京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19599号 / 医博第4106号 / 新制||医||1014(附属図書館) / 32635 / 京都大学大学院医学研究科医学専攻 / (主査)教授 柳田 素子, 教授 妹尾 浩, 教授 浅野 雅秀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Phenylethanolamine-N-methyltransferase (Pnmt) catalyzes the conversion of noradrenaline to adrenaline and is the last enzyme in the catecholamine biosynthetic pathway. Pnmt serves as a marker for adrenergic cells, and lineage-tracing experiments have identified the embryonic heart and hindbrain region as the first sites of Pnmt expression in the mouse. Pnmt expression in the heart occurs before the adrenal glands have formed and prior to sympathetic innervation, suggesting that the heart is the first site of catecholamine production in the mouse. The function of these Pnmt+ cells in heart development remains unclear. In the present study, we test the hypothesis that (i) a genetic ablation technique utilizing a suicide reporter gene selectively destroys Pnmt cells in the mouse, and (ii) Pnmt cells are required for normal cardiovascular and neurological function. To genetically ablate adrenergic cells, we mated Pnmt-Cre mice, in which Cre-recombinase is under the transcriptional regulation of the Pnmt promoter, and a Cre -activated diphtheria toxin A (DTA) mouse strain (ROSA26-eGFP-DTA), thereby causing activation of the toxic allele (DTA) in Pnmt-expressing (adrenergic) cells resulting in selective "suicide" of these cells in approximately half of the offspring. The other half serve as controls because they do not have the ROSA26-eGFP-DTA construct. In the Pnmt+/Cre; R26+/DTA offspring, we achieve a dramatic reduction in Pnmt transcript and Pnmt immunoreactive area in the adrenal glands. Furthermore, we show that loss of Pnmt cells results in severe left ventricular dysfunction that progressively worsens with age. These mice exhibit severely reduced cardiac output and ejection fraction due to decreased LV contractility and bradycardia at rest. Surprisingly, these mice appear to have a normal stress response, as heart rate and ejection fraction increased to a similar extent compared to controls. In addition to baseline cardiac dysfunction, these mice fail to gain body weight in a normal manner and display gross neurological dysfunction, including muscular weakness, abnormal gaiting, and altered tail suspension reflex, an indicator of neurological function. This work demonstrates that selective Pnmt cell destruction leads to severe left ventricular dysfunction, lack of weight gain, and neurological dysfunction. This novel mouse is expected to shed insight into the role of Pnmt cells in the heart, and suggests a role for Pnmt cells in neurological regulation of feeding behavior, metabolism, and motor control.

The wide scale use of ZnO nanoparticles (NPs) in the world consumer market has resulted in likelihood of exposure to human beings. The present study was aimed to assess the in vitro and in vivo interactions of ZnO NPs in the mammalian system and to elucidate the possible mechanism of their toxicity. Our in vitro results using human epidermal cells (A431), primary human epidermal keratinocytes and human liver cells (HepG2) demonstrated that cells exposed to ZnO NPs exhibit a decrease in cell viability which was independent of NP dissolution. ZnO NPs also induced oxidative DNA damage as evidenced by an increase in the Fpg sensitive sites. The reactive oxygen species triggered a decrease in mitochondrial membrane potential and an increase in the ratio of Bax/Bcl2 leading to apoptosis through the intrinsic pathway. In addition, ZnO NPs induced phosphorylation of JNK, P38 and P53ser15. The results from our in vivo studies using a mouse model showed that ZnO NPs induce lipid peroxidation, oxidative DNA damage and apoptosis in liver which further confirmed our in vitro findings. The data from the present study provide valuable insights into the cellular interactions of ZnO NPs and the underlying molecular mechanism of their toxicity. The results also stress the need for a comprehensive environmental health and safety assessment of engineered nanomaterials to ensure safer nanotechnology based products.

