Histological comparison of the smooth uterine muscle of healthy golden retriever bitches, carriers of the progressive muscular dystrophy (GRMD) gene, and GRMD-affected bitches

Development of the cardiorespiratory system in dogs from days 16 to 46 of pregnancy

Dogs have been studied for several reasons, such as the genetic improvement, their use as experimental models, in zoonotic research, cell therapy and as a model for human diseases. However, many features relating to the embryonic development of dogs remain unknown because of the absence of embryological studies. Considering the importance of the cardiorespiratory system in the development of embryos, the aim of this study was to investigate the development of the main cardiorespiratory organs of dog embryos and foetuses with estimated gestational ages from 16 to 46 days using macro- and microscopic descriptions. On day 16 of development, the neural tube and crest were formed, the anterior and posterior neuropore closure had begun and the somites had developed. Between days 22 and 27 of gestation, the lung buds and the initial formation of the primary bronchi and heart chambers were observed. The heart chambers exhibited the endo-, myo- and epicardial layers but did not have obvious differences in thickness among each other. Between days 41 and 46 of gestation, the nasal conchae and septa and trachea were formed, which exhibited characteristic epithelia. The lung formation and lobation were complete. The heart and major vessels exhibited mature histological architecture when their anatomical development was complete. The results of this study contribute to a more accurate definition of the embryonic and foetal developmental stages in dogs.

Profiles of Steroid Hormones in Canine X-Linked Muscular Dystrophy via Stable Isotope Dilution LC-MS/MS

Golden retriever muscular dystrophy (GRMD) provides the best animal model for characterizing the disease progress of the human disorder, Duchenne muscular dystrophy (DMD). The purpose of this study was to determine steroid hormone concentration profiles in healthy golden retriever dogs (control group - CtGR) versus GRMD-gene carrier (CaGR) and affected female dogs (AfCR). Therefore, a sensitive and specific analytical method was developed and validated to determine the estradiol, progesterone, cortisol, and testosterone levels in the canine serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). To more accurately understand the dynamic nature of the serum steroid profile, the fluctuating levels of these four steroid hormones over the estrous cycle were compared across the three experimental groups using a multivariate statistical analysis. The concentration profiles of estradiol, cortisol, progesterone, and testosterone revealed a characteristic pattern for each studied group at each specific estrous phase. Additionally, several important changes in the serum concentrations of cortisol and estradiol in the CaGR and AfCR groups seem to be correlated with the status and progression of the muscular dystrophy. A comprehensive and quantitative monitoring of steroid profiles throughout the estrous cycle of normal and GRMD dogs were achieved. Significant differences in these profiles were observed between GRMD and healthy animals, most notably for estradiol. These findings contribute to a better understanding of both dog reproduction and the muscular dystrophy pathology. Our data open new venues for hormonal behavior studies in dystrophinopathies and that may affect the quality of life of DMD patients.