Matrices 3D de collagène en modèle cellulaire et acellulaire pour l'étude de protéines > : le cas de DMP1
2012
The bone is an extremely complex structure, which closely associates cells, extracellular matrix, with collagen and, and an apatite mineral network. Although bone is one of the most studied living materials, the exact roles of non collagenous proteins as nucleator or inhibitor of the mineral phase are still controversial. The aims of the present study were to validate two different matrices, the one at 40 mg/mL mimicking osteoid tissue, the other at 250 mg/mL mimicking compact bone, used to better understand the role of “mineralizing” proteins, and in particularly DMP1 (Dentin Matrix Phosphoprotein-1), an acidic, highly phosphorylated, noncollagenous protein secreted during dentin and bone formation. The 60 day in vitro study showed that primary human osteoblasts seeded on dense 3D collagen matrices display features that are characteristic of active bone cells in vivo (adhesion, proliferation, morphology, mineralization, protein and gene expression). Then, the evolutionary analysis of DMP1 was useful for detecting new, potentially important motifs conserved during 220 millions years; some motifs could play a role in the mineralization process, due to the presence of numerous acidic residues. We have tested the possible function of these highly conserved motifs using a recombinant DMP1 (rDMP1), designed in the region which included the two collagen binding sites and the highly conserved acidic motifs. DMP1 was shown to play a role in the mineralization, as nucleating the mineral phase inside the collagen fibrils and inhibiting the ectopic mineralization. Our model provided similar results to the in vivo conditions, in term of morphology and nature of the mineral phase
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