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Background: The purpose of this study was to examine the impact of a culturally sensitive, cognitive-behavioral family treatment (CBFT) for pediatric patients with Sickle Cell Disease (SCD) to improve pain symptoms, health-related quality of life, functionality, depression, and coping strategies. Individual cognitive-behavioral treatment has been shown previously to be effective at improving pain symptoms, functionality, adaptive coping, and health care utilization, but such benefits have not yet been shown for SCD patients. The present study aimed to address this limitation by modifying the intervention to both include the family and to utilize culturally sensitive practices, which may be particularly relevant for this population. Methods: A non-concurrent multiple baseline design was used to assess the effectiveness of the intervention. A sample of 4 children (ages 8 to 12) and 4 adolescents (ages 13 to 15) participated in the intervention. Manualized treatment consisted of five sessions (including child and parent) that targeted problem-solving skills, cognitive processes, coping strategies, goal setting, and family processes. Outcomes of interest including health-related quality of life, functionality, psychological adjustment, and coping strategies, were assessed by child and parent report at pre-treatment (baseline), post-treatment, and 2-, 4-, and 6-month follow-up. Participants completed daily diaries to quantify pain, anxiety, and functionality. Results: Repeated-measures general linear model analyses were run separately for all outcome variables. A significant main effect of time was found for youth-reported HRQoL, F(4, 20) = 4.6, p=.01, depressive symptomatology, F(4, 20) = 4.5, p=.01, and parent-reported Internalizing, F(4, 16) = 3.4, p=.03, Externalizing, F(4, 16) = 7.2, p=.00, and Total Behavior Problems, F(4, 16) = 7.7, p=.00 from baseline to 6-month post-treatment. The mean frequency of pain symptoms also decreased for five of the eight participants (i.e., visual inspection of the daily diaries from baseline to treatment). Conclusions: These results suggest the potential for clinical gains through the incorporation of culturally sensitive and family-based practices into existing cognitive-behavioral interventions for SCD. The symptomatic improvements observed in the present study indicate gains in both specific domains (i.e., pain), as well as general psychological outcomes (i.e., improvements in depression, health-related quality of life, internalizing and externalizing behaviors). / Ph. D.

Multiple contributors to neurocognitive impairment in individuals with sickle cell disease have been identified. Research indicates that a history of cerebrovascular accidents, such as silent infarcts and strokes are associated with greater cognitive decline among children with sickle cell disease. Additionally, disease effects such as hemoglobin and hematocrit levels significantly effect cognitive performance among this population and should be taken into consideration when examining neurocognitive impairment. Further, previous studies show a significant relationship between child behavior problems, family functioning, and cognitive performance in children with sickle cell, marking those as important targets for intervention among this population. While cognitive decline with increased age is not typically examined in healthy child populations, some research indicates the presence of age effects in those with SCD. A majority of the literature addresses cognitive impairment from a broad perspective, while a limited number of studies have begun to address effects among specific cognitive domains. Using archival data from the National Institutes of Health's Cooperative Study of Sickle Cell Disease, results revealed that disease severity was negatively correlated with some aspects of cognitive functioning, including visual-spatial domains. Additionally, some measures of cognitive performance were inversely correlated with age. Consistent with hypothesized outcomes, family functioning was strongly associated with measures of cognitive functioning. Implications are discussed.

