Pancreatic islet cell transplantation: an update for interventional radiologists

Interventional Radiology Approaches for Managing Postpancreatic Transplant Complications and Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disorder characterized by the destruction of insulin-secreting beta cells in the pancreas, resulting in metabolic disturbances and long-term complications. While subcutaneous insulin remains the primary approach for achieving normoglycemia, pancreatic transplantation has emerged as an effective intervention for long-standing T1DM, providing insulin independence and normalized glycosylated hemoglobin levels. However, complications associated with pancreatic transplantation are frequent, necessitating thorough evaluation using diverse imaging modalities. This manuscript presents an overview of complications encountered with pancreatic transplantation, including vascular complications such as arterial and venous graft thrombosis, vessel stenosis, pseudoaneurysm, arterio-enteric fistula, and arteriovenous malformations. Additionally, the manuscript discusses other associated complications such as pancreatitis, pseudocyst formation, fistulas, pseudo-thrombosis of the iliac vein, post-transplantation lymphoproliferative disorder, and fluid collections. The integration of various imaging modalities plays a crucial role in diagnosing and managing these complications, with interventional radiologists assuming a vital role in employing image-guided procedures. Moreover, the manuscript explores pancreatic islet cell transplantation as a promising cellular-based therapy for T1DM, offering stable long-term glycemic control and decreased reliance on exogenous insulin in a significant proportion of recipients. This minimally invasive procedure involves the image-guided transcatheter infusion of islet cells obtained from deceased donors into the recipient's liver. The importance of interventional radiologists in managing complications related to pancreatic transplantation is underscored, with endovascular or image-guided approaches being utilized to address the diverse spectrum of encountered complications. Furthermore, the potential of islet cell transplantation as a minimally invasive alternative to traditional pancreatic transplantation is emphasized, as it offers the prospect of preventing many associated complications.

Ultrasound-Guided Human Islet Transplantation: Safety, Feasibility, and Efficacy Analysis

RATIONALE AND OBJECTIVES

We aimed to analyze the safety, feasibility, and efficacy of human islet transplantation (IT) using ultrasound (US) throughout the entire procedure.

MATERIALS AND METHODS

A total of 22 recipients (18 males; mean age 42.6 ± 17.5years) with 35 procedures were retrospective included. Under US guidance, percutaneous transhepatic portal catheterization was successfully performed through a right-sided transhepatic approach, and islets were infused into the main portal vein. Color Doppler and contrast-enhanced ultrasound were used to guide the procedure and monitor the complications. After infusion of the islet mass, the access track was embolized by embolic material. If hemorrhage persisted, US-guided radiofrequency ablation (RFA) was performed to stop bleeding. Factors that could affect the complication were analyzed. After transplantation, primary graft function was evaluated with a β-score 1month after the last islet infusion.

RESULTS

The technical success rates were 100% with a single puncture attempt. Six (17.1%) abdominal bleeding episodes were immediately stopped by US-guided RFA. No portal vein thrombosis were encountered. Dialysis (OR (Odd Ratio): 32.0; 95% CI: 1.561-656.054; and P = .025) was identified as a significant factor associated with bleeding. Primary graft function was optimal in eight patients (36.4%), suboptimal in 13 patients (59.1%), and poor in one patient (4.5%).

CONCLUSION

In conclusion, whole-procedure US-guided IT is a safe, feasible, and effective method for diabetes. Complications are either self-limiting or manageable with noninvasive treatment.

Percutaneous radiological interventions of the portal vein: a comprehensive review

The portal vein is the largest vessel supplying the liver. A number of radiological interventions are performed through the portal vein, namely for primary pathologies of the portal vein, for inducing liver hypertrophy or to treat the sequelae of portal hypertension among others. The routes used include direct transhepatic, transjugular, and, uncommonly, trans-splenic and through subcutaneous varices. Portal vein embolization and transjugular intrahepatic portosystemic shunt are among the most common portal vein interventions that are performed to induce hypertrophy of the future liver remnant and to treat complications of portal hypertension, respectively. Other interventions include transhepatic obliteration of varices and shunts, portal vein thrombolysis, portal vein recanalization, pancreatic islet cell transplantation, and embolization of portal vein injuries. We present a detailed illustrative review of the various radiological portal vein interventions.

