Treatment of recurrent rejection in heart transplantation: cytolytic therapy or bolus steroids?

OBJECTIVES: The treatment of recurrent rejection in heart transplant recipients has been a controversial issue for many years. The intent of this retrospective study was to perform a risk-benefit analysis between treatment strategies with bolus steroids only versus anti-thymocyte globulins (RATG; 1.5 mg/kg q 4 days). METHODS: Between 1986 and 1993, 69 of 425 patients (17 male, 52 female; mean age 44 +/- 11 years) who had more than one rejection/patient per month (rej/pt per mo) in the first 3 postoperative months were defined as recurrent rejectors. RESULTS: Repetitive methylprednisolone bolus therapy (70 mg/kg q 3 days) was given in 27 patients (group M; 1.4 +/- 0.2 rej/pt per mo) and RATG therapy for one of the rejection episodes of the 42 remaining patients (group A; 1.5 +/- 0.2 rej/pt per mo). The quality of triple drug immunosuppression in the two study groups was comparable. The rejection-free interval (RFI) following RATG treatment in group A was 21.6 +/- 10 days and 22 +/- 11 in group M. In group M, 3 of 27 patients (11%) had a rejection treatment-related infection (2 bacterial; 1 viral) versus 6 of the 42 patients of group A (14.2%; bacterial 1, viral 5). During postoperative months 3-24, 0.15 +/- 0.12 rej/pat per mo were observed in group M and 0.21 +/- 0.13 rej/pat per mo in group A (n.s.). In this 21-month period cytolytic therapy for rejection was initiated in 8 of the remaining 21 patients of group M (38%) and 15 of the remaining 37 patients of group A (40.5%). The absolute survival and the individual causes of death were not affected by the type of initial treatment of recurrent rejection. The actuarial freedom of graft atherosclerosis is comparable in the two groups with 78% in group A versus 79% in group M free of graft atherosclerosis at 3 years postoperatively. CONCLUSIONS: A comparison of cytolytic therapy versus repeated applications of bolus steroids for treatment of recurrent rejection reveals no significant difference in the long-term patient outcome with respect to the incidence of future rejection episodes and survival.

Tricuspid valve regurgitation attributable to endomyocardial biopsies and rejection in heart transplantation

In the present report the prevalence, severity, and risk factors of tricuspid valve regurgitation (TR) in 251 heart transplant recipients have been analyzed retrospectively. Tricuspid valve function was studied by color-flow Doppler echocardiogram and annual heart catheterization. The presence or severity of TR was graded on a scale from 0 (no TR) to 4 (severe). Additional postoperative data included rate of rejection, number of endomyocardial biopsies, incidence of transplant vasculopathy, and preoperative and postoperative hemodynamics. The incidence of grade 3 TR increases from 5% at 1 year to 50% at 4 years after transplantation. Multivariate analysis showed rate of rejection and donor heart weight to be significant risk factors. The ischemic intervals as well as the preoperative and postoperative pulmonary hemodynamics did not affect the severity or prevalence of TR. These results indicate that various factors appear to have an impact on the development of TR and that the prevalence might be lowered by a reduction of the number of biopsies performed and when possible, oversizing of donor hearts.

Emergency lung transplantation after extracorporeal membrane oxygenation

In some patients with acute respiratory failure, the native lungs do not recover during extracorporeal membrane oxygenation (ECMO), or complications occur that preclude the meaningful continuation of ECMO therapy. In such cases, emergency lung transplantation (LTx) represents the only therapeutic alternative. Between May 1988 and April 1993, the authors have performed LTx after ECMO support in five of 111 lung or heart-lung transplantations (4.5%). Two patients presented with early graft failure after unilateral LTx. In these patients, ECMO was used as a bridging device to unilateral re-LTx for 1, resp. 11 days. One patient died 6 months post-operatively from chronic rejection; the other underwent a third LTx and is doing well after 42 months. In three further patients already treated with ECMO for 5 to 12 days for ARDS (n = 2) or acute respiratory failure after liver and kidney transplantation, the native lungs did not recover (n = 2) or pulmonary hemorrhage developed. The last patient (unilateral LTx) and one of the former (bilateral LTx for ARDS) are long-term survivors (12, 30 months). The remaining patient (unilateral LTx for ARDS) had severe multiorgan failure at the time of his operation and died intraoperatively. The authors conclude that ECMO no longer represents a contraindication to subsequent LTx. Their results also support the continued investigation of this combined therapeutic approach.

Local resection of metanephric adenoma with kidney preservation

Metanephric adenoma (MA) is a rare renal neoplasm present at any age. Usually, a total nephrectomy is performed. Some successful partial nephrectomies or selective tumor resections are described in adults but not in children. We present here the case of a 15-month-old boy, the youngest patient yet to be reported with an MA. We performed a local resection of the tumor. Today, 2 1/2 years after surgery, we can document a favorable clinical course and normal ultrasound findings in the follow-up of the operated kidney. This case gives further evidence that organ-sparing resection of MA is feasible in selected cases. A close clinical and ultrasound follow-up is mandatory for this approach.

