Sex-specific effects of advanced maternal age on cardiovascular function in aged adult rat offspring

Guidelines for assessing maternal cardiovascular physiology during pregnancy and postpartum

Maternal mortality rates are at an all-time high across the world and are set to increase in subsequent years. Cardiovascular disease is the leading cause of death during pregnancy and postpartum, especially in the United States. Therefore, understanding the physiological changes in the cardiovascular system during normal pregnancy is necessary to understand disease-related pathology. Significant systemic and cardiovascular physiological changes occur during pregnancy that are essential for supporting the maternal-fetal dyad. The physiological impact of pregnancy on the cardiovascular system has been examined in both experimental animal models and in humans. However, there is a continued need in this field of study to provide increased rigor and reproducibility. Therefore, these guidelines aim to provide information regarding best practices and recommendations to accurately and rigorously measure cardiovascular physiology during normal and cardiovascular disease-complicated pregnancies in human and animal models.

Guidelines for in vivo models of developmental programming of cardiovascular disease risk

Research using animals depends on the generation of offspring for use in experiments or for the maintenance of animal colonies. Although not considered by all, several different factors preceding and during pregnancy, as well as during lactation, can program various characteristics in the offspring. Here, we present the most common models of developmental programming of cardiovascular outcomes, important considerations for study design, and provide guidelines for producing and reporting rigorous and reproducible cardiovascular studies in offspring exposed to normal conditions or developmental insult. These guidelines provide considerations for the selection of the appropriate animal model and factors that should be reported to increase rigor and reproducibility while ensuring transparent reporting of methods and results.

Advanced parental age affects cardiometabolic risk in offspring

Advanced age at conception usually refers to human mothers aged 35 years plus and fathers aged 40 years plus. Advanced parental age may be responsible for genetic and/or epigenetic alterations and may affect the health of offspring. Limited epidemiological and experimental studies have addressed the effect of advanced parental age on cardio-metabolic functions in human and rodent offspring. This mini review aimed to present the knowledge by focusing on adverse and favourable outcomes related to sex-specific risks and intergenerational inheritance. The outcomes identified by this review were mainly negative, but there were also some positive results.

The association between assisted reproductive technology and cardiac remodeling in fetuses and early infants: a prospective cohort study

BACKGROUND

Limited data exist regarding the potential impact of assisted reproductive technology (ART) on cardiac remodeling. In particular, whether different ART techniques are related to different cardiac alterations remains unclear. We aimed to evaluate cardiac changes in fetuses and infants arising from ART and fetal cardiac alterations in fetuses conceived by specific ART procedures.

METHODS

This prospective and observational cohort study recruited 111 fetuses conceived by ART and 106 spontaneously conceived controls between December 2017 and April 2019. Echocardiography was performed between 28⁺⁰ and 32⁺⁶ weeks-of-gestation and at 0-2 and 6 months after birth.

RESULTS

A total of 88 ART fetuses and 85 controls were included in the final analysis. Compared to controls, ART fetuses demonstrated a globular enlarged left ventricle (LV) (LV sphericity index of mid-section, 2.29 ± 0.34 vs. 2.45 ± 0.39, P = 0.006; LV area, 262.33 ± 45.96 mm² vs. 244.25 ± 47.13 mm², P = 0.002), a larger right ventricle (RV) (RV area, 236.10 ± 38.63 mm² vs. 221.14 ± 42.60 mm², P = 0.003) and reduced LV systolic deformation (LV global longitudinal strain (GLS), -19.56% ± 1.90% vs. -20.65% ± 1.88%, P = 0.013; LV GLS rate S, -3.32 ± 0.36 s^-1 vs. -3.58 ± 0.39 s^-1, P = 0.023). There were no significant differences between the ART and control groups at postnatal follow-ups. Furthermore, we found fetal cardiac morphometry and function were comparable between different ART procedures. Compared to controls, the fetuses derived from various ART procedures all exhibited impairments in the LV GLS and the LV GLS rate S.

CONCLUSIONS

Our analysis demonstrated that subclinical cardiac remodeling and dysfunction were evident in ART fetuses, although these alterations did not persist in early infancy. In addition, various ART procedures may cause the same unfavorable changes in the fetal heart.

TRIAL REGISTRATION

This trial was registered at the Chinese Clinical Trial Registry ( www.chictr.org.cn ) ( ChiCTR1900021672 ) on March 4, 2019, retrospectively registered.

