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<p>Radiation is a prominent source of environmental oxidative stress that can have deleterious consequences for health. Despite its well-known negative effects, radiation is commonly employed clinically for disease treatment and diagnosis. Bone marrow transplantation (BMT), used in the treatment of a variety of diseases, is preceded by a myeloablative regimen that usually involves radiation. Mortality associated with BMT is quite high and the aggressive radiation pre-treatment regimen contributes to these high rates of mortality. Interventions that inhibit the negative consequences of irradiation and promote BMT success would have significant implications for public health. Exercise-induced adaptations in numerous body tissues have been associated with amelioration of a variety of pathologies, particularly those associated with oxidative stress, and an overall improvement in health. Whether these adaptations can protect from damage induced by an external source of oxidative stress, such as a high dose of radiation, or promote BMT success is unknown. The purpose of this thesis was to determine if the adaptive response to exercise training could inhibit the negative effects of irradiation in skeletal muscle and bone marrow, and promote BMT success. To apply these adaptations to BMT, we examined the response of hematopoietic stem cells (HSC) and their niche to exercise. We report that muscle from exercise trained mice exhibits an enhanced response to radiation characterized by increased antioxidant and mitochondrial metabolic enzyme activity. Extending these findings to cells in the bone marrow, we demonstrated that exercise training inhibited radiation-induced genotoxicity and cytotoxicity. With respect to BMT, exercise training increased HSC quantity with no effects on HSC function; however, preconditioning BMT recipients with exercise training resulted in improved probability of survival and enhanced hematopoietic regeneration. Collectively, results from the studies presented herein suggest that exercise training may be a successful therapeutic intervention to inhibit the damaging effects of radiation and improve BMT outcomes.</p> / Doctor of Philosophy (PhD)

<p>Immunodeficient-causing diseases such as HIV and leukemia have no cures, often require meticulous treatments and result in high morbidity or mortality. Although bone marrow transplants are an option for a subset of leukemia patients, the shortage of donors and the requirement for donor matching restricts the efficacy of this treatment option. Therefore there is a prominent clinical need for alternative sources of hematopoietic stem/progentior cells with lymphopoietic potential. Recently we described the direct conversion of human dermal fibroblasts to multilineage hematopoietic progenitors by ectopic expression of OCT4. This direct conversion method was used to assess whether OCT4-transduced fibroblasts had the capacity to derive cells of the lymphoid lineage. This work shows the transient co-expression of CD34 and CD45 of fibroblasts within 7 days of OCT4 transduction followed by stable expression of CD45 on fibroblasts by day 15. The acquisition of hematopoietic markers, however, did not coincide with colony formation as previously described. Furthermore, CD45+ cells that were enriched and cultured in hematopoietic conducive conditions did not acquire co-expression of CD34 as previously shown. Interestingly, CD34 expression was shown to be inversely correlated with OCT4 expression. Therefore the constitutive expression of OCT4 may have (1) inhibited the acquisition of CD34 expression on CD45+ cells (2) downregulated the expression of CD34 on the day 7 CD34+CD45+ fibroblasts, thereby resulting in the transient expression of these markers. Furthermore, this work shows that expression of CD45 on OCT4-transduced fibroblasts is required for survival on the MS5 stromal cell line used to support hematopoietic progenitors with lymphopoietic potential, while supplementation of CD45+ fibroblasts with hematopoietic progenitor supportive conditions resulting in co-expression of CD34 and CD45 is required for acquisition of CD19, a pan-B cell marker on CD45+ fibroblasts. These findings suggest OCT4-transduced fibroblasts have lymphopoietic potential.</p> / Master of Science (MSc)