INTRODUÇÃO: Pacientes com doenças falciformes (DF) e outras anemias hemolíticas têm prevalência aumentada de hipertensão pulmonar (HP), sendo este diagnóstico associado com maior mortalidade. O objetivo deste trabalho foi estimar a prevalência desta complicação, suas características clínicas e laboratoriais e determinar o padrão hemodinâmico ao cateterismo de artéria pulmonar. MÉTODOS: Neste estudo transversal 80 pacientes consecutivos com anemia falciforme e Sb0 talassemia foram submetidos à ecocardiografia por um único observador. Os pacientes foram avaliados clinicamente, para verificar a presença de complicações associadas à DF, realizaram um teste de caminhada e realizaram exames hematológicos e bioquímicos referentes a parâmetros de hemólise, inflamação, função hepática e renal. Foi indicada avaliação hemodinâmica, com cateterismo de artéria pulmonar (Swan-Ganz), para os pacientes com velocidade de fluxo retrógrado pela tricúspide (VRT) ³2,5m/s, detectada ao ecocardiograma. A HP foi caracterizada por pressão média da artéria pulmonar ³ 25 mmHg. Os pacientes com HP foram comparados, com relação aos mesmos parâmetros prévios, ao restante da população estudada. RESULTADOS: 40% dos pacientes (32/80) apresentaram VRT³2,5m/s, sendo indicado avaliação hemodinâmica. O grupo com VRT³2,5m/s apresentou maior média etária, maior prevalência de úlceras de perna, de proteinúria e de hepatite C, menores valores de hemoglobina e de albumina, maiores valores de uréia, de creatinina, de ácido úrico, de desidrogenase lática, de aspartato aminotransferase e de gglutamiltranspeptidase do que os do grupo VRT<2,5m/s. O grupo VRT³2,5m/s apresentou também menor distância percorrida no teste de caminhada e saturação de oxigênio mais baixa tanto em repouso quanto após a caminhada. Ao ecocardiograma, este grupo apresentou maior volume atrial direito e esquerdo. 78% dos pacientes (25/32) com indicação de cateterismo se submeteram ao procedimento e em 8 deles foi confirmada HP. Dos 8 pacientes com diagnóstico de HP, 3 apresentaram hipertensão pré-capilar e os demais apresentaram hipertensão capilar (pressão de oclusão da artéria pulmonar acima de 15 mmHg). A VRT medida pelo ecocardiograma apresentou boa correlação com a medida de pressão sistólica de artéria pulmonar aferida no cateterismo (r=0,77). Os pacientes com HP confirmada apresentaram média etária maior, menores concentrações de hemoglobina e de contagem plaquetária e maiores valores de desidrogenase lática, uréia, creatinina, ácido úrico, gglutamiltranspeptidase e ferro do que o grupo sem HP. Os indivíduos com HP tiveram pior desempenho no teste de caminhada do que o grupo sem HP. Pacientes com HP apresentaram dilatação de átrio direito e esquerdo e índice cardíaco mais elevado do que o grupo sem HP. CONCLUSÕES: Pacientes com DF têm prevalência aumentada de HP detectada pelo ecocardiograma e confirmada pelo cateterismo pulmonar. O ecocardiograma é um bom instrumento de triagem. As populações separadas de acordo com o nível de VRT ao ecocardiograma apresentam diferenças clínicas e laboratoriais, sugerindo maior taxa de hemólise nas com VRT³2,5m/s. Estas diferenças se mantêm, na maior parte das situações, quando o diagnóstico de HP é confirmado. Indivíduos com diagnóstico de HP podem ter padrões hemodinâmicos de hipertensão capilar ou pré-capilar, denotando diferentes etiologias que podem implicar em diferentes abordagens terapêuticas. / INTRODUCTION: Patients with sickle cell disease (SCD) and other haemolytic anaemia have increased prevalence of pulmonary hypertension (PH) that is related to higher mortality. The aim of this stdy was to determine the prevalence of PH and, its clinical, laboratorial and hemodynamic features. METHODS: In a crosssectional study, we evaluated 80 consecutive patients with sickle cell anemia and Sb0thalassemia who were submitted to a Doppler echocardioghraphy performed by a single observer. Clinical and laboratorial data were collected for all patients in order to verify the presence of SCD complications and to evaluate haemolysis rate, inflammation, liver and renal function. All patients performed a six-minute walk test. Patients who had peak velocity of regurgitant flow of tricuspid (Vrft) of at least 2.5 m/s were referred to pulmonary artery catheterization (Swan-Ganz). PH was