Justifying clinical trials for porcine islet xenotransplantation

In vitro induced pluripotency from urine-derived cells in porcine

BACKGROUND

The generation of induced pluripotent stem cells (iPSC) has been a game-changer in translational and regenerative medicine; however, their large-scale applicability is still hampered by the scarcity of accessible, safe, and reproducible protocols. The porcine model is a large biomedical model that enables translational applications, including gene editing, long term in vivo and offspring analysis; therefore, suitable for both medicine and animal production.

AIM

To reprogramme in vitro into pluripotency, and herein urine-derived cells (UDCs) were isolated from porcine urine.

METHODS

The UDCs were reprogrammed in vitro using human or murine octamer-binding transcription factor 4 (OCT4), SRY-box2 (SOX2), Kruppel-like factor 4 (KLF4), and C-MYC, and cultured with basic fibroblast growth factor (bFGF) supplementation. To characterize the putative porcine iPSCs three clonal lineages were submitted to immunocytochemistry for alkaline phosphatase (AP), OCT4, SOX2, NANOG, TRA1 81 and SSEA 1 detection. Endogenous transcripts related to the pluripotency (OCT4, SOX2 and NANOG) were analyzed via reverse transcription quantitative real-time polymerase chain reaction in different time points during the culture, and all three lineages formed embryoid bodies (EBs) when cultured in suspension without bFGF supplementation.

RESULTS

The UDCs were isolated from swine urine samples and when at passage 2 submitted to in vitro reprogramming. Colonies of putative iPSCs were obtained only from UDCs transduced with the murine factors (mOSKM), but not from human factors (hOSKM). Three clonal lineages were isolated and further cultured for at least 28 passages, all the lineages were positive for AP detection, the OCT4, SOX2, NANOG markers, albeit the immunocytochemical analysis also revealed heterogeneous phenotypic profiles among lineages and passages for NANOG and SSEA1, similar results were observed in the abundance of the endogenous transcripts related to pluripotent state. All the clonal lineages when cultured in suspension without bFGF were able to form EBs expressing ectoderm and mesoderm layers transcripts.

CONCLUSION

For the first time UDCs were isolated in the swine model and reprogrammed into a pluripotent-like state, enabling new numerous applications in both human or veterinary regenerative medicine.

Neonatal Pig Sertoli Cells Survive Xenotransplantation by Creating an Immune Modulatory Environment Involving CD4 and CD8 Regulatory T Cells

The acute cell-mediated immune response presents a significant barrier to xenotransplantation. Immune-privileged Sertoli cells (SC) can prolong the survival of co-transplanted cells including xenogeneic islets, hepatocytes, and neurons by protecting them from immune rejection. Additionally, SC survive as allo- and xenografts without the use of any immunosuppressive drugs suggesting elucidating the survival mechanism(s) of SC could be used to improve survival of xenografts. In this study, the survival and immune response generated toward neonatal pig SC (NPSC) or neonatal pig islets (NPI), nonimmune-privileged controls, was compared after xenotransplantation into naïve Lewis rats without immune suppression. The NPSC survived throughout the study, while NPI were rejected within 9 days. Analysis of the grafts revealed that macrophages and T cells were the main immune cells infiltrating the NPSC and NPI grafts. Further characterization of the T cells within the grafts indicated that the NPSC grafts contained significantly more cluster of differentiation 4 (CD4) and cluster of differentiation 8 (CD8) regulatory T cells (Tregs) at early time points than the NPI grafts. Additionally, the presence of increased amounts of interleukin 10 (IL-10) and transforming growth factor (TGF) β and decreased levels of tumor necrosis factor (TNF) α and apoptosis in the NPSC grafts compared to NPI grafts suggests the presence of regulatory immune cells in the NPSC grafts. The NPSC expressed several immunoregulatory factors such as TGFβ, thrombospondin-1 (THBS1), indoleamine-pyrrole 2,3-dioxygenase, and galectin-1, which could promote the recruitment of these regulatory immune cells to the NPSC grafts. In contrast, NPI grafts had fewer Tregs and increased apoptosis and inflammation (increased TNFα, decreased IL-10 and TGFβ) suggestive of cytotoxic immune cells that contribute to their early rejection. Collectively, our data suggest that a regulatory graft environment with regulatory immune cells including CD4 and CD8 Tregs in NPSC grafts could be attributed to the prolonged survival of the NPSC xenografts.