Cutting-edge biotechnological advancement in islet delivery using pancreatic and cellular approaches

There are approximately 1 billion prediabetic people worldwide, and the global cost for diabetes mellitus (DM) is estimated to be $825 billion. In regard to Type 1 DM, transplanting a whole pancreas or its islets has gained the attention of researchers in the last few decades. Recent studies showed that islet transplantation (ILT) containing insulin-producing β cells is the most notable advancement cure for Type 1 DM. However, this procedure has been hindered by shortage and lack of sufficient islet donors and the need for long-term immunosuppression of any potential graft rejection. The strategy of encapsulation may avoid the rejection of stem-cell-derived allogeneic islets or xenogeneic islets. This review article describes various biotechnology features in encapsulation-of-islet-cell therapy for humans, including the use of bile acids.

The Clinical Efficacy and Safety of Stem Cell Therapy for Diabetes Mellitus: A Systematic Review and Meta-Analysis

Diabetes mellitus (DM) is a chronic metabolic disease with high morbidity and mortality. Recently, stem cell-based therapy for DM has shown considerable promise. Here, we undertook a systematic review and meta-analysis of published clinical studies to evaluate the efficacy and safety of stem cell therapy for both type 1 DM (T1DM) and type 2 DM (T2DM). The PubMed, Cochrane Central Register of Controlled Trials, EMBASE, and ClinicalTrials.gov databases were searched up to November 2018. We employed a fixed-effect model using 95% confidence intervals (CIs) when no statistically significant heterogeneity existed. Otherwise, a random-effects statistical model was used. Twenty-one studies met our inclusion criteria: ten T1DM studies including 226 patients and eleven T2DM studies including 386 patients. Stem cell therapy improved C-peptide levels (mean difference (MD), 0.41; 95% CI, 0.06 to 0.76) and glycosylated hemoglobin (HbA1c; MD, -3.46; 95% CI, -6.01 to -0.91) for T1DM patients. For T2DM patients, stem cell therapy improved C-peptide levels (MD, 0.33; 95% CI, 0.07 to 0.59), HbA1c (MD, -0.87; 95% CI, -1.37 to -0.37) and insulin requirements (MD, -35.76; 95% CI, -40.47 to -31.04). However, there was no significant change in fasting plasma glucose levels (MD, -0.52; 95% CI, -1.38 to 0.34). Subgroup analyses showed significant HbA1c and C-peptide improvements in patients with T1DM treated with bone marrow hematopoietic stem cells (BM-HSCs), while there was no significant change in the mesenchymal stem cell (MSC) group. In T2DM, HbA1c and insulin requirements decreased significantly after MSC transplantation, and insulin requirements and C-peptide levels were significantly improved after bone marrow mononuclear cell (BM-MNC) treatment. Stem cell therapy is a relatively safe and effective method for selected individuals with DM. The data showed that BM-HSCs are superior to MSCs in the treatment of T1DM. In T2DM, MSC and BM-MNC transplantation showed favorable therapeutic effects.

Donor age significantly influences the Raman spectroscopic biomolecular fingerprint of human pancreatic extracellular matrix proteins following collagenase-based digestion

Despite the enormous advances in the field of clinical pancreatic islet transplantation over the past two decades, the human islet isolation procedure remains suboptimal. Islets are extracted (isolated) from the exocrine tissue of donor pancreases using neutral protease (NP) and collagenase-based enzymes, which digest the extracellular matrix (ECM) scaffold surrounding human islets. This process remains highly variable and current isolation enzyme blends are ineffective at digesting pancreases from younger donors with low body mass indexes (BMI). However, age-related differences in pancreatic matrix digestion have not been studied in detail at the molecular level. To address this, we investigated ECM digestion in purified ECM proteins and in pancreatic tissue sections from younger (≤30 years; n = 5) and older (>55 years; n = 5) BMI matched donors, using Raman microspectroscopy (RMS). The Raman spectral profiles for purified collagens I, IV, VI and laminins were significantly altered following controlled enzyme treatment. Pancreatic cryosections were treated with Serva collagenase, NP, or the two enzymes combined, at clinically relevant concentrations. RMS demonstrated that the ECM at the islet-exocrine interface was differentially digested with respect to donor age. The action of collagenase was affected to a greater extent than NP. RMS is a powerful, marker-independent technology for characterising the human pancreatic ECM and demonstrating differences between donor types. Ongoing detailed studies using RMS will assist the development of donor-specific enzyme blends, increasing the overall success of human islet isolation and benefiting many people with type 1 diabetes worldwide. STATEMENT OF SIGNIFICANCE: Pancreatic islet transplantation is a minimally invasive treatment, which can reverse Type 1 Diabetes Mellitus (T1DM) in selected patients. Islets of Langerhans are extracted (isolated) from the exocrine tissue of human donor pancreases using neutral protease (NP) and collagenase-based enzymes, which digest the extracellular matrix (ECM) scaffold surrounding human islets. This process remains highly variable and current enzymes are ineffective at digesting pancreases from younger donors. Using Raman microspectroscopy we demonstrate that donor age affects the enzymatic digestion of the pancreatic ECM at the molecular level. Collagenase activity is affected to a greater extent than NP. These findings will assist the development of donor-specific enzymes, thereby increasing the overall success of islet isolation and benefiting many people with T1DM worldwide.

