Signaling dynamics in orchestrating stem cell functions during mammalian tissue regeneration - Summary Normal tissue structure and function rely on the regenerative capacities of tissue resident stem cells. These stem cells engage in essential activities like proliferation, migration, and differentiation, which must be carefully coordinated through dynamic signaling interactions to ensure effective tissue regeneration. Disruption of this process can give rise to diseases, including cancer. Thus, comprehending how dynamic signaling activations orchestrate stem cell behaviors to regenerate tissue and sustain tissue function is of paramount importance for advancements in regenerative medicine and cancer therapy. The inability to simultaneously track the dynamic signaling changes and stem cell activities in most mammalian tissues has been limiting our knowledge of the signaling mechanism of stem cell coordination. By generating novel signal sensors and employing our intravital imaging approach on a tissue regeneration model, the hair follicle, our previous studies have overcome this challenge and enable us to interrogate the functional significance of signaling dynamics at the single-cell level in orchestrating regenerative cell behaviors. Previous studies in culture systems and simple epithelial models have discovered regulatory roles of the distinct signal dynamics for specific cell behaviors. It remains largely unclear how dynamic signaling activations orchestrate diverse behaviors during complex tissue regeneration. Here, we study this question by using mouse hair follicle regeneration as a model, which requires both epithelial and mesenchymal signals. We hypothesize that stem cell behaviors are directly coordinated by epithelial ERK signal dynamics and indirectly influenced by TGFβ-mediated mesenchymal organization. We will test this hypothesis by defining the dynamics of the epithelial ERK (Aim 1) and mesenchymal TGFβ (Aim 2) signals and assessing the functional implications of those dynamics on stem cell behaviors and functions. We will apply intravital imaging, genetic, optogenetic, and pharmacological manipulations, as well as novel molecular analyses to gain new insights into the mechanisms by which dynamic signals orchestrate different cell behaviors to support effective tissue regeneration and uphold normal tissue architecture. The outcomes of the research will significantly advance our knowledge of the signaling mechanisms that both promote and disrupt tissue regeneration, which will pave the way for the development of innovative strategies to treat various diseases in the future.
