Keith McNeil

BMPR2 Haploinsufficiency as the Inherited Molecular Mechanism for Primary Pulmonary Hypertension

Primary pulmonary hypertension (PPH) is a potentially lethal disorder, because the elevation of the pulmonary arterial pressure may result in right-heart failure. Histologically, the disorder is characterized by proliferation of pulmonary-artery smooth muscle and endothelial cells, by intimal hyperplasia, and by in situ thrombus formation. Heterozygous mutations within the bone morphogenetic protein type II receptor (BMPR-II) gene (BMPR2), of the transforming growth factor beta (TGF-beta) cell-signaling superfamily, have been identified in familial and sporadic cases of PPH. We report the molecular spectrum of BMPR2 mutations in 47 additional families with PPH and in three patients with sporadic PPH. Among the cohort of patients, we have identified 22 novel mutations, including 4 partial deletions, distributed throughout the BMPR2 gene. The majority (58%) of mutations are predicted to lead to a premature termination codon. We have also investigated the functional impact and genotype-phenotype relationships, to elucidate the mechanisms contributing to pathogenesis of this important vascular disease. In vitro expression analysis demonstrated loss of BMPR-II function for a number of the identified mutations. These data support the suggestion that haploinsufficiency represents the common molecular mechanism in PPH. Marked variability of the age at onset of disease was observed both within and between families. Taken together, these studies illustrate the considerable heterogeneity of BMPR2 mutations that cause PPH, and they strongly suggest that additional factors, genetic and/or environmental, may be required for the development of the clinical phenotype.

Development of bronchiolitis obliterans syndrome in recipients of heart-lung transplantation : Early risk factors

Given the internationally recognized definition of bronchiolitis obliterans syndrome (BOS) and longer follow up of heart-lung transplant recipients, it is possible to establish some of the major risk factors for development and progression of BOS. Between April 1984 and 31 December 1993, 157 patients underwent heart-lung transplantation; 126 survived at least six months after operation and so were at risk of developing BOS. The following early risk factors were assessed for development of BOS grade 1 (21-35% decline in FEV1) and progression from grade 1 to grade 2 (36-50% decline in FEV1): age, gender and underlying diagnosis of the recipient, evidence of acute rejection and cytomegalovirus (CMV) infection within 6 months of operation, peak FEV1 achieved, age and gender of the donor, cold ischemic time of the graft, and matching of CMV serological status and HLA antigens of donor and recipient. The number of acute rejection episodes observed remained the single most important determinant of development of BOS grade 1 (relative risk 1.17 (1.06, 1.29), P=0.002) and progression to BOS grade 2 (relative risk 1.58 (1.02, 2.46), P=0.03). No other factors were significantly related to development or progression of BOS, although both evidence of CMV infection and disease and the number of HLA mismatches increased the risk. Bronchiolitis obliterans syndrome is a major problem for medium-to-long-term survivors of cardiothoracic transplantation. Acute rejection early after transplantation is a sensitive prognostic indicator of subsequent functional decline and requires prompt attention.

Airway complications after lung transplantation: treatment and long-term outcome

BACKGROUNDnAirway complications are a significant cause of morbidity after lung transplantation. Effective treatment reduces the impact of these complications.nnnMETHODSnData from 123 lung (99 single, 24 bilateral) transplants were reviewed. Potential risk factors for airway complications were analyzed. Stenoses were treated with expanding metal (Gianturco) stents.nnnRESULTSnMean follow-up was 749 days. Thirty-five complications developed in 28 recipients (complication rate: 23.8%/anastomosis). Mean time to diagnosis was 47 days. Only Aspergillus infection and airway necrosis were significantly associated with development of complications (p < 0.00001 and p < 0.03, respectively). Stenosis was diagnosed an average of 42 days posttransplant. Average decline in forced expiratory volume in 1 second (FEV1) was 39%. Eighteen patients (13 single and 5 bilateral) required stent insertion. Mean increase in FEV1 poststenting was 87%. Two stent patients died from infectious complications. Six patients required further intervention. Long-term survival and FEV1 did not differ from nonstented patients.nnnCONCLUSIONSnAspergillus and airway necrosis are associated with the development of airway complications. Expanding metal stents are an effective long-term treatment.

Comparison of mycophenolate mofetil and azathioprine for prevention of bronchiolitis obliterans syndrome in de novo lung transplant recipients.

