No abstract

Background and Aims: Pulmonary Hypertension (PH) represents an aetiologically and clinically heterogeneous disorder accompanied by a severely impaired prognosis. Key steps of PH pathogenesis are vascular and right ventricular myocardial remodelling entailing the re-occurrence of fetal variants of the cell adhesion modulating protein fibronectin (Fn) being virtually absent in healthy adult tissues. These variants are liberated into circulation and are therefore qualified as excellent novel serum biomarkers. Moreover, these molecules might serve as promising therapeutic targets. The current study was aimed at quantifying the serum levels of two functionally important fetal Fn variants (ED-A+ and ED-B+ Fn) in patients suffering from PH due to different aetiologies compared to healthy controls. Methods: Serum levels of ED-A+ and ED-B+ Fn were quantified using novel ELISA protocols established and validated in our group in 80 PH patients and 40 controls. Results were analysed with respect to clinical, laboratory, echocardiographic and functional parameters. Results: Serum levels of ED-A+ Fn (p = 0.001) but not ED-B+ Fn (p = 0.722) were significantly increased in PH patients compared to healthy controls. Thus, the following analyses were performed only for ED-A+ Fn. When dividing PH patients into different aetiological groups according to current ESC guidelines, the increase in ED-A+ Fn in PH patients compared to controls remained significant for group 1 (p = 0.032), 2 (p = 0.007) and 3 (p = 0.001) but not for group 4 (p = 0.156). Correlation analysis revealed a significant relation between ED-A+ Fn and brain natriuretic peptide (BNP) (r = 0.310; p = 0.002), six minutes’ walk test (r = −0.275; p = 0.02) and systolic pulmonary artery pressure (PAPsys) (r = 0.364; p < 0.001). By logistic regression analysis (backward elimination WALD) including a variety of potentially relevant patients’ characteristics, only chronic kidney disease (CKD) (OR: 8.866; CI: 1.779–44.187; p = 0.008), C reactive protein (CRP) (OR: 1.194; CI: 1.011–1.410; p = 0.037) and ED-A+ Fn (OR: 1.045; CI: 1.011–1.080; p = 0.009) could be identified as independent predictors of the presence of PH. Conclusions: Against the background of our results, ED-A+ Fn could serve as a promising novel biomarker of PH with potential value for initial diagnosis and aetiological differentiation. Moreover, it might contribute to more precise risk stratification of PH patients. Beyond that, the future role of ED-A+ Fn as a therapeutic target has to be evaluated in further studies.

Background and aims Diagnosis of Cardiac Allograft Vasculopathy (CAV) following heart transplantation (HTX) is still challenging but of prognostic relevance. Thus, the identification of biomarkers non-invasively detecting the disease is an hitherto unmet clinical need. Fetal variants of the cell adhesion modulating protein Fibronectin (Fn) could be proven to re-occur in the context of chronic rejection in rat and human cardiac tissue after HTX in spatial association to CAV and fibrosis. This study was aimed to determine serum levels of fetal Fn variants in a heterotopic rat HTX model of chronic rejection. Methods Chronic cardiac allograft rejection was induced by heterotopic rat HTX using inbred male Lewis (LEW) rats as donors and Fisher (F344) rats as recipients (n=24). After microsurgical modifications, the allograft was implanted into the abdomen of the recipient animal. Rats were sacrificed after 70 days. Untreated F344 rats were used as controls (n=6). Cardiac tissue was subjected to histological analysis according to a recently established sum-score system between 0 and 10 (0 = no detectable rejection; 1 to 3 = weak rejection; 4 to 7 = moderate rejection; and 8 to 10 = severe rejection). The score includes all relevant parameters of chronic rejection (CAV, lymphocyte infiltration, cardiomyocyte degeneration, fibrosis). Brain natriuretic peptide (BNP) was determined by a commercially available ELISA. Serum levels of both, ED-A domain containing Fn (ED-A+ Fn) and ED-B domain containing Fn (ED-B+ Fn) were quantified using ELISA protocols established in our group. Results Final experiments were performed on day 70, mortality rate was 0%. Histological analysis revealed a chronic cardiac allograft rejection in all transplanted animals (mean sum-score 6.92±1.94) while controls did not exhibit relevant alterations (mean sum-score 0.1±0.2; p<0.001). There were significantly elevated BNP levels in HTX rats (76.16±23.22 pg/ml) compared to controls (352.23±132.09 pg/ml; p<0.001). BNP showed a strong positive correlation to the histological sum-score (r=0.653; p<0.001). Serum levels of ED-A+ Fn (HTX: 34.42±11.4 μg/ml, controls: 17.3±6.13 μg/ml; p=0.009) but not ED-B+ Fn (HTX: 8.58±4.12 μg/ml, controls: 9.4±2.61 μg/ml; p=0.804) were significantly increased in HTX rats qualifying ED-A+ Fn for further analysis with respect to histological signs of chronic rejection. Interestingly, there is a noticeable association to the occurrence of CAV representing 1 out of 4 parameters included in the histological sum-score (r=0.51; p=0.006). Conclusions Chronic cardiac allograft rejection and, in particular, CAV as major long-term prognosis-limiting factor after HTX are accompanied by both, a re-expression and vessel associated tissue deposition of ED-A+ Fn and also a relevant liberation into blood. These results underline the potential impact of ED-A+ Fn as biomarker or potential therapeutic target patients that underwent HTX.