Comparison of the Effects of Liraglutide on Islet Graft Survival Between Local and Systemic Delivery

Islet transplantation has emerged as a promising treatment for type 1 diabetes mellitus. Liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, protects beta cells after islet transplantation by improving glycemic control through several mechanisms. In this study, we compared the effects of local pretreatment and systemic treatment with liraglutide on islet transplantation in a diabetic mouse model. Streptozotocin (STZ)-induced diabetic C57BL/6 mice were transplanted with syngeneic islets under the kidney capsule. Isolated islets were either locally treated with liraglutide before transplantation or mice were treated systemically by intraperitoneal injection after islet transplantation. Local pretreatment of islets with liraglutide was more effective in increasing body weight, decreasing hemoglobin A1c levels, and lowering blood glucose levels in STZ-diabetic mice transplanted with islets. Local pretreatment was also more effective in increasing insulin secretion and islet survival in STZ-diabetic mice. Histological analysis of the transplantation site revealed fewer apoptotic cells following local pretreatment compared with systemic injection of liraglutide. These findings indicate that liraglutide administered once locally before transplantation might have superior effects on islet preservation than systemic administration.

Selection of a novel AAV2/TNFAIP3 vector for local suppression of islet xenograft inflammation

BACKGROUND

Neonatal porcine islets (NPIs) can restore glucose control in mice, pigs, and non-human primates, representing a potential abundant alternative islet supply for clinical beta cell replacement therapy. However, NPIs are vulnerable to inflammatory insults that could be overcome with genetic modifications. Here, we demonstrate in a series of proof-of-concept experiments the potential of the cytoplasmic ubiquitin-editing protein A20, encoded by the TNFAIP3 gene, as an NPI cytoprotective gene.

METHODS

We forced A20 expression in NPI grafts using a recombinant adenovirus 5 (Ad5) vector and looked for impact on TNF-stimulated NF-κB activation and NPI graft function. As adeno-associated vectors (AAV) are clinically preferred vectors but exhibit poor transduction efficacy in NPIs, we next screened a series of AAV serotypes under different transduction protocols for their ability achieve high transduction efficiency and suppress NPI inflammation without impacting NPI maturation.

RESULTS

Forcing the expression of A20 in NPI with Ad5 vector blocked NF-κB activation by inhibiting IκBα phosphorylation and degradation, and reduced the induction of pro-inflammatory genes Cxcl10 and Icam1. A20-expressing NPIs also exhibited superior functional capacity when transplanted into diabetic immunodeficient recipient mice, evidenced by a more rapid return to euglycemia and improved GTT compared to unmodified NPI grafts. We found AAV2 combined with a 14-day culture period maximized NPI transduction efficiency (>70% transduction rate), and suppressed NF-κB-dependent gene expression without adverse impact upon NPI maturation.

CONCLUSION

We report a new protocol that allows for high-efficiency genetic modification of NPIs, which can be utilized to introduce candidate genes without the need for germline engineering. This approach would be suitable for preclinical and clinical testing of beneficial molecules. We also report for the first time that A20 is cytoprotective for NPI, such that A20 gene therapy could aid the clinical development of NPIs for beta cell replacement.

Recent progress in porcine islet isolation, culture and engraftment strategies for xenotransplantation

PURPOSE OF REVIEW

Xenotransplantation of porcine islets is a realistic option to restore β-cell function in type 1 diabetic patients. Among other factors, such as islet donor age (fetal, neonatal and adult) and genotype (wild type and genetically modified), choice of the transplantation site, and immune protection of the islets, efficient strategies for islet isolation, culture and engraftment are critical for the success of islet xenotransplantation.

RECENT FINDINGS

Neonatal porcine islets (NPIs) are immature at isolation and need to be matured in vitro or in vivo before they become fully functional. Recent developments include a scalable protocol for isolation of clinically relevant batches of NPIs and a stepwise differentiation protocol for directed maturation of NPIs. In addition, different sources of mesenchymal stem cells were shown to support survival and functional maturation of NPIs in vitro and in various transplantation models in vivo.

SUMMARY

A plethora of different culture media and supplements have been tested; however, a unique best culture system for NPIs is still missing. New insights, for example from single-cell analyses of islets or from stem cell differentiation toward β cells may help to optimize culture of porcine islets for xenotransplantation in an evidence-based manner.

