Islet Cell Yield Research Articles

Isolation of Human Pancreatic Islets from the Indian Population - Unveiling the Synergistic Interplay between different blends of Collagenases and Neutral Proteases

Innovative and effective therapeutic approaches for diabetes such as islet cell transplantation are much needed as diabetes increases the risk of heart failure. In India, the success rate of human clinical islet transplantation (allo-or auto-) mandates sufficiency of functional islets from the pancreas of either brain-dead or chronic pancreatitis donors. Human islet transplantation outcome is significantly affected by collagenases, which decides the yield and quality of isolated pancreatic islet cells. Comparison of collagenase blends carried out in a few islet transplantation centers yields conflicting results for islet quantity and quality. Therefore, we have researched on the right blend of enzymes to achieve an efficient pancreatic islet release, first-ever in Indian population. Our prospective approach evaluated the outcome of islet isolations performed in humans with three different collagenases, namely Serva Collagenase NB1, Roche Liberase and Vitacyte supplemented with Neutral Protease NB. Eight brain-dead humans served as organ donors for pancreatic islet isolation. We modified the islet isolation method to test these three new enzymes using the traditional split pancreas methodology. The islet isolation outcomes were compared for morphological differences, yield, and viability. This was correlated statistically with the donor characteristics using graph-pad prism analysis. Islet yield was substantial in all the three enzyme blends. But post-purification of islets in the Indian population, we found that the yield was better in Serva collagenase NB1 compared to Vitacyte and Roche liberase. For every gram of pancreas, the islet yield, proportion and morphology of islet cells (both free and intact) were higher in Serva collagenase compared to the other two enzyme blends.

Pancreas preservation: clinical practice and future developments.

To summarize recently published studies of preservation strategies including machine perfusion in pancreas transplantation. The shortage of conventional donors is leading units to use extended criteria donors (ECDs) and donors after cardiac death (DCD). Static cold storage (SCS) is still the standard method of preservation for pancreases and University of Wisconsin remains the gold standard preservation solution. In experimental studies, oxygen delivered during preservation reduced tissue injury and improved islet cell yield and function. Hypothermic machine perfusion of discarded human pancreases has been shown to improve adenosine triphosphate levels without adversely effect histology and oedema compared with SCS. Normothermic machine perfusion of discarded human organs has so far been challenging and led to increasing injury, rather than preservation. There are currently no clinical studies in pancreas transplant with the exception of a small number of pancreases being transplanted following normothermic regional perfusion. The storm of new organ preservation methods is now being more widely studied in the pancreas, with some promising results. These new strategies have the potential to allow expansion of the donor pool and greater utilization of ECD and DCD organs.

Pre-operative Sarcopenia Predicts Low Islet Cell Yield Following Total Pancreatectomy with Islet Autotransplantation for Chronic Pancreatitis

Background and AimSarcopenia defined as degenerative loss of skeletal muscle mass associated with aging, represents an objective parameter to measure frailty and to estimate patient’s physiologic reserves. It is a robust predictor of post-operative complications in transplantation and major oncologic surgeries. There is no data regarding the prevalence of sarcopenia in chronic pancreatitis or its impact on the outcome of patients undergoing TPIAT for CP. We sought to estimate the prevalence of sarcopenia, its impact on post-operative morbidity and prediction of islet yield and metabolic outcomes in patients undergoing TPIAT. MethodsAdult patients undergoing TPIAT between 2008 and 2018 were identified from our prospectively maintained database and were included if they had CT within 6 months before TPIAT. Skeletal muscle index (SMI) was evaluated by pre-operative CT at the level of L3 vertebra. Sarcopenia was defined as SMI < 52.4 in males and < 38.5 in females. Post-operative morbidity occurring within 90 days after TPIAT was graded as per the validated Clavien-Dindo score. Major post-surgical morbidity was defined as Clavien-Dindo score of IIIa or more. The yield of islets was quantified as islet equivalents (IEQ) and IEQ/kg recipient body weight was calculated. ResultsOne hundred and thirty-eight patients underwent TPIAT, with 46 (one-third) being classified as having pre-operative sarcopenia based on CT. No significant differences were observed in the incidence of any major surgical complications, length of hospital stay (median (range in days) 111–8 vs. 122–9; p = 0.6) and 30-day readmission rate (7 (15.2%) vs, 2 (2.2%); p = 0.5) between sarcopenic and non-sarcopenic patients. More patients with sarcopenia needed to be discharged to residential rehabilitation facility compared with non-sarcopenic patients (7 (15.2%) vs. 2 (2.2%), p = 0.007). Sarcopenia (OR 7.4 (95% CI 1.32–41.24); p = 0.023) and presence of calcification (OR 5.5 (95% CI 0.94–32.19); p = 0.05) were independent predictors of low islet yield (< 2500 IEQ/kg) on multivariate analysis. ConclusionSarcopenia is frequent in CP patients undergoing TPIAT, but not readily recognized by standard anthropometric measurement. Sarcopenia was associated with increased chance of discharge to a residential rehabilitation facility and with a poor islet yield during TPIAT. It is therefore critical to optimize nutrition prior to TPIAT surgery in CP patients.

