Recent Advances in Mammalian Target of Rapamycin Inhibitor Use in Heart and Lung Transplantation

Long-term outcomes in rapamycin on renal allograft function: a 30-year follow-up from a single-center experience

OBJECTIVES

To evaluate long-term renal graft prognosis and the role of rapamycin from a single-center in China over a 30-year follow-up.

METHODS

This study enrolled a total of 654 patients who underwent kidney transplantation between 1989 and 2020. The basic characteristics of the included patients were collected. Graft survival was described and compared using Kaplan-Meier curves (K-M curves). Both continuous and categorical variables were included in a multivariate Cox proportional-hazards model. Patients were divided into rapamycin-based quadruple immunosuppression regimen group (rapa group, n = 41) and conventional tacrolimus-based triple immunosuppression regimen group (control group, n = 218). The indication biopsy results of the two groups were further reviewed to compare the incidence of rejection, acute rejection, and banff score.

RESULTS

The overall 5, 10, 15, 20-year graft survival rate of our center is 87.5%, 62.4%, 46.4% and 20.9%, respectively. The median survival time after surgery is 14 years. Multiple Cox regression analysis identified BMI (p = 0.035), dialysis type (p < 0.001), immunosuppressants (p < 0.01), urine albumen (p < 0.001), globulin (p = 0.041), and blood glucose (p = 0.002) as risk factors. The 20-year, 10-year and 5-year AUC is 0.78, 0.75 and 0.75. The combination of FK506 and rapamycin was further suggested by the model to effectively improve the graft prognosis (p < 0.01, HR = 0.763). The K-M curve showed that the long-term survival rate of renal grafts in the rapa group was significantly better than that in the conventional group (p < 0.001). In addition, indication biopsy records revealed a lower possibility of immune rejection in the rapa group than that in the conventional group (p < 0.001). Banff score indicated that rapa group had less vascular inflammation in the transplanted kidney.

CONCLUSIONS

In this study, a 30-year follow-up was performed in a single center, and a total graft 20-year survival rate of 20.9% was reported. The prognostic model and subgroup analysis suggested that FK506 combined with rapamycin could effectively improve the prognosis of renal transplantation, which could be explained by reduced acute rejection and less vascular inflammation.

Reactive Oxygen Species Responsive Multifunctional Fusion Extracellular Nanovesicles: Prospective Treatments for Acute Heart Transplant Rejection

Heart transplantation offers life-saving treatment for patients with end-stage heart failure; however, ischemia-reperfusion injury (IRI) and subsequent immune responses remain significant challenges. Current therapies primarily target adaptive immunity, with limited options available for addressing IRI and innate immune activation. Although plant-derived vesicle-like nanoparticles show promise in managing diseases, their application in organ transplantation complications is unexplored. Here, this work develops a novel reactive oxygen species (ROS)-responsive multifunctional fusion extracellular nanovesicles carrying rapamycin (FNVs@RAPA) to address early IRI and Ly6C+Ly6G- inflammatory macrophage-mediated rejection in heart transplantation. The FNVs comprise Exocarpium Citri grandis-derived extracellular nanovesicles with anti-inflammatory and antioxidant properties, and mesenchymal stem cell membrane-derived nanovesicles expressing calreticulin with macrophage-targeting ability. A novel ROS-responsive bio-orthogonal chemistry approach facilitates the active targeting delivery of FNVs@RAPA to the heart graft site, effectively alleviating IRI and promoting the polarization of Ly6C+Ly6G- inflammatory macrophages toward an anti-inflammatory phenotype. Hence, FNVs@RAPA represents a promising therapeutic approach for mitigating early transplantation complications and immune rejection. The fusion-targeted delivery strategy offers superior heart graft site enrichment and macrophage-specific targeting, promising improved transplant outcomes.

Everolimus Treatment for Chronic Lung Allograft Dysfunction in Lung Transplantation

Our study aims to evaluate the effect of everolimus treatment on lung function in lung transplant (LT) patients with established chronic lung allograft dysfunction (CLAD).

METHODS

This retrospective study included LT patients in two reference LT units who started everolimus therapy to treat CLAD from October 2008 to October 2016. We assessed the variation in the maximum forced expiratory volume in the first second (FEV1) before and after the treatment.

RESULTS

Fifty-seven patients were included in this study. The variation in the FEV1 was -102.7 (149.6) mL/month before starting everolimus compared to -44.7 (109.6) mL/month within the first three months, +1.4 (63.5) mL/month until the sixth month, and -7.4 (46.2) mL/month until the twelfth month (p < 0.05). Glomerular filtrate remained unchanged after everolimus treatment [59.1 (17.5) mL/min per 1.73 m2 at baseline and 60.9 (19.6) mL/min per 1.73 m2, 57.7 (20.5) mL/min per 1.73 m2, and 57.3 (17.8) mL/min per 1.73 m2, at 1, 3, and 6 months, respectively] (p > 0.05). Everolimus was withdrawn in 22 (38.6%) patients. The median time to withdrawal was 14.1 (5.5-25.1) months.

CONCLUSIONS

This study showed an improvement in FEV1 decline in patients with CLAD treated with everolimus. However, the drug was withdrawn in a high proportion of patients.

Impact of Everolimus Initiation and Corticosteroid Weaning During Acute Phase After Heart Transplantation on Clinical Outcome: Data from the Korean Organ Transplant Registry (KOTRY)

The effect of changes in immunosuppressive therapy during the acute phase post-heart transplantation (HTx) on clinical outcomes remains unclear. This study aimed to investigate the effects of changes in immunosuppressive therapy by corticosteroid (CS) weaning and everolimus (EVR) initiation during the first year post-HTx on clinical outcomes. We analyzed 622 recipients registered in the Korean Organ Transplant Registry (KOTRY) between January 2014 and December 2021. The median age at HTx was 56 years (interquartile range [IQR], 45-62), and the median follow-up time was 3.9 years (IQR 2.0-5.1). The early EVR initiation within the first year post-HTx and maintenance during the follow-up is associated with reduced the risk of primary composite outcome (all-cause mortality or re-transplantation) (HR, 0.24; 95% CI 0.09-0.68; p < 0.001) and cardiac allograft vasculopathy (CAV) (HR, 0.39; 95% CI 0.19-0.79; p = 0.009) compared with EVR-free or EVR intermittent treatment regimen, regardless of CS weaning. However, the early EVR initiation tends to increase the risk of acute allograft rejection compared with EVR-free or EVR intermittent treatment.

