Proliferation patterns in the canine endometrium during the estrous cycle

Proliferation and apoptosis studies of interplacental areas after aglepristone treatment for planned cesarean section in pregnant bitches

Background and Aim

Progesterone (P4) is the main hormone for pregnancy maintenance, occurring approximately 62-64 days after ovulation in bitches. Progesterone acts by binding to specific receptors. Aglepristone is a progesterone receptor (PR) antagonist with a higher affinity for PR binding. There are no published studies on cell proliferation and apoptosis in the canine uterus at the time of parturition. Therefore, this study aimed to determine the local effects of aglepristone on cell proliferation and apoptosis of interplacental uterine tissue during planned cesarean section (C-section) in bitches.

Materials and Methods

In this study, 13 client-owned French bulldogs were examined. Bitches were divided into treatment (n = 8) and control (n = 5) groups. Ovulation timing was predicted based on the serum P4 level on 62-64 days post-ovulation for parturition. Serum P4 levels were measured before (on 60-day post-ovulation) and on C-section day (on 61-day post-ovulation). Aglepristone (Alizine®), 15 mg/kg subcutaneously (SC), was administered on 60 days post-ovulation in the treatment group. A C-section was planned 20-24 h later, and interplacental uterine areas were collected from both groups during the C-section. Immunohistochemistry based on Ki-67 and TUNEL assay was used to evaluate cell proliferation and apoptosis in four different interplacental uterine tissue layers (epithelium, stroma, glandular epithelium, and myometrium). Data are reported as mean ± standard deviation. Kruskal-Wallis test was used for comparisons of more than two independent groups. P value of 0.05 was considered statistically significant.

Results

One bitch in the treatment group was excluded due to emergency C-section 8 h after aglepristone administration. Serum P4 levels (ng/mL) at 20-24 h before and at C-section were 6.09 ± 2.72 and 4.32 ± 2.2 in the treatment group (n = 7) and 5.45 ± 1.28 and 3.67 ± 1.89 in the control group (n = 5), respectively. Proliferation (PI) and apoptotic (AI) indices were <5% and >45%, respectively, in both the treatment (n = 5) and control (n = 3) groups. PI and AI were detected at interplacental areas.

Conclusion

There were no significant differences in serum P4 levels or PI and AI indices between the groups. The PI <5% and AI was higher than 45% in both groups. Aglepristone did not have a direct effect on the serum P4 levels in both groups. These results correlated with the natural physiology of parturition preparation. Aglepristone 15 mg/kg SC injected 20-24 h before parturition had no effect on the P4 level, nor were any harmful effects observed for a planned C-section in pregnant bitches.

Lipid droplet dynamics in healthy and pyometra-affected canine endometrium

BACKGROUND

Accumulation of lipid droplets (LDs) was recently observed in pyometra-affected uteri. As data about their nature and function are missing we intended to compare the localization, quality and quantity of LDs in canine healthy and pyometra-affected tissues and in an in vitro model.

METHODS AND RESULTS

We characterized LDs in healthy and pyometra uterine tissue samples as well as in canine endometrial epithelial cells (CEECs) in vitro by means of histochemistry, immunohistochemistry, transmission electron microscopy, western blot, and RT-qPCR. Oil Red O (ORO) staining and quantification as well as p-phenylenediamine staining showed a higher number of LDs in epithelial cells of pyometra samples. Immunohistochemistry revealed that the amount of LDs coated by perilipin2 (PLIN2) protein was also higher in pyometra samples. Transmission electron microscopy showed an increase of LD size in surface and glandular epithelial cells of pyometra samples. In cell culture experiments with CEECs, supplementation with oleic acid alone or in combination with cholesterol lead to an increased LD accumulation. The expression of PLIN2 at protein and mRNA level was also higher upon oleic acid supplementation. Most LDs were double positive for ORO and PLIN2. However, ORO positive LDs lacking PLIN2 coating or LDs positive for PLIN2 but containing a lipid class not detectable by ORO staining were identified.

CONCLUSIONS

We found differences in the healthy and pyometra-affected endometrium with respect to LDs size. Moreover, several kinds of LDs seem to be present in the canine endometrium. In vitro studies with CEECs could show their responsiveness to external lipids. Since epithelial cells reacted only to oleic acid stimulation, we assume that the cyclic lipid accumulation in the canine endometrium is based mainly on triglycerides and might serve as energy provision for the developing early embryo. Further studies are necessary to verify the complex role of lipids in the healthy and pyometra-affected canine endometrium.