Cost and Scalability Analysis of Porcine Islet Isolation for Islet Transplantation: Comparison of Juvenile, Neonatal and Adult Pigs

The limited availability of human islets has led to the examination of porcine islets as a source of clinically suitable tissue for transplantation in patients with diabetes mellitus. Islets from porcine donors are commonly used in both in vitro and in vivo experiments studying diabetes mellitus. However, there are significant differences in quality and quantity of islet yield depending on donor pig age, as well as substantial differences in the costs of pancreas procurement in adult versus neonatal and juvenile pigs. In this study, we compared the total cost per islet of juvenile pig pancreata with that of neonatal and adult pigs. Although adult porcine pancreata yield, on average, more than five times the amount of islets than do juvenile and neonatal pancreata, we found that the high price of adult pigs led to the cost per islet being more than twice that of juvenile and neonatal islets (US $0.09 vs $0.04 and $0.02, respectively). In addition, neonatal and juvenile islets are advantageous in their scalability and retention of viability after culture. Our findings indicate that isolating neonatal and juvenile porcine islets is more cost-effective and scalable than isolating adult porcine islets.

β Cell Replacement Therapy: The Next 10 Years

β cell replacement with either pancreas or islet transplantation has progressed immensely over the last decades with current 1- and 5-year insulin independence rates of approximately 85% and 50%, respectively. Recent advances are largely attributed to improvements in immunosuppressive regimen, donor selection, and surgical technique. However, both strategies are compromised by a scarce donor source. Xenotransplantation offers a potential solution by providing a theoretically unlimited supply of islets, but clinical application has been limited by concerns for a potent immune response against xenogeneic tissue. β cell clusters derived from embryonic or induced pluripotent stem cells represent another promising unlimited source of insulin producing cells, but clinical application is pending further advances in the function of the β cell like clusters. Exciting developments and rapid progress in all areas of β cell replacement prompted a lively debate by members of the young investigator committee of the International Pancreas and Islet Transplant Association at the 15th International Pancreas and Islet Transplant Association Congress in Melbourne and at the 26th international congress of The Transplant Society in Hong Kong. This international group of young investigators debated which modality of β cell replacement would predominate the landscape in 10 years, and their arguments are summarized here.

The Future of Islet Transplantation Is Now

Milestones in the history of diabetes therapy include the discovery of insulin and successful methods of beta cell replacement including whole pancreas and islet cell transplantation options. While pancreas transplantation remains the gold standard for patients who have difficulty controlling their symptoms with exogenous insulin, islet allotransplantation is now able to provide similar results with some advantages that make it an attractive potential alternative. The Edmonton Protocol, which incorporated a large dose of islets from multiple donors with steroid-free immunosuppression helped to establish the modern era of islet transplantation almost 20 years ago. While islet allotransplantation is recognized around the world as a powerful clinical therapy for type 1 diabetes it is not yet recognized by the Federal Drug Administration of the United States. Large-scale clinical trials administered by the Clinical Islet Transplantation Consortium have recently demonstrated that the well-regulated manufacture of a human islet product transplanted into patients with difficult to control type 1 diabetes and with a history of severe hyperglycemic episodes can safely and efficaciously maintain glycemic balance and eliminate the most severe complications associated with diabetes. The results of these clinical trials have established a strong basis for licensure of clinical islet allotransplantation in the US. Recognition by the Federal Drug Administration would likely lead to third party reimbursement for islet allotransplantation as a therapeutic option in the United States and would make the treatment available to many more patients. The high costs of rampant diabetes justify the expense of the treatment, which is in-line with the costs of clinical pancreas transplantation. While much enthusiasm and hope is raised toward the development and optimization of stem cell therapy, the islet transplantation community should push toward licensure, if that means broader access of this procedure to patients who may benefit from it. Even as we prepare to take the first steps in that direction, we must acknowledge the new challenges that a shift from the experimental to clinical will bring. Clinical islet allotransplantation in the United States would be a game-changing event in the treatment of type 1 diabetes and also generate enthusiasm for continued research.

