Les cellules souches hématopoïétiques (CSH) sont rares, mais indispensables pour soutenir la production des cellules matures du sang, un tissu en constant renouvellement. Deux caractéristiques principales les définissent; la propriété d’auto-renouvellement (AR), ou la capacité de préserver leur identité cellulaire suivant une division, et la multipotence, ce potentiel de différentiation leur permettant de générer toutes les lignée hématopoïétiques. De par leurs attributs, les CSH sont utilisée en thérapie cellulaire dans le domaine de la transplantation. Une organisation tissulaire hiérarchique est aussi préservée dans la leucémie, ou cancer du sang, une masse tumorale hétérogène devant être maintenue par une fraction de cellules au potentiel prolifératif illimité, les cellules souches leucémiques (CSL). Les travaux présentés dans ce manuscrit visent à explorer les bases moléculaires de l’AR, encore mal définies. Certains membres de la famille des facteurs de transcription à homéodomaine HOX sont impliqués dans la régulation de l’hématopoïèse normale, et leur dérégulation peut contribuer à la transformation leucémique. En particulier, la surexpression du gène Hoxb4 dans les CSH influence leur destin cellulaire, favorisant des divisions d’auto-renouvellement et leur expansion en culture et in vivo. En général, les CSH s’épuisent rapidement lorsque maintenue hors de leur niche ex vivo. Différents facteurs interagissent avec les HOX et modulent leur liaison à l’ADN, dont la famille des protéines TALE (Three Amino acid Loop Extension), comme MEIS1 et PBX1. En utilisant une stratégie de surexpression combinée de Hoxb4 et d’un anti-sens de Pbx1 dans les CSH, générant ainsi des cellules Hoxb4hiPbx1lo, il est possible de majorer encore d’avantage leur potentiel d’AR et leur expansion in vitro. Les CSH Hoxb4hiPbx1lo demeurent fonctionnellement intactes malgré une modulation extrême de leur destin cellulaire en culture. Les niveaux d’expressions de facteurs nucléaires, seules ou en combinaison, peuvent donc s’avérer des déterminants majeurs du destin des CSH. Afin d’identifier d’autres facteurs nucléaires potentiellement impliqués dans le processus d’AR des CSH, une stratégie permettant d’évaluer simultanément plusieurs gènes candidats a été élaborée. Les progrès réalisés en termes de purification des CSH et de leur culture en micro-puits ont facilité la mise au point d’un crible en RNAi (interférence de l’ARN), mesurant l’impact fonctionnel d’une diminution des niveaux de transcrits d’un gène cible sur l’activité des CSH. Les candidats sélectionnés pour cette étude font partie du grand groupe des modificateurs de la chromatine, plus précisément la famille des histones déméthylases (HDM) contenant un domaine catalytique Jumonji. Ce choix repose sur la fonction régulatrice de plusieurs membres de complexes méthyl-transférases sur l’AR des CSH, dont l’histone méthyl-transférases MLL (Mixed Lineage Leukemia). Cette stratégie a aussi été utilisée dans le laboratoire pour étudier le rôle de facteurs d’asymétrie sur le destin des CSH, en collaboration. Ces études ont permis d’identifier à la fois des régulateurs positifs et négatifs de l’activité des CSH. Entre autre, une diminution de l’expression du gène codant pour JARID1B, une HDM de la lysine 4 de l’histone H3 (H3K4), augmente l’activité des CSH et s’accompagne d’une activation des gènes Hox. En conclusion, divers déterminants nucléaires, dont les facteurs de transcription et les modificateurs de la chromatine peuvent influencer le destin des CSH. Les mécanismes sous-jacents et l’identification d’autres modulateurs de l’AR demeurent des voies à explorer, pouvant contribuer éventuellement aux stratégies d’expansion des CSH ex vivo, et l’identification de cibles thérapeutiques contre les CSL. Mots-clés : cellules souches hématopoïétiques, Hoxb4, Pbx1, auto-renouvellement, histone déméthylases, RNAi / Hematopoietic stem cells (HSC) are rare, but essential to sustain the constant production of all mature blood cells, a constantly renewing tissue. They are defined by two main characteristics; namely self-renewal (SR), or the capacity to preserve cell identity following division, and multipotency, the differentiation potential that allows them to generate all hematopoietic