High-definition ultrasonography in the evaluation of the reproductive tract of bitches during the follicular phase of the estrous cycle

The aim was to sonographically evaluate the reproductive tract of bitches during the follicular phase of the estrous cycle using High Density (HD) ultrasonic techniques. Females (n = 8) were evaluated at five different times throughout the follicular phase, as determined by vaginal cytology and blood progesterone concentrations. Ultrasonic exams were performed using the ACUSON S2000/SIEMENS device utilizing a multifrequency HD transducer (5.5-18 MHz). Videos of the ovaries were obtained and recordings were evaluated using a DICOM viewer software for counting and measuring the ovarian structures, which were assigned to groups based on diameter in mm: G1: ≤ 1; G2: from 1.01 to 3.5; G3 from 3.51 to 5.5; G4: from 5.51 to 10. There was a greater uterine thickness with the progression of the follicular phase (P < 0.05). Six distinct regions were identified in the uterine wall. The ovarian dimensions increased (P < 0.05) as stage of the follicular phase advanced. There was fluid detected around the ovaries after ovulation. There was a characteristic fat tissue hyperechogenicity around the ovaries at all timepoints. There was a difference in the number of ovarian structures of each dimension group at each time there were assessments (P < 0.05). There was a difference in diameter of the largest ovarian structure and in average value of wall thickness at all timepoints when there were evaluations (P < 0.05). The HD ultrasonography technique provides for excellent image resolution, allowing for a more precise characterization of the bitch's reproductive structures and changes occurring during the follicular phase of the estrous cycle.

Pyometra-associated insulin resistance assessment by insulin binding assay and tyrosine kinase activity evaluation in canine muscle tissue

Diestrus is associated with insulin resistance in bitches and pyometra can further impair insulin sensitivity. This study aimed to compare insulin sensitivity, insulin binding, and tyrosine kinase activity in bitches in anestrus, diestrus, or with pyometra. Patients submitted to elective ovariohysterectomy were divided into anestrus (n = 11) or diestrus (n = 13) according to reproductive history, vaginal cytology, and uterine histology. The group pyometra (n = 8) included bitches diagnosed with the disease based on clinical presentation and abdominal ultrasound findings and further confirmed by uterine histopathology. All patients were submitted to an intravenous glucose tolerance test (IVGTT) before ovariohysterectomy, and rectus abdominis muscle samples were collected during surgery for plasmatic membrane suspension preparation. Muscle-membranes were submitted to cold saturation insulin binding assay for dissociation constant (Kd) and maximum binding capacity (Bmax) determination, as well as exogenous substrate Poly (Glu: Tyr 4:1) phosphorylation assay for basal tyrosine kinase evaluation. Bitches with pyometra showed higher basal insulin (P < 0.001) and higher area under the curve (AUC) for insulin (P = 0.01) and glucose (P < 0.001) response during the IVGTT in comparison with bitches in anestrus or diestrus. Diestrus (P < 0.0001) and pyometra (P = 0.001) were associated with reduced tyrosine kinase activity in comparison with anestrus. No differences were documented in Kd and Bmax results for the low-affinity/high-capacity insulin receptors; however, high-affinity/low-capacity insulin receptors showed higher Kd and Bmax results in bitches in diestrus or with pyometra (P < 0.05) in comparison with anestrus. Despite the pyometra group showed the highest Kd values (P < 0.01), its Bmax results did not differ from the diestrus group (P > 0.05). Diestrus' higher Kd values and reduced tyrosine kinase activity in muscle tissue were compensated by increased total insulin binding capacity. Absent differences in IVGTT results between diestrus and anestrus bitches corroborate this finding. However, in bitches with pyometra, the highest Kd values were not compensated by increased total insulin binding capacity. This finding was associated with insulin resistance and glucose intolerance in IVGTT results. Moreover, pyometra resolution restored insulin sensitivity and glucose tolerance. These features can play a key role in pyometra-associated CDM, as well as in diabetic remission after pyometra resolution.

Molecular studies on oestrogen α and progesterone receptors and histomorphometric analysis of canine uteri following aglepristone treatment