defined as a mean pulmonary artery pressure ³ 25 mmHg. Clinical, laboratorial and hemodynamic data of patients with confirmed PH were compared to those data of patients without PH. RESULTS: Forty percent of patients (32/80) had Vrft ³ 2.5m/s and hemodynamic evaluation was recommended. The group of patients with Vrft³2.5 m/s had higher average age, higher prevalence of leg ulcers, proteinuria and hepatitis C, lower values of hemoglobin and albumin, higher values of urea, creatinine, uric acid, lactic dehydrogenase, aspartate aminotransferase and gglutamyltranspeptidase than the group with Vrft<2.5 m.s. The group with Vrft³2.5 m/s had poorer performance on the walk test and had lowest oxygen saturation at rest and post-exercise. On echocardiography, this group had greater right and left atrial volume. Only 78% of patients (25/32) underwent pulmonary artery catheterization and, in 8 patients PH was confirmed. Among the patients with PH, 3 had pre-capillary hypertension and 5 had post-capillary hypertension (pulmonary artery occlusion pressure above 15 mmHg). The Vrft measured by echocardiogram showed good correlation with the value of systolic pulmonary artery pressure, measured on Swan-Ganz(r=0,77). The patients with confirmed PH had higher mean age, lower levels of haemoglobin and platelet count and higher values of lactic dehydrogenase, urea, creatinine, uric acid, iron and gglutamyltranspeptidase than the group without PH. Individuals with PH had poorer performance on walk test than the group without PH. Patients with PH showed increased right and left atrium volume and higher cardiac index than the group without PH. CONCLUSIONS: Patients with SCD had increased prevalence of PH detected by Doppler echocardiography and confirmed by pulmonary catheterization. The echocardiogram was a good tool for screening. Patients who had Vrft ³ 2.5m/s exhibited clinical and laboratorial data consistent with a higher hemolysis rate than those with Vrft<2.5 m/s. Individuals diagnosed with PH may have post-capillary or pre-capillary hypertension, suggesting the existence of several etiologies and the need for different therapeutic approaches.

INTRODUÇÃO: Pacientes com doenças falciformes (DF) e outras anemias hemolíticas têm prevalência aumentada de hipertensão pulmonar (HP), sendo este diagnóstico associado com maior mortalidade. O objetivo deste trabalho foi estimar a prevalência desta complicação, suas características clínicas e laboratoriais e determinar o padrão hemodinâmico ao cateterismo de artéria pulmonar. MÉTODOS: Neste estudo transversal 80 pacientes consecutivos com anemia falciforme e Sb0 talassemia foram submetidos à ecocardiografia por um único observador. Os pacientes foram avaliados clinicamente, para verificar a presença de complicações associadas à DF, realizaram um teste de caminhada e realizaram exames hematológicos e bioquímicos referentes a parâmetros de hemólise, inflamação, função hepática e renal. Foi indicada avaliação hemodinâmica, com cateterismo de artéria pulmonar (Swan-Ganz), para os pacientes com velocidade de fluxo retrógrado pela tricúspide (VRT) ³2,5m/s, detectada ao ecocardiograma. A HP foi caracterizada por pressão média da artéria pulmonar ³ 25 mmHg. Os pacientes com HP foram comparados, com relação aos mesmos parâmetros prévios, ao restante da população estudada. RESULTADOS: 40% dos pacientes (32/80) apresentaram VRT³2,5m/s, sendo indicado avaliação hemodinâmica. O grupo com VRT³2,5m/s apresentou maior média etária, maior prevalência de úlceras de perna, de proteinúria e de hepatite C, menores valores de hemoglobina e de albumina, maiores valores de uréia, de creatinina, de ácido úrico, de desidrogenase lática, de aspartato aminotransferase e de gglutamiltranspeptidase do que os do grupo VRT<2,5m/s. O grupo VRT³2,5m/s apresentou também menor distância percorrida no teste de caminhada e saturação de oxigênio mais baixa tanto em repouso quanto após a caminhada. Ao ecocardiograma, este grupo apresentou maior volume atrial direito e esquerdo. 