Magnetic resonance imaging of human tissue-engineered adipose substitutes

Adipose tissue (AT) substitutes are being developed to answer the strong demand in reconstructive surgery. To facilitate the validation of their functional performance in vivo, and to avoid resorting to excessive number of animals, it is crucial at this stage to develop biomedical imaging methodologies, enabling the follow-up of reconstructed AT substitutes. Until now, biomedical imaging of AT substitutes has scarcely been reported in the literature. Therefore, the optimal parameters enabling good resolution, appropriate contrast, and graft delineation, as well as blood perfusion validation, must be studied and reported. In this study, human adipose substitutes produced from adipose-derived stem/stromal cells using the self-assembly approach of tissue engineering were implanted into athymic mice. The fate of the reconstructed AT substitutes implanted in vivo was successfully followed by magnetic resonance imaging (MRI), which is the imaging modality of choice for visualizing soft ATs. T1-weighted images allowed clear delineation of the grafts, followed by volume integration. The magnetic resonance (MR) signal of reconstructed AT was studied in vitro by proton nuclear magnetic resonance (1H-NMR). This confirmed the presence of a strong triglyceride peak of short longitudinal proton relaxation time (T1) values (200±53 ms) in reconstructed AT substitutes (total T1=813±76 ms), which establishes a clear signal difference between adjacent muscle, connective tissue, and native fat (total T1 ∼300 ms). Graft volume retention was followed up to 6 weeks after implantation, revealing a gradual resorption rate averaging at 44% of initial substitute's volume. In addition, vascular perfusion measured by dynamic contrast-enhanced-MRI confirmed the graft's vascularization postimplantation (14 and 21 days after grafting). Histological analysis of the grafted tissues revealed the persistence of numerous adipocytes without evidence of cysts or tissue necrosis. This study describes the in vivo grafting of human adipose substitutes devoid of exogenous matrix components, and for the first time, the optimal parameters necessary to achieve efficient MRI visualization of grafted tissue-engineered adipose substitutes

Inclusion en contexte de diversité ethnoculturelle : pratiques institutionnelles et points de vue des apprenants sur leurs expériences scolaires

Ce numéro montre que la mise en œuvre d’une éducation inclusive constitue un défi de taille inachevé, tant au plan systémique que du travail sur soi. Cette démarche de changement des pratiques, questionnant de manière continue la responsabilité de l’école à l’égard de la (re)production des inégalités, de l’exclusion et de rapports sociaux inégaux, est parsemée d’obstacles, de situations non prévisibles et d’émotions fortes. Les chercheurs soulignent notamment que de nombreux mécanismes systémiques de la culture scolaire contribuent à reproduire et à réifier des expériences scolaires hiérarchisées et à exacerber des processus de discrimination institutionnelle en défaveur des élèves issus de l’immigration et/ou racisés. Les recherches empiriques présentées mettent également en exergue la pensée déficitaire (deficit thinking) du personnel scolaire vis-à-vis des élèves issus de l’immigration et de leurs parents. Les résultats montrent que des intervenants tendent à utiliser les écarts linguistiques et culturels entre les élèves et le système scolaire pour expliciter l’échec scolaire. Quoi qu’il en soit, les chercheurs ainsi que les acteurs scolaires et les élèves interrogés dans les articles du numéro suggèrent des pistes fécondes pour améliorer l’inclusion en contexte scolaire, soulignant l’importance de donner la voix aux divers acteurs pour tendre vers des transformations institutionnelles. This issue reveals that the implementation of inclusive education is an unfinished challenge, both within the system and for individual self-improvement. This process of changing practices, by continually questioning the school’s responsibility for the (re)production of inequalities, exclusion and unequal social relations, is riddled with obstacles, unpredictable situations and strong emotions. In particular, the researchers point out that many systemic mechanisms of school culture contribute to replicating and reifying hierarchical school experiences and exacerbating processes of institutional discrimination against immigrant background and/or racialized students. The empirical research presented also highlights the deficit thinking of school staff toward immigrant students and their parents. The results show that staff tend to use linguistic and cultural gaps between students and the school system to explain academic failure. Be that as it may, the researchers as well as the school actors and students interviewed in this issue suggest fertile ways to improve inclusion in the school context, stressing the importance of giving voice to the various actors in order to move toward institutional transformation