Bone is a complex organic-inorganic composite in which mineral nanoparticles (a calcium phosphate phase related to apatite) are bound into the fibrillar extracellular matrix (ECM). Our recent research suggests poly(ADP ribose) (PAR) in the ECM of developing bone may be key in calcification at the mineralisation front. Possible roles for PAR are (i) a nidus or (ii) a source of organic phosphate for formation of calcium phosphate particles; or (iii) binding mature mineral particles to the underlying ECM or (iv) trafficking calcium phosphate-containing matrix vesicles to mineralization sites, or any combination of these. PAR is most commonly associated with the nucleus where it is involved in DNA repair signalling. PAR in the ECM probably arises from cell death, normal in bone development and turnover, and then consequential cell wall rupture. In this project we aim to determine the role extracellular PAR plays in bone developmental calcification. We will start with simple model systems in acellular experiments to establish in what contexts PAR is capable of acting, then move onto in vitro models of developing bone (already developed in collaboration with Dr Roger Brooks, ORU, Addenbrookes Hospital) and finally to ex vivo bone from animal foetal growth plates. This project will use a combination of nuclear magnetic resonance (NMR) spectroscopy and electron microscopy to examine the spatial location of PAR, PAR structure (including polymer length and degree of branching), the nature of mineral being deposited as a function of time and its association with PAR and the organic matrix.
- The effect of particle agglomeration on the formation of a surface-connected compartment induced by hydroxyapatite nanoparticles inhuman monocyte-derived macrophages. K.H. Müller, M. Motskin, A.J. Philpott, A.F. Routh, C.M. Shanahan, M.J. Duer, J.N. Skepper, Biomaterials, 35(3) (2014) 1074-1088.
- Citrate Occurs Widely in Healthy and Pathological Apatitic Biomineral: Mineralized Articular Cartilage, and Intimal Atherosclerotic Plaque and Apatitic Kidney Stones, D.G. Reid, M.J. Duer, G.E. Jackson, R.C. Murray, A.L. Rodgers, C.M. Shanahan, Calcif. Tiss. Int. 93 (2013) 253 – 260.
- The mineralized phase of calcified cartilage: its molecular structure and interface with the organic matrix. M.J. Duer, T. Friščić, R.C. Murray, D.G. Reid, E.R. Wise, Biophys. J. 96 (2009) 3372 – 3378