A sinalização da resposta Imune Inata exerce um papel fundamental na eliminação de patógenos bem como no recrutamento de progenitoras para recuperação de tecidos nervosos lesionados. Nossos estudos iniciais que buscavam a compreensão desta participação da atividade inflamatória na neurorregeneração e degenerção do OE constataram que a administração tópica de lipopolissacarídeo (LPS) gera perda de seus neurônios olfatórios (OSNs), enquanto que camundongos deficientes do gene Myd88 apresentam uma taxa de reposição neuronal pós-lesão mais elevada que a de selvagens e o uso consecutivo de DEX retarda a neurorregeneração olfatória em curto prazo. Prosseguimos agora no esclarecimento destes resultados em três vertentes: A primeira busca descrever as respostas do OE de animais selvagens e trangênicos Tlr4-/-, Myd88-/-, Ticam1-/-, Il1r1-/-, Casp1-/-/Casp4-/- e Casp1-/-/Casp4-/-/Casp4tg a estímulos inflamatórios provenientes de infusões intranasais de ligantes e citocinas recombinantes envolvidas na sinalização dos TLRs. Isto através de análises histológicas por marcação nuclear e análise da espessura e alterações anatômicas do OE, e da expressão de IL1b e Nf&#954bia por hibridização in situ (ISH), ou ainda pela contagem de suas células TUNEL-positivas pós-tratamento. Neste estudo propomos ainda um modelo de lesão para estudos de neurorregenereração através da análise por imunofluorescência (IF) de OSNs em função do tempo após uma infusão intranasal (IN) de LPS. A segunda analisa por microarranjos de oligonucleotídeos (microarray) as alterações de expressão gênicas associadas à ausência do gene Myd88 no OE pós-lesão seguida de análises histológicas de sua regeneração em camundongos com deleções em genes selecionados. Por fim o terceiro estudo investiga a degeneração e a neurorregeneração do OE sob o efeito do uso tópico consecutivo de DEX. O corticoide é co-aplicado topicamente com um insulto inflamatório para avaliar o seu efeito preventivo e consecutivamente por três dias em dois modelos de lesão para avaliar sua interferência na neurorregeneração 14 dias após o tratamento. Foram realizadas IF para quantificação dos volumes neuronais, espessura do OE, proliferação celular, síntese proteica e morte celular por TUNEL. O uso tópico de LPS promove a degeneração do OE via TLR4 a partir de regiões com expressão de Il1b e Nf&#954bia e número de células TUNEL elevada. Este efeito é via MyD88-dependente sem a participação da TRIF-dependente. O gene Myd88 é tão crucial nesta degeneração do epitélio quanto na gerada por rmIL-1β e rmTNFα. Sua ausência não promove citoproteção contra o gás NO. Possivelmente, CASP1 e IL-1R estejam também envolvidos. O modelo de lesão imunológica para estudos de neurorregeneração é rápido e eficaz. A ausência do gene Myd88 acompanha uma redução na expressão da enzima degradadora de insulina (IDE) no OE pós-lesão. Camundongos que não a expressam apresentam uma reposição celular do epitélio mais rápida. A co-IN de DEX com LPS impede a degeneração do OE. 10µl deste corticoide a 40ng/µl administrada por IN não é tóxica a este epitélio, porém seu uso consecutivo em curto prazo promove aberrações anatômicas nos modelos de lesão imunológica, além de interferir na sua dinâmica de reposição neural, elevação da taxa de síntese proteica e proliferação celular, sem alterar a diferenciação, após lesão induzida por metimazol. / The innate immune response signaling plays a key role in the elimination of pathogens and in the recruitment of new cells to recover the injured nervous tissues. Our preliminary studies on the roles of the inflammatory activity in OE degeneration and neuroregeneration process showed that the topical administration of lipopolysaccharide (LPS) generates the loss of olfactory sensorial neurons (OSNs), Myd88 gene-deficient mice exhibit a higher neuronal replacement rate after injury than wild-type mice, and that the consecutive use of DEX provokes retarding olfactory neuroregeneration over the short term. We seek now to clarify these results in three ways: The first describes the OE response in wild-type animals Tlr4-/-, Myd88-/-, Ticam1-/-, Il1r1-/-, Casp1-/-/Casp4-/- and Casp1-/-/Casp4-/-/Casp4tg animals to inflammation through the intranasal infusion (IN) of ligands and cytokines associated with Toll-Like Receptors (TLR) signaling. This was acomplished