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Biomechanics and mechanobiology using in silico in situ models of biological tissues

le 3 octobre 2013
13h30

Elisa Budyn, Professeur des Universités

Biological tissues are characterised by a complex and multi-functional architecture. Often highly hierarchical, nature's constructions have optimalproperties to efficiently respond to loading with minimal weight. Additionally living tissues adapt to changing mechanical stimuli that can result from a modified activity or pathology. Biological tissues therefore constantly repair any initiating and progressing micro defect upon its detection and can therefore appose or resorb tissue in an entire region of the organ. Despite the fact that mammal proteins can differ from varying genetic encoding or transcription, cells also answer biological and mechanical cues and produce by exocytosis fibrous proteins forming the extracellular matrix of which the structure will depend on the cell microenvironment. One key to studies in mechanotransduction is the understanding on cells natural in situ micro-environment.
As an example of hierarchical biomaterial, Haversian cortical bone is a hardtissue made of mineralised collagen fibers organised in successive concentric lamellae forming small tubular reinforcements calmed osteons. Under daily exercise, bone undergoes different types of damage that is either easily identifiable by light microscopy such as microcracks or more diffuse and difficult to characterize and visualise. Bone tissue is maintained by cells called osteocytes that are located throughout the microstructure. Osteocytes are mechano-sensitive and sense mechanical stimuli to which they respond by adapting their internal biology to the changes of their mechanical environment. Aging pathologies such as osteoporosis are often following a hormonal decrease where a cell activity imbalance modifies the tissue homeostasis and produces an overly porous structure that tends to contain numerous microcracks. However the effect of a modified mechanical microenvironment on the cells is not precisely quantified. To evaluate the stress field near bone cells, approaches with different level of complexity are possible. Stochastic numerical models offer good approximations of the biomaterial mechanical properties. However visualising the in situ stress field required numerical methods based on explicit morphology that makes it possible to analyse the mechanical effect of microcracks on the cell microenvironment. Dual experimental/numerical top-down investigations through tests conducted in human femoral samples from cadavers of a targeted age group provide relevant information. The local constitutive and fracture models are identified over multiple scales after the balance of the energies at the global
scale.


Type :
Séminaires - conférences
Lieu(x) :
Campus de Cachan
Amphi e-média
Bâtiment Léonard De Vinci de - ENS Cachan
61, avenue du Président Wilson 94230 Cachan
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