Sirolimus-induced ulceration of the small bowel in islet transplant recipients: report of two cases

Innovations in bio-engineering and cell-based approaches to address immunological challenges in islet transplantation

Human allogeneic pancreatic islet transplantation is a life-changing treatment for patients with severe Type 1 Diabetes (T1D) who suffer from hypoglycemia unawareness and high risk of severe hypoglycemia. However, intensive immunosuppression is required to prevent immune rejection of the graft, that may in turn lead to undesirable side effects such as toxicity to the islet cells, kidney toxicity, occurrence of opportunistic infections, and malignancies. The shortage of cadaveric human islet donors further limits islet transplantation as a treatment option for widespread adoption. Alternatively, porcine islets have been considered as another source of insulin-secreting cells for transplantation in T1D patients, though xeno-transplants raise concerns over the risk of endogenous retrovirus transmission and immunological incompatibility. As a result, technological advancements have been made to protect transplanted islets from immune rejection and inflammation, ideally in the absence of chronic immunosuppression, to improve the outcomes and accessibility of allogeneic islet cell replacement therapies. These include the use of microencapsulation or macroencapsulation devices designed to provide an immunoprotective environment using a cell-impermeable layer, preventing immune cell attack of the transplanted cells. Other up and coming advancements are based on the use of stem cells as the starting source material for generating islet cells 'on-demand'. These starting stem cell sources include human induced pluripotent stem cells (hiPSCs) that have been genetically engineered to avoid the host immune response, curated HLA-selected donor hiPSCs that can be matched with recipients within a given population, and multipotent stem cells with natural immune privilege properties. These strategies are developed to provide an immune-evasive cell resource for allogeneic cell therapy. This review will summarize the immunological challenges facing islet transplantation and highlight recent bio-engineering and cell-based approaches aimed at avoiding immune rejection, to improve the accessibility of islet cell therapy and enhance treatment outcomes. Better understanding of the different approaches and their limitations can guide future research endeavors towards developing more comprehensive and targeted strategies for creating a more tolerogenic microenvironment, and improve the effectiveness and sustainability of islet transplantation to benefit more patients.

Rapamycin Exacerbates Staphylococcus aureus Pneumonia by Inhibiting mTOR-RPS6 in Macrophages

Purpose

This study aimed to explore the effect of Rapamycin (Rapa) in Staphylococcus aureus (S. aureus) pneumonia and clarify its possible mechanism.

Methods

We investigated the effects of Rapa on S. aureus pneumonia in mouse models and in macrophages cultured in vitro. Two possible mechanisms were investigated: the mTOR-RPS6 pathway phosphorylation and phagocytosis. Furthermore, for the mechanism verification in vivo, mice with specific Mtor knockout in myeloid cells were constructed for pneumonia models.

Results

Rapa exacerbated S. aureus pneumonia in mouse models, promoting chemokines secretion and inflammatory cells infiltration in lung. In vitro, Rapa upregulated the secretion of chemokines and cytokines in macrophages induced by S. aureus. Mechanistically, the mTOR-ribosomal protein S6 (RPS6) pathway in macrophages was phosphorylated in response to S. aureus infection, and the inhibition of RPS6 phosphorylation upregulated the inflammation level. However, Rapa did not increase the phagocytic activity. Accordingly, mice with specific Mtor knockout in myeloid cells experienced more severe S. aureus pneumonia.

Conclusion

Rapa exacerbates S. aureus pneumonia by increasing the inflammatory levels of macrophages. Inhibition of mTOR-RPS6 pathway upregulates the expression of cytokines and chemokines in macrophages, thus increases inflammatory cells infiltration and exacerbates tissue damage.

