Successful human islet isolation utilizing recombinant collagenase

The enzymatic dissociation of acinar tissue by collagenase is a substantial step in the isolation of pancreatic islets. Although essential collagenase components have been purified, the variability in the activity of different batches limits long-term reproducibility of isolation success. The utilization of purified recombinant proteases would solve this problem. In the present study, pancreases from multiorgan donors were dissociated by means of digestion-filtration using either Liberase HI (n = 51) or a recombinant collagenase blend (n = 25). No significant differences were found regarding islet yield before and after purification, the percent of exocrine-attached islets, and final purity. However, the ratio between islet equivalents and islet numbers indicated a lesser fragmentation in islets isolated with recombinant collagenase (P < 0.01). In contrast, viability was slightly higher in islets isolated with Liberase (92.3 +/- 0.8 vs. 85.6 +/- 2.9%; P < 0.05). Insulin release during static glucose incubation was not different between experimental groups. Islet transplantation into diabetic nude mice resulted in sustained normoglycemia in either group until the graft was removed. These results demonstrated that viable human islets can be isolated using recombinant collagenase. Final optimization of this enzyme blend would offer continuous reproducibility of isolation success.     

Factors influencing the collagenase digestion phase of human islet isolation

Substantial advances in human islet isolation technology have occurred during the past decade. However, it is still difficult to recover the entire quantity of islets contained in a pancreas. A major obstacle to successful human islet isolation has been the variability of the collagenase digestion phase of islet isolation. Future advances in enzyme technology will make it possible to optimally liberate islets with enzyme blends "tailor-made" for each individual donor pancreas. Such innovative strategies will be advantageous in improving islet isolation efficiency, recovery, viability, and ultimately posttransplant function.     

Peri-insular presence of collagenase during islet isolation procedures.

Reportedly, higher islet yields are obtained by ductal collagenase administration and subsequent digestion of the pancreas than by the chopped tissue collagenase digestion technique. However, the exact mechanism of islet isolation is not known. This study aims to understand the underlying mechanism of a favorable effect of ductal collagenase administration. To this end, we investigated if the higher yields can be explained by a different distribution of the collagenase enzymes in the pancreatic tissue after ductal application as compared to during chopped tissue digestion. India ink was used to mimic and visualize the distribution of collagenase in histological sections of pancreases of several species. Ink particles were seen around and even within the islets both after ductal application and during chopped tissue collagenase digestion. Thus, collagenase enzymes are not restricted to the exocrine tissue compartment with either technique. In view of this observation, we compared the efficacy of both techniques in islet isolation procedures in paired experiments in rats. Both techniques gave similar islet yields to those reportedly obtained with the ductal collagenase method. However, with either technique, the islet yield was only approximately 50% of the endocrine volume of the pancreas, indicating that a substantial loss of islet tissue had occurred. We conclude that, irrespective of the route of collagenase administration, collagenase enzymes are present in the peri-insular space during islet isolation procedures. This is pertinent in view of the finding that both methods have similar islet yields in rats and that collagenase digestion, as such, is associated with loss of islet tissue.     

Quantitative assessment of collagenase blends for human islet isolation

BACKGROUND: The variability in collagenase blends has been speculated as the single most important determinant of the success or failure in isolated islet yields in clinical islet transplantation. Examination of the formulation and potency of the widely used Liberase HI enzyme blend will uncover possible sources of imprecision. METHODS: High performance liquid chromatography (HPLC) and kinetic measurements of collagenase and protease activity were used to assess potency. Between four and nine clinical lots were assessed for various parameters such as relative formulation of collagenase isoforms, and recovered collagenase and protease potencies postreconstitution. RESULTS: Six vials from a single typical lot had a mean enzyme content of 489+/-62.5 mg (mean+/-SEM; range 398-610 mg). The mean recovered collagenase activity was 2235+/-310 Wünsch units (WU)/vial (range 1794-2968 WU/vial). The percent coefficients of variation for collagenase and protease activity in these vials were 17.4%, and 13.4%, respectively. The increase in the presence of the collagenase Ib (CIb) isoform detected by HPLC analysis was related to the chronological order of the date of manufacture. The CIb isoform was found to have a reduced specific activity compared to intact collagenase I (CI) (3.8+/-1.2 WU/mg vs. 2.1+/-0.7 WU/mg, P < 0.05). The presence of CIb was related to reduced islet yields in twelve human isolations studied. CONCLUSIONS: Variation in potency was observed between, and within lots of Liberase HI in this study. Differences in relative collagenase isoform composition may also affect the stability and potency characteristics of these blends.     

