Etude des propriétés ostéogéniques de céramiques phosphocalciques

L'autogreffe osseuse est considérée comme le modèle de référence dans la reconstruction de défauts osseux, mais présente des inconvénients. Les substituts osseux synthétiques constituent une alternative d'avenir à l autogreffe osseuse. Des céramiques macro et micro poreuses ont été préparé à partir de poudres amorphes de phosphate de calcium. Un modèle animal permettant d étudier l'ostéogénicité de céramiques et d'os autologue sans la contribution de l'ostéoconduction a été conçu et validé. L'ostéogénicité de ces céramiques a été comparé à celle de l'autogreffe osseuse après implantation dans les muscles et les condyles fémoraux de chèvre. Nous avons observé une néoformation osseuse au contact de céramiques microporeuses frittées à 1050 et 1125C après 6 et 12 semaines d'implantation. Par contre, les céramiques présentant une surface dense frittée à 1200C ne contenait pas de tissu osseux. Nous avons également noté une forte résorption de l autogreffe osseuse sans néoformation à la fois en site intra musculaire et fémoral. Le rôle de l inflammation dans les propriétés ostéogéniques de ces céramiques a ensuite été étudié. L implantation de microparticules dans les muscles de rats a donné lieu à une réaction inflammatoire. La culture de macrophages en présence des microparticules a induit une augmentation de la sécrétion de cytokines inflammatoires (IL-6 et TNF-a). Les marqueurs ostéogéniques exprimés par des cellules ostéoblaste ont été respectivement augmentés en présence d IL-6 et inhibés avec TNF-a. L ensemble de ce travail a permis d étudier les propriétés ostéogéniques de substituts osseux à base de céramiques phosphocalciques en fonction de leur microstructure.Autologous bone graft is considered as the gold standard for filling bone defects, however it presents some disadvantages. Synthetic bone substitutes represent alternatives to autologous bone autograft. Macro and microporous ceramics were prepared using calcium amorphous phosphate powders. An animal model to study osteogenicity was designed and validated. The osteogenicity of different ceramics was compared with bone autograft after implantation in the muscles and the femoral condyles of goat. We observed newly formed bone in contact with microporous ceramics sintered at 1050 and 1125C after 6 and 12 weeks. On the other hand, ceramics having a dense surface sintered at 1200C did not contain bone tissue. We also noted an important resorption of bone autograft without neoformation both in muscle and and femoral sites. The role of inflammation on the osteogenic properties of this ceramics was then studied. The implanatation of microparticles in rats muscles induced an inflammatory reaction. The culture of macrophages in the presence of these microparticles increased the secretion of inflammatory cytokines (IL-6 and TNF-a). Osteogenic markers expressed by osteoblast cells were respectively increased in the presence of IL-6 and inhibited with TNF-a. The overall work demonstrated that the osteogenic properties of calcium phosphate ceramics strongly depend on their microstructure.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

Vertebroplasty using bisphosphonate-loaded calcium phosphate cement in a standardized vertebral body bone defect in an osteoporotic sheep model

International audienceIn the context of bone regeneration in an osteoporotic environment, the present study describes the development of an approach based on the use of calcium phosphate (CaP) bone substitutes that can promote new bone formation and locally deliver in situ bisphosphonate (BP) directly at the implantation site. The formulation of a CaP material has been optimized by designing an injectable apatitic cement that (i) hardens in situ despite the presence of BP and (ii) provides immediate mechanical properties adapted to clinical applications in an osteoporotic environment. We developed a large animal model for simulating lumbar vertebroplasty through a two-level lateral corpectomy on L3 and L4 vertebrae presenting a standardized osteopenic bone defect that was filled with cements. Both 2-D and 3-D analysis of microarchitec-tural parameters demonstrated that implantation of BP-loaded cement in such vertebral defects positively influenced the microarchitecture of the adjacent trabecular bone. This biological effect was dependent on the distance from the implant, emphasizing the in situ effect of the BP and its release from the cement. As a drug device combination, this BP-containing apatitic cement shows good promise as a local approach for the prevention of osteoporotic vertebral fractures through percutaneous vertebroplasty procedures

Evaluation of a hydrogel membrane on bone regeneration in furcation periodontal defects in dogs

