Canine Uterus Research Articles

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

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. 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. 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. 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.

Investigation Of Muc1 and Muc16 Expressions in Uterus Tissue of Kangal or Kangal Cross-Bred Bitches in Proestrus, Metestrus-Diestrus and Anestrus Periods of Sexual Cycles

Mucins are glycoprotein molecules found in mucus secretion. They have important functions in the reproductive system such as sperm motility, elimination of bacterial damage and facilitating implantation. In this study, MUC1 and MUC16 expressions in uterine tissues of Kangal or Kangal cross-bred bitchs in proestrus, metoestrus-dioestrus and anoestrus sexual periods were investigated by immunohistochemical method. Uterine tissues of 15 healthy and adopted Kangal or Kangal cross-bred bitches aged 3-6 years were used in the study. The biches were divided into 3 groups according to sexual cycle periods as proestrus (n=5), metaestrus-dioestrus (n=3) and anaestrus (n=7). As a result, MUC1 was found to be expressed in both cornu and corpus uteri epithelial cells, crypt epithelial cells, uterine gland cells, stratum vascularis, myometrium and perimetrium layers in canine uterus. When oestrus cycles were compared, it was found that expression increased more in the metoestrus-dioestrus phase compared to other phases. Expression of MUC16 was observed in the cornu uteri during the metoestrus-dioestrus phase. In this study, MUC1 and MUC16 were determined to be expressed in the uterine tissue of bitches and their release was found to be affected by hormones.

Immunofluorescence Analysis of Estrogen and Progesterone Receptors and Ki-67 Nuclear Protein in Canine Uteri Treated with Medroxyprogesterone Acetate During Anestrus

Immunofluorescence Analysis of Estrogen and Progesterone Receptors and Ki-67 Nuclear Protein in Canine Uteri Treated with Medroxyprogesterone Acetate During Anestrus

Anatomic characteristics and novel transplantation model of the canine uterus.

In Vietnam, the rate of absolute uterine factor infertility is increasing, but no study has been published on uterine transplantation. The present study was designed to comprehensively observe the canine uterine anatomy and to examine the possibility of using a living canine donor for uterine transplantation training and further research. Ten female Vietnamese mixed-breed dogs were sacrificed for anatomical research, and 15 additional pairs were used to evaluate the novel uterine transplant model. The anatomic features of the canine uterus differed considerably from those of the human uterus, with the uterine vessels originating from branches of the pudendal vessels (also known as the vaginal vessels). The uterine vascular pedicle had a small diameter (1 to 1.5 mm for arteries and 1.2 to 2.0 mm for veins) and required manipulation under a microscope. To perform uterine transplantation, the donor specimen's artery and vein lengths were successfully reconstructed by anastomosis between both sides of the vasculature using autologous Y-shaped subcutaneous veins. The living-donor uterine transplantation model constructed in this study was feasible, with the transplanted uterus surviving in 86.7% of cases (13/15). Uterine transplantation was successfully performed in a Vietnamese canine living donor model. This model could be helpful in uterine transplantation training and improve the transplantation success rate in humans.

Expression of prostaglandin F2 alpha receptors (PTGFR) and C-reactive protein (CRP) in the canine uterus and cervix with opened- and closed-cervix pyometra

Expression of prostaglandin F2 alpha receptors (PTGFR) and C-reactive protein (CRP) in the canine uterus and cervix with opened- and closed-cervix pyometra

Differential Expression of Prostaglandin Receptors in Canine Uterus With Pyometra

