Advanced imaging approaches for regenerative medicine: Emerging technologies for monitoring stem cell fate in vitro and in vivo

The future of regenerative medicine relies on our ability to control stem cell fate in order to produce functional tissues. Stem cells are the preferred cell source for tissue engineering endeavors and regenerative medicine therapies due to their high potency and capacity for expansion. However, their potency also makes them very difficult to control, as they are in a constant state of flux. Therefore, in order to advance research in regenerative medicine, it is necessary to be able to monitor cell state and phenotype both in vitro and in vivo. This review will detail the imaging technologies currently in use to monitor stem cell phenotype, migration, and differentiation. In addition to providing examples of the most recent work in this area, we will also discuss the future of imaging technologies for regenerative medicine, and how current imaging modalities might be utilized to image specific cell functionality in order to track stem cell fate. The research area of imaging stem cells is progressing toward identifying mature and differentiating cells not only by phenotypic markers, but also by visualizing cell function. Many of the cutting-edge modalities detailed in this review have the potential to be harnessed toward this goal. Stem cell biology and regenerative biology require frequent assessment of cell state. Imaging affords one powerful means to do so, and new technologies are rapidly emerging and undergoing modification to accommodate this need. In particular, special efforts are underway to better assess 3D environments (in vitro and in vivo) in which stem cells and progeny reside. This review details the imaging technologies currently in use to monitor stem cell phenotype, migration, and differentiation, as well as the future of imaging technologies for regenerative medicine.