Portal vein thrombosis is a potentially preventable complication in clinical islet transplantation

Comparison of thrombosis risk in patients undergoing purified and non-purified islet cell transplantation

OBJECTIVES

To investigate the thrombosis risk and adverse bleeding events in patients who received purified vs. non-purified islet cell autotransplants (IAT).

METHODS

We performed a retrospective cohort study evaluating the rate of portal vein thrombosis (PVT), adverse bleeding events, and premature heparin discontinuation in purified and non-purified IAT patients at our center between 2013 and 2022.

RESULTS

The incidence of PVT formation was 0 % in the purified group (23 patients) and 4.2 % in the non-purified group (48 patients). Patients in the purified islet group received lower intra-operative heparin dosing compared to patients in the non-purified group (3157units vs 2657units, p = 0.03), but both groups received similar post-operative heparin dosing (505units vs. 437units, p = 0.55). Non-purified patients were on heparin for significantly fewer days than purified patients (1.6 days vs. 3.2 days, p < 0.01). There was no difference in adverse bleeding events that resulted in premature heparin discontinuation (39.1 % vs. 62.5 %, p = 0.08) nor blood transfusion requirements (34.8 % vs. 41.7 %, p = 0.58) between the purified and non-purified groups. However, patients in the purified group had higher rates of reoperation due to rebleeding compared with the non-purified group (17.4 % vs 0 %, p < 0.01).

CONCLUSIONS

While PVT is a relatively rare event in both purified and non-purified IAT when peri-operative and post-operative full-dose heparinization is administered, there remains a clinical difference in PVT formation between purified and non-purified IATs. Although bleeding risk may potentially be mitigated by a reduction in the duration of full dose heparinization without a corresponding risk in PVT rate, further investigation is warranted.

Can Islet Transplantation Possibly Reduce Mortality in Type 1 Diabetes

Islet transplantation (IT) is a successful natural cell therapy. But the benefits are known mostly to individuals with severe type 1 diabetes who undergo IT and the health care professionals that work to make the therapy available, reproducible, and safe. Data linking IT to overall survival in T1D might alter this situation and frame the therapy in a more positive light. Recent analysis of mortality in several cohorts suggests that IT has possible survival benefits when used alone or in conjunction with renal transplantation. Multi-center prospective studies with long-term follow-up of individuals that receive stand-alone IT versus individuals who qualify for but do not undergo the procedure would seem reasonable to undertake to confirm an IT survival benefit.

Impact of Tissue Factor Gene Knockout on Coagulation Properties of Umbilical Cord-Derived Multipotent Mesenchymal Stromal/Stem Cells

Multipotent mesenchymal stromal/stem cells (MSCs) refer to a population of stem cells that exhibit distinct progenitor cell characteristics including the potential for differentiation into a wide range of cell types. MSCs have become a promising candidate for cell therapy and tissue regeneration due to their unique properties, such as their ability to differentiate into multiple cell types, their capacity for expansion, self-renewal, and immune-regulatory effects. However, reports have brought attention to thrombosis-related complications associated with MSCs therapy in the last decade. As tissue factor (TF) is a powerful coagulation activator expressed by MSCs that stimulates the extrinsic coagulation pathway, we investigated the thrombotic properties of human umbilical cord MSCs (HUCMSCs) after knocking out the TF gene. MSCs populations that obtained from umbilical cord were cultured and expanded in the appropriate medium cell culture. The identity of the MSCs was verified through flow cytometry, and their ability to differentiate into osteogenic and adipogenic lineages. Two gRNAs for Exons 1 and 2 of the TF gene have been designed and cloned into px458 vector's backbone (pSpCas9 (BB)-2A-GFP). Following transfecting of gRNAs into HUCMSCs and successfully knocking out the TF gene using GAP-PCR, the impact of normal and knockout HUCMSCs on coagulation was assessed through prothrombin time (PT), D-dimer level, clotting time (CT), and turbidity assay. Furthermore, the impact of TF knockout (TFKO) on MMP19 expression was assessed. Our results revealed that the PT was prolonged and D-dimer level was decreased in TFKO group compared to normal HUCMSCs. These findings suggest that TF gene plays a crucial role in regulating coagulation in HUCMSCs. Also, a significant reduction in MMP19 expression was observed within the TFKO group.

The First Case of Intra-portal Islet Implantation During Liver Machine Perfusion Allowing Simultaneous Islet-liver Transplantation in A Human: A New and Safe Treatment for End-stage Liver Disease Combined With Diabetes Mellitus

OBJECTIVE

Evaluating the safety and efficacy of implanting a liver with islet grafts into patients with end-stage liver disease and diabetes mellitus (DM).

BACKGROUND

DM and end-stage liver diseases are significant health concern worldwide, often coexisting and mutually influencing each other. Addressing both diseases simultaneously is paramount.

METHODS

We utilized the islet transplantation combined ischemia-free liver transplantation (ITIFLT) technique to treat a patient with hepatocellular carcinoma (HCC) and type 2 diabetes mellitus (T2DM). The liver was procured and preserved using the ischemia-free liver transplantation (IFLT) technique, and during normothermic machine perfusion (NMP), isolated and purified islet grafts were transplanted into the liver through the portal vein. Finally, the liver, incorporating with the transplant islet grafts, was implanted into the recipient without interruption of blood supply.

RESULTS

The patient received both liver and islet graft from the same donor. The patient achieved insulin-independence by post-transplant day (PTD) 9, and both liver and islet function remained robust. The patient was discharged on PTD 18 and experienced no surgical or transplantation-related complications during the follow-up period. Furthermore, islet grafts presence was observed in liver biopsies after islet transplantation.

CONCLUSIONS

This landmark case marks the inaugural application of ITIFLT in humans, signifying its potential as a promising treatment modality for end-stage liver disease with DM.

Hydrogel Encapsulation Techniques and Its Clinical Applications in Drug Delivery and Regenerative Medicine: A Systematic Review

Hydrogel encapsulation is a promising carrier for cell and drug delivery due to its ability to protect the encapsulated entities from harsh physiological conditions and enhance their therapeutic efficacy and bioavailability. However, there is not yet consensus on the optimal hydrogel type, encapsulation method, and clinical application. Therefore, a systematic review of hydrogel encapsulation techniques and their potential for clinical application is needed to provide a comprehensive and up-to-date overview. In this systematic review, we searched electronic databases for articles published between 2008 and 2023 that described the encapsulation of cells or drug molecules within hydrogels. Herein, we identified 9 relevant studies that met the inclusion and exclusion criteria of our study. Our analysis revealed that the physicochemical properties of the hydrogel, such as its porosity, swelling behavior, and degradation rate, play a critical role in the encapsulation of cells or drug molecules. Furthermore, the encapsulation method, including physical, chemical, or biological methods, can affect the encapsulated entities' stability, bioavailability, and therapeutic efficacy. Challenges of hydrogel encapsulation include poor control over the release of encapsulated entities, limited shelf life, and potential immune responses. Future directions of hydrogel encapsulation include the development of novel hydrogel and encapsulation methods and the integration of hydrogel encapsulation with other technologies, such as 3D printing and gene editing. In conclusion, this review is useful for researchers, clinicians, and policymakers who are interested in this field of drug delivery and regenerative medicine that can serve as a guide for the future development of novel technologies that can be applied into clinical practice.

