KEYNOTE PRESENTATION

XRM Imaging to Evaluate Osteocyte
Direction of Bone Quality

Virginia L. Ferguson, Ph.D.

Dr. Virginia Ferguson received her Ph.D. in mechanical engineering with an emphasis on the mechanical behavior of skeletal tissues from the University of Colorado in Boulder, CO, USA, in 2001. She currently holds the Hudson Moore Jr. professorship and is an Associate Professor of Mechanical Engineering while serving as an Associate member in BioServe Space Technologies, the BioFrontiers Institute, and the Materials Science and Engineering program at the University of Colorado. Her work to date has resulted in 89 refereed publications and book chapters, where many emphasize the use of nanometer-scale property assessment and high-resolution imaging to study both bone and soft tissues following aging and disuse from microgravity. Her research also includes using 3D printed polymeric materials for stem cell-based musculoskeletal tissue regeneration. Dr. Ferguson is currently funded to support rodent spaceflight projects on the International Space Station by both the Center for Advancement of Science in Space (CASIS), an organization that is charged with operating the International Space Station as a USA National Laboratory, and the National Space and Aeronautics Association (NASA). Her work in musculoskeletal tissue mechanics and tissue engineering is supported by the National Institutes of Health (NIH). Dr. Ferguson runs the Materials Instrumentation and Multimodal Imaging Core (MIMIC) Facility at the University of Colorado that includes a ZEISS Xradia Versa 520 imaging system and an integrated system that links a Bruker Triboindenter TI-950 with a Renishaw InVia Raman spectroscopy system, for which she was awarded ~1.75 million USD from the National Science Foundation. She is an active teacher and mentor of undergraduate and graduate students. Dr. Ferguson is active in many national and international societies, including the Orthopaedic Research Society, the American Bone and Mineral Research Society, and the American Society of Mechanical Engineers; she regularly serves as an ad hoc member on NIH and other proposal review panels and is a corresponding editor for the Journal of Biomechanics.

Bone is highly adaptive and remodels in response to strains that are sensed by osteocytes. These cells exist in micrometer-sized bony ‘caves’ called lacunae and extend dendrites to form complex, interconnected networks throughout bone tissue for sensing strain and communication. While numerous, osteocytes are difficult to study as they are encased within the bone and their extraction by destructive means is challenging.

X-ray microscopy (XRM) makes it possible to visualize the bony lacunae and bone tissue surrounding osteocytes in situ. Here, we describe the optimization of methods developed in our lab to visualize hundreds to thousands of osteocyte lacunae. We also describe how we analyze these osteocyte lacunar networks using spatial statistics to demonstrate how these cells adapt to the removal of normal mechanical loading in a spaceflight study of mice on the International Space Station. Finally, we demonstrate preliminary results where we are using reference materials to quantify the tissue mineral density in locations surrounding osteocytes.