Eotaxin/CCL11 expression by infiltrating macrophages in rat heart transplants during ongoing acute rejection

Eotaxin/CCL11 chemokine is expressed in different organs, including the heart, but its precise cellular origin in the heart is unknown. Eotaxin is associated with Th2-like responses and exerts its chemotactic effect through the chemokine receptor-3 (CCR3), which is also expressed on mast cells (MC). The aim of our study was to find the cellular origin of eotaxin in the heart, and to assess whether expression is changing during ongoing acute heart transplant rejection, indicating a correlation with mast cell infiltration which we observed in a previous study. In a model of ongoing acute heart transplant rejection in the rat, we found eotaxin mRNA expression within infiltrating macrophages, but not in mast cells, by in situ-hybridization. A five-fold increase in eotaxin protein in rat heart transplants during ongoing acute rejection was measured on day 28 after transplantation, compared to native and isogeneic control hearts. Eotaxin concentrations in donor hearts on day 28 after transplantation were significantly higher compared to recipient hearts, corroborating an origin of eotaxin from cells within the heart, and not from the blood. The quantitative comparison of eotaxin mRNA expression between native hearts, isografts, and allografts, respectively, revealed no statistically significant difference after transplantation, probably due to an overall increase in the housekeeping gene's 18S rRNA during rejection. Quantitative RT-PCR showed an increase in mRNA expression of CCR3, the receptor for eotaxin, during ongoing acute rejection of rat heart allografts. Although a correlation between increasing eotaxin expression by macrophages and mast cell infiltration is suggestive, functional studies will elucidate the role of eotaxin in the process of ongoing acute heart transplant rejection.

ABO blood group incompatible haematopoietic stem cell transplantation and xenograft rejection

The current organ shortage in transplantation medicine stimulates the exploration of new strategies to expand the donor pool including the utilisation of living donors, ABO-incompatible grafts, and xenotransplantation. Preformed natural antibodies (Ab) such as anti-Gal or anti-A/B Ab mediate hyperacute graft rejection and thus represent a major hurdle to the employment of such strategies. In contrast to solid organ transplantation (SOT), ABO blood group incompatibilities are of minor importance in haematopoietic stem cell transplantation (HSCT). Thus, ABO incompatible HSCT may serve as an in vivo model to study carbohydrate antigen (Ag)-mismatched transplantations such as ABO-incompatible SOT or the effect of preformed Ab against Gal in xenotransplantation. This mini-review summarises our clinical and experimental studies performed with the support of the Swiss National Science Foundation program on Implants and Transplants (NFP-46). Part 1 describes data on the clinical outcome of ABO-incompatible HSCT, in particular the incidence of several immunohaematological complications, acute graft-versus-host-disease (GvHD), and the overall survival. Part 2 summarises the measurements of anti-A/B Ab in healthy blood donors and ABO-incompatible HSCT using a novel flow cytometry based method and the potential mechanisms responsible for the loss of anti-A/B Ab observed following minor ABO-incompatible HSCT, ie the occurrence of humoral tolerance. Part 3 analyses the potential of eliminating Gal expression as well as specific complement inhibitors such as dextran sulfate and synthetic tyrosine analogues to protect porcine endothelial cells from xenoreactive Ab-mediated damage in vitro and in a hamster-to-rat heart transplantation model. In conclusion, due to similarities of the immunological hurdles of ABO incompatible transplantations and xenotransplantation, the knowledge obtained from both fields might lead to new strategies to overcome humoral rejection in transplantation.

Risk of acute kidney injury in patients with severe aortic valve stenosis undergoing transcatheter valve replacement

BACKGROUND: Transcatheter aortic valve implantation (TAVI) for high-risk and inoperable patients with severe aortic stenosis is an emerging procedure in cardiovascular medicine. Little is known of the impact of TAVI on renal function. METHODS: We analysed retrospectively renal baseline characteristics and outcome in 58 patients including 2 patients on chronic haemodialysis undergoing TAVI at our institution. Acute kidney injury (AKI) was defined according to the RIFLE classification. RESULTS: Fifty-eight patients with severe symptomatic aortic stenosis not considered suitable for conventional surgical valve replacement with a mean age of 83 +/- 5 years underwent TAVI. Two patients died during transfemoral valve implantation and two patients in the first month after TAVI resulting in a 30-day mortality of 6.9%. Vascular access was transfemoral in 46 patients and transapical in 12. Estimated glomerular filtration rate (eGFR) increased in 30 patients (56%). Fifteen patients (28%) developed AKI, of which four patients had to be dialyzed temporarily and one remained on chronic renal replacement therapy. Risk factors for AKI comprised, among others, transapical access, number of blood transfusions, postinterventional thrombocytopaenia and severe inflammatory response syndrome (SIRS). CONCLUSIONS: TAVI is feasible in patients with a high burden of comorbidities and in patients with pre-existing end-stage renal disease who would be otherwise not considered as candidates for conventional aortic valve replacement. Although GFR improved in more than half of the patients, this benefit was associated with a risk of postinterventional AKI. Future investigations should define preventive measures of peri-procedural kidney injury.