Stem cell therapy for patients with diabetes: a systematic review and meta-analysis of metabolomics-based risks and benefits

Background

There is a general agreement that to ensure promising results of stem cell therapy in patients with diabetes, one must first understand its risks and benefits; thus, if the risk is sufficiently low along with many benefits, it can lead to developing a novel therapeutic approach based on sound science.

Methods

A systematic review and meta-analysis was performed using all available clinical trials to determine the benefits and risks associated with stem cell therapy in patients with diabetes (both T1DM and T2DM). An extensive search was conducted across several databases using all MeSH words regarding stem cell therapy and diabetes.

Results

In T2DM, a large body of research has shown that stem cell therapy has improved the insulin daily requirement and glycosylated hemoglobin (HbA1C) levels, and also has a positive effect on these variables, but has a negative impact on c-peptide. Hence, in T1DM, stem cell therapy improves c-peptide and HbA1C levels and has a positive effect on these variables, but has a negative impact on insulin daily requirement.

Conclusions

A total of 639 cells have the ability to self-renew and differentiate into a variety of cells, including blood, heart, nervous and cartilage cells. Paradoxically, it has been stated that these cells also have the potential to form cancer cells. These possible risks warrant caution by both medical specialists and patients while proceeding with the treatment; thus, it is critically crucial to conduct further research on stem cell therapy but with first considering their risk and benefits.

Allo- and auto-percutaneous intra-portal pancreatic islet transplantation (PIPIT) for diabetes cure and prevention: the role of imaging and interventional radiology

Although the life expectancy of patients with type 1 diabetes mellitus (T1DM) has improved since the introduction of insulin therapy, the acute life-threatening and long-term complications from diabetes mellitus are significant causes of both mortality and morbidity. Percutaneous intra-portal pancreatic islet transplantation (PIPIT) is a minimally invasive, repeatable procedure which allows a β-cell replacement therapy through a liver islet engraftment, leading to insulin release and glycaemic control restoration in patients with diabetes. Allo-PIPIT, in which isolated and purified islets from cadaveric donor are used, does not require major surgery, and is potentially less expensive for the recipient. In case of long-term T1DM, islet-after-kidney (IAK) transplantation can simultaneously cure diabetes and chronic renal failure, while islet-transplant-alone (ITA) is performed in brittle, short-term T1DM, based on the infusion of an adequate islet mass and on a steroid-free immunosuppressive regimen according to the Edmonton protocol. Results of the Collaborative Islet Transplant Registry (CITR) demonstrate that allo-PIPIT reduces episodes of hypoglycemia and diabetic complications, and improves quality of life of diabetic patients. Auto-PIPIT, in which the own patient's islets are used, has been investigated as a preventive treatment for pancreatogenic diabetes in patients who undergo extensive pancreatectomy for malignant and non-malignant disease. This Review outlines the role of imaging and interventional radiology in allo- and auto-PIPIT.

Liver Track Embolization After Islet Cell Transplant: Comparison of Two Techniques

OBJECTIVE

The purpose of this study was to compare the efficacy and safety of microfibrillar collagen paste with those of gelatin sponge for liver track embolization after islet cell transplants.