Current status of total pancreatectomy with islet autotransplantation for chronic and recurrent acute pancreatitis

Total pancreatectomy with islet autotransplantation (TPIAT) is an established and effective treatment modality for patients diagnosed with intractable chronic pancreatitis (CP) and recurrent acute pancreatitis (RAP). TPIAT primarily aims to manage debilitating pain leading to impaired quality of life among patients with CP or RAP, which can be successfully managed with medical, endoscopic, or surgical interventions. TPIAT is significantly successful in relieving pain associated with CP and improving health-related quality of life outcomes. Furthermore, the complete loss of pancreatic endocrine function attributed to total pancreatectomy (TP) can be compensated by autologous islet transplantation (IAT). Patients receiving IAT can achieve insulin independence or can be less dependent on exogenous insulin compared with those receiving TP alone. Historically, TPIAT has been mainly used in the United States, and its outcomes have been improving due to technological advancements. Despite some challenges, TPIAT can be a promising treatment for patients with CP-related intractable pain. Thus far, TPIAT is not commonly performed in Japan. Nevertheless, it may improve health-related quality of life in Japanese patients with CP, similar to Western patients. This review article aimed to provide an overview of the indications, related procedures, and outcomes of TPIAT and to discuss future prospects in Japan.

Total Pancreatectomy with Islet Auto-Transplantation: Surgical Procedure, Outcomes, and Quality of Life

Chronic pancreatitis is a progressive and irreversible process of pancreatic inflammation and fibrosis that can lead to intractable abdominal pain and severely impaired quality of life (QoL). Often patients are refractory to standard medical or endoscopic treatments. Total pancreatectomy (TP) and islet auto-transplantation (TP-IAT) can offer pain relief to patients by removing the entire pancreas and the auto-transplant component ameliorates the resulting diabetes. QoL is significantly improved after TP-IAT when insulin independence is present. Recent data support offering TP-IAT rather than TP alone and treating with exogenous insulin for patients with debilitating chronic pancreatitis.

The Image-Histology Correlation of Subcutaneous mPEG-poly(Ala) Hydrogel-Embedded MIN6 Cell Grafts in Nude Mice

Previously, we have successfully used noninvasive magnetic resonance (MR) and bioluminescence imaging to detect and monitor mPEG-poly(Ala) hydrogel-embedded MIN6 cells at the subcutaneous space for up to 64 days. In this study, we further explored the histological evolution of MIN6 cell grafts and correlated it with image findings. MIN6 cells were incubated overnight with chitosan-coated superparamagnetic iron oxide (CSPIO) and then 5 × 10⁶ cells in the 100 μL hydrogel solution were injected subcutaneously into each nude mouse. Grafts were removed and examined the vascularization, cell growth and proliferation with anti-CD31, SMA, insulin and ki67 antibodies, respectively, at 8, 14, 21, 29 and 36 days after transplantation. All grafts were well-vascularized with prominent CD31 and SMA staining at all time points. Interestingly, insulin-positive cells and iron-positive cells were scattered in the graft at 8 and 14 days; while clusters of insulin-positive cells without iron-positive cells appeared in the grafts at 21 days and persisted thereafter, indicating neogrowth of MIN6 cells. Moreover, proliferating MIN6 cells with strong ki67 staining was observed in 21-, 29- and 36-day grafts. Our results indicate that the originally transplanted MIN6 cells proliferated from 21 days that presented distinctive bioluminescence and MR images.

From islet of Langerhans transplantation to the bioartificial pancreas

Type 1 diabetes is a disease resulting from autoimmune destruction of the insulin-producing beta cells in the pancreas. When type 1 diabetes develops into severe secondary complications, in particular end-stage nephropathy, or life-threatening severe hypoglycemia, the best therapeutic approach is pancreas transplantation, or more recently transplantation of the pancreatic islets of Langerhans. Islet transplantation is a cell therapy procedure, that is minimally invasive and has a low morbidity, but does not display the same rate of functional success as the more invasive pancreas transplantation because of suboptimal engraftment and survival. Another issue is that pancreas or islet transplantation (collectively known as beta cell replacement therapy) is limited by the shortage of organ donors and by the need for lifelong immunosuppression to prevent immune rejection and recurrence of autoimmunity. A bioartificial pancreas is a construct made of functional, insulin-producing tissue, embedded in an anti-inflammatory, immunomodulatory microenvironment and encapsulated in a perm-selective membrane allowing glucose sensing and insulin release, but isolating from attacks by cells of the immune system. A successful bioartificial pancreas would address the issues of engraftment, survival and rejection. Inclusion of unlimited sources of insulin-producing cells, such as xenogeneic porcine islets or stem cell-derived beta cells would further solve the problem of organ shortage. This article reviews the current status of clinical islet transplantation, the strategies aiming at developing a bioartificial pancreas, the clinical trials conducted in the field and the perspectives for further progress.

Hyaluronic acid methacrylate/pancreatic extracellular matrix as a potential 3D printing bioink for constructing islet organoids

Islet transplantation has poor long-term efficacy because of the lack of extracellular matrix support and neovascularization; this limits its wide application in diabetes research. In this study, we develop a 3D-printed islet organoid by combining a pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA) as specific bioinks. The HAMA/pECM hydrogel was validated in vitro to maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, which helps improve islet function and activity. Further, in vivo experiments confirmed that the 3D-printed islet-encapsulated HAMA/pECM hydrogel increases insulin levels in diabetic mice, maintains blood glucose levels within a normal range for 90 days, and rapidly secretes insulin in response to blood glucose stimulation. In addition, the HAMA/pECM hydrogel can facilitate the attachment and growth of new blood vessels and increase the density of new vessels. Meanwhile, the designed 3D-printed structure was conducive to the formation of vascular networks and it promoted the construction of 3D-printed islet organoids. In conclusion, our experiments optimized the HAMA/pECM bioink composition and 3D-printed structure of islet organoids with promising therapeutic effects compared with the HAMA hydrogel group that can be potentially used in clinical applications to improve the effectiveness and safety of islet transplantation in vivo. STATEMENT OF SIGNIFICANCE: The extraction process of pancreatic islets can easily cause damage to the extracellular matrix and vascular system, resulting in poor islet transplantation efficiency. We developed a new tissue-specific bioink by combining pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA). The islet organoids constructed by 3D printing can mimic the microenvironment of the pancreas and maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, thereby improving islet function and activity. In addition, the 3D-printed structures we designed are favorable for the formation of new blood vessel networks, bringing hope for the long-term efficacy of islet transplantation.

Pancreatic islet transplantation in type 1 diabetes: 20-year experience from a single-centre cohort in Canada

BACKGROUND

Islet transplantation offers an effective treatment for selected people with type 1 diabetes and intractable hypoglycaemia. Long-term experience, however, remains limited. We report outcomes from a single-centre cohort up to 20 years after islet transplantation.

METHODS

This cohort study included patients older than 18 years with type 1 diabetes undergoing allogeneic islet transplantation between March 11, 1999, and Oct 1, 2019, at the University of Alberta Hospital (Edmonton, AB, Canada). Patients who underwent islet-after-kidney transplantation and islet transplantation alone or islet transplantation before whole-pancreas transplantation (follow-up was censored at the time of whole-pancreas transplantation) were included. Patient survival, graft survival (fasting plasma C-peptide >0·1 nmol/L), insulin independence, glycaemic control, and adverse events are reported. To identify factors associated with prolonged graft survival, recipients with sustained graft survival (≥90% of patient follow-up duration) were compared with those who had non-sustained graft survival (<90% of follow-up duration). Multivariate binary logistic regression analyses were done to determine predictors of sustained graft survival.

