<p>  </p> <p>Traditionally, the exocrine and endocrine cellular compartments of the pancreas have been considered distinct functional systems. However, recent studies suggest a more intricate relationship between the exocrine and endocrine, which may impact pancreatic growth and health. Additionally, translational control mechanisms have been linked to organ development. Our lab has shown that the mRNA translation factor eukaryotic initiation factor 5A (eIF5A), when in its post-translationally modified “hypusinated” form, plays a role in pancreas development. The hypusination of eIF5A requires the rate-limiting enzyme deoxyhypusine synthase (<em>Dhps</em>) to post-translationally modify a critical lysine residue which in turn produces the active form of eIF5A that functions in mRNA translation. When we generated animals with a deletion of <em>Dhps</em> in the pancreatic progenitor cells, there was no alteration in islet mass but significant exocrine insufficiency at embryonic (E) day 18.5 concomitant with downregulation of proteins required for exocrine pancreas development and function. Resultantly these animals died by 6 weeks-of-age. These observations prompted the question, is the phenotype caused by the absence of hypusinated eIF5A or the increase of unhypusinated eIF5A? To address this, we generated a mouse model wherein <em>Eif5a</em> is deleted in the pancreas (eIF5A∆PANC) and these mutant animals also display exocrine insufficiency. Interestingly, beta cell mass is increased at E18.5, and the mutant animals maintain euglycemia and survive up to 2 years. Ongoing analyses are interrogating the differences between these animal models with the goal to determine if mRNA translation facilitates cellular communication between the exocrine and endocrine pancreas.</p>

INTRODUÇÃO: Após a cirurgia pancreática, a função exócrina é determinada pela extensão da ressecção e a quantidade de tecido pancreático remanescente, sendo recomendável a avaliação da insuficiência pancreática exócrina (IPE) em todos os pacientes. A reposição de enzimas pancreáticas é o pilar do tratamento da IPE, pois melhora a absorção de gordura, diminui os sintomas relacionados com a má absorção e melhora a qualidade de vida (QV). OBJETIVO: Sabendo que o ajuste da dose de enzimas pancreáticas é realizado com base nos sinais clínicos relatados pelo paciente, o presente estudo visa aprofundar a avaliação clínica destes e avaliar o atual protocolo de tratamento, mantendo ou melhorando a QV dos pacientes. MÉTODOS: Estudo transversal em que foram avaliados adultos com histórico de ressecção pancreática há 6 meses ou mais. No tempo 1 foi realizada avaliação nutricional antropométrica e recordatório alimentar, avaliação clínica de qualidade de vida (questionário SF-36), investigação hábitos intestinais e exames laboratoriais. No tempo 2 foi realizada nova consulta para discussão dos resultados e orientação nutricional individualizada. Para análise de correlações foi usado o teste de Pearson, para associações o teste de Fisher e para comparação de médias o teste Mann-Whitney. RESULTADOS: Foram avaliados 39 pacientes, 22 (56,4%) do sexo feminino; 33 (84,6%) >=60 anos; tempo pós operatório 14,1± 6,8 anos; exames bioquímicos: em todas as dosagens a maioria dos pacientes apresenta resultados dentro dos valores de referência, mas há alta prevalência de deficiência de vitaminas lipossolúveis; os pacientes têm bom estado nutricional já que grande parte apresenta eutrofia segundo o IMC (46,1%) e segundo a porcentagem de gordura (35,9%); no geral não relatam sintomas gastrointestinais adversos: 61,5% com fezes formadas, 53,8% sem dor abdominal, 84,6% sem esteatorreia; adequação no consumo de macronutrientes: 51,3% consumo adequado de carboidratos e lipídios, e 64,1% de consumo excessivo de proteínas; correlações positivas: a dose de enzimas se correlaciona com a dor (p= 0,004) e o IMC (p= 0,009), ou seja, pacientes que relatam mais dor e que pesam mais são os que recebem as maiores doses de enzimas