The objective of the study was to ascertain the role of prostaglandins Viz., PGE2 and PGF2α, and their respective receptors in the pathophysiology of canine pyometra. Normal (n = 6) and pyometra (n = 8) affected uterus were collected from bitches undergoing ovariohysterectomy. Pyometra was graded according to histopathological alterations. The levels of PGE2 and PGF2α were estimated in the endometrium. The differential expression in the mRNA of PGF2α receptor (FP) and PGE2 receptors (EP1, EP2, EP3, and EP4) were studied in the endometrium and myometrium of the pyometra-affected uterus. Normal uterus served as calibrator. Elevation of both PGE2 and PGF2α levels in the endometrium of pyometra-affected bitches was observed. The FP receptor gene in the endometrium and myometrium of pyometra-affected bitches was downregulated (P < .05). Out of all EP receptors, only EP2 receptor has shown upregulation in both endometrium and myometrium of pyometra affected uterus. EP3 receptor got downregulated in both endometrium and myometrium in pyometra. Thus, downregulation of FP, EP3 receptors in the myometrium reinforces the lack of contractility in pyometra-affected bitches favoring bacterial proliferation and subsequent pus accumulation. Moreover, upregulation of EP2 receptors in the pyometra bitches suggests the scope of selective pharmacological inhibition of EP2 receptors as an adjunct therapy in the treatment of pyometra.

Histomorphometry and uterine proteomics during the normal reproductive cycle in bitches

We aimed to evaluate the histomorphometry and proteomic profile of the canine uterus during all stages of the reproductive cycle. Eighteen healthy female dogs had their estrous cycle identified by clinical evaluation, vaginal cytology, and serum progesterone levels, which were allocated to the proestrus (n=5), estrus (n=5), diestrus (n=5), and anestrus (n=3) groups. All were submitted to elective ovariosalpingohysterectomy, and the uteri were collected for histomorphometric measurement (Image J software). For proteomic analysis, fragments of the uterine horns were subjected to protein measurement (Bradford method) and extraction by 2D electrophoresis (PDquest software). The results showed that the diestrus promoted greater values of thickness in the uterine structures (μm): uterine wall (2,223.8±229.8), endometrium (819.7±109.1), and myometrium (1,392.6±294.2). Uterus showed a protein profile with good reproducibility per phase (pI: 3.5–9.0; PM: 24–150 KDa), with 11 spots in all phases. Despite the greatest histomorphometric changes in the diestrus, we observed a greater number of spots in the estrus (253±45), followed by the proestrus (185±21), diestrus (113±39), and anestrus (80±21). This finding showed probable participation of these proteins in the uterine preparation for receiving gametes for fertilization. Our results showed greater uterine thickness in the diestrus, and greater protein secretion in the estrus, contributing to the prospection of identification of proteins responsible for the biological reproduction processes.

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® , 10mg/kg) was injected subcutaneously 5days 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.

Comparative Proteomic Profile of Canine Uterus with Pyometra

Comparative Proteomic Profile of Canine Uterus with Pyometra

Canine conceptus-maternal communication during maintenance and termination of pregnancy, including the role of species-specific decidualization

Among domestic animal species, the reproductive biology of the dog belongs to the most peculiar. This includes the conceptus-maternal communication and endocrine mechanisms involved in maintenance of pregnancy. Dogs fully depend on luteal progesterone (P4) throughout pregnancy, with similar steroid secretion patterns in pregnant and non-pregnant bitches until prepartum luteolysis. Thus, dogs lack the classical recognition of pregnancy. The luteal P4 is the most important hormone regulating the onset and maintenance of pregnancy in previously estrogenized bitches. Although the canine uterus is exposed to high P4 levels, decidualization is not spontaneous but induced by the presence of embryos. Following implantation, decidualization continues, associated with development of the invasive endotheliochorial placenta, leading to establishment of maternal decidual cells expressing the nuclear P4 receptor (PGR). Consequently, although not producing steroids, the canine placenta remains highly sensitive to circulating ovarian steroids. The placental conceptus-maternal communication is responsible for the maintenance of pregnancy, with functional withdrawal of PGR evoking a luteolytic cascade with prepartum PGF2α release. The fetal trophoblast is the major source of prepartum placental prostaglandins. This conceptus-maternal communication is unique to the dog and has clinical implications. Due to luteal steroids, there is no prepartum estradiol increase. Elevated cortisol levels are observed irregularly. This emphasizes the unique character of canine reproductive physiology and the challenges in transferring translational research to the dog. Further research is needed for better understanding of canine reproduction and improving clinical protocols, including the latest results obtained from applying modern laboratory technologies such as the transcriptomic approach.

