Nitric oxide modulates murine yolk sac vasculogenesis and rescues glucose induced vasculopathy

Abstract

Nitric oxide (NO) has been demonstrated to mediate events during ovulation,pregnancy, blastocyst invasion and preimplantation embryogenesis. However,less is known about the role of NO during postimplantation development. Therefore, in this study, we explored the effects of NO during vascular development of the murine yolk sac, which begins shortly after implantation. Establishment of the vitelline circulation is crucial for normal embryonic growth and development. Moreover, functional inactivation of the endodermal layer of the yolk sac by environmental insults or genetic manipulations during this period leads to embryonic defects/lethality, as this structure is vital for transport, metabolism and induction of vascular development. In this study, we describe the temporally/spatially regulated distribution of nitric oxide synthase (NOS) isoforms during the three stages of yolk sac vascular development (blood island formation, primary capillary plexus formation and vessel maturation/remodeling) and found NOS expression patterns were diametrically opposed. To pharmacologically manipulate vascular development,an established in vitro system of whole murine embryo culture was employed. During blood island formation, the endoderm produced NO and inhibition of NO(L-NMMA) at this stage resulted in developmental arrest at the primary plexus stage and vasculopathy. Furthermore, administration of a NO donor did not cause abnormal vascular development; however, exogenous NO correlated with increased eNOS and decreased iNOS protein levels. Additionally, a known environmental insult (high glucose) that produces reactive oxygen species(ROS) and induces vasculopathy also altered eNOS/iNOS distribution and induced NO production during yolk sac vascular development. However, administration of a NO donor rescued the high glucose induced vasculopathy, restored the eNOS/iNOS distribution and decreased ROS production. These data suggest that NO acts as an endoderm-derived factor that modulates normal yolk sac vascular development, and decreased NO bioavailability and NO-mediated sequela may underlie high glucose induced vasculopathy.

Endothelial Nitric Oxide Synthase Gene Expression During Murine Embryogenesis

“…Nath et al documented expression of eNOS in the endothelium of extraembryonic blood vessels, presumably the vitelline circulation of the yolk sac, especially at E8.5. 43 We also observed strong eNOS promoter/␤-galactosidase reporter expression in the yolk sac, especially the endothelial layer of the yolk sac, which is consistent with the findings of others. 43,44 This is not surprising given that all 3 NOS isoforms are present in preimplantation embryos.…”

“…43 We also observed strong eNOS promoter/␤-galactosidase reporter expression in the yolk sac, especially the endothelial layer of the yolk sac, which is consistent with the findings of others. 43,44 This is not surprising given that all 3 NOS isoforms are present in preimplantation embryos. 45,46 In the embryo, we argue that the physical forces of the circulation are important to the expression of eNOS in the developing embryonic vasculature.…”

Endothelial Precursor Cell Migration During Vasculogenesis

“…A temporally and spatially regulated distribution of nitric oxide synthase (NOS) isoforms occurs during the 3 stages of yolk sac vascular development (blood island formation, primary capillary plexus formation, and vessel maturation/remodeling) and it was found that NOS expression patterns were diametrically opposed. From these results, it was suggested that NO acts as an endoderm-derived factor that modulates normal yolk sac vascular development, 64 possibly by the generation of a NO-gradient. No alterations of embryonic vasculogenesis have been described in eNOSknockout mice.…”

Peroxynitrites and impaired modulation of nitric oxide concentrations in embryos from diabetic rats during early organogenesis

“…Indeed, these agents down-regulated NO production in the embryos from control and mildly diabetic rats , but not in the embryos from severely diabetic rats, an alteration probably leading to a sustained NO production and further formation of peroxynitrite. Peroxynitrite formation may also impair NO bioavailability and thus its physiological functions, as suggested by the impaired effect of NO as a regulator of both PGE 2 production in oocytes and embryos from severely diabetic rats and murine yolk vasculogenesis under hyperglycemic conditions, even when NO is overproduced (Jawerbaum et al 1999, Nath et al 2004.…”