pancreáticas; correlações negativas: capacidade funcional e parâmetros de avaliação nutricional como IMC (p=0,004), e porcentagem de gordura (p=0,028), e também parâmetros clínicos como a dose de enzimas (p=0,022) e o número de evacuações por dia (p=0,024); associações: a inadequação do consumo de lipídios na dieta está associada com importantes sintomas gastrointestinais como a consistência amolecida das fezes (p=0,005) e flatulência (p=0,012) e ressalta a importância da orientação nutricional aos pacientes em reposição de enzimas pancreáticas. CONCLUSÃO: A maioria dos pacientes apresentou bons resultados de exames bioquímicos, qualidade de vida, consumo de macronutrientes, estado nutricional e sintomas gastrointestinais. Observaram-se importantes correlações e associações que demonstram que o estado nutricional, o consumo alimentar e a dose de enzimas interferem nos sintomas gastrointestinais e na auto-percepção de qualidade de vida dos pacientes. Sendo assim, o atual protocolo é válido, mas deve ser associado a orientação nutricional individualizada / BACKGROUND: After pancreatic surgery, exocrine function is determined by the extent of resection and the amount of remaining pancreatic tissue, and all patients should be evaluated for exocrine pancreatic insufficiency (EPI). Pancreatic enzyme replacement is the mainstay of EPI treatment, since it improves fat absorption, reduces symptoms related to malabsorption and improves quality of life (QoL). OBJECTIVE: Knowing that the adjustment of pancreatic enzymes dose is based on the clinical signs reported by the patient, the present study aims to deepen the clinical evaluation and to evaluate the current protocol of treatment, maintaining or improving patients quality of life. METHODS: A cross-sectional study in which adults were evaluated 6 months or more after pancreatic resection. At time 1, anthropometric evaluation and food recall, clinical evaluation of quality of life (SF-36 questionnaire), intestinal habits and laboratory tests were performed. At time 2 a new consultation was conducted to discuss the results and to provide individualized nutritional guidance. For the correlations analysis the Pearson test was used, for associations the Fisher test and for comparison of means the Mann-Whitney test. RESULTS: 39 patients were evaluated, 22 (56.4%) female; 33 (84.6%) >= 60 years; Time after surgery 14.1 ± 6.8 years; Biochemical tests: at all dosages most patients present results within the reference values, but there is a high prevalence of fat-soluble vitamins deficiency; The patients have good nutritional status since a great part presents eutrophy according to the BMI (46.1%) and according to the percentage of body fat (35.9%); In general they do not report adverse gastrointestinal symptoms: 61.5% with feces formed, 53.8% without abdominal pain, 84.6% without steatorrhea; Adequacy in macronutrient consumption: 51.3% adequate consumption of carbohydrates and lipids, and 64.1% excessive consumption of proteins; Positive correlations: enzyme dose correlates with pain (p = 0.004) and BMI (p = 0.009); that is, patients who report more pain and who weigh more are those who receive the highest doses of pancreatic enzymes; Negative correlations: functional capacity and nutritional assessment parameters such as BMI (p = 0.004), and body fat percentage (p = 0.028), as well as clinical parameters such as enzyme dose (p = 0.022) and number of bowel movements per day p=0.024); Associations: the dietary lipid consumption inadequacy is associated with important gastrointestinal symptoms such as soft stool consistency (p=0.005) and flatulence (p=0.012), and emphasizes the importance of nutritional guidance to patients on pancreatic enzyme replacement therapy. CONCLUSION: Most patients presented good results of biochemical tests, quality of life, macronutrient consumption, nutritional status and gastrointestinal symptoms. Significant correlations and associations have been observed that evidence that nutritional status, food intake and enzyme dose interferes with gastrointestinal symptoms and self-perceived quality of life of patients. Therefore, the current protocol is valid, but should be associated with individualized nutritional guidance