Background. There are no data on the effects of mycophenolate mofetil (MMF) on the incidence of bronchiolitis obliterans syndrome (BOS) in lung-transplant patients. This study attempted to determine whether MMF reduces the incidence of BOS in de novo lung transplant recipients compared with azathioprine (AZA). Methods. This prospective, randomized, open-label, multicenter study compared the effects of MMF with AZA in combination with induction therapy, cyclosporine (Neoral) and corticosteroids in patients receiving their first lung transplant. Primary endpoint was incidence of BOS at 3 years. Secondary endpoints were incidence of acute rejection, time to first rejection event, and survival. Results. The incidence of acute rejection and the time to first rejection event at 1 and 3 years did not differ between groups (54.1% vs. 53.8% and 56.6% vs. 60.3% for MMF and AZA respectively). Survival at 1 year tended to be better in patients receiving MMF (88 vs. 80%, P=0.07). At year 3, there was no difference in survival or in the incidence, severity or time to acquisition of BOS between the two groups. Treatment was generally well tolerated, however more patients withdrew from AZA treatment than from MMF (59.6% vs. 46.5%, P=0.02). As a result, there was an imbalance in the observation times of the two groups (876±395 vs. 947±326 days). Conclusions. No differences were seen in the incidence of acute rejection or BOS in lung transplant recipients treated with MMF or AZA. This null result may have been influenced by the shorter observation time for AZA patients.

Acute and chronic onset of bronchiolitis obliterans syndrome (BOS): are they different entities?

BACKGROUNDnBronchiolitis obliterans syndrome (BOS), defined as an irreversible, staged decline in forced expiratory volume in 1 second (FEV(1)), is an established marker of obliterative bronchiolitis. Potential causes of BOS include sub-clinical chronic rejection and/or exaggerated healing response following acute injury. BOS may thus result from two or more distinct processes, both acute and chronic.nnnMETHODSnA total of 5,916 measurements of FEV(1) from 204 lung transplant recipients surviving at least 6 months after transplantation were analyzed. Follow-up ranged from 6 months to 13 years. By adjusting for the acute effects of rejection, pulmonary infection and measurement variation on FEV(1) trace, patients either had a linear decline characterized by a single acute drop in FEV(1) of >15% at BOS onset, or a chronic linear decline in FEV(1). The fraction having acute onset was estimated. Acute events occurring within the first 6 months were assessed as risk factors for acute onset BOS.nnnRESULTSnOf the 204 patients, 8% died before BOS onset and 18% were BOS-free at analysis. For 18% of patients, BOS onset followed a chronic linear decline in FEV(1) of 3.7% per year, with a median time of BOS onset >99 months. For 56% of patients, BOS onset followed an acute drop in FEV(1) of median 33.8% (95% CI 19.1% to 39.7%), with median onset time of 52 months. During the first 6 months, acute rejection was significantly and independently associated with acute onset of BOS (relative risk = 1.15 per episode, 95% CI [1.03 to 1.29], p = 0.01), whereas pulmonary infection and cytomegalovirus (CMV) infection were not. Acute BOS onset followed a documented acute event in the previous 6 months in 38 of 114 (33%) of cases.nnnCONCLUSIONSnBOS likely reflects more than one process. Compared with those who had a slow linear decline in lung function, acute BOS onset was associated with acute rejection in the first 6 months, was often triggered by an acute event and had poor prognosis, with obliterative bronchiolitis (OB) the main cause of death.

The incidence of end-stage renal failure in 17 years of heart transplantation: a single center experience

BACKGROUNDnPredictions of the incidence of renal failure within a heart transplant population are based on the early experiences of cyclosporine (CsA)-based immunosuppression. We report a single-center experience of end-stage renal failure (ESRF) during a 17-year period encompassing current lower dose CsA regimens.nnnMETHODnProspectively collected data were analyzed on all patients who underwent first heart transplants between April 1982 and February 1999 (n = 697). We further categorized patients by the date of transplantation into a higher and lower dosage maintenance CsA group.nnnRESULTSnEnd-stage renal failure developed in 44 patients. The median time to dialysis was 87 months after transplantation and was independent of the initial CsA regimens used (p = 0.798). In the ESRF group, 14 underwent hemodialysis, 28 underwent peritoneal dialysis, and 9 underwent renal transplantation. One- and 5-year survival rates after dialysis were 82% and 62% respectively. The incidence of ESRF at our institution was 5.8%. It increased with post-operative survival and was independent of the initial CsA regimen used. We found no difference in pre-transplant age, sex, diagnosis, immediate post-operative creatinine, or the development of diabetes between the ESRF group and controls. The ESRF group received higher dosages of CsA within the first post-transplant year, although this did not reach significance (CsA dosage, 5.9 microg/kg/day vs 5.1 microg/kg/day, respectively p = 0.075).nnnCONCLUSIONSnLower dosage CsA regimes have not altered the incidence of ESRF at our institution, suggesting an individual predisposition to nephropathy. Therefore, reduction in the future incidence of ESRF may rely on extremely low-dose or calcineurin-free immunosuppression regimes.

Heart-lung transplantation for Eisenmenger syndrome: early and long-term results.

