Respiratory Development and Programming

Head of Group: Prof Richard Harding
Senior Research Officers: Dr Robert DeMatteo and Dr Foula Sozo
Neonatologist: Dr Takushi Hanita (Visiting researcher)
Research Assistant: Victoria Stokes
Animal Technician: Tash Blasch
PhD students: Kelly Kenna, Nadine Brew, Megan O"Reilly and Noreen Ishak
Masters Students: Joanna Goh and Anzari Atik
Honours students 2009: Sheena Bouch and Melissa Vela

Respiratory Development and Programming

Respiratory illnesses are a major cause of death and disability at all ages, and represents a major cost to the society in terms of medical expenses, lost days of productivity and reduced quality of life. It is now apparent that the risk of respiratory illnesses such as asthma and chronic obstructive lung disease, as well as the rate of the age-related decline in lung function, can be exacerbated by an adverse environment during fetal and neonatal life, when the lungs are developing. Particular factors that have been identified as having the potential to cause persistent alterations in lung structure and function include fetal growth restriction (e.g. by placental insufficiency or maternal undernutrition), premature birth, exposure to an inflammatory intra-uterine environment, ventilator-induced lung injury, maternal alcohol ingestion, and respiratory infections during infancy.

The major research interests of the Respiratory Development and Programming group are:

1 The role of premature birth in the early developmental origins of cardio-respiratory diseases

Premature birth is a serious environmental challenge faced by 8-10% of all infants. In infants born before term, many organs are obliged to function before they are fully mature, leading to persistent alterations in their development. This can contribute to life-long impairments in respiratory, cardiovascular and neurological function for example. The extent to which altered development is due to preterm birth per se or injury induced by medical supportive procedures is at present unclear. Our studies are aimed at understanding how premature birth alters lung structure and function from infancy through to adulthood; such information is unavailable from human observations. In collaboration with others we are researching the effects of preterm birth on the development of the cardiovascular system and kidneys.

2 Mechanisms underlying the effects of fetal and postnatal growth restriction on adult lung structure and function

Restricted growth during fetal and early postnatal life has been shown to cause permanent alterations in the development and later function of the lungs. In humans, there is a strong correlation between early growth rates and lung function and respiratory illnesses. These effects could be related to hypoxia or nutrient restriction during early life. We are currently exploring the mechanisms whereby nutrient availability and growth induce persistent alterations in structural development of the lung parenchyma and conducting airways. In collaborative studies, we are investigating the effects on development of the heart and kidneys.

3 Protecting the developing brain from injury caused by hypoxia and/or inflammation: the development of neuroprotective strategies

As well as injury to the developing lung, we are interested in the aetiology of altered brain development and fetal brain injury resulting from prenatal hypoxia or inflammation. In collaboration with Prof S. Rees and Dr M Tolcos (University of Melbourne) we are investigating the mechanisms by which prenatal hypoxia and inflammation injure the preterm fetal brain, in particular the sub-cortical and periventricular white matter. Recent studies are aimed at exploring the potential neuroprotective effects of agents such as erythropoietin (EPO). In addition, we are investigating the effects of caffeine on the developing brain, as caffeine is commonly administered to preterm babies in order to stimulate breathing.

4 Effects of alcohol exposure on the fetus during late gestation

In human infants and children the effects of prenatal exposure to high levels of alcohol are well defined. However, the effects of exposures to lower levels of alcohol are less well understood. A number of studies have shown that short exposures or “binges” may be more harmful to the developing brain than chronic exposures. We have recently shown that fetal exposure to daily episodes of maternal alcohol ingestion alters lung development and also leads to changes within blood vessels. In collaborative studies we are exploring the effects of daily prenatal alcohol exposure on the developing brain, kidney and heart.

5 Mechanisms responsible for the disadvantage in male survival following pre-term birth

It is well established that male preterm infants have an increased risk of respiratory illness and death compared to female preterm infants. The exact mechanisms that cause this “male disadvantage” are not known. The male disadvantage is also seen in preterm lambs; therefore we are using prematurely born lambs as our animal model to represent preterm infants. We wish to determine why male preterm lambs are more likely to die from respiratory insufficiency than females. To help us understand the gender dimorphism in respiratory outcomes and morbidity, we perform tests of lung function and cardiovascular performance, as well as histological and molecular analyses of lung tissue. Attention is also focussed on the composition of pulmonary surfactant, as this is critical for infant survival.

