Testing combinations of protease inhibitor and preservation solution to improve islet quality and yield

Pancreas preservation using an oxygenated two-layer method (TLM) has been reported to improve islet yields, as has supplementation of Liberase with Pefabloc. We hypothesized that using both TLM and Pefabloc could enhance islet yield as compared with preservation in University of Wisconsin (UW) or Histidine-Tryptophan Ketoglutarate (HTK) solution. METHODS: Ninety-eight pancreata with no significant differences of age, body mass index, or cold ischemia time preserved randomly with UW (n = 40), TLM (n = 48), or HTK (n = 10) were processed with (n = 36) or without (n = 66) Pefabloc. RESULTS: The total islet equivalent (IEQ) from TLM-preserved pancreata processed with Pefabloc (n = 12) showed lower yields versus those processed without Pefabloc (n = 36): 216,120 +/- 27,906 vs. 301,427 +/- 21,447 IEQ (P < .05). Islets from 1 of 12 (8.33%) pancreata processed with Pefabloc in TLM were transplanted, in contrast with 15/36 TLM (41.67%) pancreata processed without it. Islet yields were not significantly different among pancreata preserved in UW and processed with Pefabloc (n = 17) versus without Pefabloc (n = 23): 342,693 +/- 45,588 versus 266,609 +/- 29,006 IEQ (P = .149). The number of transplants from UW-preserved pancreata was 3/17 (17.65%) when processed with Pefabloc and 4/23 (17.39%) without. Among the HTK group, there was no significant difference in islet yields between pancreata processed with (n = 7) versus without Pefabloc (n = 3): 248,227 +/- 65,294 versus 483,555 +/- 144,070 IEQ (P = .118). CONCLUSIONS: Pefabloc showed no benefit to improve islet yields. Pancreata preserved in TLM provided better transplant quality islets when processed in the absence of Pefabloc.     

Pancreas storage in oxygenated perfluorodecalin does not restore post-transplant function of isolated pig islets pre-damaged by warm ischemia

BACKGROUND: Cold storage in oxygenated perfluorodecalin (PFD) restores transplant function of ischemically damaged dog pancreata and reduces the impact of cold ischemia on recovery of isolated human islets. Whether PFD storage can improve islet isolation from pancreata exposed to significant warm ischemia (WI) is unclear yet. The present study aimed to clarify this question in adult pigs. METHODS: After exsanguination, the intestine was removed immediately or left in the cavity for 30 min of WI. Resected pancreata were intraductally flushed with cold University of Wisconsin solution. Subsequently, pancreata were processed immediately by digestion-filtration (group I: 0 min WI, n=6; II: 30 min WI, n=6) or first stored for 3 h in oxygenated PFD (III: 0 min WI+PFD, n=5; IV: 30 min WI+PFD, n=6). RESULTS: Pancreata subjected to 30 min of WI yielded significantly less islets compared with the corresponding non-ischemic organs (I vs. II, P<0.01; III vs. IV, P<0.05). Oxygenation did not ameliorate the loss in islet yield (II vs. IV, NS). Ischemic islets were characterized by depleted ATP stores (388+/-73 (I) vs. 133+/-22 ng/1000 IEQ (II), P<0.01) and diminished insulin response to glucose calculated as stimulation index (SI; 2.47+/-0.36 (I) vs. 0.25+/-0.17 (II), P<0.05). PFD storage of ischemic organs partially restored ATP content (217+/-23 ng/1000 IEQ, II vs. IV, P<0.05) and glucose SI (1.60+/-0.09, II vs. IV, P<0.05) to a significant extent that reached the level of corresponding PFD-stored, non-ischemic pancreata (III vs. IV, NS). Sustained normoglycemia was exclusively observed in diabetic nude mice transplanted with islets isolated from non-ischemic organs. The significantly reduced graft function of ischemic islets (I vs. II, III vs. IV, P<0.001) was not increased by pancreatic oxygenation (II vs. IV, NS). CONCLUSIONS: The present study suggests that pancreas short-term storage in oxygenated PFD improves in vitro but not the in vivo function of ischemically damaged pig islets.     

