并将其转染纯化后的Wistar大鼠胰岛 ,逆转录 聚合酶链式反应 (RT PCR)检测TGF β1和大鼠胰岛素 (Ins1 )在实验组和对照组胰岛中的表达 ,放射免疫法 (RIA)检测体外培养液中的胰岛素含量 ;链脲霉素 (STZ) 60mg/kg体重腹腔内注射制作SD大鼠模型 ,分别将实验组和空白对照组Wistar胰岛移植到受体SD大鼠的肾包囊下 ,观察其在体内逆转糖尿病的作用以及作用时间的长短 ,并检测受体大鼠的糖耐量。结果　实验组胰岛有TGF β1和Ins1的表达 ,而对照组仅有Ins1的表达 ;实验组体外培养液中的胰岛素含量在基础相和刺激相分别为 (3 .86± 1 .2 4 ) μg/L和 (8.43± 1 .59) μg/L ,对照组体外培养液中的胰岛素含量在基础相和刺激相分别为 (4.1 3± 1 .45) μg/L和 (8.95± 1 .74) μg/L ,组间差异无显著性 (P>0 .0 5) ,而组内差异有显著性 (P <0 .0 5) ;实验组平均正常血糖维持时间 (2 6 .8± 2 .9)d比对照组的 (1 3 .2± 4 .5)d显著延长。对照组糖耐量曲线均明显高于实验组。结论　TGF β1对胰岛移植物的内分泌功能无损害作用 ,但是可以延长胰岛移植物体内存活时间     

Prolonged glucose normalization of streptozotocin-induced diabetic mice by transplantation of rat islets coencapsulated with crosslinked hemoglobin

BACKGROUND: Facilitated oxygen transport by crosslinked hemoglobin (Hb-C) in islet microcapsules may promote transplanted graft function by improving islet functionality and viability. METHODS: This study investigated the in vivo efficacy of Hb-C as an oxygen carrier on the functionality and viability of microencapsulated rat islets. Hb-C by poly(ethylene glycol) was introduced into rat islet microcapsules (alginate-poly[L-lysine]-alginate microcapsule), and 500 suboptimal encapsulated islets were xenotransplanted into each streptozotocin-induced diabetic BALB/c mouse. The graft efficacy over time was evaluated by measuring nonfasting blood glucose level, body weight, and glucose tolerance. RESULTS: Mice that received Hb-C-containing microcapsules maintained normoglycemia for at least 8 weeks with normal glucose clearance, determined by intraperitoneal glucose tolerance test. However, the mice that received the conventional control islet microcapsule (without Hb-C) transplant showed graft failure in 4 weeks, exhibited by hyperglycemia, weight loss, and deteriorated glucose tolerance. Severe central necrosis of retrieved islets was observed for the control islet capsule graft after 8 weeks. CONCLUSION: The present study revealed that the incorporation of Hb-C in islet microcapsules promotes graft function for a longer period of time than the conventional islet capsules. Therefore, Hb-C coencapsulation is a potential approach for prolonging graft function of islet microcapsules and reducing the number of islets required for normoglycemia.     

海藻酸钠-氯化钡微囊对大鼠胰岛体外胰岛素分泌功能的影响

目的　观察海藻酸钠 -氯化钡微囊对大鼠胰岛体外胰岛素分泌功能有无影响。方法　以海藻酸钠和氯化钡为材料 ,采用气体吹喷制囊法将新鲜分离纯化的大鼠胰岛制成微囊化胰岛 ,取空微囊、微囊化大鼠胰岛与未微囊化大鼠胰岛各 5 0 0只 ,分为 10份 ,置于培养板中培养 ,用放免法测定并比较第 2、4、6 d培养液中基础胰岛素浓度。结果　空微囊组第 2、4、6 d的基础胰岛素平均浓度均为 0 nm ol/ 1/ 5 0 ,微囊化大鼠胰岛组第 2、4、6 d的基础胰岛素平均浓度为 5 .179、5 .80 6、5 .5 5 8nm ol/ 1/5 0只 ,未微囊化大鼠胰岛组第 2、4、6 d的基础胰岛素平均浓度为 5 .4 4 1、6 .0 80、5 .4 6 8nmol/ 1/ 5 0只 ,后两者差异无显著性意义 (P>0 .0 5 )。结论　海藻酸钠 -氯化钡微囊对大鼠胰岛体外胰岛素分泌功能无影响     

