Cardiac transplant experience with cyclosporine

Preclinical Large Animal Porcine Models for Cardiac Regeneration and Its Clinical Translation: Role of hiPSC-Derived Cardiomyocytes

Myocardial Infarction (MI) occurs due to a blockage in the coronary artery resulting in ischemia and necrosis of cardiomyocytes in the left ventricular heart muscle. The dying cardiac tissue is replaced with fibrous scar tissue, causing a decrease in myocardial contractility and thus affecting the functional capacity of the myocardium. Treatments, such as stent placements, cardiac bypasses, or transplants are beneficial but with many limitations, and may decrease the overall life expectancy due to related complications. In recent years, with the advent of human induced pluripotent stem cells (hiPSCs), newer avenues using cell-based approaches for the treatment of MI have emerged as a potential for cardiac regeneration. While hiPSCs and their derived differentiated cells are promising candidates, their translatability for clinical applications has been hindered due to poor preclinical reproducibility. Various preclinical animal models for MI, ranging from mice to non-human primates, have been adopted in cardiovascular research to mimic MI in humans. Therefore, a comprehensive literature review was essential to elucidate the factors affecting the reproducibility and translatability of large animal models. In this review article, we have discussed different animal models available for studying stem-cell transplantation in cardiovascular applications, mainly focusing on the highly translatable porcine MI model.

Essentials in the diagnosis of postoperative myocardial lesions similar to or unrelated to rejection in heart transplant

Background, objectives: Histological diagnosis of control biopsies in patients with heart transplant represents a significant step of monitoring, with a great influence on adjusting immunosuppressive treatment. Histological lesions are usually related to ischemia and reperfusion, with varying degrees of intensity. This study aimed to highlight the most important aspects of the histological diagnosis and differential diagnosis of postoperative myocardial lesions associated or unrelated to rejection in heart transplant.

Materials and Methods: This retrospective study involved 53 patients who received cardiac transplant between 2000 and 2017. Patients were monitored by lesion quantification of endomyocardial biopsies, with diagnoses established based on biopsy material in the early, medium and late post-transplant periods. Hematoxylin eosin, Masson’s trichrome, and Van Gieson stains were used; immunohistochemical determinations used CD4, CD20, CD45, CD68, HLA-DR, VEGF and CD31.

Results: Ischemia and reperfusion lesions were diagnosed on all biopsies in the first 6 weeks post-transplant. Nine cases of the Quilty effect were identified, and in 12 cases, the biopsies were performed on the same spot as previous biopsies. A significant number of transplanted patients presented cytomegalovirus that was difficult to diagnose on endomyocardial biopsies.

Conclusions: The detailed study of ischemia and reperfusion lesions, as well as of changes un-related to rejection becomes a major objective in the short, medium and late post-transplant period. Overdiagnosis of rejection induces changes of the immunosuppressive therapeutic protocol, with alarming repercussions on cytomegalovirus reactivation, and risks of potentiating inflammation, myocyte destruction and the recurrence of disorders related to both inducing and aggravating heart failure.

Sodium Iodide Symporter PET and BLI Noninvasively Reveal Mesoangioblast Survival in Dystrophic Mice

Muscular dystrophies are a heterogeneous group of myopathies, characterized by muscle weakness and degeneration, without curative treatment. Mesoangioblasts (MABs) have been proposed as a potential regenerative therapy. To improve our understanding of the in vivo behavior of MABs and the effect of different immunosuppressive therapies, like cyclosporine A or co-stimulation-adhesion blockade therapy, on cell survival noninvasive cell monitoring is required. Therefore, cells were transduced with a lentiviral vector encoding firefly luciferase (Fluc) and the human sodium iodide transporter (hNIS) to allow cell monitoring via bioluminescence imaging (BLI) and small-animal positron emission tomography (PET). Non-H2 matched mMABs were injected in the femoral artery of dystrophic mice and were clearly visible via small-animal PET and BLI. Based on noninvasive imaging data, we were able to show that co-stim was clearly superior to CsA in reducing cell rejection and this was mediated via a reduction in cytotoxic T cells and upregulation of regulatory T cells.

