**Acknowledgements**

A. Mobasheri acknowledges the financial support of The Wellcome Trust, the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) (grant number: Mobasheri.A.28102007), the Biotechnology and Biological Sciences Research Council (BBSRC) (grants BBSRC/S/M/2006/ 13141 and BB/G018030/1), the Engineering and Physical Sciences Research Council (EPSRC), Arthritis Research UK (ARUK) and the European Commission Framework 7 (EU FP7). M. Lewis acknowledges the financial support of the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), the Engineering and Physical Sciences Research Council (EPSRC), Arthritis Research UK (ARUK), The Wellcome Trust, the National Centre for Sport and Exercise Medicine (NCSEM).