MATERIALS AND METHODS

In a single-institution, retrospective study, 37 patients underwent 66 islet cell transplants from January 2005 through October 2015. Transplants were performed with 6-French transhepatic access, systemic anticoagulation, pretransplant and posttransplant portal venous pressure measurement, and image-guided liver track embolization with gelatin sponge (2005-2011) or microfibrillar collagen paste (2012-2015). The findings on 20 patients (two men, 18 women; mean age, 48 years) who underwent 35 gelatin sponge embolizations were compared with the findings on 13 patients (six men, seven women; mean age, 48 years) who underwent 22 microfibrillar collagen paste embolizations (four patients, nine procedures without embolization excluded). Medical record review was used to compare laboratory test results, portal venous pressures, and 30-day adverse bleeding events (classified according to Society of Interventional Radiology and Bleeding Academic Research Consortium criteria) between groups.

RESULTS

The technical success rates were 100% in the microfibrillar collagen paste group and 91% in the gelatin sponge group. Group characteristics were similar, there being no differences in platelet count, partial thromboplastin time, or number of islet cell transplants per patient (p > 0.05). A statistical difference in international normalized ratio (1.0 versus 1.1) was not clinically significant (p = 0.012). Posttransplant portal venous pressure was slightly higher among patients treated with gelatin sponge (13 versus 9 mm Hg, p = 0.002). No bleeding occurred after microfibrillar collagen paste embolization, whereas nine bleeding events followed gelatin sponge embolization (0% versus 26%, p = 0.020). In univariate comparison of bleeding and nonbleeding groups, the use of gelatin sponge was statistically associated with postprocedure hemorrhage.

CONCLUSION

Microfibrillar collagen paste is effective and safe for liver track embolization to prevent bleeding after islet cell transplants. It appears to be more efficacious than gelatin sponge.

Autologous bone marrow derived stem cell therapy in patients with type 2 diabetes mellitus - defining adequate administration methods

AIM

To carry out randomized trial for evaluating effects of autologous bone marrow derived stem cell therapy (ABMSCT) through different routes.

METHODS

Bone marrow aspirate was taken from the iliac crest of patients. Bone marrow mononuclear cells were separated and purified using centrifugation. These cells were then infused in a total of 21 patients comprising three groups of 7 patients each. Cells were infused into the superior pancreaticoduodenal artery (Group I), splenic artery (Group II) and through the peripheral intravenous route (Group III). Another group of 7 patients acted as controls and a sham procedure was carried out on them (Group IV). The cells were labelled with the PET tracer F18-FDG to see their homing and in vivo distribution. Data for clinical outcome was expressed as mean ± SE. All other data was expressed as mean ± SD. Baseline and post treatment data was compared at the end of six months, using paired t-test. Cases and controls data were analyzed using independent t-test. A probability (P) value of < 0.05 was regarded as statistically significant. Measures of clinical outcome were taken as the change or improvement in the following parameters: (1) C-peptide assay; (2) HOMA-IR and HOMA-B; (3) reduction in Insulin dose; subjects who showed reduction of insulin requirement of more than 50% from baseline requirement were regarded as responders; and (4) reduction in HbA1c.

RESULTS

All the patients, after being advised for healthy lifestyle changes, were evaluated at periodical intervals and at the end of 6 mo. The changes in body weight, body mass index, waist circumference and percentage of body fat in all groups were not significantly different at the end of this period. The results of intra-group comparison before and after ABMSCT at the end of six months duration was as follows: (1) the area under C-peptide response curve was increased at the end of 6 mo however the difference remained statistically non-significant (P values for fasting C-peptide were 0.973, 0.103, 0.263 and 0.287 respectively and the P values for stimulated C-peptide were 0.989, 0.395, 0.325 and 0.408 respectively for groups I to IV); (2) the Insulin sensitivity indices of HOMA IR and HOMA B also did not show any significant differences (P values for HOMA IR were 0.368, 0.223, 0.918 and 0.895 respectively and P values for HOMA B were 0.183, 0.664, 0.206 and 0.618 respectively for groups I to IV); (3) Group Ishowed a significant reduction in Insulin dose requirement (P < 0.01). Group II patients also achieved a significant reduction in Insulin dosages (P = 0.01). The Group I and Group II patients together constituted the targeted group wherein the feeding arteries to pancreas were used for infusing stem cells. Group III, which was the intravenous group, showed a non-significant reduction in Insulin dose requirement (P = 0.137). Group IV patients which comprised the control arm also showed a significant reduction in Insulin dosages at the end of six months (P < 0.05); and (4) there was a non-significant change in the Hb A1c levels at the end of 6 mo across all groups (P = 0.355, P = 0.351, P = 0.999 and P = 0.408 respectively for groups I to IV).