Potential Benefits of Nrf2/Keap1 Targeting in Pancreatic Islet Cell Transplantation.

Permanent pancreatic islet cell destruction occurs in type 1 diabetes mellitus (T1DM) through the infiltration of inflammatory cells and cytokines. Loss of β-cell integrity secondary to oxidation leads to an inability to appropriately synthesize and secrete insulin. Allogenic islet cell transplantation (ICT) has risen as a therapeutic option to mitigate problematic hypoglycemia. Nevertheless, during the process of transplantation, islet cells are exposed to oxidatively caustic conditions that severely decrease the islet cell yield. Islet cells are at a baseline disadvantage to sustain themselves during times of metabolic stress as they lack a robust anti-oxidant defense system, glycogen stores, and vascularity. The Nrf2/Keap1 system is a master regulator of antioxidant genes that has garnered attention as pharmacologic activators have shown a protective response and a low side effect profile. Herein, we present the most recently studied Nrf2/Keap1 activators in pancreas for application in ICT: Dh404, dimethyl fumarate (DMF), and epigallocatechin gallate (EGCG). Furthermore, we discuss that Nrf2/Keap1 is a potential target to ameliorate oxidative stress at every step of the Edmonton Protocol.

194 – Pre-Operative Sarcopenia Predicts Low Islet Cell Yield Following Total Pancreatectomy with Islet Autotransplantation (TPIAT) for Chronic Pancreatitis (CP)

194 – Pre-Operative Sarcopenia Predicts Low Islet Cell Yield Following Total Pancreatectomy with Islet Autotransplantation (TPIAT) for Chronic Pancreatitis (CP)

Hereditary Pancreatitis – A Review of Current Concepts and Management

(1) Background: Hereditary Pancreatitis is a rare cause of acute pancreatitis. These patients usually present at a young age with recurrent episodes of acute pancreatitis that usually progresses to chronic pancreatitis with associated endocrine and exocrine failure. Hereditary pancreatitis also carries an increased lifetime risk of pancreatic adenocarcinoma. These high risk patients need early intervention where appropriate by specialist multidisciplinary teams and tailored long term management. (2) Methods: A review of the relevant literature regarding the epidemiology , the genetic mechanisms responsible for the disease and current management strategies for Hereditary Pancreatitis was performed. (3) Results: Several underlying genetic driver mutations for Hereditary Pancreatitis have been identified, notably PRSS1, SPINK1, CFTR and CRTC mutations. Recurrent episodes of pancreatitis result in a progressive loss of normal pancreatic parenchyma, which is eventually replaced with non-functioning fibrosis. High rates of diabetes and exocrine insufficiency is observed in this cohort of patients. The cumulative yearly risk of developing pancreatic cancer in patients with hereditary pancreatitis is significantly higher than the general population. Current indications for genetic testing for hereditary pancreatitis is based on low levels of evidence. Total pancreatectomy and auto islet transplantation is a definitive management strategy for hereditary pancreatitis. Early intervention may serve as an opportunity to improve islet cell yield, successful engraftment and long term endocrine function. (4) Conclusions: Hereditary Pancreatitis is associated with a significant morbidity, risk of chronic pancreatitis and pancreatic cancer. Through combining early diagnosis and intervention with a greater understanding of not only of the genetic mutation the individual carries but their own personal risk of disease progression, allows for a personalised treatment strategy for these patients.

