Los microRNAs (miRNAs) son unas pequeñas moléculas de RNA (20-25nt) que no codifican para proteína, sin embargo actúan inhibiendo la traducción a proteína de RNAs mensajeros mediante la unión a su región UTR 3'. Se ha visto que estos miRNAs juegan un papel esencial en la regulación de la diferenciación celular y en el mantenimiento del estado pluripotente en las células madre. De la misma manera se los ha visto desregulados en múltiples tumores, llegando a ser considerados en algunos casos oncogenes o genes supresores de tumores.En la presente tesis se realizado un análisis de la expresión de miRNAs maduros en dos modelos tumorales diferentes: por un lado se ha analizado el patrón de expresión de miRNAs en tejido tumoral y normal de pacientes afectos de cáncer colorectal y en muestras de colon embrionario humano de embriones de 7-12 semanas de desarrollo. Por otro lado se ha analizado el patrón de expresión de miRNAs en ganglios de pacientes afectos de linfoma de Hodgkin clásico y en ganglios normales. Para ello se han analizado un total de 156 miRNAs maduros mediante stem-loop RT-PCR y PCR a tiempo real(TaqMan). La validación de los resultados se ha realizado mediante el uso de líneas celulares (DLD1 de cáncer colorectal, y L-428, HD-MY-Z y L-1236 de linfoma de Hodgkin) y mediante hibridación in situ de miRNAs con sondas de tipo LNA(Exiqon) en la plataforma automática Bond Max (Vision Biosystems).En el análisis del cáncer colorectal y la embriogénesis del colon se ha detectado una expresión solapada de miRNAs entre la mucosa colónica embrionaria y el cáncer colorectal. Se ha determinado una firma de miRNAs que caracteriza al cáncer colorectal de estadio I y II. Se ha definido también el patrón de expresión de miRNAs durante la embriogénesis del colon. Además hemos demostrado que el cluster de miRNAs miR-17-92 y su proteína diana E2F1 comparten un patrón de expresión común entre la embriogénesis del colon humano y la carcinogénesis colorectal, actuando en la regulación del proceso de proliferación celular. En este sentido, la hibridación in situ confirmó la sobreexpresión de miR-17-5p en la base de las criptas colónicas, en el compartimiento proliferativo. Por otro lado, en el estudio del patrón de expresión de miRNAs en el linfoma de Hodgkin clásico (LHc), se ha encontrado una firma de 25 miRNAs que caracterizan a este LHc. Entre estos miR-21, miR-134 y miR-138 mediante hibridación in situ se los ha detectado en el citoplasma de las células de Hodgkin/Reed Sternberg (H/RS). La validación de los 25 miRNAs en las líneas celulares ha demostrado que 20 son expresados por las líneas celulares y únicamente 5 son de expresión exclusiva del microambiente reactivo. Por otro lado se han definido 32 miRNAs que permiten discriminar entre el subtipo histológico esclerosis nodular, del subtipo celularidad mixta, de los cuales 11 mostraban diferencias que caracterizaban a las células tumorales de un tipo u otro. Además se analizó si la presencia del virus de Epstein Barr (EBV) estaba alterando el patrón de miRNAs en los pacientes de LHc EBV+ respecto a los EBV-, y se encontraron un conjunto de 10 miRNAs diferencialmente expresados entre los dos grupos de pacientes. Finalmente se vio que miR-138 estaba sobreexpresado en estadios iniciales (I-II) y se infraexpresaba en estadios avanzados (III-IV).Los miRNAs se deben considerar como moléculas claves tanto en la embriogénesis del colon, como en la transformación neoplásica del epitelio colónico, así como en el LHc, pudiendo ser utilizadas en un futuro como herramienta terapéutica. / MicroRNAs (miRNAs) are negative regulators of gene expression that play an important role in hematopoiesis and tumorigenesis and have been shown to be essential to regulate cell differentiation and maintenance of the pluripotent cell state.To date, no evidence has linked miRNA expression in embryonic and tumor tissue. We assessed the expression of mature miRNAs in human embryonic colon tissue and in colorectal cancer and paired normal colon tissue. Overlapping miRNA expression was detected between embryonic colonic mucosa and colorectal cancer. We demonstrated that miR-17-92 cluster and expression of its target E2F1 share a common pattern between human colon embryogenesis and colonic carcinogenesis, regulating the proliferation process. In this sense, in situ hybridization assay confirmed the overexpression of miR-17-5p in the crypt progenitor compartment. miRNAs pathways must be considered to be included as major players contributing to both embryonic development and neoplastic transformation of colonic epithelium. In other hand, we analyzed miRNA expression in classic Hodgkin