Aglepristone, a competitive progesterone antagonist, is successfully used in various progesterone-dependent conditions. This study investigated uterine histomorphometric analysis, and expressions of the oestrogen α receptor (ERα) and progesterone receptor (PR) in uteri of bitches following the single dose of aglepristone treatment. Twelve client-owned healthy diestrous bitches were used in the study. The single dose of aglepristone (Alizine^® , 10 mg/kg) was injected subcutaneously 5 days before ovariohysterectomy in the treatment group (n = 6); bitches without treatment served as a control group (n = 6). Uteri were collected for histomorphometric analysis, ERα and PR gene, and protein expressions studies. The mRNA expressions of ERα and PR were determined by RT-qPCR. Immunohistochemical analysis was used to evaluate the ERα and PR protein expressions using an H-score in five parts of the uterus. The results demonstrated glandular epithelium height significantly decreased (p < .05) and ERα mRNA increased (p < .01) in treated dogs. Of the treated bitches, lower expression levels of ERα were observed in the luminal epithelium, crypt and glandular epithelium, with higher expression in the endometrial stroma and myometrium (p < .05); however, PR expression decreased in the luminal epithelium, crypt and glandular epithelium (p < .01). In conclusion, reduction of the uterine glandular epithelium and ERα mRNA upregulation together with changes in ERα and PR expressions were observed in the treated bitches. However, changes in uterine ERα and PR expressions in the treated bitches depended on tissue layers. The treatment had no effect on serum oestradiol and progesterone levels.

Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.

Endometrial Status in Queens Evaluated by Histopathology Findings and Two Cytological Techniques: Low-Volume Uterine Lavage and Uterine Swabbing

Simple Summary

The endometrium health of feline queens can be difficult to assess due to the reduced size of the uterus, which hinders representative biopsy sampling. This may result in limitations in diagnosing endometritis, and consequently in detecting infertility problems. Although histology is considered the most reliable technique for diagnosing endometritis in many species, cytology is also gaining importance and may be an alternative tool for evaluating the endometrium in small species. Two different common cytological techniques (uterine lavage and uterine swabbing) were compared to determine the reliability of cytology for evaluating the endometrium status in queens. Histopathological and bacteriological information was used for the control methods. Our results demonstrated that cytology may be a useful diagnostic tool for assessing the endometrial status. In addition, when comparing cytological techniques, the uterine lavage method was more representative than uterine swabbing.

Abstract

Endometritis is associated with fertility problems in many species, with endometrial biopsy being the main diagnostic tool. In feline queens, the reduced size of the uterus may make it difficult to obtain representative diagnostic samples. Endometrial cytology may represent a valuable diagnostic tool for evaluating the health status of the endometrium in queens. Fifty domestic shorthair queens were included and divided into two cytological diagnostic technique groups, the uterine lavage (UL; n = 28) and uterine swabbing (US; n = 22) groups. Cytological results were compared with histopathological and bacteriological information. Changes in the histopathological patterns were also evaluated and compared with progesterone levels to confirm previous published data. Furthermore, the results from both cytological sampling methods were compared to evaluate the utility of each method. Endometritis was ruled out in all queens by means of histology and microbiology. Leukocyte counts and red blood cell/endometrial cell ratios were significantly higher in US than UL samples. Additionally, UL sampling is less affected by blood contamination and cells are better preserved. The combination of endometrial cytology and uterine culture might be useful for evaluating the endometrial characteristics in queens. The UL evaluation method is more representative of the actual endometrial status than the US technique.

Do arachidonic acid metabolites affect apoptosis in bovine endometrial cells with silenced PPAR genes?

Peroxisome proliferator-activated receptors (PPARs) are expressed in bovine uterus, and their agonists are arachidonic acid (AA) metabolites. We hypothesised that silencing of PPAR genes in bovine endometrial stromal cells (ESC) would change the intracellular signalling through PPAR and affect apoptosis after cell treatment with different AA metabolites. The study's aims are detection of apoptosis and examining the influence of prostaglandins and leukotrienes on apoptosis occurring in physiological ESC and cells with silenced PPAR (α, δ, and γ) genes. Silencing the PPARα and PPARδ genes in cells resulted in increased DNA fragmentation and mRNA and protein expression of caspase (CASP) -3 and -8 (P < 0.05). Neither DNA fragmentation nor the mRNA and protein expression of CASP3 and -8 in cells with silenced PPARγ gene were changed compared to physiological cells (P > 0.05). Among PPARs, PPARα and PPARδ appear to inhibit apoptosis, and AA metabolites, as PPAR agonists, modify this process in bovine ESC.

Morphological Characteristics and Expression of Estrogen and Progesterone Receptors in the Canine Endometrium During the Estrus Cycle, Cystic Endometrial Hyperplasia and Pyometra