Early barriers to neonatal porcine islet engraftment in a dual transplant model

Porcine islet xenografts have the potential to provide an inexhaustible source of islets for β cell replacement. Proof-of-concept has been established in nonhuman primates. However, significant barriers to xenoislet transplantation remain, including the poorly understood instant blood-mediated inflammatory reaction and a thorough understanding of early xeno-specific immune responses. A paucity of data exist comparing xeno-specific immune responses with alloislet (AI) responses in primates. We recently developed a dual islet transplant model, which enables direct histologic comparison of early engraftment immunobiology. In this study, we investigate early immune responses to neonatal porcine islet (NPI) xenografts compared with rhesus islet allografts at 1 hour, 24 hours, and 7 days. Within the first 24 hours after intraportal infusion, we identified greater apoptosis (caspase 3 activity and TUNEL [terminal deoxynucleotidyl transferase dUTP nick end labeling])-positive cells) of NPIs compared with AIs. Macrophage infiltration was significantly greater at 24 hours compared with 1 hour in both NPI (wild-type) and AIs. At 7 days, IgM and macrophages were highly specific for NPIs (α1,3-galactosyltransferase knockout) compared with AIs. These findings demonstrate an augmented macrophage and antibody response toward xenografts compared with allografts. These data may inform future immune or genetic manipulations required to improve xenoislet engraftment.

Regenerative medicine and cell-based approaches to restore pancreatic function

The pancreas is a complex organ with exocrine and endocrine components. Many pathologies impair exocrine function, including chronic pancreatitis, cystic fibrosis and pancreatic ductal adenocarcinoma. Conversely, when the endocrine pancreas fails to secrete sufficient insulin, patients develop diabetes mellitus. Pathology in either the endocrine or exocrine pancreas results in devastating economic and personal consequences. The current standard therapy for treating patients with type 1 diabetes mellitus is daily exogenous insulin injections, but cell sources of insulin provide superior glycaemic regulation and research is now focused on the goal of regenerating or replacing β cells. Stem-cell-based models might be useful to study exocrine pancreatic disorders, and mesenchymal stem cells or secreted factors might delay disease progression. Although the standards that bioengineered cells must meet before being considered as a viable therapy are not yet established, any potential therapy must be acceptably safe and functionally superior to current therapies. Here, we describe progress and challenges in cell-based methods to restore pancreatic function, with a focus on optimizing the site for cell delivery and decreasing requirements for immunosuppression through encapsulation. We also discuss the tools and strategies being used to generate exocrine pancreas and insulin-producing β-cell surrogates in situ and highlight obstacles to clinical application.

Regulation of Clinical Xenotransplantation-Time for a Reappraisal

The continual critical shortage of organs and cells from deceased human donors has stimulated research in the field of cross-species transplantation (xenotransplantation), with the pig selected as the most suitable potential source of organs. Since the US Food and Drug Administration concluded a comprehensive review of xenotransplantation in 2003, considerable progress has been made in the experimental laboratory to improve cell and organ xenograft survival in several pig-to-nonhuman primate systems that offer the best available models to predict clinical outcomes. Survival of heart, kidney, and islet grafts in nonhuman primates is now being measured in months or even years. The potential risks associated with xenotransplantation, for example, the transfer of an infectious microorganism, that were highlighted in the 2003 Food and Drug Administration guidance and subsequent World Health Organization consensus documents have been carefully studied and shown to be either less likely than previously thought or readily manageable by donor selection or recipient management strategies. In this context, we suggest that the national regulatory authorities worldwide should re-examine their guidelines and regulations regarding xenotransplantation, so as to better enable design and conduct of safe and informative clinical trials of cell and organ xenotransplantation when and as supported by the preclinical data. We identify specific topics that we suggest require reconsideration.

The Different Faces of the Pancreatic Islet

Type 1 diabetes (T1D) patients who receive pancreatic islet transplant experience significant improvement in their quality-of-life. This comes primarily through improved control of blood sugar levels, restored awareness of hypoglycemia, and prevention of serious and potentially life-threatening diabetes-associated complications, such as kidney failure, heart and vascular disease, stroke, nerve damage, and blindness. Therefore, beta cell replacement through transplantation of isolated islets is an important option in the treatment of T1D. However, lasting success of this promising therapy depends on durable survival and efficacy of the transplanted islets, which are directly influenced by the islet isolation procedures. Thus, isolating pancreatic islets with consistent and reliable quality is critical in the clinical application of islet transplantation.Quality of isolated islets is important in pre-clinical studies as well, as efforts to advance and improve clinical outcomes of islet transplant therapy have relied heavily on animal models ranging from rodents, to pigs, to nonhuman primates. As a result, pancreatic islets have been isolated from these and other species and used in a variety of in vitro or in vivo applications for this and other research purposes. Protocols for islet isolation have been somewhat similar across species, especially, in mammals. However, given the increasing evidence about the distinct structural and functional features of human and mouse islets, using similar methods of islet isolation may contribute to inconsistencies in the islet quality, immunogenicity, and experimental outcomes. This may also contribute to the discrepancies commonly observed between pre-clinical findings and clinical outcomes. Therefore, it is prudent to consider the particular features of pancreatic islets from different species when optimizing islet isolation protocols.In this chapter, we explore the structural and functional features of pancreatic islets from mice, pigs, nonhuman primates, and humans because of their prevalent use in nonclinical, preclinical, and clinical applications.

