乌司他丁对犬胰岛的保护作用

目的判定在机械分离纯化犬胰岛过程中,胰腺原位灌洗时应用乌司他丁(UTI)的保护作用,观察胰岛的获取产量。方法将20只犬随机分为两组,每组10只。HC-A组:胰腺经腹主动脉原位灌洗时用冷HC-A液2500ml;HC-A UTI组:胰腺原位灌洗时,HC-A液中加用UTI10000U/kg。两组均经主胰管用4℃胶原酶V控压灌注,在RicordiChamber系统中消化,用Ficoll连续梯度离心纯化。记录消化时间、胰岛外分泌腺包裹率、胰岛纯度、纯化后胰岛在体外用低糖与高糖刺激下胰岛素分泌量、C-肽的释放量及收获的胰岛当量(IEQ),并对纯化后的胰岛进行光镜及电镜观察。结果HC-A UTI组与HC-A组在胰腺消化时间、胰岛外分泌腺包裹率、胰岛纯度、纯化后的胰岛在体外经低糖与高糖刺激下胰岛素分泌量、C-肽的释放量以及胰岛的形态和结构上比较,差异均无统计学意义(P>0.05)。HC-A组收获胰岛[(3.42±1.47)×104]IEQ,HC-A UTI组收获胰岛[(6.17±2.86)×104]IEQ,两组差异有统计学意义(P<0.05)。结论在犬胰岛分离和纯化过程中,胰腺获取原位灌洗液中加用UTI能保护胰腺组织,增加胰岛产量。     

猪胰岛的分离与纯化

目的 探索大规模猪胰岛细胞分离纯化的方法.方法 联合器官切取,胶原酶P主胰管灌注,COBE2991细胞分离机及HCA-Ficoil纯化猪胰岛细胞.通过双硫腙(DTZ)染色,倒置显微镜下计数胰岛细胞的数量和纯度,胰岛素释放试验检测胰岛细胞的分泌功能.结果 消化后平均每条胰腺可平均获得(275 000±20 895)胰岛细胞当量(IEQ),纯化后平均为(230 350±26 679)IEQ,平均每克胰腺组织可获得(2710±229)IEQ,纯化后胰岛细胞平均纯度为(50.2±1.95)%.纯化后的胰岛细胞对胰岛素释放刺激反应良好,高糖(16.7 mmol/L)时胰岛素的释放量为低糖(3.3 mmol/L)时的4.74倍(P≤0.001).结论 成功建立了猪胰岛细胞分离、纯化的方法,纯化的猪胰岛细胞具有良好的生物活性.     

成人胰岛大容量分离技术的改进及胰岛功能检测

目的 通过对人胰岛分离技术的改进以获得大量高活力胰岛并检测其功能,为利用同种异体胰岛移植治疗1型和部分2型糖尿病提供理论依据和技术基础。方法 采用改良的自动分离技术连续分离28例人胰岛,然后用连续性密度样度离心法纯化胰岛。胰岛收获量以国际标准的胰岛当量(islet equivalent,IEQ)表示。胰岛功能的测定分别为体外测定胰岛的胰岛素／DNA比率;静止葡萄糖刺激试验(SGS)及将胰岛移植至糖尿病裸小鼠的体内胰岛功能鉴定并随后进行腹腔糖耐量试验,连续测定移植鼠血糖水平及其体内C肽浓度。结果 28例成人胰腺分离的胰岛收获量为5000～1030000IEQ／胰腺,平均为291635IEQ／胰腺,前13例平均每个胰腺收获49123IEQ,平均每克组织收获846IEQ。平均纯度为87％,随着技术的改进后15例的分离结果则分别为：平均每个胰腺501813IEQ,平均每克组织7003IEQ,平均纯度89％。体外胰岛素刺激试验结果表明分离纯化后的人胰岛有正常功能,将12次分离得到的胰岛分别移植至34只糖尿病裸鼠肾包膜下,其中29只糖尿病裸鼠于12h内血糖恢复正常且糖耐量试验接近正常鼠,血中C肽水平亦接近正常鼠。结论 采用改进的人胰岛分离方法,可以获得大量高活力的具有正常功能的胰岛,为同种异体胰岛移植用于临床奠定了必要的实验基础。     