78% dos pacientes (25/32) com indicação de cateterismo se submeteram ao procedimento e em 8 deles foi confirmada HP. Dos 8 pacientes com diagnóstico de HP, 3 apresentaram hipertensão pré-capilar e os demais apresentaram hipertensão capilar (pressão de oclusão da artéria pulmonar acima de 15 mmHg). A VRT medida pelo ecocardiograma apresentou boa correlação com a medida de pressão sistólica de artéria pulmonar aferida no cateterismo (r=0,77). Os pacientes com HP confirmada apresentaram média etária maior, menores concentrações de hemoglobina e de contagem plaquetária e maiores valores de desidrogenase lática, uréia, creatinina, ácido úrico, gglutamiltranspeptidase e ferro do que o grupo sem HP. Os indivíduos com HP tiveram pior desempenho no teste de caminhada do que o grupo sem HP. Pacientes com HP apresentaram dilatação de átrio direito e esquerdo e índice cardíaco mais elevado do que o grupo sem HP. CONCLUSÕES: Pacientes com DF têm prevalência aumentada de HP detectada pelo ecocardiograma e confirmada pelo cateterismo pulmonar. O ecocardiograma é um bom instrumento de triagem. As populações separadas de acordo com o nível de VRT ao ecocardiograma apresentam diferenças clínicas e laboratoriais, sugerindo maior taxa de hemólise nas com VRT³2,5m/s. Estas diferenças se mantêm, na maior parte das situações, quando o diagnóstico de HP é confirmado. Indivíduos com diagnóstico de HP podem ter padrões hemodinâmicos de hipertensão capilar ou pré-capilar, denotando diferentes etiologias que podem implicar em diferentes abordagens terapêuticas. / INTRODUCTION: Patients with sickle cell disease (SCD) and other haemolytic anaemia have increased prevalence of pulmonary hypertension (PH) that is related to higher mortality. The aim of this stdy was to determine the prevalence of PH and, its clinical, laboratorial and hemodynamic features. METHODS: In a crosssectional study, we evaluated 80 consecutive patients with sickle cell anemia and Sb0thalassemia who were submitted to a Doppler echocardioghraphy performed by a single observer. Clinical and laboratorial data were collected for all patients in order to verify the presence of SCD complications and to evaluate haemolysis rate, inflammation, liver and renal function. All patients performed a six-minute walk test. Patients who had peak velocity of regurgitant flow of tricuspid (Vrft) of at least 2.5 m/s were referred to pulmonary artery catheterization (Swan-Ganz). PH was defined as a mean pulmonary artery pressure ³ 25 mmHg. Clinical, laboratorial and hemodynamic data of patients with confirmed PH were compared to those data of patients without PH. RESULTS: Forty percent of patients (32/80) had Vrft ³ 2.5m/s and hemodynamic evaluation was recommended. The group of patients with Vrft³2.5 m/s had higher average age, higher prevalence of leg ulcers, proteinuria and hepatitis C, lower values of hemoglobin and albumin, higher values of urea, creatinine, uric acid, lactic dehydrogenase, aspartate aminotransferase and gglutamyltranspeptidase than the group with Vrft<2.5 m.s. The group with Vrft³2.5 m/s had poorer performance on the walk test and had lowest oxygen saturation at rest and post-exercise. On echocardiography, this group had greater right and left atrial volume. Only 78% of patients (25/32) underwent pulmonary artery catheterization and, in 8 patients PH was confirmed. Among the patients with PH, 3 had pre-capillary hypertension and 5 had post-capillary hypertension (pulmonary artery occlusion pressure above 15 mmHg). The Vrft measured by echocardiogram showed good correlation with the value of systolic pulmonary artery pressure, measured on Swan-Ganz(r=0,77). The patients with confirmed PH had higher mean age, lower levels of haemoglobin and platelet count and higher values of lactic dehydrogenase, urea, creatinine, uric acid, iron and gglutamyltranspeptidase than the group without PH. Individuals with PH had poorer performance on walk test than the group without PH. Patients with PH showed increased right and left atrium volume and higher cardiac index than the group without PH. CONCLUSIONS: Patients with SCD had increased prevalence of PH detected by Doppler echocardiography and confirmed by pulmonary catheterization. The echocardiogram was a good tool for screening. Patients who had Vrft ³ 2.5m/s exhibited clinical and laboratorial data consistent with a higher hemolysis rate than those with Vrft<2.5 m/s. Individuals diagnosed with PH may have post-capillary or pre-capillary hypertension, suggesting the existence of several etiologies and the need for different therapeutic approaches.

