Endometrial decidualization does not trigger the blood pressure decline of normal early pregnancy in mice

Abstract

A drop in mean arterial pressure (MAP) characterizes early, normal pregnancies of humans and of inbred mice, species with hemochorial placentation. Murine MAP, assessed by continuous radiotelemetry, falls from implantation to Gestation Day 9 (GD9) and then recovers. The change in the trajectory of mouse MAP after GD9 coincides with full maturity of the placenta and onset of its circulation. To identify whether these early gestational changes in hemodynamic function are conceptus and/or maternally regulated, pseudopregnancy (conceptus absent) with endometrial decidualization was established in radio transmitter-implanted, randomly bred CD1 mice. To avoid destabilization of MAP by anesthesia and surgery, decidualization was induced by transcervical infusion of concanavalin A-coated Sepharose beads 48 h after the female had copulated with a vasectomized male. In comparison to the postimplantation drop in MAP recorded in CD1 females mated by fertile males, pseudopregnancy MAP was stable to Gestation-Equivalent Day 10 in mice with confirmed endometrial decidualization at euthanasia. Thus, decidualization, with its accompanying pregnancy-like endocrine environment and uterine neoangiogensis and immune cell recruitment, is inadequate to depress early postimplantation MAP. These data suggest that the physiological modulation of early gestational MAP is not driven by maternal changes but is altered through conceptus-based mechanisms.

Figure 1

Mean arterial pressure patterns for six CD-1 mice between mating and gestation day (gd)11. The 24h data collection interval for gd11 ended at 7AM on the 12th day of gestation. (A) Mean arterial pressure (MAP), (B) Systolic arterial pressure (SAP), (C) Diastolic arterial pressure (DAP), (D) Pulse pressure. Heart rate and activity (not shown) were not altered from baseline. *P < 0.05.

Figure 2

Mouse uteri at gestation equivalent day (ged)12.5, following administration of Conconavilin A coated Sepharose beads into left uterine horn at ged2.5. (A) Gross anatomy of a representative “pseudopregnancy with decidua” uterus. (B) Photomicrograph of a representative hematoxylin and eosin stained decidual swelling. Scale bar: 200 μm. (C) Photomicrograph of serial section of decidual swelling in B stained with Dolichos bifloris agglutinin lectin and counterstained with hematoxylin for detection of uNK cell plasma membranes and granules (brown). Scale bar: 200 μm (B, Ci). Scale bar: 12.5 μm (Cii). AM, anti-mesometrial; M, mesometrial; UL, uterine lumen remnant containing Sepharose bead.

Figure 3

Differences in arterial pressures from baseline for each reproductively distinct group. Black circle pregnant CD-1, n = 6 (data derived from Figure 1); textured circle pseudopregnant decidualized CD-1, n = 10; open circle pseudopregnant non-decidualized CD-1, n = 4. (A) ΔMean arterial pressure (MAP), (B) ΔSystolic arterial pressure (SAP), (C) ΔDiastolic arterial pressusre (DAP), (D) ΔPulse pressure. Δ Heart Rate (HR) and Δactivity did not differ (not shown). Pseudopregnancy decidua did not induce significant changes over time. Values in pseudopregnant groups were statistically different (P < 0.05) compared pregnancy with φ= pseudopregnant decidualized; γ= pseudopregnant non-decidualized.