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Maternal cardiovascular changes during pregnancy and postpartum in mice
Alan Y H Wong1, Shathiyah Kulandavelu, Kathie J Whiteley
1Samuel Lunenfeld Research Institute at Mount Sinai Hospital, Toronto, M5G 1X5, Ontario, Canada.
This study examines how the heart and blood vessels change during and after pregnancy in mice. Researchers found that mice experience similar cardiovascular shifts to humans, such as lower blood pressure early on and increased heart pumping capacity later in pregnancy. These findings suggest that mice are effective models for studying human pregnancy-related heart health.
Area of Science:
- Cardiovascular physiology research within maternal medicine
- Mouse models of maternal cardiovascular regulation
Background:
No prior work had fully resolved whether murine models accurately replicate the complex hemodynamic shifts observed during human gestation. That uncertainty drove researchers to investigate if specific physiological markers in mice align with known human pregnancy patterns. It was already known that human pregnancy involves significant vascular remodeling and altered blood pressure regulation. Prior research has shown that animal models are frequently utilized to explore these systemic changes. However, the extent to which these small mammals mirror human cardiovascular adaptations remained unclear. This gap motivated a detailed assessment of blood pressure, heart rate, and cardiac output across different reproductive stages. Scientists sought to determine if mice could serve as reliable subjects for studying pregnancy-related cardiovascular health. Establishing this baseline is vital for future investigations into hypertensive disorders of pregnancy.
Purpose Of The Study:
The aim of this study is to determine if cardiovascular changes in mice during pregnancy and postpartum effectively mimic those observed in humans. Researchers sought to establish whether murine models provide a reliable platform for exploring complex hemodynamic regulation. This investigation addresses the need for accurate animal representations of human pregnancy-related vascular adaptations. The team hypothesized that specific physiological shifts would align across both species. By comparing these parameters, the authors intended to validate the use of genetically altered mice in future research. The study focuses on quantifying blood pressure, heart rate, and cardiac output across various reproductive stages. Understanding these baseline metrics is essential for interpreting data from experimental models. This work provides a foundation for investigating the mechanisms underlying pregnancy-induced cardiovascular adjustments.
Main Methods:
Review approach involved monitoring hemodynamic parameters in ICR (CD-1) mice across multiple reproductive phases. Investigators assessed arterial pressure and heart rate in awake subjects to ensure physiological accuracy. Researchers utilized intravenous administration to test vascular reactivity to angiotensin II at 17.5 days gestation. To evaluate cardiac output, the team employed isoflurane anesthesia during the late pregnancy period. Hematocrit levels were quantified to determine changes in blood composition throughout the study duration. Data collection spanned early pregnancy, late pregnancy, and various postpartum time points. Statistical analysis confirmed the significance of all observed hemodynamic variations. This systematic approach allowed for a comprehensive comparison between murine and human pregnancy adaptations.
Main Results:
Key findings from the literature demonstrate that cardiac output increases by 64% in late pregnancy compared to nonpregnant mice. This elevation stems from a 37% increase in stroke volume and a 17% rise in heart rate. Researchers observed that arterial pressure is 12% lower during early pregnancy than in late gestation or the postpartum period. Hematocrit levels show an 18% reduction at 17.5 days gestation. The pressor response to intravenous angiotensin II is diminished by approximately 33% at this same gestational stage. Heart rate measurements indicate a 10-20% increase during the peripartum interval. All reported hemodynamic changes reached statistical significance with P values below 0.05. These data collectively illustrate a consistent pattern of cardiovascular adjustment throughout the reproductive cycle.
Conclusions:
The authors propose that mice serve as valid models for human pregnancy-related cardiovascular adaptations. Synthesis and implications suggest that the observed physiological shifts in mice closely mirror those documented in clinical human studies. Researchers highlight that early gestation is characterized by a notable reduction in arterial pressure. The study confirms that a diminished pressor response to angiotensin II occurs during the late stages of pregnancy. Evidence indicates that hematocrit levels decrease significantly as gestation progresses toward delivery. The findings imply that cardiac output rises substantially in late pregnancy due to increased stroke volume and heart rate. These results support the utility of the mouse as a platform for investigating complex hemodynamic regulation. Future studies may leverage these established patterns to better understand pregnancy-related vascular changes.
Frequently Asked Questions
The researchers observed a 33% reduction in the pressor response to intravenous angiotensin II at 17.5 days gestation. This blunted reaction indicates that the vascular system becomes less sensitive to this specific hormone during late pregnancy in mice.
The study utilized awake ICR (CD-1) mice for blood pressure measurements and isoflurane-anesthetized mice for cardiac output assessments. These different states were necessary to capture accurate hemodynamic data without the confounding influence of anesthesia on resting pressure.
Late pregnancy requires anesthesia to measure cardiac output, as this state allows for the precise imaging or probe placement needed to quantify blood flow. Conversely, awake measurements are necessary to avoid the blood pressure-lowering effects of anesthetic agents.
Cardiac output data, obtained under isoflurane anesthesia, revealed a 64% increase in late pregnancy compared to nonpregnant controls. This rise is driven by a 37% increase in stroke volume and a 17% increase in heart rate.
The researchers measured hematocrit, which was found to be reduced by 18% at 17.5 days gestation. This physiological change reflects the hemodilution that typically occurs to support increased blood volume during pregnancy.
The authors propose that these findings validate the use of genetically altered mice to explore cardiovascular regulation. They suggest that because mice mimic human responses, they are suitable for modeling pregnancy-related heart conditions.