Mutations and deletions in ribosomal proteins are associated with a group of diseases termed ribosomopathies. Collectively, these diseases are characterized by ineffective hematopoiesis, bone marrow failure, and an increased risk of developing myelodysplastic syndrome (MDS) and subsequently acute myeloid leukemia (AML). This observation highlights the role of dysregulation of this class of proteins in the development and progression of myeloid neoplasms. Analysis of gene expression in CD34+ hematopoietic stem cells (HSC) from 183 MDS patients demonstrated that ribosomal protein L22 (Rpl22) expression exhibited a greater reduction than any other ribosomal protein gene in MDS. Interestingly, we observed that AML patients with lower expression of Rpl22 had a significant reduction in their survival (TCGA cohort, N=200, Log Rank P value&lt;0.05). To assess the mechanism of reduced expression, we developed a FISH probe complementary to the RPL22 locus and assessed for deletion of this locus in an independent set of 104 MDS/AML bone marrow samples. Strikingly, we found that RPL22 deletion was enriched in high-risk MDS and secondary AML cases. We, therefore, sought to investigate whether reduced Rpl22 expression played a causal role in leukemogenesis. Using Rpl22-/- mice, we found that Rpl22-deficiency resulted in a constellation of phenotypes resembling MDS. Indeed, Rpl22-deficiency caused a macrocytic reduction in red blood cells, dysplasia in the bone marrow, and an expansion of the early hematopoietic stem and progenitor compartment (HSPC). Since MDS has been described as a disease originating from the stem cell compartment, we next sought to determine if the hematopoietic defects were cell autonomous and resident in Rpl22-/- HSC. Competitive transplantation revealed that Rpl22-/- HSC exhibited pre-leukemic characteristics including effective engraftment, but a failure to give rise to downstream mature blood cell lineages. Importantly, there was a strong myeloid bias in those downstream progeny derived form Rpl22-/- HSC. To determine how Rpl22-deficiency increased the causes these deficiencies in HSC, we performed whole transcriptome analysis on Rpl22-/- HSC. Interestingly, alterations in genes associated with both ribosomal proteins and mitochondrial components were observed. We found that protein synthesis was unchanged in Rpl22-deficient HSCs, sharply contrasting the reductions in global protein synthesis that usually accompany ribosomal protein insufficiency. Consequently, we shifted our focus to the dysregulated mitochondrial genes, which were linked to the processes of oxidative phosphorylation and fatty acid metabolism. We observed that oxidative phosphorylation was decreased in Rpl22-deficient HSCs while fatty acid oxidation was increased. Increased fatty acid oxidation is associated with maintenance of the hematopoietic stem cells. Interestingly, inhibiting fatty acid oxidation mitigated this attribute in Rpl22 deficient HSCs. Because Rpl22 is an RNA-binding protein, we asked if Rpl22 was regulating fatty acid oxidation by directly binding mRNAs encoding regulators of fatty acid oxidation. We found that Rpl22 is able to directly bind the coding region of an upstream regulator of fatty acid oxidation, Alox12. Thus, we hypothesized that Rpl22-deficiency increased fatty acid oxidation through increased expression of Alox12. Consistent with this hypothesis, knockdown of Alox12 impaired the function of Rpl22 deficient HSC. Because the increased fatty acid oxidation promotes self-renewal of Rpl22-deficient HSC and blocks their differentiation, we also hypothesized that this would predispose them to leukemogenesis. We examined the potential for Rpl22-deficient HSPC to be transformed upon ectopic expression of the MLL-AF9 oncogenic fusion. Indeed, Rpl22 deficiency increased predisposition to transformation both in vitro and in vivo, in MLL-AF9 knockin mice. Furthermore, Rpl22 deficient leukemias were preferentially sensitive to pharmacologic inhibition of fatty acid oxidation or Alox12 knockdown, indicating that leukemia cell survival was also dependent upon fatty acid oxidation. Taken together, these findings indicate that Rpl22-insufficiency predisposes HSPC to leukemic transformation and aggressive growth by regulating mitochondrial function, providing an explanation for the reduced survival observed in Rpl22-low AML patients. We also sought to determine how Rpl22 may be contributing to another subset of AML known as Therapy-related AML. Most commonly, these patients develop AML after previously being treated with an alkylating chemotherapeutic drug. Interestingly, we found that Rpl22-deficient HSPC are resistant to treatment with these agents, despite having evidence of DNA damage. The ultimate consequence of the insensitivity of Rpl22-deficient HSPC to alkylating agents was that mice given serial doses of cyclophosphamide exhibited an increased incidence of leukemic-like changes. This chemo-resistant phenotype in Rpl22-/- cells was related to increased expression of the DNA repair protein MGMT. Inhibition of this protein abrogated the ability of these cells to survive following treatment with cyclophosphamide. Ultimately, this study implicates Rpl22 as a regulator of alkylating DNA damage repair and suggests that both patients with hematologic or solid cancers that express reduced levels of Rpl22 are at increased risk for development of therapy related AML is they are treated with alkylating agents. / Cancer Biology & Genetics

