Dynamic Assessment of Cortical Porosity in Preclinical Models: Time-lapse Imaging of Cortical Remodeling

A decade has passed since we published a review entitled: “Cortical Bone Porosity: What Is It, Why Is It Important, and How Can We Detect It?” (Curr.Osteoporos.Rep. 2016;14(5):187 − 98), which addressed the growing shift from bone mass to microarchitecture in osteoporosis research. It culminated in a brief examination of animal models of cortical bone porosity and the potential of using imaging to dynamically track cortical remodeling. Here we reflect on a decade of progress in this research space - preclinical time-lapse imaging of cortical pores/remodeling. Our objectives are to: (1) review time-lapse micro-CT imaging of bone microarchitecture in murine models; (2) overview of the development of synchrotron propagation phase contrast micro-CT imaging to track cortical porosity/remodeling in rabbits; and (3) discuss challenges and future directions. Despite first being demonstrated over 20 years ago, time-lapse micro-CT of trabecular bone in preclinical models has been relatively limited. Synchrotron imaging of rabbits has recently enabled the first time-lapse views of individual cortical remodeling events and associated findings have included linear erosion rates (LER) of remodeling spaces consistent with values inferred in classic canine studies, diverse and complex remodeling space morphologies particularly in parathyroid hormone-dosed animals where LER is also reduced, and disruption of linear advance in glucocorticoid-dosed animals. Time-lapse imaging of animal models holds tremendous potential to shed new light on the dynamic process of cortical remodeling as well as related diseases and the efficacy of their treatments.