4D monitoring of stem cell differentiation by dielectric spectroscopic optical coherence tomography

In the recent years the therapeutic potential of stem cells has been recognized multilaterally. Still, the means to monitor their differentiation into different lineages are tedious and destructive precluding dynamic studies of 3D tissue regeneration. In this project, we propose to develop an imaging technology without biological labelling agents to monitor in time and space (4D) differentiating stem cell at a single-cell level. Every cell line has a bioelectrical signature that translates the response of a cell to a frequency dependent electro-magnetic field related to the proteins content of the cell membrane and cytoplasm. This bioelectrical signature is already exploited in dielectric spectroscopy and dielectrophoresis for cell sorting. A differentiating stem cell has a dynamic signature according to its various differentiation states. The biological mechanisms involved during EMF excitation generate also a change of the scattering properties of the cell by the reorganization of the cell components. This variation of the optical properties will be exploited to monitor in 3D at the single-cell level stem cell differentiation by Optical Coherence Tomography (OCT). OCT is a non invasive interferometric technique allowing in depth tissue imaging without labelling agent. Recent advances in OCT enables phase microscopy with nanometer resolution on the sample optical path. By synchronising a dielectric spectroscopic system with an OCT we will record a frequency dependent optical signature (FDOS) and will correlate it to differentiating event in 2D and 3D. Commercially adipose derived stem cells (ADSC) will be differentiated into three different lineages (bone, cartilage, adipose tissue) according to well established protocols in 2D culture plate and in commercial alginate matrixes supporting 3D culture. The multimodality of the new imaging technology (DSOCT) will be used to record differentiating events (optical, dielectric, and their combination (FDOS)) in real time. The sensitivity of the DSOCT will also be tested in collaboration with Dr. Hay by differentiating hESC into liver cells at three different developmental stages: mesendoderm, endoderm and hepatic endoderm. The new imaging technology ability to track various developmental stages of stem cell differentiation continuously and non invasively at the single-cell level without labelling agents will lead to many breakthroughs in regenerative medicine.