Maternal systemic vascular dysfunction in a primate model of defective uterine spiral artery remodeling

Abstract

Uterine spiral artery remodeling (UAR) is essential for placental perfusion and fetal development. A defect in UAR underpins placental ischemia disorders, e.g., preeclampsia, that result in maternal systemic vascular endothelial dysfunction and hypertension. We have established a model of impaired UAR by prematurely elevating maternal serum estradiol levels during the first trimester of baboon pregnancy. However, it is unknown whether this experimental paradigm is associated with maternal vascular endothelial dysfunction. Therefore, in the present study baboons were administered estradiol on days 25-59 of gestation to suppress UAR and maternal vascular function determined on day 165 (term = 184 days) peripherally and in skeletal muscle, which accounts for over 40% of body mass and 25% of resting systemic vascular resistance. Maternal serum sFlt-1 levels were 2.5-fold higher (P < 0.05), and skeletal muscle arteriolar endothelial nitric oxide synthase (eNOS) protein expression and luminal area, and skeletal muscle capillary density were 30-50% lower (P < 0.05) in UAR suppressed baboons. Coinciding with these changes in eNOS expression, luminal area, and capillary density, maternal brachial artery flow-mediated dilation and volume flow were 70% and 55% lower (P < 0.05), respectively, and mean arterial blood pressure 29% higher (P < 0.01) in UAR defective baboons. In summary, maternal vascular function was disrupted in a baboon model of impaired UAR. These results highlight the translational impact of this primate model and relevance to adverse conditions of human pregnancy underpinned by improper uterine artery transformation.NEW & NOTEWORTHY Maternal vascular dysfunction is a hallmark of abnormal human pregnancy, particularly early-onset preeclampsia, elicited by impaired UAR. The present study makes the novel discovery that maternal systemic vascular dysfunction was induced in a baboon experimental model of impaired UAR. This study highlights the translational relevance of this nonhuman primate model to adverse conditions of human pregnancy underpinned by defective UAR.

Keywords: artery; primate; remodeling; uterine; vascular.

Figure 1.

Representative (from total of n = 3) photomicrographs of fluorescent immunohistochemical labeling of baboon skeletal muscle capillary and arteriole endothelial cells with VWF (A), lectin (B), and CD31 (C). White arrowhead, green immunofluorescent VWF-labeled capillary endothelial cell; white arrow, green endothelial lining of arteriole; blue, DAPI-labeled muscle fiber nuclei. *Autofluorescence of red blood cells. Scale bar = 100 µm for all panels. VWF, von Willebrand factor.

Figure 2.

Representative photomicrographs illustrating PLA localization of eNOS protein (red dots/signals, white arrows) within endothelial cell lining of maternal skeletal muscle arterioles (110 µm luminal diameter-long axis in A) on day 165 of gestation in an untreated (A) and UAR suppressed (B) baboon. Inserts in upper right corner of A and B are high magnification of endothelial cell lining of arterioles. White arrowheads, green immunofluorescent VWF-labeled endothelial cells; yellow dots, colocalization of red PLA and green VWF-labeled endothelial cells; blue, DAPI-labeled muscle fiber nuclei. Scale bar = 25 µm for A and B and 2.5 µm for inserts in A and B. C shows the means ± SE level of eNOS protein within endothelium (red signals/µm² endothelial area × 10⁴) on day 165 in untreated (n = 6) and UAR impaired (n = 5) baboons. *P = 0.009 vs. untreated baboons. D depicts means ± SE maternal skeletal muscle arteriolar endothelial plus luminal area (µm²) on day 165 in untreated (n = 6) and UAR suppressed (n = 6) baboons. Closed (●) and open (○) circles represent individual data points. *P = 0.008 vs. untreated baboons (Student’s t test). DAPI, 4′,6-diamidine-2′-phenylindole; eNOS, endothelial nitric oxide synthase; PLA, proximity ligation assay; UAR, uterine spiral artery remodeling; VWF, von Willebrand factor.