Improved cryopreservation yield of pancreatic islets using combination of lower dose permeable cryoprotective agents

Islet transplantation has been shown to restore normoglycemia in animal models and for type 1 diabetic patients in clinical trials. One method of storing islets intended for transplantation is via cryobanking at very low temperatures (−196 °C). Cryobanking islets without the use of cryoprotecting agents (CPAs) contributes to cellular shear stress and cell death. Although current CPA protocols vary, high concentrations of these agents are toxic to islets cells. This study tested the effects of the permeating CPA dimethyl sulfoxide (Me2SO) with the addition of ethylene glycol (EG), both at reduced concentrations, on rat and human islet cell yield, viability, and glucose stimulated insulin release (GSIR). To test this, islets were treated using three combinations of CPAs (2M ME2SO, 1M ME2SO + 1M EG, and 1M ME2SO + 0.5M EG). Next, fresh islets, 2M ME2SO islets, and 1M ME2SO + 0.5M EG isolated rat islets were transplanted into streptozotocin-induced (STZ) diabetic mice. Our data showed that cryopreservation with a reduced concentration of ME2SO (1M ME2SO + multimolar EG) achieved a higher percent yield and viability when compared to the current standard 2M ME2SO treatment for both rat and human islets. Furthermore, STZ-induced diabetic mice achieved normoglycemia after transplantation with 1000 islet equivalents (IE), an average 12 days sooner, with islets cryopreserved with reduced-concentration (ME2SO + 0.5M EG), compared to islets preserved with 2M ME2SO. In conclusion, reduced concentration of penetrating CPAs during islet cryopreservation increases islet yield and viability in vitro and reduces delay before normoglycemia in diabetic mice.

The Impact of Endoscopic Retrograde Cholangiopancreatography on Islet Cell Yield During Total Pancreatectomy With Islet Autotransplantation.

Many patients with recurrent acute and chronic pancreatitis who are candidates for total pancreatectomy and islet cell autotransplantation (TPIAT) undergo endoscopic retrograde cholangiopancreatography (ERCP). However, little is known on the impact of ERCP on TPIAT outcomes. We aimed to explore the effect of antecedent ERCP on islet yield and postoperative insulin requirement after TPIAT. Through a prospectively maintained database, we identified patients who underwent TPIAT at our institution between 2009 and 2016. After adjusting for confounders, islet cell yield and postoperative insulin requirement were compared between subjects who did and did not undergo ERCP within 2 years prior to TPIAT. Data were available on 167 TPIAT patients during the study period; 105 (62.9%) had undergone ERCP within 2 years prior. Prior ERCP was not associated with a reduction in islet equivalents per patient kilogram (odds ratio, 1.37; 95% confidence interval, 0.75-2.5; P = 0.31). Antecedent ERCP was not associated with increased postoperative insulin requirement among patients with no diabetes undergoing TPIAT (odds ratio, 0.85; 95% confidence interval, 0.39-1.83; P = 0.67). Antecedent ERCP does not appear to have a deleterious impact on islet cell yield during TPIAT. Additional multicenter data are needed to more clearly determine the impact of ERCP in this context.

Patient and Procedural Factors Associated With Increased Islet Cell Yield in Total Pancreatectomy With Islet Autotransplantation.

Total pancreatectomy with islet autotransplantation (TPIAT) offers symptom relief to highly selected patients with recurrent acute and/or chronic pancreatitis. However, with variable clinical response, it is important to refine islet manipulation technique and patient selection criteria. This study explores the variables associated with high islet cell yield, a driver of success in TPIAT. This study evaluated patients who underwent TPIAT at Dartmouth-Hitchcock Medical Center from 2012 to 2016. Odds ratios were calculated for various patient and procedural characteristics. The primary clinical outcome was the number of isolated islet equivalents per kilogram body weight. Thirty-eight patients met inclusion criteria. Patients with no computed tomography or magnetic resonance imaging evidence of chronic pancreatitis, without pancreatic duct stones, and without parenchymal stones were associated with higher odds of success (P = 0.02, P = 0.02, and P = 0.002, respectively). Patients with preoperative glycated hemoglobin greater than 5.6, with islet cell suspensions positive for cultures, and with positive gram stains were associated with lower odds of success (P = 0.02, P = 0.01, and P = 0.02, respectively). Factors that diminish a successful islet cell harvest during TPIAT include the presence of infected islets, an elevated preoperative glycated hemoglobin, and the presence of pancreatic duct stones.

