ABSTRACT
A subfertilidade em éguas é um problema comum e uma importante causa de perdas econômicas. A redução da fertilidade é um multifatorial e, apesar de muitas vezes estar relacionada a problemas uterinos, as causas originadas de alterações oocitárias, ovarianas e endócrinas são muito frequentes e de difícil diagnóstico. A presente revisão tem como objetivo discutir as causas e o diagnóstico da subfertilidade em éguas relacionadas às alterações endócrinas e ovarianas
Subfertility in mares is a common problem and an importante cause of economic losses. Reduced fertility is multifactorial and, although it is often related to uterine problems, altered oocyte quality and endocrine profiles are frequent and of complex diagnosis. The present review aims to discuss causes and diagnosis of subfertility in mares related to endocrine and ovarian problems.
Subject(s)
Female , Animals , Horses/physiology , Endocrine System Diseases/diagnosis , Infertility, Female/diagnosis , Infertility, Female/physiopathologyABSTRACT
A utilização de éguas receptoras cíclicas e acíclicas nos programas de transferência de embriões (TE) é uma prática consagrada na reprodução equina. Uma alternativa vantajosa para criadores e veterinários é o uso das receptoras acíclicas, uma vez que viabiliza a antecipação da estação de monta e reduz o manejo com as receptoras. Para se estabelecer a gestação nestas receptoras, estrógenos e progestinas são administrados, de forma a simular o ambiente hormonal uterino de éguas que se tornam naturalmente gestantes. A administração de estrógenos previamente às progestinas é baseada nos estudos em éguas cíclicas, que mostram que o estradiol, presente no período de estro, estimula a expressão dos seus próprios receptores e dos receptores para progesterona no endométrio. A progesterona, por sua vez, provoca mudanças uterinas que possibilitam o estabelecimento e manutenção da gestação e leva a redução dos receptores de estradiol e de seus próprios receptores durante o diestro e início da gestação. No entanto, pouco se sabe sobre os receptores endometriais de estradiol e progesterona em éguas acíclicas, principalmente utilizadas em programas de TE. O presente trabalho revisa o padrão de expressão gênica dos receptores endometriais de estradiol e progesterona em éguas durante o ciclo estral, início da gestação e submetidas a tratamentos hormonais com estrógenos e progestinas exógenas.
The use of cyclic and non cyclic recipient mares in embryo transfer (ET) programs is a well established practice in equine reproduction. An advantageous alternative for horse owners and veterinarians is the use of non-cyclic recipients, since it makes possible the anticipation of the breeding season and reduces handling with the recipients. In order to establish pregnancy in the non-cyclic recipients, estrogens and progestins are administered to allow the induction of similar endometrial changes to those which occur in naturally pregnant mares. Administration of estradiol prior to progestins is based on cyclic mares researches, where estradiol produced during estrous stimulates the expression of estrogen and progesterone receptors in the endometrium. On the other hand, progesterone causes uterine changes that allow pregnancy establishment and maintenance. In addition, progesterone leads to reduction of estrogen and progesterone receptors during diestrous in cyclic mares. However, little is known about estrogen and progesterone endometrial receptors in non-cyclic mares, especially used in ET programs. The current study revises the gene expression pattern of estradiol and progesterone endometrial receptors in mares during estrous cycle, early pregnancy and submitted to estrogens and progestins hormonal treatments.
Subject(s)
Female , Animals , Horses , Gene Expression , Gonadal Steroid Hormones , Receptors, Estradiol/analysis , Receptors, Progesterone/analysis , Estrogens , ProgestinsABSTRACT
A utilização de éguas receptoras cíclicas e acíclicas nos programas de transferência de embriões (TE) é uma prática consagrada na reprodução equina. Uma alternativa vantajosa para criadores e veterinários é o uso das receptoras acíclicas, uma vez que viabiliza a antecipação da estação de monta e reduz o manejo com as receptoras. Para se estabelecer a gestação nestas receptoras, estrógenos e progestinas são administrados, de forma a simular o ambiente hormonal uterino de éguas que se tornam naturalmente gestantes. A administração de estrógenos previamente às progestinas é baseada nos estudos em éguas cíclicas, que mostram que o estradiol, presente no período de estro, estimula a expressão dos seus próprios receptores e dos receptores para progesterona no endométrio. A progesterona, por sua vez, provoca mudanças uterinas que possibilitam o estabelecimento e manutenção da gestação e leva a redução dos receptores de estradiol e de seus próprios receptores durante o diestro e início da gestação. No entanto, pouco se sabe sobre os receptores endometriais de estradiol e progesterona em éguas acíclicas, principalmente utilizadas em programas de TE. O presente trabalho revisa o padrão de expressão gênica dos receptores endometriais de estradiol e progesterona em éguas durante o ciclo estral, início da gestação e submetidas a tratamentos hormonais com estrógenos e progestinas exógenas. (AU)