The development of the cardiovascular system, including the heart and circulating blood within a vascular network, relies on mesoderm-derived cells to contribute to the development of both cardiac and hematopoietic tissues. This dissertation focuses on exploring the roles of crip2, downstream of the transcription factor Nkx2.5 established from an RNA sequencing dataset, in cardiac and hematopoietic development using the zebrafish model. In Chapter 2, we investigate the influence of Crip proteins on the development of the zebrafish heart. Congenital heart defects (CHDs), affecting approximately 1% of live births, arise from structural anomalies during heart development primarily caused by genetic mutations. While there isn’t just one driver of CHDs, transcription factors such as Nkx2.5, play a pivotal role in guiding cardiac morphogenesis. NKX2-5-associated CHDs often involve outflow tract (OFT) malformations. The development of the heart involves two progenitor cell populations, the first heart field (FHF) and second heart field (SHF), contributing to the linear heart tube and subsequent growth. Despite understanding the role of Nkx2.5, the spatiotemporal mechanisms directed by Nkx factors in SHF progenitor specification, proliferation, and identity maintenance remain elusive. This study aims to uncover novel effectors of Nkx transcriptional regulation, using RNA sequencing on dissected wild-type and nkx2.5-/- zebrafish hearts at 26 hours post fertilization (hpf). This work focuses on a LIM domain protein, cysteine rich intestinal protein 2 (crip2), identified as a mis-regulated gene in nkx2.5-deficient embryos, and we explore its role downstream of nkx genes in SHF-derived arterial pole formation. While crip2 is abundantly expressed in the developing heart, the family member crip3 also shows a mild expression pattern. Loss-of-function mutations in crip2 and crip3 (referred to as cripDM) reveal normal cardiac chamber specification. Atrioventricular canal morphology remains unaffected in cripDM embryos. The OFT in cripDM embryos displays a significant dilation, accompanied by increased ltbp3 expression. Surprisingly, the smooth muscle cell population of the OFT does not explain the size increase. This research expands our understanding of OFT development, highlighting the multi-layered contributions of various cell types and factors. In Chapter 3, we further examine the role of crip2 in the development of hematopoietic stem cells given its endothelial expression pattern. Hematopoietic stem and progenitor cells (HSPCs) have multilineage potential and can sustain long-term self-renewal. The ability to derive patient-specific HSCs in culture has immense therapeutic potential to overcome the shortage of compatible donors for HSC transplantations. However, differentiation protocols largely fail to produce long-lived HSCs from human pluripotent stem cells. Understanding the complex genetic networks and signaling pathways required to generate HSCs will facilitate clinical applications in patients. The hemogenic endothelium (HE) is a specialized niche of endothelial cells within the ventral portion of the dorsal aorta that gives rise to HSPCs during the definitive wave of hematopoiesis in the zebrafish embryo. Our data reveal that crip2 has a previously unrecognized function in establishing the proper endothelial cell environment for HSPC specification. CripDM embryos exhibit decreased emergence of HSCs by 26 hpf. Loss of HSPCs in the cripDM results in decreased erythroid, myeloid, and lymphoid lineage production between 30 -72 hpf; these perturbations in the hematopoietic lineages recover by 96 hpf. To decipher the spatiotemporal mechanisms underlying the cripDM phenotype, we performed single cell RNA (scRNA) sequencing of sorted, Kdrl:mCherry+ cells at 30 hpf. Our analysis reveals upregulation of genes essential for vascular development and mis-regulation of Notch signaling pathways in the cripDM embryos. Building on these data, our ongoing studies aim to investigate how crip2 regulates the endothelial niche of the ventral aorta to produce HSCs early in definitive hematopoiesis. We anticipate that our insights will inform potential therapeutic interventions for improvements of human HSC production in vitro.