lymphoma (cHL) and the influence of Epstein-Barr virus (EBV) infection on the miRNA expression profiles. The expression of 157 miRNAs in lymph nodes from 49 cHL patients and 10 reactive lymph nodes (RLNs) was analyzed by real-time polymerase chain reaction (PCR). Hierarchic clustering revealed 3 well-defined groups: nodular sclerosis cHL, mixed cellularity cHL, and RLNs. A distinctive signature of 25 miRNAs differentiated cHL from RLNs, and 36 miRNAs were differentially expressed in the nodular sclerosis and mixed cellularity subtypes. These results were validated in a set of 30 cHLs and 5 RLNs, and in 3 cHL cell lines. miR-96, miR-128a, and miR-128b were selectively down-regulated in cHL with EBV. Our findings suggest that miRNAs play an important role in the biology of cHL and may be useful in developing therapies targeting miRNAs.

El objetivo de este trabajo ha sido el estudio de dos factores genéticos implicados en la diferenciación de las neuronas GABAérgicas de proyección estriatales: Nolz1 e Ikaros. Además se ha estudiado el potencial de estos factores de transcripción en la diferenciación de células madre neurales in vitro hacia un fenotipo estriatal para entender mejor los mecanismos que regulan la aparición de este tipo de neuronas.Hemos demostrado que Nolz1 es un gen que interviene en la especificación de los precursores neurales de la SVZ de la eminencia ganglionar lateral (LGE), los llamados progenitores basales. Las células Nolz1 positivas provienen de precursores positivos para Gsh2, y su expresión contribuye a la aparición de la señalización de ácido retinoico en el núcleo estriado durante el desarrollo. Nolz1, además, regula la vía de Notch en precursores neurales i promueve la aparición de precursores oligodendrogliales mediante un mecanismo no autónomo en la LGE. Por otra parte, demostramos que la isoforma de Ikaros Ik1 es esencial para la correcta generación de las neuronas encefalinérgicas estriatales a partir de la diferenciación de precursores neurales Dlx2 positivos de la LGE. Mostramos que Ik1 es necessario para sacar de ciclo los precursores que formarán el núcleo estriado mediante el incremento de los niveles del inhibidor de ciclinas p21. En consonancia con esta observación, la falta de Ikaros durante el desarrollo, afecta la neurogénesis tardía en el estriado. Esto se traduce en que el animal deficiente de Ikaros presenta un núcleo estriado más pequeño debido a una disminución en el número de neuronas de proyección encefalinérgicas de la matriz. Así, Nolz1 e Ikaros intervienen en diferentes momentos del desarrollo estriatal, siendo el papel de Nolz1 anterior y centrado en el control de precursores neurales, y el de Ikaros algo posterior, centrado en la diferenciación de neuronas estriatales de proyección encefalinégicas / The main goal of this work has been the study of two genetic factors implied in the differentiation of the striatal GABAergic projection neurons: Nolz1 and Ikaros. Moreover, we have studied the potential of these transcription factors to direct the differentiation of neural stem cells in vitro towards a striatal phenotype, in order to understand some aspects of the generation of this kind of neurons.We have demonstrated that the action of Nolz1 is involved in the specification of the neural precursors which reside in the SVZ ol the lateral ganglionic eminencie (LGE), the so-called basal progenitors. The cells positive for Nolz1 come from Gsh2 positive neural precursors, and its expression contributes to the inititation of a source of retinoic acid signalling within the striatum during development. Nolz1, in addition, regulates the Notch pathway in neural precursors an promotes the appearance of oligodendrocyte precursors in the LGE by a non-autonomous mechanism. On the other hand, we demostrate that the Ikaros isoform Ik1 is essential for the correct generation of the striatal enkephalinergic neurons from the differentiation of Dlx2 positive neural precursors of the LGE. We show that Ik1 is necessary for the cell-cycle exit of the neural precursors which will populate the striatum by the increase of the cyclin inhibitor p21. According with this observation, Ikaros absence during development specifically affects late striatal neurogenesis.This is translated in the adult Ikaros deficient animal in a reduced striatum due to a reduced number of matrix enkephalinergic projection neurons. Thus, Nolz1 and Ikaros exhert its actions during different times in striatal development, being Nolz1 role earlier and focused in the control of neural precursors, and Ikaros role occurs later, focused in the differentiation of the enkephalinergic projection neurons.

