Fibroblast growth factors (FGFs) and their receptors are highly conserved signaling molecules that have been implicated in postnatal cardiac remodeling. However, it is not known whether cardiomyocyte-expressed FGF receptors are necessary or sufficient for ventricular remodeling in the adult heart. To determine whether cardiomyocytes were competent to respond to an activated FGF receptor, and to determine if this signal would result in the development of hypertrophy, we engineered a doxycycline (DOX)-inducible, cardiomyocyte-specific, constitutively active FGF receptor mouse model (αMHC-rtTA, TRE-caFgfr1-myc). Echocardiographic and hemodynamic analysis indicated that acute expression of caFGFR1 rapidly and directly increased cardiac contractility, while chronic expression resulted in significant hypertrophy with preservation of systolic function. Subsequent histologic analysis showed increased cardiomyocyte cross-sectional area and regions of myocyte disarray and fibrosis, classic features of hypertrophic cardiomyopathy (HCM). Analysis of downstream pathways revealed a lack of clear activation of classical FGF-mediated signaling pathways, but did demonstrate a reduction in Serca2 expression and troponin I phosphorylation. Isolated ventricular myocytes showed enhanced contractility and reduced relaxation, an effect that was partially reversed by inhibition of actin-myosin interactions. We conclude that adult cardiomyocytes are competent to transduce FGF signaling and that FGF signaling is sufficient to promote increased cardiomyocyte contractility in vitro and in vivo through enhanced intrinsic actin-myosin interactions. Long-term, FGFR overexpression results in HCM with a dynamic outflow tract obstruction, and may serve as a unique model of HCM.

Necrotizing enterocolitis (NEC) is one of the most common gastrointestinal conditions affecting 6 to 10% of low-birth-weight infants and remains a leading cause of death. The risk factors associated with NEC are complex and multifactorial, including preterm birth and intrauterine exposure to inflammation and hypoxia. Chorioamnionitis has been associated with intestinal injury in animal and human clinical studies. This review presents current evidence about the clinical impact of the intrauterine environment on intestinal injury during pregnancy and postpregnancy. We present information from our own clinical and laboratory research in conjunction with information collected from an extensive search in the databases PubMed, EMBASE, and Scopus. Prospective multicenter studies, including accurate and precise clinical, maternal, and laboratory predictors (e.g., inflammatory biomarkers), will help identify the mechanisms associated with the placental pathology, the development of NEC, and the impact of in utero-triggered inflammation on the clinical outcomes. Filling the knowledge gap to link the inflammatory surge to postnatal life will aid in identifying at-risk infants for NEC in a timely manner and facilitate the development of novel immunomodulatory treatments or interventions to improve the outcomes of these vulnerable infants. Key Points