The use of cyclic and non cyclic recipient mares in embryo transfer (ET) programs is a well established practice in equine reproduction. An advantageous alternative for horse owners and veterinarians is the use of non-cyclic recipients, since it makes possible the anticipation of the breeding season and reduces handling with the recipients. In order to establish pregnancy in the non-cyclic recipients, estrogens and progestins are administered to allow the induction of similar endometrial changes to those which occur in naturally pregnant mares. Administration of estradiol prior to progestins is based on cyclic mares researches, where estradiol produced during estrous stimulates the expression of estrogen and progesterone receptors in the endometrium. On the other hand, progesterone causes uterine changes that allow pregnancy establishment and maintenance. In addition, progesterone leads to reduction of estrogen and progesterone receptors during diestrous in cyclic mares. However, little is known about estrogen and progesterone endometrial receptors in non-cyclic mares, especially used in ET programs. The current study revises the gene expression pattern of estradiol and progesterone endometrial receptors in mares during estrous cycle, early pregnancy and submitted to estrogens and progestins hormonal treatments. (AU)
Subject(s)
Animals , Female , Horses , Gene Expression , Receptors, Estradiol/analysis , Receptors, Progesterone/analysis , Gonadal Steroid Hormones , Estrogens , ProgestinsABSTRACT
Os programas comerciais de transferência de embriões em éguas existem por mais de três décadas e são hoje uma das biotécnias mais utilizadas na reprodução assistida de equinos. O exame ultrassonográfico nos períodos pré e pós-cobertura de doadoras de embriões, assim como a avaliação de receptoras no momento da inovulação é de vital importância para o êxito de um programa de transferência de embriões. A ultrassonografia Doppler é uma técnica não-invasiva que permite a avaliação em tempo real da hemodinâmica do trato reprodutivo de animais de grande porte. Por fornecer detalhes anatômicos e informações imediatas sobre a fisiologia do fluxo sanguíneo de tecidos e órgãos, o exame doppler permite a avaliação do potencial ovulatório de folículos e do status funcional de corpo lúteo e útero, além de ser uma técnica auxiliar para o diagnóstico de distúrbios na hemodinâmica do sistema reprodutivo. Alterações na perfusão sanguínea dos futuros folículos dominantes são detectáveis em diferentes fases de seu desenvolvimento, como na divergência folicular e no período pré-ovulatório. A partir dessas informações, é possível determinar o princípio da atividade sexual e o momento ideal para o início de tratamentos superovulatórios e indutores de ovulação, assim como o momento mais apropriado para a realização de coberturas de éguas doadoras de embriões. A avaliação através do modo-Doppler do corpo lúteo e útero de éguas receptoras é também um instrumento auxiliar para a seleção de animais com perfil sérico de progesterona e ambiente uterino adequados para a sobrevivência do embrião e manutenção da gestação. Essa técnica pode ser útil ainda ao se avaliar a interação concepto-maternal. Apesar da aplicabilidade da tecnologia doppler dentro de programas de transferência de embriões, novos estudos visando a determinar padrões de normalidade e posterior caracterização de distúrbios de fluxo sanguíneo de trato reprodutivo ainda se fazem necessários.
Embryo transfer in mares has been commercially used for more than three decades and it is one of most frequently applied biotechnologies on equine reproduction. Ultrasonic doppler exam of donors during the pre and post-breeding and recipients evaluation at the embryo transfer moment is essential for embryo transfer program success. Doppler ultrasonography is a non-invasive technic that allows real-time evaluation of the reproductive system hemodynamics in large animal. For providing anatomical details and blood-flow physiologic information of vessels and tissues, doppler exam can be used for ovulation prognostication, and to evaluate uterine and luteal functional status. Additionally, it can serve as a diagnostic aid of hemodynamic disturbance in reproductive system. Vascularity changes of future ovulatory follicles precede the diameter deviation. Based on this, it is possible to estimate the beginning of the breeding season and the best moment to initiate superovulatory treatments. Moreover, follicular blood flow can be used to decide the most appropriated moment for ovulation induction and breeding of donors mares. Uterine and luteal evaluation using Doppler-mode in mares can be useful to select embryo recipients with satisfactory progesterone production and adequate uterine vascularity for embryo development and maintenance of pregnancy. The maternal recognition of pregnancy also can be evaluated. Although the applicability of the Doppler technology in embryo transfer programs, additional studies are necessary to determine the standards of normality and to characterize different blood-flow disturbances of the reproductive system.
