Approche multimodale d’analyse des adaptations osseuses ex-vivo

Abstract

Ex vivo culture is an experimental method that consists to keep biological tissues alive outside their original physiological environment. Samples are taken from donors and placed in a bioreactor that aims to reproduce an environment similar to that of the living organism. The advantage of this experimental method is to allow tests and measurements that would otherwise be impossible to carry out directly on living subjects for ethical or technical reasons. Ex vivo culture is particularly used to study changes in the trabecular bone in response to the application of mechanical loading. Unlike in-vivo experiments, which are carried out on live animal models, ex-vivo culture allows a deeper study of the tissue by controlling the environment in which it evolves. However, the characterization of changes has been identified as an area to be improved in the implementation of this type of experimentation. The combination of multiple measurement methods to document changes during the culture period is rarely used, despite the fact that it is recognized important in the literature to consider several factors to assess bone quality. The objective of this thesis is to validate the hypothesis that the monitoring of bone adaptations from ex vivo culture can be improved by combining multiple measurement modalities. To do this, an ex-vivo culture model was used to generate bone adaptations by applying mechanical loading to trabecular bone. Due to their non-destructive nature and high resolution, digital image correlation and X-ray micro-tomography have been identified as potential measurement methods to characterize the evolution of samples during the culture period. Prior to their use, a series of experiments were carried out to evaluate their ability to detect changes in bone tissue in an ex vivo culture context. The results showed the possibility of using X-ray micro-tomography to detect, after a 14-day culture period, bone changes above the sensitivity threshold of the method. As for digital image correlation, the results demonstrated the possibility of using this measurement method without the application of a stochastic paint pattern detrimental to the integrity of the samples, and to characterize the mechanical behaviour of bone samples in an ex vivo culture context. Once the characterization methods were implemented, a multimodal analysis of bone adaptations from an ex vivo culture was performed. The results showed that the complementarity of changes measured by X-ray icrotomography and digital image correlation, as well as the consideration of local rather than global adaptations, improve the interpretation of bone adaptations. Ultimately, this project contributed to the advancement of knowledge regarding the characterization of bone adaptations in ex vivo culture. Its realization proved possible to improve the monitoring of bone samples evolution by combining multiple measurement methods. The use of a multimodal approach will have the effect of expanding the scope of application of ex-vivo culture and thus advancing knowledge about bone tissue behaviour. Ex-vivo culture may eventually be used to study many phenomena related to the bone remodeling process including growth, resorption, osteoporosis, bone reinforcement due to external load application, fracture incidence, osseointegration, etc.

Date	20 Feb 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Yvan Petit (Supervisor) & Heidi-Lynn Ploeg (Co-supervisor)