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LOCALIZED EXPRESSION OF MRNAS FOR ANGIOPOIETINS (ANG-1, ANG-2) AND THEIR SPECIFIC RECEPTOR (TIE-2) IN THE PRIMATE CORPUS LUTEUM (CL) DURING THE MENSTRUAL CYCLE.
Hazzard, Timothy1, Nayak, Nihar1, Stouffer, Richard1,2, 1 2
ABSTRACT- There is increasing evidence that the angiopoietin-receptor system, which has been demonstrated to be present in the primate corpus luteum (CL), is an important regulator of angiogenesis. To determine whether there are localized changes in expression of this ligand-receptor system that could be related to luteal microvascular function, experiments were designed to specifically localize Ang-1, Ang-2 and the Tie-2 mRNAs in the macaque CL throughout its lifespan in the menstrual cycle. Serum steroids were monitored in female rhesus monkeys to estimate the day of the midcycle LH surge. CL were collected in the early (3-5 days post LH surge), mid (6-8 days), mid-late (10-12 days), and late (14-16 days) luteal phase, as well as at the time of menstruation (17-18 days; n=3/stage). Tissues were bisected and stored for total RNA and in situ hybridization (ISH). RT-PCR resulted in specific products that were confirmed by sequencing and used to create anti-sense probes. A specific ISH signal (corrected for nonspecific background) was evident for Ang-1, Ang-2 and Tie-2 in luteal tissue at all stages. Ang-1 and Tie-2 were expressed homogeneously throughout the luteal sections, while Ang-2 expression was in a punctate manner throughout the tissue. However, there is a lack of any specific compartmentalization of the angiopoietins and Tie-2 signal from the periphery to the center of the CL. Whereas Ang-1 expression (grains/unit area) did not change throughout the luteal lifespan, Ang-2 expression tended to increase (p=0.06) in the late luteal phase. In addition, Tie-2 expression increased from early to late luteal phase (p<0.05). Finally, because of opposing roles of the angiopoietins, the Ang-2/Ang-1 ratio was calculated, revealing a 2-fold increase from early to late luteal phase. Taken together, the dynamic expression of the angiopoietin-receptor system supports a functional role for Ang-1, Ang-2 and Tie-2, which may be critical for the development, maintenance, and degeneration of the microvasculature in the macaque CL during the menstrual cycle. Supported by NIH/NICHD U54 HD18185, HD22408, NCRR RR00163 and Training Grant HD07133.
KEY WORDS: angiopoietins, primate, corpus luteum, ovary