through histological analysis of the thickness and anatomical changes in DAPI stained OE, Il1b and Nfκbia expression analysis by in situ hybridization (ISH), and TUNEL-positive cells counting after treatment. In this study we propose an inflammatory lesion for neuroregeneration studies using immunofluorescence (IF) analysis of the OE in function of time after the intranasal infusion of LPS. The second part analyzes the Myd88 gene loss in the OE gene expression of after a lesion using microarray. This is followed by the histological analysis of regeneration using IF in transgenic mice with the deletion of specific genes (microarray versus literature review). Finally, the third study evaluates the OE degeneration and neuroregeneration under the influence of consecutive topical use of the DEX. The corticosteroid is co-administered with the inflammatory stimulus in order to evaluate its protective effect and consecutively for three days in two models of lesion to assess their influence on neuroregeneration 14 days after treatment. The IF analysis was performed in order to quantify the neuronal volumes, the thickness of the OE, cell proliferation, protein synthesis (by incorporation the identification of puromycin) and cell death by TUNEL. The topical use of LPS promotes the degeneration of OE by TLR4 from sites that feature an overexpression of Il1b and Nfκbia and a high number of TUNEL-positive cells. This effect is MyD88-dependent. The Myd88 gene is as crucial in this degeneration of the epithelium as in those generated by rmIL-1β and rmTNFα. Their absence does not promote cytoprotection against the cytotoxic gas nitric oxide (NO). It is possiby that CASP1 and IL-1R are also involved. The immunologic lesion model for neuroregeneration studies is fast and effective. The absence of Myd88 gene reduces the expression of insulin-degrading enzyme (IDE) in the post-lesion OE. Mice without this enzyme show a rapid cellular restoration in the epithelium. The Co-IN of DEX with LPS prevents the degeneration EO. The doses adopted by us are nontoxic; however its short-term consecutive use promotes anatomical aberrations in the immunological lesion model, and interferes with the dynamics of neural replacement by impairing both the rate of protein synthesis and proliferation of the epithelium without halting their differentiation.

Ces travaux de thèse s’inscrivent dans le cadre du projet ANR NEMRO, visant à étudier le lien entre déficience olfactive et maladies neurodégénératives. A cet effet, une biopsie optique de l’épithélium olfactif doit être réalisée. Son accès est cependant impossible, aujourd’hui, avec les outils conventionnels. Pour résoudre ce problème, nous proposons l’utilisation d’un robot à tubes concentriques (RTC). Sa synthèse est réalisée à partir d’images médicales. Elle prend en compte les critères de stabilité, la variabilité inter-sujet, et est associée à un déploiement ALFI (A La File Indienne). Le dispositif étant porté par le sujet, il doit être léger et compact. Une séquence de déploiement spécifique simplifie alors l’unité d’actionnement, et une implémentation est réalisée par fabrication additive multimatériaux. L’évaluation préliminaire d’un déploiement ALFI et des éléments de technologie clés a permis de valider l’approche retenue dans le projet NEMRO, ainsi que sa faisabilité. / This PhD thesis is part of the ANR NEMRO project, whose goal is to study the hypothetical correlation between olfactory deficiency and neurodegenerative diseases. For this purpose, an optical biopsy of the olfactory epithelium must be performed. However, this area is not accessible today with conventional tools. To go beyond this limitation, we propose to investigate the use a concentric tube robot (CTR). Its synthesis is performed from medical images. It takes into account the stability criteria, inter-subject variability, and is associated to a FTL (Follow-The-Leader) deployment. As the device is mounted on the subject, it has to be compact and lightweight. Thus, a specific deployment sequence simplifies the actuation unit, and an implementation is proposed using multimaterial additive manufacturing. Preliminary evaluations of the FTL deployment capabilities and the key components of the device allowed to validate the approach chosen for the NEMRO project, and its feasibility.