L'objectiu d'aquesta tesi doctoral ha estat el d'estudiar el comportament in vivo de les cèl·lules mare mesenquimàtiques derivades de teixit adipós (hAMSC), implantades en animals vius durant períodes extensos de temps, per a determinar la seva funcionalitat com a cèl·lules vehicle per a la teràpia gènica en tumors i per a la reparació de teixits.Per a dur a terme aquest objectiu es van marcar permanentment les cèl·lules hAMSC amb un vector lentivíric que contenia dos gens traçadors. Per una banda contenia el gen de la proteïna verda fluorescent (GFP) que ens va permetre la selecció de les cèl·lules marcades mitjançant la separació de cèl·lules activada per fluorescència, i per altra, el gen de la luciferasa de Photinus Pyralis (PLuc) que ens va permetre el seguiment no invasiu in vivo mitjançant la bioluminescència no invasiva (BLI). Aquestes cèl·lules, marcades i seleccionades, es van injectar en ratolins immunodeprimits on es van mantenir durant 8 mesos. Durant aquest període de temps, es va observar que aquestes cèl·lules es mantenien estables, que no formaven tumors i que no presentaven desequilibris cromosòmics greus.Posteriorment vam observar que les cèl·lules hAMSC també podien viure en tumors de pròstata (PC-3), inoculats en els músculs dels ratolins immunodeprimits, durant llargs períodes de temps i mantenir-se de manera estable. La detecció simultània de les cèl·lules tumorals i de les hAMSC va ser possible gràcies al marcatge de les cèl·lules amb diferents luciferases, la PLuc i la luciferasa de Renilla reniformis (RLuc). D'aquí es va concloure que aquestes cèl·lules eren vehicles segurs per a la teràpia cel·lular.Per portar a terme una teràpia gènica citotòxica en tumors, les cèl·lules hAMSC es van marcar amb un gen suïcida (timidina quinasa), de manera que gràcies a la mort d'aquestes cèl·lules suïcides quan s'administrava la prodroga (Ganciclovir) es produïa un efecte adjacent sobre les cèl·lules veïnes tumorals, fet que provocava la reducció dels tumors fins a un 98,5%. Amb la visualització dels dos tipus cel·lulars va ser possible determinar la dosi necessària de cèl·lules suïcides per obtenir un efecte adjacent major. A més, també es va poder quantificar la modulació del creixement que produïen les cèl·lules hAMSC en diferents tumors injectats de manera ortotòpica.Paral·lelament, el procediment de la BLI també ens va permetre determinar canvis en l'expressió d'un gen, el col·lagen 2 (COL2A1), el qual té un paper clau durant la condrogènesi: Les cèl·lules hAMSC es van transduir permanentment amb el gen de la PLuc, dirigit a partir del promotor específic del COL2A1, i es va observar una inducció de l'expressió de l'aquesta luciferasa, acompanyada també d'un canvifenotípic característic dels condròcits, quan es diferenciaven in vitro al llinatge condrogènic. Per tal de poder fer un seguiment in vivo, no invasiu, aquestes cèl·lules marcades es van transduir també amb la luciferasa RLuc, expressada constitutivament, per tal que fos l'indicador de la proliferació d'aquestes cèl·lules. Les cèl·lules hAMSC doblement marcades i sembrades en matrius d'os desmineralitzat (DBM) implantades subcutàniament en ratolins immunodeprimits van demostrar diferents patrons de diferenciació condrogència d'acord amb els resultats de les anàlisis histològiques. Aquest model, doncs facilitaria el desenvolupament de combinacions entre cèl·lules progenitores i esquelets per a la reparació de teixits. / The aim of this thesis was to study the behaviour of the human mesenchymal stromal cells derived from adipose tissue (hAMSCs) implanted in animals during prolonged time to determine their functionality as vehicles for genetic therapy in tumours and for tissue regeneration.For this purpose the hAMSCs were labelled by a permanent transduction with lentiviral vectors for the expression of two reporter gens. The green fluorescent protein (GFP) gene which proved to be useful for the enrichment of labelled cells, histological analysis and recovery of cells