Isolation of porcine pancreatic islets for xenotransplantation studies: Effects of low collagenase digestion temperatures

Abstract: Islets of Langerhans were isolated from porcine pancreata by a modification of our previously described method. The modification involved the use of a low temperature of collagenase digestion (30°C) during the process of islet isolation. The resulting islets were then evaluated in vitro and in vivo and compared to islets isolated at the regular 37°C temperature.
The islets produced at the low temperature were more compact compared to the control islets. In the dextran density gradient these islets were deposited at the interface of the 1.060 and 1.068 g/ml density bands as compared to 1.050 and 1.060 g/ml for the control islets. In addition, the experimental islets contained a higher proportion of compact, unfragmented islets (68%) compared to the regular islets (55%), and their uptake of the dithizone stain was considerably slower than with the control islets. All ten batches of freshly isolated microencapsulated islets produced at both temperatures responded to the glucose stimulation. After 4 weeks of in vitro culture the islets of both groups microencapsulated in alginate-polylysine-alginate (APA) microcapsules still retained glucose responsiveness, with the experimental islets demonstrating significantly higher responsiveness to the high glucose (16.7 mM) and 0.1 mM IB MX stimulation. The morphology of unencapsulated islets in the experimental group following 4 weeks of in vitro culture indicates much firmer islet structure compared to the control islets. In addition, the unencapsulated experimental islets following the 4 week culture were still found to have secreted insulin when exposed to glucose. In transplantation studies both the experimental and the control islets normalized diabetic hyperglycemia in diabetic mice in a comparable fashion. In general, the low temperature digestion results in superior islets in terms of their morphology, viability, and physiological function.     

Indefinite islet protection from autoimmune destruction in nonobese diabetic mice by agarose microencapsulation without immunosuppression

BACKGROUND: The recurrence of autoimmunity and allograft rejection act as major barriers to the widespread use of islet transplantation as a cure for type 1 diabetes. The aim of this study was to evaluate the feasibility of immunoisolation by use of an agarose microcapsule to prevent autoimmune recurrence after islet transplantation. METHODS: Highly purified islets were isolated from 6- to 8-week-old prediabetic male nonobese diabetic (NOD) mice and microencapsulated in 5% agarose hydrogel as a semipermeable membrane. Islet function was evaluated by a syngeneic islet transplantation model, in which islets were transplanted into spontaneously diabetic NOD mice. RESULTS: The nonencapsulated islet grafts were destroyed and diabetes recurred within 2 weeks after transplantation in all 12 mice. In contrast, 13 of the 16 mice that underwent transplantation with microencapsulated islets maintained normoglycemia for more than 100 days after islet transplantation. Histologic examination of the nonencapsulated islet grafts showed massive mononuclear cellular infiltration with beta-cell destruction. In contrast, the microencapsulated islets showed well-granulated beta cells with no mononuclear cellular infiltration around the microcapsules or in the accompanying blood capillaries between the microcapsules. CONCLUSIONS: Agarose microcapsules were able to completely protect NOD islet isografts from autoimmune destruction in the syngeneic islet transplantation model.     

