Austin Wesner, “The Role of Activated Mesenchymal Stem Cells in Bone Regeneration After Injury”
Mentor: Priyatha Premnath, Biomedical Engineering
Bone has the ability to regenerate completely after injury, but diseases like osteoporosis and diabetes impair this healing cascade, sometimes causing non-union of bone after injuries. Stem-cells, specifically mesenchymal stem cells (MSCs), based therapies have been proposed to improve the regenerative capacity of bone in such instances. Yet, these therapies have not proven successful owing to quiescence of these stem cells once injected in vivo. Consequently, endogenous stem cell therapies have been garnering interest where resident stem cells are activated to enhance regeneration. Chemokines and growth factors have been used with some success to improve healing; other genetic approaches are also sought. We recently demonstrated that systemic activation of cell cycle by inhibiting p21 enhances bone regeneration. While we showed that MSCs played a role in regeneration, the exact mechanisms remain unknown. This project aims to examine the specific role of MSCs in regeneration through constitutively activating cell cycle in the MSCs. Since p21 is involved in several signaling pathways, E2F1 is chosen to activate cell cycle as E2F1 acts directly on the transcription of genes. A genetically modified mouse has been engineered for MSCs (PRX1+ cells) to be activated by overexpressing E2F1. Burr-hole injuries were performed on mice, and mice were sacrificed at various stages post injury (3, 7 and 10 days). Samples were then fixed, decalcified, processed and embedded in paraffin wax. The samples were cut into 10μm thick slices and mounted on glass slides. Histology was performed by staining with Safranin-O and fast green, for cartilage and bone respectively. Experiments to stain samples and analyze them are still ongoing. immunofluorescence staining is also proposed to assess number of chondrocytes and osteoblasts present at site of injury temporally. Through this project we will be able to tease out the role of activated MSCs in bone regeneration after injury.
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