US researchers have identified a second ingredient in cigarette smoke that delays bone healing after fractures.
A team of
experts at the University of Rochester Medical Center had earlier shown in a
2005 study that nicotine delays bone growth by influencing gene expression in
the two-step bone healing processfirst, when stem cells become cartilage;
secondly, when cartilage matures into bone.
current study, it has been found that another ingredient in cigarette smoke
called the polyaromatic hydrocarbon benzo(a)pyrene (BaP) also slows bone
healing, though in a different way.
evidence that smoking delays skeletal healing by as much as 60 per cent
following fractures, and thereby increases the likelihood of re-injury, chronic
pain, and disability.
experts say that the obvious solution for the smokers is to kick the butt when
they get hurt, studies have shown that only 15 per cent can do so.
results provide the first evidence that BaP prevents stem cells from becoming
cartilage cells as part of healing," said Dr. Regis J. O'Keefe, chair of the
Department of Orthopaedics and Rehabilitation at the Medical Center and a study
findings extend our understanding of the impact of cigarette smoke on a process
that is critical to fracture repair. Perhaps down the road we will be able to
speed bone healing among smokers in more than one way," he added.
researcher said that during the study, polymerase chain reaction (PCR), a tech
technique that measures gene expression levels, revealed the genetic changes
caused by exposure to BaP in mouse stem cells.
He said that
the PCR results showed that BaP in cigarette smoke interferes with the
expression of a gene called SOX-9, which is required for the transition of stem
cells into cartilage cells. Besides BaP was also found to effect the production
of type II collagen gene, a fibrous protein framework for cartilage.
reduces the rate at which the two sides of a fracture come together. We believe
this new research will establish for the first time the mechanisms by which
polyaromatic hydrocarbons interfere with the healing process," said Dr.
Michael Zuscik, associate professor in the Department of Orthopaedics and
Rehabilitation at the Medical Center.
The new finding was presented at the annual
meeting of the Orthopaedic Research Society in San Francisco.