Production of high-quality islets from goettingen minipigs: Choice of organ preservation solution, donor pool, and optimal cold ischemia time

BACKGROUND

The transplantation of porcine islets into man might soon become reality for patients with type 1 diabetes mellitus. Therefore, porcine islets of high quality and quantity, and a scalable isolation process with strict quality control will be an unconditional prerequisite to enable the best possible transplantation graft. In this study, we provide a comparative study evaluating islet isolation outcome and in vitro survival based upon donor age, organ preservation solution (OPS), and cold ischemia time (CIT).

METHODS

Goettingen minipigs of younger age (1 year) and retired breeder animals (3.5 years) were studied. Pancreata were harvested according to the standards of human organ retrieval including in situ cold perfusion with either Custodiol^® -HTK or Belzer^® UW solution. Pancreatic tissue was characterized by quantification of apoptotic cells. Islet isolations were performed according to a modified Ricordi method, and isolation outcome was assessed by determining islet particle numbers (IP), islet equivalents (IEQ), and isolation factor (IF). Isolated islets were cultured for 24 and 48 h for the assessment of in vitro survival.

RESULTS

Islet viability was significantly higher in Custodiol^® -HTK preserved pancreas organs compared to Belzer^® UW. Furthermore, organs harvested from retired breeder preserved in Custodiol^® -HTK resulted in stable islet isolation yields even after prolonged CIT and showed superior survival rates of islets in vitro compared to the Belzer^® UW group. Younger porcine donor organs resulted generally in lower islet yield and survival rates.

CONCLUSIONS

In summary, Custodiol^® -HTK solution should be preferred over Belzer^® UW solution for the preservation of pancreata from porcine origin. Custodiol^® -HTK allows for maintaining islet viability and promotes reproducible isolation outcome and survival even after longer CIT. The usage of retired breeder animals over young animals for islet isolation is highly advisable to yield high quality and quantity.

In Vivo Imaging of Transplanted Pancreatic Islets

The beta-cells in the islets of Langerhans in the pancreas secrete insulin and play an important role in glucose homeostasis. Diabetes, characterized by hyperglycemia, results from an absolute or a relative deficiency of the pancreatic beta-cell mass. Islet transplantation has been considered to be a useful therapeutic approach, but it is largely unsuccessful because most of the transplanted islets are lost in the early stage of transplantation. To evaluate the efficacy of intervention methods for the improvement of islet survival, monitoring of the functional islet mass is needed. Various techniques to image and track transplanted islets have been investigated to assess islets after transplantation. In this review, recent progresses in imaging methods to visualize islets are discussed.

No PERV transmission during a clinical trial of pig islet cell transplantation

Xenotransplantation of pig islet cells is a promising alternative for the treatment of diabetes with insulin and may help to prevent numerous late complications such as blindness and amputation. First encouraging results using porcine islets have been reported in preclinical animal models as well in the first clinical trial in New Zealand. The goal of this manuscript is to examine the biological safety of a second trial performed in Argentina, specifically in regards to the transmission of porcine endogenous retroviruses (PERVs) using improved detection methods As in the first trial encapsulated islet cells from the well-characterised Auckland Island pigs were used. The animals were not genetically modified. The islet cells were transplanted in eight human recipients using a modified clinical protocol. Sera taken at different time points after transplantation (up to 55 weeks) were screened for the presence of antibodies against PERV proteins by Western blot analysis using viral antigens from highly purified virus particles. Positive sera obtained by immunization with recombinant PERV proteins were used as control sera. In none of the patients antibodies against PERV were detected, indicating the absence of infection. In parallel at different time points (up to 113 weeks) white blood cells (WBC) have been tested for PERV DNA, and WBC and plasma for PERV RNA by real-time RT-PCR. All tests were negative. In addition, using primers detecting pig mitochondrial cytochrome oxidase (COX) gene, patients were screened for microchimerism. In summary, the data are further evidence for the safety of pig islet cell transplantation.