The estrus cycle of bitches is divided into four phases: proestrus, estrus, diestrus and anestrus, during which different morphological changes, and also cyclic changes of estrogen and progesterone receptors are present. Several pathological changes can be differentiated on the endometrium, but one of these is the most important - cystic endometrial hyperplasia, which frequently develops into pyometra. The aim of the present study was to describe morphological characteristics, and expression of estrogen and progesterone receptors on the endometrium of mixedbreed bitches during the different phases of the estrus cycle, cystic endometrial hyperplasia and pyometra. The uterus and ovaries of 36 mixed breed bitches in different phases of the estrus cycle and also with cystic endometrial hyperplasia (CEH) and chronic purulent endometritis - pyometra were examined macroscopically, histopathologically, and immunohistochemically for estrogen receptors (ΕR) and progesterone receptors (PR). During proestrus uterine cells showed a weak reaction for both estrogen and progesterone receptors, but during estrus a large number of uterine cells showed a strong reaction on estrogen receptors and moderate reaction on progesterone receptors. On the contrary, during diestrus the scores for the estrogen receptors decreased, while the progesterone receptors level increased - uterine cells expressed strong reaction for progesterone receptors, and moderate reaction for estrogen receptors. Uterine cells in cystic endometrial hyperplasia expressed a strong reaction for estrogen receptors, and moderate reaction for progesterone receptors, but on the other hand the uterine cells in the uterus with pyometra expressed a moderate to strong reaction for progesterone receptors, and a weak reaction for estrogen receptors. In further investigations it would be interesting to perform quantitative analysis for both estrogen and progesterone receptors during different phases of the estrus cycle and also in the uterus with cystic endometrial hyperplasia and pyometra.

Immunohistochemical evaluation of apoptosis and proliferation in the mucous membrane of selected uterine regions in pre-pubertal bitches exposed to low doses of zearalenone

Mycotoxins are toxic secondary metabolites produced by fungi. Those biologically active compounds occur naturally and they include zearalenone (ZEN), a mycotoxin that contaminates plant material, including the ingredients used in the production of commercial dog food. The influence of monotonic, low-dose and long-term exposure to ZEN on pre-pubertal bitches has not been fully explored to date. This paper describes a 42-day experiment performed on clinically healthy female dogs aged approximately 70 days, with estimated body weight of 8 kg. The animals were randomly divided into two experimental groups (EI and EII) and a control group (C) of 10 animals each. Group EI received 50 μg ZEN/kg (of body weight) per os, group EII received 75 μg ZEN/kg BW per os, and the control group was administered placebo. The bitches were ovariohysterectomized at the end of the experiment (at around 112 days of age), and selected sections of the uterine wall were subjected to immunohistochemical analyses (TUNEL and PCNA). A shift towards higher apoptotic (AI) and proliferative index (PI) was observed, in particular in group EI. Higher AI and PI values were noted in the epithelium of all uterine regions analysed and in the uterine glands in the uterine horn proximal to the body of the uterus.

The Effect of Low Monotonic Doses of Zearalenone on Selected Reproductive Tissues in Pre-Pubertal Female Dogs--A Review

The growing interest in toxic substances combined with advancements in biological sciences has shed a new light on the problem of mycotoxins contaminating feeds and foods. An interdisciplinary approach was developed by identifying dose-response relationships in key research concepts, including the low dose theory of estrogen-like compounds, hormesis, NOAEL dose, compensatory response and/or food tolerance, and effects of exposure to undesirable substances. The above considerations increased the researchers’ interest in risk evaluation, namely: (i) clinical symptoms associated with long-term, daily exposure to low doses of a toxic compound; and (ii) dysfunctions at cellular or tissue level that do not produce clinical symptoms. Research advancements facilitate the extrapolation of results and promote the use of novel tools for evaluating the risk of exposure, for example exposure to zearalenone in pre-pubertal female dogs. The arguments presented in this paper suggest that low doses of zearalenone in commercial feeds stimulate metabolic processes and increase weight gains. Those processes are accompanied by lower proliferation rates in the ovaries, neoangiogenesis and vasodilation in the ovaries and the uterus, changes in the steroid hormone profile, and changes in the activity of hydroxysteroid dehydrogenases. All of the above changes result from exogenous hyperestrogenizm.

An immunohistochemical study on the expression of sex steroid receptors, Ki-67 and cytokeratins 7 and 20 in feline endometrial adenocarcinomas

BACKGROUND

Endometrial adenocarcinomas are a rare type of tumour in cats. Though different morphologies have been reported, the most frequent histological type of feline endometrial adenocarcinoma (FEA) is the papillary serous. Characterization of molecular markers expression in FEA may contribute to clarify the pathogenesis of these tumours and to assess the differences between normal endometrium and FEA regarding the expression pattern of several proteins. Therefore, this study aimed to evaluate the immunohistochemical profile of a wide panel of antibodies (specific for ER-α, PR, Ki-67, CK7 and CK20) in twenty-four cases of FEA. Comparisons were made between FEA and feline normal cyclic endometrium in follicular (n = 13) and luteal (n = 10) stages. Except for Ki-67, all other molecular markers were assessed independently for the intensity of immunolabeling and for the percentage of cells expressing the protein.

