Restoration of extensive bone loss caused by trauma, resection of cancerous tumours, or metabolic bone diseases remains a significant challenge for reconstructive surgeons and patients. The clinical gold standard remains autologous bone grafting with over 2 million bone replacement procedures conducted globally each year. However, this procedure has limitations such as pain at the second surgical site and limited bone quantity available for grafting. Thus, researchers are investigating alternatives to bone grafting in order to overcome these challenges. The use of bone marrow-derived mesenchymal stromal cells (MSCs) delivered on a biomaterial scaffold is being investigated as an alternative to avoid the need to harvest healthy bone tissue from the patient and is showing promising results in clinical trials. However, that is also not without its challenges such as the requirement for cell expansion to obtain enough cells required for a therapeutic dose, the costly and time intensive quality assurance and characterization protocols of each donor or patient MSCs, and MSCs are only therapeutic at low passages so each bone marrow harvested has a limited expansion amount.
Critically, most MSCs are produced for bone repair in culture environments that are dissimilar to their native environment in the body. We postulate that by culturing MSCs in environments that mimic more closely their environment in the body they will be more therapeutically relevant. Furthermore, the therapeutic benefits of MSCs has been attributed to their secreted factors, in particular their secreted extracellular vesicles (EVs). EVs are nanoparticles that deliver bioactive cargo (nucleic acids, proteins, and lipids) between cells to communicate between cells. The objectives of the current project is to first identify the cell culture environments that yield EVs that are the most potent in terms of modulating the immune system to promote healing, as well as to attract host stem cells and aid those cells to differentiate into bone cells that can fabricate bone tissue. A further objective is to fabricate 3D constructs made out of these EVs and biomaterials that will allow release of the EVs to the surrounding damaged tissue, while also enabling degradation of the scaffold and healing of the bone void. The global aim is to develop a platform for targeted EV delivery in easy to transport and handle, ‘off-the-shelf’ 3D constructs, which in the future have the potential to reduce pain by elimination of bone or bone marrow harvest, and revolutionize the treatment of bone defects.
