Effects of Mycophenolate Mofetil on Cardiac Allograft Survival and Cardiac Allograft Vasculopathy in Miniature Swine

The pig as an optimal animal model for cardiovascular research

Cardiovascular disease is a worldwide health problem and a leading cause of morbidity and mortality. Preclinical cardiovascular research using animals is needed to explore potential targets and therapeutic options. Compared with rodents, pigs have many advantages, with their anatomy, physiology, metabolism and immune system being more similar to humans. Here we present an overview of the available pig models for cardiovascular diseases, discuss their advantages over other models and propose the concept of standardized models to improve translation to the clinical setting and control research costs.

Current Status Regarding Immunosuppressive Treatment in Patients after Renal Transplantation

Renal transplantation is now the best treatment for end-stage renal failure. To avoid rejection and prolong graft function, organ recipients need immunosuppressive therapy. The immunosuppressive drugs used depends on many factors, including time since transplantation (induction or maintenance), aetiology of the disease, and/or condition of the graft. Immunosuppressive treatment needs to be personalised, and hospitals and clinics have differing protocols and preparations depending on experience. Renal transplant recipient maintenance treatment is mostly based on triple-drug therapy containing calcineurin inhibitors, corticosteroids, and antiproliferative drugs. In addition to the desired effect, the use of immunosuppressive drugs carries risks of certain side effects. Therefore, new immunosuppressive drugs and immunosuppressive protocols are being sought that exert fewer side effects, which could maximise efficacy and reduce toxicity and, in this way, reduce both morbidity and mortality, as well as increase opportunities to modify individual immunosuppression for renal recipients of all ages. The aim of the current review is to describe the classes of immunosuppressive drugs and their mode of action, which are divided by induction and maintenance treatment. An additional aspect of the current review is a description of immune system activity modulation by the drugs used in renal transplant recipients. Complications associated with the use of immunosuppressive drugs and other immunosuppressive treatment options used in kidney transplant recipients have also been described.

Large animal models for cardiac remuscularization studies: A methodological review

Myocardial infarction is the most common cause of heart failure, one of the most fatal non-communicable diseases worldwide. The disease could potentially be treated if the dead, ischemic heart tissues are regenerated and replaced with viable and functional cardiomyocytes. Pluripotent stem cells have proven the ability to derive specific and functional cardiomyocytes in large quantities for therapy. To test the remuscularization hypothesis, the strategy to model the disease in animals must resemble the pathophysiological conditions of myocardial infarction as in humans, to enable thorough testing of the safety and efficacy of the cardiomyocyte therapy before embarking on human trials. Rigorous experiments and in vivo findings using large mammals are increasingly important to simulate clinical reality and increase translatability into clinical practice. Hence, this review focus on large animal models which have been used in cardiac remuscularization studies using cardiomyocytes derived from human pluripotent stem cells. The commonly used methodologies in developing the myocardial infarction model, the choice of animal species, the pre-operative antiarrhythmics prophylaxis, the choice of perioperative sedative, anaesthesia and analgesia, the immunosuppressive strategies in allowing xenotransplantation, the source of cells, number and delivery method are discussed.

Subcutaneous transplantation of engineered islet/adipose-derived mesenchymal stem cell sheets in diabetic pigs with total pancreatectomy

Introduction

Intraportal islet transplantation is a promising therapeutic approach for patients with type 1 diabetes mellitus (T1DM). However, despite being minimally invasive, the method has some limitations, such as short-term graft loss, portal venous thrombosis, and difficulty in collecting adequate amounts of islets. Subcutaneous islet transplantation on adipose-derived mesenchymal stem cell (ADSC) sheets has been suggested to overcome these limitations, and in this study, we have examined its feasibility in T1DM pigs.

Methods

Inguinal subcutaneous fat was harvested from young pigs and then isolated and cultured adequate ADSCs to prepare sheets. Islets were isolated from the pancreases of mature pigs and seeded on the ADSC sheets. T1DM pigs were generated by total pancreatectomy, and ADSC sheets with transplanted islets were administered subcutaneously to the waist (n = 2). The effects of the islets on the ADSC sheets and on blood glucose levels were evaluated. Insulin secretion was measured by insulin stimulation index.

Results

Islet viability was higher on ADSCs compared to islets alone (91.8 ± 4.3 vs. 81.7 ± 4.1%). The insulin stimulation index revealed higher glucose sensitivity of islets on ADSC sheets compared to islets alone (2.8 ± 2.0 vs. 0.8 ± 0.3). After transplantation, the blood glucose levels of two pigs were within the normal range, and sensitive insulin secretion was confirmed by intravenous glucose tolerance tests. After graftectomy, decreased insulin secretion and hyperglycemia were observed.

