Distinct Expression of Non-Muscle Myosin IIB in Pulmonary Arteries of Patients with Aortic Stenosis versus Insufficiency Undergoing a Ross Procedure

Abstract Background Clinical studies have revealed a greater risk of pulmonary autograft dilatation after the Ross procedure in patients with preoperative aortic insufficiency (AI). The present study examined whether the morphological, biomechanical and cellular properties of the pulmonary artery (PA) from patients with AI were phenotypically different compared to patients diagnosed with aortic stenosis (AS). Methods PA segments were harvested from patients undergoing the Ross procedure for AS (n=16) and AI (n=6). Preoperative aortic annulus was significantly larger (p Results Collagen and elastin content in the media of the PA wall were similar in patients with AS and AI. Elastic modulus and energy loss of the PA were not significantly different between groups. In the media of the PA, expression of a panel of vascular smooth muscle cell specific proteins were similar in patients with AS and AI. By contrast, non-muscle myosin IIB protein levels in the PA of AS patients were significantly higher compared to AI patients and immunofluorescence identified staining in α-smooth muscle actin(+)-vascular smooth muscle cells. Conclusion Despite comparable morphological and biomechanical properties the disparate expression of non-muscle myosin IIB protein distinguishes the PA of patients with AI from patients with AS. The biological role in vascular smooth muscle cells and the potential contribution of non-muscle myosin IIB to pulmonary autograft dilatation in a subset of AI patients after the Ross procedure remain to be determined.