Immune cell populations in the equine corpus luteum throughout the oestrous cycle and early pregnancy: an immunohistochemical and flow cytometric study

Precise pharmacological control of the corpus luteum is important in the manipulation of the oestrous cycle in mares. Angiogenesis plays a key role in the growth and regression of the corpus luteum; therefore, influencing the vasculature of the corpus luteum may offer a novel method for controlling its lifespan. In the present study, changes in angiogenesis and vascular expression of endothelial growth factor (VEGF) were evaluated throughout the luteal phase and after PGF 2␣ -induced luteolysis. Corpora lutea were collected from mares in the early luteal phase (days 3-4), mid-luteal phase (day 10), early regression (day 14), late regression (day 17), and at 12 and 36 h after administration of PGF 2␣ on day 10 of the oestrous cycle. Immunohistochemistry was used to localize Von Willebrand factor and Ki67 in endothelial and proliferating cells, respectively. VEGF mRNA and protein were localized by in situ hybridization and immunohistochemistry. The proliferation index of endothelial cells was intense in the early luteal phase. The early and mid-luteal phases were characterized by a dense network of capillaries. The microvasculature started to regress by day 14. After administration of PGF 2␣ , vasodilation was observed after 12 h, but after 36 h, luteal degeneration was accompanied by a significant decrease in vascularity. VEGF mRNA and protein were expressed mainly in the luteal cells during the early and mid-luteal phases and expression declined at early regression (day 14). However, immunostaining for VEGF protein was high in late luteal regression (day 17) and 36 h after PGF 2␣ administration. These findings indicate a close temporal association between VEGF expression and angiogenesis in the equine corpus luteum during its functional lifespan.

Section: Discussionsupporting

confidence: 92%

Section: Animals and Tissue Collectionmentioning

confidence: 99%

Angiogenesis and vascular endothelial growth factor expression in the equine corpus luteum

Al-zi'abi¹

2003

“…In mice, SP exposure has been shown to be associated with increased ovarian leukocyte recruitment (Gangnuss et al 2004) with the processes of ovulation and luteinisation exhibiting characteristics reminiscent of an acute inflammatory response in both participating cell types and the chemical mediators involved (Espey 1994). The role of leukocyte populations in the porcine ovary is presently unknown, but studies showing similarities in rodents, humans and other livestock species (Brannstrom & Norman 1993, Brannstrom et al 1994, Lawler et al 1999, Van der Hoek et al 2000 suggest that leukocyte-mediated mechanisms are common across mammalian species.…”

Section: Introductionmentioning

confidence: 99%

Seminal plasma regulates ovarian progesterone production, leukocyte recruitment and follicular cell responses in the pig

O’Leary

Jasper²,

Robertson³

et al. 2006

Seminal plasma (SP) acts to influence the uterine endometrium after mating, activating synthesis of embryotrophic cytokines and inflammatory changes that condition the tract for embryo implantation and establishing pregnancy. The objective of this study was to investigate in pigs whether the ovary might also be responsive to SP exposure. Prepubertal gilts were synchronised with exogenous gonadotrophins and received transcervical treatment with pooled boar SP or PBS; then the ovarian tissue was recovered at 34 h (preovulation) and on days 5 and 9 after treatment. The ovarian response was assessed by measuring ovulation rate, number and size of corpora lutea, ovarian leukocyte populations, progesterone production in vivo, as well as responses of retrieved granulosa cells cultured in vitro. In SP-treated gilts, leukocyte recruitment into the ovarian tissues was increased fourfold at 34 h, with macrophages comprising the most abundant cell lineage. There was no effect of SP on the number of oocytes ovulated; however, the weight of corpora lutea was increased in SP-treated gilts. SP also induced an increase in plasma progesterone content seen from day 5 to at least day 9 after treatment. In addition, granulosa cells and thecal tissue retrieved from preovulatory follicles of SP-treated gilts were more responsive in vitro to growth factor-and gonadotrophin-stimulated cell proliferation and progesterone synthesis. These results suggest that uterine exposure to SP influences immune cell trafficking in the ovary and enhances steroidogenesis in early pregnancy. The effects of SP on ovarian function potentially contribute to reproductive success in the pig.

“…The day on which ovulation was detected was considered to be day 0. After appropriate sedation and analgesia, a colpotomy incision was used to remove the ovary containing the CL (Lawler et al 1999). This study was performed under the approval of the University of Edinburgh Ethical Review Committee and a project licence obtained under the Home Office Animals (Scientific Procedures) Act 1986.…”

Section: Animals and Tissue Collectionmentioning

confidence: 99%

Temporal relationship between proliferating and apoptotic hormone-producing and endothelial cells in the equine corpus luteum

Aguilar¹,

Fraser²,

Wilson³

et al. 2006

The temporal relationship between endothelial cell death, vascular regression and the death of hormone-producing cells in the mare has not been established. To determine the dynamics of cell proliferation and death throughout the luteal phase, corpora lutea were studied at the early, mid-and late luteal phase, and after treatment with cloprostenol in the mid-luteal phase to induce premature luteolysis. Changes in cell proliferation and apoptosis were investigated utilising specific markers (phosphorylated histone-3 and activated caspase-3 respectively). Histone-3 positive cells were most abundant during the early luteal phase, and were mainly present in endothelial cells. Histone-3 activity significantly increased in hormone-producing cells 36 h after cloprostenol treatment. Frequency of activated caspase-3 staining peaked on day 14, and was induced by 36 h after cloprostenol administration in mid-luteal phase. However, cell death occurred simultaneously in the endothelial and hormone-producing cells. These results show that a subset of hormone-producing cells enter the early stages of cell division around luteolysis, while the majority of cells are undergoing cell death. Natural and induced functional and structural luteal regression in the mare can be at least partially attributed to simultaneous apoptosis of endothelial and hormone-producing cells. However, there is no evidence that endothelial cell death is the trigger for naturally occurring luteolysis.