Conclusions

Subcutaneous islet transplantation using ADSC sheets can regulate the blood glucose levels of T1DM pigs.

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The adipose-derived mesenchymal stem cell sheet is useful to protect the islets.

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Subcutaneous islet transplantation on sheet normalized blood glucose in diabetic pig.

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Subcutaneous islet transplantation on sheet can be a useful tool.

CXCR4 Antagonist Reduced the Incidence of Acute Rejection and Controlled Cardiac Allograft Vasculopathy in a Swine Heart Transplant Model Receiving a Mycophenolate-based Immunosuppressive Regimen

BACKGROUND

CXC motif chemokine receptor 4 (CXCR4) blockade is pursued as an alternative to mesenchymal stem cell treatment in transplantation based on our previous report that burixafor, through CXCR4 antagonism, mobilizes immunomodulatory mesenchymal stem cells. Here, we explored the efficacy of combining mycophenolate mofetil (MMF)-based immunosuppressants with repetitive burixafor administration.

METHODS

Swine heterotopic cardiac allograft recipients received MMF and corticosteroids (control, n = 10) combined with burixafor as a 2-dose (burixafor2D, n = 7) or 2-dose plus booster injections (burixafor2D + B, n = 5) regimen. The efficacy endpoints were graft survival, freedom from first acute rejection, and the severity of intimal hyperplasia. Each specimen was sacrificed either at its first graft arrest or after 150 days.

RESULTS

After 150 days, all specimens in the control group had died, but 28.5% of the burixafor2D group survived, and 60% of the burixafor2D + B group survived (P = 0.0088). Although the control group demonstrated acute rejection at a median of 33.5 days, the burixafor2D + B group survived without acute rejection for a median of 136 days (P = 0.0209). Burixafor administration significantly attenuated the incidence rate of acute rejection (P = 0.002) and the severity of intimal hyperplasia (P = 0.0097) at end point relative to the controls. These findings were associated with reduced cell infiltrates in the allografts, and modulation of C-reactive protein profiles in the circulation.

CONCLUSIONS

The augmentation of conventional MMF plus corticosteroids with a CXCR4 antagonist is potentially effective in improving outcomes after heart transplantation in minipigs. Future studies are warranted into optimizing the therapeutic regimens for humans.

Cordyceps sinensis extracts attenuate aortic transplant arteriosclerosis in rats

BACKGROUND

Transplant arteriosclerosis is a hallmark of chronic rejection and is still the major limiting factor affecting the success of long-term organ transplants. Development of transplant arteriosclerosis is refractory to conventional immunosuppressive drugs, and adequate therapy is not yet available. The aim of this study was to determine the role of Cordyceps sinensis extracts in reducing the formation of transplant arteriosclerosis in a rat aortic transplant model.

METHODS

Lewis rat aortic allografts were transplanted into Brown-Norway recipient rats. Recipients received 0.5, 1, 2, and 5 mg/kg of Cordyceps sinensis extracts (or control saline) daily via intragastric injection for 60 d. Grafts were harvested 60 d post-transplantation and intimal thickness determined microscopically following hematoxylin and eosin (H and E) staining and abdominal aorta protein profiles determined by Western blot analysis. Cellular localization was assessed by histology and immunohistochemistry and the serum analyzed for tumor necrosis factor alpha (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) by enzyme-linked immunosorbent assay (ELISA).

RESULTS

C. sinensis administration resulted in a significant reduction in neointimal formation (neointimal thickness 8.27 ± 1.95 μm [0.5 mg/kg], 3.69 ± 1.43 μm [1 mg/kg], 3.69 ± 1.43 μm [1 mg/kg], 3.69 ± 1.43 μm [1 mg/kg] versus 11.42 ± 2.67 μm [control]) and in the proliferative activity of vascular smooth muscle cells. In addition, localized expression of TNF-α and ICAM-1 in transplant aortas was characterized by immunohistochemistry and immunoblot analyses demonstrating that C. sinensis treatment significantly reduced TNF-α and ICAM-1 levels compared with levels observed in controls (P < 0.05). Serum TNF-α and ICAM-1 levels were significantly reduced in C. sinensis-treated animals compared with controls (P < 0.05).