Symbiotic Firmicutes establish mutualism with the host via innate tolerance and resistance to control systemic immunity

The intestinal microbiota regulates immunity across organ systems. Which symbionts control systemic immunity, the mechanisms they use, and how they avoid widespread inflammatory damage are unclear. We uncover host tolerance and resistance mechanisms that allow Firmicutes from the human microbiota to control systemic immunity without inducing immunopathology. Intestinal processing releases Firmicute glycoconjugates that disseminate, resulting in release of cytokine IL-34 that stimulates macrophages and enhances defenses against pneumonia, sepsis, and meningitis. Despite systemic penetration of Firmicutes, immune homeostasis is maintained through feedback control whereby IL-34-mediated mTORC1 activation in macrophages clears polymeric glycoconjugates from peripheral tissues. Smaller glycoconjugates evading this clearance mechanism are tolerated through sequestration by albumin, which acts as an inflammatory buffer constraining their immunological impact. Without these resistance and tolerance mechanisms, Firmicutes drive catastrophic organ damage and cachexia via IL-1β. This reveals how Firmicutes are safely assimilated into systemic immunity to protect against infection without threatening host viability.

Crohn's disease with dilated cardiomyopathy in a child: An experience with heart transplantation

BACKGROUND

DCM has rarely been reported in children with CD, but is a recognized complication in adults. DCM with uncontrolled heart failure may need heart transplantation, which could be challenging in CD.

CASE DESCRIPTION

We present a 9-year-old female with CD who was diagnosed with DCM and a measured Ejection fraction ~25.8%. She was initiated on heart failure treatment, but continued to have progressive symptoms and underwent bicaval OHT three months after her initial presentation. Her post-operative course was complicated by perforation of the rectosigmoid junction requiring exploratory laparotomy and primary repair of the perforation. This was believed to be secondary to her underlying CD and possibly reperfusion injury after heart transplant. During the first-year post heart transplant, she had 4 episodes of acute cellular rejection. These episodes were treated with high dose steroids with good results. The patient has been in remission from CD since transplantation. For the last two years she is doing well, with no further rejection episodes on current immunosuppression.

CONCLUSION

DCM, though rare, can occur in patients with CD, whether active or in remission. The development of DCM could be insidious and keeping a high index of suspicion is important and subtle signs suggestive of cardiac involvement should warrant further investigation. The post-transplant management can be challenging with early morbidity in the first post-transplant year but overall good median survival and quality of life for our patient to date.

Colovesical fistula: a rare complication after renal transplantation

Colovesical fistula per se is a rare condition and most commonly occurs secondary to diverticular disease in normal patients. Colovesical fistula in the setting of post-renal transplantation is even rarer and very few cases have been reported in literature. Patients with autosomal-dominant polycystic kidney disease (ADPKD) are predisposed to diverticulosis and hence are at a higher risk for fistula formation. Herein, we report a case of colovesical fistula in a renal allograft recipient with ADPKD in the absence of diverticulosis. The patient was successfully operated and is stable with no complications at 1-year follow-up.

Diagnostic Lessons from a Complex Case of Postintestinal Transplantation Enteropathy

Recent advances in the field of intestinal transplantation have been mitigated by the incidence of allograft rejection. In such events, early identification and appropriate timing of antirejection therapy are crucial in retaining graft function. We present the case of a patient who suffered severe postintestinal transplantation allograft enteropathy, primarily characterized by extensive mucosal ulcerations, and was refractory to all conventional therapy. This progressed as chronic rejection; however crucially this was not definitively diagnosed until allograft function had irreversibly diminished. We argue that the difficulties encountered in this case can be attributed to the inability of our current array of investigative studies and diagnostic guidelines to provide adequate clinical guidance. This case illustrates the importance of developing reliable and specific markers for guiding the diagnosis of rejection and the use of antirejection therapeutics in this rapidly evolving field of transplant surgery.

Basiliximab treatment for autoimmune bowel disease in a pediatric heart transplant patient