RESULTS

This study showed that in FEA a loss of expression occurs for ER-α (P ≤ 0.0001) and less markedly also for PR. The lost in sex steroid receptors concerns a decrease in both the proportion of labelled cells and the intensity of immunolabelling (P = 0.002 and P = 0.024, respectively). Proliferative activity, estimated via Ki-67 immunoreaction, significantly increased in FEA as compared to normal endometrium (P ≤ 0.0001). Feline endometrial adenocarcinomas maintained the CK7+/CK20+ status of normal endometrium. However, FEA showed decreased CK7 intensity of labelling compared to normal endometria (P ≤ 0.0001) and loss of CK20 expression, both in intensity (P ≤ 0.0001) and in percentage of positive cells (P = 0.01), compared to normal tissues.

CONCLUSIONS

Data gathered in this study suggest that proliferation in FEA accompanies ER-α down-regulation, possibly following activation of pathways mediated by local growth factors. Moreover, FEA retains combined expression of CK7 and CK20, as evidenced in normal endometrial epithelia, although a decrease in CK7 expression was observed.

Oestrous cycle-dependent expression of Fas and Bcl2 family gene products in normal canine endometrium

During the oestrous cycle canine endometrium undergoes cyclical cellular proliferation, apoptosis and differentiation. To study the regulation of endometrial apoptosis and proliferation events the expression of apoptosis-related genes was analysed by real-time polymerase chain reaction and cellular expression of their proteins was identified through immunohistochemistry. Cellular apoptosis and proliferation events were detected by TdT-mediated dUTP-biotin nick end labeling (TUNEL) and proliferation marker Ki67 immunostaining, respectively. The highest proliferative index was observed in the follicular phase (all endometrial cellular components) and at early dioestrus (basal glands). This was associated with a low apoptotic index and a strong expression of anti- (Bcl2) and pro-apoptotic proteins (Fas, FasL, Bax). Subsequently (Days 11-45 of dioestrus), basal glandular epithelium experienced the highest apoptotic index, coincidental with a decrease of Bcl2 expression and a low ratio of Bcl2/Bax transcription. An increase in the apoptotic index of crypts, stromal and endothelial cells was observed at late dioestrus and the beginning of anoestrus. These results indicate that pro- and anti-apoptotic proteins regulate the balance between cell proliferation and death in the canine endometrium during the oestrous cycle. High Bcl2 expression in both the follicular and early dioestrous phases stimulate glandular proliferation and prevent apoptosis but, in the non-pregnant uterus, a decrease in Bcl2 expression together with an increase in pro-apoptotic proteins induces apoptosis of basal glandular epithelium cells.

The effect of low doses of zearalenone and its metabolites on progesterone and 17β-estradiol concentrations in peripheral blood and body weights of pre-pubertal female Beagle dogs

The experiment involved 30 clinically healthy female Beagle dogs aged approximately 70 days with estimated initial body weight (BW) of 8 kg. The animals were randomly divided into two experimental groups (EI and EII) and a control group of 10 animals each. Group EI was intoxicated with 50 μg zearalenone/kg BW per os for 42 days, group EII received 75 μg zearalenone/kg BW per os for 42 days, and the control group was administered placebo per os for 42 days. The animals were weighed, and blood samples for analyses of the concentrations of zearalenone, its metabolites, progesterone and 17β-estradiol were collected seven times at seven-day intervals, one hour after mycotoxin administration. Biotransformation of zearalenone was observed in all groups throughout the experiment, and the highest percentage share of α-zearalenol was reported in group EII on the last five sampling dates (0.637-0.788 ng/ml, i.e. percentage share of 57.96-73.64%). The above had a significant influence on the non-physiological concentrations of progesterone and 17β-estradiol in both experimental (E) groups throughout the experiment. The lowest progesterone levels (0.131 ng/ml) were observed in group EII during the last test, and high concentrations of 17β-estradiol were found in group EII on the last two sampling dates (17.434 and 21.581 ng/ml, respectively) in comparison with control. Inhibited proliferation, manifested by a slower rate of body weight gain, was observed on the last but one day of zearalenone administration in both experimental groups. Our results indicate that NOAEL doses have stimulating/adaptive effects, whereas doses above NOAEL values suggest that even very low zearalenone doses can act as endocrine disruptors with regard to progesterone and 17β-estradiol.