Case report: Severe asymptomatic hypertriglyceridemia associated with long-term low-dose rapamycin administration in a healthy middle-aged Labrador retriever

Rapamycin is an mTOR inhibitor that has been shown to extend the lifespan of laboratory model organisms. In humans, rapamycin is used at higher doses as an immunosuppressive medication to prevent organ rejection. Numerous adverse effects are seen with rapamycin treatment in humans, with one of the most common being dysregulation of lipid metabolism. In humans, this often manifests as mild to moderate serum lipid elevations, with a small subset developing extreme triglyceride elevations. This case report describes an eight-year-old, castrated male, clinically healthy Labrador retriever who developed severe hypertriglyceridemia associated with low-dose rapamycin administration over a six-month period. During this time, the dog was asymptomatic and displayed no other clinical abnormalities, aside from a progressive lipemia. Within 15 days of discontinuing rapamycin treatment, and with no targeted lipemic intervention, the dog's lipemia and hypertriglyceridemia completely resolved.

Lymphocyte Depleting and Modulating Therapies for Chronic Lung Allograft Dysfunction

Chronic lung rejection, also called chronic lung allograft dysfunction (CLAD), remains the major hurdle limiting long-term survival after lung transplantation, and limited therapeutic options are available to slow the progressive decline in lung function. Most interventions are only temporarily effective in stabilizing the loss of or modestly improving lung function, with disease progression resuming over time in the majority of patients. Therefore, identification of effective treatments that prevent the onset or halt progression of CLAD is urgently needed. As a key effector cell in its pathophysiology, lymphocytes have been considered a therapeutic target in CLAD. The aim of this review is to evaluate the use and efficacy of lymphocyte depleting and immunomodulating therapies in progressive CLAD beyond usual maintenance immunosuppressive strategies. Modalities used include anti-thymocyte globulin, alemtuzumab, methotrexate, cyclophosphamide, total lymphoid irradiation, and extracorporeal photopheresis, and to explore possible future strategies. When considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin and total lymphoid irradiation appear to offer the best treatment options currently available for progressive CLAD patients. SIGNIFICANCE STATEMENT: Effective treatments to prevent the onset and progression of chronic lung rejection after lung transplantation are still a major shortcoming. Based on existing data to date, considering both efficacy and risk of side effects, extracorporeal photopheresis, anti-thymocyte globulin, and total lymphoid irradiation are currently the most viable second-line treatment options. However, it is important to note that interpretation of most results is hampered by the lack of randomized controlled trials.

Molecular and therapeutic insights of rapamycin: a multi-faceted drug from Streptomyces hygroscopicus

The advancement in pharmaceutical research has led to the discovery and development of new combinatorial life-saving drugs. Rapamycin is a macrolide compound produced from Streptomyces hygroscopicus. Rapamycin and its derivatives are one of the promising sources of drug with broad spectrum applications in the medical field. In recent times, rapamycin has gained significant attention as of its activity against cytokine storm in COVID-19 patients. Rapamycin and its derivatives have more potency when compared to other prevailing drugs. Initially, it has been used exclusively as an anti-fungal drug. Currently rapamycin has been widely used as an immunosuppressant. Rapamycin is a multifaceted drug; it has anti-cancer, anti-viral and anti-aging potentials. Rapamycin has its specific action on mTOR signaling pathway. mTOR has been identified as a key regulator of different pathways. There will be an increased demand for rapamycin, because it has lesser adverse effects when compared to steroids. Currently researchers are focused on the production of effective rapamycin derivatives to combat the growing demand of this wonder drug. The main focus of the current review is to explore the origin, development, molecular mechanistic action, and the current therapeutic aspects of rapamycin. Also, this review article revealed the potential of rapamycin and the progress of rapamycin research. This helps in understanding the exact potency of the drug and could facilitate further studies that could fill in the existing knowledge gaps. The study also gathers significant data pertaining to the gene clusters and biosynthetic pathways involved in the synthesis and production of this multi-faceted drug. In addition, an insight into the mechanism of action of the drug and important derivatives of rapamycin has been expounded. The fillings of the current review, aids in understanding the underlying molecular mechanism, strain improvement, optimization and production of rapamycin derivatives.

Everolimus Based Immunosuppression Strategies in Adult Lung Transplant Recipients: Calcineurin Inhibitor Minimization Versus Calcineurin Inhibitor Elimination

Everolimus (EVE) provides an alternative to maintenance immunosuppression when conventional immunosuppression cannot be tolerated. EVE can be utilized with a calcineurin inhibitor (CNI) minimization or elimination strategy. To date, clinical studies investigating EVE after lung transplant (LTx) have primarily focused on the minimization strategy to preserve renal function. The primary aim was to determine the preferred method of EVE utilization for lung transplant recipients (LTR). To undertake this aim, we compared the safety and efficacy outcomes of EVE as part of minimization and elimination immunosuppressant regimens. Single center retrospective study of 217 LTR initiated on EVE (120 CNI minimization and 97 CNI elimination). Survival outcomes were calculated from the date of EVE commencement. On multivariate analysis, LTR who received EVE as part of the CNI elimination strategy had poorer survival outcomes compared to the CNI minimization strategy [HR 1.61, 95% CI: 1.11-2.32, p=0.010]. Utilization of EVE for renal preservation was associated with improved survival compared to other indications [HR 0.64, 95% CI: 0.42-0.97, p=0.032]. EVE can be successfully utilized for maintenance immunosuppression post LTx, particularly for renal preservation. However, immunosuppressive regimens containing low dose CNI had superior survival outcomes, highlighting the importance of retaining a CNI wherever possible.

