BONE IMPLANTS – OLD PROBLEMS AND NEW PERSPECTIVEES

1. BONE IMPLANTS – OLD PROBLEMS AND NEW PERSPECTIVEES Radostina Alexandrova, PhD Institute of Experimental Morphology, Pathology AND Anthropology with Museum, Bulgarian Academy of Sciences

2. Organic matrix Collagen type I fibers (95%) Proteoglicans and numerous non-collagenous proteins (5%)

4. CELLS

5. Cytokines Hormones (parathyroid hormone (PTH) and 1α, 25(OH)2 vitamin D3) Growth factors (IGFs, PDGF, FGFs, VEGFs, tTGFs and bone morphogenic proteins (BMPs)

6. F U N C T I O N • Involved in body protection, support and motion; • It is a protection and production site for specialized tissues (bone marrow, heart, lungs) • Supports structurally the mechanical action of soft tissues, like the construction of muscles or extension of lungs. • It is a mineral reservoir whereby endocrine system regulate the level of calcium and phosphate ions in the circulating body fluids

7. Mechanical properties

8. Diseases Trauma Congenitive disorders Cancer, ostoeporosis, Rheumatoid arthritis, etc Fractura, Burning BONE DEFFECTS

9. Techniques used to repair damaged bones Autografts Allografts • Limited availability • Foreign body reactions • Infections Limited amount Artificial materials

10. B I O M A T E R I A L S

11. DEFINITION OF BIOMATERIALS • A biomaterial can be defined as any material used to make devices to replace a part or a functionof the body in a safe, reliable, economic, and physiologically acceptable manner. A variety of devices and materials isused in the treatment of disease or injury.

15. Orthopedic implants may fail owing to different reasons: • poor osseointegration at the tissue-implant interface • generation of wear debris • stress and imbalance between implant and surrounding tissues • infections The average lifetime of the current bone biomaterials is less than 15 years

16. TISSUE ENGINEERING STEM CELLS SCAFFOLD

17. Osteogenesis occurs by seeding the scaffolds before implantation with cells that will establish new centers for bone formation, such as osteoblasts and mesenchymal cells that have the potential to commit to an osteoblastic lineage Genetically transduced cells that express osteoinductive factors can also be used

18. Scaffolds for bone regeneration should meet certain criteria to serve this function: • Mechanical properties - • Biocompatibility and biodegradability • Osteoconductivity • Dlivery vehicles for cytokines such as BMPs, IGFs and TGFs – similar to those of the bone repair site • at a rate commensurate with remodeling. the phenomenon of new bone formation on the surfaces of biomaterial that transform recruited precursor cells from the host into bone matrix producing cells, thus providing osteoinduction.

20. Cytokines Growth factors

24. 1.Activation: preosteoclasts are stimulated and differentiate under the influence of cytokines and growth factors into mature active osteoclasts 2. Resorption: osteoclasts digest mineral matrix (old bone) 3. Reversal: end of resorption 4. Formation: osteoblasts synthesize new bone matrix 5. Quiescence: osteoblasts become resting bone lining cells on the newly formed bone surface

25. The complexity of architecture and the variability of properties of bone tissue (e.g. porosity, pore size, mechanical properties, mineralization of mineral density, cell type and cytokine graduated features) • Differences in age, nutritional state, activity (mechanical loading and disease status of individuals a major challenge in fabricating scaffolds and engineering bone tissues that will meet the needs of specific repair sites in specific patients

27. Acknowledgement: This study was supported by Grant DTK-02-70/2009, National Science Fund, Bulgaria

28. THANK YOU!!!