Diastolic dysfunction of the cardiac allograft and maximal exercise capacity

BACKGROUND: Peak oxygen uptake (peak Vo(2)) is an established integrative measurement of maximal exercise capacity in cardiovascular disease. After heart transplantation (HTx) peak Vo(2) remains reduced despite normal systolic left ventricular function, which highlights the relevance of diastolic function. In this study we aim to characterize the predictive significance of cardiac allograft diastolic function for peak Vo(2). METHODS: Peak Vo(2) was measured using a ramp protocol on a bicycle ergometer. Left ventricular (LV) diastolic function was assessed with tissue Doppler imaging sizing the velocity of the early (Ea) and late (Aa) apical movement of the mitral annulus, and conventional Doppler measuring early (E) and late (A) diastolic transmitral flow propagation. Correlation coefficients were calculated and linear regression models fitted. RESULTS: The post-transplant time interval of the 39 HTxs ranged from 0.4 to 20.1 years. The mean age of the recipients was 55 +/- 14 years and body mass index (BMI) was 25.4 +/- 3.9 kg/m(2). Mean LV ejection fraction was 62 +/- 4%, mean LV mass index 108 +/- 22 g/m(2) and mean peak Vo(2) 20.1 +/- 6.3 ml/kg/min. Peak Vo(2) was reduced in patients with more severe diastolic dysfunction (pseudonormal or restrictive transmitral inflow pattern), or when E/Ea was > or =10. Peak Vo(2) correlated with recipient age (r = -0.643, p < 0.001), peak heart rate (r = 0.616, p < 0.001) and BMI (r = -0.417, p = 0.008). Of all echocardiographic measurements, Ea (r = 0.561, p < 0.001) and Ea/Aa (r = 0.495, p = 0.002) correlated best. Multivariate analysis identified age, heart rate, BMI and Ea/Aa as independent predictors of peak Vo(2). CONCLUSIONS: Diastolic dysfunction is relevant for the limitation of maximal exercise capacity after HTx.

The murine Fgfrl1 receptor is essential for the development of the metanephric kidney

Fgfrl1 is a novel member of the fibroblast growth factor receptor family. Its extracellular domain resembles the four conventional Fgfrs, while its intracellular domain lacks the tyrosine kinase domain necessary for Fgf mediated signal transduction. During embryonic development Fgfrl1 is expressed in the musculoskeletal system, in the lung, the pancreas and the metanephric kidney. Targeted disruption of the Fgfrl1 gene leads to the perinatal death of the mice due to a hypoplastic diaphragm, which is unable to inflate the lungs. Here we show that Fgfrl1-/- embryos also fail to develop the metanephric kidney. While the rest of the urogenital system, including bladder, ureter and sexual organs, develops normally, a dramatic reduction of ureteric branching morphogenesis and a lack of mesenchymal-to-epithelial transition in the nephrogenic mesenchyme result in severe renal dysgenesis. The failure of nephron induction might be explained by the absence of the tubulogenic markers Wnt4, Fgf8, Pax8 and Lim1 at E12.5 of the mutant animals. We also observed a loss of Pax2 positive nephron precursor cells and an increase of apoptosis in the cortical zone of the remnant kidney. Fgfrl1 is therefore essential for mesenchymal differentiation in the early steps of nephrogenesis.

Endothelial cell protection by dextran sulfate: a novel strategy to prevent acute vascular rejection in xenotransplantation

We showed recently that low molecular weight dextran sulfate (DXS) acts as an endothelial cell (EC) protectant and prevents human complement- and NK cell-mediated cytotoxicity towards porcine cells in vitro. We therefore hypothesized that DXS, combined with cyclosporine A (CyA), could prevent acute vascular rejection (AVR) in the hamster-to-rat cardiac xenotransplantation model. Untreated, CyA-only, and DXS-only treated rats rejected their grafts within 4-5 days. Of the hearts grafted into rats receiving DXS in combination with CyA, 28% survived more than 30 days. Deposition of anti-hamster antibodies and complement was detected in long-term surviving grafts. Combined with the expression of hemoxygenase 1 (HO-1) on graft EC, these results indicate that accommodation had occurred. Complement activity was normal in rat sera after DXS injection, and while systemic inhibition of the coagulation cascade was observed 1 h after DXS injection, it was absent after 24 h. Moreover, using a fluorescein-labeled DXS (DXS-Fluo) injected 1 day after surgery, we observed a specific binding of DXS-Fluo to the xenograft endothelium. In conclusion, we show here that DXS + CyA induces long-term xenograft survival and we provide evidence that DXS might act as a local EC protectant also in vivo.

