Date of Award
MS in Biomedical Engineering
Biomedical and General Engineering
A Study of Osteocyte Apoptosis by Region and Quadrant in Murine Cortical Bone
Jessica Kristen Chan
Osteocytes undergo apoptosis to spatially and temporally initiate bone remodeling. This study investigates the distribution of apoptotic osteocytes within different quadrants and regions of cortical bone and compares the frequency of osteocyte apoptosis to regional factors associated with bone remodeling. Specifically, the quantity of apoptosis was compared to levels of the bone morphagenic protein antagonists noggin and gremlin. Samples of unloaded right tibial bone obtained from C57/Bl/6 mice underwent TUNEL staining for apoptotic osteocytes and were counterstained with methyl green to detect osteocyte viability. Cross sectional areas of bone were divided into four quadrants (cranial, caudal, medial, and lateral) and three regions (proximal, midshaft, and distal) for analysis. Densities and percentages of osteocytes were measured within each area. While the results show that there were no differences among quadrants, regional variations were found in osteocyte apoptosis. A significantly higher density of apoptotic osteocytes was found in the midshaft region which also displayed higher levels of BMP antagonists. Using regression analysis, a positive linear relationship between apoptotic osteocytes and gremlin was established while noggin showed a negative linear correlation for the percentage of apoptotic osteocytes. Further studies are needed to observe the distribution of apoptotic osteocytes within loaded bone to confirm the exact relationship between osteocyte apoptosis and bone remodeling.
Keywords: osteocyte apoptosis, bone remodeling