from tissue implants and the Photinus pyralis luciferase (PLuc) gene which allowed us the long term monitoring with the non-invasive bioluminescence imaging (BLI).The labelled and selected hAMSCs were injected in immunosupressed mice and maintained during 8 months. During this period, cells maintained a steady state and no detectable chromosomal abnormalities nor tumours formed during the 8 months of residence in the host's tissues.We also observed that hAMSCs could live long periods when implanted within PC-3 tumours, inoculated in the thighs of immunosupressed mice. The use of two luminescent reporters, allowed the simultaneous and independently monitoring in real time of two different cells populations implanted in the same anatomical site of the animal. Thus, from these observations we conclude that the hAMSCs could be safe vehicles for cell therapy.In order to perform a citotoxic gene therapy in PC-3 tumours, hAMSCs were labelled with a suicide gene (thymidine kinase). The addition of the prodrug (Gangiclovir) produced the death of these cells and killing of the neighbouring tumour cells (Bystander effect). This bystander effect produced a reduction of the tumours treated with suicide cells of 98.5% comparing with the control ones. The use of BLI and the dual labelling allowed us to optimize the ratio of the suicide vehicles to tumour cells to obtain a major bystander effect. Furthermore it was possible to quantify the tumour growth modulation produced by the injection of hAMSCs within different types of tumour cells.BLI procedures allowed us to analyze changes in gene expression and monitor cell differentiation in a live animal model of cartilage and bone formation.

Anti-Müllerian hormone (AMH) is a homodimeric glycoprotein that is best known for its role in regression of the Müllerian duct in the male fetus. Accumulating evidence indicates that AMH also has an important role during different physiological processes after birth. In contrast to other species, relatively little is known about AMH in the horse. In chapter one, developmental and seasonal changes in serum AMH concentrations in male horses were determined, and the use of AMH for determination of retained cryptorchid testes was established. In chapter two, the interrelationship between plasma AMH concentrations, antral follicle counts (AFC), and age in mares was evaluated. Molecular and hormonal changes in the equine follicle with regard to variations in antral follicle count and follicular development were examined in chapter three. In chapter four, the effect of AFC on age-related changes in follicular parameters in light-type horse mares was examined. Peripheral AMH concentrations were significantly higher in prepubertal colts than in postpubertal stallions and varied with season in mature stallions with higher concentrations during the physiological breeding season. Furthermore, serum AMH concentrations were significantly higher in cryptorchid stallions compared to intact stallions or geldings. Circulating AMH concentrations varied widely amongst mares of the same age while the repeatability of AMH was high within and between estrous cycles. More importantly, AMH concentrations were positively associated with AFC, and this relationship increased with mare age. In addition, variations in AMH concentrations or AFC were associated with molecular differences in granulosa cells of growing follicles, and the expression of AMH and genes co-expressed with AMH in the equine follicle as well as intrafollicular AMH concentrations decreased during follicular development. Finally, the inter-ovulatory interval and length of the follicular phase is increased in aged mares with low AFC. In conclusion, AMH is a useful biomarker for cryptorchidism in stallions and ovarian reserve in mares. Furthermore, follicular function was interrelated to AFC or AMH based upon molecular differences in growing follicles, while age-related changes in follicular parameters are linked to differences in AFC.