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Longitudinal monitoring of murine mesoangioblasts with BLI and small-animal PET

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Noninvasive evaluation of immune suppressant efficacy

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Inhibition of co-stimulation outperformed cyclosporin

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Inhibition of co-stimulation reduced cytotoxic and upregulated regulatory T cells

Trends in the biosynthesis and production of the immunosuppressant tacrolimus (FK506)

The current off-patent state of tacrolimus (FK506) has opened the hunting season for new generic pharmaceutical formulations of this immunosuppressant. This fact has boosted the scientific and industrial research on tacrolimus for the last 5 years in order to improve its production. The fast discovery of tacrolimus producer strains has generated a huge number of producers, which presents the biosynthetic cluster of FK506 as a high promiscuous genetic region. For the first time, the current state-of-the-art on the tacrolimus biosynthesis, production improvements and drug purification is reviewed. On one hand, all the genes involved in the tacrolimus biosynthesis, in addition to the traditional PKS/NRPS, as well as their regulation are analysed. On the other hand, tacrolimus direct and indirect precursors are reviewed as a straight manner to improve the final yield, which is a current trend in the field. Twenty years of industrial and scientific improvements on tacrolimus production are summarised, whereas future trends are also drafted.

Costimulation-adhesion blockade is superior to cyclosporine A and prednisone immunosuppressive therapy for preventing rejection of differentiated human embryonic stem cells following transplantation

RATIONALE

Human embryonic stem cell (hESC) derivatives are attractive candidates for therapeutic use. The engraftment and survival of hESC derivatives as xenografts or allografts require effective immunosuppression to prevent immune cell infiltration and graft destruction.

OBJECTIVE

To test the hypothesis that a short-course, dual-agent regimen of two costimulation-adhesion blockade agents can induce better engraftment of hESC derivatives compared to current immunosuppressive agents.

METHODS AND RESULTS

We transduced hESCs with a double fusion reporter gene construct expressing firefly luciferase (Fluc) and enhanced green fluorescent protein, and differentiated these cells to endothelial cells (hESC-ECs). Reporter gene expression enabled longitudinal assessment of cell engraftment by bioluminescence imaging. Costimulation-adhesion therapy resulted in superior hESC-EC and mouse EC engraftment compared to cyclosporine therapy in a hind limb model. Costimulation-adhesion therapy also promoted robust hESC-EC and hESC-derived cardiomyocyte survival in an ischemic myocardial injury model. Improved hESC-EC engraftment had a cardioprotective effect after myocardial injury, as assessed by magnetic resonance imaging. Mechanistically, costimulation-adhesion therapy is associated with systemic and intragraft upregulation of T-cell immunoglobulin and mucin domain 3 (TIM3) and a reduced proinflammatory cytokine profile.

CONCLUSIONS

Costimulation-adhesion therapy is a superior alternative to current clinical immunosuppressive strategies for preventing the post-transplant rejection of hESC derivatives. By extending the window for cellular engraftment, costimulation-adhesion therapy enhances functional preservation following ischemic injury. This regimen may function through a TIM3-dependent mechanism.

Host-based Th2 cell therapy for prolongation of cardiac allograft viability

Donor T cell transfusion, which is a long-standing approach to prevent allograft rejection, operates indirectly by alteration of host T cell immunity. We therefore hypothesized that adoptive transfer of immune regulatory host Th2 cells would represent a novel intervention to enhance cardiac allograft survival. Using a well-described rat cardiac transplant model, we first developed a method for ex vivo manufacture of rat host-type Th2 cells in rapamycin, with subsequent injection of such Th2.R cells prior to class I and class II disparate cardiac allografting. Second, we determined whether Th2.R cell transfer polarized host immunity towards a Th2 phenotype. And third, we evaluated whether Th2.R cell therapy prolonged allograft viability when used alone or in combination with a short-course of cyclosporine (CSA) therapy. We found that host-type Th2.R cell therapy prior to cardiac allografting: (1) reduced the frequency of activated T cells in secondary lymphoid organs; (2) shifted post-transplant cytokines towards a Th2 phenotype; and (3) prolonged allograft viability when used in combination with short-course CSA therapy. These results provide further support for the rationale to use “direct” host T cell therapy for prolongation of allograft viability as an alternative to “indirect” therapy mediated by donor T cell infusion.