Adaption of neutral protease activity for islet isolation from the long-term two-layer method-stored pig pancreas

BACKGROUND: Islet release from the pancreas is mediated by both collagenase and neutral protease (NP), a critical effector of islet integrity. To prove the hypothesis that adjustment of NP reduces islet damage after prolonged ischemia, adult pig pancreata were digested after 7-hour preservation by the two-layer method (TLM) using a 2-component enzyme blend consisting of collagenase NB-8 and NP. METHODS: After intraductal University of Wisconsin (UW) flush resected pancreata were distended with 4.4 PZ-U/g of UW-dissolved Serva collagenase either before (TLM-preloaded, n = 7) or after (TLM-postloaded, n = 10) cold storage, or for immediate processing (n = 6). NP was adjusted after preliminary experiments to respectively 1.1, 0.2, or 0.8 DMC-U/g for unstored, TLM-preloaded, or postloaded organs. RESULTS: Purified islet yield decreased from 3670 +/- 730 islet equivalents (IEQ)/g in unstored pancreata to 1800 +/- 180 and 2080 +/- 290 IEQ/g in TLM-preloaded or postloaded organs, respectively (P < .05). Although purity was always >90%, IEQ recovery was significantly decreased in TLM-preloaded pancreata. Quality control revealed consistently high viability as determined using trypan-blue exclusion (>95%) or formazan production. Compared with unstored organs (2.47 +/- 0.36; P < .05), glucose stimulation index was reduced in TLM-preloaded (1.48 +/- 0.15) and TLM-postloaded pancreata (1.81 +/- 0.20). Normoglycemia in diabetic nude mice transplanted with islets from TLM-preloaded pancreata was transient in contrast to sustained function in the other groups. CONCLUSIONS: Significant amounts of viable pig islets can be isolated after prolonged TLM preservation by reducing NP activity. Nevertheless, early enzyme administration prior to long-term storage deteriorates islet graft function.     

Improved Islet Yields From Macaca Nemestrina and Marginal Human Pancreata After Two-Layer Method Preservation and Endogenous Trypsin Inhibition

We tested whether two-layer method (TLM) pancreas preservation and trypsin inhibition (Pefabloc) during processing allows longer preservation while retaining or improving viable islet recovery. Non-marginal primate (Macaca nemestrina) and marginal human (ischemic or preservation-injured) pancreata were processed with a research-oriented pan technique (Seattle method). Organs were processed upon arrival (+/- Pefabloc), or after TLM or University of Wisconsin solution (UW) preservation (+ Pefabloc). Islet yield, viability, and function were assessed. Pefabloc increased M. nemestrina islet yields from 9696 +/- 1749 IE/g to 15 822 +/- 1332 IE/g (p < 0.01). Two-layer method preservation (< 6 h) further increased yields, to 23 769 +/- 2773 IE/g (vs. + Pefabloc; p < 0.01). Similarly, Pefabloc increased marginal human islet yields from 2473 +/- 472 IE/g to 4723 +/- 1006 IE/g (p < 0.04). This increase was maintained after lengthy TLM preservation (> 30 h; 4801 +/- 1066 IE/g). We also tested the applicability of TLM preservation (23.5 +/- 3.2 h) to the processing of marginal human pancreata by the Edmonton/Immune Tolerance Network clinical protocol. Islet yield and function approached published results of pancreata processed 4.8 +/- 0.8 h after organ recovery (p = 0.06). Pefabloc, and TLM vs. UW preservation, prolonged the tolerable interval between organ recovery and islet isolation. Islet yield, viability, and functionality improved from both marginal and nonmarginal pancreata.     

Two-layer method in short-term pancreas preservation for successful islet isolation