lineages. Given their attributes, HSC are used for cellular therapy in the transplantation field. A hierarchy in tissue organisation is also preserved in leukemia, or blood cancer, a heterogeneous tumor mass that is sustained by a subset of cells with unlimited SR potential, the leukemia stem cells (LSC). Studies presented in this manuscript aim to explore the molecular basis underlying SR, which are still poorly defined. Certain members of the HOX family of homeodomain transcription factors are involved in the regulation of normal hematopoiesis, and their deregulation can contribute to leukemia development. In particular, Hoxb4 overexpression in HSC influences cells fate, favouring SR divisions and their subsequent expansion in culture and in vivo. In general, HSC exhaust rapidly when maintained ex vivo, outside of their niche. Several factors interact with HOX and modulate their binding to DNA, including members of the TALE (Three Amino acid Loop Extension) protein family, such as MEIS1 and PBX1. Using a strategy of combined overexpression of Hoxb4 and an anti-sense to Pbx1in HSC, generating Hoxb4hiPbx1lo cells, it is possible to further impact on their SR potential and expansion in vitro. These Hoxb4hiPbx1lo cells remain functionally intact despite extreme modulation of their cell fate in culture. Levels of expression of nuclear factors, alone or in combination, can thus impact significantly on HSC fate. In order to identify other nuclear factors potentially involved in the process of HSC self-renewal, a strategy enabling simultaneous assessment several gene candidates was elaborated. To this end, progress made in terms of HSC purification and their culture in micro-wells facilitated the setup of an RNAi (RNA interference) screen, measuring the functional impact of lowering gene candidate transcript levels on HSC activity. Gene candidates selected for this study belong to the greater group of chromatin modifiers, more specifically the family of histone demethylases (HDM) containing a Jumonji catalytic domain. This choice stems from the regulatory function of several members of histone methyl-transferase complexes on HSC self-renewal, including the histone methyl-transferase MLL (Mixed Lineage Leukemia). This strategy was also used in the laboratory to study the role of asymmetry factors on HSC fate, in a collaborative study. These studies enabled identification of both positive and negative regulators of HSC activity. Among these, reduced expression of the gene coding for JARID1B, a histone 3 lysine 4 (H3K4) HDM, increased HSC activity was associated with Hox genes activation. In conclusion, several nuclear determinants, including transcription factors and chromatin modifiers, can influence HSC fate. Underlying mechanisms and identification of additional modulators of SR remain areas to explore, which could eventually contribute to HSC expansion strategies ex vivo, and identification of therapeutic targets against LSC. Keywords: hematopoietic stem cells, Hoxb4, Pbx1, self-renewal, histone demethylases, RNAi

Muscle aging is associated with a decrease in the number of satellite cells and their progeny, muscle progenitor cells (MPCs) that are available for muscle repair and regeneration. However, there is an increase in non-immuno-hematopoietic cells (CD45 negative) in regenerating muscle from aged mice characterized by high stem cell antigen -1(Sca-1) expression. In aged regenerating muscle, 14.2% of cells are CD45neg Sca-1pos while 7.2% of cells are CD45neg Sca-1pos in young adult muscle. In vitro, CD45neg Sca-1pos cells over express genes associated with fibrosis, potentially controlled by Wnt2. These cells are proliferative, non-myogenic and non-adipogenic, and arise in clonally-derived MPCs cultures from aged mice. Both in vitro and in vivo studies suggest that CD45neg Sca-1pos cells from aged muscle are more susceptible to apoptosis than their MPCs, which may contribute to depletion of the satellite cell pool. Therefore, with age, a subset of MPCs takes on an altered phenotype, which is marked by high Sca-1 expression. This altered phenotype prevents these cells from participating in muscle regeneration or replenishing the satellite cell pool, and instead may contribute to fibrosis in aged muscle.