大量人胰岛分离技术的改进及相应胰岛功能的检测

目的 通过对人胰岛分离技术的改进以获得大量高活力胰岛并检测其功能。方法采用经典及改良技术分离、纯化28例人胰岛。胰岛收获量以胰岛当量(IEQ)表示。胰岛功能测定分别为体外测定胰岛素/DNA比率、静止葡萄糖刺激试验(SGS)及将胰岛移植至糖尿病裸小鼠的体内功能鉴定并行糖耐量试验,连续测血糖水平及其体内C肽浓度。结果 前13例采用经典方法,平均每个胰腺收获49123 IEQs,平均846 IEQs/g胰腺组织,平均纯度为87％。改进技术后15例的分离结果则分别为:501813 IEQs/胰腺,7003 IEQ/g胰腺组织及纯度89％。体外胰岛素刺激试验结果表明分离纯化后的人胰岛有正常功能,将12次分离得到的胰岛分别移植至34只糖尿病裸鼠肾包膜下,其中29只糖尿病裸鼠于12h内血糖恢复正常且糖耐量试验接近正常鼠,血中C肽水平亦接近正常。结论 采用改进的人胰岛分离方法,可以获得大量高活力的具有正常功能的胰岛,为同种异体胰岛移植用于临床奠定了必要的基础。     

大鼠胰岛的分离纯化方法改进与功能鉴定

目的 通过改进胰腺消化和分离的技术条件,提高成年大鼠胰岛分离纯化产率和质量. 方法 用胶原酶Ⅺ液灌注消化成年SD大鼠胰腺,对胰岛分离纯化方法加以改进:以 4 种比重的 Euro- Ficoll (F1∶D=1.132,F2∶D=1.108,F4∶D=1.069) 和 Hank's 液(F5∶D=1.023) 不连续密度梯度离心,以离心半径 15 cm,2 000 r/min 于4℃缓慢升降离心 20 min,收集位于F1 和 F2界面的胰岛.双硫腙特异染色法鉴定胰岛纯度;二醋酸酯荧光素/碘化丙啶染色法计算胰岛成活率;放射免疫分析法检测葡萄糖刺激的胰岛素分泌量,计算刺激指数.将胰岛当量(islets equivalent quantity,IEQ) 为 1000 的胰岛移植于同品系糖尿病大鼠肾包膜下,9d 内隔日观察动物血糖的变化,评价胰岛功能.比较分离条件优化前后收获胰岛的产率和质量. 结果 改进纯化方法后每只大鼠胰岛收获量为(920±122) IEQ,胰岛纯度> 90%,胰岛细胞成活率为 91%±2%.胰岛细胞功能良好,在低糖和高糖刺激后培养液中胰岛素浓度分别为(18.25±0.32) mU/L 和(36.70±3.57)mU/L,刺激指数为 2.01±0.15.1000 IEQ 胰岛移植于糖尿病大鼠肾包膜下,观察期内可维持动物血糖水平正常. 结论 改进后的胶原酶灌注消化和不连续梯度离心方法提高了胰岛的产率,保证了胰岛的高纯度及高成活率.     

机械分离成人尸体胰腺提高胰岛数量和质量

目的通过机械分离胰腺的方法,提高成人胰岛数量和质量。方法切取8个成人尸体胰腺,并保存于4℃UW液中。首先经主胰管插管灌注复合胶原酶溶液,使胰腺膨胀,然后将胰腺剪切成5~8块,放入Ricordi室中,于37℃下机械震荡消化。收集的胰岛溶于100mlUW液中,放置30min。先将Ficoll液泵入COBE2991细胞分离仪中,然后泵入UW/胰岛制剂,最后加入M199液冲洗。收集纯化的胰岛,计算胰岛当量(IEQ)和纯度,检测胰岛的活性。结果热缺血时间为0~1min,冷缺血时间0.5~4h。纯化前收集的胰岛数量平均为(376.7±50.2)×103IEQ,纯化后为(378.6±56.7)×103IEQ;胰岛收获率平均为(86.8±9.4)%,镶嵌的胰岛平均占(11.0±2.7)%;收获的胰岛纯度平均为(88.3±5.1)%;经AO-PI染色后检测胰岛的活度为(91.3±7.8)%。胰岛素分泌指数平均为5.87±0.81。结论通过机械分离胰腺的方法,可以获得更多的胰岛数量和更高的胰岛活性,适合用于临床移植。     