FINDINGS

Between March 11, 1999, and Oct 1, 2019, 255 patients underwent islet transplantation and were included in the analyses (149 [58%] were female and 218 [85%] were White). Over a median follow-up of 7·4 years (IQR 4·4-12·2), 230 (90%) patients survived. Median graft survival was 5·9 years (IQR 3·0-9·5), and graft failure occurred in 91 (36%) patients. 178 (70%) recipients had sustained graft survival, and 77 (30%) had non-sustained graft survival. At baseline, compared with patients with non-sustained graft survival, those with sustained graft survival had longer median type 1 diabetes duration (33·5 years [IQR 24·3-41·7] vs 26·2 years [17·0-35·5]; p=0·0003), median older age (49·4 years [43·5-56·1] vs 44·2 years [35·4-54·2]; p=0·0011), and lower median insulin requirements (0·53 units/kg per day [0·45-0·67] vs 0·59 units/kg per day [0·48-0·70]; p=0·032), but median HbA1c concentrations were similar (8·2% [7·5-9·0] vs 8·5% [7·8-9·2]; p=0·23). 201 (79%) recipients had insulin independence, with a Kaplan-Meier estimate of 61% (95% CI 54-67) at 1 year, 32% (25-39) at 5 years, 20% (14-27) at 10 years, 11% (6-18) at 15 years, and 8% (2-17) at 20 years. Patients with sustained graft survival had significantly higher rates of insulin independence (160 [90%] of 178 vs 41 [53%] of 77; p<0·0001) and sustained improvements in glycaemic control mixed-main-effects model group effect, p<0·0001) compared with those with non-sustained graft survival. Multivariate analyses identified the combined use of anakinra plus etanercept (adjusted odds ratio 7·5 [95% CI 2·7-21·0], p<0·0001) and the BETA-2 score of 15 or higher (4·1 [1·5-11·4], p=0·0066) as factors associated with sustained graft survival. In recipients with sustained graft survival, the incidence of procedural complications was lower (23 [5%] of 443 infusions vs 17 [10%] of 167 infusions; p=0·027), whereas the incidence of cancer was higher (29 of [16%] of 178 vs four [5%] of 77; p=0·015) than in those with non-sustained graft survival; most were skin cancers (22 [67%] of 33). End-stage renal disease and severe infections were similar between groups.

INTERPRETATION

We present the largest single-centre cohort study of long-term outcomes following islet transplantation. Although some limitations with our study remain, such as the retrospective component, a relatively small sample size, and the absence of non-transplant controls, we found that the combined use of anakinra plus etanercept and the BETA-2 score were associated with improved outcomes, and therefore these factors could inform clinical practice.

FUNDING

None.

A modified surgical procedure using minimally invasive ileocolic vein perfusion in a mouse intrahepatic islet transplant model

Murine intrahepatic islet transplantation is a clinically relevant but technically challenging surgical procedure because of frequent lethal postoperative bleeding. Here, we describe a protocol for mouse pancreatic islet isolation, purification, and culture. Besides, we also describe a protocol for intrahepatic islet transplantation through the ileocolic vein. Intrahepatic islet transplantation through the ileocolic vein, as opposed to traditional islet perfusion via the main portal vein, has the advantage of improving recovery after surgery and may facilitate islet survival and function in preclinical settings. For complete details on the use and execution of this protocol, please refer to Shrestha et al. (2020).

Pharmacological management of patients undergoing total pancreatectomy with auto-islet transplantation

Chronic pancreatitis results in permanent parenchymal destruction of the pancreas gland leading to anatomical and physiological consequences for patients. Surgical management varies, and some patients require total pancreatectomy with autologous islet cell transplantation (TPIAT). Patients undergoing TPIAT require complex and diligent management after surgery. This encompasses the management of glucose control (endocrine function of the pancreas) and supplementing loss of exocrine function of the pancreas with digestive enzymes. Other areas of management include optimizing pain relief while reducing narcotic usage, providing antimicrobial prophylaxis, and reducing loss of islet cells by improving its integrity through anticoagulation and use of anti-inflammatory agents. Each aspect of care is unique to this population. However, comprehensive reviews on its pharmacological management are scarce. This review will discuss the available literature to date surrounding all aspects of pharmacological management of patients undergoing TPIAT.

Advanced cell therapy with low tissue factor loaded product NestaCell® does not confer thrombogenic risk for critically ill COVID-19 heparin-treated patients

Since the COVID-19 pandemic started, mesenchymal stromal cells (MSC) appeared as a therapeutic option to reduce the over-activated inflammatory response and promote recovery of lung damage. Most clinical studies use intravenous injection for MSC delivery, raising several concerns of thrombogenic risk due to MSC procoagulant activity (PCA) linked to the expression of tissue factor (TF/CD142). This is the first study that demonstrated procoagulant activity of TF+ human immature dental pulp stromal cells (hIDPSC, NestaCell® product) with the percentage of TF+ cells varied from 0.2% to 63.9% in plasma of healthy donors and COVID-19 heparin-treated patients. Thrombogenic risk of TF+ hIDPSCs was evaluated by rotational thromboelastometry (in vitro) and in critically ill COVID-19 patients (clinical trial). We showed that the thromboelastography is not enough to predict the risk of TF+ MSC therapies. Using TF-negative HUVEC cells, we demonstrated that TF is not a unique factor responsible for the cell's procoagulant activity. However, heparin treatment minimizes MSC procoagulant (in vitro). We also showed that the intravenous infusion of hIDPSCs with prophylactic enoxaparin administration in moderate to critically ill COVID-19 patients did not change the values of D-dimer, neither in the PT and PTT times. Our COVID-19 clinical study measured and selected the therapeutic cells with low TF (less than 25% of TF+ hIDPSCs). Our data indicate that the concomitant administration of enoxaparin and low TF-loaded is safe even for critically ill COVID-19 patients.

Perfusion-Based Recellularization of Rat Livers with Islets of Langerhans

Purpose

Artificial organs might serve as alternative solutions for whole organ transplantation. Decellularization of a liver provides a non-immunogenic matrix with the advantage of three afferent systems, the portal vein, the hepatic artery and the bile duct. This study aims to evaluate the recellularization of rat livers with islets of Langerhans via the bile duct and the portal vein for the comparison of different perfusion routes.

Methods

Rat livers were decellularized in a pressure-controlled perfusion manner and repopulated with intact isolated islets of Langerhans via either the portal vein or the bile duct.

Results

Repopulation via the portal vein showed islet clusters stuck within the vascular system demonstrated by ellipsoid borders of thick reticular tissue around the islet cluster in Azan staining. After recellularization via the bile duct, islets were distributed close to the vessels within the parenchymal space and without a surrounding reticular layer. Large clusters of islets had a diameter of up to 1000 µm without clear shapes.

Conclusion

We demonstrated the bile duct to be superior to the portal vein for repopulation of a decellularized rat liver with islets of Langerhans. This technique may serve as a bioengineering platform to generate an implantable and functional endocrine neo-pancreas and provide scaffolds with the anatomic benefit of three afferent systems to facilitate co-population of cells.

Effects of different routes of heparin on instant blood-mediated inflammatory reaction after portal vein islet transplantation

OBJECTIVES

Heparin is mainly used as an anticoagulant in clinic, and it also has a certain anti-inflammatory effect. At present, after portal vein islet transplantation in diabetic patients, heparin is mainly infused through the peripheral veins of the limbs to achieve the purpose of anticoagulation and protection of the graft, rather than through the portal vein. In this study, animal experiments were conducted to investigate the effect of heparin infusion via the portal vein and marginal ear vein on the instant blood-mediated inflammatory reaction (IBMIR) after portal vein islet transplantation, which is the choice of anticoagulation methods for clinical islet transplantation to provide a basis for decision-making.