Prominin-1 (alias CD133) has received considerable interest because of its expression by several stem and progenitor cells originating from various sources, including the neural and hematopoietic systems. As a cell surface marker, prominin-1 is now used for somatic stem cell isolation. Its expression in cancer stem cells has broadened its clinical value, as it might be useful to outline new prospects for more effective cancer therapies by targeting tumor-initiating cells. Cell biological studies of this molecule have demonstrated that it is specifically concentrated in various membrane structures that protrude from the planar areas of the plasmalemma. Prominin-1 binds to the plasma membrane cholesterol and is associated with a particular membrane microdomain in a cholesterol-dependent manner. Although its physiological function is not yet determined, it is becoming clear that this cell surface protein, as a unique marker of both plasma membrane protrusions and membrane microdomains, might reveal new aspects of the cell biology of rare stem and cancer stem cells. The aim of this review is to outline the recent discoveries regarding the dynamic reorganization of the plasma membrane of rare CD133+ hematopoietic progenitor cells during cell migration and division. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

The bone marrow (BM) niche provides hematopoietic stem (HSC) and progenitor cells with many exogenous cues that tightly regulate homeostasis. These cues orchestrate cellular decisions, which are difficult to dissect and analyze in vivo. This thesis introduces a novel in vitro platform that permits systematic studies of BM-relevant factors that regulate homeostasis. Specifically, the role of 3D patterned adhesion ligands and soluble cytokines were studied in a combinatorial fashion. Analysis of human HSC differentiation and proliferation at both population and single cell level showed synergistic and antagonistic effects of adhesion- and cytokine-related signals. Those effects were dependent on the cytokine concentration and the distribution and number of adhesion ligands. The aim of this thesis was to model the in vivo bone marrow with its porous 3D structure and different sized niche compartments using a microcavity culture carrier. The developed culture system presented extracellular matrix (ECM) adhesion ligands to the HSCs in various defined dimensions ranging from single- to multi-cell capacity. The 3D open well geometry of the microcavity carriers also allowed HSCs to freely explore different scenarios including homing, migration, adhesion, or suspension. Furthermore, the developed setup offered straightforward accessibility to analytical methods like cytometry and quantitative microscopy. Single cell analysis of adherent HSCs showed decreased DNA synthesis and higher levels of stem cell marker expression within single cell microcavities under low cytokine conditions . This effect was reflected in a decline of proliferation and differentiation with decreasing microcavity size. When the cytokine concentration was increased2 beyond physiological levels the inhibitory effect on proliferation and differentiation due to single-cell-microcavity adherence was diminished. This result highlighted the fine balance between adhesion related and soluble cues regulating HSC fate. Within small microcavities more adhesion related receptors were engaged due to the 3D character of the culture carrier compared to multi-cell wells or conventional 2D cell culture plates. This study demonstrated that adhesion-related signal activation leads to reduced proliferation and differentiation. This geometry-based effect could be reversed by increased cytokine supplementation in the culture media. For plane substrates, HSCs attachment to fibronectin or heparin initiated early cell cycle entry compared to non-adherent cells during the initial 24h. Cytokine supplemented media favored integrin activation that induced fast adhesion, ultimately leading to early cell cycle activation. However, after prolonged cell culture the system balanced itself with a lower cycling rate of adherent versus non-adherent HSCs. Furthermore, HSCs within the 3-dimensionality of the microcavities cycled less than 2D adherent cells. These findings additionally supported the above stated idea of limited HSC proliferation as a consequence of more adhesion-related signals overwriting cytokine driven expansion. To complement the various in vitro studies, an in vivo repopulation study was performed. Cultured HSCs derived from single cell microcavities outperformed freshly isolated HSCs in a competitive repopulation assay, indicating