采用改良的胰腺三管插管法分离成人胰岛的实验研究

目的 探讨胰腺插管方式对成人胰岛分离及纯化的影响.方法 共对17例成人胰腺进行了胰岛的分离和纯化.采用改进的腹部器官联合快速切取技术获取胰腺,分别采用标准法(3例)、单管法(11例)和三管法(3例)对胰腺进行灌注.标准法是将胰腺从胰颈处完全切断,沿主胰管分别向胰头和胰尾插管,主胰管人十二指肠处予以结扎.单管法为采用加长插管自主胰管插入,直至胰尾.三管法是在胰颈背侧切开胰腺至主胰管,经主胰管分别向胰头和胰尾方向插管,在主胰管进入十二指肠处插第3根插管.采用胶原酶LibarseHI消化,Ficoll连续密度梯度离心法纯化.双硫腙染色,鉴定胰岛的纯度,并计算胰岛当量(IEQ).丫啶橙/溴乙啶荧光染色,计数活细胞百分率.体外葡萄糖刺激试验鉴定胰岛功能.结果 标准法的灌注量平均为0.71 ml/g胰腺,单管法的灌注量平均为0.96 ml/g胰腺,三管法的灌注量平均为1.24 ml/g胰腺,明显多于前两种方法(P＜0.05).标准法的胰岛收获量平均为1914 IEQ/g胰腺,单管法为2270 IEQ/g胰腺,三管法为2514 IEQ/g胰腺,单管法和三管法明显高于标准法(P＜0.05);其胰岛纯度/活性分别为74 ％/79.3％、75.6 ％/79.4％和78.3 ％/84.0％,三者间的差异无统计学意义.标准法所获得的胰岛胰岛素释放指数平均为3.46,单管法为4.74,三管法为5.27,单管法和三管法明显高于标准法(P＜0.05).结论不同的插管灌注方式对成人的胰岛分离有一定影响,三管法有利于提高胰腺灌注量,增加胰岛的收获量.     

不同胶原酶消化对大鼠胰岛的纯化和获得率的影响

目的 比较不同胶原酶消化大鼠胰腺的效果,选择消化效果较好的胶原酶.方法 采用随机数字表法将SD大鼠分为2组,胶原酶P组大鼠胰腺使用1 mg/ml的胶原酶P液进行消化,Ⅴ型胶原酶组大鼠胰腺使用1 mg/ml的Ⅴ型胶原酶进行消化.胰腺消化后,对获得的两组大鼠胰岛进行纯化、培养.采用双硫腙染色于倒置显微镜下计数纯化前后获得的两组全部胰岛数量,并计算胰岛当量(IEQ);采用吖啶橙和碘丙啶双色荧光染色,于荧光显微镜下计数纯化后胰岛的活率;两组大鼠胰岛经纯化、培养2d后进行胰岛素释放试验,观察两组胰岛的功能.结果 纯化前,两组间每个大鼠胰腺获得的胰岛数量的差异无统计学意义(P＞0.05);但两组间IEQ的差异有统计学意义(P＜0.05);经纯化后,Ⅴ型胶原酶组和胶原酶P组每个大鼠胰腺获得的胰岛数量分别为485±113和643±82,IEQ分别为674±157和989±126,两组间胰岛数量和IEQ的比较,差异均有统计学意义(P＜0.05).Ⅴ型胶原酶组和胶原酶P组大鼠胰岛经纯化后,其活率分别为(96.13±1.13)％和(96.38±0.92)％,两组比较,差异无统计学意义(P＞0.05).胰岛素释放试验结果显示,在低糖或高糖刺激下,两组间大鼠胰岛功能的差异均无统计学意义(P＞0.05).结论 两种胶原酶均适用于大鼠胰腺的消化,但胶原酶P消化效果较Ⅴ型胶原酶稳定,且胰岛获得率也较高.     