Remodeling of bovine endometrium throughout the estrous cycle

The mammalian endometrium changes morphologically and functionally throughout the estrous cycle. In some species, endometrial cells also undergo periodic proliferation and degeneration. However, the remodeling of bovine endometrium throughout the estrous cycle remains unclear. In the present study, we examined how the remodeling of bovine endometrium varied through the estrous cycle by measuring the relative rates of cell proliferation and apoptosis. Cells positive for both KI-67 (a proliferation marker) and cleaved caspase-3 (CCP3: an apoptotic cell marker) were immunohistochemically evaluated throughout the estrous cycle in the luminal and glandular epithelia, and the stroma of bovine endometrium. Percentages of KI-67-positive cells tended to be higher at the early luteal and follicular stages than at the mid and late luteal stages in all cell types. Similarly, percentages of CCP3-positive cells were higher at the early luteal stage than at the mid and late luteal stages in the luminal epithelium and stroma. Furthermore, CCP3 expression levels by Western blot analysis agreed with these immunohistological observations. On the other hand, DNA fragmentation was detected in the bovine endometrium without significant differences during the estrous cycle by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. Together, these results show that cell proliferation and apoptosis undergo cyclic patterns in the bovine endometrium, and suggest that the bovine endometrium is remodeled in each estrous cycle.

Characterization of foamy epithelial surface cells in the canine endometrium

In mature bitches, endometrial epithelial surface cells modify function and corresponding morphology during the oestrous cycle. During late metoestrous, endometrial epithelial surface cells frequently accumulate fat and thereby adopt a foamy morphology. This cyclic appearance of foamy endometrial epithelial cells (fEECs) seems to be physiological in the dog, whereas in other species, it indicates pathological changes. Function of these fEECs has not been identified until now. Therefore, the aim of the study was to characterize the fEECs by means of transmission electron microscopy and immunohistochemistry. Different manifestations of fEECs were observed and analysed with regard to proliferative activity and presence of different epithelial adhesion molecules including PLEKHA7, β-catenin and E-cadherin. PLEKHA7 was restricted to the apical regions of the fEECs, whereas E-cadherin and β-catenin were demonstrated basolateral. The immunohistochemical detection of steroid hormone receptors demonstrated the responsiveness of the fEECs to steroid hormones. Intense progesterone receptor expression was observed in the fEECs indicating a high responsiveness to this hormone. Considering a potential function of the fEECs, we hypothesized that leptin, a hormone produced by other lipid-accumulating cells and described to be involved in reproduction, in particular during implantation, might also originate from the fEECs which was confirmed by immunohistochemical methods. Moreover, leptin receptor was found in fEECs indicating the fEECs as both, source and target for leptin. Therefore, we conclude that fEECs in the canine uterus have a potential role in early pregnancy events and that the different observed manifestations might simply reflect the variations of signs of pseudopregnancy among bitches.

Effects of steroid hormones on differentiated glandular epithelial and stromal cells in a three dimensional cell culture model of the canine endometrium

Background

Oestrogens and progesterone have a significant impact on the endometrium during the canine oestrous cycle. Their receptors mediate plasma steroid hormone levels and are expressed in several endometrial cell types. Altered steroid receptor expression patterns are involved in serious uterine diseases; however the mechanisms of hormone action during pathogenesis in these tissues remain unclear. The development of 3D culture systems of canine endometrial cells provides an opportunity for the effects of steroid hormones to be quantitatively assessed in a more in vivo-like setting. The present study aimed to determine the effects of the steroid hormones 17β-estradiol (E) and progesterone (P) on the expression of the oestrogen and progesterone receptors (ER and PR), and on proliferative activity, in a 3D co-culture system of canine uterine origin, comprising differentiated endometrial glands, and stromal cells (SCs).

Results

Morphology, differentiation, and apical-basolateral polarity of cultured glandular epithelial cells (GECs) were comparable to those in native uterine tissue as assessed by immunohistochemistry using differentiation markers (β-catenin, laminin), lectin histochemistry, and transmission electron microscopy. Supplementation of our 3D-culture system with E (at 15, 30 and 100 pg/mL) resulted in constant levels of ER expression in GECs, but reduced expression levels in SCs. PR expression was reduced in both GECs and SCs following treatment with E. 3 ng/mL P resulted in increased ER expression in GECs, but a decrease in SCs. PR expression in GECs increased in all P-treated groups, whereas PRs in SCs decreased with the lowest and highest doses, but increased with the middle dose of treatment. Proliferative activity, assessed by Ki67 staining, remained below 1% in all assays and cell types.

Conclusions

The present study demonstrates the applicability of our 3D organotypic canine endometrium-derived culture system for cellular-level studies. 3D cultures represent near-physiological systems allowing reproducible quantitative experimentation, thus reducing the need to experiment on living animals. The results of the present investigation emphasize the importance of co-culture of the uterine glands with SCs, as it was shown that the responsiveness of the different cell types to steroid hormones were divergent in the 3D cell culture model.

