Extra-domain A containing fibronectin in pulmonary hypertension and treatment effects of a function-blocking antibody.

Pulmonary vascular and right ventricular remodelling processes are important for development and progression of pulmonary hypertension (PH). The current study analyzed the functional role of the extra domain A containing fibronectin (ED-A+ Fn) for the development of PH by comparing ED-A+ Fn knockout (KO) and wild-type (WT) mice as well as the effects of an antibody-based therapeutical approach in a model of monocrotaline (MCT)-induced PH, which will be validated in a model of Sugen 5416/Hypoxia induced PH. PH was induced using monocrotaline (MCT) (PH mice). 69 mice were divided into the following groups: sham-treated controls (WT: n=7; KO: n=7), PH mice without specific treatment (WT: n=12; KO: n=10), PH mice treated with a dual endothelin receptor antagonist (MAC; WT: n=6; KO: n=11), WT PH mice treated with the F8 antibody, specifically recognizing ED-A+ Fn, (n=8) and WT PH mice treated with an antibody of irrelevant antigen specificity (KSF, n=8). Compared to controls, WT_PH mice showed a significant elevation of the right ventricular systolic pressure (RVPsys, p=0.04) and RV functional impairment including increased basal right ventricular (RVbasal, p=0.016) diameter or tricuspid annular plane systolic excursion (TAPSE, p=0.008). In contrast, KO PH did not show such effects compared to controls (p=n.s.). In WT_PH mice treated with F8, hemodynamic and echocardiographic parameters were significantly improved compared to untreated WT_PH mice or those treated with the KSF antibody (p<0.05). On the microscopic level, KO_PH mice showed significantly less tissue damage compared to the WT_PH mice (p=0.008). Furthermore, lung tissue damage could significantly be reduced after F8 treatment (p=0.04). Additionally, these findings could be verified in the Sugen 5416/Hypoxia mouse model, in which F8 significantly improved echocardiographic, hemodynamic and histologic parameters. ED-A+ Fn is of crucial importance for PH pathogenesis representing a promising therapeutic target in PH. We here show a novel therapeutic approach using antibody-mediated functional blockade of ED-A+ Fn capable to attenuate and partially reverse PH-associated tissue remodelling.

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