Trends in invasive disease due to Candida species following heart and lung transplantation

Although invasive candidiasis (IC) causes significant morbidity and mortality in patients who undergo heart, lung, or heart-lung transplantation, a systematic study in a large cohort of thoracic organ transplant recipients has not been reported to date. Clinical and microbiological data were reviewed for 1305 patients who underwent thoracic organ transplantation at Stanford University Medical Center between 1980 and 2004. We identified and analyzed 76 episodes of IC in 68 patients (overall incidence 5.2% per patient).The incidence of IC was higher in lung (LTx) and heart-lung transplant (HLTx) recipients as compared with heart transplant (HTx) recipients (risk ratio [RR] 1.7, 95% confidence interval [CI] 1.1-2.7).The incidence of IC decreased over time in all thoracic organ transplant recipients, decreasing from 6.1% in the 1980-1986 time period to 2.1% in the 2001-2004 era in the HTx recipients, and from 20% in the 1980-1986 period to 1.8% in the 2001-2004 period in the LTx and HLTx recipients.The most common site of infection differed between the HTx and LTx cohorts, with bloodstream or disseminated disease in the former and tracheobronchitis in the latter. IC in the first year after transplant was significantly associated with death in both HTx (RR 2.9, 95% CI 1.8-4.6, P=0.001) and LTx and HLTx patients (RR 3.0, 95% CI 1.9-4.6, P<0.001). The attributable mortality from IC decreased during the 25-year period of observation, from 36% to 20% in the HTx recipients and from 39% to 15% in the LTx and HLTx recipients. There were a significant number of cases caused by non-albicans Candida species in all patients, with a trend toward higher mortality in the HTx group. In conclusion, the incidence and attributable mortality of IC in thoracic organ transplant recipients has significantly declined over the past 25 years.The use of newer antifungal agents for prophylaxis and treatment, the decrease in the incidence of cytomegalovirus disease, and the use of more selective immunosuppression, among other factors, may have been responsible for this change.

Effect of various immunosuppressive monotherapies on survival and histopathology of monkey islet xenografts in rats

BACKGROUND

The isolation and testing of monkey islets after transplantation in small animal models provides basic information about their functional capacity. We describe the effect of cyclosporine A (CsA), tacrolimus (FK506) or prednisolone monotherapy on preventing monkey islet graft rejection after xenoTx in a rat model. Histopathological aspects are reported.

METHODS

Indian bonnet monkey (Macaca radiata radiata) islets were isolated by a simple stationary digestion technique using collagenase. The islets were purified with dextran density gradients and were transplanted under the renal capsule of normal or diabetic rats. The rats received a daily dose of CsA, or FK506, or prednisolone, and the grafts were removed at different intervals to determine islet survival. The effect of discontinuation of CsA on islet graft survival was also monitored. Histological examination of islets transplanted into normal or streptozotocin-induced diabetic rats was carried out. In diabetic rats, islet survival was determined by the graft's ability to achieve euglycemia.

RESULTS

Reversal of diabetes was achieved in all transplanted diabetic rats, demonstrating the efficacy of the isolated monkey islets. Histological examination indicated that monkey islets survived in the presence of continuous high-dose immunosuppressive monotherapy in rats. Various types of infiltrating cells were observed in the grafted area at varying times after transplantation, depending on the immunosuppressive treatment. After discontinuation of CsA, the grafts were protected for a short period.

CONCLUSIONS

This study provided evidence for monkey islet survival after transplantation into rats receiving immunosuppressive monotherapy. Basic information on infiltrating cell types may be important in the study of xenograft rejection.

Should we be doing routine biopsy after heart transplantation in a new era of anti-rejection?

PURPOSE OF REVIEW

The endomyocardial biopsy has defined the diagnosis of rejection in cardiac transplantation and has historically been a vital tool when rejection rates following transplantation were high. Surveillance biopsies have been the cornerstone of post-transplant management, as signs or symptoms of rejection are non-specific. With significant improvements in immunosuppressive therapy, however, the incidence of clinically significant rejection has declined, bringing into question the need for routine surveillance biopsy. This article reviews the current role of the endomyocardial biopsy in the management of patients following cardiac transplantation.

RECENT FINDINGS

The endomyocardial biopsy is also limited by sub-optimal interobserver reproducibility, a lack of consensus with regard to treating certain grades of rejection, and often a lack of histological findings in patients with hemodynamic compromise, which frequently responds to anti-rejection therapy. Recent refinements, however, have allowed improved diagnosis of antibody mediated rejection, a relatively recently recognized entity. Moreover, a number of non-invasive modalities have been investigated recently as potential substitutes for the endomyocardial biopsy in detecting rejection.

SUMMARY

Despite the development of a variety of non-invasive methods for the detection of rejection, the endomyocardial biopsy will remain important in the management of patients following cardiac transplantation, as non-invasive techniques are associated with low specificity for the diagnosis of rejection. A new standardized classification will likely improve the utility of the biopsy by simplifying interpretation of cellular rejection and importantly allowing recognition of antibody-mediated rejection.