人工生物胰的体外分泌功能研究

目的 探讨海藻酸钠-氯化钡微囊对成人胰岛细胞体外分泌功能的影响.方法 对6例成人胰腺组织称重后采用V型胶原酶消化法分离,采用Ficoll间断密度梯度离心纯化法纯化,采用DTZ染色显微镜下评价胰岛细胞的数量、纯度.采用海藻酸钠氯化钡为材料包裹成人胰岛,体外培养及放射免疫法测定培养液中基础胰岛素浓度.结果 成人胰腺经胶原酶消化分离后,胰岛平均收获量(3600±447)个胰岛/g胰腺；Ficoll间断密度梯度离心纯化后,每克胰腺组织平均收获量(2140±207)个胰岛,纯度大于70％；成人胰岛细胞培养2、4、6d后,微囊化组第2、4、6天的基础胰岛素平均浓度(每100个胰岛单位mU/L)分别为3.302±1.63、3.504±1.10、2.921±1.13,未微囊化组的基础胰岛素平均浓度(每100个胰岛单位mU/L)分别为3.814±1.49、4.175±1.60、3.617±1.34,两组基础胰岛素浓度差异无统计学意义(P＞0.05).结论 人工生物胰具有良好的体外分泌功能,包裹成人胰岛的海藻酸钠-氯化钡微囊对胰岛体外分泌胰岛素的功能无影响.     

成人胰岛细胞移植治疗1型糖尿病

目的 探讨新型成人胰岛细胞分离、纯化技术分离的成人胰岛细胞移植治疗1型糖尿病的安全性与有效性.方法 采用全氟化碳液(PFC)和UW液双层冷藏胰腺,Liberase酶消化,COBE 2991型专用胰岛细胞分离机分离及连续密度梯度纯化,获取高纯度与高活性的胰岛细胞.通过上腹部小切口,胃右静脉或脐静脉插管,将经短期培养的胰岛细胞经门静脉移植到11例1型糖尿病患者肝脏内.采用达利珠单抗或阿来佐单抗进行诱导,西罗莫司和他克莫司联用的方案预防排斥反应,术后观察胰岛素使用情况,监测血糖、G-肽与糖化血红蛋白水平以及肝功能、肾功能.结果 45个胰腺中,42个成功分离出胰岛细胞,其数量平均为28.5×104胰岛当量(IEQ)/个,纯度为95.7%,活率为93.2%,胰岛素释放试验刺激指数为2.43.11例1型糖尿病患者共行胰岛细胞移植20次,其中移植1次4例,2次5例,3次2例,每次移植胰岛细胞数平均为11 200 IEQ/kg.术后随访6个月至4年,6例完全撤除胰岛素,2例胰岛素用量较术前减少80%,3例减少50%.术后血糖稳定维持在正常水平,C-肽均超过0.166 nmol/L,糖化血红蛋白基本正常,肝、肾功能正常,未发生与胰岛细胞输注相关的并发症.结论 新型成人胰岛细胞分离、纯化方法可靠,采用该技术分离、纯化的成人胰岛细胞移植治疗1型糖尿病临床效果较好.     

Improved recovery of human islets from young donor pancreases utilizing increased protease dose to collagenase for digesting peri‐islet extracellular matrix

Human islet isolation from young donor pancreases (YDP) utilizing the current purified standard dose of collagenase‐protease enzyme mixtures often results in the release of a high percentage of mantled islets. Mantled islets are those surrounded by exocrine tissue and are difficult to purify by density gradient centrifugation, leading to poor islet recovery. Based on difference in extracellular matrix, and total collagen content between YDP and old donor pancreas (ODP, > 35 Y) led us to compare results from islet isolation using increased collagenase combination (ICC) or increased protease combination (IPC), to the standard enzyme combination (SEC) in a “trisected” pancreas model to overcome the donor‐to‐donor variability. These results showed a reduced percentage of mantled islets (17% ± 7.5%) and higher postpurification islet recovery (83.8% ± 5.6%) with IPC. Furthermore, these results were confirmed in 13 consecutive whole pancreas islet isolations utilizing IPC from VitaCyte, Roche, or SERVA collagenase‐protease enzyme mixtures. Results obtained from in vitro and in vivo islet functional assessment indicated that islets isolated using IPC retained normal islet morphology, insulin secretion, and the ability to reverse diabetes after transplantation in diabetic nude mice. This is the first report utilizing trisected pancreas to assess the effectiveness of different enzyme combinations to improve islet recovery from young donor pancreases.     

