Stable renal function after islet transplantation: importance of patient selection and aggressive clinical management

Allo Beta Cell transplantation: specific features, unanswered questions, and immunological challenge

Type 1 diabetes (T1D) presents a persistent medical challenge, demanding innovative strategies for sustained glycemic control and enhanced patient well-being. Beta cells are specialized cells in the pancreas that produce insulin, a hormone that regulates blood sugar levels. When beta cells are damaged or destroyed, insulin production decreases, which leads to T1D. Allo Beta Cell Transplantation has emerged as a promising therapeutic avenue, with the goal of reinstating glucose regulation and insulin production in T1D patients. However, the path to success in this approach is fraught with complex immunological hurdles that demand rigorous exploration and resolution for enduring therapeutic efficacy. This exploration focuses on the distinct immunological characteristics inherent to Allo Beta Cell Transplantation. An understanding of these unique challenges is pivotal for the development of effective therapeutic interventions. The critical role of glucose regulation and insulin in immune activation is emphasized, with an emphasis on the intricate interplay between beta cells and immune cells. The transplantation site, particularly the liver, is examined in depth, highlighting its relevance in the context of complex immunological issues. Scrutiny extends to recipient and donor matching, including the utilization of multiple islet donors, while also considering the potential risk of autoimmune recurrence. Moreover, unanswered questions and persistent gaps in knowledge within the field are identified. These include the absence of robust evidence supporting immunosuppression treatments, the need for reliable methods to assess rejection and treatment protocols, the lack of validated biomarkers for monitoring beta cell loss, and the imperative need for improved beta cell imaging techniques. In addition, attention is drawn to emerging directions and transformative strategies in the field. This encompasses alternative immunosuppressive regimens and calcineurin-free immunoprotocols, as well as a reevaluation of induction therapy and recipient preconditioning methods. Innovative approaches targeting autoimmune recurrence, such as CAR Tregs and TCR Tregs, are explored, along with the potential of stem stealth cells, tissue engineering, and encapsulation to overcome the risk of graft rejection. In summary, this review provides a comprehensive overview of the inherent immunological obstacles associated with Allo Beta Cell Transplantation. It offers valuable insights into emerging strategies and directions that hold great promise for advancing the field and ultimately improving outcomes for individuals living with diabetes.

Cell Therapy for Type 1 Diabetes: From Islet Transplantation to Stem Cells

The field of cell therapy of type 1 diabetes is a particularly interesting example in the scenario of regenerative medicine. In fact, β-cell replacement has its roots in the experience of islet transplantation, which began 40 years ago and is currently a rapidly accelerating field, with several ongoing clinical trials using β cells derived from stem cells. Type 1 diabetes is particularly suitable for cell therapy as it is a disease due to the deficiency of only one cell type, the insulin-producing β cell, and this endocrine cell does not need to be positioned inside the pancreas to perform its function. On the other hand, the presence of a double immunological barrier, the allogeneic one and the autoimmune one, makes the protection of β cells from rejection a major challenge. Until today, islet transplantation has taught us a lot, pioneering immunosuppressive therapies, graft encapsulation, tissue engineering, and test of different implant sites and has stimulated a great variety of studies on β-cell function. This review starts from islet transplantation, presenting its current indications and the latest published trials, to arrive at the prospects of stem cell therapy, presenting the latest innovations in the field.

Felix dies natalis, insulin… ceterum autem censeo "beta is better"

One hundred years after its discovery, insulin remains the life-saving therapy for many patients with diabetes. It has been a 100-years-old success story thanks to the fact that insulin therapy has continuously integrated the knowledge developed over a century. In 1982, insulin becomes the first therapeutic protein to be produced using recombinant DNA technology. The first "mini" insulin pump and the first insulin pen become available in 1983 and 1985, respectively. In 1996, the first generation of insulin analogues were produced. In 1999, the first continuous glucose-monitoring device for reading interstitial glucose was approved by the FDA. In 2010s, the ultra-long action insulins were introduced. An equally exciting story developed in parallel. In 1966. Kelly et al. performed the first clinical pancreas transplant at the University of Minnesota, and now it is a well-established clinical option. First successful islet transplantations in humans were obtained in the late 1980s and 1990s. Their ability to consistently re-establish the endogenous insulin secretion was obtained in 2000s. More recently, the possibility to generate large numbers of functional human β cells from pluripotent stem cells was demonstrated, and the first clinical trial using stem cell-derived insulin producing cell was started in 2014. This year, the discovery of this life-saving hormone turns 100 years. This provides a unique opportunity not only to celebrate this extraordinary success story, but also to reflect on the limits of insulin therapy and renew the commitment of the scientific community to an insulin free world for our patients.

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.