METHODS

A total of 50 neonatal pigs (Xeno-1 type, 3-5 days) were selected. Islets were isolated and purified from the pancreas of neonatal pigs. Ten non-diabetic Landrace pigs (1.5-2.0 months) served as recipients, and 12 000 IEQ/kg neonatal porcine islets were transplanted into the liver through the portal vein. All recipients received bolus injection of 50 U/kg of heparin 10 minutes before transplantation. After the bolus injection of heparin, the experimental group received heparin via the portal vein [10 U/(kg·h), 5 recipients], and the control group received heparin via the marginal ear vein [10 U/(kg·h), 5 recipients]. The superior vena cava blood was collected from the 2 groups pre-operation at 1, 3, 24 h post-operation of the transplantation. The portal vein blood was collected from the experimental group at 1 and 3 h after the transplantation as well. The levels of complement C3a, C5a, thrombin-antithrombin complex (TAT), β-thromboglobulin (β-TG), and D-dimer as well as activated partial thromboplastin time (APTT) in superior vena cava blood from 1 and 3 h post-transplantation were detected in the 2 groups, and the levels of anti-Xa and anti-IIa in the portal vein and superior vena cava blood from 1 and 3 h post-transplantation in the experimental group were detected. Twenty four hours after the transplantation, the liver tissues in the 2 groups were collected for pathological examination to observe the inflammatory cell infiltration and peripheral thrombosis around the islets graft in liver.

RESULTS

Before transplantation, there was no statistically significant difference in C3a, C5a, TAT, β-TG, D-dimer levels and APTT between the 2 groups (all P>0.05). At 1 and 3 h after transplantation, the C3a, TAT, and D-dimer levels in the experimental group were significant decreased than those in the control groups (all P<0.05), and at 3 h after transplantation the C5a was significant decreased than that in the control group (P<0.05). At 1 and 3 h after transplantation, the anti-Xa and anti-IIa levels in the portal vein blood were significantly increased than those in the superior vena cava blood in the experimental group (all P<0.05). Pathological results showed the presence of islet cell clusters in the liver blood vessels. The thrombus formation and neutrophil infiltration around islet graft was not obvious in the experimental group, while massive thrombus formation and neutrophil infiltration in the control group.

CONCLUSIONS

Compared with marginal ear vein infusion of heparin, the direct infusion of heparin in the portal vein has a certain inhibitory effect on complement system, coagulation system activation and inflammatory cell infiltration in portal vein islet transplantation, which may attenuate the occurrence of IBMIR.

Portal Vein Thrombosis May Be More Strongly Associated With Islet Infusion Than Extreme Thrombocytosis After Total Pancreatectomy With Islet Autotransplantation

BACKGROUND

Total pancreatectomy with islet autotransplantation (TPIAT) involves pancreatectomy, splenectomy, and reinjection of the patient's pancreatic islets into the portal vein. This process triggers a local inflammatory reaction and increase in portal pressure, threatening islet survival and potentially causing portal vein thrombosis. Recent research has highlighted a high frequency of extreme thrombocytosis (platelets ≥1000 × 109/L) after TPIAT, but its cause and association with thrombotic risk remain unclear.

METHODS

This retrospective single-site study of a contemporary cohort of 409 pediatric and adult patients analyzed the frequency of thrombocytosis, risk factors for thrombosis, and antiplatelet and anticoagulation strategies.

RESULTS

Of 409 patients, 67% developed extreme thrombocytosis, peaking around postoperative day 16. Extreme thrombocytosis was significantly associated with infused islet volumes. Thromboembolic events occurred in 12.2% of patients, with portal vein thromboses occurring significantly earlier than peripheral thromboses. Portal vein thromboses were associated with infused islet volumes and portal pressures but not platelet counts or other measures. Most thromboembolic events (82.7%) occurred before the postoperative day of maximum platelet count. Only 4 of 27 (14.8%) of portal vein thromboses occurred at platelet counts ≥500 × 109/L. Perioperative heparin was given to all patients. Treatment of reactive thrombocytosis using aspirin in adults and hydroxyurea in children was not associated with significantly decreased thromboembolic risk.

CONCLUSIONS

These results suggest that post-TPIAT thrombocytosis and portal vein thromboses may be linked to the islet infusion inflammation, not directly to each other, and further reducing this inflammation may reduce thrombosis and thrombocytosis frequencies simultaneously.

Challenges, highlights, and opportunities in cellular transplantation: A white paper of the current landscape

Although cellular transplantation remains a relatively small field compared to solid organ transplantation, the prospects for advancement in basic science and clinical care remain bountiful. In this review, notable historical events and the current landscape of the field of cellular transplantation are reviewed with an emphasis on islets (allo- and xeno-), hepatocytes (including bioartificial liver), adoptive regulatory immunotherapy, and stem cells (SCs, specifically endogenous organ-specific and mesenchymal). Also, the nascent but rapidly evolving field of three-dimensional bioprinting is highlighted, including its major processing steps and latest achievements. To reach its full potential where cellular transplants are a more viable alternative than solid organ transplants, fundamental change in how the field is regulated and advanced is needed. Greater public and private investment in the development of cellular transplantation is required. Furthermore, consistent with the call of multiple national transplant societies for allo-islet transplants, the oversight of cellular transplants should mirror that of solid organ transplants and not be classified under the unsustainable, outdated model that requires licensing as a drug with the Food and Drug Administration. Cellular transplantation has the potential to bring profound benefit through progress in bioengineering and regenerative medicine, limiting immunosuppression-related toxicity, and providing markedly reduced surgical morbidity.

Hypoparathyroidism: State of the Art on Cell and Tissue Therapies

Hypoparathyroidism is an endocrine disorder characterized by low serum calcium levels, high serum phosphorus levels, and by inappropriate or absent secretion of the parathyroid hormone (PTH). The most common therapeutic strategy to treat this condition is hormone replacement therapy with calcium and vitamin D but, unfortunately, in the long term this treatment may not be sufficient to compensate for the loss of endocrine function. Glandular autotransplantation is considered the most effective technique in place of replacement therapy. Although it leads to excellent results in most cases, autotransplantation is not always possible. Allograft is a good way to treat patients who have not been able to undergo autograft, but this technique has limited success due to side effects related to tissue rejection. This therapy is supported by systemic immunosuppression, which leads to the onset of serious side effects in patients, with a risk of endocrine toxicity. Today, research on endocrine disorders is focused on discovering alternative graft therapies that can allow optimal results with the fewest possible side effects. In this review, we will make an update on the current state of the art about the cell and tissue therapy as treatment for hypoparathyroidism, to identify which type of therapeutic strategy could be valid for a future clinical use.

Noninvasive Tracking of mPEG-poly(Ala) Hydrogel-Embedded MIN6 Cells after Subcutaneous Transplantation in Mice

Recently, we demonstrated the feasibility of subcutaneous transplantation of MIN6 cells embedded in a scaffold with poly(ethylene glycol) methyl ether (mPEG)-poly(Ala) hydrogels. In this study, we further tracked these grafts using magnetic resonance (MR) and bioluminescence imaging. After being incubated overnight with chitosan-coated superparamagnetic iron oxide (CSPIO) nanoparticles and then mixed with mPEG-poly(Ala) hydrogels, MIN6 cells appeared as dark spots on MR scans. For in vivo experiments, we transfected MIN6 cells with luciferase and/or incubated them overnight with CSPIO overnight; 5 × 10⁶ MIN6 cells embedded in mPEG-poly(Ala) hydrogels were transplanted into the subcutaneous space of each nude mouse. The graft of CSPIO-labeled MIN6 cells was visualized as a distinct hypointense area on MR images located at the implantation site before day 21. However, this area became hyperintense on MR scans for up to 64 days. In addition, positive bioluminescence images were also observed for up to 64 days after transplantation. The histology of removed grafts showed positive insulin and iron staining. These results indicate mPEG-poly(Ala) is a suitable scaffold for β-cell encapsulation and transplantation. Moreover, MR and bioluminescence imaging are useful noninvasive tools for detecting and monitoring mPEG-poly(Ala) hydrogel-embedded MIN6 cells at a subcutaneous site.