Autoimmune-mediated bowel disease has been reported after pediatric heart transplantation. Recognition and treatment of these patients has been difficult. We describe a patient who responded to steroids and basiliximab therapy after an inflammatory process secondary to abnormal T-cell activation. Our patient is a 28-month-old female who received a heart transplant at five wk of age. At 24 months post-transplant, she developed fever and bloody stools. Initial investigations were significant for an elevated ESR (>120) and CRP (15.2). Symptoms persisted despite bowel rest and mycophenolate discontinuation. Endoscopic evaluation revealed discontinuous ulcerative disease involving esophagus, terminal ileum, right and left colon, necessitating extensive bowel resection. She had additional airway inflammation leading to a TEF at the site of esophageal ulceration, requiring tracheostomy. Immune evaluation revealed autoimmune dysregulation that responded to parenteral methylprednisolone. Chronic basiliximab therapy allowed for successful weaning of steroids with sustained remission. She has been transitioned to sirolimus and tacrolimus maintenance immunosuppression with plans to discontinue basiliximab once off steroids. In conclusion, bowel disease in the setting of pediatric heart transplantation can be severe and refractory to traditional treatment methods. Tailoring immune therapy to activated T cells can result in remission. Basiliximab therapy was used in our patient to maintain steroid-induced remission, but long-term complications of this disease process are unknown.

Transdisciplinary approach to restore pancreatic islet function

The focus of our research is on islet immunobiology. We are exploring novel strategies that could be of assistance in the treatment and prevention of type 1 diabetes, as well as in the restoration of metabolic control via transplantation of insulin producing cells (i.e., islet cells). The multiple facets of diabetes and β-cell replacement encompass different complementary disciplines, such as immunology, cell biology, pharmacology, and bioengineering, among others. Through their interaction and integration, a transdisciplinary dimension is needed in order to address and overcome all aspects of the complex puzzle toward a successful clinical translation of a biological cure for diabetes.

Profiling sirolimus-induced inflammatory syndrome: a prospective tricentric observational study

Background

The use of the immunosuppressant sirolimus in kidney transplantation has been made problematic by the frequent occurrence of various side effects, including paradoxical inflammatory manifestations, the pathophysiology of which has remained elusive.

Methods

30 kidney transplant recipients that required a switch from calcineurin inhibitor to sirolimus-based immunosuppression, were prospectively followed for 3 months. Inflammatory symptoms were quantified by the patients using visual analogue scales and serum samples were collected before, 15, 30, and 90 days after the switch.

Results

66% of patients reported at least 1 inflammatory symptom, cutaneo-mucosal manifestations being the most frequent. Inflammatory symptoms were characterized by their lability and stochastic nature, each patient exhibiting a unique clinical presentation. The biochemical profile was more uniform with a drop of hemoglobin and a concomitant rise of inflammatory acute phase proteins, which peaked in the serum 1 month after the switch. Analyzing the impact of sirolimus introduction on cytokine microenvironment, we observed an increase of IL6 and TNFα without compensation of the negative feedback loops dependent on IL10 and soluble TNF receptors. IL6 and TNFα changes correlated with the intensity of biochemical and clinical inflammatory manifestations in a linear regression model.

Conclusions

Sirolimus triggers a destabilization of the inflammatory cytokine balance in transplanted patients that promotes a paradoxical inflammatory response with mild stochastic clinical symptoms in the weeks following drug introduction. This pathophysiologic mechanism unifies the various individual inflammatory side effects recurrently reported with sirolimus suggesting that they should be considered as a single syndromic entity.

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.

Wound healing complications and the use of mammalian target of rapamycin inhibitors in kidney transplantation: a critical review of the literature

Surgical complications, including events such as lymphocele and urological complications that affect wound healing, are reported with an incidence of 15% to 32% after kidney transplantation. The experience of the surgeon and comorbidities play an important role in determining the risk of such complications occurring. Since the introduction of the inosine 5'-monophosphate dehydrogenase inhibitors (mycophenolate mofetil) to the immunosuppressive armamentarium, replacing the antimetabolite prodrug azathioprine, reports have associated certain forms of wound healing complications (wound dehiscence, impaired healing, lymphocele, and incisional hernia) with the use of these agents. When mammalian target of rapamycin (mTOR) inhibitors (sirolimus, everolimus) became available, these findings were observed increasingly, particularly in direct comparisons with inosine 5'-monophosphate dehydrogenase inhibitors. The purpose of this article was to review the reported incidence of wound healing complications from randomized clinical trials that investigated the use of sirolimus- and everolimus-based treatment regimens in de novo kidney transplantation and the information available from the U.S. Food and Drug Administration database. The clinical trials included were primarily identified using biomedical literature database searches, with additional studies added at the authors' discretion. This review summarizes these studies to consider whether modern mTOR inhibitor-based immunosuppressive regimens exert and affect wound healing after kidney transplantation.