No description available.

Thesis--Paris V, 1973. / Includes bibliographical references (p. 809-815).

Thesis--Paris V, 1973. / Includes bibliographical references (p. 809-815).

Resumo: A fêmea da espécie eqüina é considerada monovulatória sazonal, o que é "ator limitante a produção de embriões ao longo do ano. Esta limitação poderia inimizada se houvesse uma resposta superovulatória eficiente em melhorar a ção de embriões. Protocolos mais recentes desenvolvidos em nosso atório utilizando-se o Extrato de Pituitária Eqüina (EPE) têm permitido uma esposta superovulatória. Contudo o número de embriões recuperados ainda sido inferior ao das ovulações, em conseqüência de fatores ainda não inados. O presente estudo teve por objetivo: verificar se o tratamento com o - administrado duas vezes ao dia, altera a maturação nuclear e citoplasmática I ito, avaliar o ambiente folicular mensurando os níveis de 17(3-estradiol, E5~)tlerona, progesterona, inibina e óxido nítrico, bem como o perfil eletroforético eínas no fluido folicular entre éguas superovuladas e não superovuladas. amos também o transporte do oócito para o oviduto. Este trabalho foi o em quatro experimentos: Experimento I "Estudo do transporte dos oócitos oviduto de éguas superovuladas com extrato de pituitária eqüina"; ento II "Efeito da superovulação na recuperação de oócitos quando da ~-es foliculares guiadas por ultra-sonografia"; Experimento 111 "Avaliação do e folicular de éguas superovuladas"; Experimento IV "Avaliação da '"'ação oocitária de éguas superovuladas com extrato de pituitária equina". O ento I" foi desenvolvido na Universidade de Rio Cuarto (Argentina), foram _za.:las 22 éguas de 3 - 12 anos, (09 éguas controles; 13 éguas tratadas _ . Estes animais foram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The equine female is considered a seasonal mono-ovulatory specie, which is a restrictive factor in respect to embryo production throughout the year. This limitation could be minimized if an efficient superovulatory response and consequent improvement of embryo production were possible. More recent protocols developed in our lab using EPE (equine pituitary extract) have allowed a good superovulatory response. However, the number of embryos recovered has been inferior to the number of ovulations detected due to unknown factors. The present study has the following objectives: Verify if the EPE treatment administered twice daily would alter the oocyte cytoplasmic and nuclear maturation; and to evaluate the follicular environment by measuring estradiol 17-, testosterone, progesterone, inhibin and nitric oxide. The electrophoresis pattern of proteins in follicular fluid from superovulated and non- superovulated mares was determined. In addition, the oocyte transport through the oviduct was investigated. The present study was divided into four experiments. Experiment I: Study of oocyte transport to the oviduct in superovulated mares using equine pituitary extract. Experiment II: Effect of superovulation on oocyte recovery using transvaginal ultrasound guided follicular aspiration. Experiment III: Evaluation of follicular environment in superovulated mares. Experiment IV: Oocyte maturation in superovulated in mares using equine pituitary extract. Experiment I was performed at Rio Cuarto University, Argentina. In the related study, 22 mares aging from 3 to 12 years were used (9 control mares, 13 EPE treated mares). These mares were monitored daily by ultrasound until the presence of a follicle ≥ 30mm in diameter, being then examined twice daily. The superovulation protocol used consisted in 25mg of EPE twice a day, intramuscularly, starting at day 7 post- ovulation... (Complete abstract click electronic access below) / Orientador: Marco Antonio Alvarenga / Coorientador: Fernanda da Cruz Landim e Alvarenga / Banca: Cezinande de Meira / Banca: Frederico Ozanam Papa / Banca: Rubens Pais de Arruda / Banca: Carlos Antonio de carvalho Fernandes / Doutor