6 Ventilator-induced lung injury and repair in very immature ovine lungs

The lungs of very preterm infants are immature and often unable to sustain the respiratory needs of the infant. These infants usually require mechanical ventilation to survive; however, ventilating these infants can injure the lung causing inflammation, abnormal lung development and the cessation of alveolarisation. As a result, approximately a third of ventilated infants develop bronchopulmonary dysplasia (BPD). Until recently, researchers have found it difficult to assess the specific factors by which mechanical ventilation causes lung injury. However, this has been overcome with the development of a new model with which to study ventilator-induced lung injury. This model involves mechanical ventilation of the fetus whilst still being maintained by the placenta. Early findings indicate that the immature fetal lung is injured by mechanical ventilation but that it also has the capacity to repair in utero in the absence of further treatments. These studies will be used to isolate genes that are altered by ventilator-induced lung injury and that may lead to the abnormal lung development seen in infants with bronchopulmonary dysplasia or those involved with lung repair processes.

7 Hyperoxia-induced injury in the developing lung

Advances in medical care have improved the outcomes of infants born very prematurely, leading to an increased rate of survival. However, infants born preterm often require ventilatory support to survive as a result of their lungs being structurally immature and surfactant deficient. Exposing the preterm lung to high levels of oxygen (hyperoxia) is thought to be one of the major contributing factors of bronchopulmonary dysplasia (BPD) and lung injury. Using a mouse model of neonatal exposure to hyperoxia, we aim to investigate its effects on the structure and function of the developing airways of the lung. In doing so, we will obtain a better understanding of the poor lung function often reported in children and adults who were born preterm and developed BPD.

Conferences and workshops

• Fetal and Neonatal Workshop

Recent Publications

Research Books Edited

Harding R, Pinkerton KE, Plopper CG. (2004) The Lung: Development, Aging and the Environment. Elsevier Academic Press, UK. (27 chapters, 395 pages).

Harding R, Bocking AD. (2001) Fetal Growth and Development, Cambridge University Press, Cambridge, UK. (13 chapters, 283 pages)

Recent Journal Articles, Reviews and Chapters

2009 publications

De Matteo R, Snibson K, Thompson B, Koumoundouros E, Harding R.  Lung function in developing lambs: is it affected by preterm birth? Journal of Applied Physiology [E-Pub Aug 13].

Harding R, Hooper SB. (2009) Physiologic mechanisms of normal and altered lung growth before and after birth. In: Fetal and Neonatal Physiology; Fourth edition, Edited by R. Polin, W. Fox and S. Abman. Published by Elsevier Science / W.B. Saunders, pp 802-811.

Harding R, Snibson K, O’Reilly M, Maritz GS (2009). Early environmental influences on lung development: Implications for lung function and respiratory health throughout life. In: “Early Life Origins of Human Health and Disease”. Eds. MG Ross and JP Newnham. Karger, Basel; pp 77-88.

O’Reilly M, Hooper SB, Allison BJ, Flecknoe SF, Snibson K, Harding R, Sozo F. Airway remodeling following ventilator-induced injury of the very immature lung in sheep. American Journal of Physiology: Lung Cellular and Molecular Physiology [E-pub Aug 28].

Probyn M, Cock M, Duncan J, Tolcos M, Rees S, Harding R. The anti-inflammatory agent N-acetyl cysteine exacerbates endotoxin-induced hypoxemia and hypotension and induces polycythemia in the ovine fetus. Neonatology [in press].

Rees S, Hale N, DeMatteo R, Cardamone L, Tolcos M, Loeliger M, Mackintosh    A, Shields A, Probyn M, Scheerlinck J-P, Harding R. (2009) Erythropoietin is neuroprotective in a preterm ovine model of endotoxin-induced brain damage. Brain (in press)

Schulzke SM, Polglase GR, Sozo F, Pillow JJ. Feasibility and short-term effects of biphasic positive airway pressure versus assist-control ventilation in preterm lambs. Pediatr Res [E-pub Aug 16].

Sozo F, O’Day L, Maritz G, Kenna K, Stacy V, Brew N, Walker D, Bocking A, Brien J, Harding R. (2009) Repeated ethanol exposure during late gestation alters the maturation and innate immune status of the ovine fetal lung. American Journal of Physiology: Lung Cell Mol Physiol. 296: L510-8.

Stacy V, De Matteo R, Brew N, Sozo F, Probyn ME, Harding R, Black MJ. (2009) The influence of naturally occurring differences in birthweight on ventricular cardiomyocyte number in sheep. Anat Rec (Hoboken). 292: 29-37.

2008 publications

Allison BJ, Crossley KJ, Flecknoe SJ, Davis PG, Morley CJ, Harding R, Hooper SB. (2008) Ventilation of the very immature lung in utero induces injury and BPD-like changes in lung structure in fetal sheep. Pediatric Research 64:387-92.

Dalitz P, Cock M, Harding R*, Rees S*. (2008) Injurious effects of acute ethanol exposure during late gestation on developing white matter in fetal sheep.  International Journal of Developmental Neuroscience 26: 391-399.