Multicentric outcome analysis of sirolimus-based immunosuppression in 252 liver transplant recipients

SUMMARY

The use of sirolimus (SRL) in orthotopic liver transplantation (OLT) has been controversial after experimental data suggested an increased risk of hepatic artery thrombosis (HAT). To assess the safety and efficacy of SRL as de novo immunosuppression in OLT recipients. Outcomes of 252 OLT patients who received SRL were compared with outcomes of 291 OLT recipients who received calcineurin inhibitor in a retrospective study. Primary outcomes of this study were: patient- and graft survivals, vascular, biliary, wound complications and rejection rates. Secondary outcomes were: postoperative infection rate, bone marrow and renal function and changes of lipid levels. Patient- and graft survivals, rejection and infection rates were similar. In the SRL group, HAT occurred in 1.2%, biliary complications in 19.4%, and incisional hernias in 9.1%. In the control group the incidence of HAT was 5.8% (P = 0.004), biliary complications 18.5% (P = NS) and incisional hernias 7.2% (P = NS). Patients on SRL experienced significantly higher levels of serum triglycerides but fewer acute cellular rejections. Bone marrow and renal functions were similar in both the groups. Our findings would suggest that SRL is safe and effective for very selected OLT recipients. Randomized controlled trials are necessary to confirm our results.

Clinical islet transplantation in Japan

INTRODUCTION

The results of clinical islet transplantation in Japan are, here in, reported and discussed its efficacy and problems.

METHODS

Since the first islet transplantation was performed in 2004, 65 islet isolations and 34 islet transplantations to 18 type 1 diabetic patients have been performed in Japan.

RESULTS

Following islet transplantation, patients experienced decreased insulin requirements and lower hemoglobin A1C levels, and positive serum C-peptide levels. All patients achieved stabilized blood glucose levels and the disappearance of hypoglycemic unawareness. Although three patients achieved insulin independency for a limited period, persistent islet graft function was difficult to maintain. Overall islet graft survival was 86.5% at 6 months, 78.7% at 1 year, and 62.9% at 2 years after the first islet transplantation. In our institution, we carried out 23 islet isolations and six islet transplantations to four patients. Although insulin independency was not achieved, all patients showed a disappearance of hypoglycemic unawareness.

CONCLUSIONS

Using data from the Japanese Trial of Islet Transplantation, the effectiveness of islet transplantation was shown even when using the pancreata from non-heart-beating donors. Although there are a number of problems to be solved and further improvement is needed, we can state that the introduction of clinical islet transplantation offers hope for type 1 diabetic patients.

Current status of islet cell transplantation

Despite substantial advances in islet isolation methods and immunosuppressive protocol, pancreatic islet cell transplantation remains an experimental procedure currently limited to the most severe cases of type 1 diabetes mellitus. The objectives of this treatment are to prevent severe hypoglycemic episodes in patients with hypoglycemia unawareness and to achieve a more physiological metabolic control. Insulin independence and long term-graft function with improvement of quality of life have been obtained in several international islet transplant centers. However, experimental trials of islet transplantation clearly highlighted several obstacles that remain to be overcome before the procedure could be proposed to a much larger patient population. This review provides a brief historical perspective of islet transplantation, islet isolation techniques, the transplant procedure, immunosuppressive therapy, and outlines current challenges and future directions in clinical islet transplantation.

Rapamycin in islet transplantation: friend or foe?

The Edmonton protocol was undoubtedly a major step forward in the history of islet transplantation. Its immunosuppression regimen was largely based on the mTOR inhibitor rapamycin (sirolimus), which remains the most frequently used immunosuppressive drug in clinical islet transplant protocols. As time reveals the somewhat disappointing long-term results achieved with the Edmonton protocol, a number of publications have appeared addressing the potential beneficial or deleterious role of rapamycin on islet cell engraftment, function survival and regeneration, as well as on its side-effects in human subjects. This paper reviews the sometimes contradictory evidence on the impact of rapamycin in islet transplantation.

