Search

The ascending aorta and pulmonary trunk develop from the common truncus arteriosus that later becomes symmetrically divided by the aorticopulmonary septum. Normally, the systolic pressure value and the diastolic pressure gradient in the aorta is much higher than that in the pulmonary artery. In the Ross procedure, patient’s diseased aortic valve is replaced with their own pulmonary valve and as a consequence the pulmonary trunk is placed in the aortic root position. Typically, a reinforcement of transposed pulmonary trunk is necessary to avoid vessel dilation. In order to investigate how the blood flow characteristics determine the vessel wall structure we examined by immunochemistry the wall of normal aorta (NA), normal pulmonary trunk (NPT), transposed pulmonary trunk (trPT) and transposed pulmonary trunk with reinforcement (trPT-R). Throughout the tunica media of NA, elastic fibers form numerous, conspicuous and orderly arranged wavy lamellae that parallel thin layers of smooth muscle cells between the internal and external elastic membrane. In the NPT, smooth muscle cells run amid collagen fibers and form layers that are thicker and irregular, with elastic fibers arranged accordingly. In the trPT, intima denudation and media disruptions were observed. In the tunica media, smooth muscle cells were abundant, but muscle fibers, with irregular profiles and no discernible alignment, were widely spaced with intervening collagen fibers. In the trPA-R, the endothelial lining was preserved and elastic fibers formed a thick and highly organized layer of concentric lamellae in the middle third of tunica media. The structure of normal aorta and pulmonary trunk, both elastic arteries, with common embryological origin, differs significantly in terms of smooth muscle and elastic sheets number and organization. The animal model of Ross procedure with pulmonary trunk in aorta position further underscores the role of blood pressure and mechanical stress in vessel wall modification., Italian Journal of Anatomy and Embryology, Vol 119, No 1 (Supplement) 2014

The Ross procedure has emerged as a popular choice for aortic valve replacement in infants and children. However, pulmonary artery (PA) autograft dilation remains the major concern; hence, several modifications of the valve implantation techniques, such as reinforcing the autografts with a tubular synthetic mesh, have been reported. With the aim to prevent dilation and permit the normal growth of the neo-aortic root following pulmonary autograft implantation, we assessed the biological effect and long term performance of an external bioresorbable reinforcement for PA autograft in an experimental Ross model in growing animals. An experimental model of translocation of the pulmonary trunk as autograft in aortic position, funded on the Hook’s law and Laplace equilibrium, has been developed and performed under cardiopulmonary bypass in young lambs. The PA without reinforcement (n=5) was compared to PA reinforced with new scaffold polymer with an external armour of Polytetrafluoroethylene. The PA autograft diameter was measured using transoesophageal echography at day 0 and at 6 months and compared to the distal aortic diameter. Pathological analysis of the PA autograft reinforced was performed at 6 months and the results were compared to those of a control group with no reinforcement (n=5) Animal weight was 25+5 kg at day 0 and 58+10 kg at 6 months and the reference aortic diameter increased from 14+1mm at day 0 to 17+2mm at 6 months. With no reinforcement, an instantaneous PA graft distension (27,4+2mm) was noted followed by an aneurysmal formation at 6 months (38+3mm). Reinforcement with scaffold polymer on polidioxanone allowed maintaining the PA graft diameter close to the reference value (17+2mm at day 0). Immunohistochemistry revealed MMP-9 overexpression indicating the induction of a matrix remodeling process that are not detectable in the control group. Mallory staining revealed elastin deposition in the reinforced PA in comparison to the collagen present in the non-reinforced group, reliably suggesting a shift towards an elastic remodeling and arterialization. PicroSirius red staining reveled in the control group collagen fibers non- homogeneously distributed with a increased cellularity indicating inflammatory infiltrates. The reinforced PA displays more organized and dense collagen fibers in the “elastic zone” of the vessel and less pronounced cellular infiltrate. In conclusion, bioresorbable external polydioxanone-based reinforcement allowed a structural rearrangement of PA autograft consisting of media reorganization with an increase in the elastic wall component. Such histological outcome arguably prevented autograft dilation and conferred enhanced mechanical properties on the PA wall, Italian Journal of Anatomy and Embryology, Vol. 120, No. 1 (Supplement) 2015

Cardiac cells and extracellular matrix (ECM) are reciprocally related and their characteristics are modified in response to developmental or pathophysiological cues. Adult human cardiac tissue regeneration mediated by cardiac stem cells (CSCs) is strictly regulated and, hypothetically, impaired by the ECM-CSC signalling in the pathological conditions. To test this hypothesis, we isolated cardiac fibroblasts (CFs) and CSCs from the atria of age-matched adult human normal (n=9) and pathological hearts (ischemic cardiomyopathy, n=11). The CFs were cultured in order to obtain ECM coating and conditioned medium, which were characterized by immunoblotting and ELISA, respectively. Next, we examined the effects of CF-derived ECM and CF-conditioned medium on normal and pathological CSC proliferation, apoptosis, and migration in vitro. The ECM produced by CFs from normal heart was composed mainly of fibronectin, laminin α2 and collagen I, while that produced by CFs from hearts with ischemic cardiomyopathy contained also laminin α1 and tenascin X. Compared to the normal CF-conditioned medium, that conditioned by pathological CFs contained twice as much IGF1 and HGF, and it stimulated proliferation and migration, while reducing apoptosis of CSCs. In the presence of pathological CF-derived ECM, there was a nearly 2-fold increase (p, Italian Journal of Anatomy and Embryology, Vol 117, No 2 (Supplement) 2012

Italian Journal of Anatomy and Embryology, Vol 115, No 1/2 (Supplement) 2010