La malformation de Chiari type 1 (MCI) est une anomalie congénitale de la jonction cranio-cérébrale fréquente avec une incidence de 1:1280. MCI est caractérisée par la descente des amygdales cérébelleuses à travers le foramen magnum et est souvent associée à la syringomyélie. Les causes de cette maladie semblent être multifactorielles incluant des facteurs génétiques. La MCI est similaire à une malformation fréquente chez la race des Griffon Bruxellois (GB) connue sous le nom de Malformation Chiari-like (MCL). Le modèle canin offre l’avantage d’une forte homogénéité génétique réduisant ainsi la complexité de la maladie et facilitant l’identification d’un locus causatif. Une étude d’association du génome entier sur une cohorte de 56 GB suivie d’une cartographie fine sur une cohorte de 217 GB a identifié un locus fortement associé à la MCL sur le chromosome 2 (22 SNPs, valeur P= 7 x 10-8) avec un haplotype de 1.9 Mb plus fréquent chez les non affectés. Une seconde étude d’association du génome entier sur une cohorte de 113 GB a permis d’identifier un 2 ème locus fortement associé à la MCL sur le chromosome 13 (25 SNPs , valeur P= 3 x 10 -7) avec un haplotype de 4 Mb surreprésenté chez les non affectés. Ces régions candidates constituent la première étape vers l’identification de gènes causatifs pour la MCL. Notre étude offre un point d’entrée vers une meilleure compréhension des mécanismes moléculaires sous-tendant la pathogénèse de la MCI humaine. / Chiari I malformation (CMI) represents a common congenital abnormality of the craniocerebral junction with an estimated incidence of 1 in 1280. CMI is characterized by a descent of the cerebellar tonsils into the foramen magnum, often in association with syringomyelia. The developmental defect in CMI is thought to be the result of an underdeveloped occipital bone and small posterior fossa. The etiology of CMI is thought to be multifactorial involving genetic factors. CMI in humans is similar to a condition in the dog called Chiari-like malformation (CM) that is particularly common in the Griffon Bruxellois (GB) breeds. A genome wide association study on a 56 GB cohort followed by a fine mapping in a 217 GB cohort have identified a locus on chromosome 2 that was strongly associated with CM (22 SNPs, P value= 7 x 10-8). Haploview analysis of this locus identified a haplotype of 1.9 Mb that was more frequent in non-affected dogs. A second genome wide association study in a 113 GB cohort lead to the identification of another locus on chromosome 13 that was strongly associated with CM (25 SNPs , P value= 3 x 10-7). Analysis of this region identified a 4Mb haplotype that was more frequent in non-affected dogs. Our study constitutes the first essential step towards identification of the causative genes in CM. Our study provides an entry point for better understanding of the molecular genetic mechanisms underlying the pathogenesis of human CMI.

O transplante intrauterino de células-tronco (TIUCT) é um método de tratamento de doenças genéticas, congênitas, hematológicas e imunológicas em um feto durante a gestação. Em pesquisa básica este modelo permite o estudo da dinâmica de migração, enxertia e estado funcional de diferentes tipos de células-tronco (CT). Estas células podem ser transplantadas em diferentes momentos do período gestacional, que pode ser dividido em três momentos do desenvolvimento fetal, sendo estes, diferentes funcionalmente. A escolha deste momento para o transplante influenciará tanto no comportamento celular quanto no resultado. Para o TIUCT são utilizadas as CT mesenquimais derivadas da medula óssea ou fetais ou hematopoiéticas. Para esta pesquisa utilizamos células-tronco derivadas da polpa dentária imatura humana (CTIPDh) as quais apresentam potencial pluripotente e propriedades imunomodulatórias. Nosso principal objetivo foi avaliar a capacidade migratória, bem como de proliferação e endereçamento (homing) das CTIPDh durante o terceiro período gestacional do desenvolvimento fetal no modelo canino. Todos os procedimentos experimentais foram elaborados sob protocolo anestésico apropriado e aprovados pelo comitê de ética da FMVZ da USP. Foram transplantadas via intraperitoneal (IP) 1x106 CTIPDh GFP+ em cada feto, durante procedimento cirúrgico de laparotomia exploratória com ultrassonografia guiada intraoperatóriamente em quatro fetos com idade gestacional aproximada de 45 dias, e outros dois fetos os quais não receberam o transplante, utilizados como controle. Avaliamos os fetos pré e pós-transplante através do ultrasson. Após