ABSTRACT
Background: Doppler ultrasonography is a non-invasive real time pulse-wave technique recently used for the transrectal study of the reproductive system hemodynamics in large animals. This technic is based in the Doppler Effect Principle that proposes the change in frequency of a wave for an observer (red blood cells) moving relative to the source of the respective wave (ultrasonic transducer). This method had showed to be effective and useful for the evaluation of the in vivo equine reproductive tract increasing the diagnostic, monitoring, and predictive capabilities of theriogenology in mares. However, an accurate and truthful ultrasonic exam requires the previous knowledge of the Doppler ultrasonography principles. Review: In recent years, the capabilities of ultrasound flow imaging have increased enormously. The current Doppler ultrasound machines offer three methods of evaluation that may be used simultaneously (triplex mode). In B-mode ultrasound, a linear array of transducers simultaneously scans a plane through the tissue that can be viewed as a two-dimensional gray-scale image on screen. This mode is primarily used to identify anatomically a structure for its posterior evaluation using colored ultrasound modes (Color or Spectral modes). Colored ultrasound images of flow, whether Color or Spectral modes, are essentially obtained from measurements of moving red cells. In Color mode, velocity information is presented as a color coded overlay on top of a B-mode image, while Pulsed Wave Doppler provides a measure of the changing velocity throughout the cardiac cycle and the distribution of velocities in the sample volume represented by a spectral graphic. Color images conception varies according to the Doppler Frequency that is the difference between the frequency of received echoes by moving blood red cells and wave frequency transmitted by the transducer. To produce an adequate spectral graphic it is important determine the position and size of the simple gate. Furthermore, blood flow velocity measurement is influence by the intersection angle between ultrasonic pulses and the direction of moving blood-red cells (Doppler angle). Objectively colored ultrasound exam may be done on large arteries of the reproductive tract, as uterine and ovary arteries, or directly on the target tissue (follicle, for example). Mesovarium and mesometrium attachment arteries also can be used for spectral evaluation of the equine reproductive system. Subjectively analysis of the ovarian and uterine vascular perfusion must be done directly on the corpus luteum, follicular wall and uterus (endometrium and myometrium associated), respectively. Power-flow imaging has greater sensitivity to weak blood flow and independent of the Doppler angle, improving the evaluation of vessels with small diameters and slow blood flow. Conclusion: Doppler ultrasonography principles, methods of evaluation and reproductive system anatomy have been described. This knowledge is essential for the competent equipment acquisition and precise collection and analysis of colored ultrasound images. Otherwise, the reporting of inconsistent and not reproducible findings may result in the discredit of Doppler technology ahead of the scientific veterinary community.
Subject(s)
Animals , Female , Ovary , Urogenital System/diagnostic imaging , Fertilization , Horses , Myometrium , Ultrasonics , Ultrasonography, DopplerABSTRACT
Background: Studies with Doppler ultrassonography started at the end of the 90s for the determination of physiological and pathological alterations in the reproductive tract of the mare. Uterine alterations caused by inflammation, response from seminal plasma infusion, hormonal variations during estrous and diestrus, pregnancy and action of various vasoactive factors influence on the vascular perfusion detected by Doppler ultrasound. The development of efficient methods for uterine quality evaluation is of big importance for field equine reproduction veterinarians, once uterine environment is responsible for pregnancy maintenance. Review: Nowadays, the most used methods of uterine evaluation are the mode B ultrassonography, cytology, culture and biopsy. Hemodynamic evaluation of the uterus can be done by spectral data collected from large vessels, as A. uterine and its ramifications, or from subjective or objective evaluations from endometrium, miometrium and mesometrium attachment, which provide data referent to local and specific alterations of the evaluated area. Alterations in uterine vascular perfusion has been detected during estrous cycle, during pregnancy and in cases of infusion of inflammatory substances. These alterations happen because of vasoactive substances that act in the uterus during these events, however, most of these vasoactive substances are probably not even known. Also, important hemodynamic alterations in old mares, as an increase in vascular resistance, have been described. This increase might result from fibrosis of the uterus and in women it is considered to be a cause of infertility. In mares, periglandular fibrosis of the endometrium is considered to be the major diagnosable cause of embryonic and fetal loss in older mares. For the CL, ovarian artery of the mare supplies the ovary as well as the oviduct and therefore can be used for evaluation of these areas. The CL evaluation can also be done by the percentage of luteum area with colored signals as an indicator of the extent of blood flow. The percentage of the CL area with colored signals is determined subjectively by images observations in real time and/or by a freezing Power Doppler cross-section image with the maximum number of color pixels taped and the total number of color pixels is assessed by a computer analysis system. Therefore, a high correlation between plasmatic progesterone and CL vascularization also allows the CL evalution by this technique. In a first report, CL circulation reached its maximum on D5, the progesterone concentration in peripheral blood increased until D7 and in a posterior report, maximum perfusion was achieved two days after the maximum progesterone concentration (D8). Blood flow reduced between D10 - D14 some days before the plasma progesterone decrease and, during the luteolytic period (D15 - D17), the decline in CL blood-flow area was greater than blood flow decrease. Conclusion: Doppler ultrassonography add knowledge about uterine viability and CL functionality can be easily used by veterinarians in the field. It is a noninvasive method that provides real time results. However, because of the short time studies in this area have been done, many other answers still need to be found until normal and pathological patterns will be established.