Our bones are alive: they can repair themselves when damaged and they can adjust to the amount of stress and strain that we put them through, becoming thicker and stronger if we exercise regularly, and weak and porous if we don’t. We know that our bones can do these things: what we don’t know is how. But scientists at Trinity College Dublin may have found the answer.
Bone is full of living cells, connected to each other in networks rather like neurons in the brain. Professor of Materials Engineering, Professor David Taylor and colleagues at the Trinity Centre for Bioengineering are conducting research as to how this network reacts to mechanical strain and damage. In a project funded by Science Foundation Ireland, they have discovered that the links between cells – known as cellular processes – can be broken where they pass across tiny, microscopic cracks in the bone matrix. By culturing bone cells artificially, they showed that when these cellular processes are cut, they release a substance known as RANKL. This is the cell’s way of telling its neighbours that it has been damaged. When RANKL is detected by other cells, a repair process is begun which removes the region of bone containing the crack and replaces it with new bone. In this way, they believe, bone is able to maintain itself against daily wear and tear, and to detect changes in its stress environment.
This project, called the ‘Living Bone Project’, was funded with a budget of €266,000 under SFI’s Research Frontiers Programme which supports cutting edge scientific research on a wide range of topics. Teamwork is the key to making progress is this multidisciplinary field, which requires a wide range of expertise covering biology and medicine as well as engineering and materials science. The team led by Professor Taylor includes Professor Clive Lee and Dr Garry Duffy, experts in cell biology and anatomy at the Royal College of Surgeons in Ireland, and Dermot Geraghty, an expert in control engineering who is helping the team understand feedback systems. Two PhD students – Pietro Tisbo and Lauren Mulcahy – are employed directly on the project, whilst a third researcher – Clodagh Dooley – has joined the team from Trinity’s Centre for Microscopy and Analysis, providing valuable expertise in microscopic techniques.
Professor Taylor described this work as part of a recent public lecture, titled ‘An Exposition of the Art and Science of Fracture (With Demonstrations) Including Metal Fatigue and Broken Bones’. The lecture was on the occasion of Professor Taylor’s inaugural lecture as Professor of Materials Engineering at the School of Engineering, and his election to membership of the prestigious Royal Irish Academy. In the lecture, Professor Taylor used demonstrations to illustrate that many materials frequently fail by cracking, that they can develop toughness by resisting the growth of cracks and that, in the case of living materials, they can prevent fracture by monitoring and repairing themselves continuously. Using examples of his work stretching over 30 years, he showed how a career spent breaking things can lead to fascinating insights into the materials and structures around us and useful outcomes to help prevent failure in everything from aircraft to human bones.
Other examples of Professor Taylor’s work include developments in the theory of fracture mechanics, which is the science of how things break. He pioneered new methods of predicting failure in engineering structures which have been incorporated into commercial software now being used all over the world by companies manufacturing cars, aircraft components and bridges among other structures. In particular, this software can help to prevent metal fatigue, which is the most common type of failure in engineering components and the cause of many terrible aircraft accidents and bridge failures among others. When failures do happen, Professor Taylor assists the courts by carrying out forensic analysis to determine who was responsible, helping to prevent similar problems in the future.
He has also studied the failure of medical devices such artificial hip joints, knee joints and bone fracture plates. This work lead to the development of a new type of glue for the attachment of artificial joints and has influenced the choice of materials and techniques used in operating theatres in Ireland and abroad.
Other current work includes a project on osteoporosis, in conjunction with Professor Bernard Walsh and colleagues at St James’s Hospital and Tallaght’s Adelaide and Meath, incorporating the National Children’s Hospital and the Royal College of Surgeons in Ireland. This project aims to understand why our bones become weak and brittle in old age, to improve the clinical methods used to monitor patients with osteoporosis and to understand the effects of the various drugs which are used to treat this condition.
Extracts from a public lecture by Professor David Taylor on the occasion of his inaugural lecture as Professor of Materials Engineering. Professor David Taylor was promoted to the personal Chair of Materials Engineering in 2008.