Islet transplantation attenuates cardiac fibrosis in diabetic rats through inhibition of TGF-β1/Smad3 pathway

Although islet transplantation has been identified as a promising endocrine replacement treatment for patient with diabetes mellitus (DM), it still remains unclear whether islet transplantation can inhibit the diabetic-induced myocardial injury and subsequent adverse ventricular remodeling. Here, we sought to explore the molecular mechanism underlying the cardioprotective effect of islet transplantation. We established the diabetic rat model by intraperitoneal injection of STZ, which was followed by either islet transplantation or conventional insulin treatment. Compared with insulin treatment, islet transplantation further reduced the elevated blood glucose which was nearly restored to normoglycaemia. In addition, islet transplantation attenuated the increased levels of cTn-I and CK-MB, cleaved-caspase-3 in response to DM, and ameliorated diabetic-induced cardiac hypertrophy and interstitial fibrosis, along with improved extracellular matrix (ECM) deposition. Moreover, diabetic rats that underwent islet transplantation had lower expression of TGF-β1 and lower phosphorylation levels of Smad3. Therefore, islet transplantation exerted protective effect against diabetic-induced myocardial injury and fibrotic remodeling through deactivation of TGF-β₁/Smad3 signaling pathway.

Pancreas Islet Transplantation for Patients With Type 1 Diabetes Mellitus: A Clinical Evidence Review

BACKGROUND

Type 1 diabetes mellitus is caused by the autoimmune destruction of pancreatic beta (β) cells, resulting in severe insulin deficiency. Islet transplantation is a β-cell replacement therapeutic option that aims to restore glycemic control in patients with type 1 diabetes. The objective of this study was to determine the clinical effectiveness of islet transplantation in patients with type 1 diabetes, with or without kidney disease.

METHODS

We conducted a systematic review of the literature on islet transplantation for type 1 diabetes, including relevant health technology assessments, systematic reviews, meta-analyses, and observational studies. We used a two-step process: first, we searched for systematic reviews and health technology assessments; second, we searched primary studies to update the chosen health technology assessment. The Assessment of Multiple Systematic Reviews measurement tool was used to examine the methodological quality of the systematic reviews and health technology assessments. We assessed the quality of the body of evidence and the risk of bias according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria.

RESULTS

Our searched yielded 1,354 citations. One health technology assessment, 11 additional observational studies to update the health technology assessment, one registry report, and four guidelines were included; the observational studies examined islet transplantation alone, islet-after-kidney transplantation, and simultaneous islet-kidney transplantation. In general, low to very low quality of evidence exists for islet transplantation in patients with type 1 diabetes with difficult-to-control blood glucose levels, with or without kidney disease, for these outcomes: health-related quality of life, secondary complications of diabetes, glycemic control, and adverse events. However, high quality of evidence exists for the specific glycemic control outcome of insulin independence compared with intensive insulin therapy. For patients without kidney disease, islet transplantation improves glycemic control and diabetic complications for patients with type 1 diabetes when compared with intensive insulin therapy. However, results for health-related quality of life outcomes were mixed, and adverse events were increased compared with intensive insulin therapy. For patients with type 1 diabetes with kidney disease, islet-after-kidney transplantation or simultaneous islet-kidney transplantation also improved glycemic control and secondary diabetic complications, although the evidence was more limited for this patient group. Compared with intensive insulin therapy, adverse events for islet-after-kidney transplantation or simultaneous islet-kidney transplantation were increased, but were in general less severe than with whole pancreas transplantation.

CONCLUSIONS

For patients with type 1 diabetes with difficult-to-control blood glucose levels, islet transplantation may be a beneficial β-cell replacement therapy to improve glycemic control and secondary complications of diabetes. However, there is uncertainty in the estimates of effectiveness because of the generally low to very low quality of evidence for all outcomes of interest.

Early alteration of kidney function in nonuremic type 1 diabetic islet transplant recipients under tacrolimus-mycophenolate therapy

BACKGROUND

Transplant patients on tacrolimus therapy exhibit a reduced glomerular filtration rate (GFR). The type of graft and immune treatment protocol may influence the extent and reversibility of this side effect.

METHODS

The present single-center study is conducted in 48 nonuremic type 1 diabetic recipients of an intraportal islet-cell graft under maintenance immunosuppression (IS) with tacrolimus and mycophenolate mofetil. Estimated GFR (eGFR) and albuminuria were followed up to 5 years posttransplantation.

RESULTS

Mean eGFR values decreased by 19 mL/min/1.73 m after 1 to 2 weeks of IS (P<0.0001) and then remained stable throughout the complete treatment period. The decrease was related to predose trough tacrolimus concentrations or doses and disappeared upon its discontinuation; it was also associated with the presence of albuminuria at the time of transplantation. Tacrolimus treatment resulted in a reduction of albuminuria; its discontinuation restored albuminuria to the initial levels.