Mammalian Target of Rapamycin Inhibitors and Kidney Function After Thoracic Transplantation: A Systematic Review and Recommendations for Management of Lung Transplant Recipients

BACKGROUND

Chronic kidney disease (CKD) after lung transplantation is common and limits the survival of transplant recipients. The calcineurin inhibitors (CNI), cyclosporine A, and tacrolimus being the cornerstone of immunosuppression are key mediators of nephrotoxicity. The mammalian target of rapamycin (mTOR) inhibitors, sirolimus and everolimus, are increasingly used in combination with reduced CNI dosage after lung transplantation.

METHODS

This systematic review examined the efficacy and safety of mTOR inhibitors after lung transplantation and explored their effect on kidney function.

RESULTS

mTOR inhibitors are often introduced to preserve kidney function. Several clinical trials have demonstrated improved kidney function and efficacy of mTOR inhibitors. The potential for kidney function improvement and preservation increases with early initiation of mTOR inhibitors and low target levels for both mTOR inhibitors and CNI. No defined stage of CKD for mTOR inhibitor initiation exists, nor does severe CKD preclude the improvement of kidney function under mTOR inhibitors. Baseline proteinuria may negatively predict the preservation and improvement of kidney function. Discontinuation rates of mTOR inhibitors due to adverse effects increase with higher target levels.

CONCLUSIONS

More evidence is needed to define the optimal immunosuppressive regimen incorporating mTOR inhibitors after lung transplantation. Not only the indication criteria for the introduction of mTOR inhibitors are needed, but also the best timing, target levels, and possibly discontinuation criteria must be defined more clearly. Current evidence supports the notion of nephroprotective potential under certain conditions.

Protocadherin gamma C3: a new player in regulating vascular barrier function

Defects in the endothelial cell barrier accompany diverse malfunctions of the central nervous system such as neurodegenerative diseases, stroke, traumatic brain injury, and systemic diseases such as sepsis, viral and bacterial infections, and cancer. Compromised endothelial sealing leads to leaking blood vessels, followed by vasogenic edema. Brain edema as the most common complication caused by stroke and traumatic brain injury is the leading cause of death. Brain microvascular endothelial cells, together with astrocytes, pericytes, microglia, and neurons form a selective barrier, the so-called blood-brain barrier, which regulates the movement of molecules inside and outside of the brain. Mechanisms that regulate blood-brain barrier permeability in health and disease are complex and not fully understood. Several newly discovered molecules that are involved in the regulation of cellular processes in brain microvascular endothelial cells have been described in the literature in recent years. One of these molecules that are highly expressed in brain microvascular endothelial cells is protocadherin gamma C3. In this review, we discuss recent evidence that protocadherin gamma C3 is a newly identified key player involved in the regulation of vascular barrier function.

Current perspective of immunomodulators for lung transplant

Lung transplantation is an effective treatment option for selected patients suffering from end-stage lung disease. More intensive immunosuppression is enforced after lung transplants owing to a greater risk of rejection than after any other solid organ transplants. The commencing of lung transplantation in the modern era was in 1983 when the Toronto Lung Transplant Group executed the first successful lung transplant. A total of 43,785 lung transplants and 1365 heart-lung transplants have been performed from 1 Jan 1988 until 31 Jan 2021. The aim of this review article is to discuss the existing immunosuppressive strategies and emerging agents to prevent acute and chronic rejection in lung transplantation.

BEZ235 Prolongs Murine Cardiac Allograft Survival Through the Autophagy Pathway

BACKGROUND

BEZ235, a dual PI3K/mTOR inhibitor, has shown a critical impact in the treatment of cancers, with the ability to induce autophagy. However, the effects of BEZ235 in heart transplant have been rarely investigated. The aim of this study was to evaluate the potency of BEZ235 in cardiac allograft survival.

METHODS

BEZ235 was administered during the perioperative period of syngeneic or allogeneic heart transplant to assess survival time. Next, the autophagy signaling pathway and the proinflammatory cytokines were analyzed. Furthermore, a cardiomyocytes-specific ATG5 gene-ablated mouse was used to confirm the results.

RESULTS

BEZ235 treatment significantly prolonged the survival of the cardiac graft and reduced the infiltration of inflammatory cells. The expression levels of autophagy proteins were increased in the BEZ235 treatment group compared to the control group, but the therapeutic effect of BEZ235 was weakened in the cardiomyocytes-specific ATG5 gene-ablated mice. Moreover, BEZ235 significantly downregulated the expression of IL-1β, IL-2, and TNF-α.

CONCLUSIONS

It seems BEZ235 could induce autophagy and prolonged murine cardiac allograft survival in a mechanism that involved the autophagy pathway and changed multiple inflammatory factors. This study has proposed a theoretical foundation for the strong connection between mTOR-induced autophagy and heart transplant.

Viral-specific cytotoxic T-cell responses in HLA-sensitized kidney transplant patients maintained on everolimus and low dose tacrolimus

BACKGROUND

Maintenance with "everolimus + reduced dose tacrolimus" (Ev + Tac_low ) was reported to reduce the risk of viral infections compared to (Tac + MMF). Here we examined viremia and viral-specific T-cell (viral-Tc) responses in patients treated with Ev + Tac_low v. Tac + MMF in highly-HLA sensitized patients.

METHODS

HLA sensitized (HS) kidney transplant patients were monitored pre- and post-transplant for viremia (CMV, BK and EBV) by PCR in 19 Ev + Tac_low and 48 Tac + MMF patients. For CMV PCR analysis, we compared infection rates in 19 Ev + Tac_low patients to 48 CMV D+/R- (#28) or CMV D-/R- (#20) Tac + MMF patients. CMV-Tc and EBV-Tc were evaluated by cytokine flow cytometry, and DSA levels by Luminex for selected patients in both groups.

RESULTS

CMV, EBV viremia rates were similar in Ev + Tac_low v. Tac + MMF patients, but BKV rates were significantly higher in Ev + Tac_low patients. No patient in either group developed BKAN or PTLD. CMV- & EBV-Tc decreased significantly after alemtuzumab induction but returned to pre-treatment levels 1-2 months post-transplant in most patients. de novo DSA was similar in both groups as were patient and graft survival and graft rejection.

