RAISED, Raman and AFM Integrated Stem Cell Exploration of Differentiation, focused on elucidating the mechanisms triggered by external stimulation which drive stem cell fate. The control of stem cell fate via external stimulation is a vital contribution to the advancement of tissue engineering for regenerative medicine. Almost every kind of living cell will respond to a wide range of external stimuli; the direct stimulation of living cells is particularly interesting for the area of tissue engineering as stem cells can be triggered to differentiate from external stimuli such as electrical and mechanical signals. Delivering this signal to stem cells can be done via conductive biomaterials, designed to support the cells and promote the targeted differentiation. In RAISED we focused on understanding the influence of electrical and mechanical stimulation on human mesenchymal stem cells (hMSC) as they undergo osteogenic differentiation on a conductive polymer biomaterial. For the development of new conductive biomaterials for tissue engineering applications, understanding this fundamental relationship between the cells and the material is vital for progression of the field. The main objectives of RAISED were to use non-invasive single cell characterisation techniques, atomic force microscopy (AFM) and Raman micro-spectroscopy. These techniques allow us to measure changes in cellular properties, such as cell stiffness and biochemical changes, which can be correlated with changes in the intracellular structure. Changes in the intracellular structure are an integral part of stem cell restructuring as they differentiate towards different phenotypes for the formation of different tissue types, and hence this approach using non-invasive characterisation allows us to study this restructuring in real time as the stimulus is applied. This approach offers a much more efficient and informative measurements of stem cell response compared to standard biological assays and immunostaining.
The characterisation techniques developed in RAISED revealed that hMSC respond to electrical and mechanical stimulation on a very short time scale with long reaching differentiation consequences. The real-time characterisation measurements on the live hMSC measured near immediate changes in the cell elasticity, a property which is strongly correlated with intracellular cytoskeleton structure. Electrical stimulation disrupted the intracellular structure, resulting in inhibition of osteogenesis; this was correlated with conventional biological assays. These measurements demonstrated the ability to use cell elasticity measurements to predict the long-term stem cell fate in the presence of controlled external stimulation, and can now be applied to a broader approach in optimising electrical stimulation protocols. RAISED also demonstrated that control of human hMSC fate can be modulated via direct electrical stimulation, and the underlying mechanism behind this is the intracellular restructuring.
Throughout RAISED there was significant transfer of knowledge, specifically in training gained in using Raman micro-spectroscopy and biological culture and analysis, and training given in live cell AFM and other highly advanced AFM techniques and conductive polymer electrochemistry. The multidisciplinary environment at the Stevens Group and Imperial College London provided an excellent support for this very multidisciplinary project, and also fantastic opportunity for career development and growth through the interaction with the vast amount of expertise across a broad range of tissue engineering research within the group. Career development was also facilitated through training and courses through the Postdoctoral Development Centre at Imperial College London.