CONCLUSION

Targeted route showed a significant reduction in Insulin requirement at the end of six months of study period whereas the intravenous group failed to show reduction.

VP40 Comprehensive Evaluation Of Islet Transplantation For Type I Diabetes

INTRODUCTION:

Despite several therapeutic options existing for the patients with type I diabetes, the patients are still at high risk for severe acute and chronic complications (1). Pancreatic islet transplantation is a promising therapy to achieve good glycemic control with no or little additional insulin (2). This study was to evaluate the effectiveness, safety, economics and social ethics of islet transplantation (IT) for the patients with type I diabetes.

METHODS:

We searched PubMed, Cochrane Library, CNKI and CBM to retrieve eligible literatures. The values of H1bAc before and after transplantation, the rates of insulin independence and functional islet graft at the last follow-up, and the insulin dose per patient-day were analyzed. Descriptive statistics, t tests and random effects meta-analyses were used in the study.

RESULTS:

Totally 21 original papers with 488 cases from 9 different countries were reviewed and analyzed. The studies showed that the H1bAc was decreased from 7.7 percent (95 percent Confidence Interval, CI: 7.4, 8.1) before IT to 6.2 percent (95 percent CI: 5.9, 6.4) after IT. At the last follow-up, the rate of insulin independence was 48.96 percent (95 percent CI: 31.32, 66.73) and the rate of functional islet graft was 65.79 percent (95 percent CI: 47.06, 82.21). The daily insulin requirement dropped from 0.52U/kg/d to 0.21 U/kg/d. The main adverse events of islet transplantation were bleeding (7.01 percent) and the complications related to immunosuppression therapy (6.37 percent), but they were less than those of whole pancreas transplantation.

Another study with a 20-year follow-up also showed that the cost-effectiveness of islet transplantation (USD47,800 per QALY) was better than that of insulin therapy (USD71,000 per QALY). In spite of the better evidences of islet transplantation, the insufficient organ donation and issues of cell purification and immunological rejection limited islet transplantation's widespread utilization (1).

CONCLUSIONS:

The islet transplantation therapy for the patients with type I diabetes has a potential to achieve insulin independence and better cost-effectiveness, and is relatively safe. But there are some obstacles for its wide utilization.

Portal Venous Interventions: State of the Art

In recent decades, there have been numerous advances in the management of liver cancer, cirrhosis, and diabetes mellitus. Although these diseases are wide ranging in their clinical manifestations, each can potentially be treated by exploiting the blood flow dynamics within the portal venous system, and in some cases, adding cellular therapies. To aid in the management of these disease states, minimally invasive transcatheter portal venous interventions have been developed to improve the safety of major hepatic resection, to reduce the untoward effects of sequelae from end-stage liver disease, and to minimize the requirement of exogenously administered insulin for patients with diabetes mellitus. This state of the art review therefore provides an overview of the most recent data and strategies for utilization of preoperative portal vein embolization, transjugular intrahepatic portosystemic shunt placement, balloon retrograde transvenous obliteration, and islet cell transplantation.

Clinical Efficacy of Stem Cell Therapy for Diabetes Mellitus: A Meta-Analysis

BACKGROUND

Stem cell therapy is a promising therapeutic modality for advanced diabetes mellitus (DM). This study presents a meta-analysis of relevant clinical trials to determine the efficacy of stem cell therapy in DM. We aim to critically evaluate and synthesize clinical evidence on the safety and efficiency of different types of stem cell therapy for both T1DM and T2DM.