CONCLUSIONS

CMV-Tc, EBV-Tc were similar in Ev + Tac_low and Tac + MMF patients. EBV and CMV viremia rates were similar over 1 year. BKV rates were significantly higher in Ev + Tac_low patients suggesting no benefit for Ev + Tac_low in enhancing viral specific Tc effector functions or limiting viral infections. This article is protected by copyright. All rights reserved.

Sirolimus-Based Immunosuppression Is Associated with Decreased Incidence of Post-Transplant Lymphoproliferative Disorder after Heart Transplantation: A Double-Center Study

Mammalian target of rapamycin (mTOR) inhibitors have been shown to reduce proliferation of lymphoid cells; thus, their use for immunosuppression after heart transplantation (HT) may reduce post-transplant lymphoproliferative disorder (PTLD) risk. This study sought to investigate whether the sirolimus (SRL)-based immunosuppression regimen is associated with a decreased risk of PTLD compared with the calcineurin inhibitor (CNI)-based regimen in HT recipients. We retrospectively analyzed 590 patients who received HTs at two large institutions between 1 June 1988 and 31 December 2014. Cox proportional-hazard modeling was used to examine the association between type of primary immunosuppression and PTLD after adjustment for potential confounders, including Epstein-Barr virus (EBV) status, type of induction therapy, and rejection. Conversion from CNI to SRL as primary immunosuppression occurred in 249 patients (42.2%). During a median follow-up of 6.3 years, 30 patients developed PTLD (5.1%). In a univariate analysis, EBV mismatch was strongly associated with increased risk of PTLD (HR 10.0, 95% CI: 3.8-26.6; p < 0.001), and conversion to SRL was found to be protective against development of PTLD (HR 0.19, 95% CI: 0.04-0.80; p = 0.02). In a multivariable model and after adjusting for EBV mismatch, conversion to SRL remained protective against risk of PTLD compared with continued CNI use (HR 0.12, 95% CI: 0.03-0.55; p = 0.006). In conclusion, SRL-based immunosuppression is associated with lower incidence of PTLD after HT. These findings provide evidence of a benefit from conversion to SRL as maintenance therapy for mitigating the risk of PTLD, particularly among patients at high PTLD risk.

Review: immunosuppression for the lung transplant patient

Lung transplantation (LTx) has evolved significantly since its inception and the improvement in LTx outcomes over the last three decades has predominantly been driven by advances in immunosuppression management. Despite the lack of new classes of immunosuppression medications, immunosuppressive strategies have evolved significantly from a universal method to a more targeted approach, reflecting a greater understanding of the need for individualized therapy and careful consideration of all factors that are influenced by immunosuppression choice. This has become increasingly important as the demographics of lung transplant recipients have changed over time, with older and more medically complex candidates being accepted and undergoing LTx. Furthermore, improved survival post lung transplant has translated into more immunosuppression related comorbidities long-term, predominantly chronic kidney disease (CKD) and malignancy, which has required further nuanced management approaches. This review provides an update on current traditional lung transplant immunosuppression strategies, with modifications based on pre-existing recipient factors and comorbidities, peri-operative challenges and long term complications, balanced against the perpetual challenge of chronic lung allograft dysfunction (CLAD). As we continue to explore and understand the complexity of LTx immunology and the interplay of different factors, immunosuppression strategies will require ongoing critical evaluation and personalization in order to continue to improve lung transplant outcomes.

Mammalian Target of Rapamycin Inhibitors Vs Calcineurin Inhibitors in Chronic Graft Rejection After Lung Transplantation: A Systematic Review and Meta-Analysis

BACKGROUND

The number of lung transplantations has been rising constantly. However, use of this therapeutic resource is limited by several issues that are difficult to resolve, such as chronic graft rejection and complications secondary to immunosuppression.

METHODS

This systematic review compared mammalian target of rapamycin (mTOR) inhibitor immunosuppression associated with low-dose calcineurin inhibitors with isolated calcineurin inhibitor immunosuppression on the new-onset chronic rejection development and mortality 12 months after lung transplantation. Three controlled randomized clinical trials (SHITRIT, NOCTET, and 4EVERLUNG) were selected from electronic databases.

RESULTS

Meta-analysis of the data at 12 months postintervention showed that only 4EVERLUNG assessed chronic graft rejection, with a higher incidence in the control group; however, the difference was not statistically significant (P = .197). Significant data were related to an increase in the number of adverse events (P = .0064) and improved renal function (P < .0001) in the mTOR inhibitor-based scheme. The other outcomes indicated a trend toward greater risk of death and acute graft rejection with the use of mTORs.

CONCLUSIONS

The researchers suggest considering the use of mTOR inhibitors, whose greatest benefit is felt by patients with renal dysfunction, in association with the use of calcineurin inhibitors, because of the imminent risk of death among patients with renal failure.

Immunosuppression and Heart Transplantation

Since the first human heart transplant in 1967, immense advancements have been made in the field of immunosuppression. This chapter provides an in-depth analysis of the use of immunosuppressive agents in heart transplant recipients. Evidence regarding maintenance immunosuppressive regimens, the efficacy of induction immunosuppression and corticosteroid weaning, as well as the use of distinct immunosuppression regimens within select patient populations is summarized. This chapter helps elucidate the data regarding contemporary protocols in cardiac transplantation.