Xenograft rejection: IgG1, complement and NK cells team up to activate and destroy the endothelium

Acute vascular rejection represents a formidable barrier to clinical xenotransplantation and it is known that this type of rejection can also be initiated by xenoreactive antibodies that have limited complement-activating ability. Using a sophisticated mouse model, a recent study has provided in vivo evidence for the existence of an IgG(1)-mediated vascular rejection, which uniquely depends on both the activation of complement and interactions with FcgammaRIII on natural killer (NK) cells.

Solid organ transplantation across the ABO histo-blood group barrier: a case report

The ABO blood group system until recently constituted an insuperable barrier for solid organ transplantation, but cases of heart transplantation in infants and kidney transplantation in adults have been reported, wherein ABO-incompatible grafts have been successful. In 1990, the molecular genetic basis of three major alleles at the ABO locus was elucidated; A and B glycosyltransferases are specified by a variety of functional alleles at this locus. The antibody response to ABH antigens, namely, naturally occurring anti-A/B IgM and IgG isotype agglutinins, are controlled preoperatively by recipient conditioning using plasma exchange, immunoadsorption, and immunosuppressive regimens. We report an O-type patient who accidentally received a B-type cardiac allograft in 1997 who survived for 5 years, dying for an unrelated reason. Over a period of 45 months semiquantitatively we monitored the expression of ABO-type antigens in graft heart vessels using monoclonal antibodies on sections of formalin-fixed, paraffin-embedded biopsies. We observed a progressive change in the antigenic profile of graft endothelial cells from B- to O-type, which was first detected at 1 year posttransplant and most prominent 3 years later, the end of the observation period. No temporal relationship was observed between the transition from B to O expression, the anti-B antibody levels or the immunosuppressive regimen.

Pulse mTOR inhibitor treatment effectively controls cyst growth but leads to severe parenchymal and glomerular hypertrophy in rat polycystic kidney disease

The efficacy of mammalian target of rapamycin (mTOR) inhibitors is currently tested in patients affected by autosomal dominant polycystic kidney disease. Treatment with mTOR inhibitors has been associated with numerous side effects. However, the renal-specific effect of mTOR inhibitor treatment cessation in polycystic kidney disease is currently unknown. Therefore, we compared pulse and continuous everolimus treatment in Han:SPRD rats. Four-week-old male heterozygous polycystic and wild-type rats were administered everolimus or vehicle by gavage feeding for 5 wk, followed by 7 wk without treatment, or continuously for 12 wk. Cessation of everolimus did not result in the appearance of renal cysts up to 7 wk postwithdrawal despite the reemergence of S6 kinase activity coupled with an overall increase in cell proliferation. Pulse everolimus treatment resulted in striking noncystic renal parenchymal enlargement and glomerular hypertrophy that was not associated with compromised kidney function. Both treatment regimens ameliorated kidney function, preserved the glomerular-tubular connection, and reduced proteinuria. Pulse treatment at an early age delays cyst development but leads to striking glomerular and parenchymal hypertrophy. Our data might have an impact when long-term treatment using mTOR inhibitors in patients with autosomal dominant polycystic kidney disease is being considered.

Renal allografts with IF/TA display distinct expression profiles of metzincins and related genes

Chronic renal allograft injury is often reflected by interstitial fibrosis (IF) and tubular atrophy (TA) without evidence of specific etiology. In most instances, IF/TA remains an irreversible disorder, representing a major cause of long-term allograft loss. As members of the protease family metzincins and functionally related genes are involved in fibrotic and sclerotic processes of the extracellular matrix (ECM), we hypothesized their deregulation in IF/TA. Gene expression and protein level analyses using allograft biopsies with and without Banff'05 classified IF/TA illustrated their deregulation. Expression profiles of these genes differentiated IF/TA from Banff'05 classified Normal biopsies in three independent microarray studies and demonstrated histological progression of IF/TA I to III. Significant upregulation of matrix metalloprotease-7 (MMP-7) and thrombospondin-2 (THBS-2) in IF/TA biopsies and sera was revealed in two independent patient sets. Furthermore, elevated THBS-2, osteopontin (SPP1) and beta-catenin may play regulatory roles on MMP. Our findings further suggest that deregulated ECM remodeling and possibly epithelial to mesenchymal transition (EMT) are implicated in IF/TA of kidney transplants, and that metzincins and related genes play an important role in these processes. Profiling of these genes may be used to complement IF/TA diagnosis and to disclose IF/TA progression in kidney transplant recipients.