METHODS AND FINDINGS

We pooled participant-level data from twenty-two eligible clinical trials that satisfied our inclusion criteria, with a total of 524 patients. There were significant differences in the outcome based on the type and source of the infused cells. Out of all T1DM patients who received CD34+ hematopoietic stem cell (HSC) infusion, 58.9% became insulin independent for a mean period of 16 months, whereas the results were uniformly negative in patients who received umbilical cord blood (UCB). Infusion of umbilical cord mesenchymal stem cells (UC-MSCs) provided significantly beneficial outcome in T1DM, when compared to bone-marrow mesenchymal stem cells (BM-MSCs) (P<0.0001 and P = 0.1557). Administration of stem cell therapy early after DM diagnosis was more effective than intervention at later stages (relative risk = 2.0, P = 0.0008). Adverse effects were observed in only 21.72% of both T1DM and T2DM stem cell recipients with no reported mortality. Out of all poor responders, 79.5% were diagnosed with diabetic ketoacidosis.

CONCLUSIONS

Stem cell transplantation can represent a safe and effective treatment for selected patients with DM. In this cohort of trials, the best therapeutic outcome was achieved with CD34+ HSC therapy for T1DM, while the poorest outcome was observed with HUCB for T1DM. Diabetic ketoacidosis impedes therapeutic efficacy.

A Comparative Analysis of the Safety, Efficacy, and Cost of Islet Versus Pancreas Transplantation in Nonuremic Patients With Type 1 Diabetes

Few current studies compare the outcomes of islet transplantation alone (ITA) and pancreas transplantation alone (PTA) for type 1 diabetes (T1D). We examined these two beta cell replacement therapies in nonuremic patients with T1D with respect to safety, graft function and cost. Sequential patients received PTA (n = 15) or ITA (n = 10) at our institution. Assessments of graft function included duration of insulin independence; glycemic control, as measured by hemoglobin A1c; and elimination of severe hypoglycemia. Cost analysis included all normalized costs associated with transplantation and inpatient management. ITA patients received one (n = 6) or two (n = 4) islet transplants. Mean duration of insulin independence in this group was 35 mo; 90% were independent at 1 year, and 70% were independent at 3 years. Mean duration of insulin independence in PTA was 55 mo; 93% were insulin independent at 1 year, and 64% were independent at 3 years. Glycemic control was comparable in all patients with functioning grafts, as were overall costs ($138 872 for ITA, $134 748 for PTA). We conclude that with advances in islet isolation and posttransplant management, ITA can produce outcomes similar to PTA and represents a clinically viable option to achieve long-term insulin independence in selected patients with T1D.

The cell cycle as a brake for β-cell regeneration from embryonic stem cells

The generation of insulin-producing β cells from stem cells in vitro provides a promising source of cells for cell transplantation therapy in diabetes. However, insulin-producing cells generated from human stem cells show deficiency in many functional characteristics compared with pancreatic β cells. Recent reports have shown molecular ties between the cell cycle and the differentiation mechanism of embryonic stem (ES) cells, assuming that cell fate decisions are controlled by the cell cycle machinery. Both β cells and ES cells possess unique cell cycle machinery yet with significant contrasts. In this review, we compare the cell cycle control mechanisms in both ES cells and β cells, and highlight the fundamental differences between pluripotent cells of embryonic origin and differentiated β cells. Through critical analysis of the differences of the cell cycle between these two cell types, we propose that the cell cycle of ES cells may act as a brake for β-cell regeneration. Based on these differences, we discuss the potential of modulating the cell cycle of ES cells for the large-scale generation of functionally mature β cells in vitro. Further understanding of the factors that modulate the ES cell cycle will lead to new approaches to enhance the production of functional mature insulin-producing cells, and yield a reliable system to generate bona fide β cells in vitro.

Impact of Procedure-Related Complications on Long-term Islet Transplantation Outcome

BACKGROUND

Pancreatic islet transplantation offers a promising biotherapy for the treatment of type 1 diabetes, but this procedure has met significant challenges over the years. One such challenge is to address why primary graft function still remains inconsistent after islet transplantation. Several variables have been shown to affect graft function, but the impact of procedure-related complications on primary and long-term graft functions has not yet been explored.

METHODS

Twenty-six patients with established type 1 diabetes were included in this study. Each patient had two to three intraportal islet infusions to obtain 10,000 islet equivalent (IEQ)/kg in body weight, equaling a total of 68 islet infusions. Islet transplantation consisted of three sequential fresh islet infusions within 3 months. Islet infusions were performed surgically or under ultrasound guidance, depending on patient morphology, availability of the radiology suite, and patient medical history. Prospective assessment of adverse events was recorded and graded using "Common Terminology Criteria for adverse events in Trials of Adult Pancreatic Islet Transplantation."