Patient and Procedural Factors Associated With Increased Islet Cell Yield in Total Pancreatectomy With Islet Autotransplantation

Introduction: Total pancreatectomy with islet autotransplantation (TP-IAT) provides pain relief to highly select patients with recurrent acute and/or chronic pancreatitis. However with variable outcomes and no standardized guideline for patient selection, it is important to refine islet manipulation procedures and patient selection characteristics to optimize outcomes. Success of the procedure depends on a high number of isolated islet equivalents. This study explores the patient and procedural characteristics associated with high islet cell yield. Methods: This study evaluated patients who underwent TP-IAT at Dartmouth Hitchcock Medical Center from 2012 to 2016. 38 patients met inclusion criteria. Odds ratios with 95% confidence intervals were found for various patient and procedural characteristics listed in Table 1. The primary clinical outcome was the number of isolated islet equivalents per kilogram body weight (IEQ/Kg), defined as IEQ/Kg >2,500.Table: Table. Factors Associated with Successful Islet Cell Yield During TPIATResults: All patient factors and procedural fields evaluated are listed in Table 1. Patients with no CT/MRI evidence of chronic pancreatitis showed statistically significant higher odds of success (OR=29, P=0.02). Patients without pancreatic duct stones or parenchymal stones were associated with higher odds of success (OR=23, P=0.02 and OR=55, P=0.002, respectively). Islet cell suspensions positive for cultures or positive gram stains were associated with lower chances of success (OR=0.06, P=0.02, and OR=0.48, P=0.01, respectively). Patients with preoperative HgbA1c greater than 5.6 were associated with lower odds of success (OR=0.13, P=0.02). Conclusion: This investigation found that patients without CT/MRI evidence of chronic pancreatitis, without bacterial infections, and without pancreatic duct or parenchymal stones are more likely to attain successful islet cell yields. Additionally, patients with preoperative HgbA1c less than 5.6 were associated with higher outcomes of success. These factors should be considered when selecting patients for TP-IAT.

Islet Cell Yield Following Remote Total Pancreatectomy With Islet Autotransplant is Independent of Cold Ischemia Time.

Total pancreatectomy with islet autotransplantation is increasingly being performed remotely, that is, removing the pancreas in 1 location, isolating the islet cells in another location, then returning the islets to the original location for reimplantation into the patient. We determined the influence of extended cold ischemia time on key clinical outcomes in remote islet autotransplantation. We evaluated patients who underwent remote islet autotransplantation at 2 centers from 2011 to 2014. Patients were divided into 2 groups: those with and those without a decrease in C-peptide greater than 50% from baseline. The primary clinical outcome was the quantity of isolated islet equivalents per kilogram body weight (IEQs/kg). Twenty-five patients met inclusion criteria; 15 had a decrease in C-peptide greater than 50% from baseline and had lower corresponding IEQs/kg compared with those without a decrease greater than 50% (4045 vs 6654 IEQs/kg, P = 0.01). There was no difference in cold ischemia time between the 2 groups (664 vs 600 minutes, P = 0.25). Daily insulin use at 1 year nearly met statistical significance (25.3 vs 8 U, P = 0.06), as did glycated hemoglobin (8.07 vs 6.69 mmol/L, P = 0.06). Cold ischemia time does not influence islet yield in patients undergoing pancreatectomy with remote isolation.

Influence of adenosine on preservation of porcine pancreas in islet transplantation.