Clinical islet transplantation: Current progress and new frontiers

Islet transplantation (IT) is now a robust treatment for selected patients with type 1 diabetes suffering from recurrent hypoglycemia and impaired awareness of hypoglycemia. A global soar of clinical islet transplant programs attests to the commitment of many institutions and researchers to advance IT as a potential cure for this devastating disease. However, many challenges limiting the widespread applicability of clinical IT remain. In this review, we will touch on the milestones in the history of IT and its path to clinical success, discuss the current challenges around IT, propose some possible solutions, and elaborate on the frontiers envisioned in the future of clinical IT.

The Utility of Exosomes in Diagnosis and Therapy of Diabetes Mellitus and Associated Complications

Diabetes mellitus and the associated complications are metabolic diseases with high morbidity that result in poor quality of health and life. The lack of diagnostic methods for early detection results in patients losing the best treatment opportunity. Oral hypoglycemics and exogenous insulin replenishment are currently the most common therapeutic strategies, which only yield temporary glycemic control rather than curing the disease and its complications. Exosomes are nanoparticles containing bioactive molecules reflecting individual physiological status, regulating metabolism, and repairing damaged tissues. They function as biomarkers of diabetes mellitus and diabetic complications. Considering that exosomes are bioactive molecules, can be obtained from body fluid, and have cell-type specificity, in this review, we highlight the multifold effects of exosomes in the pathology and therapy of diabetes mellitus and diabetic complications.

Portal flow dynamics after total pancreatectomy and autologous islet cell transplantation

BACKGROUND

Portal vein thrombosis (PVT) is a serious complication of total pancreatectomy and autologous islet cell transplant (TPAIT); therefore, portal flow dynamics are monitored by Doppler ultrasound postoperatively. The practical value of scheduled Doppler ultrasound examinations and the relationship between portal vein velocity, liver function, and complications have not been clearly studied.

METHODS

A retrospective review of 16 TPAIT was performed. Correlation analysis of portal vein velocity with indices of liver function, portal pressure, and volume of islet cells infused was conducted.

RESULTS

There was no correlation between portal vein velocity and postoperative liver function tests (LFTs). Larger volume of islet cells infused and higher intraoperative portal pressure correlated with decreased postoperative portal flow. There was no significant difference in portal pressure, portal vein velocity, or LFTs between those with normal and abnormal pre-infusion liver histopathology. While no PVT occurred, there were two cases of postoperative bleeding related to anticoagulation.

CONCLUSION

Segmental portal vein velocities are low in the setting of high tissue volume and portal pressure, but are not associated with variation in LFTs. Therefore, patient management in response to changes in velocities without clinical symptoms may be unnecessary.

Islet transplantation in the subcutaneous space achieves long-term euglycaemia in preclinical models of type 1 diabetes

The intrahepatic milieu is inhospitable to intraportal islet allografts^1-3, limiting their applicability for the treatment of type 1 diabetes. Although the subcutaneous space represents an alternate, safe and easily accessible site for pancreatic islet transplantation, lack of neovascularization and the resulting hypoxic cell death have largely limited the longevity of graft survival and function and pose a barrier to the widespread adoption of islet transplantation in the clinic. Here we report the successful subcutaneous transplantation of pancreatic islets admixed with a device-free islet viability matrix, resulting in long-term euglycaemia in diverse immune-competent and immuno-incompetent animal models. We validate sustained normoglycaemia afforded by our transplantation methodology using murine, porcine and human pancreatic islets, and also demonstrate its efficacy in a non-human primate model of syngeneic islet transplantation. Transplantation of the islet-islet viability matrix mixture in the subcutaneous space represents a simple, safe and reproducible method, paving the way for a new therapeutic paradigm for type 1 diabetes.

Considerations for an Alternative Site of Islet Cell Transplantation

Islet cell transplantation has been limited most by poor graft survival. Optimizing the site of transplantation could improve clinical outcomes by minimizing required donor cells, increasing graft integration, and simplifying the transplantation and monitoring process. In this article, we review the history and significant human and animal data for clinically relevant sites, including the liver, spleen, and kidney subcapsule, and identify promising new sites for further research. While the liver was the first studied site and has been used the most in clinical practice, the majority of transplanted islets become necrotic. We review the potential causes for graft death, including the instant blood-mediated inflammatory reaction, exposure to immunosuppressive agents, and low oxygen tension. Significant research exists on alternative sites for islet cell transplantation, suggesting a promising future for patients undergoing pancreatectomy.

Erythropoietin accelerates the revascularization of transplanted pancreatic islets

BACKGROUND AND PURPOSE

Pancreatic islet transplantation is a promising therapeutic approach for Type 1 diabetes. A major prerequisite for the survival of grafted islets is a rapid revascularization after transplantation. Erythropoietin (EPO), the primary regulator of erythropoiesis, has been shown to promote angiogenesis. Therefore, we investigated in this study whether EPO improves the revascularization of transplanted islets.

EXPERIMENTAL APPROACH

Islets from FVB/N mice were transplanted into dorsal skinfold chambers of recipient animals, which were daily treated with an intraperitoneal injection of EPO (500 IU·kg^-1 ) or vehicle (control) throughout an observation period of 14 days. In a second set of experiments, animals were only pretreated with EPO over a 6-day period prior to islet transplantation. The revascularization of the grafts was assessed by repetitive intravital fluorescence microscopy and immunohistochemistry. In addition, a streptozotocin-induced diabetic mouse model was used to study the effect of EPO-pretreatment on the endocrine function of the grafts.

KEY RESULTS

EPO treatment slightly accelerated the revascularization of the islet grafts. This effect was markedly more pronounced in EPO-pretreated animals, resulting in significantly higher numbers of engrafted islets and an improved perfusion of endocrine tissue without affecting systemic haematocrit levels when compared with controls. Moreover, EPO-pretreatment significantly accelerated the recovery of normoglycaemia in diabetic mice after islet transplantation.

CONCLUSION AND IMPLICATIONS

These findings demonstrate that, particularly, short-term EPO-pretreatment represents a promising therapeutic approach to improve the outcome of islet transplantation, without an increased risk of thromboembolic events.

Real-Time, Intraoperative Doppler/Ultrasound Monitoring of Islet Infusion During Total Pancreatectomy With Islet Autotransplant: A First Report

Chronic pancreatitis (CP), secondary to a wide variety of etiologies, is a progressive and irreversible disease. Initially, CP is managed with endoscopic interventions, long-term analgesia for its associated chronic abdominal pain syndrome and pancreatic enzyme replacement for exocrine dysfunction. As the disease advances, pancreatic drainage procedures and partial resections are considered, but they leave diseased tissue behind and usually result in short-term relief only. Total pancreatectomy alone is widely viewed as a last resort treatment option because it causes brittle diabetes mellitus. However, total pancreatectomy with islet autotransplantation (TPIAT) can prevent the development of diabetes and cure the chronic pain syndrome. One serious, albeit rare, complication of TPIAT is (partial) portal vein thrombosis. Its incidence is probably about 5%. To prevent the occurrence of portal vein thrombosis, we propose herein, and have successfully performed, continuous real-time Doppler ultrasonography during the islet infusion to study portal vein and intrahepatic flow patterns, as well as changes in Doppler signals. Flow and signal changes may allow for timely adjustment of the infusion rate, before a marked increase in portal vein pressure is noted and decrease the risk of portal vein thrombosis.

