Blood vessels act like tissue engineers, guiding the correct formation of facial cartilage and bone according to a world-first study published in the highly ranked scientific journal PNAS.
Beyond delivering oxygen and nutrients to developing facial structures, a secondary role for blood vessels had not previously been recognized. With further development, the research could have implications for better understanding or even treating craniofacial defects and other health issues involving defective cartilage.
Dr Quenten Schwarz - who lead the study at the Neurovascular Research Laboratory in the Centre for Cancer Biology in South Australia - said the results fundamentally change how he and his colleagues understand development of head and facial structures.
"Our research provides the first evidence that blood vessels are critical to set up the right environment for cartilage growth in the jaw," he said.
"We've discovered that blood vessels secrete factors that control cartilage growth and that this is essential for craniofacial development."
In humans and other mammals, the jaw starts to take shape during embryonic life when a structure known as Meckel's cartilage forms. Later, this cartilage acts as a scaffold around which bone is deposited.
In studies performed in laboratory mice, Dr Schwarz's colleague Dr Sophie Wiszniak found that the correct formation of Meckel's cartilage only took place in mice that had normal blood vessels becoming established in the jaw. She identified that the blood vessels release molecules that guide the cartilage-forming cells to create Meckel's cartilage.
The results were supported by studying anatomical details in X-ray films and tomographical images of people with hemifacial microsomia, a condition in which the lower half of one side of the face is underdeveloped and does not grow normally. In all patients, poor jaw formation coincided with incomplete formation of the mandibular artery, the main blood vessel that runs along and within the jaw.
"We think it's a growth factor or maybe a cytokine that is released from the blood vessels cells that guides normal cartilage and hence jaw formation," said Sophie.
"We hope that through further research we will be able to identify what that factor is. In turn, this may allow us to think about new treatments for disorders where cartilage growth is defective - like some forms of arthritis - or when cartilage is damaged through sporting injuries."
"We'd also like to better understand why some craniofacial abnormalities occur," she said.
Craniofacial abnormalities affect around 1 in 500-750 babies born worldwide, with incidence varying across different geographical regions and ethnic groups.
The study was performed at the Centre for Cancer Biology - an alliance between the University of South Australia and SA Pathology - in collaboration with the Australian Craniofacial Unit and University College London.