Bacteriological findings in the canine uterus during Caesarean section performed due to dystocia and their correlation to puppy mortality at the time of parturition.

Canine intrauterine bacteriological flora during dystocia is unknown. Thus, frequency (bacterial growth (not) detected), quality (species and number of different bacterial isolates) and quantity (colony-forming units) of intrauterine bacteria in relation to in utero foetal death in 50 bitches undergoing emergency Caesarean section were investigated. Bacterial growth was quantified from single colonies, (+) (0.5), to strong growth, +++ (3) and was observed in 34 bitches (68%), with Staph.epidermidis (n=12), Staph. intermedius-group (n=7), β-haemolytic streptococci (n=6), Staph. aureus, α- and γ-haemolytic streptococci (n=4 each) being most common and one to four bacteria per sample. Regarding the quantity, most often (n=46) low growth was identified. In bitches with living pups only (group I), mean number of isolates was 0.78±0.83 compared to 1.60±1.10 (living + stillborn pups, group II) and 1.0±1.15 (stillborn pups only, group III) and mean bacterial growth in groups I/II/III was + (1.0, quantity), + (1.4) and ++ (1.6). Taking just positive samples into consideration, mean number of bacterial isolates was significantly higher in group II compared to I (p=.0088). We concluded that the canine uterus cannot be considered free of bacteria during dystocia. Mean numbers of different bacterial isolates and quantity of bacterial growth are higher in bitches with in utero foetal death.

Functional implications of the utero-placental relaxin (RLN) system in the dog throughout pregnancy and at term.

Relaxin (RLN) is a key hormone of pregnancy in mammals best known for its involvement in connective tissue remodeling. In the domestic dog, placental RLN is the only known endocrine marker of pregnancy. However, knowledge is sparse regarding the spatio-temporal expression of RLN and its receptors (RXFP1 and RXFP2) in the canine uterus and placenta. Here, their expression was investigated in the pre-implantation uterus and utero-placental compartments (UtPl) at selected time points during gestation: post-implantation, mid-gestation, and at normal and antigestagen-induced luteolysis/abortion. Immunohistochemistry with newly generated, canine-specific antisera, in situ hybridization and semi-quantitative PCR were applied. In compartmentalization studies, placental and endometrial RLN increased continuously toward prepartum. The placental RXFP1 was time-related and highest during post-implantation and decreased together with RXFP2 at prepartum luteolysis. The endometrial levels of both receptors did not vary greatly, but myometrial RXFP2 decreased from mid-gestation to prepartum luteolysis. Antigestagen treatment resulted in suppression of RLN in UtPl and decreased RXFP1 and RXFP2 in the uterus. The placental RLN was localized mainly in the cytotrophoblast. Additionally, RXFP1 stained strongly in placental endothelial cells while RXFP2 was found mainly in maternal decidual cells. Uterine staining for all targets was found in epithelial cellular constituents and in myometrium. Finally, besides its endocrine functions, RLN seems to be involved in auto-/paracrine regulation of utero-placental functions in dogs in a time-dependent manner. New insights into feto-maternal communication was provided, in particular regarding the localization of RXFP2 in the maternal decidual cells, implying functional roles of RLN during the decidualization process.

Histomorphometrics and quantitative unbiased stereology in canine uteri treated with medroxyprogesterone acetate