Thrombogenic Risk Induced by Intravascular Mesenchymal Stem Cell Therapy: Current Status and Future Perspectives

Mesenchymal stem cells (MSCs) are currently studied and used in numerous clinical trials. Nevertheless, some concerns have been raised regarding the safety of these infusions and the thrombogenic risk they induce. MSCs express procoagulant activity (PCA) linked to the expression of tissue factor (TF) that, when in contact with blood, initiates coagulation. Some even describe a dual activation of both the coagulation and the complement pathway, called Instant Blood-Mediated Inflammatory Reaction (IBMIR), explaining the disappointing results and low engraftment rates in clinical trials. However, nowadays, different approaches to modulate the PCA of MSCs and thus control the thrombogenic risk after cell infusion are being studied. This review summarizes both in vitro and in vivo studies on the PCA of MSC of various origins. It further emphasizes the crucial role of TF linked to the PCA of MSCs. Furthermore, optimization of MSC therapy protocols using different methods to control the PCA of MSCs are described.

Islet Transplantation Alone Versus Solitary Pancreas Transplantation: an Outcome-Driven Choice?

PURPOSE OF REVIEW

In patients with type 1 diabetes with extreme glycemic variability, the restoration of pancreas endocrine function is potentially and completely achieved with islets of Langerhans (tissue derived from whole organ) or pancreas (whole organ) transplantation. The aim of our review is to report on the latest studies and to highlight the benefits and risks of the two procedures, providing clearer, more selective, evidence-based clinical indications that also consider the impact on the degenerative complications of diabetes as a potential benefit.

RECENT FINDINGS

Clinical experience in this field has been dynamic over the last three decades, and has been characterized by the development of more standardized protocols and a clearer definition of clinical outcome. On the contrary, the recommendations thus far are not well delineated and tend to overlap, and the past ADA position statement for pancreas transplant alone has also been applied to islet transplant alone, without differentiation. Both outcome-driven and non-outcome-driven criteria are considered in the conclusions, in an attempt to streamline indications for islet-alone or pancreas-alone transplantation.

Pancreatic Islet Transplantation in Humans: Recent Progress and Future Directions

Pancreatic islet transplantation has become an established approach to β-cell replacement therapy for the treatment of insulin-deficient diabetes. Recent progress in techniques for islet isolation, islet culture, and peritransplant management of the islet transplant recipient has resulted in substantial improvements in metabolic and safety outcomes for patients. For patients requiring total or subtotal pancreatectomy for benign disease of the pancreas, isolation of islets from the diseased pancreas with intrahepatic transplantation of autologous islets can prevent or ameliorate postsurgical diabetes, and for patients previously experiencing painful recurrent acute or chronic pancreatitis, quality of life is substantially improved. For patients with type 1 diabetes or insulin-deficient forms of pancreatogenic (type 3c) diabetes, isolation of islets from a deceased donor pancreas with intrahepatic transplantation of allogeneic islets can ameliorate problematic hypoglycemia, stabilize glycemic lability, and maintain on-target glycemic control, consequently with improved quality of life, and often without the requirement for insulin therapy. Because the metabolic benefits are dependent on the numbers of islets transplanted that survive engraftment, recipients of autoislets are limited to receive the number of islets isolated from their own pancreas, whereas recipients of alloislets may receive islets isolated from more than one donor pancreas. The development of alternative sources of islet cells for transplantation, whether from autologous, allogeneic, or xenogeneic tissues, is an active area of investigation that promises to expand access and indications for islet transplantation in the future treatment of diabetes.

Portal Vein Thrombosis After Total Pancreatectomy and Islet Autotransplant: Prophylaxis and Graft Impact

OBJECTIVES

To determine the rate of portal vein thrombosis (PVT) based on pharmacologic prophylaxis protocol and the impact of PVT on islet graft function after total pancreatectomy with islet autotransplantation (TPIAT).

METHODS

We compared the incidence of PVT, postsurgical bleeding, and thrombotic complications in patients undergoing TPIAT between 2001 and 2018 at the University of Minnesota who received either unfractionated heparin (UFH) or enoxaparin for postoperative PVT prophylaxis. Six-month and 1-year graft function was compared between patients who developed PVT and those who did not.

RESULTS

Twelve patients (6.6%) developed a PVT, which resolved by 6 months after TPIAT in 10 patients. There was no statistically significant difference in PVT rate between patients who received UFH or enoxaparin for prophylaxis (P = 0.54). Patients who received enoxaparin developed other thrombotic complications more often (6% vs 0%, P = 0.02). Islet graft function did not differ in patients who developed PVT versus those who did not.

CONCLUSIONS

There was no difference between enoxaparin or UFH prophylaxis in preventing PVT, but there may be a higher incidence of other thrombotic complications with enoxaparin. In the setting of routine screening and anticoagulation therapy, PVT is a self-limited process.

Ascites formation accompanied by portal vein thrombosis after porcine islet xenotransplantation via the portal vein in Rhesus macaque (Macaca mulatta)

Pig-to-nonhuman primate (NHP) islet transplantation has been widely conducted as a preclinical xenotransplantation model prior to human clinical trial. Portal vein thrombosis is one of the complications associated with islet infusion through the portal vein into the liver. Here, we briefly report severe case of ascites formation accompanied by portal vein thrombi after pig-to-NHP islet xenotransplantation in a rhesus monkey. Meticulous prophylactic treatment such as continuous heparin infusion should be implemented to prevent portal vein thrombi in pig-to-NHP islet transplantation models.

The liver surface as a favorable site for islet cell sheet transplantation in type 1 diabetes model mice

INTRODUCTION

Islet transplantation is one of the most promising therapeutic approaches for patients with severe type 1 diabetes mellitus (T1DM). Transplantation of engineered islet cell sheets holds great potential for treating T1DM as it enables the creation of stable neo-islet tissues. However, a large mass of islet cell sheets is required for the subcutaneous transplantation to reverse hyperglycemia in diabetic mice. Here, we investigated whether the liver surface could serve as an alternative site for islet cell sheet transplantation.

METHODS

Dispersed rat islet cells (0.8 × 106 cells) were cultured on laminin-332-coated thermoresponsive culture dishes. After 2 days of cultivation, we harvested the islet cell sheets by lowering the culture temperature using a support membrane with a gelatin gel. We transplanted two recovered islet cell sheets into the subcutaneous space or onto the liver surface of severe combined immunodeficiency (SCID) mice with streptozocin-induced diabetes.

RESULTS

In the liver surface group, the non-fasting blood glucose level decreased rapidly within several days after transplantation. In marked contrast, the hyperglycemia state was maintained in the subcutaneous space transplantation group. The levels of rat C-peptide and insulin in the liver surface group were significantly higher than those in the subcutaneous space group. An immunohistological analysis confirmed that most of the islet cells engrafted on the liver surface were insulin-positive. The CD31-positive endothelial cells formed vascular networks within the neo-islets and in the surrounding tissues. In contrast, viable islet cells were not found in the subcutaneous space group.

CONCLUSIONS

Compared with the subcutaneous space, a relatively small mass of islet cell sheets was enough to achieve normoglycemia in diabetic mice when the liver surface was selected as the transplantation site. Our results demonstrate that the optimization of the transplantation site for islet cell sheets leads to significant improvements in the therapeutic efficiency for T1DM.