Alterations of immune parameters were investigated in fish exposed to non-overtly toxic levels of three different environmentally relevant chemicals, 7,12-dimethylbenzanthracene (DMBA), hexachlorocyclohexane (lindane), and 2,3,7,8- tetrachlorodibenzo-p -dioxin (TCDD). Each chemical agent was administered to tilapia in separate experiments by intraperitoneal injection for five consecutive days. Following the final dose, total cellularity and histology of the spleen and pronephros were assessed, as were activity of phagocytic celis contained in these hematopoietic organs. <p>Using chemical doses which produced no clinical toxicity, tilapia exposed to each chemical agent displayed a significant reduction in total cell number of both spleen and pronephros, in most cases in a dose-related manner. Consistent with this observation, splenic and pronephric hypocellularity was confirmed upon histological examination of chemical-treated fish. However, neither superoxide radical production or phagocytosis of splenic or pronephric macrophages was inhibited in either DMBA, lindane, or TCDD exposed fish. Results of this study indicate that depressed total cell number in fish hematopoietic organs may be a more sensitive indicator of exposure to these environmental contaminants than is the activity of macrophages contained within these organs. / Master of Science

O diabetes mellitus do tipo 1 (T1D) é uma doença autoimune mediada por células T e caracterizada pela destruição seletiva das células ? pancreáticas produtoras de insulina. Células estromais mesenquimais (MSCs) e células tronco hematopoéticas (HSCs) são os principais componentes do nicho hematopoético na medula óssea. Estas células vêm sendo utilizadas nos últimos anos em transplantes autólogos para tratamento do T1D. O objetivo geral do presente trabalho foi avaliar o perfil de expressão gênica global de MSCs e HSCs de pacientes com T1D e compará-lo com células isoladas de indivíduos saudáveis através da técnica de microarray e programas específicos de bioinformática. As MSCs e HSCs foram isoladas da medula óssea de pacientes com T1D antes e após o tratamento com imunossupressão em altas doses seguida pelo transplante autólogo de células tronco hematopoéticas (AHSCT). As MSCs apresentaram valor elevado de expressão absoluta de diversas moléculas potencialmente relacionadas com suas funções de suporte à hematopoese. MSCs de pacientes diabéticos apresentaram perfil de expressão gênica global distinto das isoladas de indivíduos saudáveis, com hiper-regulação da sinalização via proteína G e hiporregulação da atividade transcricional. O receptor ?3 adrenérgico, assim como a sinalização simpática, foram hiper-expressos nas células dos pacientes. Genes que codificam moléculas que suportam a hematopoese e regulados pelo sistema nervoso simpático, VCAM1 e CXCL12, foram hiporregulados em nossa análise. Após o AHSCT, houve atenuação do perfil de expressão diferencial das MSCs dos pacientes, entretanto elas permaneceram com hiperatividade da sinalização via proteína G e déficit da atividade transcricional. As HSCs apresentaram altos níveis de expressão absoluta de diversas integrinas e receptores de citocinas e fatores de crescimento, potencialmente relacionados com funções na hematopoese. HSCs de pacientes com T1D apresentaram perfil de expressão gênica global distinto das de indivíduos saudáveis, com hiper-regulação de genes associados com a atividade transcricional. Os fatores de transcrição TCFL2 e p53, que têm papel fundamental na regulação do ciclo celular das HSCs, foram diferencialmente expressos entre as HSCs de pacientes diabéticos e controles. Assim, nossos resultados de expressão gênica global apontaram alterações intrínsecas nas HSCs e MSCs de pacientes diabéticos que podem estar relacionadas com a falha terapêutica dos transplantes autólogos. A implicação dessas alterações no desenvolvimento e patogênese do T1D permanece desconhecida e a realização de ensaios funcionais poderá esclarecer o significado biológico das mesmas. / Type 1 diabetes mellitus (T1D) is a T cell-mediated autoimmune disease, characterized by selective destruction of insulin-producing pancreatic ? cells. Mesenchymal stromal cells (MSCs) and hematopoietic stem cells (HSCs) are the main components of hematopoietic niches. In the last years, these cells are being used in autologous transplantation settings for T1D treatment. The main goal of this study was to evaluate the global gene expression profile of MSCs and HSCs from T1D patients, by using microarrays and bioinformatics specific programs. MSCs and HSCs were isolated from bone marrow of T1D patients before and after treatment with high dose immunossupression followed by hematopoietic stem cell transplantation. MSCs showed high absolute expression values of several molecules potentially related to their function of hematopoiesis support. MSCs from T1D patients exhibited distinct gene expression profile from control MSCs and presented up-regulation of the G protein-coupled receptor signaling pathway and down-regulation of transcriptional activity. The ?3 adrenergic receptor, as well the sympathetic nervous system signaling were up-regulated on patient´s cells. Genes that codify molecules which support hematopoeisis and are regulated by the symphatic nervous system, VCAM1 and CXCL12, were downregulated on our analysis. After AHSCT, there was an attenuation of the differential expression profile of MSCs from T1D patients, however they remained with G proteincoupled receptor signaling pathway hyperactivity and transcriptional activity deficit. HSCs exhibited high absolute expression values of integrins, cytokine receptors and growth factors, molecules potencially related to hematopoietic functions. HSCs from T1D patients showed distinct expression profile from control HSCs and demonstrated up-regulation of genes related to transcriptional activity. The transcription factors TCFL2 and p53, which have important role in regulating HSC cycle, were differentially expressed between HSCs from T1D patients and controls. Thus, our global gene expression analysis has revealed intrinsic alterations on MSCs and HSCs from T1D patients that could be related to the autologous transplant therapeutic failures. The implications of these alterations on the development and pathogenesis of T1D remain unknown and functional assays could unravel their biological meaning.