BACKGROUND: We sought to determine whether the two-layer method (TLM) offers advantages over UW storage solution for locally procured pancreata with cold ischemia time of <8 hours for successful islet isolation. METHODS: From October 2003 through February 2005, 22 human pancreata were procured locally from cadaveric donors and preserved using UW solution (n = 11) or TLM (n = 11). RESULTS: Donor characteristics were similar in the two groups, with no statistical difference. Cold ischemia time was 4.5 +/- 0.6 (2.5 to 8) hours in the UW and 5.1 +/- 0.5 (3 to 8) hours in TLM group (P > .05). Organs preserved with TLM were exposed to PFC for 4 +/- 0.5 (2 to 7.5) hours. After TLM preservation, 8 of 11 (72%) pancreata yielded >300,000 IEQ pancreatic islets, which met all criteria for clinical transplantation; after UW cold storage, only 3 of 11 isolations were equally successful (27%) (P < .05). Mean IEQ was higher in the TLM than in the UW group: 349,000 +/- 37,000 vs 277,800 +/- 34,000; IEQ/g was also higher at 5100 +/- 760 vs 3000 +/- 570, respectively (P < .05). Islet quality, characterized by purity, viability, and insulin SI, did not differ statistically in the two groups: 67 +/- 4 vs 74 +/- 4%, 87 +/- 2 vs 83 +/- 4%, and 4 +/- 0.7 vs 4.8 +/- 1, respectively (P > .05). CONCLUSIONS: The Two Layer Method for locally procured human pancreata with cold ischemia time lower than 8 hours offers significant advantage over UW cold storage increasing the pancreatic islet isolation yield and the isolation success rate.     

Influence of preservation solution on human islet isolation outcome

BACKGROUND: The influence of the preservation solution used for in situ perfusion of the donor and pancreas storage on islet isolation has received little attention. METHODS: In this prospective controlled trial, we compared the outcome of human islet isolation from pancreata perfused with University of Wisconsin (UW) solution or Celsior, an alternative colloid-free extracellular solution. RESULTS: At the 1-year interim analysis, the viability and insulin secretion of islets isolated from donors perfused with UW (n=19) or Celsior (n=5) were identical. However, total islet recovery (IEQ) and isolation yield (IEQ/g) were 1.8-fold and 2.1-fold inferior in the Celsior group (P<0.05 vs. UW). Overall, 13 (68%) of islet preparations were effectively transplanted from the UW group vs. none from the Celsior group (P=0.01). The clinical study was discontinued and the causes of these differences were further explored in the pig (n=14). In contrast to UW, Celsior induced cell swelling and pancreas edema after only four hours of cold storage. These abnormalities were delayed when the donor was perfused with Solution de Conservation d'Organes et de Tissus (SCOT), an extracellular solution containing polyethylene glycol. CONCLUSIONS: Our results suggest that colloid-free preservation solutions might be suboptimal for pancreas perfusion and cold storage prior to islet isolation and transplantation. Because pancreata are now frequently recovered for islet transplantation, preliminary experimental and clinical data about islet isolation should be obtained prior to the routine implementation of new preservation solutions for abdominal perfusion during multiorgan recovery.     

Improved Human Islet Isolation Using Nicotinamide

We investigated the effects of nicotinamide (NA) supplementation of the processing medium during islet isolation. One hundred and two human pancreata were processed for clinical transplantation after preservation either in the University of Wisconsin (UW) or using the two-layer method (TLM). Pancreata were then divided into four groups and retrospectively analyzed. Group I: UW preservation followed by processing without NA, Group II: UW preservation and processing with NA, Group III: TLM preservation without NA, Group IV: TLM preservation with NA. We observed a significant increase in islet yield in Group II (4343+/-348 IEQ/g) [mean+/-SEM], compared to Group I (2789+/-348 IEQ/g) (p=0.005). Similarly, a significant increase in islet yield was observed when NA was used in the processing of organs preserved with TLM (Group IV: 5538+/-413 vs. Group III: 3500+/-629; p=0.02). Furthermore islet yield was higher in Group IV than in Group II (p<0.05). The percentages of preparations that qualified for transplantation were 25, 47, 45, 69% in Groups I, II, III, IV, respectively. Addition of NA to the processing medium significantly improved islet yields in both the UW and TLM preservation protocols, allowing for a higher percentage of islet preparations to qualify for clinical transplantation.     

Significant progress in porcine islet mass isolation utilizing liberase HI for enzymatic low-temperature pancreas digestion.