that carefully engineered substrates are capable of preserving stem cell potential. Overall the reported findings provide a promising in vitro culture strategy that allows the stem cell field to gain a better understanding of the impact of distinct exogenous signals on human HSCs, which discloses new concepts for the wide scientific community working towards tissue engineering and regenerative medicine. / Die Homöostase der Hämatopoietischen Stamm- und Vorläuferzellen (HSC) in der Knochenmark Nische wird von einer Vielzahl exogener Faktoren gezielt reguliert. Diese Faktoren orchestrieren intrazelluläre Vorgänge, deren in vivo Analyse kompliziert ist. Die vorliegende These widmet sich einem neuen biotechnologischen Ansatz, der systematische Studien von Knochenmark-relevanten Faktoren ermöglicht. Im Speziellen wurde die Rolle 3D-präsentierter Zell Adhäsionsliganden in Kombination mit verschiedenen Konzentrationen löslicher Zytokine untersucht. Die Auswertung der Proliferation und Differenzierung von humanen HSC auf Einzelzell- und Populationsebene offenbarte die synergistischen und antagonistischen Effekte von Adhäsions- und Zytokinsignalen in ihrer Abhängigkeit von der Verteilung und der Anzahl von Adhäsionsliganden sowie der Zytokinkonzentration. Um die poröse Struktur des Knochenmarks in vivo-ähnlich darzustellen, wurde eine Zellkultur Plattform mit Mikrokavitäten verschiedenster Dimensionen von Multi- bis Einzelzellgröße entwickelt und mit Molekülen der extrazellulären Matrix beschichtet. Die Vorteile dieser Plattform liegen in der offenen 3D-Geometrie dieses mikrokavitäten Kultursystems, die den Zellen ermöglichte verschiedene Wachstumsbedingungen bezüglich Homing, Migration, Adhäsion oder Suspension frei zu erkunden. Das leicht zugängliche Setup eignete sich zudem hervorragend für die zytometrische Analyse der Zellen oder die quantitative Mikroskopie. Die Einzelzellanalyse adhärenter HSC ergab eine Reduktion von DNA Synthese und eine höhere Expression von Stammzelloberflächenfaktoren innerhalb der Einzelzell-Mikrokavitäten bei niedrigen Zytokinkonzentrationen . Dieser Effekt spiegelte sich auch auf Populationsebene in verminderter Proliferation und Differenzierung mit abnehmender Größe der Mikrokavitäten wider. Wurde die Zytokinkonzentration jedoch weit über physiologische Bedingungen erhöht, verminderte sich der Effekt (reduzierte DNA Synthese und höhere Stammzellfaktorexpression) beschrieben für die Einzelzellmikrokavitäten. Dieses Ergebnis verdeutlicht die empfindliche intrazelluläre Balance, vermittelt durch Adhäsionsignale und löslichen Faktoren, die das Verhalten von HSCs regulieren. Aufgrund des 3D-Charakters des Zellkulturträgers wurden innerhalb kleiner Mikrokavitäten mehr Adhäsionsrezeptoren ringsum die Zelle aktiviert. Dieser Vorteil gegenüber den Multizellkavitäten oder der herkömmlichen 2D–Zellkultur ermöglichte eine hohe Anzahl adhäsionsvermittelter Signale mit entsprechend höherer Proliferations-inhibitorischer Wirkung. Je höher die Konzentration der Zytokine war, desto stärker erfolgte die Stimulation der Proliferation und Differenzierung. Auf 2D Substraten, initiierte Adhäsion zu Fibronektin und Heparin innerhalb der ersten 24h einen frühen Zell-Zyklus-Start im Gegensatz zu nicht adhärenten Zellen. Die Zytokine im Zellmedium förderten die Integrin Aktivierung, was zu einer schnellen Zelladhäsion führte. Die Adhäsionsrezeptoren wiederum kooperieren mit Zytokinrezeptoren im Zellinneren und begünstigten damit einen zeitigeren Zell-Zyklus- Start. Allerdings stellte sich danach ein Gleichgewicht im Kultursystem ein, wobei weniger adhärente Zellen als nicht-adhärente Zellen den Zellzyklus durchliefen. Des Weiteren war die Zellzyklusrate innerhalb von 3D Mikrokavitäten niedriger verglichen mit herkömmlichen 2D Substraten. Diese Ergebnisse bestätigen ferner obenstehende These, dass Zytokin-induzierte Zellexpansion durch erhöhte Zelladhäsions-vermittelte Signale überschrieben wird. Um die in vitro Studien zu komplettieren wurde ein in vivo Repopulationsversuch durchgeführt. HSC kultiviert auf Einzel-Zell-Mikrokavitäten übertrafen frisch isolierte Konkurrenz-Zellen in einem kompetitiven Repopulationsversuch. Dieses erste Ergebnis zeigt, dass sich der Zellgröße entsprechende Biomaterialien für die erfolgreiche Stammzell-Kultur eignen. Die Ergebnisse dieser Arbeit bieten eine vielversprechende in vitro Zellkulturstrategie, die ein besseres Verständnis der Einflüsse von exogenen Signalen auf HSC erlaubt und damit eine Grundlage für neue Erkenntnisse in Richtung erfolgreicheres Tissue Engineering und klinische Anwendungen im Bereich der regenerativen Medizin bildet.

