Effect Of Nitric Oxide On Expression Of Matrix Metalloproteinase-9 MRNA In Endometrium During Rat Embryo Implantation

Sexual mature mice were randomly assigned to 3 groups: non-pregnant group (withouttreatment),pregnant control group (treated with 0.9% sodium chloride injection) andinhibitor group (treated with nitric oxide synthase inhibitor). The mRNA expression ofmatrix metalloproteinase-9 (MMP-9) of mouse endometrium in the groups was determined bythe reverse transcription-polymerase chain reaction (RT-PCR). The objective of this study wasto investigate changes of mRNA expression of mouse endometrium MMP-9 in the earlyimplantation phase, implantation phase and late implantation phase and to determine the effectof nitric oxide (NO) on it. The results were as follows:1. The expression level of endometrium matrix metailoproteinase-9 mRNA during mouseembryo implantationThe results showed that there was the different expression of endometrium MMP-9mRNA in the non-pregnant mice and the pregnant mice during embryo implantation, whichwere found at a level of 0.47±0.01 in the non-pregnant mice and 0.81±0.05 in the earlyimplantation phase, 1.54±0.10 in the implantation phase and 0.40±0.02 in the laterimplantation phase, respectively. In comparison with the non-pregnant mice, the expression ofMMP-9 mRNA was significantly enhanced in the early implantation phase and in theimplantation phase (P＜0.01), reaching up to the fastigium in the implantation phase and thengetting back in the late implantation phase to the level of the non-pregnant mice.2. Effect of Nitric oxide on expression of matrix metalloproteinase-9 mRNA during mouseembryo implantationThe changes of the mRNA expression of mouse endometrium MMP-9 were determinedin the inhibitor group, in which production of NO was suppressed by treatment with nitricoxide synthase inhibitor L-NAME in the early implantation phase, implantation phase and lateimplantation phase. The results were showed that the mRNA expression of mouseendometrium MMP-9 in the early implantation phase (no expression) and implantation phase (0.47±0.15) in the inhibitor group was restrained and was significantly lower than that inpregnant control group (P＜0.01), while it was similar in the late implantation phase to that inthe non-pregnant group and the same phase in pregnant group (P≥0.05).3. Effect of nitric oxide on morphological changes of endometriumThe results of endometrial morphology showed distinctly endometrial development withhigh epithelium, proliferation of endometrial glands, big stromal cells of endometrium,loosened stroma and decidualisation of stroma in pregnant control group during the process ofembryo implantation. By comparaison, a relatively low epithelium and a few endometrialglands were found in the inhibitor group and the endometrium in the late implantation phaseshowed regressing changes with compactible stroma.In summary as above, nitric oxide as an endogenesis muscle loosenor and vesseldistendor may play a role in regulation on the expression of endometrium MMP-9 mRNA,which was decreased obviously when the production of NO was inhibited by nitric oxidesynthase inhibitor. The results of our study suggest that nitric oxide may influence theexpression of MMP-9 gene in transcriptional level and further effect on endometriumdevelopment and embryo implantation.