Rodent studies of developmental programming and ageing mechanisms: Special issue: In utero and early life programming of ageing and disease

Compelling evidence exists indicating that developmental programming influences ageing. Programming alters life-course phenotype in multiple organs, predisposing to diseases such as diabetes, obesity and cardiovascular disease that shorten lifespan. This review describes studies in rodents, the most commonly studied species, addressing interactions of programming challenges with ageing. We first consider ageing and programming of insulin function that has been clearly shown to decrease with age. It is important to evaluate ageing in pancreatic islets isolated from other systems. Studies discussed show premature pancreatic islet ageing resulting from both maternal under- and overnutrition. New ways to determine programming of adipose tissue and effects on fat storage are explored. Oxidative stress is a major factor that regulates ageing in tissues. Oxidative stress is discussed in relation to reproductive and cardiovascular ageing. Premature ageing is associated with both low and high glucocorticoid function. Both over and undernutrition have offspring sex-specific programming effects on life-course glucocorticoid concentrations. Evidence is provided that maternal age at conception affects offspring endocrine and metabolism ageing. Finally, the importance of matching foetal nutrition and energy availability with composition and energy content in the post-weaning diet is demonstrated. This mismatch can lead to a greatly shortened lifespan. General principles are discussed throughout. For example, sexual dimorphism of age-related outcomes can be marked. Accelerated ageing occurs early in life. Improving knowledge on programming ageing interactions will improve health span as well as lifespan. Finally, there are considerable similarities in outcomes programmed by maternal undernutrition and overnutrition.

Altered Vascular Adaptations to Pregnancy in a Rat Model of Advanced Maternal Age

Advanced maternal age (≥35 years old) increases the risk of pregnancy complications such as preeclampsia and fetal growth restriction. We previously demonstrated vascular dysfunction and abnormal pregnancy outcomes in a rat model of advanced maternal age. However, vascular adaptations to pregnancy in aging were not studied. We hypothesize that advanced maternal age is associated with a more vasoconstrictive phenotype due to reduced nitric oxide (NO) and increased activity of matrix metalloproteinases (MMPs), contributing to impaired vascular adaptations to pregnancy. A rat model of advanced maternal age was used: young (4 months) and aged (9.5 months; ∼35 years in humans) non-pregnant and pregnant rats. On gestational day 20 (term = 22 days; non-pregnant rats were aged-matched), blood pressure and heart rate were measured (tail cuff plethysmography) and vascular function was assessed in mesenteric arteries (wire myography). Endothelium-dependent relaxation to methylcholine (MCh) was assessed in the presence/absence of nitric oxide synthase inhibitor (L-NAME), or inhibitors of endothelium-dependent hyperpolarization (EDH; apamin and TRAM-34). Vasoconstriction responses to big endothelin-1 (bigET-1), in the presence/absence of MMPs-inhibitor (GM6001) or endothelin converting enzyme (ECE-1) inhibitor (CGS35066), in addition, ET-1 responsiveness, were measured. Blood pressure was elevated only in aged non-pregnant rats (p < 0.001) compared to all other groups. MCh responses were not different, however, L-NAME decreased maximum vasodilation in young (p < 0.01) and aged pregnant rats (p < 0.001), and decreased MCh sensitivity in young non-pregnant rats (p < 0.01), without effects in aged non-pregnant rats. EDH contribution to relaxation was similar in young non-pregnant, and aged non-pregnant and pregnant rats, while EDH-mediated relaxation was absent in young pregnant rats (p < 0.001). BigET-1 responses were enhanced in aged non-pregnant (p < 0.01) and pregnant rats (p < 0.05). No significant changes in bigET-1 conversion occurred in the presence of MMP-inhibitor, whereas ECE-1 inhibition reduced bigET-1 constriction in aged rats (p < 0.01). No differences in ET-1 sensitivity were observed. In conclusion, contrary to our hypothesis, reduced blood pressure, and an increased EDH-dependent contribution to vasodilation suggest a compensatory mechanism that may reflect beneficial adaptations in these aged rats that were able to maintain pregnancy. These data increase our understanding of how the vascular adaptive pathways in pregnancy compensate for advanced maternal age.

Early Life Oxidative Stress and Long-Lasting Cardiovascular Effects on Offspring Conceived by Assisted Reproductive Technologies: A Review

Assisted reproductive technology (ART) has rapidly developed and is now widely practised worldwide. Both the characteristics of ART (handling gametes/embryos in vitro) and the infertility backgrounds of ART parents (such as infertility diseases and unfavourable lifestyles or diets) could cause increased oxidative stress (OS) that may exert adverse influences on gametogenesis, fertilisation, and foetation, even causing a long-lasting influence on the offspring. For these reasons, the safety of ART needs to be closely examined. In this review, from an ART safety standpoint, the origins of OS are reviewed, and the long-lasting cardiovascular effects and potential mechanisms of OS on the offspring are discussed.

