Effects of Prone Sleeping on Cerebral Oxygenation in Preterm Infants.

OBJECTIVE: To determine the effect of prone sleeping on cerebral oxygenation in preterm infants in the neonatal intensive care unit. STUDY DESIGN: Preterm infants, divided into extremely preterm (gestational age 24-28 weeks; n = 23) and very preterm (gestational age 29-34 weeks; n = 33) groups, were studied weekly until discharge in prone and supine positions during active and quiet sleep. Cerebral tissue oxygenation index (TOI) and arterial oxygen saturation (SaO2) were recorded. Cerebral fractional tissue extraction (CFOE) was calculated as CFOE = (SaO2 - TOI)/SaO2. RESULTS: In extremely preterm infants, CFOE increased modestly in the prone position in both sleep states at age 1 week, in no change in TOI despite higher SaO2. In contrast, the very preterm infants did not have position-related differences in CFOE until the fifth week of life. In the very preterm infants, TOI decreased and CFOE increased with active sleep compared with quiet sleep and with increasing postnatal age. CONCLUSION: At 1 week of age, prone sleeping increased CFOE in extremely preterm infants, suggesting reduced cerebral blood flow. Our findings reveal important physiological insights in clinically stable preterm infants. Further studies are needed to verify our findings in unstable preterm infants regarding the potential risk of cerebral injury in the prone sleeping position in early postnatal life.

Dobutamine treatment reduces inflammation in the preterm fetal sheep brain exposed to acute hypoxia.

BACKGROUND: Impaired cerebral autoregulation in preterm infants makes circulatory management important to avoid cerebral hypoxic-ischemic injury. Dobutamine is frequently used as inotropic treatment in preterm neonates, but its effects on the brain exposed to cerebral hypoxia are unknown. We hypothesized that dobutamine would protect the immature brain from cerebral hypoxic injury. METHODS: In preterm (0.6 gestation) fetal sheep, dobutamine (Dob, 10 µg/kg/min) or saline (Sal) was infused intravenously for 74 h. Two hours after the beginning of the infusion, umbilical cord occlusion (UCO) was performed to produce fetal asphyxia (Sal+UCO: n = 9, Dob+UCO: n = 7), or sham occlusion (Sal+sham: n = 7, Dob+sham: n = 6) was performed. Brains were collected 72 h later for neuropathology. RESULTS: Dobutamine did not induce cerebral changes in the sham UCO group. UCO increased apoptosis and microglia density in white matter, hippocampus, and caudate nucleus, and astrocyte density in the caudate nucleus. Dobutamine commenced before UCO reduced microglia infiltration in the white matter, and microglial and astrocyte density in the caudate. CONCLUSION: In preterm hypoxia-induced brain injury, dobutamine decreases neuroinflammation in the white matter and caudate, and reduces astrogliosis in the caudate. Early administration of dobutamine in preterm infants for cardiovascular stabilization appears safe and may be neuroprotective against unforeseeable cerebral hypoxic injury.

A percutaneous fetal cardiac catheterization technique for pulmonary valvuloplasty and valvulotomy in a mid-gestation lamb model.

OBJECTIVE: We aimed to assess the feasibility of using a percutaneous transhepatic cardiac catheterization technique to perform fetal pulmonary valvuloplasty and valvulotomy under ultrasound guidance at mid-gestation. METHOD: In 13 mid-gestation fetal lambs without cardiac pathology, percutaneous transhepatic cardiac catheterization was used to position a coronary angioplasty catheter within the pulmonary valve. The balloon was inflated/deflated several times, simulating pulmonary valvuloplasty. In another two fetal lambs, a guidewire tip was positioned against the pulmonary valve, and unipolar diathermy was applied to simulate perforation of an atretic valve. RESULTS: Percutaneous access followed by right heart catheterization was successful in all cases. One fetus died following right ventricle perforation. Simulated pulmonary valvuloplasty was successful in nine cases using catheters with 6-mm-long balloons but unsuccessful in two cases (both survived) using 12-mm-long balloons. In one case, the catheter could not be inserted as the cannula became dislodged. Diathermy of the pulmonary valve was successful in both attempts. CONCLUSION: We successfully simulated in utero perforation and dilation of the pulmonary valve using percutaneous transhepatic access in fetal lambs. The technique has potential for clinical translation into treatment for human fetuses with critical pulmonary stenosis or pulmonary atresia with intact ventricular septum.