INTRODUÇÃO: Após a cirurgia pancreática, a função exócrina é determinada pela extensão da ressecção e a quantidade de tecido pancreático remanescente, sendo recomendável a avaliação da insuficiência pancreática exócrina (IPE) em todos os pacientes. A reposição de enzimas pancreáticas é o pilar do tratamento da IPE, pois melhora a absorção de gordura, diminui os sintomas relacionados com a má absorção e melhora a qualidade de vida (QV). OBJETIVO: Sabendo que o ajuste da dose de enzimas pancreáticas é realizado com base nos sinais clínicos relatados pelo paciente, o presente estudo visa aprofundar a avaliação clínica destes e avaliar o atual protocolo de tratamento, mantendo ou melhorando a QV dos pacientes. MÉTODOS: Estudo transversal em que foram avaliados adultos com histórico de ressecção pancreática há 6 meses ou mais. No tempo 1 foi realizada avaliação nutricional antropométrica e recordatório alimentar, avaliação clínica de qualidade de vida (questionário SF-36), investigação hábitos intestinais e exames laboratoriais. No tempo 2 foi realizada nova consulta para discussão dos resultados e orientação nutricional individualizada. Para análise de correlações foi usado o teste de Pearson, para associações o teste de Fisher e para comparação de médias o teste Mann-Whitney. RESULTADOS: Foram avaliados 39 pacientes, 22 (56,4%) do sexo feminino; 33 (84,6%) >=60 anos; tempo pós operatório 14,1± 6,8 anos; exames bioquímicos: em todas as dosagens a maioria dos pacientes apresenta resultados dentro dos valores de referência, mas há alta prevalência de deficiência de vitaminas lipossolúveis; os pacientes têm bom estado nutricional já que grande parte apresenta eutrofia segundo o IMC (46,1%) e segundo a porcentagem de gordura (35,9%); no geral não relatam sintomas gastrointestinais adversos: 61,5% com fezes formadas, 53,8% sem dor abdominal, 84,6% sem esteatorreia; adequação no consumo de macronutrientes: 51,3% consumo adequado de carboidratos e lipídios, e 64,1% de consumo excessivo de proteínas; correlações positivas: a dose de enzimas se correlaciona com a dor (p= 0,004) e o IMC (p= 0,009), ou seja, pacientes que relatam mais dor e que pesam mais são os que recebem as maiores doses de enzimas pancreáticas; correlações negativas: capacidade funcional e parâmetros de avaliação nutricional como IMC (p=0,004), e porcentagem de gordura (p=0,028), e também parâmetros clínicos como a dose de enzimas (p=0,022) e o número de evacuações por dia (p=0,024); associações: a inadequação do consumo de lipídios na dieta está associada com importantes sintomas gastrointestinais como a consistência amolecida das fezes (p=0,005) e flatulência (p=0,012) e ressalta a importância da orientação nutricional aos pacientes em reposição de enzimas pancreáticas. CONCLUSÃO: A maioria dos pacientes apresentou bons resultados de exames bioquímicos, qualidade de vida, consumo de macronutrientes, estado nutricional e sintomas gastrointestinais. Observaram-se importantes correlações e associações que demonstram que o estado nutricional, o consumo alimentar e a dose de enzimas interferem nos sintomas gastrointestinais e na auto-percepção de qualidade de vida dos pacientes. Sendo assim, o atual protocolo é válido, mas deve ser associado a orientação nutricional individualizada / BACKGROUND: After pancreatic surgery, exocrine function is determined by the extent of resection and the amount of remaining pancreatic tissue, and all patients should be evaluated for exocrine pancreatic insufficiency (EPI). Pancreatic enzyme replacement is the mainstay of EPI treatment, since it improves fat absorption, reduces symptoms related to malabsorption and improves quality of life (QoL). OBJECTIVE: Knowing that the adjustment of pancreatic enzymes dose is based on the clinical signs reported by the patient, the