Ischemia time during transplantation has greatly restricted the quality and utilization of grafts. To improve the quality of islet transplantation, adenosine was added into the University of Wisconsin (UW) pancreas perfusate to assess its effect on islet yield and function in porcine pancreas. Ten pancreata from donation after cardiac death pigs were obtained and randomly divided into two groups: control group (N = 5) with UW perfusion solution, and experimental group (N = 5) with adenosine-enriched UW perfusion solution. The yield and purity of the islet cells were counted after they were collected, purified, and stained with dithizone. Acridine orange/propidium iodide staining was applied to determine islet cell viability. Islet function was assessed by glucose stimulated insulin secretion assays, and released insulin was quantified by enzyme-linked immunosorbent assay. The metabolic substrates of the pancreas were analyzed by trace dialysis technology. We found that the addition of adenosine in UW perfusion solution significantly increased the yield, purity and viability of islet cells, as well as enhanced their insulin release. In addition, the levels of metabolic substrates, pyruvate and lactate, were significantly reduced. The addition of adenosine could effectively increase islet cell viability during mechanical perfusions, which may improve islet transplantation. This perfusion protocol may be clinically feasible, and should be considered in the clinical setting.

MRI Prediction of Islet Yield for Autologous Transplantation After Total Pancreatectomy for Chronic Pancreatitis

The relationship between magnetic resonance imaging (MRI), histopathology, and islet yield was examined for chronic pancreatitis patients undergoing total pancreatectomy and autologous islet cell transplant (TP-AIT) to determine if the yield can be predicted by pre-operative MRI. MRI sequences and histopathology were scored and compared for patients from whom ≤2,500 islet equivalents/kg were obtained with those from whom >2,500 islet equivalents/kg were obtained. Twenty patients, 14 female, mean age 40.20 ± 12.5 years, (range 19-63) underwent MRI before TP-AIT; mean 3,724 ± 891 islet equivalents/kg body weight, median 2,970, (range 76-17,770) were procured. There was no correlation between islet cell numbers and pancreas weight, HgbA1c, or c-peptide. The most common MRI sequence abnormality was the delayed interstitial phase, 14/18 (78 %). The other common MRI sequence abnormalities were, precontrast T1W 3D GRE sequence, 13/19 (68 %), and the arterial perfusion phase, 11/18 (61 %). The pancreatic duct was dilated in 10/20 (50 %). Parenchymal atrophy was noted in 10/20 (50 %). Median scores for individual MRI sequences were greater in patients with an islet cell yield of ≤2,500 islet equivalents/kg; for the delayed interstitial phase the difference was significant (median 2.5, range 1-3 versus median 0.5, range 0-3, P = 0.034). Histologically the most common feature was fibrosis, (17/17, 100 %); the score for fibrosis was greater for patients with an islet cell yield of ≤2,500 islet equivalents/kg (median 6.0, range 5-7 versus median 4.0, range 3-7, P = 0.024). A diminished islet yield may be predicted on the basis of the delayed interstitial phase MRI sequence.

Protective effects of hypothermic ex vivo perfusion on ischemia/reperfusion injury and transplant outcomes

Hypothermic machine preservation (HMP) has been used in renal transplantation since the late 1960s with recent robust prospective, multicenter data showing lower rates of delayed graft function and improved graft survival. Although now clearly beneficial for renal transplantation, extrarenal machine perfusion has remained predominantly in preclinical investigations. Pancreatic HMP has drawn little clinical interest because HMP has been suggested to cause graft edema and congestion, which is associated with early venous thrombosis and graft failure. Early investigation showed no benefit of HMP in whole-organ pancreas transplant. One report did show that HMP increases islet cell yield after isolation. Preclinical work in liver HMP has been promising. Short- and long-term HMP has been shown to improve graft viability and reduce preservation injury, even in animal models of steatotic and donation after cardiac death. The first clinical study of liver HMP using a centrifugal dual perfusion technique showed excellent results with lower hepatocellular injury markers and no adverse perfusion-related outcomes. In addition, a dramatic attenuation of proinflammatory cytokine expression was observed. Further studies of liver HMP are planned with focus on developing a reproducible and standard protocol that will allow the widespread availability of this technology. Future research and clinical trials of novel organ preservation techniques, solutions, and interventions are likely to bring about developments that will allow further reduction of preservation-related ischemia/reperfusion injury and improved outcomes and allow safer utilization of the precious and limited resource of donor organs.