Experimental islet isolation in porcine pancreas with new enzyme Liberase PI

The aim of this study was to investigate the results of 20 consecutive porcine islet isolations using a new enzyme Liberase PI. Twenty pancreata were procured for islet isolation, which was performed using modified Ricordi's method with Liberase PI. Quantitation of islet viability staining, insulin stimulation assay, intracellular insulin content/DNA, and in vivo transplantability into diabetic nude mice were examined for quality control. The results were compared between a high-yield group (>2500 IEQ/g pancreas) and a low-yield group (<2500 IEQ/g pancreas). Sufficient amount of purified islets (3000 IEQ/g pancreas) were obtained using the new brand enzyme Liberase PI. These islets showed good quality in structure and functions, which were demonstrated by in vitro and in vivo standard assays. Isolation index (IEQ/number) of the low-yield group was lower than that of high-yield group (0.75 vs 0.86), which means more fragmentation of islets in the low-yield group. There were no differences in function between the two groups. In conclusion, we obtained sufficient numbers of viable, functional islets from porcine pancreas using a new brand enzyme Liberase PI and low-temperature isolation technique. However, overdigestion of islets during the isolation remains to be overcome. Advance in porcine islet isolation technique will in the future make the porcine islet xenotransplantation a reality for the cure of diabetes mellitus.     

Serine-protease inhibition during islet isolation increases islet yield from human pancreases with prolonged ischemia.

BACKGROUND: Islet isolation from the pancreatic tissue matrix remains highly variable. Recent evidence suggests that intrinsic human pancreatic proteases, including trypsin, may inhibit effective collagenase enzymatic activity during islet isolation, thereby impairing the isolation success. In this study we have hypothesized that serine protease inhibition applied during pancreatic digestion, could improve yield and/or functional viability of islets isolated from human pancreases. METHODS: Twelve organ donor pancreases with 12.9+/-0.6 hr cold storage (mean+/-SEM) were perfused via their ducts with Liberase-HI enzyme in the presence (n=6) or absence (n=6) of 0.4 mM Pefabloc. All were then gently dissociated and their purified islets separated with Ficoll density gradient centrifugation. RESULTS: Donor-related factors (age, gender, cold storage time, body mass index, and pancreas weight) did not differ significantly between the two experimental groups. Pefabloc supplementation did not affect the digestion time, islets remaining trapped in exocrine tissue, or final islet purity. Islet recovery was increased in the Pefabloc-treated group (mean+/-SEM yield 323.8+/-80.8 x 10(3) islet equivalents vs. 130.8+/-13.6 x 10(3) islet equivalents, P<0.05). Cellular composition, DNA and insulin content, and insulin secretory activity of the isolated islets was similar. CONCLUSIONS: Inhibition of intrinsic protease activity within pancreases after prolonged cold storage improves isolation of viable islets.     

Factors that affect human islet isolation

More than 10,000 IEQ/kg recipient weight of islets is often necessary to achieve insulin independence in patients with type 1 diabetes mellitus. Several studies have identified high donor body mass index (BMI) and pancreas size as important factors for the success of human islet isolation. However, the donor shortage underscores the need to improve isolation outcomes from lower BMI pancreas donors and/or small pancreata. The aim of this study was to identify the critical factors that affect isolation outcome. We analyzed the data from 207 isolations performed from 2002 to 2006 with respect to donor characteristics, pancreas condition, and processing variables. More than 3000 IEQ/g pancreas weight was considered to be an acceptable isolation outcome. This goal was obtained from donors with a BMI >30 kg/m2 (P = .002). The pancreatic surface integrity was also a significant factor (P = .02). Moreover, longer digestion times (P = .04) and a greater proportion of trapped islets negatively affected success rates (P = .004). As previously reported, pancreata from high BMI donors were suitable for islet isolation and transplantation, as they yielded higher total islet particle numbers and higher IEQ/g. Although BMI and pancreas size are not controllable due to the organ donor shortage, factors such as pancreatic surface integrity, shorter digestion time, and lower proportions of trapped islets were found to be significant to obtain higher success rates. The development of better protocols and systematic training of processing/procurement teams will be of assistance to increase the number of successful human islet isolations.     

