Sarah Little-Letsinger

I completed my bachelor's degree in Human Nutrition, Foods, and Exercise at Virginia Tech in 2015. I then earned my master's degree (2017) and Ph.D. (2020) in Exercise Physiology from Texas A&M University. My doctoral research focused on inflammatory bone loss caused by space radiation and diet-induced obesity. My first postdoctoral fellowship was undertaken at the University of North Carolina at Chapel Hill School of Medicine in Endocrinology and Metabolism (2020-2021). My research at UNC focused on mechanisms linking bone marrow adiposity, including cell fate decisions in mesenchymal stem cells, bone mass and strength.

I became very interested in the bone marrow microenvironment, particularly in how the immune system regulates bone. Around this time, I learned that modern humans demonstrate skeletal gracilization (relatively thinner bones) similar to our ancestors. Temporal associations between a substantial rise in infectious disease burden (Neolithic transition) and skeletal gracilization deeply sparked my interest. I completed a second postdoctoral fellowship at Duke University in Evolutionary Anthropology (2021-2025) to gain a new understanding of bone structure and strength in humans and to gain new perspectives in evolutionary theory and environmental physiology.

Overall Research Program: The long-term goal of my research program is to determine robust biological and environmental regulators of lifelong bone health. It is my belief that osteoporosis is completely preventable for the vast majority of people. Much of my work has focused on inflammation-driven osteoporosis, including in models of space radiation, diet-induced obesity, aging, caloric restriction and physical inactivity. I am particularly interested in understanding: a) bone mass acquisition during adolescence, a critical period of bone development where over 90% of bone mass accrues; and b) bone loss due to aging of the reproductive and immune systems.

Current Research: The two major areas of my research focus are the integrative function and evolution of the skeletal, immune, and reproductive systems, or the osteoimmune-reproductive axis. My work is interdisciplinary, using perspectives from exercise physiology, mechanical engineering, immunology, reproductive biology, and evolutionary anthropology.

My current primary research line involves 'dirty mice' (e.g. wild or pet store mice) characterized by diverse microbial exposures which induce chronic immune activation. My efforts are primarily related to how immune defense and reproductive effort impact bone homeostasis (in bone marrow) across the lifespan with the goal to redefine osteoporosis pathogenesis. While this is my primary goal, my interests are broad and I am always looking for new collaborations!