La drépanocytose est la maladie moléculaire et héréditaire (transmission mendélienne récessive et autosomique) la plus répandue au monde. Elle est un problème de santé publique par sa gravité et ses implications socio-économiques dans de nombreux pays. Seuls les sujets homozygotes (SS) ou hétérozygotes composites (SC) sont malades, les hétérozygotes (AS) ne sont que des transmetteurs du gène S. Elle est la première cause d’OstéoNécrose de la Tête Fémorale (ONTF), douloureuse évoluant vers l’arthrose, en l’absence de traitement chez un patient jeune.<p>La Guadeloupe compte 450.000 habitants, dont 12% sont porteurs de l’hémoglobine S. Le nombre des drépanocytaires est estimé à 1.200 dont les 3/4 sont suivis au Centre Caribéen de la Drépanocytose (CCD), créé en 1990. Le centre assure la prise en charge médicale des enfants dès leur naissance et des adultes malades. Nos activités au CHU de Pointe-à-Pitre, au CCD et à l’Unité INSERM-UMR S458 depuis juillet 1992 nous ont permis d’étudier:<p>- le diagnostic de l’ONTF;<p>- l’évaluation de l’hyperpression osseuse dans l’ONTF et l’évaluation du traitement par forage simple;<p>- l’étude de l’impact de la prise en charge orthopédique précoce sur la survenue et l’évolution de l’ONTF.<p>Notre étude concerne les patients drépanocytaires adultes homozygotes (SS) et double hétérozygotes (SC):<p>- une série rétrospective de 1993-1994 [E-1994] portant sur 115 patients (58 SS, 57 SC) identifiés en 1984,<p>sans suivi médical ni orthopédique;<p>- une série prospective de 1995 à 2008 [E-2008] portant sur 215 patients (94 SS, 121 SC) avec prise en<p>charge médicale et orthopédique.<p>L’IRM est l’examen de référence pour le diagnostic de l’ONTF comme dans la nécrose idiopathique. En absence d’imagerie moderne, la radiographie traditionnelle réalisée de façon complète (profil et, surtout, faux profil), permet le diagnostic avant toute déformation. Seules les lésions cliniquement symptomatiques et évolutives (examen clinique itératif, contrôle radiologique, tomographie, TDM ou IRM) ont une indication opératoire.<p>L’hyperpression intra osseuse, dans l’ONTF drépanocytaire, est significativement liée à la douleur (que les patients soient homozygotes ou hétérozygotes). Sa diminution a un effet antalgique objectif, observée après forage. Elle permet de confirmer le diagnostic d’ostéonécrose au stade précoce, dans les régions où l’IRM est inexistante.<p>Un forage réalisé aux stades précoces de l’ONTF permet un arrêt rapide de l’évolution des lésions vers une arthrose, avec une efficacité certaine pour les stades I et II. Il garde une efficacité limitée pour le stade III. En plus de l’indolence apportée par la décompression, le bénéfice du forage se manifeste par l’allongement du délai avant arthroplastie (de 7,4 ± 2,7 ans). La technique est réalisable dans les régions sous équipées, où la drépanocytose est fréquente.<p>La description histologique aux différents stades radiologiques de l’ONTF montre toujours des lésions de nécrose médullaire et osseuse. A l’inverse des lésions idiopathiques, les lésions drépanocytaires sont caractérisées par la présence d’une inflammation, en dehors de tout processus infectieux.<p>Dans la littérature, la fréquente de l’ONTF drépanocytaire chez l’adulte est voisine de 40%, proche de celle observée dans [E-1994], notre population non suivie (36,5%). En comparant les études [E-1994] et [E-2008], la fréquence de l’ONTF passe de 36,5% à 14,4%. L’officialisation en 1992 d’une prise en charge médicale et d’un suivi orthopédique régulier au CCD et au CHU de Pointe-à-Pitre, a permis la réduction de la fréquence de l’ONTF et d’autres morbidités.