Clinical use of donation after circulatory death pancreas for islet transplantation

Due to a shortage of donation after brain death (DBD) organs, donation after circulatory death (DCD) is increasingly performed. In the field of islet transplantation, there is uncertainty regarding the suitability of DCD pancreas in terms of islet yield and function after islet isolation. The aim of this study was to investigate the potential use of DCD pancreas for islet transplantation. Islet isolation procedures from 126 category 3 DCD and 258 DBD pancreas were performed in a 9-year period. Islet yield after isolation was significantly lower for DCD compared to DBD pancreas (395 515 islet equivalents [IEQ] and 480 017 IEQ, respectively; p = .003). The decrease in IEQ during 2 days of culture was not different between the two groups. Warm ischemia time was not related to DCD islet yield. In vitro insulin secretion after a glucose challenge was similar between DCD and DBD islets. After islet transplantation, DCD islet graft recipients had similar graft function (AUC C-peptide) during mixed meal tolerance tests and Igls score compared to DBD graft recipients. In conclusion, DCD islets can be considered for clinical islet transplantation.     

Isolation and Purification of Islet Cells From Adult Pigs

We used in situ perfusion and a multiple-organ harvesting technique to collect islets from adult pig pancreata. The tissues were digested with collagenase P followed by purification in a lympholyte discontinuous gradient using a COBE2991 cell separator. The yield and purity of isolated islets were evaluated with a light microscope after dithizone (DTZ) staining. Islet function was assessed using an in vitro insulin release assay. The results showed that before purification 275,000 ± 20,895 islet equivalents (IEQ) were obtained from 1 digested pancreas. After purification with gradient centrifugation, the islet yield was 230,350 ± 26,679 IEQ/pancreas. Each gram of the purified pancreatic tissues yielded 2710 ± 229 IEQ with an average purity of 50.2 ± 2.0%. The purified islet cells responded to stimulation with high glucose concentrations (16.7 mmol/L), namely, 4.74-fold greater than the insulin secretion with exposure to the basal level of glucose (3.3 mmol/L; P < .001). These results suggested that the established isolation method can be applied to large-scale purification of fully functional islets from pig pancreata.     

Can the density of native pancreatic tissue slices predict human islet isolation and purification outcome?

INTRODUCTION: With currently available technology, the outcomes of human islet isolation and purification are still inconsistent, in part due to a lack of control of the pancreas donor and the procurement conditions. Using a single donor pancreas, the critical islet mass for establishing insulin independence of approximately 5000 engrafted islet equivalents (IEQ)/kg of recipient weight can only be retrieved from about one third of isolations. The purpose of this study was to analyze whether successful islet isolation and purification outcomes might be predicted from the density of native pancreatic tissue. METHODS: Tissue slices (TS) were obtained from the neck of 9 nondistended human donor pancreata. The density of the TS was determined using gravity sedimentation in continuous density gradients under either iso-osmolar or hyperosmolar conditions. Correlation coefficients were calculated with regard to the density of isolated exocrine and endocrine tissue, donor age, body mass index (BMI), cold ischemia time (CIT), IEQ prepurification and postpurification, IEQ recovery, and purity. RESULTS: (1) There was no change in density over time for TS in 300 mOsm/kg (mean, 1.079 +/- 0.0019 g/cm(3)) (2) In 500 mOsm/kg, there was a significant increase in density from 1.086 +/- 0.0021 g/cm(3) to 1.092 +/- 0.0021 g/cm(3) over time. (3) Density of isolated exocrine and endocrine became more distinct with lower density of TS (r = -0.776; P < .05). (4) Donor age, BMI, recovery of IEQ from gradients, and number of IEQ after purification did not correlate significantly with TS density. (5) In contrast, a significant inverse correlation existed betwen TS and CIT (r = -0.829; P < .05), and between TS versus IEQ number prior to purification (r = -0.867; P < .05). CONCLUSION: No homogeneous distribution of pancreas tissue density was seen among 9 consecutive human organs. Taken together, the density of native pancreas TS is not a suitable sole predictor for successful islet isolation and purification.     