RESULTS

There were no deaths or patients dropouts. Early complications occurred in nine of 68 procedures. β score 1 month after the last graft and optimal graft function (β score ≥7) rate were significantly lower in cases of procedure-related complications (P = 0.02, P = 0.03). Procedure-related complications negatively impacted graft function (P = 0.009) and was an independent predictive factor of long-term graft survival (P = 0.033) in multivariate analysis.

CONCLUSION

Complications occurring during radiologic or surgical intraportal islet transplantation significantly impair primary graft function and graft survival regardless of their severity.

Concise Review: Manufacturing of Pancreatic Endoderm Cells for Clinical Trials in Type 1 Diabetes

The cellular component of ViaCyte's VC-01 combination product for type 1 diabetes, pancreatic endoderm cells (PEC-01) derived from CyT49 human embryonic stem cells, matures after transplantation and functions to regulate blood glucose in rodent models. The aims in manufacturing PEC-01 at scale are to generate a consistent and robust transplantable population that functions reliably and safely in vivo. ViaCyte has integrated multiple bioprocessing strategies to enable a tightly controlled PEC-01 manufacturing process for clinical entry.

Islet cell transplant and the incorporation of Tregs

PURPOSE OF REVIEW

T regulatory cells (Tregs) play a central role in maintaining immune homeostasis and peripheral tolerance to foreign antigens in humans. The immune response to alloantigens and recurrence of autoimmunity contribute to pancreatic islet transplant dysfunction, hence the adoptive transfer of Tregs has the potential to significantly improve islet graft survival. In this review, we provide an in-depth analysis of challenges associated with the application of ex-vivo expanded Tregs therapy in pancreatic islet transplant.

RECENT FINDINGS

Tregs administered systemically may poorly migrate to the site of transplantation, which is critical for tolerance induction and graft protection. Intraportal administration of pancreatic tissue exerts some limitations on the ability to cotransplant Tregs at the same site of islet transplantation. In order to maximize therapeutic potential of Tregs, islet transplantation protocols may need additional refinement. Further to this, the Tregs may require cryopreservation in order to make them readily available at the same time as islet transplant.

SUMMARY

On the basis of current experience and technology, the combination of islet and Treg cotransplantation is feasible and has great potential to improve islet graft survival. The possibility to wean off, or withdraw, traditional immunosuppressive agents and improve patient quality of life makes it an interesting avenue to be pursued.

Spatio-temporal simulation of first pass drug perfusion in the liver

The liver is the central organ for detoxification of xenobiotics in the body. In pharmacokinetic modeling, hepatic metabolization capacity is typically quantified as hepatic clearance computed as degradation in well-stirred compartments. This is an accurate mechanistic description once a quasi-equilibrium between blood and surrounding tissue is established. However, this model structure cannot be used to simulate spatio-temporal distribution during the first instants after drug injection. In this paper, we introduce a new spatially resolved model to simulate first pass perfusion of compounds within the naive liver. The model is based on vascular structures obtained from computed tomography as well as physiologically based mass transfer descriptions obtained from pharmacokinetic modeling. The physiological architecture of hepatic tissue in our model is governed by both vascular geometry and the composition of the connecting hepatic tissue. In particular, we here consider locally distributed mass flow in liver tissue instead of considering well-stirred compartments. Experimentally, the model structure corresponds to an isolated perfused liver and provides an ideal platform to address first pass effects and questions of hepatic heterogeneity. The model was evaluated for three exemplary compounds covering key aspects of perfusion, distribution and metabolization within the liver. As pathophysiological states we considered the influence of steatosis and carbon tetrachloride-induced liver necrosis on total hepatic distribution and metabolic capacity. Notably, we found that our computational predictions are in qualitative agreement with previously published experimental data. The simulation results provide an unprecedented level of detail in compound concentration profiles during first pass perfusion, both spatio-temporally in liver tissue itself and temporally in the outflowing blood. We expect our model to be the foundation of further spatially resolved models of the liver in the future.

