Abstract 2959: TGF-beta Is A Promising Biomarker For Monitoring The Aortic Root Dilatation And Losartan Therapy In Marfan Syndrome

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Objectives: Aortic root dilatation is the main cause of morbidity and mortality in Marfan syndrome (MFS), a disorder caused by mutations in the gene encoding fibrillin-1 and consequent dysregulation of TGF-beta signaling. The aim of this study was to discover a serological biomarker for the aortic root dilatation in a mouse model of MFS, that was also responsive to losartan therapy. Methods: Serum samples from mice heterozygous for a fibrillin-1 missense mutation (C1039G/+) and wild-type mice treated with losartan or placebo were obtained at 10 weeks, 6 months and 10 months of age. Total (acid activated) TGF-beta 1 serum concentrations were measured by ELISA. Echo measurements of the aortic root were obtained from a parasternal long axis view at 10 months of age. Results: Mean TGF-beta serum concentrations were higher in C1039G/+ mice compared to wild-type mice (p=0.01; 80.0 ng/ml (n=5) vs. 58.3 ng/ml (n=4) at 10 weeks, 117.4 ng/ml (n=11) vs. 87.0 ng/ml (n=6) at 6 months, 137.5 ng/ml (n=3) vs. 103.0 ng/ml (n=2) at 10 months, respectively). Losartan-treated C1039G/+ mice had significantly lower mean TGF-beta serum levels compared to C1039G/+ mice with placebo (p=0.007; 92.9 ng/ml (n=5) vs. 117.4 ng/ml (n=11) at 6 months, 101.2 ng/ml (n=13) vs. 137.5 ng/ml (n=3) at 10 months, respectively). Mean TGF-beta serum concentrations in losartan-treated C1039G/+ mice and wild-type mice with placebo were not significant different (p=0.3; 92.9 ng/ml (n=5) vs. 87.0 ng/ml (n=6) at 6 months, 101.2 ng/ml (n=13) vs. 103.0 ng/ml (n=2) at 10 months, respectively). Echo analyses revealed significantly smaller mean aortic root diameters in 10 months old wild-type and losartan-treated C1039G/+ mice compared to age-matched C1039G/+ mice with placebo (p=0.001; 1.94 mm (n=2) and 2.06 mm (n=13) vs. 2.4 mm (n=3), respectively). Conclusions: TGF-beta serum levels are higher in C1039G/+ mice compared to wild-type mice. Losartan treatment of C1039G/+ mice reduces TGF-beta serum concentrations and aortic root diameters towards wild-type levels. Serum TGF-beta is a promising biomarker for prognostication and monitoring the therapeutic response to losartan therapy in Marfan syndrome.