Objetivos: Avaliar os resultados das coletas de células hematopoéticas CD34+, por aférese, em crianças portadoras de neuroblastoma tratadas no Serviço de Oncologia e Hematologia do Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; estudar os fatores (idade, peso, estimulação com quimioterapia, dose do G-CSF, uso terapêutico de 131I-MIBG e tempo entre exposição à quimioterapia prévia) que influenciaram na mobilização e no rendimento da coleta de células CD34+ no sangue periférico e associar a quantidade de células CD34+ obtidas com a evolução clínica do paciente. Métodos: Trata-se de um estudo retrospectivo de pacientes com neuroblastoma submetidos à coleta de células-tronco hematopoéticas entre janeiro de1989 e junho 2012. Resultados: Avaliados 45 prontuários de crianças com idade mediana de 3,1 anos (0-12 anos), 26 (57%) apresentavam metástase em medula óssea ao diagnóstico. O tempo entre diagnóstico e o início da mobilização foi em média 19,7 ± 12 meses (mediana de 15,8 meses). Dos pacientes estudados, 11/45 (24,4%) receberam 131I-MIBG terapêutico antes da mobilização. Somente cinco pacientes (11,1%) receberam quimioterapia associada ao G-CSF para mobilização; as demais 40 crianças (88,9%) receberam exclusivamente G-CSF na dose média 26,5 ± 5,3 ug/kg/dia (mediana 28 ug/kg/dia). Não houve correlação entre o número máximo de células CD34+ no sangue periférico com a idade (p=0,9), com o peso (p=0,63), com a dose do G-CSF (p=0,46) ou com o intervalo entre o diagnóstico e o início da mobilização (p=0,09). A mediana da quantificação de células CD34+/uL no sangue periférico foi de 36,6 células, média de 45,2 ± 42,6 (mínimo 1,7 e máximo 236,3). Pacientes que haviam recebido 131I-MIBG previamente à mobilização apresentaram menor número de células CD34+/uL no sangue periférico (p=0,04). Em 26 pacientes (57,8%) foi possível coletar mais de 2,0x106 células CD34+/Kg na primeira coleta e em 19 pacientes (42,2%) foram necessárias mais de uma coleta, sendo que, oito pacientes (17,8%) apresentaram falha de mobilização. Os pacientes que apresentaram menor quantidade de células CD34+/uL no sangue periférico (<= 12) não conseguiram número maior ou igual a 2,0x106 células CD34+/Kg em 81,8% das coletas. O número mediano de células infundidas foi de 2,66 x106 células CD34+/Kg (média 3,38 ±1,6; mínimo 1,8; máximo 8,74 x106 CD34+/Kg). Os pacientes apresentaram contagem de leucócitos maior que 1000/mm3 e de plaquetas maior 50000/mm3 por dois dias consecutivos em média, no dia 13 ± 10 e no dia 46 ± 33, respectivamente, após infusão. Conclusões: A coleta de células-tronco hematopoéticas por aférese foi factível em todos os pacientes do estudo. Não houve influência significativa da idade, do peso, da dose do G-CSF e do tempo entre diagnóstico e inicio da mobilização, no número máximo de células. O uso prévio à coleta de 131I-MIBG terapêutico parece influenciar negativamente no pico de células CD34+ no sangue periférico (p=0,04). A contagem de células CD34+ no sangue periférico é importante fator preditivo do resultado das coletas de células progenitoras hematopoéticas CD34+ por aférese / Objectives: To evaluate the results of peripheral hematopoietic CD34+ stem cells harvesting in children with neuroblastoma treated at Serviço de Oncologia e Hematologia do Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; regarding age, weight, stimulation with chemotherapy, G-CSF dose, time between diagnosis and the mobilization beginning and therapeutic 131I-MIBG use and the influence in mobilization and peripheral harvesting of autologous hematopoietic stem cells and to associate the amount of CD34+ cells obtained with the patient\'s clinical evolution. Methods: Between January 1989 and June 2012, children with neuroblastoma underwent to mobilization and peripheral hematopoietic stem cell harvesting and were retrospectively analyzed. Results: The charts of 45 children were reviewed. Median age was 3.1 years (0-12years), and 26 (57%) had metastases in bone marrow at diagnosis. Average time between diagnosis and mobilization was 19.7 ± 12 months (median, 15.8 months). 