The Role of Peroxisome Proliferator-Activated Receptors in PGF2α-Induced Luteolysis in the Bovine Corpus Luteum.

The participation of peroxisome proliferator-activated receptors (PPARs) in ovarian function in cattle is still not fully understood. The aim of this in vitro study was to determine: (i) the immunolocalization, mRNA expression and tissue concentration of PPARα, PPARδ and PPARγ in the bovine corpus luteum (CL) (n = 40) throughout the estrous cycle, and (ii) the involvement of PPAR in PGF2α-induced processes related to luteolysis. CL (n = 9) explants were cultured in the presence of PPAR antagonists (10-5 M) in combination with or without PGF2α receptor antagonist (10-5 M) and PGF2α (10-6 M). The mRNA and protein expression of PPARs was evaluated through qPCR, IHC, and ELISA, respectively. The results showed that PPAR mRNA and protein expression differed according to the luteal stages. PGF2α upregulated PPARδ and PPARγ mRNA expression in the bovine CL in vitro, whereas PPARγ increased the inhibitory effect of PGF2α by decreasing progesterone secretion and the mRNA expression of hydroxy-delta-5-steroid dehydrogenase, 3 ß- and steroid delta-isomerase 1 (HSD3B1) in the CL explants; mRNA transcription of tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) was increased. The obtained results indicate that the mRNA and protein expression of PPARs changes in the bovine CL throughout the estrous cycle and under the influence of PGF2α. We suggest that isoform γ, among all examined PPARs, could be a factor involved in the regulation of PGF2α-induced processes related to luteolysis in the bovine CL. Further studies are needed to understand the role of PPAR in luteal regression in the CL of cattle.

Peroxisome proliferator-activated receptor expression in the canine endometrium with cystic endometrial hyperplasia-pyometra complex.

The most common uterine diseases in bitches occurring during diestrus are cystic endometrial hyperplasia (CEH) and pyometra. These diseases can coexist as CEH-pyometra complex (CEH-P). Their pathogenesis has not been fully explained. Peroxisome proliferator-activated receptors (PPARs) are important factors regulating mammalian reproductive function and inflammatory processes. Although there is a lack of data concerning the expression of PPARs in the canine endometrium during CEH and CEH-P, we hypothesized that they might be involved in the development of pathological disorders of the canine endometrium. Therefore, the current study was conducted to evaluate and compare PPARα, PPARδ and PPARγ mRNA expression using quantitative real-time PCR (qPCR) and their immunolocalization using immunohistochemistry (IHC) staining in the endometrium of clinically healthy bitches (control group; n = 8) and those with CEH (n = 8) or CEH-P (n = 8). For quantification, the arithmetic means of all intensities of immunostaining from the cells were measured with the optical density. PPARα, PPARδ and PPARγ were detected in the luminal epithelium, glandular epithelium and stromal cells. The mRNA transcription of PPARα was higher in the CEH group than in the control group (p < .05). Additionally, the mRNA expression and immunostaining intensities of PPARδ and PPARγ in the endometrium in the CEH-P group were downregulated relative to those in the control group (p < .05). Moreover, the serum progesterone concentration measured by direct radioimmunoassay was decreased in the CEH-P group compared to the control group (p < .001) and CEH group (p < .05). The obtained results indicate that PPARs are present in the canine endometrium and that their mRNA profile and intensity levels change under pathological conditions such as CEH and CEH-P. This finding may suggest a correlation between changes in the PPAR expression profile and hormonal disturbances, as well as the potential involvement of PPARs in signal transduction during inflammatory processes occurring in the endometrium during CEH-P. These results pave the way to further research into the role of PPARs in the pathogenesis of CEH and CEH-P in female dogs.

Expression of pluripotency markers in the bovine uterus with adenomyosis.

BACKGROUND: Adenomyosis is a proliferative uterine dysfunction with unknown aetiology. One possible mechanism of its development involves disturbances in stem cell differentiation in uterine tissue. Previously, we identified pluripotent/multipotent cells in the bovine uterus, therefore our present study focused on determining expression of pluripotency markers, NANOG, OCT4 and SOX2, in bovine adenomyotic tissues and cells. FINDINGS: Immunolocalisation revealed protein expression of NANOG, OCT4 and SOX2 in both normal and adenomyotic uteri. mRNA expression for NANOG and OCT4 was increased in tissues obtained from uteri with adenomyosis compared to controls, but at the protein level there were no significant differences. mRNA expression for all three pluripotency markers was higher in myometrial cells isolated from uteri with adenomyotic lesions than in those isolated from normal uteri. The protein level of NANOG and SOX2 was decreased in stromal cells from adenomyotic tissues, whereas the level of OCT4 and SOX2 was increased in myometrial cells obtained from dysfunctional uteri. CONCLUSIONS: The results indicate significant changes in expression of pluripotency markers in adenomyotic compared to normal uteri, which suggest the involvement of uterine stem cells in adenomyosis.

Adenomyosis in the bovine uterus: correlation between frequency, age, and 17ß-estradiol-progesterone equilibrium.

Adenomyosis of the uterus is characterized by the presence of islands of endometrial glands and stroma within the myometrium. Etiopathology of adenomyosis has not been clearly defined but it potentially interferes reproductive processes in cattle. The aim of this initial study was to evaluate the impact of age on the frequency of adenomyosis in cows. Endometrial tissues collected from cows slaughtered between Day 8 and 12 of the estrous cycle (N = 72) were divided into two age groups: (1) 2 to 4 years old (N = 36) and (2) 5 years old and older (N = 36). The tissues were stained with hematoxylin and eosin. The adenomyosis histopathomorphologic stage was classified on a four-point scale according to the penetration of endometrial structures inside the perimetrium. The protein expression of the 17-ß estradiol (E2) and progesterone (P4) receptors were evaluated in the endometrial tissue samples by immunohistochemistry and Western blot analysis, and E2 and P4 concentrations were measured in the peripheral blood and uterine tissue. Adenomyosis was observed in 38 of the cows examined including 13 of the 2- to 4-year-old cows and 25 of the cows 5 years old or older. The frequency and intensity of adenomyosis increased with age. Higher E2 receptor protein expression was observed in adenomyotic cows and increased with disease development and increase of number of glands inside the uterus in the direction of perimetrium, and P4 receptor protein expression were unchanged in healthy and adenomyotic cows. An increase in the expression of E2 receptors and high, supraphysiological levels of E2 was detected in cows with III and IV degree of adenomyosis (P < 0.05). Overexpression of E2 receptor and alternations in E2 secretion might make the bovine uterus susceptible to a growth advantage of adenomyotic tissue over the surrounding myometrium. The pathogenesis and immunoendocrine mechanisms controlling adenomyosis in cattle warrant further study.