present study aims to deepen the clinical evaluation and to evaluate the current protocol of treatment, maintaining or improving patients quality of life. METHODS: A cross-sectional study in which adults were evaluated 6 months or more after pancreatic resection. At time 1, anthropometric evaluation and food recall, clinical evaluation of quality of life (SF-36 questionnaire), intestinal habits and laboratory tests were performed. At time 2 a new consultation was conducted to discuss the results and to provide individualized nutritional guidance. For the correlations analysis the Pearson test was used, for associations the Fisher test and for comparison of means the Mann-Whitney test. RESULTS: 39 patients were evaluated, 22 (56.4%) female; 33 (84.6%) >= 60 years; Time after surgery 14.1 ± 6.8 years; Biochemical tests: at all dosages most patients present results within the reference values, but there is a high prevalence of fat-soluble vitamins deficiency; The patients have good nutritional status since a great part presents eutrophy according to the BMI (46.1%) and according to the percentage of body fat (35.9%); In general they do not report adverse gastrointestinal symptoms: 61.5% with feces formed, 53.8% without abdominal pain, 84.6% without steatorrhea; Adequacy in macronutrient consumption: 51.3% adequate consumption of carbohydrates and lipids, and 64.1% excessive consumption of proteins; Positive correlations: enzyme dose correlates with pain (p = 0.004) and BMI (p = 0.009); that is, patients who report more pain and who weigh more are those who receive the highest doses of pancreatic enzymes; Negative correlations: functional capacity and nutritional assessment parameters such as BMI (p = 0.004), and body fat percentage (p = 0.028), as well as clinical parameters such as enzyme dose (p = 0.022) and number of bowel movements per day p=0.024); Associations: the dietary lipid consumption inadequacy is associated with important gastrointestinal symptoms such as soft stool consistency (p=0.005) and flatulence (p=0.012), and emphasizes the importance of nutritional guidance to patients on pancreatic enzyme replacement therapy. CONCLUSION: Most patients presented good results of biochemical tests, quality of life, macronutrient consumption, nutritional status and gastrointestinal symptoms. Significant correlations and associations have been observed that evidence that nutritional status, food intake and enzyme dose interferes with gastrointestinal symptoms and self-perceived quality of life of patients. Therefore, the current protocol is valid, but should be associated with individualized nutritional guidance

Au cours de ce travail, nous nous sommes attachés à étudier certaines réponses cellulaires secondaires à l’activation des récepteurs purinergiques P2X dans deux modèles différents, les macrophages péritonéaux et les cellules des glandes sous-maxillaires. Ces cellules contribuent à notre immunité innée, soit tournée vers l’intérieur (macrophages), soit vers l’extérieur (glandes sous-maxillaires).<p><p>Nous avons dans un premier temps confirmé par Western blot et par des dosages de la concentration intracellulaire de calcium ([Ca2+]i) que les deux types de cellules étudiés expriment des récepteurs P2X4 et P2X7 fonctionnels.<p><p>Nous nous sommes alors concentrés sur deux réponses impliquées dans la protection de l’hôte contre les agressions et l’élimination de pathogènes :la production d’espèces réactives de l’oxygène (ROS) ainsi que la sécrétion de la cytokine pro-inflammatoire interleukine-1beta (IL-1beta). Nos résultats montrent que la production de ROS en réponse à l’ATP extracellulaire est secondaire à l’activation d’une NADPH oxydase dans les deux types de cellules. Cette réponse est médiée par les récepteurs P2X7 ainsi que, dans les macrophages, par d’autres récepteurs purinergiques comme par exemple les récepteurs P2X4 et des récepteurs P2Y. Dans les glandes exocrines, contrairement aux macrophages, la protéine kinase C ainsi que ERK1/2 interviennent