Diss. (sammanfattning) Umeå : Univ., 2008. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 6 uppsatser.

Source: Dissertation Abstracts International, Volume: 70-07, Section: B, page: 4063. Adviser: David R. Lairson. Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Bruce R. Locke, Florida State University, FAMU-FSU College of Engineering, Dept. of Chemical and Biomedical Engineering. Title and description from dissertation home page (viewed Jan. 12, 2006). Document formatted into pages; contains xix, 250 pages. Includes bibliographical references.

A mucosite bucal (MB) é uma complicação comum no tratamento do câncer e o desenvolvimento de intervenções efetivas para sua prevenção e tratamento são vistos como prioridade nos cuidados de suporte ao paciente oncológico. O objetivo do presente estudo foi investigar fatores de risco relacionados à incidência de mucosite bucal em pacientes submetidos a transplante de células progenitoras hematopoiéticas (TCPH) e em pacientes oncológicos pediátricos. Foram realizados dois estudos: o primeiro analisando a relação entre a incidência de mucosite bucal e o estado de saúde bucal, neutropenia, leucopenia e níveis de IL-1β em pacientes submetidos ao TCPH; e, o segundo, avaliando a incidência de mucosite bucal em pacientes oncopediátricos submetidos a diferentes protocolos quimioterápicos e sua relação com toxicidade hematológica, hepática e renal. Estudo 1: Foram avaliados 54 pacientes submetidos ao TCPH coletados dados demográficos e de à história médica foram coletados. Todos os pacientes foram avaliados quanto a saúde bucal através da análise do índice de placa (IP), índice gengival (IG), número de dentes cariados, perdidos e obturados (CPOD) e exame da mucosa bucal. Todos os pacientes receberam tratamento dentário e orientações de higiene bucal prévio bem como, fotobiomodulação (FBM) com laser de diodo InGaAlP como protocolo preventivo para mucosite bucal. Os pacientes foram avaliados diariamente desde o condicionamento ate o final do transplante. Avaliações de mucosite bucal, níveis de neutrófilos e leucócitos e análise de IL-1β foram realizados nos períodos de condicionamento, D+3 e D+8. Os pacientes que apresentaram gengivite severa anterior ao condicionamento para o transplante e que apresentaram neutropenia grave e leucopenia mostraram associação com o desenvolvimento OM. Os pacientes com mucosite bucal apresentaram níveis mais baixos de IL-1β. Estudo 2: Foram acompanhados 172 ciclos de quimioterapia realizados em 40 pacientes pediátricos. Dados de toxicidade hematológica (níveis de plaquetas, leucócitos, neutrófilos e hemoglobina), hepática (níveis de bilirrubina, TGO, TGP) e renal (creatinina e uréia) nos períodos D1, D5, D10 e D15 foram coletados. Avaliação do grau de mucosite bucal foi realizado diariamente a partir de D1 até D15. Os pacientes que desenvolveram mucosite receberam FBM 3 vezes por semana como tratamento. Os resultados mostraram que a mucosite bucal em pacientes oncológicos pediátricos tem relação com o tipo de protocolo quimioterápico utilizado, com a diminuição nos níveis de plaquetas, leucócitos e hemoglobina bem como, com o aumento dos níveis de bilirrubina. Os níveis de plaquetas e de bilirrubina podem ser considerados como fatores de risco para predizer o desenvolvimento de mucosite bucal. Conclui-se que ambos os trabalhos vieram a contribuir para a elucidação de fatores envolvidos no desenvolvimiento de mucosite bucal em pacientes submetidos ao TCPH e em pacientes oncopediátricos. / Oral mucositis (OM) is a common complication in cancer treatment. The development of effective interventions for prevention and treatment are seen as priority in supportive care cancer patients. The aim of this study was to investigate risk factors related to the incidence of oral mucositis in patients undergoing to hematopoietic stem cells transplantation (HSCT) and in pediatric oncology patients. Two studies were performed: the