BIOMECHANCIAL CHARACTERIZATION OF POSTNATAL GROWTH BEHAVIOR IN THE OVINE MAIN PULMONARY ARTERY

It has been estimated that worldwide 600,000 babies are born annually with significant congenital heart disease. In children with congenital heart disease, normal growth and hemodynamic function of the pulmonary arteries and aorta become disrupted due to structural heart defects and/or genetic disorders. Congenital heart and related vascular defects cause increased flow and pulmonary pressure leading to unfavorable vascular remodeling that result in pulmonary arterial hypertension. Congenital abnormalities of these arteries often necessitate surgical repair or the use of autologous tissue and synthetic biomaterials as vascular grafts. The optimal vascular replacement should be able to accommodate somatic growth and closely mimic the structure, function and physiologic environment of native vessels. In recent years, there has been a growing interest in the development of a living autologous tissue graft that could address the critical need for growing substitutes in the repair of congenital cardiovascular defects. \ud In the current study, the biomechanical characteristics of the native ovine main pulmonary artery during postnatal growth period were delineated to establish the benchmarks for tissue engineering approaches. The local postnatal alterations in the surface geometry of the pulmonary artery based on magnetic resonance images of the endoluminal arterial surface were estimated. The regional growth adaptations of the mechanical behavior and elastin structure were subsequently quantified. The collagen organization and recruitment behavior using a biaxial stretching device combined with multiphoton microscopy were measured. The experimental measurements were finally fit to a structurally-based constitutive model of the arterial wall. The results of this study can also help elucidate the governing mechanisms of normal remodeling and growth process by enhancing our knowledge of alterations in the geometry and structure-mechanics relationship of the pulmonary arterial wall during postnatal maturation.\u