CONCLUSIONS

The use of tacrolimus in our islet-cell transplant protocol caused an initial 20% reduction in eGFR, which was reversible following its discontinuation, at least within the 5-year follow-up period. The associated reduction in albuminuria was also reversible, compatible with a tacrolimus-induced preglomerular vasoconstriction. These observations support further use of our tacrolimus regimen in this patient population.

Clinical application of microencapsulated islets: actual prospectives on progress and challenges

After 25 years of intense pre-clinical work on microencapsulated intraperitoneal islet grafts into non-immunosuppressed diabetic recipients, the application of this procedure to patients with type 1 diabetes mellitus has been a significant step forward. This result, achieved in a few centers worldwide, underlies the safety of biopolymers used for microencapsulation. Without this advance, no permission for human application of microcapsules would have ever been obtained after years of purification technologies applied to the raw alginates. To improve safety of the encapsulated islet graft system, renewed efforts on the capsules' bioengineering, as well as on insulin-producing cells within the capsular membranes, are in progress. It is hoped that advances in these two critical aspects of the cell encapsulation technology will result in wider human application of this system.

Can improved glycemic control slow renal function decline at all stages of diabetic nephropathy?

Observational studies have shown the strong association between level of glycemic control and the key outcome measure, risk of glomerular filtration rate (GFR) loss rather than subsequent course of albumin excretion, in type 1 diabetes patients at all stages of nephropathy. However, it has not been clear if clinical interventions designed to normalize glycemic control are equally effective at all stages, such as primary prevention in normoalbuminuric patients, secondary prevention in microalbuminuria and macroalbuminuria, or tertiary prevention aimed at slowing or reversing further loss of GFR once impaired. Substantial randomized controlled trial data from the Diabetes Control and Complications Trial and Epidemiology of Diabetes Interventions and Complications exists to support postponement, but not outright prevention, of GFR loss in normoalbuminuric patients. Although secondary and tertiary prevention systematic studies are limited to methodologically insufficient insulin pump and transplantation trials, the reversal of advanced glomerular lesions observed in whole-pancreas transplant recipients who experienced long-term glycemic normalization offers convincing support for further research into glycemic interventions specifically for GFR preservation. In light of existing literature, we encourage the design of secondary and tertiary prevention trials that incorporate biomarker methods for identifying patients at highest risk of GFR loss because interventions to normalize hyperglycemia are resource-intensive and may be applied unnecessarily to clinical populations at low long-term GFR loss risk.

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

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

Impact of islet transplantation on diabetes complications and quality of life

Insulin represents a life-saving therapy for patients with type 1 diabetes but, despite appropriate treatment, it prevents only partially long-term diabetic complications, while generating fatal hypoglycemic episodes. Islet transplantation gained attention because of its safety, effectiveness, and minimal invasiveness; however it remains a procedure reserved for a selected group of patients. The introduction of the Edmonton Protocol in 2000, based on a newly designed steroid-free immunosuppressive protocol, revamped the course of islet transplantation. The main goal of islet transplantation remains insulin independence, although the effect of islet transplantation can be more comprehensively evaluated in terms of frequency of hypoglycemic episodes and impact on diabetic complications and quality of life. Islet transplantation was shown to have positive consequences on cardiovascular, renal, neurologic, and ocular diabetic complications. The proof of concept for cellular replacement therapy in diabetes has been established with islet transplantation, it only needs to be improved and rendered widely available.

Nonalbumin proteinuria in islet transplant recipients

The aim of this study was to evaluate the importance of nonalbumin-predominant proteinuria on kidney function (KF) after islet transplantation (ITx). Twenty-four-hour proteinuria and albuminuria were available in 27 recipients. KF was assessed by serum creatinine and estimated glomerular filtration rate (eGFR) was calculated by Modification of Diet in Renal Disease formula. Correlations between eGFR and albuminuria (r = -0.422, p < 0.001) were higher than with proteinuria (r = -0.223, p < 0.001; p = 0.006 for comparison between correlations). Nineteen (70%) subjects had proteinuria >or= 300 mg/24 h during the follow-up. Subjects were divided into three groups according to urinary protein excretion patterns: no proteinuria (n = 8), nonalbumin-predominant (n = 8), and albumin-predominant (n = 11) proteinuria. Proteinuria >or= 500 mg/24 h was observed only among patients with albumin-predominant proteinuria (64%; p = 0.002) and these patients had the lowest eGFR means post-ITx (no proteinuria: 84.2 +/- 16.4 vs. nonalbumin: 69.1 +/- 13.8 vs. albumin-predominant proteinuria: 65.5 +/- 16.6 ml/min/1.73 m(2), p = 0.044 for first vs. last group). In conclusion, high frequency of proteinuria was observed after ITx. However, it seems to be milder and have less impact on KF when albumin is not the major source of proteinuria. Prospective evaluation of proteinuria, including tubular function markers, should be performed to elucidate the mechanisms of kidney damage in this population.