Figure 3.

Representative photomicrographs depicting PLA localization of eNOS protein (red dots/signals) within transverse sections of maternal skeletal muscle fibers in an untreated baboon showing outline of myofiber endomysium (A) and after removal of autofluorescence background to show the presence of red PLA signals (B). Insert box in B is magnified and shown in C to more clearly illustrate red PLA eNOS signals. Green, immunofluorescent VWF-labeled endothelial cells of vessels located between myofibers. Scale bar = 25 µm (A, B, and C). D shows the means ± SE level of eNOS protein in myofibers (signals/µm² skeletal muscle fiber area × 10⁴) on day 165 of gestation in untreated (n = 6) and UAR suppressed (n = 6) baboons (no significant difference by Student’s t test). Closed (●) and open (○) circles represent individual data points. eNOS, endothelial nitric oxide synthase; PLA, proximity ligation assay; UAR, uterine spiral artery remodeling; VWF, von Willebrand factor.

Figure 4.

Maternal skeletal muscle [myosin fast (red) and slow (dark)] fibers of an untreated baboon shown in transverse section (A) and showing green VWF-labeled capillaries (B, white arrow). Dotted yellow line circumscribed around a group of myofibers in A and B illustrates area used to quantify by image analysis means ± SE VWF-positive capillary (cap) density (capillaries/myofiber cross-sectional area) (C) and capillary/muscle fiber ratio (capillaries/muscle fiber number × area) (D) on day 165 in untreated (n = 6) and UAR suppressed (n = 6) baboons. Scale bar = 100 µm for A and B. Closed (●) and open (○) circles represent individual data points. *P = 0.029; **P = 0.05 vs. untreated baboons (Student’s t test). UAR, uterine spiral artery remodeling; VWF, von Willebrand factor.

Figure 5.

Maternal brachial artery flow-mediated dilation (FMD; A) and volume flow (B) expressed as the percent change versus basal level during the 5-min interval following induction of hyperemia/shear stress in untreated (n = 5) and UAR suppressed (n = 6) baboons. Values are the means ± SE of the average of the percent change in FMD and volume flow values obtained on days 100 and 165 of gestation. Closed (●) and open (○) circles represent individual data points. *P = 0.043 (A) and *P = 0.05 (B) vs. untreated baboons (Student’s t test). FMD, flow-mediated dilation; UAR, uterine spiral artery remodeling.

Figure 6.

Maternal means ± SE arterial blood pressure (MABP, A) and heart rate (B) on day 165 in untreated (n = 6–7) and UAR defective (n = 7) baboons. Closed (●) and open (○) circles represent individual data points. *P = 0.004 (A); P = 0.012 (B) vs. untreated baboons (Student’s t test). UAR, uterine spiral artery remodeling.

Figure 7.

A: representative Western immunoblot of catalase, pan-actin, heme oxygenase-1 (HO-1), superoxide dismutase (SOD1), and thioredoxin peroxidase (TRX) protein expression in maternal skeletal muscle on day 165 of UAR suppressed (n = 3) and untreated (n = 3) baboons. Catalase, actin, SOD1, and TRX electrophoresed on the same membrane and HOX-1 on a separate membrane and protein bands positioned for illustrative purposes. B: mean (SD) levels of maternal skeletal muscle oxidative stress markers quantified by Western immunoblot (expressed as a ratio of pan-actin) on day 165 of gestation in untreated (n = 7) and UAR suppressed (n = 6) baboons. *P = 0.045 vs. untreated (Student’s t test). ND, not detectable. HO-1, heme oxygenase-1; SOD1, superoxide dismutase; UAR, uterine spiral artery remodeling; TRX, thioredoxin peroxidase.

Figure 8.

Nonhuman primate model of preeclampsia elicited by a defect in uterine spiral artery remodeling.