Short-term implantation effects of a DCPD-based calcium phosphate cement

International audienceCalcium phosphate cements can be handled in paste form and set in a wet medium after precipitation of calcium phosphate crystals in the implantation site. Depending on the products entering into the chemical reaction leading to the precipitation of calcium phosphates, different phases can be obtained with different mechanical properties, setting times and injectability. We tested a cement composed of a powder, containing-tricalcium phosphate (-TCP) and sodium pyrophosphate mixed with a solution of phosphoric and sulphuric acids. The cement set under a dicalcium phosphate dihydrate (DCPD)-based matrix containing-TCP particles. This was injected with a syringe into a defect drilled in rabbit condyles, the control being an identical defect left empty in the opposite condyle. The condyles were analysed histologically 2, 6 and 18 weeks after implantation. After injection into the bone defect the cement set and formed a porous calcium phosphate structure. Two different calcium phosphate phases with different solubility rates could be identified by scanning electron microscopy (SEM) observation. The less-soluble fragments could be degraded by cell phagocytosis in cell compartments of low pH or integrated in the newly formed bone matrix. The degradation rate of the material was relatively high but compatible with the ingrowth of bone trabeculae within the resorbing material. The ossification process was different from the creeping substitution occurring at the ceramic contact. Bone did not form directly at the cement surface following the differentiation of osteoblasts at the material surface. The trabeculae came to the material surface from the edges of the implantation site. Bone formation in the implantation site was significantly higher than in the control region during the first week of implantation. In conclusion, this material set in situ was well tolerated, inducing a mild foreign-body reaction, which did not impair its replacement by newly formed bone within a few weeks

MMP-2, MMP-9 and their inhibitors TIMP-2 and TIMP-1 production by human monocytes in vitro in the presence of different forms of hydroxyapatite particles.

DOI : 10.1016/j.biomaterials.2003.09.034After calcium-phosphates biomaterials based implantation like hydroxyapatite (HA) coating, particles are released in the periprosthetic tissues. Wear-debris induced fibrous membranes contain macrophage subsets that can produce metalloproteinases (MMPs), which are considered to be key enzymes in extra-cellular matrix turnover. Tissue inhibitors of metalloproteinases (TIMPs) are important regulator of MMPs activity. Interleukin-1 mainly produced by monocytes can also regulate MMPs production. In the present work, we have evaluated the effect of HA particles characteristics (size, shape and sintering temperature) on the MMP-2, -9 and their respective inhibitors TIMP-2, -1 production. Our results demonstrate that sintering temperature (that modify crystal size and surface area) have little effect on MMPs and TIMPs production. Non-phagocytable particles induced more MMP-9, although phagocytable particles induced more IL-1β release. The shape of the particles was the most important factor since needle-shaped particles induced the most significant up-regulated expression of MMPs and IL-1β

Histological study of the interface of calcium phosphate bioceramics and soft tissue in humans.

International audienceThe differentiation of mesenchymal tissue into bone tissue when in contact with different forms of calcium phosphate ceramics implanted within intraskeletal sites in different animals has been reported. The osteogenic effects of calcium phosphate ceramics have been demonstrated in several animal species. Four biopsies from HA-ceramics were obtained, implanted in bony sites of humans, which failed to be osteointegrated for more than one year. Two kinds of ceramics with different characteristics were studied. A histological analysis of the soft tissue/ceramic interface was carried out. The ceramics were embedded in an identical connective tissue. The interface with the ceramic consisted of collagen bundles parallel to the ceramic surface. Certain ceramics showed at their surface, a tissue matrix with the staining abilityof bone, although no evidence of osteogenic cells or osteoid was foundat the matrix surface.The pores were filled with a hyaline tissue containing a few cells dispersed within the hyaline matrix. Although this study could not be performed under the same conditions as in animals, no bone formation was induced by these ceramics implanted in the connective tissue suggesting that, in humans the osteogenic effect of this material is inconstant, or related to specific characteristics

Les substituts du tissu osseux

National audienc

Devenir à deux ans de l'interface os-hydroxyapatite. Etude histologique de 10 hémiarthroplasties fémorales.

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Projection d'hydroxyapatite sur prothèses articulaires: progrès ou illusion?

SCOPUS: re.jinfo:eu-repo/semantics/publishe

Biotechnology, material sciences and bone repair

International audienceIt is very likely that the need for bone substitutes will increase in the next decade. The present substitutes are generally bioactive and osteoconductive. Glassy or ceramic materials have been used up to now to act as a guide for bone healing tissue and were shown to admit bone apposition at their surface, probably due to the epitaxial growth of carbonated apatite crystals on it. Different forms of bone substitutes have been developed which do not show exactly the same properties. The reaction of bone tissue against bioactive material debris show major differences from that of polymers or metals. In vitro models were developed to study the interface between bone cells and extracellular matrix, and the surface of bioactive material. Biotechnology makes available some morphgenetic proteins or growth factors in large quantities for combination with osteoconductive material which then can become osteoinductive. Bioartificial bone tissue constituted by a primary osteogenetic cell line immobilised at the surface of osteoconductive materials maade it possible to obtain osteogenic materials. The ideal bone material is still to be engineered. The combination of material sciences and and molecular biology will help to optimise the next generation of material surfaces