Optimization of neutral protease to collagenase activity ratio for islet of Langerhans isolation

AIM: The optimal neutral protease to collagenase activity ratio has not been determined for islet isolation. We evaluated a new highly purified collagenase that can be blended with predetermined amounts of neutral protease (NP). METHODS: Islets were isolated from 7 groups of Sprague-Dawley rats. In group I, collagenase type XI (Sigma) at 2 mg/mL, and, in group II, Liberase at 0.6 mg/mL (2.4 PZ- U/mL; Roche) were used as controls. In groups III to VII, collagenase NB1 0.6 mg/mL (2.4 PZ-U/mL; Serva Electrophoresis) was used with increasing amounts of added NP. The NP to collagenase activity ratio (DMC-U/PZ-U) increased from 0.5% in group III to 2.0% in group VII. RESULTS: Mean islet equivalent (IE) yields per rat were 1367, 1755, 597, 895, 1712, 1043, and 905 in groups I to VII. IE yields were maximal at DMC-U/PZ-U = 1.2%. Islet morphology was influenced by NP concentration with decreasing numbers of trapped islets and increasing numbers of fragmented islets as NP contents increased. Cytokine release, islet cell apoptosis, and in vitro function were significantly better in groups III to VII as compared with groups I and II. CONCLUSION: NP is a crucial additive to collagenase for islet isolation. Optimization of the NP to collagenase activity ratio (1.2% in this model) improves yields and morphology after islet isolation.     

Improved human islet isolation by a tube method for collagenase infusion.

BACKGROUND: Collagenase infusion into the pancreatic duct is an essential step in human islet isolation. We developed a new method for ductal canulation and collagenese infusion. METHODS: A total of 53 pancreata were divided into two groups: group 1 (n=23), the new tube method, and group 2 (n=30), the standard angiocatheter method. In group 1, a polyethylene tube was inserted into the duct and pushed to the tail. The tail was first expanded, followed by expansion of the body and then the head, by pulling out the tube. RESULTS: Total islet number and number/g pancreas (mean+/-SE) were significantly higher in group 1 (481,123+/-43,218 and 8,010+/-722) (mean+/-SE) than in group 2 (300,974+/-35,122 and 5,090+/-515, P<0.01). Total islet equivalent number and islet equivalent number per gram pancreas were also significantly higher in group 1 (319,176+/-39,354 and 5,455+/-652) than in group 2 (202,022+/-23,331 and 3,722+/-468, P<0.04). Islet purity and fragmentation showed no differences between the groups. CONCLUSIONS: The tube method improved islet yields. We recommended this method for human islet isolation.     

Microbial surveillance during human pancreatic islet isolation

OBJECTIVES: The study aim was to investigate the microbiological safety of islet isolation and transplantation. MATERIALS AND METHODS: Between 1996 and 2002, prospective microbiological screening was performed on all pancreata procured for islet transplantation. Pancreas transport media and postpurification preparations were screened for microbiological contamination. Prior to isolation, pancreata were washed with either Hanks solution (group I, n = 170) or decontaminated with antiseptic and antimicrobial drugs (group II, n = 45). RESULTS: Microbiological contamination of the pancreas preservation media was shown in 62%. Analysis of the contaminants showed 74% gram-positive, 21% gram-negative organisms, and 5% fungi. The donor condition or procurement center did not influence the contamination rate. Longer pancreas transport duration was significantly associated with bacterial contamination (P <.05). In group I, 16 (9.4%) of 170 islet preparations presented microbial contamination at the end of the isolation procedures. Gram-positive organisms were present in 10 (6%), gram-negative organisms in 4 (2.4%), and fungi in 2 (1.2%) preparations. Four islet preparations (2.4%) from pancreata with noninfected transport medium were positive on postpurification cultures, all with gram-positive organisms. In group II, only 2 of 45 islet preparations (4.4%) presented microbial contamination at the end of the isolation process. CONCLUSIONS: The rate of microbial contamination during pancreas procurement and transport is high. Significant contaminants present when beginning islet isolation become undetectable by the conclusion of isolation. Diminishing the bio-burden by pancreas decontamination reduces the risk of contamination of the final islet preparation.     