微囊包膜新生猪胰岛移植逆转糖尿病大鼠甲状腺形态学改变

目的探讨糖尿病大鼠胰岛移植后的甲状腺形态学的变化。方法给用链脲霉素所致的糖尿病大鼠腹腔内移植微囊包膜的新生猪胰岛８００个。术后３个月将动物处死,取甲状腺切片观察。结果动物处死前对照组及移植组的血糖水平分别为（４．８７±０．４７）ｍｍｏｌ／Ｌ和（６．４４±１．８２）ｍｍｏｌ／Ｌ,糖尿病组为（１６．１２±１．４７）ｍｍｏｌ／Ｌ,移植组与对照组比较,差异不显著（Ｐ＞０．０５）,糖尿病组与对照组比较,差异显著（Ｐ＜０．００１）;甲状腺滤泡腔内胶质的面积,移植组、糖尿病组分别与对照组比较,差异不显著,但甲状腺滤泡上皮细胞的高度,糖尿病组与对照组相比,差异显著（Ｐ＜０．００１）,而移植组与对照组相比,差异不显著（Ｐ＞０．０５）。结论胰岛移植后若受体的血糖控制良好,其甲状腺滤泡上皮细胞的形态改变可以逆转,这可能是纠正糖尿病时甲状腺分泌功能低下的重要因素之一。     

微囊化大鼠胰岛异种移植治疗小鼠实验性糖尿病的研究

目的 研究海藻酸钠－聚赖氨酸－海藻酸钠包裹胰岛进行移植的效果。方法 将Ｗｉｓｔａｒ大鼠的胰腺先行胶原酶胰管内注射消化,然后分离,纯化,所得胰岛经培养后制成微囊包膜的胰岛,微囊直径为０．４￣０．５ｍｍ,每个微囊内包１个胰岛。     

Survival prolongation of microencapsulated allogeneic islet by nanosized nordihydroguaiaretic acid

Immunoisolation such as alginate-poly-L-lysine-alginate (APA) microencapsulation may protect entrapped islet graft cells from destruction by cellular and humoral immunities, but cannot avoid aggregation of macrophages and fibroblasts around microcapsules, which has been known to cause late dysfunction. Nordihydroguaiaretic acid (NDGA) is a lipoxygenase inhibitor that prevents the activation and chemotaxis of macrophages. In this study, we used the dialysis method without surfactant to prepare poly (DL-lactide-co-glycolide) (PLGA) nanoparticles to entrap NDGA. We determined the formulation conditions suitable for sustained release when coencapsulated with the islets. Nanoparticle sizes of 0.2-0.3 microm were suitable for sustained release in electromagnetic driven APA microcapsules. In the toxicity study, we coincubated islets with PLGA-NDGA nanoparticles in vitro for 2 and 4 weeks. The glucose stimulated insulin secretion and insulin contents of islets were not influenced significantly. To test whether nanosized NDGA provides extra protection for APA islets, about 160-200 allogeneic islets of C57BL/6 mice were either encapsulated alone using APA or coencapsulated with PLGA-NDGA. At 2 and 4 weeks after implantation into the peritoneal cavities of healthy BALB/c mice, the intraperitoneal islet grafts were recovered using lavage. Mice that received islets of APA-PLGA-NDGA preparations showed a higher recovery rate of functioning grafts than those that received islets prepared using APA alone (10.1%, n = 4 vs 5.2%, n = 3). In conclusion, nanosized NDGA prolonged the graft survival of APA microencapsulated allogeneic islets.     

Biodritin microencapsulated human islets of Langerhans and their potential for type 1 diabetes mellitus therapy