O objetivo geral deste trabalho foi caracterizar o perfil protéico da secreção uterina pura, através da eletroforese bi-dimensional, de éguas em diferentes fases do ciclo estral, com diferentes graus de alterações inflamatórias e degenerativas, e com diferente capacidade de resposta à cobertura. Para tanto se realizaram cinco experimentos. O primeiro objetivou caracterizar o perfil protéico da secreção endometrial de éguas e determinar se essas proteínas estão associadas ao ciclo estral. A hipótese a ser testada é que o perfil protéico das secreções endometriais varia entre o estro e o diestro. Conclui-se que a composição protéica da secreção uterina da égua em estro é diferente daquela de éguas em diestro, podendo as diferenças protéicas estarem associadas tanto ao processo de manutenção e desenvolvimento embrionário, como a uma necessidade de eventual resposta inflamatória. O segundo experimento objetivou comparar as taxas de prenhez e morte embrionária em éguas não lactantes cobertas no primeiro, ou em outros ciclos durante a temporada reprodutiva. Foi concluído que: (a) durante a temporada reprodutiva, a fertilidade de éguas solteiras é menor no 1° ciclo que nos ciclos subseqüentes; (b) que uma taxa de morte embrionária maior pode ser esperada em éguas falhadas cobertas no 1° ciclo do que nos demais e (c) que a menor fertilidade observada no 1° ciclo não está relacionada à incidência de endometrite persistente pós-cobertura. O terceiro experimento objetivou comparar o perfil protéico da secreção endometrial e a expressão de receptores para esteróides ovarianos no endométrio de éguas em diestro após a 1ª ovulação e após a 2ª ovulação da temporada. Conclui-se que o ambiente uterino é diferente no primeiro diestro da temporada reprodutiva, comparado aos ciclos subseqüentes. O quarto experimento objetivou comparar o perfil protéico da secreção endometrial de éguas resistentes e susceptíveis à endometrite persistente pós-cobertura, durante o estro.Ahipótese a ser testada é que o ambiente uterino da égua susceptível encontra-se alterado no estro prévio à cobertura. Conclui-se que a composição da secreção endometrial das éguas susceptíveis, antes da cobertura, é diferente daquela observada nas éguas resistentes, estando as proteinas observadas relacionadas ao processo inflamatório e à contratilidade uterina. O quinto experimento objetivou (a) comparar a composição protéica da secreção endometrial de éguas em estro com e sem fibrose e (b) avaliar o efeito da inflamação endometrial sobre o perfil protéico da secreção uterina de éguas em estro e em diestro. A hipótese é que a fibrose e a inflamação alteram a composição protéica do fluído uterino, podendo prejudicar o desempenho reprodutivo da égua. Conclui-se que nas éguas em estro a inflamação e a fibrose endometrial alteram apenas a quantidade de poucas proteínas no ambiente uterino. Durante o diestro, a presença da inflamação alterou o ambiente uterino, havendo maior quantidade de proteínas inflamatórias. Os resultados apresentados neste trabalho requerem a confirmação da identidade das proteínas, através de seqüeciamento ou imuno identificação. No entanto, várias informações puderam ser obtidas e muitas novas perguntas podem ser geradas, em especial a partir dos resultados com as éguas susceptíveis. / The main objective from this study was the characterization of the protein profile by SDS-PAGE, from mares during the estrous cycle and mares with uterine inflammation, fibrosis and susceptibility to persistent post-mating endometritis. Five experiments were performed. The first aimed to evaluate the protein profile of endometrial secretions of mares and to determine if any of these proteins was associated with estrous cycle. It was concluded that protein profile from estrous mares is different from the profile from diestrous mares. This difference can be explained by requirements to support and develop the embryo or to an eventually inflammatory response. The second experiment aimed to compare pregnancy and embryo loss rates in non-lactating mares bred either in the first, or in other estrus cycles during the breeding season. It was concluded that: (a) during the breeding the fertility of non-lactating mares is lower in the 1st than in other estrus cycles season; (b) that a higher embryo loss rate may be expected in barren mares bred in the 1st than in other estrus cycles of the breeding season and (c) that the lower fertility rate observed during the 1st estrus cycle is not related to the incidence of post-breeding endometritis. The third experiment aimed to compare the protein profile of endometrial secretions and the steroid hormone receptor expression of the uterus from diestrous mares in the first, or in other estrous cycles during the breeding season. It was concluded that the uterine environment in the first diestrus of the