Microbial surveillance during human pancreatic islet isolation

The aim of the study was to investigate microbiological contamination rate during human pancreatic islet isolation. Between 1996 and 2002, pancreas preservation media and post-purification islet preparations were screened for microbiological contamination. After arrival in the laboratory, pancreata were washed prior to enzyme perfusion with either Hank's balanced salt solution (Group I, n = 170, 1996 to 2001) or decontaminated with polyvidonum-iodine, cefazoline, and amphotericine B (Group II, n = 45, 2001 to 2002). Microbiological contamination of preservation media was observed in 56% and 84% for Groups I and II, respectively. Analysis of contaminants revealed 74% Gram-positive, 21% Gram-negative bacteria and 5% fungi. Duration of transport had an influence on the rate of contamination (P < 0.05). After islet isolation, Group I presented microbial contamination of 16 islet preparations (9.4%) [i.e. Gram-positive bacteria (n = 10), Gram-negative bacteria (n = 4), and fungi (n = 2)]. In Group II, only 2 islet preparations (4.4%) presented microbial contamination. Microbial contamination during pancreas procurement occurs frequently. Most microorganisms are eliminated during islet isolation, and de novo contaminations during islet isolation are rare. Pancreas decontamination reduces the risk of infection of the final islet preparation.     

Endogenous pancreatic enzyme activity levels show no significant effect on human islet isolation yield

Despite advances in human islet isolation, islet yield remains inconsistent and unreliable. In recent studies, it has been suggested that serine proteases, in particular trypsin, have been shown to have a damaging effect on islet yield. This study evaluated enzyme activity levels throughout 42 human islet isolation procedures. Trypsin, chymotrypsin, and elastase activity was determined spectrophotometrically using suitable chromophoric substrates. The results of the islet isolations were rated as successful (n = 19) or unsuccessful (n = 23) based on the islet yield and functionality. The enzyme activity profiles of the isolations were compared. No significant differences in donor-related variables were found in this study. However, in the successful isolations, a significantly greater amount (85.6 +/- 1.9%; p = 0.0017) of the pancreas was digested in a significantly shorter digestion time (19.7 +/- 0.6 min; p = 0.0054) compared with 74.8 +/- 2.5% of digested tissue in 22.6 +/- 0.7 min in the poor isolations. This study showed no significant effect of serine protease levels on the outcome of islet isolations, regardless of enzyme inhibitor supplementation. These data suggest that serine protease activity does not sufficiently affect islet yield. However, the data show that the most successful human islet isolations are achieved when the maximum amount of tissue is digested in the shortest amount of time. This suggests that further understanding of the isolation process should focus on the role of the collagenase digestion solution in the dissociation of the endocrine-exocrine tissue connection.     

Influence of neutral protease activity on human islet isolation outcome

Observations in rat pancreata have revealed that enzymatic islet release is mediated by both collagenase and neutral protease (NP), a critical effector of islet integrity. Since no information is available about the effect of NP activity on islet release from the human pancreas, the present study evaluated the effect of various NP concentrations on the outcome of human islet isolation. METHODS: Following intraductal collagenase distension, pancreata obtained from adult multiorgan donors were digested using 2000 PZ-U of purified Serva collagenase NB 1 supplemented with 2.6 (n = 10) or 4.5% (DMC-U/PZ-U) (n = 10) of NP. RESULTS: Increasing NP from 2.6% to 4.5% reduced the amount of undigested tissue from 22 +/- 2 to 17 +/- 2 g (P < .05) while simultaneously increasing the volume of digested tissue (26 +/- 2 vs 40 +/- 3 mL, P < .01). Increased NP concentrations increased the islet yield prepurification (459,800 +/- 22,900 vs 587,600 +/- 69,000 IEQ, P < .05), but simultaneously affected islet purification, resulting in equal islet yields (345,700 +/- 31,200 vs 391,500 +/- 35,400 IEQ, NS) and less purity (70 +/- 6 vs 49% +/- 5%, P < .01). A NP concentration of 4.5% reduced the stimulation index (4.7 +/- 1.2 vs 2.0 +/- 0.5, P < .01) and viability (100 +/- 1 vs 95% +/- 3%, P < .05). CONCLUSIONS: Although increased NP activity seems to improve islet release from adult human pancreata, it significantly affects islet viability and function. The reduction in purity reflected damage to acinar tissue by increased NP activity presumably affecting islet integrity.     

