Examination of the Potential Effects of the Conceptus and Uterine Natural Killer Cells on Angiogenesis in the Mouse Uterus During Decidualization.

During rodent pregnancy, there is a period of time after implantation of the blastocyst but before the establishment of a fully functioning placenta that the maternal endometrium must provide nutrients to the developing conceptus. Angiogenesis occurs in the endometrium during this period known as implantation in order to meet the increased blood flow demand created by the increased tissue mass caused by decidualization. Although we know the conceptus and uterine natural killer (uNK) cells produce angiogenic factors, the precise role they have on uterine angiogenesis during decidualization in rodents is not well worked out. Therefore, the purpose of this study was to determine if the conceptus and uNK cells play a role in normal uterine angiogenesis during decidualization in mice. To do this, we collected tissue on days 6.5-8.5 from implantation sites from deciduas (conceptus present) and pseudopregnant bead-induced deciduomas (conceptus absent), respectively. Additionally, decidual tissue was collected on days 6.5 to 11.5 from implantation sites from both pregnant interleukin-15 (Il15) knockout (Il15 KO, lack uNK cells) and wild-type (Il15 WT) mice. The first aim of this study was to examine the potential roles of the conceptus and uNK cells on endothelial cell density and proliferation index in order to assess the vascular changes and angiogenesis in the endometrium. We found endothelial cell density to be significantly (P<0.05) greater on Day 6.5 in the decidua compared to pseudopregnant bead-induced deciduoma (Ps-BID). Conversely on that day, we found the mean proliferation index of endothelial cells to be significantly (P<0.05) greater in the Ps-BID compared to time-matched decidua. No differences were found in either endothelial cell density or mean proliferation index of endothelial cells on days 7.5 and 8.5. In addition, there were no observable differences on any of the days examined in implantation sites from Il15 KO compared to Il15 WT. The second aim of this study was to use quantitative RT-PCR analysis to measure the mRNA levels of endothelial cell markers (CD34 and Pecam1), transcription factors known to play a key role in angiogenesis (Fra1, Klf5, Runx1 and Runx2) and other factors potentially important in angiogenesis (Edg1 , Edg5, Gja1, Nrp1, Nrp2, Plgf, Vegfa, Vegfb, Vegfc, Vegfr1, Vegfr2). The mRNA levels of Ptgs2 and Edg5 were significantly (P<0.05) greater in the Ps-BID compared to the decidua on Day 6.5. Similarly, the level of mRNA expression of Plgf was significantly greater (P<0.05) in the Ps-BID compared to the decidua on days 7.5 and 8.5. Surprisingly, the level of mRNA for these transcripts at all other times examined, as well as at all times for the other mRNAs investigated, showed no significant difference between the Ps-BID and decidua or between Il15 KO and WT. In conclusion, the results do not strongly support the hypothesis that the conceptus or uNK cells play key roles in endometrial angiogenesis during decidualization in mice. (This work was supported by NIH grant HD049010 to BB). (poster)