dans l’activation de la NADPH oxydase. <p><p>Par la suite nous avons comparé la régulation de l’expression et de la sécrétion d’IL-1beta par les macrophages et les glandes sous-maxillaires. Nous avons observé que l’IL-1beta est présente dans la salive collectée chez des souris injectées par de la pilocarpine. Des analyses par ELISA, RT-PCR et Western blot montrent que la cytokine est exprimée de manière constitutive par les cellules acineuses et ductales des glandes sous-maxillaires, à un niveau plus élevé que dans les macrophages. Contrairement aux cellules phagocytaires, l’expression de la cytokine dans les cellules des glandes salivaires n’est pas augmentée suite à la stimulation par des lipopolysaccharides. De même, dans ces cellules l’ATP n’a pas provoqué la sécrétion d’IL-1beta malgré l’efflux de K+ secondaire à l’activation des récepteurs P2X7. <p><p>Dans une dernière série d’expériences nous avons évalué les effets du peptide antimicrobien CRAMP sur les macrophages murins. Le CRAMP a inhibé toutes les réponses secondaires à l’activation des récepteurs P2X7 (ouverture du canal cationique, formation de pore, production de ROS, libération d’IL-1beta, d’acide oléique et de lactate déshydrogénase). L’inhibition par le CRAMP de l’augmentation de la [Ca2+]i en réponse à l’ATP n’était pas médiée par les récepteurs aux peptides formylés car les agonistes de ces récepteurs n’ont pas bloqué cette augmentation. Le CRAMP n’a pas eu d’effet sur l’augmentation de la [Ca2+]i secondaire à l’activation des récepteurs P2X4 par une combinaison d’ATP et d’ivermectine.<p><p>Nos expériences ont révélé que les récepteurs P2X7 sont couplés à diverses voies de signalisation dans les macrophages et dans les glandes exocrines. Les voies activées diffèrent en fonction du type de cellules. Nous avons également conclu que les peptides antimicrobiens de la famille de cathélicidines ne sont pas des agonistes universels des récepteurs P2X7.<p><p><p><p><p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Einleitung: Vor mehr als 3 Jahrzehnten zeigten mehrere Untersuchungen, dass bei Patienten mit terminaler Niereninsuffizienz in bis zu 60% der Fälle eine mit dem Sekretin-Pancreozymin-Test (SPT) oder eine seiner Modifikationen nachweisbare Pankreasinsuffizienz (EPI) vorliegt. Da der SPT weltweit kaum noch zur Verfügung steht, wurde untersucht, ob und wie häufig mit der fäkalen Elastase-1- Messungeine EPI bei Hämodialyse-(HD)-Patienten nachweisbar ist. Methodik: Die Studie umfasste 50 HD-Patienten, bei denen die fäkale Elastase-1 mit zwei verschiedenen Methoden (Bioserv Diagnostics und Schebo-Biotech) bestimmt und außerdem das Stuhlgewicht und der Stuhlfettgehalt ermittelt wurden. Bei keinem der Patienten bestand in der Vorgeschichte eine akute oder chronische Pankreatitis bzw., eine chronisch-entzündliche Darmerkrankung. Ebenso lag kein Zustand nach Teil- Gastrektomie bzw., Teil-Dünndarmresektion vor. Ergebnis: Eine EPI leichten Grades (100 - 200 µg/g Stuhl) wurde bei 5 (10%) Patienten festgestellt. Sie korrelierte nicht mit Alter, Geschlecht, nephrologischer Grunderkrankung und HD-Dauer. In keinem Fall war eine Pankreasenzymsubstitution (< 100 µg/g Stuhl) erforderlich. Bei 9 (18%) Patienten lag eine leichte Diarrhoe (200 - 300 g/Tag) vor, bei 10 (20%) eine Steatorrhoe leichten Grades (7 - 15 g Fett/ Tag). Die Steatorrhoe war bei 6 (67%) bzw. 5 (50%) dieser Patienten durch die gleichzeitige Gabe eines Phosphatbinders (Gallensäurebindung) erklärbar. Schlussfolgerung: Anders als früher scheint jetzt eine EPI ein seltenes und klinisch nicht bedeutsames Problem bei HD-Patienten zu sein. Dies ist möglicherweise dadurch zu erklären, dass jetzt ausreichend Dialyseplätze zur Verfügung stehen und Patienten mit terminaler Niereninsuffizienz in noch gutem Allgemein- und Ernährungszustand in ein Dialyseprogramm aufgenommen werden können. Ob die ebenfalls seltene, aber zunächst klinisch nicht erklärbare Diarrhoe/Steatorrhoe klinisch von Bedutung (Osteoporose?) ist, müssen weitere Untersuchungen zeigen.