Impact of co-culture on pancreatic differentiation of embryonic stem cells

Promise of cellular therapy for type 1 diabetes has inspired the search for transplantable cell sources, and embryonic stem cells (ESCs) have emerged as strong candidates. We have developed a directed differentiation protocol to obtain insulin-producing cells from ESCs. The ESCs are first induced towards a homogeneous monolayer of definitive endoderm-like cells by co-culture with primary hepatocytes. Pancreatic commitment is induced by plating the ESC-derived endoderms on Matrigel, along with Sonic hedgehog inhibition and retinoid induction. More than 70% of differentiated cells positively upregulated Pdx-1, along with pro-endocrine transcription factors Ngn3, β2/neroD1, Nkx2.2 and Nkx6.1. Final maturation to islet-specific cells is achieved by co-culturing the ESC-derived pancreatic endocrine cells with endothelial cells, which resulted in Insulin 1 upregulation in 60% of the cell population, along with high levels of IAPP and Glut2. The differentiated cell population also secreted high levels of insulin. Our findings illustrate the significant effect of co-culture in different stages of differentiation and maturation of ESCs in vitro. Such a high yield of pancreatic islet cells has not yet been reported. Our findings establish a robust protocol for islet differentiation.

Islet Cell Survival During Isolation Improved Through Protein Kinase C Epsilon Activation

Strategies inhibiting cell death signaling pathways may enhance the availability of islet transplantation for patients with type 1 diabetes mellitus. The epsilon isoform of protein kinase C (PKCε) has been shown to have an anti-apoptotic effect in many cell types. The present study investigated whether activation of PKCε may improve the yield of functional islet cells for transplantation. Islet cells were isolated from wild-type BALB/c mice preconditioned with either a PKCε activator (ψεRACK) or a TAT carrier control peptide and further treated with the same agents during isolation and in vitro for either 0, 1, 16, or 40 hours. Islet cells were assessed at each time point for viability, apoptosis, and function. ψεRACK-treated islets showed significantly decreased islet cell death up to 40 hours after isolation compared with TAT-treated control islets. Beta-cell function in response to high glucose challenge remained unchanged.

A better yield of islet cell mass from living pancreatic donors compared with cadaveric donors

Studies in rats have shown that brain death decreases beta-cell function and causes islet cell death during islet isolation and transplantation. Because a direct comparison of human islet cells between living and cadaveric donors has not been reported to date, we studied the effects of brain death on islet cell yield. A total of 36 pancreas specimens from 20 living donors and 16 cadaveric donors were used for analysis. Islets were isolated with a Ricordi chamber, and counted as equivalent islet numbers (EIN). Living donors were predominantly female, and cadaveric donors were mainly male. Although the cold ischemic time, pancreas distensibility and digestion time were not different, islet yield was observed to be higher in living donors compared with cadaveric donors (5800 +/- 3500 vs. 1900 +/- 2000 EIN/g pancreas). Islet isolation success rates (when defined as more than 2000 EIN/g) were 94.1% and 42.9%, respectively. Post-Ficoll islet recovery rates and purity were also better in living donors. However, islet viability and in vitro function of isolated islets showed no significant differences between the groups. These results suggested that brain death negatively affected the processes of islet isolation from the pancreas.

Mitochondrial Targeting with Antioxidant Peptide SS-31 Prevents Mitochondrial Depolarization, Reduces Islet Cell Apoptosis, Increases Islet Cell Yield, and Improves Posttransplantation Function