This article describes the effects of MPA use on the canine uterus using stereological methods. Entire reproductive tracts were removed from normal healthy canine bitches (Canis lupus familiaris) and grouped as: nulliparous (n = 11), multiparous (n = 11) and MPA-treated (n = 11; nulliparous; two treatments; 5 mg/kg). 1 cm samples were cut from the corpus, horn and uterine tube and fixed in 10% formaldehyde. Sections of each were mounted on slides and stained with hematoxylin-eosin. We assessed the fraction area for components of endometrium and myometrium and VV (volume density) and SV (surface density) of the gland and stroma using the M36 test system provided by the STEPanizer Stereological Tool. No gross histological differences were observed between study groups in the uterine tube, uterine corpus and horn. The wall of the uterine corpus and horn in MPA-treated bitches was characterized as being thicker than in the other groups. A cross-section of the uterine corpus revealed no differences between components of uterine wall in the corpus and horn; however, differences were observed in the volume density [VV; %] in variables such as: VV[str.vasc/uterus] (nulliparous vs. multiparous; p = 0.0019) and VV[str.supravasc/uterus] (multiparous vs. nulliparous and MPA; p = 0.0035). In the endometrial gland, differences were detected in SV[gland/endom] (multiparous vs. MPA, p = 0.0442). In the uterine horn, differences were only observed in the variable VV[lumen.gland/endom] (multiparous vs. MPA; p = 0.0019). This study shows quantitative changes in the architecture of the endometrium and myometrium in all the uterine segments, mainly morphological endometrial gland changes of the uterine corpus, increasing the surface area per unit of volume; however, these changes usually do not differ quantitatively from those observed in the uterus of multiparous bitches.

Quantitative Analysis of Collagen Fibrillar Structure in Canine Uterus Exposed to Acetate of Medroxyprogesterone Using Second Harmonic Generation Microscopy

Quantitative Analysis of Collagen Fibrillar Structure in Canine Uterus Exposed to Acetate of Medroxyprogesterone Using Second Harmonic Generation Microscopy

Oxytocin receptors in dioestrous and anoestrous canine uteri.

The aim of the study was to localize oxytocin receptors (OTR) and measure mRNA expression of OTR in the canine uterus with and without the influence of progesterone. Uterine samples were taken from nine anoestrous and eight dioestrous bitches during ovariohysterectomy. Histological changes were evaluated in haematoxylin and eosin (HE)-stained samples. Purified polyclonal antibody for OTR was used in immunohistochemistry to localize receptors in uterine layers. Relative mRNA concentration of OTR was evaluated with real-time PCR from full-thickness uterine samples taken from the middle horn and the body. Myometrial smooth muscle cells, endometrial luminal epithelium (LE) and deep and superficial glandular epithelium were positively stained for oxytocin receptors in non-pregnant animals. No significant difference in staining intensity was detected between uterine middle horn and body. However, the staining intensity of LE was significantly higher in dioestrous than in anoestrous uteri (p<.05). Leucocytes and endothelium of blood vessels were also positively stained for OTR. Real-time PCR showed no significant differences in OTR mRNA expression between the middle horn and the body of the uterus, or between anoestrous and dioestrous uterus. No correlation was noted between OTR mRNA expression and blood progesterone concentration. In conclusion, despite the apparent inactivity, the uterus of the non-pregnant bitch expresses OTR. The distribution or relative expression of OTR does not differ between uterine horn and body in dioestrus or anoestrus except in LE. LE may have more oxytocin-dependent activity during dioestrus than anoestrus.

Quantification of collagen fibers in canine uteri treated with medroxyprogesterone acetate

Collagen plays essential roles in remodeling uterine tissue during decidualization, implantation, pregnancy and involution. To understand whether the progestational agent medroxyprogesterone acetate (MPA) can modify the organization and deposit of collagen in the uteri of normal bitches (Canis Tlupus familiaris), we assessed uterine tissues by histochemistry. Uteri were grouped as: nulliparous (n=11), multiparous (n=11) and treated with MPA (n=11; nulliparous with two treatments; 5mg/kg; i.m.). The amount, location and birefringence of interstitial collagen types I and III in the fold and base of the endometrial stroma and the myometrial muscular layers were studied on sections stained with Picrosirius Red by polarized light microscopy and evaluated by ANOVA. No differences were observed in the endometrium. In the myometrium, differences were observed in collagen type I between MPA-treated and nulliparous uteri vs. multiparous (p<0.05), and differences in collagen type III between nulliparous and multiparous uteri vs. MPA-treated (p=0.0001). In conclusion, two doses of MPA had no significant effect on the investigated collagens in the extracellular matrix.