breeding season is different in relation of the other diestrus. The fourth experiment aimed to compare the protein profile of endometrial secretions from estrous mares resistant or susceptible to persistent post-mating endometritis (PPME). The tested hypothesis was that before the insemination in susceptible mares the uterine environment is disturbed. It was concluded that there is a difference in the uterine environmentbetween resistant and susceptible mares to PPME, probably resulting from the inflammatory response and affecting the uterine contractility. The fifth experiment aimed (a) to compare the protein profile of endometrial secretions from estrous mares with and without fibrosis and (b) to estimate the effect of inflammation in the protein profile of endometrial secretion from mares in estrous and in diestrous. The tested hypothesis was that fibrosis and inflammation disturb the uterine environment modifying the protein profile of the endometrial secretion impairing the reproductive performance. It was concluded that inflammation and fibrosis in estrous influenced the protein profile in a low number of spots. During diestrous, the inflammation affect uterine environment with an expressive number of inflammatory proteins. The protein profile observed in the experiments must be confirmed by sequencing or immunoidentification. However, much information could be obtained but many others must be investigated, principally by the susceptible mare.

A endometrite é uma importante causa de subfertilidade na égua. Infecções uterinas repetidas ou persistentes poderiam levar ao desenvolvimento de fibrose periglandular. Os objetivos deste trabalho foram avaliar se os processos degenerativos do endométrio são influenciados por infecções bacterianas experimentais sucessivas; realizar uma avaliação histopatológica das biópsias endometriais para documentar os efeitos de diferentes tratamentos sobre o endométrio após infecções experimentais. Foram utilizadas vinte éguas resistentes, com histórico reprodutivo desconhecido, e cinco éguas susceptíveis, com histórico de endometrites recorrentes e subfertilidade. As vinte e cinco éguas foram classificadas nos seguintes grupos, de acordo com o grau de endometrite e endometrose: GI (n=4), GIIA (n=10), GIIB (n=8) e GIII (n=3). Após o primeiro exame histopatológico (amostra pré-infecção), as éguas foram sincronizadas com prostaglandina. Na fase estral, as éguas foram infectadas com 1 x 109 Streptococcus equi subsp. zooepidemicus. Constatada a presença de sinais clínicos de endometrite, os grupos de éguas foram distribuídos entre cinco diferentes tratamentos: leucócitos frescos, leucócitos congelados, leucócitos lisados, Interleucina-8 (Il-8) e grupo controle.As éguas foram tratadas diariamente, por, no máximo, quatro dias, ou até que o exame bacteriológico não evidenciasse o crescimento de Streptococcus. No quinto dia, as éguas eram submetidas a novo exame histopatológico (amostra pós-infecção) e no sétimo dia, todas as éguas eram tratadas com penicilina, independentemente de terem eliminado a infecção ou não. Sete dias após, as éguas eram novamente submetidas a exame histopatológico e sincronizadaspara realizar uma nova infecção e novo tratamento. As biópsias foram avaliadas quanto à endometrose e endometrite. Não se observaram diferenças significativas entre os graus de endometrose observados antes e no quinto dia após as cinco infecções experimentais. Da mesma forma, não foram observadas variações no grau de endometrose entre as biópsias realizadas antes das infecções, bem como entre as biópsias coletadas no quinto dia após a infecção. Não houve influência dos tratamentos sobre os graus de endometrose durante as 5 infecções experimentais. Entretanto, verificou-se variação significativa entre as diferentes éguas no grau de endometrose das biópsias uterinas coletadas antes e após a infecção experimental. Observou-se, nas éguas resistentes, neutrofilia e eosinofilia significativas nas biópsias do 5º dia pós-infecção, quando comparadas com as biópsias pré-infecção. Nas éguas susceptíveis, somente foi detectada eosinofilia, não se observando aumento do número de neutrófilos. Não houve aumento do número de linfócitos e plasmócitos nas biópsias pós-infecção, quando comparadas às pré- infecção, nas éguas susceptíveis e resistentes. Os tratamentos não influenciaram, nas éguas resistentes e susceptíveis, a migração de