Optimizing Porcine Islet Isolation to Markedly Reduce Enzyme Consumption Without Sacrificing Islet Yield or Function

BACKGROUND

Human allogeneic islet transplantation for treatment of type 1 diabetes provides numerous clinical benefits, such as fewer episodes of hypoglycemic unawareness and tighter control of blood glucose levels. Availability of human pancreas for clinical and research use, however, is severely limited. Porcine pancreas offers an abundant source of tissue for optimization of islet isolation methodology and future clinical transplantation, thereby increasing patient access to this potentially lifesaving procedure.

METHODS

Porcine islet isolations were performed using varying amounts of collagenase (7.5, 3.75, or 2.5 Wunsch units per gram tissue) and neutral protease activity (12 000, 6000, or 4000 neutral protease units per gram tissue) and perfusion volumes (1.7 or 0.85 mL/g tissue) to assess their effects on isolation outcomes. Retention of dissociative enzymes within the pancreas during perfusion and digestion was evaluated, along with distribution of the perfusion solution within the tissue.

RESULTS

Reducing enzyme usage by as much as 67% and perfusion volume by 50% led to equally successful islet isolation outcomes when compared with the control group (48 ± 7% of tissue digested and 1088 ± 299 islet equivalents per gram of pancreas vs 47 ± 11% and 1080 ± 512, respectively). Using margin-marking dye in the perfusion solution to visualize enzyme distribution demonstrated that increasing perfusion volume did not improve tissue infiltration.

CONCLUSIONS

Current protocols for porcine islet isolation consume excessive amounts of dissociative enzymes, elevating cost and limiting research and development. These data demonstrate that islet isolation protocols can be optimized to significantly reduce enzyme usage while maintaining yield and function and thus accelerating progress toward clinical application.

Contribution of polymeric materials to progress in xenotransplantation of microencapsulated cells: a review

Cell microencapsulation and subsequent transplantation of the microencapsulated cells require multidisciplinary approaches. Physical, chemical, biological, engineering, and medical expertise has to be combined. Several natural and synthetic polymeric materials and different technologies have been reported for the preparation of hydrogels, which are suitable to protect cells by microencapsulation. However, owing to the frequent lack of adequate characterization of the hydrogels and their components as well as incomplete description of the technology, many results of in vitro and in vivo studies appear contradictory or cannot reliably be reproduced. This review addresses the state of the art in cell microencapsulation with special focus on microencapsulated cells intended for xenotransplantation cell therapies. The choice of materials, the design and fabrication of the microspheres, as well as the conditions to be met during the cell microencapsulation process, are summarized and discussed prior to presenting research results of in vitro and in vivo studies. Overall, this review will serve to sensitize medically educated specialists for materials and technological aspects of cell microencapsulation.

Brief review: cell replacement therapies to treat type 1 diabetes mellitus

Human embryonic stem cells (hESCs) and induced pluripotent cells (iPSCs) have the potential to differentiate into any somatic cell, making them ideal candidates for cell replacement therapies to treat a number of human diseases and regenerate damaged or non-functional tissues and organs. Key to the promise of regenerative medicine is developing standardized protocols that can safely be applied in patients. Progress towards this goal has occurred in a number of fields, including type 1 diabetes mellitus (T1D). During the past 10 years, significant technological advances in hESC/iPSC biochemistry have provided a roadmap to generate sufficient quantities of glucose-responsive, insulin-producing cells capable of eliminating diabetes in rodents. Although many of the molecular mechanisms underlying the genesis of these cells remain to be elucidated, the field of cell-based therapeutics to treat T1D has advanced to the point where the first Phase I/II trials in humans have begun. Here, we provide a concise review of the history of cell replacement therapies to treat T1D from islet transplantations and xenotranplantation, to current work in hESC/iPSC. We also highlight the latest advances in efforts to employ insulin-producing, glucose-responsive β-like cells derived from hESC as therapeutics.

Pancreatic Islets: Methods for Isolation and Purification of Juvenile and Adult Pig Islets

The current situation of organ transplantation is mainly determined by the disbalance between the number of available organs and the number of patients on the waiting list. This obvious dilemma might be solved by the transplantation of porcine organs into human patients. The metabolic similarities which exist between both species made pancreatic islets of Langerhans to that donor tissue which will be most likely transplanted in human recipients. Nevertheless, the successful isolation of significant yields of viable porcine islets is extremely difficult and requires extensive experiences in the field. This review is focussing on the technical challenges, pitfalls and particularities that are associated with the isolation of islets from juvenile and adult pigs considering donor variables that can affect porcine islet isolation outcome.