11/45 (24.4%) received therapeutic 131I-MIBG prior to mobilization. The average G-CSF dose was 26.5 ± 5.3mg/kg/day (mean 28mg/kg/day). There was no correlation between the absolute number of peripheral CD34+ cells and age (p=0.9), weight (p=0.63), G-CSF dose (p=0.46) or the range between diagnosis and early mobilization (p=0.09). The median quantification of CD34+ cells/uL in peripheral blood was 36.6, average 45.2 ±42.6 (minimum 1.7 and maximum 236.3 CD34+ cells/uL). Patients who had received therapeutic 131I-MIBG prior to mobilization, showed fewer absolute amount of CD34+/uL cells in peripheral blood (p=0.04). In 26 patients (57.8%) it was possible to harvest more than 2.0 x106 CD34+ cells/kg at first apheresis and in 19 patients (42.2%) more than one collection were necessary, and eight patients (17.8 %) failure to mobilize. Patients presenting less than 12 CD34+ cells/uL in peripheral blood on the harvesting day failed to reach more then 2.0x106 cells CD34+/kg in 81.8% of the apheresis procedures. It was infused a median number of 2.66 x106 CD34+ cells/kg (mean 1.6 ± 3.38; min 1.8; max 8.74 x106 CD34+ cells/kg). After the stem cells infusion, patients had white blood cells count greater than 1000/mm3 and platelet greater than 50,000/mm3 for two consecutive days on average after 13 ±10 and 46 ± 33 days, respectively. Conclusions: The hematopoietic stem cells harvesting was feasible in all patients included in this report. The G-CSF dose, age, weight and the period between harvesting and diagnosis showed no influence in mobilization and harvesting of autologous hematopoietic stem cells, however the absolute number of peripheral blood CD34+ cells/uL is an important predictive factor for the harvesting outcome. Additionally our findings support for the first time the notion that the use of therapeutic 131I-MIBG could have a negative impact in mobilization of peripheral blood stem cells in children with neuroblastoma

L’hématopoïèse est un processus finement régulé pour permettre sa pérennité et son adaptation aux contraintes physiologiques et pathologiques. Ce potentiel repose en grande partie sur les capacités de quiescence, auto-renouvellement, division asymétrique et multipotence des cellules souches hématopoïétiques (CSH). Les CSH et progéniteurs hématopoïétiques (CSPH) sont principalement régulés de façon extrinsèque au sein des niches hématopoïétiques médullaires et cette régulation fait intervenir, des contacts intercellulaires et des facteurs diffusibles. Le phénotype « side-population » (SP), secondaire à l’efflux actif d’un colorant fluorescent (Hoechst 33342) par des pompes de type multidrugresistance, est une caractéristique des cellules souches de la plupart des tissus. Au sein de l’hématopoïèse, le phénotype SP est un excellent moyen pour identifier les CSH murines et est associé à leur quiescence et à leur adhésion à la niche endostéale, mais sa valeur comme marqueur des CSH est plus discutée chez l’homme. Les cellules SP, de par leur nature, sont également étudiées en oncologie, et sont associées aux cellules tumorales les plus résistantes et les plus tumorogènes. La compréhension des mécanismes régulant la fonctionnalité SP devrait permettre d’ouvrir des pistes en physiologie quand à la compréhension de la régulation des CSPH par les niches mésenchymateuses et en pathologie pour cibler les mécanismes de chimiorésistance.Dans ce travail nous montrons pour la première fois chez l’homme que l’acquisition du phénotype SP est un phénomène dynamique et versatile sous le contrôle du stroma médullaire. Le stroma médullaire est en effet capable de maintenir le phénotype SP de CSPH médullaires et d’induire le phénotype SP de CSPH circulants. L’acquisition du phénotype SP par les cellules circulantes nécessite à la fois un « nichage » au sein du stroma et des facteurs diffusibles. Les cellules circulantes capables d’acquérir le phénotype SP contiennent des CSPH au regard de (i) leur expression du CD34, (ii) leur richesse en cellules quiescentes, (iii) leur capacité clonogénique et proliférative en cultures secondaires, (iv) leur expression des gènes de « nichage » et de « souchitude », (v) leur capacité de migration en réponse à un gradient de CXCL12, (vi) leur activité LT-SRC in vivo. De plus nous avons mis en évidence, au sein de ces CSPH SP+CD34+ révélés par le stroma médullaire, une sous-population CD44-/faible qui pourrait contenir les cellules plus immatures en raison de sa quiescence et de l’intensité de son efflux du Hoechst 33342. Les études mécanistiques montrent que l’acquisition du phénotype SP par les cellules circulantes est sous la dépendance de l’intégrine VLA-4 et du CD44. La transduction du signal implique des protéines G et la famille des Src-kinases. Nous montrons également que le stroma médullaire peut induire/maintenir/amplifier la fonctionnalité SP de blastes circulants de leucémie aigüe myéloblastique de façon