The effect of experimental low zearalenone intoxication on ovarian follicles in pre-pubertal bitches

Companion animals, including bitches, may be exposed to zearalenone (ZEN) toxins that are often present in feed, and ZEN intoxication may lead to ovarian dysfunction. This study involved evaluation of the degree of ZEN-induced hypo stimulation of ovary by determination of proliferative and apoptotic indices and description of the ultra-structural organization of ovarian follicles in pre-pubertal bitches subjected to experimental, long-term exposure to low-dose ZEN mycotoxicosis. The experiment involved 30 clinically healthy, immature Beagle bitches aged approximately 70 days with initial average body weight of 8 kg, randomly divided into three groups of 10 animals each: two experimental groups (EI and EII) and a control group (C). Over a period of 42 days, ZEN was administered per os to EI animals at a dose of 50 μg/kg BW, and to EII bitches at a dose of 75 μg/kg BW. Control group animals were fed placebo containing no ZEN for 42 days. Analytical samples of the mycotoxin were administered daily in gelatin capsules before morning feeding. All the bitches were subjected to ovario-hysterectomy at the end of the experiment. Proliferation index (PCNA method) and apoptotic index (TUNEL test) values were determined by immune-histological analyses. The median for apoptotic index was determined at 13.45 for group EI, 17.84 for group EII, and 8.59 for group C. The median for proliferation index was determined at 35.25 for group EII, 42.44 for group EI, and 70.60 for group C. The results of ultra-structural examinations of the ovaries revealed that experimental, ZEN-induced hyperestrogenism enhanced apoptosis and lowered the proliferative ability of follicular cells what contributed to organelle destruction in pre-pubertal bitches. The changes observed were particularly advanced in EII animals, which were administered a higher dose of ZEN.

The morphological basis of proestrus endometrial bleeding in canines

Endometrial bleeding during proestrus is a well-known phenomenon in the bitch. However, the exact events on the cellular level have not been studied. In the present investigation, immunohistochemical methods and transmission electron microscopy were employed to obtain more information about this cyclic event in canines. Long, stretched blood vessels were seen in H&E stained sections during proestrus. These vessels showed mitotic activity, as evidenced by Ki67 immunostaining. Although the endothelial lining and basement membrane of endometrial blood vessels seemed continuous, as indicated by immunohistochemical staining for laminin and Von Willebrand factor, transmission electron microscopy showed an extreme thinning and even interruption of the vascular wall in endometrial venules. Platelets were frequently seen in those areas, and also detected by immunohistochemistry. Interestingly, all endometrial capillaries examined by electron microscopy had an intact wall. We therefore postulate the endometrial venules to be the blood vessels that are mainly responsible for proestrus endometrial bleeding, rather than subepithelial capillaries.

Reproductive cycles of the domestic bitch

Domestic dogs are monoestrous, typically non-seasonal, polytocous, spontaneous ovulators and have a spontaneous luteal phase slightly longer (by approx 5 day) than the 64±1day luteal phases of a 65±1day pregnancy, a phase followed by an obligate anestrus before the next 2-3 week "heat" (proestrus-estrus). The resulting inter-estrus intervals of 5-12 months are variable among bitches, commonly 6-7 months, and range from highly variable to regular (to perhaps within±5-10 day of sequential 7 month cycle, for instance) within bitches, and across studies and do not vary significantly between pregnant and non-pregnant cycles. Hormone levels reported are those observed in this laboratory using previously reported assays and canine gonadotropin standards unless stated otherwise. Endocrine sequences for dog cycles are not unlike those of many other mammals, including selection of ovulatory follicles by increased LH pulsatility, the occurrence of estrus behavior and LH surge during a decline in the estrogen: progestin ratio, a pronounced preovulatory luteinization as in humans and rodents, and luteotrophic roles for both LH and prolactin. Non-pregnant bitches have a spontaneously prolonged luteal phase, often longer and with a more protracted decline in serum progesterone than in pregnancy as there is no uterine luteolytic mechanism. The obligate anestrus of 8-40 weeks is terminated by poorly understood interactions of environment (e.g. pheromones, possibly photoperiod) and a potential endogenous circannual cycle in sensitivities of hypothalamic dopaminergic, serotonergic and/or opioid pathways.

Immunohistochemical searching for estrogen and progesterone receptors in women vocal fold epithelia

Larynx is extremely sensitive to endocrinologic changes. Most vocal fold mucosa alterations are caused by changes in vocal fold liquid content and its epithelial changes. Estrogen and progesterone interfere and change this liquid content in the vocal folds. Our goal with the present paper is to study the presence of estrogen and progesterone receptors on vocal fold epithelium in 19 vocal fold epithelium specimens that did not present any indication of disease, especially inflammatory disease. We discarded those cases of patients above 40 years of age and those below 15.