BACKGROUND: Frequent success in human islet isolation is prevented by the large variability of scarce organ donors; this favors the future utilization of pigs as donors for clinical islet xenotransplantation. Porcine-specific difficulties of islet isolation are attributed to the intrinsic fragility of islets during pancreas digestion. METHODS: To preserve islet integrity during efficient pancreas dissociation, porcine pancreata (n=48) were distended after cold storage with cold University of Wisconsin solution containing Liberase HI and digested at 24-28 degrees C using digestion-filtration. Pancreata distended with University of Wisconsin solution containing well-proven crude collagenase and digested at 32-34 degrees C served as controls (n=46). Monolayer Ficolldiatrizoate gradient purification was performed in a Cobe 2991. RESULTS: Purified yield of islet equivalents per pancreas (mean+/-SEM) was almost doubled by Liberase HI compared with crude collagenase (526,480+/-46,560 vs. 270,270+/-19,420; P < 0.0001) and also significantly increased comparing islet equivalents per gram of pancreas (4,210+/-320 vs. 2,640+/-245; P=0.0004). Islet integrity was better preserved during Liberase HI digestion compared with crude collagenase digestion as indicated by isolation index (2.1+/-0.1 vs. 1.4+/-0.1; P<0.0001). Purity, viability, and in vitro function of islets did not differ between experimental groups. Preserved in vivo function of islets isolated by Liberase HI was demonstrated after subcapsular transplantation into 16 diabetic nude rats. CONCLUSIONS: If the problems related to xenograft rejection and xenosis could be solved, low-temperature digestion of porcine pancreata using Liberase HI could serve as an essential prerequisite for successful 1:1 xenotransplantation of pig islets into type 1 diabetic human recipients.     

Successful pancreas preservation by a perfluorocarbon-based one-layer method for subsequent pig islet isolation

BACKGROUND: The oxygenation of human pancreas by the two-layer method (TLM) during cold storage was recently established for clinical islet transplantation. Simplification of TLM would facilitate the application of perfluorocarbon (PFC) as a regularly used preservation solution for subsequent islet transplantation. The present study examined whether PFC can be used in a one-layer method (OLM) for long-term pancreas preservation before isolation of adult pig islets. METHODS: Resected pancreases were intraductally flushed with cold University of Wisconsin solution and immediately processed (n=6) or subjected to 7-hour storage by OLM (n=8) or TLM (n=10). Subsequently, pancreases were intraductally distended with collagenase NB-8 supplemented with neutral protease. Isolation and purification were performed as previously described. RESULTS: Compared with unstored pancreases (3,670+/-740 islet equivalents [IEQ]) purified islet yield in TLM-stored organs (2,080+/-290 IEQ, P<0.05) was significantly decreased in contrast with OLM-preserved pancreases (3,110+/-520 IEQ, NS). No differences were observed between groups regarding purity (>90%), trypan-blue exclusion (>95%), adenosine triphosphate content, and mitochondrial viability of islets. Stimulation index during static glucose incubation (20 vs. 2.8 mm) was decreased after storage by TLM (1.81+/-0.20, P<0.05) but not by OLM (2.27+/-0.57) if compared with unstored pancreases (2.47+/-0.36). However, transplantation into diabetic nude mice resulted in sustained normoglycemia of recipients of either group until nephrectomy of graft-bearing kidneys was performed. CONCLUSIONS: This study demonstrates that PFC alone can be used in a one-layer procedure for successful pig-pancreas preservation. This simplification can facilitate the broad application of PFC as pancreas preservation solution without reducing its benefits demonstrated by TLM.     

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.     

Pulsatile pump perfusion of pancreata before human islet cell isolation

Machine pulsatile perfusion for whole pancreas preservation might improve yield, viability, and function of human islets recovered after prolonged cold ischemia times. Four human pancreata were procured from cadaver donors (1 non-heart-beating donor) and stored in cold University of Wisconsin (UW) solution for a mean 13 hours prior to placement on a machine pulsatile perfusion device. The four pancreata were perfused for 4 hours with UW solution before undergoing islet isolation. Islets were quantified, viability was assessed, and insulin secretion was measured. Results were compared with nonpumped islet isolations stratified for cold ischemia time (CIT) <8 hours or cold ischemia time >8 hours. The islet yield for the four pumped pancreata was 3435 (+/-1951) islet equivalents/gram pancreas tissue (IEQ/g), compared with a mean yield of 5134 (+/-2700) IEQ/g and 2640 (+/-1000) IEQ/g from pancreas with <8 hours and >8 hours CIT, respectively. The mean viability after machine pulsatile perfusion was 86% (vs 74% and 74% for the <8 hour and >8 hour CIT groups). The mean viable yield (total yield x viability) was 2937 IEQ/g for machine perfusion, compared with 3799 IEQ/g and 1937 IEQ/g from pancreata with <8 hours and >8 hours CIT, respectively. The insulin secretion index of islets after machine perfusion was 6.4, compared with indices of 1.9 and 1.8 for the <8 hour and >8 hour CIT groups. This preliminary data indicates that low-flow machine pulsatile perfusion of pancreata with prolonged cold ischemia time can result in excellent yield, viability, and function.     