Les enzymes lipolytiques sont solubles en phase aqueuse mais hydrolysent des substrats insolubles. Leurs activités lipolytiques dépendent donc fortement de l’organisation des substrats lipidiques présents sous forme de structures interfaciales telles que des émulsions, des micelles, des liposomes, ou des bicouches lipidiques. Les propriétés cinétiques et la spécificité de substrat de ces enzymes résultent de l’étape initiale d’adsorption à l’interface lipide-eau et des interactions entre le substrat et le site actif. Dans le cadre de ce travail de thèse, la technique des films monomoléculaires a été utilisée pour étudier en détail les étapes séquentielles d’adsorption, de catalyse et d’inhibition de l’enzyme à l’interface lipide-eau. Dans une première partie, nous avons réalisé la caractérisation physico-chimique de la lipase gastrique de chien (DGL), avec l’étude :  de son adsorption sur un film non substrat de dilauroylphosphatidylcholine ; ‚ de l’hydrolyse interfaciale de la 1,2-dicaprine dans des films mixtes en présence d’Orlistat. Concernant l’étape de catalyse, nous avons étudié l’effet du propeptide sur la spécificité de substrat et l’activité interfaciale de la phospholipase A2 sécrétée de groupe X de souris. Enfin, dans une troisième partie, nous avons comparé les propriétés interfaciales de la lipase YLLIP2 de la levure Yarrowia lipolytica qui serait un bon candidat pour l’enzymothérapie de substitution chez les patients atteints d’insuffisance pancréatique exocrine (IPE), la lipase pancréatique humaine et la DGL. Nos résultats ont confirmé le rôle d’YLLIP2 en tant qu’excellent « substitut » non seulement de la HPL en cas d’IPE, mais aussi de la DGL. / Lipolytic enzymes are water-soluble whereas their substrates are insoluble in water. Their lipolytic activities depend strongly on the organization of the lipid substrates present in interfacial structures such as oil-in-water emulsions, micelles, liposomes, and membrane bilayers. The kinetic properties and substrate specificity of these enzymes result from both their adsorption at the lipid-water interface, and the interactions occurring between the substrate and the active site. In this thesis work, the monomolecular film technique was used to study in details the sequential steps of adsorption, catalysis and inhibition of model enzymes at the lipid-water interface. In a first part, we performed the physico-chemical characterization of the dog gastric lipase (DGL), by studying:  its adsorption onto a dilauroylphosphatidylcholine non-substrate film; ‚ its interfacial hydrolysis of 1,2-dicaprin in mixed films with various amounts of Orlistat. Regarding the catalysis step, we studied the effect of the propeptide on the substrate specificity and interfacial activity of the murine group X secreted phospholipase A2. A model of this enzyme with its propeptide was built from the available 3D structure of the corresponding mature human enzyme. Finally, in the third part, we compared the interfacial kinetic properties of YLLIP2 lipase of the yeast Yarrowia lipolytica which has been identified as a good candidate for enzyme replacement therapy for patients with exocrine pancreatic insufficiency (EPI), human pancreatic lipase and DGL. Our results confirmed the role of YLLIP2 as an excellent "substitute" not only for HPL in case of PEI, but also for the DGL at acidic pH values.

