Murine Marfan Syndrome Sildenafil Treatment

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the fibrillin-1 (Fbn1) gene. While aortic rupture is the major cause of mortality in MFS, patients also suffer from poorly understood pulmonary complications. Loss of basal nitric oxide (NO) production and vascular integrity are proposed to take part in MFS aortic root disease, yet their contribution to lung complications has yet to be determined. Due to its capacity to potentiate the vasodilatory NO/cyclic guanylate monophosphate signaling pathway, we assessed whether the phosphodiesterase-5 (PDE5) inhibitor sildenafil (SIL) could attenuate aortic root remodelling and emphysema in a mouse model of MFS. Despite increasing NO-dependent vasodilation, SIL unexpectedly elevated mean arterial blood pressure, failed to inhibit MFS aortic root dilation and exacerbated elastic fibrefiber fragmentation. In the lung, early pulmonary artery dilation observed in untreated MFS mice was delayed by SIL treatment, and severe emphysema-like alveolar destruction was prevented. In addition, improvements in select parameters of lung function were documented. Subsequent micro-array analyses showed changes to gene signatures involved in the inflammatory response in MFS lung treated with SIL, without significant downregulation of connective tissue or TGF-β signalling genes. Since PDE5 inhibition leads to improved lung histopathology and function, the effects of SIL against emphysema warrant further investigation in the settings of MFS despite limited efficacy on aortic root remodelling. n=6 per group, 4 groups, WT-Veh = wild-type vehicle treated controls, WT-SIL = wild-type sildenafil treated, MFS-Veh = Marfan mice vehicle treated, MFS-SIL = Marfan mice sildenafil treated