Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is a cyanogenic plurifactorial disorder characterized by failed postnatal drop of pulmonary vascular resistance and maintenance of right-to-left shunt across ductus arteriosus and foramen ovale typical of intrauterine life. The pathogenesis of PPHN is very complex and can result from functional (vasoconstriction) or structural (arteriolar remodeling, reduced pulmonary vessels density) anomalies of pulmonary circulation. Etiopathogenetic factors heterogeneity can strongly condition therapeutical results and prognosis of PPHN that is particularly severe in organic forms that are usually refractory to selective pulmonary vasodilator therapy with inhaled nitric oxide. This paper reports the more recent acquisitions on molecular physiopathogenetic mechanisms underlying functional and structural forms of PPHN and illustrates the bases for adoption of new potential treatment strategies for organic PPHN. These strategies aim to reverse pulmonary vascular remodeling in PPHN with arteriolar smooth muscle hypertrophy and stimulate pulmonary vascular and alveolar growth in PPHN associated with lung hypoplasia.In order to restore lung growth in this severe form of PPHN, attention is focused on the results of studies of mesenchymal stem cells and their therapeutical paracrine effects on bronchopulmonry dysplasia, a chronic neonatal lung disease characterized by arrested vascular and alveolar growth and development of pulmonary hypertension.
Highlights
Persistent pulmonary hypertension of the newborn (PPHN), first described as “persistence of fetal circulation” by Gersony and Sinclair in 1969 [1], is a cyanogenic disorder characterized by the lack of postnatal drop of pulmonary vascular resistance and by the persistence of the typical intrauterine right-to-left shunting of blood through foramen ovale and ductus arteriosus
PPHN is a plurifactorial syndrome with a complex pathogenesis sustained by functional or structural pulmonary circulation anomalies
Despite considerable therapeutical progress achieved using inhaled nitric oxide (INO), a selective pulmonary vasodilator, PPHN still remains a major cause of mortality in all neonatal centers
Summary
Persistent pulmonary hypertension of the newborn (PPHN), first described as “persistence of fetal circulation” by Gersony and Sinclair in 1969 [1], is a cyanogenic disorder characterized by the lack of postnatal drop of pulmonary vascular resistance and by the persistence of the typical intrauterine right-to-left shunting of blood through foramen ovale and ductus arteriosus. Elevated fetal pulmonary vascular resistance is partly caused by pulmonary collapse and vessels tortuosity but above all by pulmonary arterioles vasoconstriction. These arterioles present a muscular medial tunic up to the preacinar zones disappearing in intraacinar branches [9]. Pulmonary arteriolar tone can be influenced by several humoral factors present in the perinatal circulation Some of these (thromboxane, endothelin etc.) possess a vasoconstricting action, whereas others (prostacyclin, nitric oxide, etc.) determine vasodilatation [12,13]
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