Cerebral vascular regulation and brain injury in preterm infants.

Cerebrovascular lesions, mainly germinal matrix hemorrhage and ischemic injury to the periventricular white matter, are major causes of adverse neurodevelopmental outcome in preterm infants. Cerebrovascular lesions and neuromorbidity increase with decreasing gestational age, with the white matter predominantly affected. Developmental immaturity in the cerebral circulation, including ongoing angiogenesis and vasoregulatory immaturity, plays a major role in the severity and pattern of preterm brain injury. Prevention of this injury requires insight into pathogenesis. Cerebral blood flow (CBF) is low in the preterm white matter, which also has blunted vasoreactivity compared with other brain regions. Vasoreactivity in the preterm brain to cerebral perfusion pressure, oxygen, carbon dioxide, and neuronal metabolism is also immature. This could be related to immaturity of both the vasculature and vasoactive signaling. Other pathologies arising from preterm birth and the neonatal intensive care environment itself may contribute to impaired vasoreactivity and ineffective CBF regulation, resulting in the marked variations in cerebral hemodynamics reported both within and between infants depending on their clinical condition. Many gaps exist in our understanding of how neonatal treatment procedures and medications have an impact on cerebral hemodynamics and preterm brain injury. Future research directions for neuroprotective strategies include establishing cotside, real-time clinical reference values for cerebral hemodynamics and vasoregulatory capacity and to demonstrate that these thresholds improve long-term outcomes for the preterm infant. In addition, stimulation of vascular development and repair with growth factor and cell-based therapies also hold promise.

Injury and repair in the very immature lung following brief mechanical ventilation.

Mechanical ventilation (MV) of very premature infants contributes to lung injury and bronchopulmonary dysplasia (BPD), the effects of which can be long-lasting. Little is currently known about the ability of the very immature lung to recover from ventilator-induced lung injury. Our objective was to determine the ability of the injured very immature lung to repair in the absence of continued ventilation and to identify potential mechanisms. At 125 days gestational age (days GA, 0.85 of term), fetal sheep were partially exposed by hysterotomy under anesthesia and aseptic conditions; they were intubated and ventilated for 2 h with an injurious MV protocol and then returned to the uterus to continue development. Necropsy was performed at either 1 day (short-term group, 126 days GA, n = 6) or 15 days (long-term group, 140 days GA, n = 5) after MV; controls were unventilated (n = 7-8). At 1 day after MV, lungs displayed signs of injury, including hemorrhage, disorganized elastin and collagen deposition in the distal airspaces, altered morphology, significantly reduced secondary septal crest density, and decreased airspace. Bronchioles had thickened epithelium with evidence of injury and sloughing. Relative mRNA levels of early response genes (connective tissue growth factor, cysteine-rich 61, and early growth response-1) and proinflammatory cytokines [interleukins (IL)-1ß, IL-6, IL-8, tumor necrosis factor-α, and transforming growth factor-ß] were not different between groups 1 day after MV. At 15 days after MV, lung structure was normal with no evidence of injury. We conclude that 2 h of MV induces severe injury in the very immature lung and that these lungs have the capacity to repair spontaneously in the absence of further ventilation.

The Movember Prostate Cancer Landscape Analysis: an assessment of unmet research needs.

Prostate cancer is a heterogeneous cancer with widely varying levels of morbidity and mortality. Approaches to prostate cancer screening, diagnosis, surveillance, treatment and management differ around the world. To identify the highest priority research needs across the prostate cancer biomedical research domain, Movember conducted a landscape analysis with the aim of maximizing the effect of future research investment through global collaborative efforts and partnerships. A global Landscape Analysis Committee (LAC) was established to act as an independent group of experts across urology, medical oncology, radiation oncology, radiology, pathology, translational research, health economics and patient advocacy. Men with prostate cancer and thought leaders from a variety of disciplines provided a range of key insights through a range of interviews. Insights were prioritized against predetermined criteria to understand the areas of greatest unmet need. From these efforts, 17 research needs in prostate cancer were agreed on and prioritized, and 3 received the maximum prioritization score by the LAC: first, to establish more sensitive and specific tests to improve disease screening and diagnosis; second, to develop indicators to better stratify low-risk prostate cancer for determining which men should go on active surveillance; and third, to integrate companion diagnostics into randomized clinical trials to enable prediction of treatment response. On the basis of the findings from the landscape analysis, Movember will now have an increased focus on addressing the specific research needs that have been identified, with particular investment in research efforts that reduce disease progression and lead to improved therapies for advanced prostate cancer.