BACKGROUND: Microencapsulation of pancreatic islets with polymeric compounds constitutes an attractive alternative therapy for type 1 diabetes mellitus. The major limiting factor is the availability of a biocompatible and mechanically stable polymer. We investigated the potential of Biodritin, a novel polymer constituted of alginate and chondroitin sulfate, for islet microencapsulation. METHODS: Biodritin microcapsules were obtained using an air jet droplet generator and gelated with barium or calcium chloride. Microencapsulated rat insulinoma RINm5F cells were tested for viability using the [3-(4,5-dimetyl-thiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide] [MTT] colorimetric assay. Microencapsulated rat pancreatic islets were coincubated with macrophages derived from mouse peritoneal liquid to assess the immunomodulatory potential of the microcapsules, using quantitative real time-PCR (qPCR). Biodritin biocompatibility was demonstrated by subcutaneous injection of empty microcapsules into immunocompetent Wistar rats. Insulin secretion by microencapsulated human pancreatic islets was evaluated using an electrochemoluminescent assay. Microencapsulated human islets transplanted into chemically induced diabetic mice were monitored for reversal of hyperglycemia. RESULTS: The metabolic activity of microencapsulated RINm5F cells persisted for at least 15 days. Interleukin-1beta expression by macrophages was observed during coculture with islets microencapsulated with Biodritin-CaCl2, but not with Biodritin-BaCl2. No statistical difference in glucose-stimulated insulin secretion was observed between nonencapsulated and microencapsulated islets. Upon microencapsulated islet transplantation, the blood glucose level of diabetic mice normalized; they remained euglycemic for at least 60 days, displaying normal oral glucose tolerance tests. CONCLUSION: This study demonstrated that Biodritin can be used for islet microencapsulation and reversal of diabetes; however, further investigations are required to assess its potential for long-term transplantation.     

微囊化新生猪甲状旁腺细胞异种移植的实验研究

目的 探讨微囊化新生猪甲状旁腺细胞异种移植治疗大鼠甲状旁腺功能低下症的效果。方法 应用微囊化技术，制备微囊化（海藻酸钠－聚赖氨酸－海藻酸钠生物微胶囊）新生猪甲状旁腺细胞，32只去甲状旁腺的Wistar大鼠随机分成微囊组、非微囊组、空囊组和对照组，分别移植微囊化新生猪甲状旁腺细胞、甲状旁腺细胞、空微囊及生理盐水。移植后监测血钙及甲状旁腺素水平40周，40周后回收移植物，透射电镜检查。结果 移植后，微囊组大鼠血钙及甲状旁腺素水平恢复到正常范围内，直至观察结束时（40周），透射电镜检查显示移植物存活良好；非微囊组、空囊组和对照组大鼠的血钙及甲状旁腺素水平无改善。结论 微囊化新生猪甲状旁腺细胞异种移植在不用免疫抑制剂情况下，可以在大鼠体内存活，且有功能；海藻酸钠－聚赖氨酸－海藻酸钠生物微胶囊对免疫活性细胞及抗体具有屏蔽作用。     

Survival of microencapsulated islets at 400 days posttransplantation in the omental pouch of NOD mice

The long-term durability of agarose microencapsulated islets against autoimmunity was evaluated in NOD mice. Islets were isolated from 6-8-week-old prediabetic male NOD mice and microencapsulated in 5% agarose hydrogel. Microencapsulated or nonencapsulated islets were transplanted into the omental pouch of spontaneously diabetic NOD mice. Although the diabetic NOD mice that received nonencapsulated islets experienced a temporary reversal of their hyperglycemic condition, all 10 of these mice returned to hyperglycemia within 3 weeks. In contrast, 9 of 10 mice transplanted with microencapsulated islets maintained normoglycemia for more than 100 days. Islet grafts were removed at 100, 150, 200, 300, and 400 days posttransplantation. A prompt return to hyperglycemia was observed in the mice after graft removal, indicating that the encapsulated islet grafts were responsible for maintaining euglycemia. Histological examination revealed viable islets in the capsules at all time points of graft removal. In addition, beta-cells within the capsules remained well granulated as revealed by the immunohistochemical detection of insulin. No immune cells were detected inside the microcapsules and no morphological irregularities of the microcapsules were observed at any time point, suggesting that the microcapsules successfully protected the islets from cellular immunity. Sufficient vascularization was evident close to the microcapsules. Considerable numbers of islets showed central necrosis at 400 days posttransplantation, although the necrotic islets made up only a small percentage of the islet grafts. Islets with central necrosis also showed abundant insulin production throughout the entire islets, except for the necrotic part. These results demonstrate the long-term durability of agarose microcapsules against autoimmunity in a syngeneic islet transplantation model in NOD mice.