BACKGROUNDnHeart-lung transplantation (HLT) for Eisenmenger syndrome (ES) provides superior early and intermediate survival when compared with other forms of transplantation. The early risk factors and long-term outcome of HLT for ES are less well defined.nnnMETHODSnWe analyzed 263 patients who had undergone HLT at our institution during more than 15 years. Fifty-one consecutive patients with ES who underwent HLT, 33 (65%) of which had simple anatomy, were compared with 212 cases having HLT for other indications (non-ES).nnnRESULTSnFemale sex and previous thoracotomy were more prevalent in the ES group. Patients with ES had greater postoperative blood loss and returned more frequently to the operating room for control of bleeding. There were 8 (16%) early deaths in the ES group compared with 27 (13%) in non-ES (p = 0.65). One-, 5-, and 10-year survival rates for ES were 72.6%, 51.3%, and 27.6%, respectively, compared with non-ES of 74.1%, 48.1%, and 26.0%, respectively, and there was no difference in survival overall (p = 0.54). Among ES patients, previous thoracotomy was a risk factor for hospital death. A subgroup analysis based on simple versus complex type of ES did not show statistically significant differences in terms of postoperative course or early or late survival.nnnCONCLUSIONSnHeart-lung transplantation is a successful procedure for ES. Despite a greater frequency of risk factors and a more difficult operative course, early and late outcome with HLT is comparable to non-ES recipients.

Combined transplantation of the heart, lung, and liver.

Combined transplantation of the heart, lung, and liver may be indicated in patients with either end-stage respiratory failure complicated by advanced liver disease or end-stage liver failure complicated by advanced lung disease. A retrospective review of nine patients who underwent combined heart-lung-liver transplantation in Cambridge (1986-99) was carried out. The 1-year and 5-year actuarial survival was 56% and 42%, respectively. Combined heart-lung-liver transplantation is a feasible option for a few patients and has a 5-year survival similar to heart-lung transplantation but with a lower incidence of acute and chronic rejection.

Cytomegalovirus antibody status of donor/recipient does not influence the incidence of bronchiolitis obliterans syndrome in lung transplantation

BACKGROUNDnWe have previously reported that prophylaxis for cytomegalovirus (CMV) infection does not influence the incidence of bronchiolitis obliterans syndrome (BOS) at 2 years. The effect of CMV infection (without evidence of disease) on BOS is still not well understood. Moreover, the incidence and risk factors for development of BOS in CMV-antibody-negative donor/recipient matches in lung transplantation have not been described. The aim of this study is to determine the incidence of BOS in lung transplant patients with CMV-antibody-negative (-) donors (D) and recipients (R), and to evaluate the risk factors that predispose to BOS in this sub-group.nnnMETHODnA retrospective study of data from the transplant database of our center was performed. All single-lung (SL), double-lung (DL) and heart-lung block (HL) transplant patients who survived >2 years post-transplant were included in the study group. They were grouped as follows: D(-)/R(-), n = 102; D(-)/R(+), n = 70; D(+)/R(-), n = 33, and D(+)/R(+), n = 92.nnnRESULTSnThe 3-year BOS-free survival rates were 65%, 56%, 58% and 67%, respectively, and the incidence rates of BOS at 5 years post-transplant in the different groups were 57%, 62%, 78% and 55% (p > 0.05). In the D(-)/R(-) group, the significant risk factor for developing BOS was three or more episodes of acute rejection (p = 0.02). The mean numbers of acute rejection episodes per 100 patients-days within the first 6 months were 1.28, 1.06, 0.50 and 1.11 (p < 0.001 overall) for the four groups, respectively.nnnCONCLUSIONnAlthough CMV is believed to be a risk factor for BOS, its absence did not affect the occurrence or incidence of BOS in lung transplant patients. The main risk factor for BOS in the CMV-antibody-negative population remains the number of acute rejection episodes within the first 6 months after transplantation.

Interleukin 1 and Chronic Rejection: Possible Genetic Links in Human Heart Allografts

Chronic rejection is a leading cause of graft loss in thoracic transplant recipients. Studies on the pathogenesis of chronic rejection have suggested a contributory role for certain cytokines and growth factors. The activity of these mediators is subject to genetic variation if a polymorphism alters expression, or function, of the ligand or its receptor. Here we have asked if certain cytokine and growth factor gene polymorphisms correlate with chronic rejection in recipients of thoracic allografts. In a retrospective analysis of 179 recipients of thoracic organ transplants (128 heart; 36 heart‐lung; and 15 lung), polymorphisms in 8 genes that influence the inflammatory process, namely IL1B, IL1R1, IL1RN, IL6, IL10, TNFA, TGFB1 and FCGRIIA, were examined. Genotypic data from recipients who had either died or been re‐transplanted as a result of chronic rejection (nu2003=u200396) were then compared to those of recipients who had a functioning graft for more than 11u2003years (nu2003=u200383). In the heart graft recipients, only those polymorphisms that influenced expression of the IL1 receptor antagonist gene had a significant correlation with graft survival, with homozygosity for the IL1RN*1 allele being associated with rejection. The alternative, less frequent IL1RN alleles emerged as genomic predictors of long‐term allograft survival. This association was especially strong when IL1 region haplotypes were considered, particularly when analysis was confined to heart transplant recipients who had had multiple acute rejection episodes (ORu2003>u200320). This case‐control study indicates that gene polymorphisms which influence IL1 bioactivity also influence the progression of chronic rejection in heart grafts.