Beta Cell Death by Cell-free DNA and Outcome After Clinical Islet Transplantation

BACKGROUND

Optimizing engraftment and early survival after clinical islet transplantation is critical to long-term function, but there are no reliable, quantifiable measures to assess beta cell death. Circulating cell-free DNA (cfDNA) derived from beta cells has been identified as a novel biomarker to detect cell loss and was recently validated in new-onset type 1 diabetes and in islet transplant patients.

METHODS

Herein we report beta cell cfDNA measurements after allotransplantation in 37 subjects and the correlation with clinical outcomes.

RESULTS

A distinctive peak of cfDNA was observed 1 hour after transplantation in 31 (83.8%) of 37 subjects. The presence and magnitude of this signal did not correlate with transplant outcome. The 1-hour signal represents dead beta cells carried over into the recipient after islet isolation and culture, combined with acute cell death post infusion. Beta cell cfDNA was also detected 24 hours posttransplant (8/37 subjects, 21.6%). This signal was associated with higher 1-month insulin requirements (P = 0.04), lower 1-month stimulated C-peptide levels (P = 0.01), and overall worse 3-month engraftment, by insulin independence (receiver operating characteristic-area under the curve = 0.70, P = 0.03) and beta 2 score (receiver operating characteristic-area under the curve = 0.77, P = 0.006).

CONCLUSIONS

cfDNA-based estimation of beta cell death 24 hours after islet allotransplantation correlates with clinical outcome and could predict early engraftment.

An engineered cell sheet composed of human islets and human fibroblast, bone marrow-derived mesenchymal stem cells, or adipose-derived mesenchymal stem cells: An in vitro comparison study

BACKGROUND

We previously reported the utility of engineered cell sheets composed of human islets and supporting cells in vitro and in vivo. It is unclear which type of supporting cell is most suitable for constructing cell sheets with human islets. The present study aimed to compare human fibroblasts, bone marrow-derived mesenchymal stem cells (BM-MSCs), and adipose-derived mesenchymal stem cells (ADSCs) as a supporting source for cell sheets.

METHODS

Engineered cell sheets were fabricated with human islets using human fibroblasts, BM-MSCs, or ADSCs as supporting cells. The islet viability, recovery rate, glucose-stimulated insulin release (determined by the stimulation index), and cytokine secretion (TGF-β1, IL-6, and VEGF) of groups-including an islet-alone group as a control-were compared.

RESULTS

All three sheet groups consistently exhibited higher viability, recovery rate, and stimulation index values than the islet-alone group. The ADSC group showed the highest viability and recovery rate among the three sheet groups. There were no discernible differences in the stimulation index values of the groups. The fibroblast group exhibited significantly higher TGF-β1 values in comparison to the other groups. The IL-6 level of the ADSC group was more than five times higher than that of the other groups. The ADSC group showed the VEGF level; however, it did not differ from that of the BM-MSC group to a statistically significant extent.

CONCLUSION

Engineered cell sheets composed of islets and supporting cells had a cytoprotective effect on islets. These results suggest that individual cell types could be a more attractive source for crafting engineered cell sheets in comparison to islets alone.

The journey of islet cell transplantation and future development

Intraportal islet transplantation has proven to be efficacious in preventing severe hypoglycemia and restoring insulin independence in selected patients with type 1 diabetes. Multiple islet infusions are often required to achieve and maintain insulin independence. Many challenges remain in clinical islet transplantation, including substantial islet cell loss early and late after islet infusion. Contributions to graft loss include the instant blood-mediated inflammatory reaction, potent host auto- and alloimmune responses, and beta cell toxicity from immunosuppressive agents. Protective strategies are being tested to circumvent several of these events including exploration of alternative transplantation sites, stem cell-derived insulin producing cell therapies, co-transplantation with mesenchymal stem cells or exploration of novel immune protective agents. Herein, we provide a brief introduction and history of islet cell transplantation, limitations associated with this procedure and methods to alleviate islet cell loss as a means to improve engraftment outcomes.

An engineered macroencapsulation membrane releasing FTY720 to precondition pancreatic islet transplantation

Macroencapsulation is a powerful approach to increase the efficiency of extrahepatic pancreatic islet transplant. FTY720, a small molecule that activates signaling through sphingosine-1-phosphate receptors, is immunomodulatory and pro-angiogenic upon sustained delivery from biomaterials. While FTY720 (fingolimod, Gilenya) has been explored for organ transplantation, in the present work the effect of locally released FTY720 from novel nanofiber-based macroencapsulation membranes is explored for islet transplantation. We screened islet viability during culture with FTY720 and various biodegradable polymers. Islet viability is significantly reduced by the addition of high doses (≥500 ng/mL) of soluble FTY720. Among the polymers screened, islets have the highest viability when cultured with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Therefore, PHBV was blended with polycaprolactone (PCL) for mechanical stability and electrospun into nanofibers. Islets had no detectable function ex vivo following 5 days or 12 h of subcutaneous implantation within our engineered device. Subsequently, we explored a preconditioning scheme in which islets are transplanted 2 weeks after FTY720-loaded nanofibers are implanted. This allows FTY720 to orchestrate a local regenerative milieu while preventing premature transplantation into avascular sites that contain high concentrations of FTY720. These results provide a foundation and motivation for further investigation into the use of FTY720 in preconditioning sites for efficacious islet transplantation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 555-568, 2018.

Autologous Mesenchymal Stem Cell and Islet Cotransplantation: Safety and Efficacy

Islet engraftment after transplantation is impaired by high rates of islet/β cell death caused by cellular stressors and poor graft vascularization. We studied whether cotransplantation of ex vivo expanded autologous bone marrow-derived mesenchymal stem cells (MSCs) with islets is safe and beneficial in chronic pancreatitis patients undergoing total pancreatectomy with islet autotransplantation. MSCs were harvested from the bone marrow of three islet autotransplantation patients and expanded at our current Good Manufacturing Practices (cGMP) facility. On the day of islet transplantation, an average dose of 20.0 ± 2.6 ×106 MSCs was infused with islets via the portal vein. Adverse events and glycemic control at baseline, 6, and 12 months after transplantation were compared with data from 101 historical control patients. No adverse events directly related to the MSC infusions were observed. MSC patients required lower amounts of insulin during the peritransplantation period (p = .02 vs. controls) and had lower 12-month fasting blood glucose levels (p = .02 vs. controls), smaller C-peptide declines over 6 months (p = .01 vs. controls), and better quality of life compared with controls. In conclusion, our pilot study demonstrates that autologous MSC and islet cotransplantation may be a safe and potential strategy to improve islet engraftment after transplantation. (Clinicaltrials.gov registration number: NCT02384018). Stem Cells Translational Medicine 2018;7:11-19.

The Optimal Timing for Pancreatic Islet Transplantation into Subcutaneous Scaffolds Assessed by Multimodal Imaging

Subcutaneously implanted polymeric scaffolds represent an alternative transplantation site for pancreatic islets (PIs) with the option of vascularisation enhancement by mesenchymal stem cells (MSC). Nevertheless, a proper timing of the transplantation steps is crucial. In this study, scaffolds supplemented with plastic rods were implanted into diabetic rats and two timing schemes for subsequent transplantation of bioluminescent PIs (4 or 7 days after rod removal) were examined by multimodal imaging. The cavities were left to heal spontaneously or with 10 million injected MSCs. Morphological and vascularisation changes were examined by MRI, while the localisation and viability of transplanted islets were monitored by bioluminescence imaging. The results show that PIs transplanted 4 days after rod removal showed the higher optical signal and vascularisation compared to transplantation after 7 days. MSCs slightly improved vascularisation of the graft but hindered therapeutic efficiency of PIs. Long-term glycaemia normalisation (4 months) was attained in 80% of animals. In summary, multimodal imaging confirmed the long-term survival and function of transplanted PIs in the devices. The best outcome was reached with PIs transplanted on day 4 after rod removal and therefore the suggested protocol holds a potential for further applications.

