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Biochemists add important clues in respiratory research
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EVERY year, all around the world, thousands of premature babies die within hours of birth, due to their inability to fill, and keep filling, their lungs with fresh oxygen.
Now, a team of Murdoch University biochemists, led by Associate Professor Max Cake, has discovered some potentially life-saving clues to the condition known as Neonatal Respiratory Distress Syndrome.
The team's research may help infants 'switch on' their lungs, hastening development of these vital organs and enabling them to produce a natural supply of a crucial material — pulmonary surfactant.
The lungs are one of the body's last organs to develop fully, normally only reaching full maturity by about the 37th week of the 40-week gestation period. Babies born prematurely, before this critical period, frequently have difficulty breathing due to their inability to retain some of their previous breath in their lungs  which is essential to keep their lungs partially expanded.
Keeping the lungs partially expanded relies on the presence of pulmonary surfactant, a lipid-containing material which is secreted by specialised cells that line the alveoli. The alveoli are the tiny air sacs within the lung which fill with air with each breath. The transfer of oxygen and carbon dioxide between the lungs and blood circulatory system takes place across the walls of the alveoli.
The surface of the lungs is bathed with a continuous layer of liquid which, through the forces of surface tension, contributes to the contraction of the lungs when one's body exhales a breath. This surface tension is so strong that the lungs would totally collapse at the end of each breath if pulmonary surfactant was not present.
Surfactant forms a thin film at the air-liquid interface within the alveoli and, acting not unlike a detergent, reduces the surface tension. When an infant exhales, the surfactant helps to bring the lungs' contraction to a halt, before they completely collapse and empty of air. Thus, surfactant is of critical importance in the continuous inflation and deflation of the lung.
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Unfortunately, surfactant is not produced in the lungs until very late in the gestation period and hence many premature babies are born before their lungs have the ability to produce this essential, life-saving lipid material.
For many years scientists have been trying to discover a means of overcoming the often-fatal consequences of Neonatal Respiratory Distress Syndrome.
Dr Cake's team which, in recent years, has included PhD research students Namita Sen, Nithiananthan Asokananthan, Mimi Tajbakhsh and Brian Poleykett, has been focussing its research on the role of various peptides, produced within the lung, which stimulate the secretion of the surfactant lipids.
Dr Cake said surfactant is known to be produced by specialised cells within the lung called type II pneumocytes.
"These type II pneumocytes are cells that acquire the ability to synthesise and secrete surfactants into the alveoli quite late in gestation, which is why when premature babies are born they are lacking an ability to produce it."
Dr Cake said scientists have been able to produce a synthetic surfactant which can be infused into the lung of an infant suffering from Neonatal Respiratory Distress Syndrome.
"But there is still ongoing interest in what is the normal process that actually controls the maturation of the lung and we've been particularly interested in the role of small peptides, called growth factors," he said.
"There are a number of different peptides that are produced within the body that seem to have an effect on the lung.
"One that we've done quite a bit of research on is gastrin-releasing peptide, which we found brings about a very significant increase in the rate of secretion of surfactant from the type II pneumocytes."
Dr Cake said the potentially life-saving discoveries had been made in the Murdoch laboratories, where experiments have been conducted in tissue culture, using foetal rat cells as a model.
"The intention is that once we've fully understood the system we will provide the information to medical scientists working with premature babies in some of the nation's leading paediatric research facilities," he said.
Dr Cake said he believes that, if premature babies with Neonatal Respiratory Distress Syndrome were given gastrin-releasing peptide, along with the synthetic surfactant, it would facilitate the continuing development of the lung. The infant would then have its own lungs 'switched on', hastening the natural development of its lungs and enabling them to produce their own natural supply of surfactant.
Dr Cake said it was now time to have discussions with staff at King Edward Memorial Hospital in Perth to ascertain whether the findings of his research team are applicable to the human condition.
"If they are, then the KEMH staff can start looking at the possibility of applying it to their treatment procedures," he said.
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