Nitric oxide in blastocyst implantation in the rhesus monkey

Abstract

Successful blastocyst implantation depends on the interaction between cells of maternal endometrium and conceptus, as well as adequate blood supply to the site of blastocyst implantation. Nitric oxide (NO) generally plays a significant role in the local regulation of vascular physiology in a variety of mammalian tissue systems, however, its role in blastocyst implantation and placentation in the primate is not known. The aim of the present study was to examine: (i) NADH-diaphorase activity and expression of three isoforms of nitric oxide synthase (NOS), namely endothelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS) in pre-implantation stage monkey embryos, morula (n 5 4) and blastocyst (n 5 10), as well as, in different compartments of conceptus and maternal endometrium at primary implantation sites during lacunar (n 5 6) and villous (n 5 9) stages of placentation in the rhesus monkey, and (ii) the potential anti-nidatory effect of vaginal administration of NOS inhibitor during the peri-implantation period of conception cycles in rhesus monkeys. Pre-implantation stage blastocysts exhibited marked NADPH-diaphorase activity along with immunopositive iNOS mainly in the inner cell mass. During the lacunar stage, marked eNOS expression was observed in cytotrophoblast cells lining the embryonic cavity. However, cytotrophoblast cells lining villi, forming columns, and constituting anchoring villi expressed all the three isoforms of NOS in villous placenta stage tissue. During the lacunar stage, eNOS and iNOS protein expressions were observed in epithelial and decidual cells of endometrium. As gestation advanced, mRNAs for all three isoforms of NOS were observed to increase in epithelial and decidual cells, however, with no marked change in protein expression. Vaginal administration of a NOS inhibitor (N G -nitro-L-arginine methyl ester, L-NAME, 4, 6, and 8 mg/kg body weight or aminoguanidine, AG, 4 mg/kg body weight) during days 6 to 12 after ovulation resulted in pregnancy failure in a higher number of animals (L-NAME: 8 confirmed pregnancies in 25 animals; AG: 2 confirmed pregnancies in 8 animals) compared with control animals (5 pregnancies in 7 animals). It appears that NO may play an important role in the establishment of pregnancy in the rhesus monkey.Reproduction (2005) 130 321-332

Expression and Localization of NO Synthase Isoenzymes (iNOS and eNOS) in Development of the Rabbit Placenta

“…Likewise, iNOS expression in human endometrial stromal cells can be enhanced by IL-1β and IFN-γ [40]. These cytokines, including IFN-γ and IFN-ω in rabbits [41], are considered to be engaged in the implantation-recognition process by advancing embryo infiltration and tissue remodeling of the endometrium via effects of NO and matrix metalloproteinase [18]. It seemed that induction of NOS isoenzymes is an underlying event in the developing placenta in the postimplantation period for initiation and reconstruction of placental vascular systems.…”

“…With the advancement of rabbit pregnancy, vascular remodeling in the maternal and fetal vessels becomes dominant, as shown by the narrowing intervillous spaces and drastic ramifications in the labyrinth. Recent studies in various mammalian species indicate that NO acts as a major modulator of uterine blood flow during pregnacy [13], placental-fetal blood flow [14] and placental angiogenesis [2].The distribution of iNOS and eNOS has been confirmed in the placentas of many animal species including the human [15], rat [16], sheep [3,17] and rhesus monkey [18]. In spite of the fact that the rabbit is a useful research model in the field of reproductive and developmental biology, previous published literature is absolutely silent about the assessment of iNOS and eNOS in the rabbit placenta.…”

“…The distribution of iNOS and eNOS has been confirmed in the placentas of many animal species including the human [15], rat [16], sheep [3,17] and rhesus monkey [18]. In spite of the fact that the rabbit is a useful research model in the field of reproductive and developmental biology, previous published literature is absolutely silent about the assessment of iNOS and eNOS in the rabbit placenta.…”

Protective effects of baicalin on lipopolysaccharide (LPS)-induced implantation failure and the uterine endometrium in mice

“…The embryo implantation is unsuccessful with blocking NO production. The studies have shown that great amounts of NO and NOS might play a role in the pathogenesis of endometriosis (Wu et al, 2003), and NO might play an important role in the establishment of pregnancy in the rhesus monkey (Sengupta et al, 2005). NO production was increased in LPS-induced embryonic resorption mice, mainly due to the induction of expression of inducible nitric oxide synthase (iNOS) isoform in the decidua and uterus, and neuronal nitric oxide synthase (nNOS) isoform in the decidua (Ogando et al, 2003).…”

Presence of Nitric Oxide Synthase Immunoreactivity and mRNA in Buffalo (Bubalus bubalis) Oocytes and Embryos

“…Using NADPH diaphorase staining, NOS activity has been reported to be higher in the inner cell mass (ICM) than in the trophectoderm in mouse (Nishikimi et al. 2001) and monkey blastocysts (Sengupta et al. 2005).…”