Influence of cyclosporine on low-density lipoprotein uptake in human lymphocytes

Low-density lipoprotein (LDL) levels are often elevated in renal transplant recipients, and cyclosporine (CsA) therapy in these patients has been implicated. Cardiovascular disease is the major cause of mortality in transplant recipients, and alterations of lipid metabolism represent a common risk factor. The role of CsA on LDL metabolism is still partially defined. The aim of the study was to evaluate the LDL receptor uptake of CsA-transported LDL (CsA-LDL) compared with normal LDL in normal and CsA-treated lymphocytes. Forty-seven healthy unrelated subjects and 6 CsA-treated patients were consecutively enrolled as donors of lymphocytes to measure receptor-mediated LDL metabolism. Normal LDL and CsA-LDL were isolated from blood donors and from patients under CsA immunosuppressive therapy, respectively. Lipoproteins were labeled with a fluorochrome, and LDL receptor uptake was measured by flow cytometry. Normal LDL uptake was 13.95% +/- 4.5%, whereas CsA-LDL uptake was 32.47% +/- 10.84% (P < .001) in healthy lymphocytes. In CsA-treated lymphocytes, normal LDL uptake was 7.48% +/- 2.32% vs 12.49% +/- 2.44% CsA-LDL (P < .01). Lymphocytes of every subject showed at least a 2-fold increased uptake of CsA-LDL vs normal LDL. Our data show that CsA-LDL is internalized more than normal LDL via the LDL receptor in both human healthy and CsA-treated lymphocytes. CsA-treated lymphocytes, in comparison to normal lymphocytes, exhibit a reduced LDL receptor activity.

[Tacrolimus blood levels and incidence of graft rejection in heart transplantation]

OBJECTIVE

To determine the relationship between pharmacokinetic parameters and clinical outcomes after heart transplantation and to determine the range of tacrolimus blood levels which provides the most effective protection against graft rejection. To study other factors that predict graft rejection.

METHOD

We retrospectively analyzed the clinical outcomes of all adult patients who received a heart transplant between January 2000 and October 2003 and had routine monitoring of tacrolimus trough levels at the time of scheduled endomyocardial biopsy. Rejection was defined as Grade = 3, based on the International Society for Heart and Lung Transplantation (ISHLT) criteria. The follow-up period was 1 year. All patients were on a triple therapy regimen of Tacrolimus (TAC), Corticosteroids and Azatioprine/Micophenolate Mofetil. Data were analyzed by Student s t-test, univariate logistic regression and ROC curve.

RESULTS

Tacrolimus blood levels measured at day +5 postransplant were the strongest predictor of acute graft rejection over a 1-year follow-up period (rejection 5.76 +/- 3.4 ng/ml vs no rejection 9.66 +/- 2.73 ng/ml, p = 0.016). A decrease of one unit in TAC trough level values at day +5 postransplant implied a 1.58 greater risk of rejection (p = 0.05). Overall incidence of treated acute rejection was lower for patients with trough levels higher than 8 ng/ml on day +5 postransplant (33 vs 80%, p = 0.055, Fisher s exact test).

CONCLUSIONS

Data suggest that in heart transplant patients it may be crucial to achieve tacrolimus levels of at least 8 ng/ml during the first days postsurgery to avoid rejection.

Impact of Cardiac Transplantation in 24 Hours Circadian Blood Pressure and Heart Rate Profile

OBJECTIVE

The aim of the present study was to evaluate 24 hours blood pressure (BP) and heart rate changes as well as 24-hour circadian BP rhythm of cardiac transplant recipients.

METHODS

Twenty-five transplant recipients and twenty-five healthy volunteers underwent 24-hour ambulatory BP monitoring. Parameters of 24-hour ambulatory BP monitoring (24-h/daytime/nightime systolic, diastolic BP, pulse pressure, and heart rate) were determined in all patients.

RESULTS

Clinic systolic/diastolic BP, mean 24-h systolic/diastolic BP, mean daytime systolic/diastolic BP, mean nighttime systolic/diastolic BP, and mean 24-h/daytime/nighttime heart rate were significantly higher in transplant recipients than in control group subjects. Standard deviations of 24-h/daytime/nighttime heart rates were significantly lower in transplant recipients. Dippers were 48% of the control and only 12% of the transplantation group.

CONCLUSIONS

Cardiac transplant recipients had increased ambulatory BP. They also had increased 24-h/daytime/nighttime heart rate and decreased heart rate variability. Also, diminished nocturnal decrease of BP was found in transplant recipients.