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<p>Allergic asthma is a chronic and complex disease of the airways characterized by dysregulated immune-inflammatory responses to aeroallergens and reversible airflow obstruction. The prevalence and economic burden of allergic asthma have increased substantially over the last five decades. Despite remarkable progress in our understanding of the immunobiology and pathophysiology of asthma, the ontogeny of the disease remains elusive. As a result, there is a lack of effective preventative strategies. Here, we used a murine model of allergic asthma to house dust mite (HDM), the most pervasive indoor aeroallergen worldwide to address issues pertaining to the development of allergic asthma. First, we provided a comprehensive computational view of the impact of dose and length of HDM exposure on both local and systemic allergic outcomes (Chapter 2). Parameters, such as thresholds of responsiveness, and non-linear relationships between allergen exposure, allergic sensitization and airway inflammation were identified. We, then, investigated molecular signatures implicated in the onset of allergic responses (Chapter 3). HDM exposure was associated with production of the epithelial-associated cytokines TSLP, IL-25 and IL-33. However, only IL-33 signaling was necessary for intact Th2 immunity to HDM, likely because of its superior ability to induce the critical co-stimulatory molecule OX40L on dendritic cells and expand innate lymphoid cells. Lastly, as individuals are most likely exposed to allergens concomitantly to other environmental immunogenic agents, we studied the impact of an initial immune perturbation on allergic responses to sub-threshold amounts of HDM (Chapter 4). We showed that transient expression of GM-CSF in the airway substantially lowers the threshold of allergen required to generate robust, HDM-specific Th2 immunity, likely through increasing IL-33 production from alveolar type II cells. These studies favor a paradigm whereby distinct molecular pathways can elicit type 2 immunity, intimating the need to classify asthma into distinct clinical subsets.</p> / Doctor of Philosophy (PhD)

Cardiovascular disease is the leading cause of death in the United States, and coronary artery disease (CAD) kills over 370,000 people annually. There are available therapies that offer a temporary solution; however, only a heart transplant can fully resolve heart failure, and donor organ shortages severely limit this therapy. C-kit+ human cardiac stem cells (hCSCs) offers a viable alternative therapy to treat cardiovascular disease by replacing damaged cardiac tissue; however, low cell viability, low retention/engraftment, and uncontrollable in vivo differentiation after transplantation has limited the efficacy of stem cell therapy. Tissue engineering solutions offer potential tools to overcome current limitations of stem cell therapy. Materials derived from natural sources such as keratin from human hair offers innate cellular compatibility, bioactivity, and low immunogenicity. Keratin proteins extracted using oxidative chemistry known as keratose (KOS) have shown therapeutic potential in a wide range of applications including cardiac regeneration. My studies utilize KOS hydrogels to modulate c-kit+ hCSC differentiation, and explore the capability of differentiated cells to regenerate vascular tissue. In the first Chapter, we reviewed literature relevant to keratin-based biomaterials and their biomedical applications, the use of stem cells in cardiovascular research, and the differentiation of vascular smooth muscle cells (VSMCs). The section on biomedical applications of keratin biomaterials focuses on the oxidized form of keratin known as keratose (KOS), because this was the material used for our research. Since we planned to use this material in conjunction with c-kit+ hCSCs, we also briefly explored the use of stem cells in cardiovascular research. Additionally, we examined some key signaling pathways, developmental origins, and the cell phenotype of VSMCs for reasons that will become clear after observing results from chapters 2 and 3. Based upon our review of the literature, KOS biomaterials and c-kit+ hCSCs were determined to be promising as a combined therapeutic for the regeneration of cardiac tissue. Research in Chapter 2 focused on characterizing the effects of KOS hydrogel on c-kit+ hCSC cell viability, proliferation, morphology, and differentiation. Results demonstrated that KOS hydrogels could maintain hCSC viability without any observable toxic effects, but it modulated cell size, proliferation, and differentiation compared to standard tissue culture polystyrene cell culture (TCPS). KOS hydrogel produced gene and protein expression consistent with a VSMC phenotype. Further, we also observed novel "endothelial cell tube-like" microstructures formed by differentiated VSMCs only on KOS hydrogel, suggesting a potential capability of the hCSC-derived VSMCs for in vitro angiogenesis. Results from this study lead us to question what signaling pathways might be responsible for the apparent VSMC differentiation pattern we observed on KOS hydrogels. Research in Chapter 3 explored the time course of VSMC differentiation, cell contractility, inhibition of VSMC differentiation, and