Transplantation of Encapsulated Pancreatic Islets as a Treatment for Patients with Type 1 Diabetes Mellitus

Encapsulation of pancreatic islets has been proposed and investigated for over three decades to improve islet transplantation outcomes and to eliminate the side effects of immunosuppressive medications. Of the numerous encapsulation systems developed in the past, microencapsulation have been studied most extensively so far. A wide variety of materials has been tested for microencapsulation in various animal models (including nonhuman primates or NHPs) and some materials were shown to induce immunoprotection to islet grafts without the need for chronic immunosuppression. Despite the initial success of microcapsules in NHP models, the combined use of islet transplantation (allograft) and microencapsulation has not yet been successful in clinical trials. This review consists of three sections: introduction to islet transplantation, transplantation of encapsulated pancreatic islets as a treatment for patients with type 1 diabetes mellitus (T1DM), and present challenges and future perspectives.

Percutaneous intraportal application of adipose tissue-derived mesenchymal stem cells using a balloon occlusion catheter in a porcine model of liver fibrosis

PURPOSE

To investigate the safety and effectiveness of a novel endovascular approach for therapeutic cell delivery using a balloon occlusion catheter in a large animal model of liver fibrosis.

MATERIALS AND METHODS

Transcatheter arterial embolization with ethiodized oil (Ethiodol) and ethanol was used to induce liver damage in 11 pigs. Mesenchymal stem cells (MSCs) were harvested from adipose tissue and engineered to express green fluorescent protein (GFP). A balloon occlusion catheter was positioned in the bilateral first-order portal vein branches 2 weeks after embolization to allow intraportal application of MSCs in six experimental animals. MSCs were allowed to dwell for 10 minutes using prolonged balloon inflation. Five control animals received a sham injection of normal saline in a similar fashion. Hepatic venous pressure gradient (HVPG) was measured immediately before necropsy. Specimens from all accessible lobes were obtained with ultrasound-guided percutaneous 18-gauge biopsy 2 hours after cell application. All animals were euthanized within 4 weeks. Fluorescent microscopy was used to assess the presence and distribution of cells.

RESULTS

Liver injury and fibrosis were successfully induced in all animals. MSCs (6-10 × 10(7)) were successfully delivered into the portal vein in the six experimental animals. Cell application was not associated with vascular complications. HVPG showed no instances of portal hypertension. GFP-expressing MSCs were visualized in biopsy specimens and were distributed primarily within the sinusoidal spaces; however, 4 weeks after implantation, MSCs could not be identified in histologic specimens.

CONCLUSIONS

A percutaneous endovascular approach for cell delivery using a balloon occlusion catheter proved safe for intraportal MSC application in a large animal model of liver fibrosis.

Islet transplantation in type 1 diabetes: ongoing challenges, refined procedures, and long-term outcome

Remarkable progress has been made in islet transplantation over a span of 40 years. Once just an experimental curiosity in mice, this therapy has moved forward, and can now provide robust therapy for highly selected patients with type 1 diabetes (T1D), refractory to stabilization by other means. This progress could not have occurred without extensive dynamic international collaboration. Currently, 1,085 patients have undergone islet transplantation at 40 international sites since the Edmonton Protocol was reported in 2000 (752 allografts, 333 autografts), according to the Collaborative Islet Transplant Registry. The long-term results of islet transplantation in selected centers now match registry data of pancreas-alone transplantation, with 6 sites reporting five-year insulin independence rates ≥50%. Islet transplantation has been criticized for the use of multiple donor pancreas organs, but progress has also occurred in single-donor success, with 10 sites reporting increased single-donor engraftment. The next wave of innovative clinical trial interventions will address instant blood-mediated inflammatory reaction (IBMIR), apoptosis, and inflammation, and will translate into further marked improvements in single-donor success. Effective control of auto- and alloimmunity is the key to long-term islet function, and high-resolution cellular and antibody-based assays will add considerable precision to this process. Advances in immunosuppression, with new antibody-based targeting of costimulatory blockade and other T-B cellular signaling, will have further profound impact on the safety record of immunotherapy. Clinical trials will move forward shortly to test out new human stem cell derived islets, and in parallel trials will move forward, testing pig islets for compatibility in patients. Induction of immunological tolerance to self-islet antigens and to allografts is a difficult challenge, but potentially within our grasp.