The study biomaterials were kindly provided by Biomatlante, Vigneux de Bretagne, France.International audienceThe aim of the study was to evaluate bone regeneration using a canine model with surgically created periodontal defects filled for 12 weeks using a stratified biomaterial consisting in a biphasic calcium phosphate (BCP) covered with a crosslinking hydrogel acting as polymer membrane of silated hydroxypropyl methylcellulose (Si-HPMC) as the tested new concept. Bilateral, critical-sized, defects were surgically created at the mandibular premolar teeth of six adult beagle dogs. The defects were randomly allocated and: (i) left empty for spontaneous healing or filled with: (ii) BCP and a collagen membrane; (iii) BCP and hydrogel Si-HPMC membrane. At 12 weeks, the experimental conditions resulted in significantly enhanced bone regeneration in the test BCP/Si-HPMC group. Within the limits of this study, we suggest that the hydrogel Si-HPMC may act as an occlusive barrier to protect bone area from soft connective tissue invasion and then effectively contribute to enhance bone regeneration

Sequences of rabbit primer pairs, gene bank accession numbers used for real-time PCR analysis and size of the PCR products.

<p>Sequences of rabbit primer pairs, gene bank accession numbers used for real-time PCR analysis and size of the PCR products.</p

Chondrogenic potential of differentially preconditioned rabbit ASC (rASC).

<p><b>A)</b> rASC were cultured under normoxic conditions (21% O₂) in control medium (NCT) and chondrogenic medium (NCH) or under hypoxic conditions (5% O₂) in chondrogenic medium (HCH). The expression of transcripts encoding type II collagen (<i>col2a1</i>) and aggrecan (<i>acan</i>) was measured by real-time PCR. The results are expressed as relative expression levels. ND: not detected. # <i>p</i><0.05 compared with NCT; * <i>p</i><0.05 compared with NCH. <b>B)</b> rASC were cultured in NCT (a, b, c, d), NCH (e, f, g, h), or HCH (i, j, k, l) and implanted with the Si-HPMC hydrogel in rabbit osteochondral defects. Rabbit nasal chondrocytes (RNCs) incorporated into the Si-HPMC hydrogel were used as a control (m, n, o, p). After 18 weeks of implantation, the defects were macroscopically observed [gross appearance (a, e, i, m)], histologically stained using Movat's pentachrome (b, f, j, n) and alcian blue (c, g, k, o) and immunostained for type II collagen (d, h, l, p). a, e, i, m: bar indicates 1 mm. b–d; f–h, j–l, n–p: bar indicates 100 µm. <b>C)</b> A semi-quantitative analysis of the regenerated tissue was performed using O′Driscoll's repair score as described in the “Materials and Methods” section. The results are expressed as a mean O′Driscoll score.</p

Schematic overview of <i>in vivo</i> experimental design.

<p>A) Schematic overview of the chondrogenic potential of differentially preconditioned rabbit adipose stromal cells (rASC). rASC were isolated and cultured under normoxic conditions (21% O₂) in control medium or chondrogenic medium or under hypoxic conditions (5% O₂) in chondrogenic medium. As a positive control, rabbit nasal chondrocytes (RNC) were used. Preconditioned rASC and RNC were finally associated with Si-HPMC hydrogel and implanted in rabbit articular cartilage defects for 18 weeks. B) Schematic overview of the chondrogenic potential of differentially preconditioned human adipose stromal cells (hASC). hASC were isolated and cultured under normoxic conditions (21% O₂) in control medium or chondrogenic medium or under hypoxic conditions (5% O₂) in chondrogenic medium. As a positive control, horse nasal chondrocytes (HoNC) were used. Preconditioned hASC and HoNC were finally associated with Si-HPMC hydrogel and implanted in nude mice subcutis for 5 weeks.</p

Sequences of human primer pairs, gene bank accession numbers used for real-time PCR analysis and size of the PCR products.

<p>Sequences of human primer pairs, gene bank accession numbers used for real-time PCR analysis and size of the PCR products.</p

Chondrogenic potential of differentially preconditioned human ASC (hASC).

<p><b>A)</b> hASC were cultured under normoxic conditions (21% O₂) in control medium (NCT) and chondrogenic medium (NCH) or under hypoxic conditions (5% O₂) in chondrogenic medium (HCH). The expression of transcripts encoding type II collagen (<i>COL2A1</i>) and aggrecan (<i>ACAN</i>) was measured using real-time PCR. The results are expressed as relative expression levels. ND: not detected * <i>p</i><0.05 compared with NCH. <b>B)</b> hASC were cultured in NCT (a, b), NCH (c, d) or HCH (e, f) and implanted with the Si-HPMC hydrogel into subcutaneous pockets of nude mice. Horse nasal chondrocytes (HoNCs) incorporated into the Si-HPMC hydrogel were used as a control (g, h). After five weeks, the samples were harvested, histologically stained using alcian blue (a, c, e, g) and immunostained for type II collagen (b, d, f, h). Bar indicates 20 µm.</p