Analysis on donor and isolation-related factors of successful isolation of human islet of Langerhans from human cadaveric donors

We analyzed the preexisting donor factors and isolation variables that affected isolation of human islets of Langerhans. Sixty-nine pancreata from cadaveric donors were analyzed for donor factors of age, gender, body mass index, cause of death as well as graft factors of cold ischemia time, pancreas status, distensibility during intraductal collagenase distension and time of collagenase expansion and digestion. Islet isolations that recovered >100,000 IEQ (n = 53) were compared to those generating less than 100,000 IEQ (n = 16) to analyze the factors affecting islet yield during donor harvest and isolation procedures. The mean islet recovery was 216.0 x 10(3) (IEQ) or 2840 (IEQ) per gram of pancreas. Mean purity was 54%. The success rate of islet isolation was 76%. Mean age was 31 years, and mean cold ischemia time was 6.9 hours. In univariate analysis, the status of the pancreas was the only significant factor for successful isolation, and gender, time of collagenase expansion and digestion were marginal factors. In stepwise multivariate logistic regression analysis of donor and isolation-related factors, donor gender, pancreas status and digestion time were significant factors. During the same period we performed three cases of clinical islet allotransplantation and one autotransplantation. This study confirmed that the same donor factors and variables in the isolation process can affect the ability to obtain successful human islet isolation. Enough experience and pertinent review of donor and isolation factors can make islet isolation consistent, supporting clinical islet transplantation without unnecessary cost.     

Evaluation of a Purified Enzyme Blend for the Recovery and Function of Canine Pancreatic Islets

Recently developed technologies enabling the production of a reproducible, purified enzyme blend for optimal human pancreatic islet isolation has renewed interest in clinical islet transplantation. The canine model has been an ideal preclinical model for the development of islet transplantation protocols. As seen in other species, the application of crude collagenase for isolating canine islets resulted in highly variable islet yields, extensive islet fragmentation, and variable islet functionality. We compared the function of commercially available crude collagenases with that of Liberase™-CI purified enzyme blend for canine islet isolation. We also compared two manufacturing runs of Liberase-CI enzyme (lots 1 and 2) to demonstrate reproducibility of islet recovery and function. We report on the improved recovery and function of islets isolated using Liberase-CI enzyme. No difference in dog age, mean body weight, or pancreas weight were observed between the experimental groups. We observed a significantly higher postpurification recovery of islet equivalent number (IE) from pancreases processed using two lots of Liberase-CI enzyme (189 ± 20 × 103 IE, n = 4) and lot 2 (234 ± 39 × 10³ IE, n = 7) than that obtained from pancreases processed with Sigma Type V (116.8 ± 27 × 10³ IE, n = 5), Serva collagenase (49 ± 11.6 × 10³ IE, n = 5, p < 0.05) or Boehringer–Mannheim (BM) Type P collagenase (85.4 ± 25 × 10³ IE, n = 5, p < 0.05, ANOVA). No significant differences were observed in islet yield recovery from pancreases processed using the two production lots of Liberase-CI enzyme. Islet survival after 48 h in culture at 37°C was significantly higher from islets isolated using Liberase-CI enzyme (88 ± 3.7% survival) when compared to Sigma Type V (81.8 ± 3.3%), Serva (71.7 ± 2.8%), and BM Type P (77 ± 7.2%) (p < 0.05). Islet functional testing in vitro demonstrated islets isolated using crude collagenase had an increased insulin basal release and a reduced insulin stimulated response when compared with islets isolated using the two lots of Liberase-CI enzyme. The calculated stimulation index was 7.8 ± 1.7, 3.1 ± 0.6, and 4.8 ± 1.1 for Sigma Type V, Serva, and BM Type P isolated islets, respectively, compared to 15.7 ± 1.6 and 16.2 ± 1.9 for islets isolated with Liberase-CI enzyme production lots 1 and 2, respectively (p < 0.05). This evaluation demonstrates that a purified enzyme blend can significantly improve islet recovery and function. It also demonstrates the manufacturing reproducibility of Liberase-CI enzyme lots resulting in the isolation of canine islets with the same degree of efficacy. A blend of purified enzymes, specifically formulated for canine islet isolation, can consistently yield large numbers of islets that survive longer in culture and demonstrate an improved insulin response in vitro.