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There is an urgent need for predictive preclinical models to enhance the success rate of clinical trial outcomes. One of the main reasons for drug attrition is the lack of translational models, methods using human cells are particularly in the spotlight of regulatory bodies as they offer an alternative to in vivo studies and have the potential to improve the translational of preclinical trials. Organs-on-Chips (OoCs) are sensible candidates to reduce the cost and the ethical burden of animal models while accelerating and de-risking drug development. The innovation of such systems is based on both the increased relevance of the cells used and the ability to build precise, yet physiologically relevant, complex architectures. The use of microfluidic technologies with human induced pluripotent stem cells (hiPSCs) opens new routes to create relevant in vitro approaches as they will soon be able to reproduce clinical characteristics of donors or specific populations. The adoption of OoC models by pharmaceutical industries, and in fine by regulatory agencies, still requires: (i) establishing standardized, reproducible, robust, and replicable cell culture protocols with specific validation and characterization criteria, (ii) evidence that the technology predicts human responses, thus allowing to contribute efficiently and reliably to clinical trials success of novel therapeutics, and (iii) evidence that the models refine and reduce animal testing without compromising with the quality and the pertinence of the data generated.

International audience

The detection of abnormal prion protein in the lymphoid tissues of UK patients suggests that after exposure to the agent of variant Creutzfeldt-Jakob disease (vCJD), more than 99% of contaminations may remain clinically silent. These data highlight a risk of secondary transmission through blood transfusion. In parallel to the classical vCJD forms, our experimental models in mice and macaques revealed another group which avoids the current diagnostic criteria, including the absence of abnormal prion protein (PrPres).The main goal of our work was to experimentally assess the risk of blood through retransmission studies and characterization of the abnormal replication of classical and atypical strains examined at peripheral and central levels.We observed a high heterogeneity of the distribution of the abnormal PrP in the lymphoid tissues of vCJD transfused macaques. The global level of contamination in lymphoid tissues seems proportional to the blood infectivity in these animals and to the risk of in vivo transmission of the disease. Regarding atypical forms, despite an absence of replication in lymphoid tissues, these phenotypes are experimentally transmissible. Transmissions to immunodeficient mice reveal that atypical strains are transmissible through peripheral routes in the absence of functional immune system.An alternative to animal testing has been achieved using to "mini-brains" mimicking the complexity of the human nervous system. These organoids cultured in three dimensions are sensitive to at least one prion isolate associated with human sporadic forms. Thus, mini-brains could constitute a new tool for studying prion diseases and improve the characterization of atypical strains.; La détection de la protéine prion anormale dans les tissus lymphoïdes de patients britanniques suggère qu’après exposition à l’agent de la variante de la maladie de Creutzfeldt-Jakob (vMCJ) plus de 99% des contaminations pourraient demeurer cliniquement silencieuses. Ces données soulignent un risque de transmission secondaire par transfusion sanguine ce qui nous a conduit à une étude expérimentale. En parallèle des formes classiques de vMCJ, nos modèles murins et simiens de retransmission ont mis en evidence des phenotypes atypiques. Ces phénotypes échappent actuellement aux critères de diagnostic puisqu’aucune protéine prion anormale (PrPres) n’est détectée.Nos travaux ont eu pour but principal d’évaluer expérimentalement le risque sanguin au travers d’études de retransmission et de caractérisation de la replication des souches classiques et atypiques aux niveaux périphérique et central.Nous observons une très forte hétérogénéité dans la réplication de la PrP anormale dans les différents tissus lymphoïdes des macaques transfusés développant une vMCJ. Le niveau de contamination des tissus lymphoïdes apparait proportionnel à l’infectiosité sanguine de ces animaux et au risque de transmission de la maladie in vivo. Concernant les formes atypiques, la majorité des macaques transfusés n’ont pas de réplication dans les tissus lymphoïdes bien que ces phénotypes soient transmissibles expérimentalement à des modèles murins. Des transmissions à des souris immunodéficientes révèlent que les souches atypiques sont transmissibles par voie périphérique en l’absence d’un système immunitaire fonctionnel.Une alternative à l’expérimentation animale a été réalisée grâce aux « mini-brains » mimant la complexité du cerveau humain. Ces organoïdes cultivés en trois dimensions sont sensibles à au moins un isolat de prion associé aux formes sporadiques humaines. Les mini-brains pourraient ainsi constituer un nouvel outil d’étude des maladies à prions et permettre à termes la caractérisation des souches atypiques.