neutrófilos no quinto dia, quando comparada com a observada antes da infecção. Conclui-se que infecções experimentais sucessivas durante 13 meses não influenciaram o grau médio de endometrose, apesar da variabilidade ocorrida entre as éguas. Esta variação provavelmente se deva a uma baixa representatividade de uma única amostra de biópsia na avaliação somente do grau de degeneração endometrial. Conclui-se, também, que éguas susceptíveis à endometrite, com presença de Streptococcus no útero, não apresentam neutrofilia cinco dias após a infecção. Provavelmente, o menor tempo de eliminação bacteriana observada nos tratamentos com leucócitos frescos e congelados deva-se a outros fatores que não o efeito quimioatraente leucocitário. / Endometritis is an important cause of subfertility in the mare. Repetitive or persistent uterine infections could lead to the development of periglandular fibrosis. The objectives of this study were: - to evaluate if degenerative endometrial diseases are influenced by repetitive experimental bacterial infections; - to determine the effect of different treatments on the endometrium after experimental infections by means of histopathological evaluation of endometrial biopsies. Twenty resistant mares, with unknown reproductive history, and five susceptible mares, with history of recurrent endometritis and subfertility, were used. Mares were classified, according to the degree of endometritis and endometrosis, within the following groups: GI (n=4), GIIA (n=10), GIIB (n=8) and GIII (n=3). Cycles were synchronized with prostaglandin after the first histopathological examination (pre-infection sample). During estrus, mares were infected with 1 x 109 Streptococcus equi subsp. zooepidemicus. Twenty four hours after the inoculation, clinical, bacteriological and cytological examinations were performed. When endometritis clinical signs were detected, the groups of mares were distributed into five different treatments: fresh leukocytes, frozen leucocytes, lysed leucocytes, Interleukin-8 (Il-8) and control group. Mares were treated on a daily basis for no more than four days, or until there was no Streptococcus growth in bacteriological examination. On the fifth day, mares were submitted to a new histopathological examination (post-infection sample) and, on the seventh day, all the mares were treated with penicillin, independently of having eliminated infection, or not. Seven days after, mares were submitted to a new histopathological examination and synchronized in order to proceed to a new infection and a new treatment. Biopsies were evaluated for endometritis and endometrosis. Therewas no significant difference regarding the degree of endometrosis before and on the fifth day after the five infections. Similarly, there was no difference regarding the degree of endometrosis among biopsies performed before infections and among biopsies performed on the fifth day after infections. Treatments did not influence the degree of endometrosis during the five experimental infections. Anyway, there was a significant variation between different mares, according to the degree of endometrosis, in biopsies collected before, as well as in biopsies collected after experimental infection. Resistant mares showed significant neutrophilia and eosinophilia in biopsies collected on the fifth day after infection, compared to pre-infection samples. Susceptible mares showed eosinophilia, but no growth in neutrophil number. There was no growth in lymphocyte and plasma cell number in post-infection biopsies, if compared to pre-infection biopsies, either in susceptible, or in resistant mares. In the same way, treatments did not influence neutrophil migration on the fifth day post-infection, if compared to pre-infection, either in susceptible, or in resistant mares. It was concluded that repetitive experimental infections do not influence the average degree of endometrosis, in spite of the variability between mares. This variability is probably due to the low representation of one single biopsy sample in the evaluation of the degree of endometrial degeneration. It was also concluded that susceptible mares showing Streptococcus in uterus do not present with neutrophil growth five days after infection. The shorter time required for bacterial elimination when fresh and frozen leukocytes were used is probably due to other factors than leukocyte chemoattractive effect.