measured protein expression of transforming growth factor beta 1 (TGF-β1) and its associated peptides for hCSCs cultured on KOS hydrogels, tissue culture polystyrene, and collagen hydrogels. A review of VSMC differentiation signaling pathways informed our decision to investigate the role of TGF-β1 in VSMC differentiation. Results demonstrated that KOS hydrogel differentiated hCSCs significantly increased expression for all three vascular smooth muscle (VSM) markers compared to TCPS differentiated cells. Additionally, KOS differentiated hCSCs were significantly more contractile than cells differentiated on TCPS. Recombinant human (rh) TGF-β1 was able to induce VSM differentiation on TCPS. VSM differentiation was successfully inhibited using TGF-β NABs and A83-01. Enzyme-Linked Immunosorbent Assay (ELISA) analysis revealed that both TCPS and KOS hydrogel differentiated cells produced TGF-β1, with higher levels being measured at early time points on TCPS and later time points on KOS hydrogels. Results from supplementing rhTGF-β1 to TCPS and KOS hydrogels revealed that KOS seems to interact with TGF-β to a greater extent than TCPS. Western blot results revealed that latency TGFβ binding protein (LTBP-1) and latency associated peptide (LAP) had elevated levels early during differentiation. Further, the levels of LTBP-1 and LAP were higher on KOS differentiated hCSCs than TCPS hCSCs. This study reaffirms previous results of a VSM phenotype observed on KOS hydrogels, and provides convincing evidence for TGF-β1 inducing VSM differentiation on KOS hydrogels. Additionally, results from ELISA and western blot provide evidence that KOS plays a direct role in this pathway via interactions with TGF-β]1 and its associated proteins LTBP-1 and LAP. Results from chapter 2 and 3 offered significant evidence that our cells exhibited a VSMC phenotype, and that TGF-β1 signaling was a key contributor for the observed phenotype, but we still needed an animal model to explore the therapeutic potential of our putative VSMCs. Research in Chapter 4 investigated a disease model to test the ability of KOS hydrogel differentiated cells to regenerate vascular tissue. To measure vascular regenerative capability, we selected a murine model of critical limb ischemia (CLI). CLI was induced in 3 groups (n=15/group) of adult mixed gender NSG mice by excising the femoral artery and vein, and then treated the mice with either PBS (termed as PBS-treated), Cells differentiated on TCPS (termed as Cells from TCPS), or KOS hydrogel-derived VSMCs (termed as Cells from KOS). Blood perfusion of the hind limbs was measured immediately before and after surgery, then 14, and 28 days after surgery using Laser Doppler analysis. Tissue vascularization, cell engraftment, and skeletal muscle regeneration were measured using immunohistochemistry, 1,1'-Dioctadecyl3,3,3',3'-Tetramethylindocarbocyanine Perchlorate (DiL) vessel painting, and hematoxylin and eosin (HandE) pathohistological staining. During the 4-week period, both cell treatment groups showed significant increases in blood perfusion compared to the PBS-treated control, and at day 28 the Cells from KOS group had significantly better blood flow than the Cells from TCPS group. Additionally, the Cells from KOS group demonstrated a significant increase in the ratio of DiL positive vessels, capillary density, and a greater density of small diameter arterioles compared to the PBS-treated group. Further, both cell-treated groups had similar levels of engraftment into the host tissue. We conclude that Cells from KOS therapy increases blood perfusion in an NSG model of CLI, but does not lead to increased cell engraftment compared to other cell based therapies. Overall, the results from this dissertation demonstrated that KOS hydrogels produce VSMC differentiation from c-kit+ hCSCs mediated by TGF-β1 signaling, and that the differentiated cells are able to increase blood perfusion in a CLI model by increasing capillary density, suggesting enhanced angiogenesis. Future studies should explore potential protein-protein interactions between KOS, TGF-β1 and its associated proteins. Additionally, we should plan animal studies that examine the efficacy of our cells to regenerate cardiac tissue following an acute myocardial infarction (AMI). / PHD

[ES] El daño cerebral es la mayor causa de discapacidad en la etapa adulta, particularmente afectando a la población anciana. Independientemente de la causa, los diferentes tipos de daño cerebral comparten eventos fisiopatológicos similares. Hasta ahora, la mayoría de los estudios se enfocaron en estudiar las respuestas inmediatas tras la lesión, mientras que los mecanismos que subyacen bajo los procesos de plasticidad y regeneración cortical aún son desconocidos. Neuregulina 1 (Nrg1) es una proteína esencial en el desarrollo de los circuitos corticales que se ha asociado a diferentes trastornos psiquiátricos, como la esquizofrenia. En las últimas décadas, varios trabajos proponen a Nrg1 como un factor neuroprotector emergente en el ámbito de lesión. No obstante, la mayoría de las investigaciones se centran en estudiar la respuesta temprana de la forma soluble de Nrg1 tras el daño, mediada por la activación de los receptores ErbB, la cual no recapitula totalmente la compleja