ß1-intégrine dépendante et que cette fonctionnalité est associée à une capacité d’efflux de Mitoxantrone. Ce mécanisme de modulation de l’activité d’ABC-transporteurs par l’adhésion au stroma correspond à un mécanisme encore jamais décrit de CAM-DR. / Hematopoiesis is a finely tuned process to allow its long-term efficiency and its adaptation to various physiological and pathological stresses. Hematopoietic stem cell (HSC) is the keystone of hematopoiesis through its multipotency, quiescence, asymmetrical division and self-renewing properties. HSC bone marrow (BM) niches mainly regulate hematopoietic stem and progenitor cells (HSPC) through intercellular contacts and diffusible factors. Side-population (SP) cells are characterized by their capability to actively efflux Hoechst 33342 dye through multidrug resistance-like pumps. SP phenotype is a characteristic of stem cells in many tissues and especially, it is a stringent criterion to purify murine HSCs. In mice, this phenotype has been demonstrated to be related to quiescence and resistance to drugs/environmental stresses and to be controlled by endosteal niche adhesion. SP cells are also studied in oncology and are associated to chemo-resistance and tumor initiating capacity. At steady state, SP cells are mainly present in the BM and are mostly absent from the circulation except in stress conditions, raising the hypothesis of the versatility of the SP functionality. Therefore, studying SP phenotype regulation is of importance to understand how BM niches regulate HSPC and how to interfere with cancer cells chemo-resistance.In this work, we demonstrate for the first time and in human that SP phenotype acquisition is a dynamic phenomenon under control of stromal BM cells. Stromal cells from healthy donors maintain SP phenotype of BM HSPC and promote SP phenotype acquisition in circulating ones. SP phenotype promotion depends of stroma nesting and of diffusible factors secretion. This stroma-induced circulating SP cell fraction contains HSPC, as ascertained by (i) CD34 expression, (ii) proportion of cells in G0, (iii) clonogenic and proliferative potential, (iv) nesting and “stemness” gene expression, (v) CXCL12-related migration capability and (vi) LT-SRC activity. Moreover, we describe an SP+CD34+CD44-/low sub-population that could contain most immature HSPCs with regards to their quiescence and Hoechst efflux intensity. Mechanistic studies show that the stoma-mediated SP promoting effect is VLA-4/4ß1-integrin and CD44 dependent, and implicate G-protein and Src-kinase pathways. We also demonstrate that BM stroma from healthy donors can induce/maintain/amplify in a ß1-integrin dependent manner an SP sub-population with mitoxantrone efflux capability in blast cells from acute myeloid leukemia. The existence of a similar mechanism in circulating leukemic blasts suggests the possibility to interfere with the chemo-resistant phenotype of blast cells through integrin/CD44 axis blockade.

Objetivos: Avaliar os resultados das coletas de células hematopoéticas CD34+, por aférese, em crianças portadoras de neuroblastoma tratadas no Serviço de Oncologia e Hematologia do Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; estudar os fatores (idade, peso, estimulação com quimioterapia, dose do G-CSF, uso terapêutico de 131I-MIBG e tempo entre exposição à quimioterapia prévia) que influenciaram na mobilização e no rendimento da coleta de células CD34+ no sangue periférico e associar a quantidade de células CD34+ obtidas com a evolução clínica do paciente. Métodos: Trata-se de um estudo retrospectivo de pacientes com neuroblastoma submetidos à coleta de células-tronco hematopoéticas entre janeiro de1989 e junho 2012. Resultados: Avaliados 45 prontuários de crianças com idade mediana de 3,1 anos (0-12 anos), 26 (57%) apresentavam metástase em medula óssea ao diagnóstico. O tempo entre diagnóstico e o início da mobilização foi em média 19,7 ± 12 meses (mediana de 15,8 meses). Dos pacientes estudados, 11/45 (24,4%) receberam 131I-MIBG terapêutico antes da mobilização. Somente cinco pacientes (11,1%) receberam quimioterapia associada ao G-CSF para mobilização; as demais 40 crianças (88,9%) receberam exclusivamente G-CSF na dose média 26,5 ± 5,3 ug/kg/dia (mediana 28 ug/kg/dia). Não houve correlação entre o número máximo de células CD34+ no sangue periférico com a idade (p=0,9), com o peso (p=0,63), com a dose do G-CSF (p=0,46) ou com o intervalo entre o diagnóstico e o início da mobilização (p=0,09). A mediana