Intra-Ductal Glutamine Administration Reduces Oxidative Injury During Human Pancreatic Islet Isolation

Oxidative stress during islet isolation induces a cascade of events injuring islets and hampering islet engraftment. This study evaluated islet isolation and transplantation outcomes after intra-ductal glutamine administration. Human pancreata deemed unsuitable for pancreas or islet transplantation were treated with either a 5 mM solution of l-glutamine (n = 6) or collagenase enzyme alone (n = 6) through the main pancreatic duct. Islet yield, viability, in vitro function; markers of oxidative stress [malondialdehyde (MDA) and Glutathione (GSH)] and apoptosis were assessed. Islet yields were significantly increased in the glutamine group compared to controls (318, 559 +/- 25, 800 vs. 165, 582 +/- 39, 944 mean +/- SEM, p < 0.01). The amount of apoptotic cells per islet was smaller in the glutamine group than the control. The percentage of nude mice rendered normoglycemic with glutamine-treated islets was higher than the controls (83% n = 10/12 vs. 26% n = 6/23; p < 0.01), and the time to reach normoglycemia was decreased in the glutamine group (1.83 +/- 0.4 vs. 7.3 +/- 3 days; p < 0.01). Glutamine administration increased GSH levels (7.6 +/- 1.7 nmol/mg protein vs. 4.03 +/- 0.5 in control, p < 0.05) and reduced lipid-peroxidation (MDA 2.45 +/- 0.7 nmol/mg of protein vs. 6.54 +/- 1.7 in control; p < 0.05). We conclude that intra-ductal administration of glutamine reduces oxidative injury and apoptosis and improves islet yield and islet graft function after transplantation.     

Improvement of pancreatic islet isolation outcomes using glutamine perfusion during isolation procedure

During procurement, isolation, and transplantation, islets are exposed to high levels of oxidative stress triggering a variety of signaling pathways that can ultimately lead to cell death. Glutamine is an important cellular fuel and an essential precursor for the antioxidant glutathione. The aim of this study was to examine the role of intraductal glutamine administration in facilitating recovery of isolated rat islets from pancreases subjected to a clinically relevant period of warm ischemia. Islets were isolated in Sprague-Dawley (SD) rats (n = 18 per group). Pancreata in groups 1 and 2 were procured immediately while groups 3 and 4 were subjected to 30-min warm ischemia. Groups 2 and 4 were treated intraductally with 5 mM glutamine prior to pancreatectomy. Exposure to 30-min warm ischemia significantly reduced islet yield [groups 1 & 2 (nonischemia): 503 +/- 29 islets/rat vs. groups 3 & 4 (ischemia): 247 +/- 26 islets/rat; p < 0.05]. Intraductal glutamine treatment significantly improved islet yield when pancreata were subjected to 30-min warm ischemia [144 +/- 16 islets/rat without glutamine (group 3) vs. 343 +/- 36 islets/rat with glutamine (group 4), p < 0.05]. Glutamine also significantly improved islet viability (values were 50 +/- 4% in group 4 vs. 27 +/- 3% in group 3, p < 0.05). Similarly, glutathione (reduced) levels were significantly elevated in both glutamine-treated groups; however, this increase was greatest in tissues exposed to ischemia (2.76 +/- 0.04 nmol/mg protein in group 4 vs. 1.66 +/- 0.04 nmol/mg protein in group 3, p < 0.05). Intraductal glutamine administration considerably improves the islet yield, viability, and augments endogenous glutathione levels in pancreata procured after a clinically relevant period of ischemia. Intraductal administration of glutamine at the time of digestive enzyme delivery into the harvested pancreas may represent a simple yet effective tool to improve islet yields in clinical isolations.     