Delayed introduction of sirolimus in paediatric intestinal transplant recipients: indications and long-term benefits

To review our experience using sirolimus in a single centre paediatric intestinal transplantation cohort. Intestinal transplant patients with more than 3 months follow-up were divided into two groups according to their immunosuppression regimen: tacrolimus, (TAC group, n = 45 grafts) or sirolimus (SRL group, n = 38 grafts), which included those partially or completely converted from tacrolimus to sirolimus. The indications to switch were tacrolimus side effects and immunological complications. Survival and complications were retrospectively analysed comparing both groups. SRL was introduced 9 months (0 months-16.9 years) after transplant. The main cause for conversion was worsening renal function (45%), followed by haemolytic anaemia (21%) and graft-versus-host-disease (16%). Both groups showed a similar overall patient/graft survival (P = 0.76/0.08) and occurrence of rejection (24%/17%, P = 0.36). Immunological complications did not recur after conversion. Renal function significantly improved in most SRL patients. After a median follow-up of 65.17 months, 28/46 survivors were on SRL, 26 with monotherapy, with good graft function. Over one-third of our patients eventually required SRL conversion that allowed to improve their kidney function and immunological events, without entailing additional complications or survival impairment. Further trials are warranted to clarify the potential improvement of the standard tacrolimus maintenance by sirolimus conversion or addition.

Hepatitis E viral infection regulates estrogen signaling pathways: Inhibition of the cAMPK-PKA-CREB and PI3K-AKT-mTOR signaling pathways

Hepatitis E virus (HEV) infection has become a global concern with high mortality rates among pregnant women, especially those in their third trimester of pregnancy. Estrogen plays an important role in mediating the body, regulating physiological and pathological processes. Estrogen is activated by binding to estrogen receptors (ERs) and mediates rapid signaling events by pathways that involve transmembrane ERs. Our previous study had confirmed that high estrogen levels during pregnancy are associated with high HEV titers. However, the association between HEV infection and estrogen signaling pathways remains unclear. In the present study, the regulation of estrogen signaling pathways by HEV infection was evaluated. Results demonstrated that HEV infection significantly inhibits the cAMP-PKA-CREB and PI3K-AKT-mTOR signaling pathways, but is independent of the Ras-Raf-MEK-ERK signaling pathway. In summary, the increasing estrogen levels and highly activated ERα during pregnancy aggravates HEV replication. The exacerbation of HEV replication, in turn, inhibits ERα expression and suppresses both cAMP-PKA-CREB and PI3K-AKT-mTOR signaling pathways.

Real life experience with mTOR-inhibitors after lung transplantation

Mammalian target of rapamycin inhibitors (mTORi) are increasingly used after lung transplantation as part of a calcineurin inhibitor sparing regimen, aiming to preserve renal function. The aim of our study was to determine whether immunosuppressive therapy using mTORi in lung transplant recipients (LTR) is feasible in practice, or limited by intolerance and adverse events. Data were retrospectively assessed for all LTR transplanted between July 1991 and January 2020. Patients ever receiving mTORi (monotherapy or in combination with calcineurin inhibitor) as treatment of physicians' choice were included. 149/1184 (13%) of the LTR ever received mTORi. Main reasons to start were renal insufficiency (67%) and malignancy (21%). In 52% of the patients, mTORi was stopped due to side effects or drug toxicity after a median time of 159 days. Apart from death, main reasons for discontinuation were infection (19%) and edema (14%). Early discontinuation (<90 days) was mainly due to edema or gastrointestinal intolerance. As mTORi was stopped due to adverse events or drug intolerance in 52% of LTR, cautious consideration of advantages and disadvantages when starting mTORi is recommended.

Twelve-month effects of everolimus on renal and lung function in lung transplantation: differences in chronic lung allograft dysfunction phenotypes

Background:

Chronic lung allograft dysfunction (CLAD), a complication affecting the survival of lung transplanted patients, includes two clinical phenotypes: bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS). Everolimus is used in CLAD because of its antiproliferative mechanism. In lung transplant patients treated with everolimus, the clinical course of renal and lung function has not yet been assessed systematically in CLAD, BOS and RAS patients for more than 6 months.

Methods:

We retrospectively evaluated the 12-month follow-up of renal and lung function of lung-transplanted patients switched to everolimus and evaluated the reduction in immunosuppressant dosage (ISD) and mortality. Subgroups were based on indication for everolimus treatment: CLAD and non-CLAD patients, BOS and RAS among CLAD patients.

Results:

We included 26 patients, 17 with CLAD (10 BOS, seven RAS). After 1 year from the everolimus switch, we observed renal function improvement (serum creatinine −17%, estimated glomerular filtration rate +24%) and stable pulmonary function [forced expiratory volume in the first second (FEV₁) −0.5%, forced vital capacity (FVC) +0.05%]. RAS patients had progressive functional loss, whereas BOS patients had FEV₁ improvement and FVC stability. All-cause mortality was higher in the CLAD versus non-CLAD group (41% versus 11%), without differences between BOS and RAS patients (p > 0.05). All patients had significant and persistent ISD reduction.

Conclusion:

Lung transplant patients treated with everolimus had improvements in renal function and reduced ISD. We observed sustained improvements in lung function for CLAD related to BOS subgroup results, whereas RAS confirmed the 1-year worsening functional trend. Data seem to suggest one more piece of the puzzle in CLAD phenotyping.

A Retrospective Study of Lung Transplantation in Patients With Lymphangioleiomyomatosis: Challenges and Outcomes

Background: Lymphangioleiomyomatosis (LAM) is a rare systemic disease that generally leads to a progressive decline in pulmonary function. Experience, especially from the Asian population, including combined drug therapy before and after lung transplantation (LT) in LAM, is still limited. This study aimed to summarize the clinical data from patients with pulmonary LAM who underwent LT at centers in China. Methods: A retrospective review of all patients with LAM undergoing LT at the two largest centers in China between 2010 and 2018 was conducted. Pre- and posttransplant data were assessed and analyzed. Results: Overall, 25 patients with LAM underwent bilateral LT. The mean age was 35.0 ± 8.6 years at diagnosis and 36.8 ± 9.3 years at the time of transplant. Before LT, only six patients could complete pulmonary function test; the reachable mean forced expiratory volume in one second (FEV₁) before LT was 15.9 ± 6.9%. Twenty-one patients (84%) had a recurrent pneumothorax, four (16.0%) of which required pleurodesis. Eight patients (32%) were treated with sirolimus pretransplant for 3.9 years (1-9 years). The average intra-surgery bleeding volume was 1,280 ± 730 ml in need of a transfusion of 1,316 ± 874 ml due to moderate-to-severe adhesion and pretransplant pleurodesis. The causes of death of four patients (16%) included primary graft dysfunction, bronchial dehiscence with long-term use of sirolimus, and uncontrollable infections. The median follow-up time from LT was 41.1 ± 25.0 months. Conclusions: LT for LAM patients from the Asian population has been reinforced from the data that we presented. Peri-transplantation use of sirolimus and LAM-related complications should be further defined and under constant surveillance.