Tot i que es coneix l’involucrament de les cèl·lules pancreàtiques acinars en patologies exocrines (pancreatitis i càncer de pàncrees), la manca de models normals basats en cèl·lules ha limitat l’estudi de les alteracions que succeeixen en el programa de diferenciació pancreàtica. Hem demostrat prèviament que les cèl·lules mare embrionàries murines, que són pluripotents, poden adquirir un fenotip acinar in vitro. Això es va aconseguir, en part, amb una combinació de senyals que provenien del cultiu de pàncrees fetals que no era, però, específic del llinatge pancreàtic. L’objectiu d’aquest treball ha estat el de desenvolupar un protocol selectiu pel llinatge acinar basat en l’activació seqüencial de vies de senyalització que recapitulin el desenvolupament pancreàtic in vivo, a través de la formació definitiva de l’endoderm, l’especificació pancreàtica i acinar i l’expansió/diferenciació de progenitors acinars. El tractament de cossos embrionaris amb Activina A va promoure l’expressió de gens d’endoderm com està prèviament descrit. El tractament subsegüent amb àcid Retinoic, FGF10 i Ciclopamina, un inhibidor de la via de Hedgehog, va resutar en la inducció dels marcadors de progenitors pancreàtics Pdx1, Ptf1a i Cpa1 però també d’aquells expressats en el llinatge pancreàtic, que van ser reduïts amb la inhibició de BMPs. Les cèl·lules van ser a continuació cultivades en Matrigel utilitzant un sistema de cultiu en 3D en presència de fol·listatina, dexametasona i KGF comportant una inducció significativa dels nivells de mRNA i proteïna de marcadors acinars i una disminució de l’expressió dels de marcadors acinars. A més, es va veure que Amyl es secretava en el medi. Aquestes dades indiquen que l’activació selectiva del programa de diferenciació acinar en cèl·lules mare embrionàries es pot dur a terme mitjançant una inducció esgraonada de vies de senyalització involucrades en el desenvolupament pancreàtic exocrí proporcionant una eina potencial per estudiar la diferenciació pancreàtica i malalties relacionades amb el pàncrees. / Despite known involvement of pancreatic acinar cells in exocrine pathologies (pancreatitis and pancreatic cancer), the lack of normal cell-based models has limited the study of the alterations that occur in the acinar differentiation program. We have previously shown that mESC (murine embryonic stem cells), which are pluripotent, can acquire an acinar phenotype in vitro. This was achieved, in part, by a combination of signals provided by the culture of foetal pancreases which was, however, no specific for the acinar lineage. The aim of this work was to develop a protocol selective for the acinar lineage based on the sequential activation of signaling pathways that recapitulate pancreatic development in vivo, through the definitive endoderm formation, the pancreatic and acinar specification and the expansion/differentiation of acinar progenitors. Treatment of embryoid bodies with Activin A enhanced the expression of endodermal genes as previously described. Subsequent treatment with Retinoic acid, FGF10 and Cyclopamine, an inhibitor of the Hedgehog pathway, resulted in the enhancement of pancreatic progenitor markers Pdx1, Ptf1a and Cpa1 but also of those expressed in the hepatic lineage, which were reduced by BMPs inhibition. Cells were further cultured in Matrigel using a 3D culture system in the presence of follistatin, dexamethasone, and KGF leading to a significant enhancement of the mRNA and protein levels of acinar markers while decreasing the expression of endocrine ones. Moreover, active Amyl was released into the medium. These data indicate that the selective activation of the acinar differentiation program in ES cells can be achieved by stepwise induction of signaling pathways involved in pancreatic exocrine development providing a potential tool for studying pancreatic differentiation and pancreas-related diseases.