Aging Endocrine and Metabolic Phenotypes Are Programmed by Mother’s Age at Conception in a Sex-Dependent Fashion in the Rat

Programming of offspring life-course health by maternal nutrition and stress are well studied. At postnatal day 850, we evaluated male and female steroid levels and metabolism in aged offspring of primigravid sister rats bred at 70, 90, 150, or 300 days’ life. At 850 days life, male offspring corticosterone was similar regardless of maternal age. Female corticosterone was highest in offspring of 70- and 300-day mothers. Serum dehydroepiandrosterone:corticosterone was lowest in both sexes of offspring of 70- and 300-day mothers. Male and female fat depots were smaller in offspring of 150- than 70- and 90-day mothers. Insulin, glucose, and homeostatic model assessment were similar in all male offspring but higher in female offspring of 70-day mothers than other ages. We conclude, maternal age affects offspring aging in an offspring sex-dependent manner and merits consideration in designing and interpreting programming studies.

Advanced maternal age compromises fetal growth and induces sex-specific changes in placental phenotype in rats

Advanced maternal age is associated with an increased risk of pregnancy complications. It programmes sex-specific cardiovascular dysfunction in rat offspring, however the intrauterine mechanisms involved remain unknown. This study in the rat assessed the impact of advanced maternal age on placental phenotype in relation to the growth of female and male fetuses. We show that relative to young (3-4 months) dams, advanced maternal age (9.5-10 months) compromises growth of both female and male fetuses but affects the placental phenotype sex-specifically. In placentas from aged versus young dams, the size of the placental transport and endocrine zones were increased and expression of Igf2 (+41%) and placental lactogen (Prl3b1: +59%) genes were upregulated in female, but not male fetuses. Placental abundance of IGF2 protein also decreased in the placenta of males only (-95%). Moreover, in placentas from aged versus young dams, glucocorticoid metabolism (11β-hsd2: +63% and 11β-hsd1: -33%) was higher in females, but lower in males (11β-hsd2: -50% and 11β-hsd1: unaltered). There was however, no change in the placental abundance of 11β-HSD2 protein in aged versus young dams regardless of fetal sex. Levels of oxidative stress in the placenta were increased in female and male fetuses (+57% and +90%, respectively) and apoptosis increased specifically in the placenta of males from aged rat dams (+700%). Thus, advanced maternal age alters placental phenotype in a sex-specific fashion. These sexually-divergent changes may play a role in determining health outcomes of female and male offspring of aged mothers.

CORP: Practical tools for improving experimental design and reporting of laboratory studies of cardiovascular physiology and metabolism

The exercise consisted of: 1) a short survey to acquire baseline data on current practices regarding the conduct of animal studies, 2) a series of presentations for promoting awareness and providing advice and practical tools for improving experimental design, and 3) a follow-up survey 12 mo later to assess whether practices had changed. The surveys were compulsory for responsible investigators (n = 16; paired data presented). Other investigators named on animal ethics applications were encouraged to participate (2017, total of 36 investigators; 2018, 37 investigators). The major findings to come from the exercise included 1) a willingness of investigators to make changes when provided with knowledge/tools and solutions that were relatively simple to implement (e.g., proportion of responsible investigators showing improved practices using a structured method for randomization was 0.44, 95% CI (0.19; 0.70), P = 0.003, and deidentifying drugs/interventions was 0.40, 95% CI (0.12; 0.68), P = 0.010); 2) resistance to change if this involved more personnel and time (e.g., as required for allocation concealment); and 3) evidence that changes to long-term practices ("habits") require time and follow-up. Improved practices could be verified based on changes in reporting within publications or documented evidence provided during laboratory visits. In summary, this exercise resulted in changed attitudes, practices, and reporting, but continued follow-up, monitoring, and incentives are required. Efforts to improve experimental rigor will reduce bias and will lead to findings with the greatest translational potential.NEW & NOTEWORTHY The goal of this exercise was to encourage preclinical researchers to improve the quality of their cardiac and metabolic animal studies by 1) increasing awareness of concerns, which can arise from suboptimal experimental designs; 2) providing knowledge, tools, and templates to overcome bias; and 3) conducting two short surveys over 12 mo to monitor change. Improved practices were identified for the uptake of structured methods for randomization, and de-identifying interventions/drugs.Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/experimental-design-survey-training-practical-tools/.

Advanced maternal age and the impact on maternal and offspring cardiovascular health

Delaying pregnancy, which is on the rise, may increase the risk of cardiovascular disease in both women and their children. The physiological mechanisms that lead to these effects are not fully understood but may involve inadequate adaptations of the maternal cardiovascular system to pregnancy. Indeed, there is abundant evidence in the literature that a fetus developing in a suboptimal in utero environment (such as in pregnancies complicated by fetal growth restriction, preterm birth, and/or preeclampsia) is at an increased risk of cardiovascular disease in adulthood, the developmental origins of health and disease theory. Although women of advanced age are at a significantly increased risk of pregnancy complications, there is limited information as to whether advanced maternal age constitutes an added stressor on the prenatal environment of the fetus, and whether or not this is secondary to impaired cardiovascular function during pregnancy. This review summarizes the current literature available on the impact of advanced maternal age on cardiovascular adaptations to pregnancy and the role of maternal age on long-term health risks for both the mother and offspring.