Rapamycin persistently improves cardiac function in aged, male and female mice, even following cessation of treatment

Even in healthy aging, cardiac morbidity and mortality increase with age in both mice and humans. These effects include a decline in diastolic function, left ventricular hypertrophy, metabolic substrate shifts, and alterations in the cardiac proteome. Previous work from our laboratory indicated that short-term (10-week) treatment with rapamycin, an mTORC1 inhibitor, improved measures of these age-related changes. In this report, we demonstrate that the rapamycin-dependent improvement of diastolic function is highly persistent, while decreases in both cardiac hypertrophy and passive stiffness are substantially persistent 8 weeks after cessation of an 8-week treatment of rapamycin in both male and female 22- to 24-month-old C57BL/6NIA mice. The proteomic and metabolomic abundance changes that occur after 8 weeks of rapamycin treatment have varying persistence after 8 further weeks without the drug. However, rapamycin did lead to a persistent increase in abundance of electron transport chain (ETC) complex components, most of which belonged to Complex I. Although ETC protein abundance and Complex I activity were each differentially affected in males and females, the ratio of Complex I activity to Complex I protein abundance was equally and persistently reduced after rapamycin treatment in both sexes. Thus, rapamycin treatment in the aged mice persistently improved diastolic function and myocardial stiffness, persistently altered the cardiac proteome in the absence of persistent metabolic changes, and led to persistent alterations in mitochondrial respiratory chain activity. These observations suggest that an optimal translational regimen for rapamycin therapy that promotes enhancement of healthspan may involve intermittent short-term treatments.

Efficacy and safety of everolimus treatment on liver transplant recipients: A meta-analysis

BACKGROUND

Everolimus is an effective immunosuppressant in organ transplantation without impaired renal function. The present study aimed to evaluate the efficacy and safety of everolimus therapy in liver transplant recipients.

MATERIALS AND METHODS

A systematic literature search was conducted to identify the eligible studies. The quality of the included studies was assessed. The outcomes of interest were biopsy-proven acute rejection (BPAR), graft loss, death, renal function and adverse events.

RESULTS

Eight trials involving 1570 participants were included. Compared to the standard exposure to calcineurin inhibitors (CNIs), the incidences of BPAR, graft loss and death were not increased in the everolimus combined with reduced CNIs group. The renal function was significantly improved after everolimus combined with reduced CNI therapy, and the glomerular filtration rate (GFR) was estimated to be elevated by 5.59 (95% CI: 2.17-9.01, P = .001) as compared to the standard exposure to CNIs. The risk of any adverse event was increased by everolimus combined with reduced CNI therapy (RR = 1.22, 95% CI: 1.04-1.42, P = .01) as compared to the standard exposure to CNIs. The likelihood of infection was not associated with the regimen. Any publication bias was not identified.

CONCLUSIONS

Although everolimus combined with reduced CNI therapy significantly improved the renal function in liver transplant recipients, it did not influence the incidence of BPAR, graft loss and death. This regimen might be associated with an increased risk of adverse events, which needs to be elucidated further.

Blood Pressure in De Novo Heart Transplant Recipients Treated With Everolimus Compared With a Cyclosporine-based Regimen: Results From the Randomized SCHEDULE Trial

BACKGROUND

Systemic hypertension is prevalent in heart transplant recipients and has been partially attributed to treatment with calcineurin inhibitors (CNIs). SCandinavian HEart transplant De-novo stUdy with earLy calcineurin inhibitors avoidancE trial was the first randomized trial to study early withdrawal of CNIs in de novo heart transplant recipients, comparing an everolimus-based immunosuppressive regimen with conventional CNI-based treatment. As a prespecified secondary endpoint, blood pressure was repeatedly compared across treatment arms.

METHODS

The The SCandinavian HEart transplant De-novo stUdy with earLy calcineurin inhibitors avoidancE trial was a prospective, multicenter, randomized, controlled, parallel-group, open-label trial in de novo adult heart transplant recipients, undertaken at transplant centers in Scandinavia. Blood pressure was assessed with 24-hour ambulatory blood pressure monitoring up to 3 years after heart transplantation (HTx) in 83 patients.

RESULTS

Overall, systolic blood pressure fell with time, from 138 ± 15 mm Hg 2 weeks after HTx to 134 ± 11 mm Hg after 12 months and 132 ± 14 mm Hg after 36 months (P = 0.003). Diastolic blood pressure did not change over time. After 12 months, there was a numerically larger fall in systolic blood pressure in the everolimus arm (between-group difference 8 mm Hg; P = 0.053), and after 36 months, there was a significant between group difference of 13 mm Hg (P = 0.02) in favor of everolimus.

CONCLUSIONS

In this first, randomized trial with early CNI avoidance in de novo HTx recipients, we observed a modest fall in systolic blood pressure over the first 1 to 3 years after transplantation. The fall in systolic blood pressure was more pronounced in patients allocated to everolimus.

A 3-month, Multicenter, Randomized, Open-label Study to Evaluate the Impact on Wound Healing of the Early (vs Delayed) Introduction of Everolimus in De Novo Kidney Transplant Recipients, With a Follow-up Evaluation at 12 Months After Transplant (NEVERWOUND Study)

BACKGROUND

The risk of wound healing complications (WHCs) and the early use of mammalian target of rapamycin inhibitors after kidney transplantation (KT) have not been fully addressed.

METHODS

The NEVERWOUND study is a 3-month, multicenter, randomized, open-label study designed to evaluate whether a delayed (ie, 28 ± 4 d posttransplant) immunosuppression regimen based on everolimus (EVR) reduces the risk of WHC versus EVR started immediately after KT. Secondary endpoints were treatment failure (biopsy-proven acute rejection, graft loss, or death), delayed graft function, patient and graft survival rates, and renal function.