Diabetes mellitus (DM) is a severe and frequent disease with increasing prevalence. It is not possible to achieve long term cure without late complications. Recent advances in cell fate modifications open a pathway to alternative cell therapies for DM cure. My doctoral thesis "Differentiation of pancreatic stem cells into insulin producing β- cells" is focused on the development of a new source of insulin secreting cells for transplantation. Combinatorial testing of numerous potential transcription factors and epigenetic modifiers resulted in a final protocol for the reprogramming pancreatic of exocrine cells into insulin secreting cells. The key transcriptional factors TF (Pdx1, Ngn3 a MafA) were applied in the form of synthetic mRNA. In four independent experiments we applied transcriptional factors in a specific sequence, thus obtaining 14.3 ± 1.9 % insulin positive cells. When challenged in vitro by the glucose levels of 2.5 and 20 mmol/l glucose, respectively, these cells exhibited glucose-sensitivity of insulin secretion (842 ± 72 and 1 157 ± 58 pg insulin/µg DNA/ml, n=5). They also demonstrated a sensitivity of insulin secretion (863 ± 78 and 1 025 ± 66 pg insulin/µg DNA/ml, n=5) to the concentration of depolarization agent KCl applied at 0 and 30 mmol/l, respectively together with 2.5...

Indiana University-Purdue University Indianapolis (IUPUI) / Type I diabetes is an autoimmune disorder characterized by the loss of insulin producing islet cell mass. While daily insulin injection provides an easy means of glycemic control, it does not prevent long-term complications associated with diabetes. Islet transplantation has been suggested as a permanent cure for type 1 diabetes. However, the recurrence of host immunity and shortage of donor islets hinder the prevalence of islet transplantation. Biomaterial strategies provide an alternative route to solving the problems associated with host immune response and shortage of donor islets. One highly recognized platform for achieving these goals are hydrogels, which are hydrophilic crosslinked polymers with tissue-like elasticity and high permeability. Hydrogels prepared from poly(ethylene glycol) (PEG) derivatives are increasingly used for a variety of tissue engineering applications, including encapsulation of pancreatic islets and serving as a material platform for pseudo-islet differentiation. PEG hydrogels formed by mild and rapid thiol-ene photo-click reactions are particularly useful for studying cell behaviors in three-dimension (3D). Thiol-ene PEG-based hydrogels can be rendered biodegradable if appropriate macromer and cross-linker chemistry is employed. However, the influence of hydrogel matrix properties on the survival, growth, and morphogenesis of cells in 3D has not been fully evaluated. This thesis aims at using norbornene-functionalized PEG macromers to prepare thiol-ene hydrogels with various stiffness and degradability, from which to study the influence of hydrogel properties on pancreatic cell fate processes in 3D. Toward establishing an adaptable hydrogel platform for pancreatic tissue engineering, this thesis systematically studies the influence of hydrogel properties on encapsulated endocrine cells (e.g., MIN6 beta-cells) and exocrine cells (PANC-1 cells), as well as human mesenchymal stem cells (hMSC). It was found that thiol-ene photo-click hydrogels provide a cytocompatible environment for 3D culture of these cells. However, cell viability was negatively affected in hydrogels with higher cross-linking density. In contrast to a monolayer when cultured on a 2D surface, cells with epithelial characteristic formed clusters and cells with mesenchymal features retained single cell morphology in 3D. Although cells survived in all hydrogel formulations studied, the degree of proliferation, and the size and morphology of cell clusters formed in 3D were significantly influenced by hydrogel matrix compositions. For example: encapsulating cells in hydrogels formed by hydrolytically degradable macromer positively influenced cell survival indicated by increased proliferation. In addition, when cells were encapsulated in thiol-ene gels lacking cell-adhesive motifs, hydrolytic gel degradation promoted their survival and proliferation. Further, adjusting peptide crosslinker type and immobilized ECM-mimetic bioactive cues provide control over cell fate by determining whether observed cellular morphogenesis is cell-mediated or matrix-controlled. These fundamental studies have established PEG-peptide hydrogels formed by thiol-ene photo-click reaction as a suitable platform for pancreatic tissue engineering