RESUMO
Recombinant human bone morphogenetic protein-2 with an additional s-tag domain (s-tag-BMP-2) synthesized in E. coli is characterized by higher solubility and activity than the protein without additional s-tag domain, which increases the yield during purification and simplifies protein introduction into the osteoplastic materials. The high osteoinductivity of the demineralized bone matrix with s-tag-BMP-2 was shown on the model of regeneration of cranial defects of a critical size in mice and on the model of implantation of porous titanium matrix into defects of femoral and tibial bones in rabbits.
Assuntos
Proteína Morfogenética Óssea 2/farmacologia , Regeneração Óssea/efeitos dos fármacos , Fêmur/efeitos dos fármacos , Proteínas Recombinantes de Fusão/farmacologia , Crânio/efeitos dos fármacos , Tíbia/efeitos dos fármacos , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Proteína Morfogenética Óssea 2/biossíntese , Proteína Morfogenética Óssea 2/genética , Clonagem Molecular , Escherichia coli/genética , Escherichia coli/metabolismo , Fêmur/lesões , Expressão Gênica , Implantes Experimentais , Masculino , Camundongos , Camundongos Endogâmicos ICR , Coelhos , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , Crânio/lesões , Tíbia/lesões , Engenharia Tecidual , Alicerces Teciduais , Titânio/química , Titânio/farmacologiaRESUMO
The porous titanium implants were introduced into the condyles of tibias and femurs of sheep. New bone tissue fills the pore, and the porous titanium-new bone tissue composite is formed. The duration of composite formation was 4, 8, 24 and 52 weeks. The formed composites were extracted from the bone and subjected to a compression test. The Young's modulus was calculated using the measured stress-strain curve. The time dependence of the Young's modulus of the composite was obtained. After 4 weeks the new bone tissue that filled the pores does not affect the elastic properties of implants. After 24 and 52 weeks the Young's modulus increases by 21-34% and 62-136%, respectively. The numerical calculations of the elasticity of porous titanium-new bone tissue composite were conducted using a simple polydisperse model that is based on the consideration of heterogeneous structure as a continuous medium with spherical inclusions of different sizes. The kinetics of the change in the elasticity of the new bone tissue is presented via the intermediate characteristics, namely the relative ultimate tensile strength or proportion of mature bone tissue in the bone tissue. The calculated and experimentally measured values of the Young's modulus of the composite are in good agreement after 8 weeks of composite formation. The properties of the porous titanium-new bone tissue composites can only be predicted when data on the properties of new bone tissue are available after 8 weeks of contact between the implant and the native bone.
Assuntos
Osso e Ossos , Nanocompostos/química , Titânio/química , Animais , Módulo de Elasticidade , Teste de Materiais , Porosidade , OvinosRESUMO
A porous material has been produced by pressing spongy titanium granules with subsequent vacuum sintering. The material with porosity of more than 30% has an open system of interconnecting pores. The Young's modulus and 0.2% proof strength have been measured for the samples having 20-55% porosity. If the porosity is between 30 and 45%, the mechanical properties are determined by irregular shape of pores, which is due to spongy titanium granules. The experiment in vivo was performed on adult rabbits. Before surgery the implants were saturated with adherent autologous bone marrow cells. The implants were introduced into the defects formed in the condyles of tibias and femurs. Investigations of osseointegration of implants having 40% porosity showed that the whole system of pores was filled with mature bone tissue in 16 weeks after surgery. Neogenic bone tissue has an uneven surface formed by lacunas and craters indicative of active resorption and subsequent rearrangement (SEM examination). The bone tissue is pierced by neoformed vessels. Irregular-shaped pores with tortuous walls and numerous lateral channels going through the granules provide necessary conditions for the formation of functional bone tissue in the implant volume and the periimplant region.
Assuntos
Substitutos Ósseos/síntese química , Osseointegração/fisiologia , Osteoblastos/citologia , Osteoblastos/fisiologia , Osteogênese/fisiologia , Próteses e Implantes , Titânio/química , Animais , Força Compressiva , Módulo de Elasticidade , Análise de Falha de Equipamento , Dureza , Teste de Materiais , Porosidade , Desenho de Prótese , Coelhos , Resistência à TraçãoRESUMO
The review describes the mechanisms of hormonal, autocrine, paracrine and intracellular regulation in osteogenic differentiation of mesenchymal stem cells, the role of negative feedbacks in this process.
Assuntos
Diferenciação Celular , Células-Tronco Mesenquimais/fisiologia , Osteogênese/genética , Animais , Células da Medula Óssea/citologia , Fatores de Crescimento de Fibroblastos/genética , Fatores de Crescimento de Fibroblastos/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Células-Tronco Mesenquimais/citologia , Microscopia Eletrônica de Transmissão e Varredura , Osteoblastos/citologia , Osteoblastos/metabolismo , Osteogênese/fisiologia , Via de Sinalização Wnt/genéticaRESUMO
We studied changes of microarchitectonics of lymph nodes in mature rabbits in response to introduction of bioimplants based on porous titanium with carbon-containing nanocoating or nanocoating with hydroxyapatite embedded into pores. Moderate local reactivity of the lymphoid system was observed in animals with implants coated with carbon-containing films within 30 days after surgery. In animals with nanocoated implants containing hydroxyapatite, the immune response was more pronounced. Introduction of implants led to activation of cellular and humoral mechanisms of immunity in animals of both groups.