<p>Le rappel sur la drépanocytose révèle la complexité de la maladie, la variabilité de son expression clinique et de ses complications. L’amélioration de vie des patients nécessite une prévention primaire, secondaire et tertiaire, en l’absence d’un traitement spécifique de la maladie.<p>La prise en charge médicale, complétée par une prévention et un traitement précoce (orthopédique ou chirurgical) telle que réalisés au CCD en Guadeloupe, a permis une réduction significative de la survenue de la nécrose de hanche et de ses complications. Pour une prévention tertiaire des complications ostéo-articulaires, nous suggérons:<p>- une prise en charge médicale régulière des enfants et des adultes afin de réduire les crises vaso-occlusives;<p>- une éducation des patients à la recherche de signes d’appel de l'ONTF et, aussi, d’autres articulations;<p>- un examen clinique ostéo-articulaire lors des bilans annuels et après toute crise vaso-occlusive;<p>- une attention particulière à l’adolescence (passage enfant-adulte), après une grossesse;<p>- une prise en charge précoce, orthopédique ou chirurgicale conservatrice (forage ou ostéotomie) face à une<p>nécrose, afin de réduire les complications invalidantes de l’ONTF.<p><p>Sickle-cell anemia is the most widespread hereditary (autosomal recessive Mendelian transmission) molecular pathology in the world. It is a public health issue in many countries, due to its severity and socio-economic impact. Only homozygous (SS) and double heterozygous (SC) subjects are affected, heterozygous (AS) subjects merely transmitting the gene S. Sickle-cell anemia is the most frequent cause of osteonecrosis of the femoral head (ONFH), a painful condition which evolves towards osteoarthritis if not treated at an early age.<p>Guadeloupe has a population of 450,000, 12% of whom are carriers of hemoglobin S. There are estimated to be 1,200 sickle-cell anemia sufferers, three-quarters of whom are followed in the Caribbean Sickle-Cell Center (Centre Caribéen de la Drépanocytose: CCD), which was set up in 1990. The Center provides medical care for adult patients and for children as of birth. Work has been ongoing since July 1992, in the Pointe-à-Pitre University Hospital, the CCD and the INSERM-UMR S458 research unit, focusing on:<p>- diagnosis of ONFH;<p>- bone hyperpressure measurement in ONFH and assessment of simple drilling treatment;<p>- the impact of early orthopedic treatment on the onset and evolution of ONFH.<p>The present study involved homozygous (SS) and double heterozygous (SC) adult sickle-cell anemia patients:<p>- a retrospective series, from 1993 to 1994 [S-1994], including 115 patients (58 SS, 57 SC) identified in 1984,<p>who had no medical or orthopedic care;<p>- a prospective series, from 1995 to 2008 [S-2008], including 215 patients (94 SS, 121 SC), with medical and orthopedic care.<p>MRI is the diagnostic gold-standard in ONFH, as in idiopathic necrosis. Where such modern imaging is not available, complete standard X-ray (lateral and especially false lateral) enables diagnosis to be made before deformity sets in. Surgery is indicated only for clinically symptomatic evolutive lesions on iterative clinical check-up, X-ray control, tomography, CT or MRI.<p>Intraosseous hyperpressure in sickle-cell ONFH shows a significant correlation with pain, in both homozygous and heterozygous patients. Pressure reduction is objectively pain-relieving, as seen after drilling, and can confirm diagnosis of ONFH at an early stage, in places where MRI is not available.