Apoptotic cell death is a defined pathway for islet cell demise, and mitochondrial dysfunction contributes to islet cell apoptosis. The hypothesis that the novel peptide D-Arg-2', 6'-dimethyltyrosine-Lys-Phe-NH2 (SS-31), previously shown to target inner mitochondrial membrane and prevent oxidative damage of neuronal cells and other cell types, optimizes pancreatic islet isolation and improves posttransplantation function in recipients with diabetes was investigated. Herein is demonstrated that SS-31 readily penetrates intact mouse islets, preserves mitochondrial polarization, reduces islet cell apoptosis, and increases islet cell yield. Optimization of islet isolation is demonstrable after SS-31 pretreatment of islet (pancreas) donor mice and with the addition of SS-31 to reagents that are used in the isolation of mouse islets. The supplementation of in vitro culture medium with SS-31 reduced islet cell apoptosis and increased the viability of human islets, as ascertained by dual-parameter flow cytometry analysis. In a stringent marginal islet cell mass transplantation model (200 mouse islets transplanted under the renal capsule of syngeneic diabetic mice) and using islets that were derived from old mice (>24 wk), SS-31 treatment was associated with prompt and sustained normoglycemia, whereas the untreated islet graft recipients remained diabetic. Our data suggest a novel strategy to optimize islet isolation and reduce the need for multiple pancreata to achieve insulin independence in the recipient with type 1 diabetes. Because SS-31 was effective with "extended" islet donors, it is hypothesized that the antioxidant SS-31 may serve to increase the pool of eligible organ donors.

Evaluation of Thermal Efficacy of Hypothermic Tissue Preservation Methods

The Two-Layer Method (TLM) of hypothermic preservation applied to cadaveric pancreata has been reported to permit improved islet cell yield and functional quality over simple immersion preservation in University of Wisconsin (UW) solution or perfluorocarbon (PFC) fluid alone. The mechanistic basis for improved islet cell outcomes with TLM preservation is argued by proponents of the TLM to be due to improved oxygen diffusion from PFC to tissue. However, no rigorous evaluation of this or alternative hypotheses has been reported. Because UW solution and PFC have significantly different thermal properties, the current study postulates that these characteristics could more likely than oxygen diffusion contribute to the salutary outcomes reported for the TLM. In the current study, an isotropic block of agarose gelatin is used as a tissue surrogate. The similarity in thermal behavior of agarose gelatin and pancreas tissue is validated. Thermal measurements are made in the tissue surrogate, when cooled by immersion in UW solution, PFC, and by TLM. Numerical calculations are performed to solve natural convection for all three methods. A multiphase model is used to solve for heat transfer between the two different fluid phases in the TLM. Results are expressed in terms of tissue cooling rates and surface heat transfer. At 30 min immersion, the instantaneous difference in temperature within the tissue surrogate immersed in UW solution and PFC is 8°C, while the same between UW solution and TLM is 4°C. The temporal heat transfer rate in the tissue surrogate immersed in UW solution is 1.8 times and 1.4 times higher than that achieved in PFC alone and TLM, respectively, at 15 min of preservation. The spatial and time averaged heat transfer coefficient in UW solution is 2 and 3 times higher than that of TLM and PFC alone, respectively, during the first 60 min of tissue immersion. The variation in heat transfer coefficients could thus contribute significantly to the outcomes achieved by tissue preservation using these three methods.

Pancreatic Autotransplantation in Chronic Pancreatitis

The apancreatic state secondary to resective surgery for chronic pancreatitis is associated with a high rate of late morbidity and mortality that is due, in part, to endocrine insufficiency. Resective procedures should, therefore, be used very selectively. Over the last 2 decades we have seen a shift from extensive distal resections to limited proximal resections. This is because of the lowering of the operative mortality of pancreatic head resection and its better results in pain relief, while preserving in situ the body and tail of the gland with its metabolic functions. Islet autotransplantation and segmental pancreatic autotransplantation were introduced in 1977 and 1978, respectively. Over 150 and 25 cases of these operations have been reported, respectively. Both techniques are evolving with a goal to improve results. Procedures placing the graft in the iliac fossa and anastomosing the pancreatic duct to the jejunum are now favored over groin placement and duct occlusion. Islet autotransplants achieve a higher yield of islet cells and decrease the exocrine impurity of the preparation. Both methods can prevent or delay the onset of diabetes mellitus, and when diabetes mellitus does occur, it is frequently easier to manage. The long-term function of the grafts appears to be dependent on the beta-cell mass available in the diseased pancreas, the loss of cells related to the transplant procedure, and the characteristics of gradual loss of function from the type of transplant used. Although extensive pancreatic resections are occasionally required, the possibility of autotransplantation should be considered in those patients.