DeMatteo R, Stacy V, Probyn M, Brew N, Blasch N, Harding R. (2008) Does moderate preterm birth lead to altered arterial pressure? Studies in sheep. Clinical and Experimental Pharmacology and Physiology 35: 1426-1432.

DeMatteo R, Stacy V, Probyn M, Desai M, Ross M, Harding R. (2008) The perinatal development of arterial pressure in sheep: effects of low birthweight due to twinning. Reproductive Sciences 15: 66-74.

Gray SP, Kenna K, Bertram JF, Hoy WE, Yan EB, Bocking AD, Brien JF, Walker DW, Harding R, Moritz KM. (2008) Repeated ethanol exposure during late gestation decreases nephron endowment in fetal sheep. American Journal of Physiology: Regulatory, Integrative and Comparative 295: R568-574.

Harding R, Hooper SB. (2008) Lung growth and maturation. In: Fetal Medicine: Basic Science & Clinical Practice, 2nd edition; eds C Rodeck and M Whittle. Elsevier UK, p 133-146.

Maritz GS, Probyn M, DeMatteo R, Snibson K, Harding R. (2008) Lung structure at maturity is influenced by postnatal growth rate but not by moderately preterm birth in sheep. Neonatology 93: 28-35.

Probyn ME, Stacy V, Desai M, Ross M, Harding R. (2008) Spontaneously occurring differences in fetal weight do not affect blood pressure, the hypothalamic-pituitary-adrenal axis or the renin-angiotensin system in the late gestation ovine fetus. Reproduction, Fertility and Development 20: 451-459.

Rees S, Harding R, Walker D. (2008) An adverse intrauterine environment: implications for injury and altered development of the brain. International Journal of Developmental Neuroscience 26: 3-11.

Snibson K, Harding R. (2008) Postnatal growth rate, but not mild preterm birth, influences airway structure in adult sheep challenged with house dust mite. Experimental Lung Research 34:69-84.

Verbeek M, Richardson HL, Parslow PM, Walker AM, Harding R, Horne RSC. (2008)  Arousal and ventilatory responses to mild hypoxia in preterm infants. Journal of Sleep Research 17: 344-353.

2007 publications

Gatford KL, Dalitz PA, Cock ML, Harding R, Owens JA. (2007) Acute ethanol exposure in pregnancy alters the insulin-like growth factor axis of fetal and maternal sheep. American Journal of Physiology; Endocrinology and Metabolism. 292: E494-500.

Loeliger M, Duncan J, Cock ML, Harding R, Rees SM. (2007) Vulnerability of dopaminergic amacrine cells and optic nerve myelination to prenatal endotoxin exposure. Investigative Ophthalmology and Visual Science. 48: 472-478.

Richardson HL, Parslow PM, Walker AM, Harding R, Horne RSC. (2007) Maturation of the initial ventilatory response to hypoxia in sleeping infants. Journal of Sleep Research. 16: 117-27.

Feltis BN, Wignarajah D, Ward C, Reid DW, Harding R, Walters EH. (2007) Effects of inhaled fluticasone on angiogenesis and vascular endothelial growth factor in asthma. Thorax 62: 314-9

Bubb KJ, Cock ML, Black MJ, Dodic M, Boon WM, Parkington HC, Harding R, Tare M. (2007) Intrauterine growth restriction delays cardiomyocyte maturation and alters coronary artery function in the fetal sheep. Journal of Physiology 578: 871-881.

Crossley KJ, Morley CJ, Allison BJ, Polglase GR, Dargaville PA, Harding R, Hooper SB. (2007) Blood gases and pulmonary blood flow during resuscitation of very preterm lambs treated with antenatal Betamethasone and/or Curosurf: effect of positive end-expiratory pressure. Pediatric Research 62: 37-42.

Maritz GS, Probyn M, DeMatteo R, Snibson K, Harding R. (2007) Lung structure at maturity is influenced by postnatal growth rate but not by moderately preterm birth in sheep. Neonatology 93: 28-35.

Zohdi V, Moritz KM, Bubb KJ, Cock ML, Wreford N, Harding R, Black MJ. (2007) Nephrogenesis and the renal renin-angiotensin system in fetal sheep: effects of intrauterine growth restriction during late gestation. American Journal of Physiology: Regulatory, Integrative and Comparative 293: R1267-73.

Suzuki K, Harding R. (2007) Pulmonary circulation and pulmonary function in neonatal lung hypoplasia: treatment with corticosteroids. Current Pediatric Reviews 3: 264-276.

Thompson B, King G, Harding R. (2007) Commentary on "The role of the large airways on smooth muscle contraction in asthma". J Appl Physiol 103(4):1465.

Sozo F, Hooper SB, Wallace MJ. (2007) Thrombospondin-1 expression and localization in the developing ovine lung. J Physiol 584: 625-635.