IDENTIFYING THE SOURCE OF SKELETAL PROGENITOR CELLS IN FRACTURE HEALING
Jenny Lei, Elise Morgan.
Boston University, Boston, MA.
The regenerative process of bone fracture healing provides an opportunity to study the sources of skeletal progenitor cells and the processes by which these cells differentiate into osteoblasts (bone-forming cells) or chondrocytes (cartilage-forming cells). The lessons learned can inform a multitude of approaches to encourage tissue healing and regeneration. This study aims to investigate fracture healing in mice in which cells expressing Prx1 (a gene associated with skeletal progenitor cells) are tagged with expression of beta galactosidase, an enzyme whose presence can be detected with a simple staining method. A transverse femoral fracture is generated by an externally applied blunt trauma and is stabilized by an intramedullary pin. The bolus of tissue that is formed at the fracture site, known as the callus, is initially loose connective tissue populated with progenitor cells. Over time, these cells differentiate into osteoblasts and, to a lesser extent, chondrocytes, resulting in large amounts of bone formation and, ultimately, a healed bone. Calluses will be harvested at post-operative days 7, 14, and 21. Histological analyses will be performed to visualize the tagged cells and to examine the spatial distribution of tissues. Micro-computed tomography will be used to visualize the 3D structure of the callus. Our hypothesis is that the skeletal progenitor cells originate in the periosteum, the membrane covering the outer surface of the bone. This study will identify the contribution of skeletal progenitor cells to healing and will set the stage for subsequent studies on how mechanical loading influences fracture healing.