The Application of miRNA in Bone Tissue Engineering

Bone defects, which can be caused by trauma, tumor resection, infection and skeletal abnormalities, are capable of regenerating by itself when the injury is small such as in stable fracture. However, when the defect is large or if there is insufficient vascularity, aid is needed to heal the defect. Among the different strategies that are currently being applied to repair bone defects, bone autographs are considered the gold standard of treatment. Due to problems associated with this method, such as pain at the donor site, the need for two surgeries, the risk of infections as well as availability of appropriate grafts with the right shape and volume, the repair of bone defects still remains a challenge for orthopedic and reconstructive surgeons and thus, alternative treatment methods are much needed and should be developed. Tissue engineering which has the ultimate goal of using the body’s own capacity instead of grafts or artificial prostheses, to guide the wound healing process toward tissue regeneration, is a promising approach to repair bone defects. Extensive research has been focused on delivering growth factors for bone tissue engineering. Shortcomings associated with delivering growth factors in the protein form, such as the short half-life of protein and cost and difficulty of manufacturing these recombinant proteins, have led to the search of other methods of delivering bioactive factors to the defect site to aid in bone regeneration. By controlling the production of proteins capable of inducing osteogenesis in vivo, the proteins can be delivered in a more biologically active form with more precise post-translational modification and tertiary structure formation compared to the exogenous growth factors that may be altered through the delivery process. The overexpression of microRNAs (miRNAs) to regulate in vivo production of specific bioactive factors that are vital for bone regeneration can be a promising alternative to current treatments of delivering growth factors as recombinant protein. The goal of this project was to identify and select the miRNA that has the optimal ability to induce osteogenesis to promote bone regeneration. Through literature search, miRNAs that have the potential to induce osteogenesis were identified. These miRNAs were then evaluated and tested side by side in vitro to determine and select the miRNA that has the optimal ability to induce osteogenesis. This was done by overexpressing these miRNAs in mesenchymal stem cells (MSCs) and determining the expression of osteogenic marker protein and mRNA levels by immunoblotting and reverse transcription polymerase chain reaction (RT-qPCR), respectively.