When Dr. Ashley Walker (University of Oregon) began to study sex differences with vascular aging and cognitive decline, she and her team went to the literature for guidance on research study design to account for the confounding variable of estrous cycle in young female mice. Problem: There were no recommendations in the literature. Solution: The Walker Lab got to work. In our latest episode, Dr. Amanda LeBlanc (University of Louisville) interviews lead author Dr. Ashley Walker and first author Ms. Mackenzie Kehmeier (University of Oregon), along with expert Dr. Sarah Lindsey (Tulane University) about the novel study by Kehmeier et al. – the first of its kind – to show that the impact of estrogen on vascular stiffness changes with each day of the female mouse estrous cycle. The authors found that estrous phase was associated with lower in vivo large artery stiffness in mice, but ex vivo resistance artery endothelial function was not different between estrous cycle phases. Kehmeier et al. determined that estrogen receptor expression is modulated by the estrous cycle in an artery dependent manner, which means that estrous cycle phase in young female mice should be considered when measuring in vivo arterial stiffness. What techniques do the authors recommend for other investigators to best determine accurate staging of the estrous cycle? Listen to find out.   Mackenzie N. Kehmeier, Bradley R. Bedell, Abigail E. Cullen, Aleena Khurana, Holly J. D’Amico, Grant D. Henson, Ashley E. Walker In vivo arterial stiffness, but not isolated artery endothelial function, varies with the mouse estrous cycle Am J Physiol Heart Circ Physiol, published October 14, 2022. DOI: 10.1152/ajpheart.00369.2022