Evaluation of 3K3A-Activated Protein C to Treat Neonatal Hypoxic Ischemic Brain Injury in the Spiny Mouse.

Neonatal hypoxic ischemic encephalopathy (HIE) resulting from intrapartum asphyxia is a global problem that causes severe disabilities and up to 1 million deaths annually. A variant form of activated protein C, 3K3A-APC, has cytoprotective properties that attenuate brain injury in models of adult stroke. In this study, we compared the ability of 3K3A-APC and APC (wild-type (wt)) to attenuate neonatal brain injury, using the spiny mouse (Acomys cahirinus) model of intrapartum asphyxia. Pups were delivered at 38 days of gestation (term = 39 days), with an intrapartum hypoxic insult of 7.5 min (intrapartum asphyxia cohort), or immediate removal from the uterus (control cohort). After 1 h, pups received a subcutaneous injection of 3K3A-APC or wild-type APC (wtAPC) at 7 mg/kg, or vehicle (saline). At 24 h of age, pups were killed and brain tissue was collected for measurement of inflammation and cell death using RT-qPCR and histopathology. Intrapartum asphyxia increased weight loss, inflammation, and apoptosis/necrosis in the newborn brain. 3K3A-APC administration maintained body weight and ameliorated an asphyxia-induced increase of TGFß1 messenger RNA expression in the cerebral cortex, immune cell aggregation in the corpus callosum, and cell death in the deep gray matter and hippocampus. In the cortex, 3K3A-APC appeared to exacerbate the immune response to the hypoxic ischemic insult. While wtAPC reduced cell death in the corpus callosum and hippocampus following intrapartum asphyxia, it increased markers of neuro-inflammation and cell death in control pups. These findings suggest 3K3A-APC administration may be a useful therapy to reduce cell death and neonatal brain injury associated with HIE.

Does moderate preterm birth lead to altered arterial pressure? Studies in sheep.

1. Low birth weight (LBW) is associated with an increased risk of cardiovascular disease. Preterm birth is a major determinant of LBW and has been shown to result in elevated arterial pressure (AP) in humans, but few studies have investigated the effects of preterm birth in the absence of potentially confounding factors. Our aim was to determine whether moderately preterm birth per se alters the postnatal development of AP in lambs. 2. Preterm lambs were delivered approximately 14 days before term (i.e. approximately 133 days of gestation); controls were born at term (approximately 147 days). Mean arterial pressure (MAP), heart rate (HR), blood composition and indices of growth were measured at 4 and 8 weeks post term-equivalent age (PTEA). We also studied a separate cohort of preterm and term sheep as young adults (approximately 1.1 years). 3. Preterm lambs had significantly lower birth weights than term lambs, but bodyweights were not significantly different by Day 12 PTEA. In addition, MAP, HR and most blood variables did not differ between term and preterm lambs at 4 or 8 weeks PTEA. Preterm birth per se did not alter MAP or HR in young adult sheep. 4. Low birth weight due to preterm birth does not result in an altered AP during early postnatal life or at maturity. Moderate intrauterine growth restriction (IUGR) due to twinning, which further reduces birth weight, does not affect MAP in preterm lambs. Other factors, such as the degree of prematurity or IUGR, exposure to corticosteroids or postnatal nutrition, may be important in the later development of elevated AP.

Effects of hypoxia-ischemia and inotropes on expression of cardiac adrenoceptors in the preterm fetal sheep.