Decidualization of the canine uterus: From early until late gestational in vivo morphological observations, and functional characterization of immortalized canine uterine stromal cell lines.

The apparent lack of classical mechanisms for maternal recognition of pregnancy is one of the most intriguing features of canine reproduction. Consequently, similar levels of circulating luteal steroids are observed in pregnant and non-pregnant dogs. However, the early pre-implantation canine embryo locally modulates uterine responses to its presence, facilitating the successful onset of pregnancy. As a part of this interaction, the canine uterus undergoes a species-specific decidualization. Maternal stroma-derived decidual cells develop, the only cells of the canine placenta expressing progesterone receptor (PGR). There exists an acute need for an in vitro stable cell line model for canine decidualization. Therefore, herein our goal was to establish, immortalize and characterize such a cell line. We immortalized three monolayer dog uterine stromal (DUS) cell lines by stably transfecting them with SV40Tag oncogene. Cells retained their mesenchymal character for over 30 passages, as evidenced by VIMENTIN staining. Genomic incorporation of the SV40Tag protein was confirmed by immunofluorescence and Western blot analyses. Cells submitted to a classical in vitro decidualization protocol (N6,2'-O-dibutyryladenosine-3',5'-cyclic monophosphate) revealed upregulated gene levels of selected major decidualization markers (e.g. PRLR, PGR, IGF1, PTGES). Additionally, the basic decidualization capability of PGE2 was demonstrated, revealing increased levels of, for example, PGR and PRLR gene expression, thereby implying its involvement in the progesterone-dependent decidualization in the canine uterus. In summary, our in vitro model with immortalized DUS cell line could serve as an ideal and unique model to study the underlying molecular and endocrine mechanisms of canine decidualization.

Kisspeptin-10 and the G protein-coupled receptor 54 are differentially expressed in the canine pregnant uterus and trophoblast cells.

Uterine tissue was collected from bitches after ovariohysterectomy at different times after ovulation. Samples were assigned to four groups: metestrous non-pregnant, day 10-12, n=4; pre-implantation, day 10-12, n=9; post-implantation, day 18-25, n=13; mid-gestation, day 30-40, n=7. RT-qPCR detection was performed for kiss1 and the G protein-coupled receptor 54 (GPR54, specific receptor for kisspeptin). In addition, immunohistochemistry was performed for detection of kisspeptin-10 (KP-10), GPR54, as well as pan-cytokeratin and vimentin. The latter two were included to differentiate the different placental cell types. The percentage of positive stained cells was evaluated, and an immunoreactivity score (IRS) was obtained by multiplying the labelling intensity score (0-3) with the percentage of immunolabelled cells (range: 0-300). In non-pregnant and pre-implantation tissues, gene expression was highly variable for kiss1 and GPR54. Expression of GPR54 was higher before embryo adhesion than during post-implantation and mid-gestation (p<.05), whereas there was no difference found between groups for kiss1. Except during the pre-implantation period, KP-10 expression was higher in the non-pregnant uterus compared to all gestational periods investigated, indicating a pregnancy-related downregulation. In the pre-implantation period, KP-10 was present in larger vessels only, whereas the presence of GPR54 in vessels was found in all samples, with most labelling in the post-implantation period. KP-10 was present in superficial uterine glands, GPR54 in superficial and deep uterine glands of the post-implantation uterus. In myocytes, the highest staining for KP-10 was seen in the non-pregnant uterus, whereas the highest staining for GPR54 was seen in post-implantation and mid-gestation. Syncytiotrophoblast cells stained for both KP-10 and GPR54 in post-implantation and mid-gestation, with maximum intensity for GPR54 in the latter. We conclude that KP-10 and GPR54 are expressed in the canine uterus and trophoblast cells. However, during pregnancy, expression of both proteins seems to be differentially regulated.