CONCLUSION

C. sinensis treatment effectively reduced the formation of transplant arteriosclerosis in a rat aortic transplant model.

Contribution of B cells and antibody to cardiac allograft vasculopathy

BACKGROUND

The aim of this study was to determine the role of alloantibody in the development of cardiac allograft vasculopathy (AV). AV is the main pathologic indicator of chronic cardiac graft rejection resulting in graft loss at 10 years posttransplant. In AV, a neointimal lesion forms resulting in luminal occlusion and damage to the transplanted organ. AV is T-cell mediated, but the role played by B cells and antibody in AV development has been controversial. No studies have been conducted in the presence of a clinically relevant immunosuppressant. In our study, we use cyclosporin A, a calcineurin inhibitor.

METHODS

Two models of B-cell deficiency were used as recipients of a C3H/HeJ abdominal aortic graft; grafts were harvested at 8 weeks. T- and B-cell immunodeficient mice (RAG1-/-) received passively transferred anti-C3H antibody, raised in B6 mice. Cyclosporin A was administered daily to both control and experimental groups. Alpha-actin staining was used to identify myofibroblasts in the neointima.

RESULTS

Lesions in B-cell-deficient B6 mice were not significantly different in size from those of control mice. Lesions in both B-cell-deficient and wild-type mice showed similar levels of alpha-actin positivity. Passive transfer of antibody to RAG1-/- mice resulted in small, alpha-actin-positive lesions.

CONCLUSIONS

B cells are not required for the development of AV, but the presence of an alloantibody can contribute to AV. We hypothesize that the alloantibody mediates AV by initiating complement-mediated killing of smooth muscle cells, based on an in vitro work. Of interest, we found that the neointimal lesions of B-cell-deficient mice and mice that received antibody showed the presence of alpha-actin in myofibroblasts.

Conversion to sirolimus as primary immunosuppression attenuates the progression of allograft vasculopathy after cardiac transplantation

BACKGROUND

We investigated the potential of conversion to sirolimus (SRL) as a primary immunosuppressant in attenuating cardiac allograft vasculopathy progression.

METHODS AND RESULTS

Twenty-nine cardiac transplant recipients were converted to SRL 3.8+/-3.4 years after transplantation with complete calcineurin inhibitor (CNI) withdrawal. Secondary immunosuppressants (azathioprine or mycophenolate) and steroids remained unchanged. Forty patients (controls) 4.8+/-4.0 years from transplantation were maintained on CNIs. Three-dimensional intravascular ultrasound studies were performed at baseline and 12.1+/-2.6 months later. Mean plaque (media and intima) volume (PV) and plaque index (PI) (PV/vessel volume percent) increased significantly in the CNI group (1.28+/-2.86 mm(3)/mm, P=0.004; and 6+/-8%, P=0.0001) but not in the SRL group (0.1+/-1.13 mm(3)/mm, P=0.63; and 0.1+/-8%, P=0.94). In patients enrolled within 2 years after transplantation, the increases in PV (0.06+/-1.06 versus 1.77+/-1.65 mm(3)/mm; P=0.0081) and PI (0+/-9% versus 10+/-8%; P=0.0145) were smaller in the SRL group (n=11) than in the CNI (n=12) group. In patients enrolled >/=2 years after transplantation, the increase in PI was less in the SRL group compared with the CNI group (0.1+/-6.5% versus 5+/-8%; P=0.033), but changes in PV did not differ significantly. Treatment with azathioprine or mycophenolate did not affect PV or PI in either the SRL group (PV: 0.22+/-0.66 versus 0.05+/-1.45 mm(3)/mm, P=0.46; PI: 1.5+/-6% versus -1.6+/-8.5%, P=0.29) or the CNI group (PV: 1.42+/-1.39 versus 1.06+/-2.28 mm(3)/mm, P=0.49; PI: 7.8+/-8.7% versus 4.8+/-7.3%, P=0.23).

CONCLUSIONS

Substituting CNI with SRL as primary immunosuppression attenuates cardiac allograft vasculopathy progression.

Mycophenolate Mofetil and Atherosclerosis: Results of Animal and Human Studies

The immunosuppressive agent mycophenolate mofetil (MMF) has beneficial effects in cardiac transplant patients beyond the suppression of tissue rejection. Patients with regimens containing MMF experience diminished intimal thickening and cardiac allograft vasculopathy compared to patients treated with azathioprine. Studies have shown that diet-induced atherosclerosis (a related vasculopathy) is a chronic inflammatory process, and so MMF has also been used to reduce atherosclerosis in a rabbit model of hyperlipidemia. These data hold out the intriguing possibility that MMF might be a viable primary or secondary preventive agent in people at significant risk for atherosclerosis.