señalización de Nrg1. De este modo, nuestro laboratorio ha demostrado previamente que la señalización intracelular de Nrg1 se activa en situaciones de hipoxia, promoviendo la supervivencia neuronal tras ictus. El principal objetivo de esta tesis es estudiar el papel de la señalización de Nrg1 en la regeneración y plasticidad cortical tras daño cerebral. Para ello, hemos desarrollado nuevos modelos para 1) ofrecer una metodología que permita estudiar la regeneración axonal in vitro e in vivo y 2) específicamente estudiar el papel de la señalización intracelular de Nrg1 en el ámbito de daño cortical. Primero, desarrollamos un nuevo modelo in vitro de lesión axonal en cultivos de neuronas corticales, utilizando técnicas de electroporación para marcar un número limitado de neuronas, combinado con una posterior lesión física basada en una transección mecánica de los axones. En este modelo, también se realizaron estudios de ganancia y pérdida de función para comprender el papel de Nrg1 en el crecimiento axonal. Nuestros resultados mostraron que Nrg1, y específicamente la activación de su vía intracelular, potencia el crecimiento axonal tras daño. Posteriormente, diseñamos una metodología novedosa en ratones para estudiar la regeneración cortical, combinando técnicas de trazado de conexiones cortico-corticales con una lesión focal y mecánica en la corteza primaria motora. Se realizó una extensa caracterización funcional empleando diversas pruebas comportamentales específicas para detectar déficits motores en lesiones unilaterales como la ofrecida en este modelo. Gracias al procesamiento del tejido cerebral en series flotantes, se combinaron diferentes tinciones para realizar reconstrucciones 3D del cerebro y, así, ofrecer un estudio completo incluyendo medidas volumétricas y un análisis de diferentes poblaciones celulares y estructuras subcelulares. Como ejemplo, se investigó la correlación entre la eliminación de redes perineuronales y la activación de células microgliales en la zona adyacente a la lesión. Esta metodología de lesión cortical in vivo se utilizó en innovadores modelos genéticos de ratón en esta tesis para entender el papel de Nrg1 tras daño cortical. Así, se eliminó la expresión del gen de Nrg1 en ratonas jóvenes y maduras previamente a la lesión, observando que la ausencia de Nrg1 promueve la respuesta neuroinflamatoria y una preservación axonal limitada, conllevando una menor recuperación motora espontánea tras la lesión. Finalmente, para ofrecer una visión mecanicista del papel de la señalización intracelular de Nrg1, su dominio intracelular se expresó específicamente en neuronas corticales, observando que la activación de esta vía de señalización reduce la respuesta inflamatoria tras lesión cortical. En conclusión, estos resultados señalan que Nrg1, y específicamente la activación de su vía intracelular, podría ser una diana molecular prometedora en el contexto de neuroprotección, regeneración y recuperación cortical tras daño cerebral. / [CA] El dany cerebral és la major causa de discapacitat en l'etapa adulta, particularment en la població anciana. Independentment de la causa, els diferents tipus de dany cerebral comparteixen esdeveniments fisiopatològics similars. Fins ara, la majoria dels estudis es van enfocar a estudiar les respostes immediates després de la lesió, mentre que els mecanismes que subjauen sota els processos de plasticitat i regeneració cortical encara són desconeguts. Neuregulina 1 (Nrg1) és una proteïna essencial en el desenvolupament dels circuits corticals que s'ha associat a diferents trastorns psiquiàtrics, com l'esquizofrènia. En les últimes dècades, diversos treballs proposen a Nrg1 com un factor neuroprotector emergent en l'àmbit de lesió. No obstant això, la majoria de les investigacions se centren en estudiar la resposta primerenca de la forma soluble de Nrg1 després del mal, mediada per l'activació dels receptors ErbB, la qual no recapitula totalment la complexa senyalització de Nrg1. D'aquesta manera, el nostre laboratori ha demostrat prèviament que la senyalització intracel·lular de Nrg1 s'activa en situacions d'hipòxia, promovent la supervivència neuronal després de l'ictus. El principal objectiu d'aquesta tesi és estudiar el paper de la senyalització de Nrg1 en la regeneració i plasticitat cortical després de dany cerebral. Per a això, hem desenvolupat nous models per a 1) oferir una metodologia que permeta estudiar la regeneració axonal in vitro i in vivo i 2) específicament estudiar el paper de la senyalització intracel·lular de *Nrg1 en l'àmbit de mal cortical. Primer, desenvolupem un nou model in vitro de lesió axonal en cultius de neurones corticals, utilitzant tècniques de electroporació per a marcar un nombre limitat de neurones, combinat amb una posterior lesió física basada en una secció mecànica dels axons. En aquest model, també es van realitzar estudis de guany i pèrdua de funció per a comprendre el paper de Nrg1 en el creixement axonal. Aquests resultats van mostrar que Nrg1, i específicament l'activació de la seua via intracel·lular, potència el creixement axonal després de mal. Posteriorment, dissenyem una metodologia nova en ratolins per a estudiar la regeneració cortical, combinant tècniques de traçat de connexions cortico-corticals amb una lesió focal i mecànica