first analyzing the relationship between oral mucositis incidence with oral health status, neutropenia, leukopenia, and IL-1β levels in patients undergoing to HPCT; and the second, evaluating the incidence of oral mucositis in pediatric oncological patients undergoing to different chemotherapy protocols and their relationship with toxicity haematological, of liver and of kidney. Study 1: A total of 54 patients undergoing to HSCT were collected demographic data and medical history. All patients were evaluated for the oral health through plaque index (PI), gingival index (GI), number of decayed, missing and filled (DMF) and oral mucosa examination. All patients received prior dental and oral hygiene as well as photobiomodulation (PBM) InGaAlP diode laser as a preventive protocol for oral mucositis. Patients were evaluated daily from the conditioning until the end of transplantation. Reviews of oral mucositis, neutrophil ans leukocytes levels and IL- 1β analysis were performed in periods of conditioning, D+3 and D+8. Patients with previous severe gingivitis to conditioning for transplantation and who had severe neutropenia and leukopenia showed association with OM development. The oral mucositis patients had lower levels of IL-1β. Study 2: Wewre analyzed a total of 172 cycles of chemotherapy conducted in 40 oncological pediatric patients. Haematological toxicity data (levels of platelets, leukocytes, neutrophils, and hemoglobin), liver (bilirubin, GOT, GPT) and renal (creatinine and urea) in the periods D1, D5, D10 and D15 were collected. oral mucositis grade evaluation was performed daily from D1 to D15. Patients who developed oral mucositis received three times a week PBM as treatment. The results showed that oral mucositis in pediatric oncology patients is related to the type of chemotherapy protocol used with the decrease in the levels of platelets, leucocytes and hemoglobin as well as with the increase of the bilirubin level. The levels of platelets and bilirubin may be considered as risk factors to predict the development of oral mucositis. We conclude that both studies contributed to the elucidation of factors involved in the development of oral mucositis in patients undergoing HSCT and pediatric oncology patients.

A mucosite bucal (MB) é uma complicação comum no tratamento do câncer e o desenvolvimento de intervenções efetivas para sua prevenção e tratamento são vistos como prioridade nos cuidados de suporte ao paciente oncológico. O objetivo do presente estudo foi investigar fatores de risco relacionados à incidência de mucosite bucal em pacientes submetidos a transplante de células progenitoras hematopoiéticas (TCPH) e em pacientes oncológicos pediátricos. Foram realizados dois estudos: o primeiro analisando a relação entre a incidência de mucosite bucal e o estado de saúde bucal, neutropenia, leucopenia e níveis de IL-1β em pacientes submetidos ao TCPH; e, o segundo, avaliando a incidência de mucosite bucal em pacientes oncopediátricos submetidos a diferentes protocolos quimioterápicos e sua relação com toxicidade hematológica, hepática e renal. Estudo 1: Foram avaliados 54 pacientes submetidos ao TCPH coletados dados demográficos e de à história médica foram coletados. Todos os pacientes foram avaliados quanto a saúde bucal através da análise do índice de placa (IP), índice gengival (IG), número de dentes cariados, perdidos e obturados (CPOD) e exame da mucosa bucal. Todos os pacientes receberam tratamento dentário e orientações de higiene bucal prévio bem como, fotobiomodulação (FBM) com laser de diodo InGaAlP como protocolo preventivo para mucosite bucal. Os pacientes foram avaliados diariamente desde o condicionamento ate o final do transplante. Avaliações de mucosite bucal, níveis de neutrófilos e leucócitos e análise de IL-1β foram realizados nos períodos de condicionamento, D+3 e D+8. Os pacientes que apresentaram gengivite severa anterior ao condicionamento para o