RESULTS

Overall, 394 KT recipients were randomized to receive immediate (N = 197) or delayed (N = 197) EVR after KT. At 3 months, WHC-free rates in the immediate EVR versus delayed EVR arm, considering the worst- and best-case scenario approach, were 0.68 (95% confidence interval [CI], 0.62-0.75) versus 0.62 (95% CI, 0.55-0.68) (log-rank P = 0.56) and 0.70 (95% CI, 0.64-0.77) versus 0.72 (95% CI, 0.65-0.78) (log-rank P = 0.77), respectively. The 3- and 12-month treatment failure rates, delayed graft function and renal function, and patient and graft survival were not different between the arms.

CONCLUSIONS

The early introduction of EVR after KT did not increase the risk of WHC, showing good efficacy and safety profile.

The change of immunosuppressive regimen from calcineurin inhibitors to mammalian target of rapamycin (mTOR) inhibitors and its effect on malignancy following heart transplantation

Malignancy is a significant cause of mortality after organ transplantation. There is an increased rate of malignancy following heart transplantation (HTx) compared to the general population and other organ transplant recipients. Post-HTx patients with a history of malignancy are also at a higher risk of developing new malignancies or exacerbation of their existing malignancies. Mammalian target of Rapamycin inhibitors (mTORIs) are newly introduced immunosuppressive drugs with a unique mechanism of action. By changing the immunosuppressive regimen from classic drugs, especially calcineurin inhibitors (CNIs) to mTORIs, the rate of developing de novo malignancies and the relapse of former malignancies is significantly reduced. However, issues like allograft function, total surveillance of patients, and post-transplantation complications should be considered during the conversion of drug regimens utilizing CNIs to drug regimens employing mTORIs. We reviewed different post-heart transplant maintenance immunosuppressive regimens and their effect on post-HTx malignancies with a focus on mTORIs, compared safety against effectiveness, and gathered conclusions based on our review of the literature, which may lead clinicians to make a better evidence-based decision regarding post-HTx maintenance immunosuppressive drug regimens. Overall, CNI to mTORI conversion in post-HTx maintenance immunosuppressive drug regimens was associated with a reduced rate of developing malignancy in post-HTx patients. Furthermore, nephrotoxicity decreased significantly while using mTORIs in combination with lower doses of CNIs and the rejection rate was equivalent to CNI-only regimens. In conclusion, mTORI-based maintenance immunosuppressive drug regimens seem to be safe and beneficial when considering efficacy vs. adverse effects, and all-cause mortality rates are significantly lower in patients switched to mTORIs when compared to CNI recipients.

mTOR: A Cellular Regulator Interface in Health and Disease

The mechanistic target of Rapamycin (mTOR) is a ubiquitously-conserved serine/threonine kinase, which has a central function in integrating growth signals and orchestrating their physiologic effects on cellular level. mTOR is the core component of differently composed signaling complexes that differ in protein composition and molecular targets. Newly identified classes of mTOR inhibitors are being developed to block autoimmune diseases and transplant rejections but also to treat obesity, diabetes, and different types of cancer. Therefore, the selective and context-dependent inhibition of mTOR activity itself might come into the focus as molecular target to prevent severe diseases and possibly to extend life span. This review provides a general introduction to the molecular composition and physiologic function of mTOR complexes as part of the Special Issue “2018 Select Papers by Cells’ Editorial Board Members”.

Current Topics and Controversies in Pediatric Heart Transplantation: Proceedings of the Pediatric Heart Transplantation Summit 2017

In October 2017, a pediatric heart transplant summit was held in Seattle-the first of its kind internationally-which focused solely upon controversies in pediatric end-stage heart failure management and pediatric heart transplantation. We selected five of the most popular and contentious topics and asked the speakers to provide a position paper. Worldwide, the vast majority of programs perform only a handful of pediatric heart transplants a year. Because of this, these "orphan" areas of investigation provide an opportunity for us as a community to aggregate our collective knowledge, which may represent the only viable way that we might sort through these complex and controversial issues in the field. We hope this represents the first of many such conferences and that this initial selection of papers encourages us to begin this collaborative process.

Immunosuppression for Lung Transplantation: Current and Future

Purpose of the review

The number of lung transplantations performed worldwide continues to increase. There is a growing need in these patients for more effective immunosuppressive medications with less toxicity.

Recent findings

This review article summarizes the recent studies and developments in lung transplant immunosuppression. Novel immunosuppressive medications and strategies used in other solid organ transplantations are being trialed in lung transplantation. This includes the use of co-stimulation blockers like belatacept and mTOR inhibitors like everolimus. Calcineurin sparing regimens have been described in an attempt to minimize nephrotoxicity. Assays to measure the bioactivity of immunosuppressive medications to determine the global immune competence, such as Immuknow assay and Gamma interferon response are gaining traction.

Summary

Immunosuppression in lung transplant is evolving with the development of newer drugs and promising strategies to optimize immunosuppression. Further studies with multicenter randomized trials are required to increase the strength of the evidence.

Cardiovascular disease after transplantation: an emerging role of the immune system

Cardiovascular disease (CVD) after transplantation remains a major concern. Little is known about what drives the increased cardiovascular risk in transplant recipients apart from traditional risk factors. The immune system is involved in the pathogenesis of hypertension, atherosclerosis, and coronary artery disease in the general population. Recently, inhibition of interleukin 1 - β by canakinumab versus placebo decreased the incidence of cardiovascular events. Emerging evidence points to a role of adaptive cellular immunity in the development of CVD. Especially, expansion of pro-inflammatory and antiapoptotic cytotoxic CD4⁺ CD28^null T cells is closely associated with incident CVD in various study populations including transplant recipients. The association of cytomegalovirus exposure with increased cardiovascular mortality might be explained by its capacity to upregulate these cytotoxic cells. Also, humoral immunity seems to be relevant for cardiovascular outcome in transplant recipients. Panel-reactive antibodies at baseline and donor-specific antibodies are independently associated with poor cardiovascular outcome after kidney transplantation. Cardiovascular effects of immunosuppressive drugs and statins do not only imply indirect positive or negative effects on traditional cardiovascular risk factors but also intrinsic immunological effects. How immunosuppressive drugs modify atherosclerosis largely remains elusive.