Preterm infants frequently suffer cardiovascular compromise, with hypotension and/or low systemic blood flow, leading to tissue hypoxia-ischemia (HI). Many preterm infants respond inadequately to inotropic treatments using adrenergic agonists such as dobutamine (DB) or dopamine (DA). This may be because of altered cardiac adrenoceptor expression because of tissue HI or prolonged exposure to adrenergic agonists. We assessed the effects of severe HI with and without DB/DA treatment on cardiac adrenoceptor expression in preterm fetal sheep. Fetal sheep (93-95 days) exposed to sham surgery or severe HI induced by umbilical cord occlusion received intravenous DB or saline for 74 h (HI + DB, HI, Sham + DB, Sham). The HI groups were also compared with fetal sheep exposed to HI and DA. Fetal hearts were collected to determine ß-adrenoceptor numbers using [125I]-cyanopindolol binding and mRNA expression of ß1-, ß2-, α1A-, α2A-, or α2B-adrenoceptors. The HI group had increased ß-adrenoceptor numbers compared with all other groups in all four heart chambers ( P < 0.05). This increase in ß-adrenoceptor numbers in the HI group was significantly reduced by DB infusion in all four heart chambers, but DA infusion in the HI group only reduced ß-adrenoceptor numbers in the left atria and ventricle. DB alone did not affect ß-adrenoceptor numbers in the sham animals. Changes in ß1-adrenoceptor mRNA levels trended to parallel the binding results. We conclude that HI upregulates preterm fetal cardiac ß-adrenoceptors, but prolonged exposure to adrenergic agonists downregulates adrenoceptors in the preterm heart exposed to HI and may underpin the frequent failure of inotropic therapy in preterm infants. NEW & NOTEWORTHY This is the first study, to our knowledge, on the effects of hypoxia-ischemia and adrenergic agonists on adrenoceptors in the preterm heart. In fetal sheep, we demonstrate that hypoxia-ischemia increases cardiac ß-adrenoceptor numbers. However, exposure to both hypoxia-ischemia and adrenergic agonists (dobutamine or dopamine) reduces the increase in ß-adrenoceptor numbers, which may underpin the inadequate response in human preterm infants to inotropic therapy using adrenergic agonists. Dobutamine alone does not affect the cardiac adrenoceptors in the sham animals.

Percutaneous fetal cardiac catheterization technique for stenting the foramen ovale in a midgestation lamb model.

BACKGROUND: Intact or highly restricted intra-atrial septum can be reliably diagnosed in the human fetus as early as 22 to 24 weeks of gestation. Fetal interventions targeting the atrial septum have used a direct approach through the atrial wall. Here, we report stenting of the foramen ovale with a large, open-cell stent via percutaneous access through the fetal hepatic vein in a sheep model. METHODS AND RESULTS: In 5 fetal sheep of 109 to 111 days of gestation (term, 147 days), the fetal hepatic vein was punctured percutaneously under ultrasound guidance and a 13.3-cm 14-gauge intravenous catheter was inserted. After catheterization of the inferior vena cava, right atrium, foramen ovale, and left atrium with a guidewire and 1.8F to 2.6F tapered catheter, a self-expandable, 8×12-mm flexible open-cell stent was positioned in an unrestricted foramen ovale. Flow and fetal well-being were documented for 45 minutes after the procedure. Access to the left atrium was achieved in all 5 animals and all survived. In 4 animals, the stent was successfully positioned in the foramen ovale. One fetus was born at term and euthanized on day 3: postmortem examination confirmed the patency of the stent. The other 3 fetuses were well after being monitored by ultrasound for 45 minutes. In 1 animal, the stent dislodged immediately after release obstructing the mitral valve. This fetus developed ascites and was euthanized after 4 days. CONCLUSIONS: It is feasible to safely advance a large diameter, self-expandable, open-cell design stent into the fetal atrial septum via a percutaneous access route through the fetal hepatic vein.

Mechanical ventilation injury and repair in extremely and very preterm lungs.

