Increased stiffness of omental arteries from late pregnant women at advanced maternal age

Abstract

Advanced maternal age (≥35 years) is a risk factor for poor pregnancy outcomes. Pregnancy requires extensive maternal vascular adaptations, and with age, our blood vessels become stiffer and change in structure (collagen and elastin). However, the effect of advanced maternal age on the structure of human resistance arteries during pregnancy is unknown. As omental resistance arteries contribute to blood pressure regulation, assessing their structure in pregnancy may inform on the causal mechanisms underlying pregnancy complications in women of advanced maternal age. Omental fat biopsies were obtained from younger (<35 years) or advanced maternal age (≥35 years) women during caesarean delivery (n=7-9/group). Arteries (200-300 µm) were isolated and passive mechanical properties (circumferential stress and strain) assessed with pressure myography. Collagen (Masson’s Trichrome) and elastin (Verhoff) were visualized histologically and % positively-stained area was assessed. Median maternal age was 32 years (range 25-34) for younger, and 38 years (range 35-42) for women of advanced maternal age. Circumferential strain was lower in arteries from advanced maternal age vs. younger women but circumferential stress was not different. Omental artery collagen levels were similar, while elastin levels were lower with advanced maternal age vs. younger pregnancies. The collagen:elastin ratio was greater in arteries from advanced maternal age vs. younger women. In conclusion, omental arteries from women of advanced maternal age were less compliant with less elastin compared to arteries of younger controls, which may affect how vascular stressors are tolerated during pregnancy. Understanding how vascular aging affects pregnancy adaptations may contribute to better pregnancy outcomes.

Commentary on: Increased stiffness of omental arteries from late pregnant women at advanced maternal age

“…Importantly, despite the mounting evidence and the increased global risk of adverse perinatal outcomes observed, few studies have examined the potential mechanisms underlying this elevated risk in pregnancies of AMA. The work of Wooldridge and colleagues begins to address this gap in the literature [ 7 ] and findings from their recent investigation suggest that maternal resistance arteries collected from pregnant women ≥35 years of age were less compliant and had less elastin than arteries obtained from women <35 years of age. Their findings suggest that alterations in maternal resistance vessel stiffness may contribute to increased risk of adverse maternal and fetal outcomes associated with pregnancy at AMA.…”

“…Furthermore, increased vascular stiffness assessed in vivo in early pregnancy is associated with the development of adverse pregnancy outcomes such as preeclampsia [ 14 , 15 ]. In their in vitro approach, Wooldridge et al [ 7 ] obtained omental adipose tissue during scheduled cesarean delivery at term (∼38–39 weeks gestation), isolated omental arteries from this biopsy, and examined collagen and elastin content – the main components of the extracellular matrix within the vascular wall. Previous studies have shown that aging leads to the overproduction of collagen and the degradation of elastin, which contributes to arterial stiffening [ 16 ].…”

“… Advanced maternal age (AMA, pregnancy at ≥35 years of age) is associated with increased omental artery stiffness – increased circumferential strain and decreased elastin content – at term (∼38–39 gestational weeks) compared with young (<35 years of age) pregnant women [ 7 ]. This increased stiffness may be due to an age-associated increase in pre-pregnancy resistance artery stiffness, a maladaptation to the cardiovascular demands of the pregnancy, or a combination of the two, driving changes in underlying vascular mechanisms.…”