The detection of abnormal prion protein in the lymphoid tissues of UK patients suggests that after exposure to the agent of variant Creutzfeldt-Jakob disease (vCJD), more than 99% of contaminations may remain clinically silent. These data highlight a risk of secondary transmission through blood transfusion. In parallel to the classical vCJD forms, our experimental models in mice and macaques revealed another group which avoids the current diagnostic criteria, including the absence of abnormal prion protein (PrPres).The main goal of our work was to experimentally assess the risk of blood through retransmission studies and characterization of the abnormal replication of classical and atypical strains examined at peripheral and central levels.We observed a high heterogeneity of the distribution of the abnormal PrP in the lymphoid tissues of vCJD transfused macaques. The global level of contamination in lymphoid tissues seems proportional to the blood infectivity in these animals and to the risk of in vivo transmission of the disease. Regarding atypical forms, despite an absence of replication in lymphoid tissues, these phenotypes are experimentally transmissible. Transmissions to immunodeficient mice reveal that atypical strains are transmissible through peripheral routes in the absence of functional immune system.An alternative to animal testing has been achieved using to "mini-brains" mimicking the complexity of the human nervous system. These organoids cultured in three dimensions are sensitive to at least one prion isolate associated with human sporadic forms. Thus, mini-brains could constitute a new tool for studying prion diseases and improve the characterization of atypical strains., La détection de la protéine prion anormale dans les tissus lymphoïdes de patients britanniques suggère qu’après exposition à l’agent de la variante de la maladie de Creutzfeldt-Jakob (vMCJ) plus de 99% des contaminations pourraient demeurer cliniquement silencieuses. Ces données soulignent un risque de transmission secondaire par transfusion sanguine ce qui nous a conduit à une étude expérimentale. En parallèle des formes classiques de vMCJ, nos modèles murins et simiens de retransmission ont mis en evidence des phenotypes atypiques. Ces phénotypes échappent actuellement aux critères de diagnostic puisqu’aucune protéine prion anormale (PrPres) n’est détectée.Nos travaux ont eu pour but principal d’évaluer expérimentalement le risque sanguin au travers d’études de retransmission et de caractérisation de la replication des souches classiques et atypiques aux niveaux périphérique et central.Nous observons une très forte hétérogénéité dans la réplication de la PrP anormale dans les différents tissus lymphoïdes des macaques transfusés développant une vMCJ. Le niveau de contamination des tissus lymphoïdes apparait proportionnel à l’infectiosité sanguine de ces animaux et au risque de transmission de la maladie in vivo. Concernant les formes atypiques, la majorité des macaques transfusés n’ont pas de réplication dans les tissus lymphoïdes bien que ces phénotypes soient transmissibles expérimentalement à des modèles murins. Des transmissions à des souris immunodéficientes révèlent que les souches atypiques sont transmissibles par voie périphérique en l’absence d’un système immunitaire fonctionnel.Une alternative à l’expérimentation animale a été réalisée grâce aux « mini-brains » mimant la complexité du cerveau humain. Ces organoïdes cultivés en trois dimensions sont sensibles à au moins un isolat de prion associé aux formes sporadiques humaines. Les mini-brains pourraient ainsi constituer un nouvel outil d’étude des maladies à prions et permettre à termes la caractérisation des souches atypiques.

International audience; Human mini-brains (MB) are cerebral organoids that recapitulate in part the complexity of the human brain in a unique three-dimensional in vitro model, yielding discrete brain regions reminiscent of the cerebral cortex. Specific proteins linked to neurodegenerative disorders are physiologically expressed in MBs, such as APP-derived amyloids (Aβ), whose physiological and pathological roles and interactions with other proteins are not well established in humans. Here, we demonstrate that neuroectodermal organoids can be used to study the Aβ accumulation implicated in Alzheimer's disease (AD). To enhance the process of protein secretion and accumulation, we adopted a chemical strategy of induction to modulate post-translational pathways of APP using an Amyloid-β Forty-Two Inducer named Aftin-5. Secreted, soluble Aβ fragment concentrations were analyzed in MB-conditioned media. An increase in the Aβ 42 fragment secretion was observed as was an increased Aβ 42 /Aβ 40 ratio after drug treatment, which is consistent with the pathological-like phenotypes described in vivo in transgenic animal models and in vitro in induced pluripotent stem cell-derived neural cultures obtained from AD patients. Notably in this context we observe time-dependent Aβ accumulation, which differs from protein accumulation occurring after treatment. We show that mini-brains obtained from a non-AD control cell line are responsive to chemical compound induction, producing a shift of physiological Aβ concentrations, suggesting that this model can be used to identify environmental agents that may initiate the cascade of events ultimately leading to sporadic AD. Increases in both Aβ oligomers and their target, the cellular prion protein (PrP C), support the possibility of using MBs to further understand the patho-physiological role that underlies their interaction in a human model. Finally, the potential application of MBs for modeling age-associated phenotypes and the study of neurological disorders is confirmed.