RESULTS

We found progesterone receptors in 18 of the 19 patients. The progesterone receptors are located both in the nucleus and the cytoplasm of cells, and mainly in the basal layer. There was no report of estrogen receptors present in the vocal folds.

CONCLUSION

Vocal fold epithelium bears progesterone receptors, in the cytoplasm and in the nucleus. We did not find estrogen receptors in the epithelia of the vocal folds investigated.

A three-dimensional culture model of canine uterine glands

The canine endometrium is frequently affected by severe alterations with unclear pathogenesis and is, therefore, an important subject of research in veterinary gynecology. Therefore, the aim of our study was to establish a three-dimensional in vitro system of the canine endometrium suitable for experimental approaches. For this reason, intact uterine glands were isolated from canine uteri and placed together with stromal cells on culture dishes coated with several extracellular matrix components (collagen I, IV, fibronectin, laminin, gelatin, Matrigel) for up to 4 d to support differentiation of cultured cells. Immunohistochemical detection of laminin on freshly isolated glands showed a partial preservation of the basement membrane--an important factor for epithelial differentiation. Glandular structures were differentiated and polarized during culture time as shown by electron microscopy. Signs of degeneration and loss of cell-cell adhesions as seen occasionally on day 4 depended on the individual dog. In general, morphology was best preserved on Matrigel matrix. No significant changes of cultured glandular explants were observed concerning proliferation and steroid receptor (estrogen, progesterone) expression when compared with the original uterine tissue as assessed by immunohistochemical staining. Lectin histochemistry revealed comparable results for the in vivo endometrial glands and the cultured glandular explants during the whole culture period. This in vitro reconstitution of the canine endometrium is a promising tool to study the cyclic events in the normal endometrium as well as alterations in the affected uterus.

Relationship between uterine morphology and peripheral concentrations of sex steroid hormone in wild Japanese black bears (Ursus thibetanus japonicus)

Developing a better understanding of the reproductive physiology and breeding condition peculiar to wild Japanese black bears (Ursus thibetanus japonicus) is crucial for estimation of their habitat distribution. The aim of this study was to clarify the changes in morphology of the genital organs, cellular proliferation in the endometrium and sex steroid hormone concentrations along with the reproductive cycle in Japanese black bears. Samples were collected from a total of 24 female Japanese black bears (1-15 presumptive years old) that were caught in the wild in Iwate prefecture during the period between August 1999 and September 2005. Twenty-two out of the 24 animals were hunted from May to October. The ovaries from the 24 animals and the uteri from 23 animals were observed macroscopically and histologically to examine the relationship between morphology of the genital organs and the month of the year the animal was caught. The staining pattern of proliferating cell nuclear antigen (PCNA) in the endometrium was characterised. Peripheral concentrations of oestradiol-17beta and progesterone were determined by radioimmunoassay. All the animals that had a corpus luteum (n=12) were captured from August to October. The thickness of the endometrium in the animals captured from August to October (n=16) was significantly greater than those in animals captured from May to July (n=5) (P<0.05). From August to October, the thickness of the endometrium and the ratio of the area of the uterine glands to the area of the endometrium in the animals with a corpus luteum (n=12) were significantly greater than those without a corpus luteum (n=4) (P<0.01). Positive PCNA staining was only observed in the uteri of two animals captured in May. There was a significantly positive correlation between plasma progesterone concentrations and the thickness of the endometrium (rho=0.589, P<0.05). There were also significantly positive correlations between the progesterone to oestradiol-17beta ratio (P4/E2 ratio) and the thickness of the endometrium (rho=0.710, P<0.05), and between the P4/E2 ratio and the ratio of the uterine gland area in the endometrium (rho=0.626, P<0.01). These data suggest that the corpus luteum is formed during or just after the breeding season and that the cells in the endometrium and the uterine glands, which proliferate in the early breeding season, grow and develop under the influence of progesterone and oestradiol-17beta during the period of delayed implantation in Japanese black bears.

Estrous cycle-dependent histology and review of sex steroid receptor expression in dog reproductive tissues and mammary gland and associated hormone levels

This report describes normal histology of tissues from immature female dogs and sequential microscopic changes that occur during different stages of the estrous cycle in ovary, uterus, vagina and mammary glands. These observations are associated with a literature review of concurrent estrous cycle plasma hormone levels and expression of sex steroid receptors in these tissues. The combined review of different aspects of the estrous cycle in the dog provides readers with a comprehensive presentation and may guide investigators that are involved in testing compounds with hormonal effects in female dogs.