en l'escorça primària motora. Es va realitzar una extensa caracterització funcional emprant diverses proves comportamentals específiques per a detectar dèficits motors en lesions unilaterals com l'oferida en aquest model. Gràcies al processament del teixit cerebral en sèries flotants, es van combinar diferents tincions per a realitzar reconstruccions 3D del cervell i, així, oferir un estudi complet incloent mesures volumètriques i una anàlisi de diferents poblacions cel·lulars i estructures subcel·lulars. Com a exemple, es va investigar la correlació entre l'eliminació de xarxes perineuronals i l'activació de cèl·lules microglials en la zona adjacent a la lesió. Aquesta metodologia de lesió cortical in vivo es va utilitzar en innovadors models genètics de ratolí per a entendre el paper de Nrg1 després de mal cortical. Es va eliminar l'expressió del gen de Nrg1 en ratolins joves i madurs prèviament a la lesió, observant que l'absència de Nrg1 promou la resposta neuroinflamatoria i una preservació axonal limitada, el que comporta una menor recuperació motora espontània després de la lesió. Finalment, per a oferir una visió mecanicista del paper de la senyalització intracel·lular de Nrg1, el seu domini intracel·lular es va expressar específicament en neurones corticals, observant que l'activació d'aquesta via de senyalització redueix la resposta inflamatòria després de lesió cortical. En conclusió, aquests resultats assenyalen que la senyalització de Nrg1, i específicament l'activació de la seua via intracel·lular, podria ser una diana molecular prometedora en el context de neuroprotecció, regeneració i recuperació cortical després de dany cerebral. / [EN] Brain damage is the leading cause of disability in adults, particularly in the elderly population. Regardless of the cause, different types of brain injury share similar physiopathological events. Most studies to date have focused on the immediate post-injury response, whereas less is known about cortical regeneration and plasticity after brain injury. Neuregulin 1 (Nrg1) is essential for the development of cortical circuits and has been implicated in several psychiatric disorders, such as schizophrenia. In the last decades, several works proposed Nrg1 signaling as an emergent modulator of neuroprotection upon damage. However, most research has focused on the early response of Nrg1 diffusible isoforms mediated by ErbB receptor activation after injury, which does not fully recapitulate the complexity of Nrg1 signaling. In this context, we have previously shown that Nrg1 intracellular signaling is activated under hypoxic conditions and promotes neuronal survival after cortical stroke. The overall goal of this dissertation is to investigate the role of Nrg1 signaling in cortical regeneration and plasticity after cortical damage. To achieve this goal, we developed novel, refined models to 1) provide new methodological approaches to study axonal regeneration in vitro and in vivo and 2) specifically target Nrg1 signaling and particularly investigate the role of Nrg1 intracellular pathway upon cortical injury. First, we developed a novel in vitro model of axonal injury in cortical neuron cultures. Specifically, we performed sparse labeling of the cultures by electroporation techniques and induced physical injury by mechanical transection of the axons. In this model, we also performed gain- and loss-of-function approaches to investigate the role of Nrg1 in axonal outgrowth. Our results showed that Nrg1, and specifically the activation of its intracellular signaling, potentiates axonal outgrowth upon injury. Second, we developed a novel methodology in mice that combines cortico-cortical projection tracing with focal mechanically controlled cortical damage (CCD) to study cortical regeneration. We performed extensive functional characterization of the model and provided meaningful behavioral tasks to detect motor impairment in unilateral focal injuries. Since tissue processing is performed in serial floating sections, we combined different immunolabeling and 3D brain reconstruction to evaluate stereological measurements and analysis of axonal projections and different cell populations. As a biological result, we showed a correlation between perineuronal nets (PNNs) disruption and microglial activation in the perilesional region. Later, we applied the CCD methodology in novel genetic mouse models to better understand the role of Nrg1 signaling in vivo after cortical injury. We induced acute Nrg1 deletion prior to injury in young and aged mice and observed that Nrg1 deletion promoted neuroinflammatory response and limited axonal preservation and spontaneous motor recovery after cortical injury. Finally, we specifically expressed Nrg1-ICD to provide a mechanistic perspective and observed that activation of this intracellular pathway decreased the neuroinflammatory response. Collectively, our results shed light on Nrg1 signaling, and specifically the activation of its intracellular pathway, as a promising molecular target in neuroprotection, cortical regeneration, and recovery after brain injury. / González Manteiga, A. (2023). Understanding the Role of Nrg1 Signaling Upon Brain Damage: Novel Models of Cortical Regeneration [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/200224