Distribution of superoxide dismutase 1 and glutathione peroxidase 1 in the cyclic canine endometrium

Superoxide dismutase (SOD) and glutathione peroxidase (GPx) are two important antioxidant enzymes involved in tissue homeostasis by protecting cells and tissues from an accumulation of reactive oxygen species. Information concerning antioxidant enzymes in the canine uterus is almost inexistent. This work intends to establish the pattern of distribution of SOD1 and GPx1 immunoreaction in canine endometrium throughout the estrous cycle, using 46 endometrium samples of healthy dogs representing different cycle stages (anestrus-10, proestrus-10, estrus-10, early diestrus-7, and diestrus-9). SOD1 distribution in canine endometrium showed cyclic variations (P ≤ 0.001), with higher immunoscores in the progesterone-associated stages. Changing immunoreaction also concerned the different epithelial structures considered (surface epithelium, superficial glandular epithelium, and deep glandular epithelium) (P ≤ 0.001), but it was always higher than in the stroma (P ≤ 0.001). Deep glandular epithelial cells usually showed higher scores of immunoreaction compared with the other epithelial cells. Interestingly, in epithelial cells, distinct subcellular patterns for SOD1 were seen: the nuclear labeling was observed in estrus and early diestrus (P ≤ 0.001), whereas an apical reinforcement was observed in estrus (P = 0.011) in the glandular epithelia but not in the surface epithelia. In general, GPx1 distribution in canine endometrium remained relatively unchanged throughout the estrous cycle (P = 0.169) despite the slight decrease observed from proestrus to early diestrus. The highest scores were found in anestrus and diestrus (P < 0.05), varying with of the structure considered. An apical reinforcement pattern was also found for this molecule, which peaked in proestrus and estrus (P < 0.005). In summary, the present study showed that SOD1 and GPx1 are consistently distributed in the canine endometrium. The cyclic changes registered for both molecules suggest that they may play important roles in endometrial physiology, probably in apoptosis and proliferation.

The physiological expression of scavenger receptor SR-B1 in canine endometrial and placental epithelial cells and its potential involvement in pathogenesis of pyometra

Pyometra, the purulent inflammation of the uterus, is a common uterine disease of bitches that has potentially life-threatening consequences. The opportunistic bacterial infection of the uterus often progresses into the serious systemic inflammatory response syndrome. In a previous study, we characterized epithelial foam cells in the canine endometrial surface occurring in metestrus, and we regularly observed pronounced epithelial foam-cell formations in pyometra-affected uteri. Therefore, it was assumed that the mechanism behind lipid droplet accumulation in surface epithelial cells might even increase bacterial binding capacity and promote pyometra development. Lipid droplet accumulation in epithelial cells is accomplished via specialized lipid receptors called scavenger receptors (SR). Scavenger receptor class B type 1 (SR-B1) is an important receptor for lipid accumulation in diverse cell types, but it is also a strong binding partner for bacteria, and thereby enhances bacterial adhesion and clinical signs of systemic inflammatory response syndrome. In the present study, after the isolation of metestrous surface epithelial cells from canine uteri by laser capture microdissection, SR-B1 was identified at the messenger RNA (mRNA) level by quantitative real time polymerase chain reaction and also at the protein level by means of immunohistochemistry. In pyometra-affected uteri, SR-B1 mRNA expression was higher than that in the healthy control samples, and SR-B1 protein was expressed in the surface and crypt epithelial cells. Furthermore, to understand the physiological role of SR-B1 expression in the metestrus surface epithelial cells, we investigated its expression in the epithelial cells of the glandular chambers of canine placenta in different stages of gestation because these cells are also characterized by lipid droplet accumulation. SR-B1 was present in the placental epithelial cells of the glandular chambers from 25 to 30 and 45 to 50 days of gestation, where basal and basal and/or apical expression patterns were observed. The physiological expression of SR-B1 in metestrous endometrial surface epithelia might be related to the implantation process and embryo development, as SR-B1 was also identified in the epithelial cells of the canine placental chambers. The increased levels of SR-B1 in pyometra-affected uteri indicate a potential role for this scavenger receptor in endometrial bacterial adhesion.