Inhibition of fracture healing in smokers: cellular and molecular aspects

Tobacco smoking has a detrimental impact on fracture healing, and has been implicated inthe non-union and delayed union of bone. Whilst previous studies have concentrated on theclinical manifestations of smoking, little work has been undertaken biochemically.Aim: To study the effects of smoking at the cellular and molecular level in vitro.Methods: Cell-culture assay: Fracture haematomas were collected from anaesthetisedpatients (n=16; 5 smokers vs. 11 non-smokers) that had sustained a tibial fracture. Thesemisolid material was explanted into tissue culture flasks and allowed to clot. Completeculture media was introduced into the flasks, which were placed in an incubator (37°C;humidified CO2). Cultured cells were characterised via immunofluorescence andimmunophenotyping using known mesenchymal stem cell antibody markers (CD29, CD44,and CD166); CD34 was applied as a negative control. A flow cytometer was used to countcell populations at the end of each passage. ELISA assays: Serum and cells obtained fromthe fracture haematomas were subjected to an ELISA to compare the amount of VEGF-A(serum) and IL-6 (cells) between smokers and non-smokers.Results: Cell counting showed a reduction in the rate of proliferation of cells in smokers over3 passages (~-200%). The VEGF-A (serum) and IL-6 (cells) ELISA revealed a reduction ofthese acute phase proteins in patients who were smokers (VEGF-A ~-10%; IL-6 ~-15%).Conclusion: Fracture haematoma mesenchymal stem cells proliferate at a slower rate invitro in smokers than non-smokers. The amounts of VEGF-A and IL-6 are reduced insmokers’ serum and cell cytoplasm respectively.