<p>Drilling performed in the early stages of ONFH quickly arrests evolution towards osteoarthritis, with proven efficacy in grades I and II, and a certain degree of effectiveness in grade III. Over and above the pain-relief provided by decompression, drilling also enables hip replacement to be postponed, by 7.4±2.7 years. Moreover, the technique is feasible in those under-equipped regions in which sickle-cell disease is widespread.<p>Histologic description of radiologic ONFH stages consistently finds medullary and bone necrosis. In contrast to idiopathic lesions, sickle-cell related lesions show inflammation without any associated infection.<p>In the literature, the frequency of adult sickle-cell ONFH is reported to be nearly 40%, close to the 36.5% found in the S-1994 study of a non-treated population. In the S-2008 study of a population with medical and orthopedic care, ONFH frequency fell to 14.4%. The official provision of medical care and regular orthopedic follow-up in the CCD and Pointe-à-Pitre Hospital has reduced the frequency of ONFH and other morbidities.<p>A review of sickle-cell disease reveals its complexity: the variability of its clinical expression and associated complications. Improving patients’ quality of life requires primary, secondary and tertiary prevention, in the absence of specific treatment.<p>Medical care, supplemented by early prevention and treatment (orthopedic or surgical), as practiced in the Guadeloupe CCD, has significantly reduced the rates of ONFH and associated complications. We recommend the following CCD protocol for tertiary prevention of osteoarticular complications:<p>- regular medical care for children and adults, to reduce the incidence of vaso-occlusive crises;<p>- patient education in alarm signs of osteonecrosis of the femoral head and of other joints;<p>- systematic osteoarticular assessment at yearly check-up and after all vaso-occlusive crises;<p>- special focus on adolescence (child-to-adult transition) and following pregnancy;<p>- early care, both orthopedic and by conservative surgery (drilling or osteotomy), in case of necrosis, to reduce the rate of disabling complications of ONFH / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

An understanding of the human fetal to adult hemoglobin switch offers the potential to ameliorate β-type globin gene disorders such as sickle cell anemia and β-thalassemia through activation of the fetal γ-globin gene. Chromatin modifying complexes, including MBD2-NuRD and GATA-1/FOG-1/NuRD play a role in γ-globin gene silencing, and Mi2β (CHD4) is a critical component of NuRD complexes. In the studies presented in Chapter 2, we observed that the absence of MBD2 in a sickle cell mouse model leads to a decrease in the number of sickled cells observed in the peripheral blood, and significantly increases survival in these mice. Although further studies will be necessary to fully understand the effect of MBD2 knockout in sickle cell disease mice, absence of MBD2 appears to partially ameliorate the sickle cell anemia phenotype in vivo. In the studies presented in Chapter 3, we observed that knockdown of Mi2β relieves γ-globin gene silencing in β-YAC transgenic murine CID hematopoietic cells and in CD34+ progenitor derived human primary adult erythroid cells. We show that independent of MBD2-NuRD and GATA-1/FOG-1/NuRD, Mi2β binds directly to and positively regulates both the KLF1 and BCL11A genes, which encode transcription factors critical for γ-globin gene silencing during β-type globin gene switching. Remarkably, less than 50% knockdown of Mi2β is sufficient to significantly induce γ-globin gene expression without disrupting erythroid differentiation of primary human CD34+ progenitors. These results indicate that Mi2β is a potential target for therapeutic induction of fetal hemoglobin.