sete dias, realizamos a ovário-salpingo-histerectomia (OSH) para a colheita dos fetos. Em seguida coletamos seus órgãos e tecidos os quais foram fixados em paraformoldeído a 4% e criopreservados a temperatura de -80oC. Analisamos a biodistribuição das CTIPDh dentro dos órgãos e tecidos em criocortes de 5µm sob microscopia Confocal. Constatamos o homing das CTIPDh nos órgãos derivados das linhas germinativas endodermais, ectodermais e mesodermais. No estômago e intestinos as CTIPD/GFP+ foram identificadas tanto no espaço intraglandular, como na camada muscular da mucosa; no fígado no parenquima hepático; no coração especialmente no tecido muscular do miocárdio; no cérebro nos vasos da substância branca, e cerebelo entre células de Purkinje. Na placenta estas células foram encontradas especialmente junto aos vasos. Quantificamos as CTIPD GFP+ utilizando a citometria de fluxo. Comparativamente dentre os órgãos analisados, obtivemos resultados expressivos do homing celular no miocárdio (~50%), no baço e fígado. Nossos resultados foram confirmados através das análises de imunohistoquímica e imunofluorescência utilizando os anticorpos Anti-núcleo (HuNu), Anti-CTIPD e Anti-GFP humanos. Concluímos que as CTIPDh apresentam grande potencial migratório e proliferativo após o TIUCT em fetos caninos. Estas células indiferenciadas demonstraram homing, especialmente nos tecidos: hematopoiéticos fetais (placenta, fígado e baço), tecido epitelial e glandular de órgãos, bem como de nichos perivasculares de CT. Estes dados sugerem que as CTIPD através do TIU, é uma alternativa viável, segura e promissora para o tratamento de doenças genéticas, congênitas, hematológicas e imunológicas. / Intra-uterine stem cells transplantation (IUSCT) is a method for the treatment of genetic, congenital, hematological, and immunological diseases. In basic research it provides a model for studying the dynamics of migration, graft and functional status of different types of stem cells. The cells can be transplanted in different moments of gestational period, which can be divided into quarters that are not functionally equivalent. The choice of the cells and quarter where the stem cells will be applied can influence cells behavior and results of transplantation. Fetal and adult hematopoietic or bone marrow derived mesenchymal stem cells (MSCs) were mainly used for IUSCT. We previously obtained human immature dental pulp stem cell (IDPSCs), which showed pluripotent potential and immune-compatible properties. The goal of our study was to evaluate migration capacity, proliferation and homing of IDPSCs after IUSCT during the third fetal period in dogs. All experimental procedures were approved by the Ethical Committee of the School of Veterinary Medicine and Animal Science of São Paulo University and were performed under appropriate anesthesia. 1x106 of undifferentiated GFP-positive human IDPSCs were transplanted following laparotomy and intraperitoneal injection under intra-operative ultrasound control into 5 fetuses at the 45 days of gestation. Five fetuses, which did not receive IDPSCs, were used as a control. Ultrasound analyses were performed daily before collection of the fetuses. After 7 days ovarian hysterectomy was performed, fetuses were collected; organs and tissues were isolated and fixed in 4% paraformaldehyde or cryopreserved. Biodistribution of IDPSCs within the organs and tissues were analyzed on cryosections (5µm) under Confocal Microscopy. Homing of IDPSCs was observed in organs derived from three germ lines, endoderm, ectoderm and mesoderm. In stomach and in intestine GFP IDPSCs were found in intraglandular space as well as in muscularis mucosae. In liver they appeared in hepatic parenchyma; in heart in myocardium and in brain in bold vessels, in cerebellum within Purkinje cells. Using Flow cytometry assay GFP IDPSCs graft was quantified. Among the different organs an expressive homing was observed in myocardium of heart (~50%), in spleen and liver. The IDPSCs were also found in canine placenta, especially in blood vessels. These data were confirmed using anti-human nucleus (HuNu), anti-GFP and anti-IDPSCs anti-bodies. Human IDPSCs showed high migration and proliferation potential after IUSCT in dog fetuses. Undifferentiated IDPSCs demonstrated homing in fetal hematopoietic (placenta), epithelial (gastric glands) and perivascular stem cells niches. Our data suggest that IDPSCs is a new promising source for genetic, congenital, hematological, and immunological treatment for those diseases through IUSCT.