During embryonic development a variety of tissues and organs such as the lung, eye, and kidney are being formed. The generation of functional organs is regulated by reciprocal cell-cell interactions. Via the secretion of soluble molecules one type of cells affect the fate of their neighboring cells. A central issue in organogenesis is how a cell interprets such extrinsic signals and adopts a specific fate, and how the cell in response to this signal establishes reciprocal signaling. Transcription factors play a critical role in this process and my thesis focuses on the role of the LIM-homeodomain transcription factor, Lhx2, in the development of three different organ systems, the liver, the hematopoietic system and the olfactory system. The liver is formed from endoderm of the ventral foregut and mesenchyme of the septum transversum (st) and its development depends upon signaling interactions between these two tissues. As the liver becomes a distinct organ it is colonized by hematopoietic cells and serves as hematopoietic organ until birth. The fetal liver provides a microenvironment that supports the expansion of the entire hematopoietic system (HS) including the hematopoietic stem cells (HSCs). Liver development in Lhx2-/- embryos is disrupted leading to a lethal anemia due to insufficient support of hematopoiesis. To further investigate the role of Lhx2 in liver development I analyzed gene expression from the Lhx2 locus during liver development in wild-type and Lhx2-/- mice. Lhx2 is expressed in the liver associated st mesenchymal cells that become integrated in the liver and contribute to a subpopulation of hepatic stellate cells in adult liver. Lhx2 is not required for the formation of these mesenchymal cells, suggesting that the phenotype in Lhx2-/- livers is due to the presence of defective mesenchymal cells. The putative role of Lhx2 in the expansion of the HS was examined by introducing Lhx2 cDNA into embryonic stem cells differentiated in vitro. This approach allowed for the generation of immortalized multipotent hematopoietic progenitor cell (HPC) lines that share many characteristics with normal HSCs. The Lhx2-dependent generation of HSC-like cell lines suggests that Lhx2 plays a role in the maintenance and/or expansion of the HS. To isolate genes putatively linked to Lhx2 function, genes differentially expressed in the HPC lines were isolated using a cDNA subtraction approach. This allowed for the identification of a few genes putatively linked to Lhx2 function, as well as several stem cell-specific genes. The antagonist of Wnt signalling, Dickkopf-1 (Dkk-1), was identified in the former group of genes as it showed a similar expression pattern in the fetal liver, as that of Lhx2 and expression of Dkk-1 in fetal liver and in HPC lines appeared to be regulated by Lhx2. This suggests that Dkk-1 plays a role in liver development and/or HSC physiology during embryonic development. During development of the olfactory epithelium (OE) neuronal progenitors differentiate into mature olfactory sensory neurons (OSNs) that are individually specified into over a thousand different subpopulations, each expressing a unique odorant receptor (OR) gene. The expression of Lhx2 in olfactory neurons suggested a potential role for Lhx2 in the development of OSNs. To address this OE from Lhx2-/- and wild-type mice was compared. In the absence of functional Lhx2 neuronal differentiation was arrested prior to onset of OR expression. Lhx2 is thus required for the development of OSN progenitors into functional, individually specified OSNs. Thus, Lhx2 trigger a variety of cellular responses in different organ systems that play important roles in organ development in vivo and stem cell expansion in vitro.

in English While axon fasciculation plays a key role in the development of neural networks, very lit- tle is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behaviour that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and me- chanical tension in the axons. This is upheld on quantitative level by conforming change of network global structure in response to various pharmacological treatments, without active involvement of growth cones. The calibrated manipulations of interacting shafts provide qualitative support for the hypothesis, and also allow us to quantify the mechan- ical tension of axons in our system. Furthermore, we introduce a biophysical model of the zippering dynamics, which efficiently serves the purpose of estimating the magnitude of remaining involved...

Extrazelulläre Purine und Pyrimidine sind wichtige Signalmoleküle, die über membranständige Rezeptoren, so genannte purinerge Rezeptoren ihre biologischen Effekte vermitteln. In der vorliegenden Arbeit wurden ATP-induzierte Antworten in den Stützzellen des olfaktorischen Epithels mit Hilfe der Calcium-Imaging-Technik charakterisiert.Die Applikation von ATP induzierte Zunahmen der intrazellulären Kalziumkonzentration ([Ca2+]i) sowohl in Anwesenheit, als auch in Abwesenheit von extrazellulärem Kalzium. Anders bei Anwendung von CPA, einem spezifischen Hemmstoff der Ca2+-ATPase des sarkoplasmatischen bzw. endoplasmatischen Retikulums. In diesen Versuchen wurden die ATP-induzierten [Ca2+]i-Zunahmen komplett aufgehoben. Das zeigt, dass die ATP-induzierten [Ca2+]i-Zunahmen in Stützzellen größtenteils, wenn nicht vollständig, durch die Aktivierung von G-Protein gekoppelten P2Y-Rezeptoren ausgelöst werden. Die ermittelte Wirkpotenz purinerger Agonisten war UTP>ATP>ATPγS. Die ATP-induzierten [Ca2+]i-Zunahmen konnten durch die purinergen Antagonisten PPADS und RB2 reduziert werden. Die hemmende Wirkung des purinergen Antagonisten Suramin blieb aus. Zusammen weisen die oben genannten Ergebnisse dieser Arbeit darauf hin, dass extrazelluläre Nukleotide die Stützzellen des olfaktorischen Epithels über P2Y2 / P2Y4-artige Rezeptoren aktivieren. Zusätzlich zeigten die Versuche mit dem Ektonukleotidase-Hemmstoff ARL 67156, dass im olfaktorischen Epithel von larvalen Xenopus laevis eine hohe Ektonukleotidasenaktivität herrscht.