Individualizing immunosuppression in lung transplantation

Immunosuppression management after lung transplantation continues to evolve, with an increasing number of agents available for use in various combinations allowing for more choice and individualization of immunosuppressive therapy. Therapeutic developments have led to improved outcomes including lower acute rejection rates and improved survival. However, a one size fits all approach for any immunosuppressive strategy may not be best suited to the individual patient and ultimately patient specific factors must be considered when designing the immunosuppressive regimen. Recipient factors including age, race, co-morbidities, immunologic risk, genetic polymorphisms, concomitant and previous pharmacotherapy, and overall immunosuppression burden should be considered. There are several significant drug-drug interactions with select immunosuppressive agents utilized in lung transplant pharmacotherapy that must be considered when choosing and devising a dosing strategy for an individual immunosuppressive agent. Herein, considerations for immunosuppression management in the individual patient will be reviewed.

Overview of Immunosuppressive Therapy in Solid Organ Transplantation

Mechanisms of rejection, new pharmacologic approaches, and genomic medicine are major foci for current research in transplantation. It is hoped that these new agents and personalized immunosuppression will provide for less toxic regimens that are effective in preventing both acute and chronic allograft rejection. Until new agents are available, practitioners must use various combinations of currently approved agents to find the best regimens for improved long-term outcomes.

Experience of Lung Transplantation in Patients with Lymphangioleiomyomatosis at a Brazilian Reference Centre

INTRODUCTION

Lung transplantation (LT) is the standard of care for patients with advanced lung diseases, including lymphangioleiomyomatosis (LAM). LAM accounts for only 1% of all LTs performed in the international registry. As a result, the global experience, including the use of mechanistic target of rapamycin (mTOR) inhibitors before and after LT in LAM, is still limited.

METHODS

We conducted a retrospective review of all LAM patients who underwent LT at our centre between 2003 and 2016. Pre- and post-transplant data were assessed.

RESULTS

Eleven women with LAM underwent LT, representing 3.3% of all procedures. Ten (91%) patients underwent double-LT. The mean age at diagnosis was 39 ± 6 years and the mean FEV₁ before LT was 28 ± 14%. Only one patient underwent pleurodesis for recurrent pneumothorax. Pulmonary hypertension was confirmed in 3 (27%) patients. Four (36%) patients received sirolimus preoperatively; three of them received it until the day of LT, and there was no occurrence of bronchial anastomotic dehiscence after the procedure. Four patients (36%) received mTOR inhibitors post-transplant. The median follow-up from LT was 44 months. There were 3 deaths (27%) during the study and survival probabilities at 1, 3, and 5 years after LT were, 90, 90, and 77%, respectively.

CONCLUSIONS

This data reinforces the role of LT for LAM patients with end-stage disease. The use of sirolimus seems to be safe before LT and the occurrence of complications after LT, including those LAM-related, should be continuously monitored.

Immunosuppression Drug Therapy in Lung Transplantation for Cystic Fibrosis

Cystic fibrosis (CF) is a common indication for lung transplantation (LTx) in children and adults with severe and irreversible lung disease. In the setting of LTx in the CF population, immunosuppressive medications are used to prevent allograft rejection despite the majority of these patients being chronically infected with numerous, and often antibiotic-resistant, pathogens. There is limited evidence for the optimal post-LTx immunosuppression regimen in patients with CF, particularly in children. This article provides a review of immunosuppression regimens in the pediatric and adult CF post-LTx population, investigating drug dosing and monitoring, and medication combinations. Currently used immunosuppressive medications and related systemic adverse effects are reviewed. With limitations of data in the pediatric population, future research should address immunosuppression in these children to help guide pediatric drug management as a means to optimize clinical outcomes after LTx.

Modification of immunosuppressive therapy as risk factor for complications after liver transplantation

Management of complications post-liver transplantation (LT) includes immunosuppressive manipulations with the aim to reduce the overall burden of immunologic suppression and compensate for renal, cardiovascular, metabolic toxicities, and for the increased oncologic risk. Two approaches can be implemented to reduce immunosuppression-related adverse events: upfront schedules tailored to the pretransplant individual patient's risk profile versus downstream modifications in the event of immunosuppression-related complications. Upfront strategies are supported by evidence originating from prospective randomized trials and consist of triple/quadruple schedules whereby calcineurin inhibitors (CNI)-exposure is reduced with combination of anti-CD25 monoclonal antibodies, antimetabolites and corticosteroids. Quadruple regimens allow for staggering of CNI introduction and higher renal function in the early term, but their superiority in the long term has not yet been established. A more recent upfront schedule contemplates early (4 weeks) introduction of mammalian target of rapamycin inhibitor (mTORi) everolimus and allows for reduction of CNI up to 4 years posttransplantation. Incorporation of mTORi has the potential to prolong time to recurrence for patients with hepatocellular carcinoma. However, as suggested by the available evidence, downstream immunosuppressive manipulations are more frequently adopted in clinical practice. These encompass CNI replacement and immunosuppression withdrawal. Switching CNI to mTORi monotherapy is the option most commonly adopted to relieve renal function and compensate for posttransplant malignancies. Its impact is dependent on interval from transplantation and underlying severity of renal impairment. Introduction of mTORi is associated with longer overall survival for patients with extrahepatic posttransplant malignancies, but results are awaited for recurrences of hepatocellular carcinoma. Immunosuppression withdrawal seems feasible (70%) in very long term survivors (>10 years), but is not associated with reversal of immunosuppression-related complications. Awaiting novel immunosuppressive drug categories, integration of upfront strategies with the aim to reduce CNI-exposure and a low threshold for adjustment in the posttransplant course are both advisable to improve long-term outcomes of LT.