Belatacept and basiliximab diminish human antiporcine xenoreactivity and synergize to inhibit alloimmunity

BACKGROUND

Maintenance immunosuppression with calcineurin inhibitor therapy has improved survival rates in solid organ transplantation over the past decade. However, these drugs are associated with negative side effects, including nephrotoxicity and new-onset diabetes. Selective immunomodulatory agents such as belatacept and basiliximab have shown great promise in promoting allograft survival. In the present study, in vitro experiments were conducted to determine if these agents could synergize to inhibit immune responses.

METHODS

Porcine and human lymphocytes were incubated with each drug and analyzed using flow cytometry to measure binding capability. The inhibitory effects of each drug were evaluated using mixed lymphocyte reactions with drug doses comparable to the trough levels observed in treated human patients.

RESULTS

Our data demonstrates that belatacept and basiliximab bind to porcine peripheral blood mononuclear cells. Mixed lymphocyte reactions revealed that both belatacept and basiliximab monotherapy potently inhibited allogeneic immune responses and human antipig xenoreactivity. These data also demonstrate that combination of belatacept and basiliximab produces a synergistic inhibition of allogeneic immune responses.

CONCLUSIONS

These studies suggest that the combination of belatacept and basiliximab will potently inhibit alloreactivity in vivo when used as maintenance immunosuppression. We have further shown that belatacept and basiliximab are significantly reduce xenoreactivity of human lymphocytes in vitro.

Resolution of severe atopic dermatitis after tacrolimus withdrawal

Tacrolimus is an immunosuppressive agent used in solid organ and islet transplantation. Its topical form has shown benefit in the treatment of inflammatory skin conditions. Although tacrolimus has a wide spectrum of side effects, dermatological complications related to systemic tacrolimus therapy are limited in the literature. Atopic dermatitis (AD) is a chronic pruritic cutaneous condition that usually begins in infancy and is characterized by an increased Th2 response. We report the case of a patient with type 1 diabetes mellitus (T1DM) and history of AD latent for 10 years who developed severe dermatitis and alopecia 5 months after undergoing allogeneic islet transplantation and initiating a steroid-free immunosuppressive regimen with sirolimus and tacrolimus maintenance. After exclusion of other possible causes for the progression and exacerbation of the clinical presentation of AD, discontinuation of tacrolimus and introduction of mycophenolate mofetil resulted in full remission of the symptoms. The beneficial effects of tacrolimus withdrawal suggest a cause-effect relationship between this adverse event and the utilization of the drug. Islet graft function remained stable after modification of the therapeutic regimen (stable glycemic control and unchanged C-peptide).

Factors influencing the loss of beta-cell mass in islet transplantation

Recent advances in clinical islet transplantation have clearly demonstrated that this procedure can provide excellent glycemic control and often insulin independence in a population of patients with type 1 diabetes. A key limitation in the widespread application of clinical islet transplantation is the requirement of 10,000 islet equivalents/kg in most recipients, generally derived from two or more cadaveric donors. It has been determined that a majority of the transplanted islets fail to engraft and become fully functional. In this review article, the factors that contribute to this early loss of islets following transplantation are discussed in depth.

Overcoming the Challenges Now Limiting Islet Transplantation: A Sequential, Integrated Approach

Steady improvements in islet cell processing technology and immunosuppressive protocols have made pancreatic islet transplantation a clinical reality for the treatment of patients with Type 1 diabetes mellitus (T1DM). Recent trials are showing that improved glycemic metabolic control, prevention of severe hypoglycemia, and better quality of life can be reproducibly achieved after transplantation of allogeneic islets in patients with unstable T1DM. Despite these encouraging results, challenges ahead comprise obtaining adequate islet cells for transplant, enhancing islets engraftment, sustaining beta cell mass and function over time, and defining effective immune interventions, among others. In order to overcome the current hurdles to the widespread application of islet transplantation there is a need for implementation of integrated, sequential therapeutic approaches.