da quantificação de células CD34+/uL no sangue periférico foi de 36,6 células, média de 45,2 ± 42,6 (mínimo 1,7 e máximo 236,3). Pacientes que haviam recebido 131I-MIBG previamente à mobilização apresentaram menor número de células CD34+/uL no sangue periférico (p=0,04). Em 26 pacientes (57,8%) foi possível coletar mais de 2,0x106 células CD34+/Kg na primeira coleta e em 19 pacientes (42,2%) foram necessárias mais de uma coleta, sendo que, oito pacientes (17,8%) apresentaram falha de mobilização. Os pacientes que apresentaram menor quantidade de células CD34+/uL no sangue periférico (<= 12) não conseguiram número maior ou igual a 2,0x106 células CD34+/Kg em 81,8% das coletas. O número mediano de células infundidas foi de 2,66 x106 células CD34+/Kg (média 3,38 ±1,6; mínimo 1,8; máximo 8,74 x106 CD34+/Kg). Os pacientes apresentaram contagem de leucócitos maior que 1000/mm3 e de plaquetas maior 50000/mm3 por dois dias consecutivos em média, no dia 13 ± 10 e no dia 46 ± 33, respectivamente, após infusão. Conclusões: A coleta de células-tronco hematopoéticas por aférese foi factível em todos os pacientes do estudo. Não houve influência significativa da idade, do peso, da dose do G-CSF e do tempo entre diagnóstico e inicio da mobilização, no número máximo de células. O uso prévio à coleta de 131I-MIBG terapêutico parece influenciar negativamente no pico de células CD34+ no sangue periférico (p=0,04). A contagem de células CD34+ no sangue periférico é importante fator preditivo do resultado das coletas de células progenitoras hematopoéticas CD34+ por aférese / Objectives: To evaluate the results of peripheral hematopoietic CD34+ stem cells harvesting in children with neuroblastoma treated at Serviço de Oncologia e Hematologia do Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo; regarding age, weight, stimulation with chemotherapy, G-CSF dose, time between diagnosis and the mobilization beginning and therapeutic 131I-MIBG use and the influence in mobilization and peripheral harvesting of autologous hematopoietic stem cells and to associate the amount of CD34+ cells obtained with the patient\'s clinical evolution. Methods: Between January 1989 and June 2012, children with neuroblastoma underwent to mobilization and peripheral hematopoietic stem cell harvesting and were retrospectively analyzed. Results: The charts of 45 children were reviewed. Median age was 3.1 years (0-12years), and 26 (57%) had metastases in bone marrow at diagnosis. Average time between diagnosis and mobilization was 19.7 ± 12 months (median, 15.8 months). 11/45 (24.4%) received therapeutic 131I-MIBG prior to mobilization. The average G-CSF dose was 26.5 ± 5.3mg/kg/day (mean 28mg/kg/day). There was no correlation between the absolute number of peripheral CD34+ cells and age (p=0.9), weight (p=0.63), G-CSF dose (p=0.46) or the range between diagnosis and early mobilization (p=0.09). The median quantification of CD34+ cells/uL in peripheral blood was 36.6, average 45.2 ±42.6 (minimum 1.7 and maximum 236.3 CD34+ cells/uL). Patients who had received therapeutic 131I-MIBG prior to mobilization, showed fewer absolute amount of CD34+/uL cells in peripheral blood (p=0.04). In 26 patients (57.8%) it was possible to harvest more than 2.0 x106 CD34+ cells/kg at first apheresis and in 19 patients (42.2%) more than one collection were necessary, and eight patients (17.8 %) failure to mobilize. Patients presenting less than 12 CD34+ cells/uL in peripheral blood on the harvesting day failed to reach more then 2.0x106 cells CD34+/kg in 81.8% of the apheresis procedures. It was infused a median number of 2.66 x106 CD34+ cells/kg (mean 1.6 ± 3.38; min 1.8; max 8.74 x106 CD34+ cells/kg). After the stem cells infusion, patients had white blood cells count greater than 1000/mm3 and platelet greater than 50,000/mm3 for two consecutive days on average after 13 ±10 and 46 ± 33 days, respectively. Conclusions: The hematopoietic stem cells harvesting was feasible in all patients included in this report. The G-CSF dose, age, weight and the period between harvesting and diagnosis showed no influence in mobilization and harvesting of autologous hematopoietic stem cells, however the absolute number of peripheral blood CD34+ cells/uL is an important predictive factor for the harvesting outcome. Additionally our findings support for the first time the notion that the use of therapeutic 131I-MIBG could have a negative impact in mobilization of peripheral blood stem cells in children with neuroblastoma