Improvement of Human Islet Cryopreservation by a p38 MAPK Inhibitor

The activation of p38 mitogen-activated protein kinase (MAPK) has been shown to cause ischemia/reperfusion injury of several organs used for transplantation and also to play a significant role in primary islet graft nonfunction. Activation of p38 MAPK may also occur during islet cryopreservation and thawing. In this study, a p38 MAPK inhibitor (p38IH) was applied to human islet cryopreservation to improve islet yield and quality after thawing. Under serum-free conditions, human islets were cryopreserved, thawed and cultured using our standard procedures. Three types of solutions were tested: conventional RPMI1640 medium (RPMI), a newly developed islet cryopreservation solution (ICS), and ICS supplemented with a p38IH, SD-282 (ICS-p38IH). Activation or inhibition of p38 MAPK was demonstrated by the diminished phosphorylation of HSP27 substrate. Islet recovery on day 2 after thawing was highest with ICS-p38IH and islet viability was not significantly different in the three groups. beta Cell numbers and function were the highest in islets cryopreserved with ICS-p38IH. Glucose-stimulated human C-peptide levels were 86% of that of the nonfrozen islets when measured 4 weeks after transplantation into NODscid mice. This improvement may provide an opportunity to establish islet banks and allow the use of cryopreserved islets for clinical transplantation.     

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.     

Influence of collagenase loading on long-term preservation of pig pancreas by the two-layer method for subsequent islet isolation

BACKGROUND: The introduction of the two-layer method (TLM) for long-term human pancreas preservation revealed the enormous potential of TLM to improve graft function of isolated islets. It is still unclear whether pig islets can be successfully isolated from pancreases after prolonged cold ischemia. To clarify this question, pig pancreases were subjected to 7-hour preservation by University of Wisconsin solution (UWS) storage or TLM. Another aim was to verify whether TLM can be synergistically combined with intraductal collagenase injection before cold storage. METHODS: After intraductal flush with UWS, organs were distended with 4.4 PZ-U/g of UWS-dissolved collagenase NB-8 and neutral protease adjusted to respectively 1.1, 0.2, 0.5, or 0.8 DMC-U/g for pancreases freshly procured (n=6) or distended with enzymes before (TLM preloaded, n=7) or after cold storage (UWS storage, n=4; TLM postloaded, n=10). RESULTS: Purified islet yield decreased from 429,200+/-86,700 islet equivalents (IEQ) in unstored pancreases to respectively 37,670+/-19620, 210,400+/-22900 and 238,000+/-26600 IEQ in UWS-stored (P<0.01), TLM-preloaded, or postloaded organs (P<0.05). Purity (>90%), viability (>95%), and insulin content were not different between groups. Islets from UWS-stored pancreases fragmented extensively, preventing further assessment of in vivo function. Compared with other experimental groups, islets from TLM-preloaded organs were characterized by enhanced basal and stimulated insulin release. Sustained normoglycemia was observed in diabetic nude mice transplanted with islets from TLM-postloaded or unstored pancreases in contrast with transient function in TLM-preloaded islets. CONCLUSIONS: This study demonstrates that significant amounts of intact pig islets can be isolated after prolonged pancreas preservation by TLM. Enzyme administration before TLM preservation decreases islet graft function.     

The morphology of islets within the porcine donor pancreas determines the isolation result: successful isolation of pancreatic islets can now be achieved from young market pigs