国产胶原酶在小鼠胰岛分离中的效果研究#br#

目的 研究一种国产胶原酶在小鼠胰岛分离中的分离效果,探索该胶原酶在胰岛分离中应用的 可行性。方法 将国产胶原酶分别配成不同浓度的胶原酶溶液和含中性蛋白酶的胶原酶的溶液,经胰管逆行灌注胶原酶的方法进行小鼠胰岛分离,采用Ficoll液对胰岛进行纯化,计数所得的胰岛细胞团,培养 6 h后检测活性,对最佳分离结果的胰岛做同系糖尿病小鼠的肾被膜下移植,监测术后血糖和进行组织学 检查,以进口Sigma胶原酶V为对照。结果 国产胶原酶在小鼠胰腺消化时间、所得胰岛数量和活性效果 上跟进口胶原酶V有一定差距（P＜0.01）,但含中性蛋白酶的国产胶原酶组在小鼠胰岛分离数量和当量上 与进口胶原酶组无差异（P＞0.05）,分离的胰岛在体内移植后降血糖效果与进口胶原酶组无差异（P＞0.05）。 结论 国产胶原酶结合中性蛋白酶可用于小鼠胰岛的分离。     

Serva collagenase NB1: a new enzyme preparation for human islet isolation

INTRODUCTION: Advances in the rate of success of human islet isolation are due in part to the availability of new purified enzyme blends. In this study we evaluated a new enzyme preparation composed of a highly purified collagenase that can be reproducibly blended with predetermined amounts of separately packaged neutral protease. METHODS: Nine human islet isolations were performed with collagenase NB1 supplemented with neutral protease (Serva Electrophoresis GMbH, group I). Yields, purity, morphology, in vitro function and islet cell apoptosis were assessed. The results were compared to those of nine human islet isolations performed with Liberase (Roche, group II) and matched for donor age, BMI, and circumstances of death. RESULTS: Islet yields were similar in both groups. However, islet equivalents (IE) per gram of pancreas and IE number to islet number were higher in group I (P <.05). Stimulation indices after insulin response to glucose (static incubation) were similar in both groups. Islet cell apoptosis rate was statistically significantly lower in group I. Islet morphology was significantly improved in group I with a higher proportion of intact islets. CONCLUSION: This new enzyme preparation (collagenase NB1 with neutral protease adjunct) was as effective as Liberase in terms of islet yields and function. Islet morphology was improved and rate of islet cell apoptosis was lower with this new collagenase. The absence of lot-to-lot variability in terms of neutral protease to collagenase ratio makes collagenase NB1 a promising enzyme for human islet isolation.     

Detection of microbial contamination during human islet isolation

Current good manufacturing practice (cGMP) islet processing facilities provide an ultraclean environment for the safe production of clinical grade islets for transplantation into immunosuppressed diabetic recipients. The objective of this study was to monitor the rate of microbial contamination in islet products after implementation of good manufacturing practice conditions. Fluid samples for microbial contamination were collected at the following steps: from the pancreas transport solution upon arrival of the organ (n=157), after surface decontamination of the pancreas with antiseptic agents (n=89), from islet supernatant at the end of the isolation (n=104), and from islet supernatant as a final transplantable product after culture (n=53). Bacterial, fungal, and mycoplasma cultures were conducted for 2, 2, and 3 weeks, respectively. Microbial contamination was detected in 31% of transport solution. The contamination was not associated with the presence of the duodenum during the preservation, cold ischemia time, or procurement team (local vs. distant). Surface decontamination of the pancreas resulted in clearance of 92% of the microbial contamination. Six preparations at the end of the isolation revealed microbial growth. All were de novo contamination during the processing. Fifty-three preparations that met our release criteria in terms of product sterility were transplanted into type 1 diabetic patients. In two instances, positive culture of the islet preparation was reported after transplantation had occurred. No patient showed any clinical findings suggestive of infection or any radiological abnormalities suggestive of abscess; a single dose of antibiotic coverage was given routinely to recipients prior to islet infusion. Although transport solution carries a high risk of microbial contamination, most contaminants become undetectable during islet processing. Microbial contamination in final products is rare, but de novo contamination still occurs during processing even under cGMP conditions.     

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.     

Characterization of collagenase blend enzymes for human islet transplantation

BACKGROUND: Efficient islet isolation represents a necessary requirement for successful islet transplantation as a treatment for type 1 diabetes. The choice of collagenase for pancreas digestion is critical for the isolation outcome, and Liberase is the most widely used enzyme, although large intra-batched variability in activity and efficiency has been observed. METHODS: The aim of this study was to characterize Liberase components and their relative role in pancreas digestion. Liberase batches were characterized by microelectrophoresis. RESULTS: By means of microelectrophoresis, we identified three main proteins each with different prevalences between batches. Two proteins were found to correspond to class I (CI) and one to class II (CII) collagenase. In a series of 163 islet isolations, we observed that the CII correlated with islet yield (P<0.001) and digestion time (P<0.001); additionally, CI directly correlated with purity (P=0.028). Finally, when CII and one of the CI isoforms were >50 percentile, 15 of 36 preparations were transplanted, with 27 of 127 transplanted in the other cases (P=0.013). CONCLUSION: These results represent an important step toward the characterization of enzymes, with the final aim of identifying key components for a standardized product.     