BACKGROUND: Extremely preterm infants often receive mechanical ventilation (MV), which can contribute to bronchopulmonary dysplasia (BPD). However, the effects of MV alone on the extremely preterm lung and the lung's capacity for repair are poorly understood. AIM: To characterise lung injury induced by MV alone, and mechanisms of injury and repair, in extremely preterm lungs and to compare them with very preterm lungs. METHODS: Extremely preterm lambs (0.75 of term) were transiently exposed by hysterotomy and underwent 2 h of injurious MV. Lungs were collected 24 h and at 15 d after MV. Immunohistochemistry and morphometry were used to characterise injury and repair processes. qRT-PCR was performed on extremely and very preterm (0.85 of term) lungs 24 h after MV to assess molecular injury and repair responses. RESULTS: 24 h after MV at 0.75 of term, lung parenchyma and bronchioles were severely injured; tissue space and myofibroblast density were increased, collagen and elastin fibres were deformed and secondary crest density was reduced. Bronchioles contained debris and their epithelium was injured and thickened. 24 h after MV at 0.75 and 0.85 of term, mRNA expression of potential mediators of lung repair were significantly increased. By 15 days after MV, most lung injury had resolved without treatment. CONCLUSIONS: Extremely immature lungs, particularly bronchioles, are severely injured by 2 h of MV. In the absence of continued ventilation these injured lungs are capable of repair. At 24 h after MV, genes associated with injurious MV are unaltered, while potential repair genes are activated in both extremely and very preterm lungs.

The influence of naturally occurring differences in birthweight on ventricular cardiomyocyte number in sheep.

In most species including man, cardiomyocytes cease proliferating soon after birth when they become terminally differentiated. A reduced complement of cardiomyocytes in infancy may adversely impact on the function and adaptive capabilities of the heart in later life. Low birthweight is associated with an increased risk of heart disease in adults, but little is known about its effect on the number of cardiomyocytes. Using naturally occurring differences in birthweight, our aim was to determine the effect of birthweight on cardiomyocyte number in postnatal lambs. At 9 weeks after term birth, when the final number of cardiomyocytes is considered to be established, hearts were collected at necropsy from seven singleton and seven twin lambs. Hearts were perfusion-fixed, and tissue samples were systematically taken from the left ventricle plus intraventricular septum (LV+S) and the right ventricle (RV). The number of cardiomyocyte nuclei was estimated using an unbiased optical disector-fractionator stereological technique, and the total number of cardiomyocytes was determined. Weights of the total heart, LV+S and RV were significantly related to both birthweight and necropsy weight. In the LV+S but not the RV, cardiomyocyte number was significantly and directly related to heart tissue weight, birthweight, and necropsy weight. We conclude that the final number of cardiomyocytes in the LV+S is related to prenatal and early postnatal growth, and is proportionate to the weight of heart tissue. A low cardiomyocyte number in the LV+S following restricted fetal growth may contribute to the increased incidence of heart disease in adults born with low birthweight. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.

Repeated ethanol exposure during late gestation alters the maturation and innate immune status of the ovine fetal lung.

Little is known about the effects of fetal ethanol exposure on lung development. Our aim was to determine the effects of repeated ethanol exposure during late gestation on fetal lung growth, maturation, and inflammatory status. Pregnant ewes were chronically catheterized at 91 days of gestational age (DGA; term approximately 147 days). From 95-133 DGA, ewes were given a 1-h daily infusion of either 0.75 g ethanol/kg (n = 9) or saline (n = 8), with tissue collection at 134 DGA. Fetal lungs were examined for changes in tissue growth, structure, maturation, inflammation, and oxidative stress. Between treatment groups, there were no differences in lung weight, DNA and protein contents, percent proliferating and apoptotic cells, tissue and air-space fractions, alveolar number and mean linear intercept, septal thickness, type-II cell number and elastin content. Ethanol exposure caused a 75% increase in pulmonary collagen I alpha1 mRNA levels (P < 0.05) and a significant increase in collagen deposition. Surfactant protein (SP)-A and SP-B mRNA levels were approximately one third of control levels following ethanol exposure (P < 0.05). The mRNA levels of the proinflammatory cytokines interleukin (IL)-1beta and IL-8 were also lower (P < 0.05) in ethanol-exposed fetuses compared with controls. Pulmonary malondialdehyde levels tended to be increased (P = 0.07) in ethanol-exposed fetuses. Daily exposure of the fetus to ethanol during the last third of gestation alters extracellular matrix deposition and surfactant protein gene expression, which could increase the risk of respiratory distress syndrome after birth. Changes to the innate immune status of the fetus could increase the susceptibility of the neonatal lungs to infection.