Clinical islet allotransplantation has become an increasingly efficient "routine" therapy in recent years. Shortage of human donor organs leads to porcine pancreatic islets as a potential source for islet xenotransplantation. Yet it is still very difficult to isolate sufficient numbers of intact porcine islets, particularly from young market pigs. In the following study islets were successfully isolated from retired breeders [4806 +/- 720 islet equivalents per gram organ (IEQ/g); n = 25; 2-3 years old; RB] and also from young hybrid pigs [2868 +/- 260 IEQ/g; n = 65; 4-6 months old; HY] using LiberasePI and a modified version of Ricordi's digestion-filtration technique. As expected, isolations from RB showed significantly better results (p < 0.002). A retrospective histological analysis of almost all donor pancreases showed that the majority of organs from RB (80%) contained mainly large islets (diameter > 200 microm), in contrast to only 35% of all pancreases from HY. Remarkably, the islet size in situ, regardless whether detected in RB or HY, strongly determined the isolation result. A donor organ with predominantly large islets resulted in significantly higher numbers of IEQs compared with a donor organ with predominantly small islets [RB(Large Islets): 5680 +/- 3,318 IEQ/g (n= 20); RB(Small Islets): 1353 +/- 427 IEQ/g (n = 5); p < 0.02]. In addition, isolation results were strongly influenced by the quality of the LiberasePI batch, and therefore single batch testing is invariably required. Purification was performed using Ficoll or OptiPrep density gradient centrifugation manually or in the COBE cell processor. Although islet purity was highest when OptiPrep was used, final islet yields did not differ between the different purification methods. Our study demonstrates that islet size in situ is an extremely critical parameter for highly successful islet isolation; consequently, we are now performing a morphological screening of each donor organ prior to the isolation process. Under these conditions highly successful isolations can reliably be performed even from young market pigs.     

Improved pancreatic islet isolation outcome in autologous transplantation for chronic pancreatitis

Total or partial pancreatectomy followed by autologous islet transplantation is a therapeutic option for the treatment of refractory chronic pancreatitis (CP). Maximization of islet yields from fibrotic and inflamed organs is crucial for prevention of posttransplant diabetes. We adapted technical advancements developed for islet allotransplantation toward islet autotransplantation. Eight patients (two men, six women; ages 24-58 years) underwent total (n = 7) or partial (n = 1) pancreatectomy for the treatment of CP refractory to maximal medical management. Pancreata were preserved in UW solution (UW group) in initial three cases and the last five pancreata were preserved with pancreatic ductal injection followed by ET-Kyoto/oxygenated PFC solutions (DI+TLM group). Islets were isolated by modified Ricordi method and were purified only in one case. All islet infusions were performed under general anesthesia via direct vein injection into the portal venous system with pressure monitoring. Total islet yields (129,314 ± 51,627 vs. 572,841 ± 116,934 IEQ, p < 0.04), islet yield/pancreas weight (1,233 ± 359 vs. 6,848 ± 847 IEQ/g, p < 0.003), and islet yield/patient body weight (1,951 ± 762 vs. 7,305 ± 1,531 IEQ/kg, p < 0.05) were significantly higher in the DI+TLM group when compared to the UW group. Pellet size was also higher (5.3 ± 0.3 vs. 13.5 ± 3.4 ml) in the DI+TLM group, suggesting that this method of preservation effectively protected pancreatic tissue against autolysis. First month posttransplant basal C-peptide and the secretory unit of islet transplant objects (SUITO) index were also higher in the DI+TLM group when compared to the UW group (2.0 ± 0.3 vs. 1.4 ± 0.4 ng/ml and 42.6 ± 12.7 vs. 14.6 ± 5.6, respectively). There were no technical complications related to the infusion. Our results suggest that higher islet yields can be achieved even from chronically inflamed and fibrotic organs using DI+TLM. The techniques applied for islet isolations from normal pancreata are showing promise for fibrotic pancreata from CP patients.     

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.     

Inhibition of p38 mitogen-activated protein kinase protects human islets from cryoinjury and improves the yield, viability, and quality of frozen-thawed islets

The development of an optimal islet cryopreservation method will permit transplantation of islets from multiple donors in a single procedure and contribute to alleviation of the islet shortage. In this study, we have improved human islet cryopreservation methods under serum-free conditions using an intracellular-based islet cryopreservation solution (ICS), especially supplemented with a p38 pathway inhibitor (p38IH) to suppress p38 mitogen-activated protein kinase (MAPK) activation. Three different solutions were compared for freezing and thawing of human islets (1) conventional RPMI1640 medium, (2) ICS, and (3) ICS supplemented with a p38IH, SD-282 (ICS-p38IH). Islet cryopreservation with ICS-p38IH significantly improved islet recovery, viability, and quality after thawing of cryopreserved islets. This improvement may allow the use of cryopreserved islets in clinical islet transplantation.