transplante e que apresentaram neutropenia grave e leucopenia mostraram associação com o desenvolvimento OM. Os pacientes com mucosite bucal apresentaram níveis mais baixos de IL-1β. Estudo 2: Foram acompanhados 172 ciclos de quimioterapia realizados em 40 pacientes pediátricos. Dados de toxicidade hematológica (níveis de plaquetas, leucócitos, neutrófilos e hemoglobina), hepática (níveis de bilirrubina, TGO, TGP) e renal (creatinina e uréia) nos períodos D1, D5, D10 e D15 foram coletados. Avaliação do grau de mucosite bucal foi realizado diariamente a partir de D1 até D15. Os pacientes que desenvolveram mucosite receberam FBM 3 vezes por semana como tratamento. Os resultados mostraram que a mucosite bucal em pacientes oncológicos pediátricos tem relação com o tipo de protocolo quimioterápico utilizado, com a diminuição nos níveis de plaquetas, leucócitos e hemoglobina bem como, com o aumento dos níveis de bilirrubina. Os níveis de plaquetas e de bilirrubina podem ser considerados como fatores de risco para predizer o desenvolvimento de mucosite bucal. Conclui-se que ambos os trabalhos vieram a contribuir para a elucidação de fatores envolvidos no desenvolvimiento de mucosite bucal em pacientes submetidos ao TCPH e em pacientes oncopediátricos. / Oral mucositis (OM) is a common complication in cancer treatment. The development of effective interventions for prevention and treatment are seen as priority in supportive care cancer patients. The aim of this study was to investigate risk factors related to the incidence of oral mucositis in patients undergoing to hematopoietic stem cells transplantation (HSCT) and in pediatric oncology patients. Two studies were performed: the first analyzing the relationship between oral mucositis incidence with oral health status, neutropenia, leukopenia, and IL-1β levels in patients undergoing to HPCT; and the second, evaluating the incidence of oral mucositis in pediatric oncological patients undergoing to different chemotherapy protocols and their relationship with toxicity haematological, of liver and of kidney. Study 1: A total of 54 patients undergoing to HSCT were collected demographic data and medical history. All patients were evaluated for the oral health through plaque index (PI), gingival index (GI), number of decayed, missing and filled (DMF) and oral mucosa examination. All patients received prior dental and oral hygiene as well as photobiomodulation (PBM) InGaAlP diode laser as a preventive protocol for oral mucositis. Patients were evaluated daily from the conditioning until the end of transplantation. Reviews of oral mucositis, neutrophil ans leukocytes levels and IL- 1β analysis were performed in periods of conditioning, D+3 and D+8. Patients with previous severe gingivitis to conditioning for transplantation and who had severe neutropenia and leukopenia showed association with OM development. The oral mucositis patients had lower levels of IL-1β. Study 2: Wewre analyzed a total of 172 cycles of chemotherapy conducted in 40 oncological pediatric patients. Haematological toxicity data (levels of platelets, leukocytes, neutrophils, and hemoglobin), liver (bilirubin, GOT, GPT) and renal (creatinine and urea) in the periods D1, D5, D10 and D15 were collected. oral mucositis grade evaluation was performed daily from D1 to D15. Patients who developed oral mucositis received three times a week PBM as treatment. The results showed that oral mucositis in pediatric oncology patients is related to the type of chemotherapy protocol used with the decrease in the levels of platelets, leucocytes and hemoglobin as well as with the increase of the bilirubin level. The levels of platelets and bilirubin may be considered as risk factors to predict the development of oral mucositis. We conclude that both studies contributed to the elucidation of factors involved in the development of oral mucositis in patients undergoing HSCT and pediatric oncology patients.