Adjustment of the ratio between collagenase class II and I improves islet isolation outcome

BACKGROUND: Previous studies have clarified the distinct roles of collagenase class I (ccI) and class II (ccII) in enzymatic release of islets from pancreatic tissue. The present study sought to enhance the limited knowledge about the optimal ratio between collagenase classes. METHODS: Rat islets were isolated utilizing 0.4 DMC-U of neutral protease and 20 PZ-U of fractionated NB-1 collagenase recombined to obtain a ccII/I ratio of 0.5, 1.0, and 1.5. Quality control included assessment of yield (islet equivalents), trypan-blue exclusion, insulin release during static glucose incubation, and transplant function in diabetic nude mice. Data are expressed as mean values +/- SEM. RESULTS: Digestion time was only minimally influenced by different ccII/I ratios. The highest islet yield (P < .05) was obtained using a ccII/I ratio of 1.0. Purity and glucose stimulation index were only marginally affected by different ccII/I ratios. A significant loss of islet viability after 24-hour culture (P < .05) was observed only in islets isolated by means of a ccII/I ratio of 0.5 and 1.5 but not 1.0. Transplantation into diabetic nude mice revealed sustained islet graft function in all experimental groups. CONCLUSIONS: The present study indicates that the ratio between ccII and ccI is of significant relevance for optimizing islet yield and viability.     

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.     

Deterioration and variability of highly purified collagenase blends used in clinical islet isolation

BACKGROUND: The quality and stability of enzyme blends used in islet cell processing are critical for successful human islet isolation. A wide variability in enzymatic activity among lots of Liberase HI has been reported. This study examines the interlot and intralot variability of Liberase HI and the over-time deterioration of enzyme quality based on the analysis of islet isolation outcomes. METHODS: The data of 169 human isolations processed for clinical islet transplantation, using five different lots of Liberase HI, were retrospectively analyzed. Inter- and intralot variables in the islet isolation were assessed over a 15-month period. RESULTS: The analysis revealed significant interlot differences in the digestion time, prepurification islet counts, percent recovery, viability, and glucose stimulation insulin index. Moreover, a significant decrease in the pre- and postpurification islet yield per pancreas weight (IEQ/g) in isolations processed by two different enzyme lots used over a 15-month period was observed, suggesting a progressive deterioration of enzyme quality. CONCLUSIONS: Our data demonstrate a significant lot-to-lot related variability in islet isolation outcomes. In addition, the over-time decline in isolation outcomes processed using a single enzyme lot was observed even when the enzyme blends were used within the expiration dating specified by the manufacturer.     

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.     

Donor and isolation variables predicting human islet isolation success

BACKGROUND: Recent advances in the fields of islet transplantation and in vitro islet cell expansion place a renewed emphasis on the optimization of islet isolation from cadaveric human donor organs. We retrospectively analyzed 171 islet isolations to identify variables that predict islet yield and isolation success. METHODS: Cadaveric human donor pancreata were procured and processed according to established protocols. Donor-, procurement-, and isolation-related variables were analyzed for correlation with islet yield and isolation success (> or =250,000 islet equivalents). RESULTS: Univariate analysis suggested correlations between islet yield and donor age (P<0.005), body surface area (P<0.005), duration of enzymatic digestion (P<0.001), and pancreatic beta-cell volume (P<0.05). Donor sex (P<0.01), procurement team (P<0.05), and peridigestion serine protease inhibition (P<0.05) affected islet yield, whereas enzyme lot (P<0.01) and pancreatic fatty infiltration (P<0.05) influenced isolation success. By logistic regression, donor sex and age, and duration of enzymatic digestion could predict a successful isolation with 72% accuracy. The use of Liberase CI improved islet yield (P<0.05) in young donors (< or =25 years). CONCLUSIONS: While donor-related variables are useful in predicting islet yield, these are likely surrogates for pancreatic beta-cell volume. Enzyme lot, and the associated duration of enzymatic digestion (P<0.05), appears to be key determinants of isolation success.