PARENT SESSION

(T479) PATTERN OF ENDOCRINE GLAND-DERIVED VASCULAR ENDOTHELIAL GROWTH FACTOR (EG-VEGF)/ PROKINETICIN-1 mRNA EXPRESSION IN BOVINE OVARIES THROUGHOUT THE ESTROUS CYCLE: MORE THAN ANGIOGENIC FACTOR.

Kisliouk, Tatiana¹, Podlovni, Helena¹, Zhou, Qun-Yong², Meidan, Rina¹, ¹ The Hebrew University of Jerusalem, Rehovot, Israel² University of California, Irvine, CA

ABSTRACT- Endocrine Gland-Derived Vascular Endothelial Growth Factor (EG-VEGF) or Prokineticin-1 (PK-1) is a novel secreted protein expressed in various tissues including steroidogenic glands. Although structurally non-related to VEGF, EG-VEGF/PK-1 was shown to promote angiogenesis acting via two G-protein coupled receptors (PK-R1 and PK-R2). Recently we demonstrated that EG-VEGF/PK-1 acts as a mitogenic and survival factor for bovine luteal EC: it enhanced cell proliferation and [3H]-thymidine incorporation, increased MAPK activation and c-jun/fos mRNA expression and inhibited apoptosis induced by serum starvation. Luteal EC express both PK-R1 and PK-R2 while steroidogenic cells predominantly express PK-R1 which suggests that this protein may also affect non-endothelial cells. To better understand tentative EG-VEGF/PK-1 roles in the bovine ovary, we cloned the bovine EG-VEGF/PK-1 cDNA sequence and examined its expression throughout the estrous cycle by quantitative real-time PCR. Levels of EG-VEGF/PK-1 mRNA were relatively high in estrogenic, healthy large follicles; it declined during ovulation, remained low at early and mid luteal stages, but sharply increased during luteolysis. The pattern of VEGF mRNA was different: levels were high during most of luteal phase and decreased only in later stages. Surprisingly, the highest EG-VEGF/PK-1 mRNA levels were detected in granulosa cells (GC) of atretic (non-estrogen active) follicles. As expected, VEGF mRNA was low in atretic follicles. Expression of PK-Rs correlated well with EG-VEGF/PK-1 mRNA levels, suggesting autoregulation by EG-VEGF/PK-1. Indeed, EG-VEGF/PK-1 augmented the expression of PK-R1 and PK-R2 in GC cultures. An inverse relationship between EG-VEGF/PK-1 and VEGF expression was also observed under in vitro conditions: incubation of GC for 2 - 6d in a luteinization promoting medium consisting of forskolin and insulin elevated VEGF and inhibited EG-VEGF/PK-1 expression. The profile of ovarian EG-VEGF/PK-1 expression throughout the bovine estrous cycle as well as the distinct pattern of PK-R expression in endothelial and steroidogenic cells suggest that in addition to its angiogenic effects, EG-VEGF/PK-1 may also mediate functions related to the apoptotic process in the ovary.

KEY WORDS: Corpus luteum, follicle, Apoptosis, granulosa cells