Multimodal Imaging Reveals Improvement of Blood Supply to an Artificial Cell Transplant Site Induced by Bioluminescent Mesenchymal Stem Cells

PURPOSE

An artificial site for cell or pancreatic islet transplantation can be created using a polymeric scaffold, even though it suffers subcutaneously from improper vascularisation. A sufficient blood supply is crucial for graft survival and function and can be enhanced by transplantation of mesenchymal stem cells (MSCs). The purpose of this study was to assess the effect of syngeneic MSCs on neoangiogenesis and cell engraftment in an artificial site by multimodal imaging.

PROCEDURES

MSCs expressing a gene for luciferase were injected into the artificial subcutaneous site 7 days after scaffold implantation. MRI experiments (anatomical and dynamic contrast-enhanced images) were performed on a 4.7-T scanner using gradient echo sequences. Bioluminescent images were acquired on an IVIS Lumina optical imager. Longitudinal examination was performed for 2 months, and one animal was monitored for 16 months.

RESULTS

We confirmed the long-term presence (lasting more than 16 months) of viable donor cells inside the scaffolds using bioluminescence imaging with an optical signal peak appearing on day 3 after MSC implantation. When compared to controls, the tissue perfusion and vessel permeability in the scaffolds were significantly improved at the site with MSCs with a maximal peak on day 9 after MSC transplantation.

CONCLUSIONS

Our data suggest that the maximal signal obtained by bioluminescence and magnetic resonance imaging from an artificially created site between 3 and 9 days after MSC transplantation can predict the optimal time range for subsequent cellular or tissue transplantation, including pancreatic islets.

The greater omentum as a site for pancreatic islet transplantation

The greater omentum is a highly vascularized anatomical structure in the peritoneal cavity. Its main components are connective, adipose and vascular cells, along with specialized immune cells. The omentum functions as a site for fat accumulation, it has adhesive properties to control traumatized and inflamed tissues, and a function in local hemostasis, immune responses, and revascularization. Other functions include the absorption of fluids, the phagocytosis of particulate matter, and foreign body reaction. The omentum is catalyzing significant interest for its potential as a site for pancreatic islet and cell transplantation. Our knowledge about this structure, its functions, and its potential as a site for transplantation is poised to grow in the coming years.

Clinical pancreatic islet transplantation

Clinical pancreatic islet transplantation can be considered one of the safest and least invasive transplant procedures. Remarkable progress has occurred in both the technical aspects of islet cell processing and the outcomes of clinical islet transplantation. With >1,500 patients treated since 2000, this therapeutic strategy has moved from a curiosity to a realistic treatment option for selected patients with type 1 diabetes mellitus (that is, those with hypoglycaemia unawareness, severe hypoglycaemic episodes and glycaemic lability). This Review outlines the techniques required for human islet isolation, in vitro culture before the transplant and clinical islet transplantation, and discusses indications, optimization of recipient immunosuppression and management of adjunctive immunomodulatory and anti-inflammatory strategies. The potential risks, long-term outcomes and advances in treatment after the transplant are also discussed to further move this treatment towards becoming a more widely available option for patients with type 1 diabetes mellitus and eventually a potential cure.

Total Pancreatectomy With Islet Autotransplantation Resolves Pain in Young Children With Severe Chronic Pancreatitis

OBJECTIVES

Fear of diabetes and major surgery may prohibit referral of young children severely affected by pancreatitis for total pancreatectomy with islet autotransplant (TPIAT). We evaluated outcomes in our youngest TPIAT recipients, 3 to 8 years of age at surgery.

METHODS

Medical records were reviewed for 17 children (9 girls) ages 8 years or younger undergoing TPIAT from 2000 to 2014. Most (14/17) had genetic risk factors for pancreatitis. Since 2006, TPIAT recipients were followed prospectively with health questionnaires including assessments of pain and narcotic use, and scheduled hemoglobin A1c (HbA1c) and mixed-meal tolerance tests (6 mL/kg Boost HP) before surgery, and at regular intervals after. Patients are 1 to 11 years post-TPIAT (median 2.2 years). Data are reported as median (25th, 75th percentile).

RESULTS

All had relief of pain, with all 17 patients off narcotics at most recent follow-up. Hospitalization rates decreased from 5.0 hospitalization episodes per person-year of follow-up before TPIAT, to 0.35 episodes per person-year of follow-up after TPIAT. Fourteen (82%) discontinued insulin, higher than the observed insulin independence rate of 41% in 399 patients older than 8 years of age undergoing TPIAT over the same interval (P = 0.004). Median post-TPIAT HbA1c was 5.9% (5.6%, 6.3%), and within patient post-TPIAT mean HbA1c was ≤6.5% for all but 2 patients.

CONCLUSIONS

Young children with severe refractory chronic pancreatitis may be good candidates for TPIAT, with high rates of pain relief and insulin independence, and excellent glycemic control in the majority.

Single-donor islet transplantation in type 1 diabetes: patient selection and special considerations

Type 1 diabetes mellitus is an autoimmune disorder of the endocrine pancreas that currently affects millions of people in the United States. Although the disease can be managed with exogenous insulin administration, the ultimate cure for the condition lies in restoring a patient's ability to produce their own insulin. Islet cell allotransplantation provides a means of endogenous insulin production. Though far from perfected, islet transplants are now a proven treatment for type 1 diabetics. However, proper patient selection is critical for achieving optimal outcomes. Given the shortage of transplantable organs, selecting appropriate candidates for whom the procedure will be of greatest benefit is essential. Although many of those who receive islets do not retain insulin independence, grafts do play a significant role in preventing hypoglycemic episodes that can be quite detrimental to quality of life and potentially fatal. Additionally, islet transplant requires lifelong immunosuppression. Antibodies, both preformed and following islet infusion, may play important roles in graft outcomes. Finally, no procedure is without inherent risk and islet transfusions can have serious consequences for recipients' livers in the form of both vascular and metabolic complications. Therefore, patient-specific factors that should be taken into account before islet transplantation include aims of therapy, sensitization, and potential increased risk for hepatic and portal-venous sequelae.

Engineering an endocrine Neo-Pancreas by repopulation of a decellularized rat pancreas with islets of Langerhans

Decellularization of pancreata and repopulation of these non-immunogenic matrices with islets and endothelial cells could provide transplantable, endocrine Neo- Pancreata. In this study, rat pancreata were perfusion decellularized and repopulated with intact islets, comparing three perfusion routes (Artery, Portal Vein, Pancreatic Duct). Decellularization effectively removed all cellular components but conserved the pancreas specific extracellular matrix. Digital subtraction angiography of the matrices showed a conserved integrity of the decellularized vascular system but a contrast emersion into the parenchyma via the decellularized pancreatic duct. Islets infused via the pancreatic duct leaked from the ductular system into the peri-ductular decellularized space despite their magnitude. TUNEL staining and Glucose stimulated insulin secretion revealed that islets were viable and functional after the process. We present the first available protocol for perfusion decellularization of rat pancreata via three different perfusion routes. Furthermore, we provide first proof-of-concept for the repopulation of the decellularized rat pancreata with functional islets of Langerhans. The presented technique can serve as a bioengineering platform to generate implantable and functional endocrine Neo-Pancreata.