To begin to understand how tissue regeneration is regulated, we have studied how individual epithelial stem cells contribute to the process by tracking single cells and their behaviors over time (Figure 1). These approaches have allowed us to understand that location dictates stem cell fate (Rompolas, Nature 2013) and that extrinsic mechanisms involving TGF-β signaling and the phagocytic activity of neighboring cells regulate stem cell elimination (Mesa, Nature 2015). Yet we still lack an understanding of how these individual cell behaviors are coordinated at the tissue-wide level. 

We aim to elucidate a) how different molecular signals cross-talk to result in the specific cell behaviors that we have identified, b) how single cell behaviors affect neighboring cells in order to lead to controlled growth at the level of the whole tissue and c) how these cellular interactions are regulated by surrounding niche populations. 

In order to understand how each cell decision impacts surrounding cells we are using light-activated fluorophores that allow us to distinctly mark and track any cell of choice to provide a history of their behaviors over time (Figure 2 & Movie). Close monitoring of these cells and their neighbors as well as long time-lapse recordings are elucidating the consequences of each individual cell decision for its immediate neighbors at the level of a tissue. 

In order to improve our understanding of tissue regeneration we are studying the interactions between epithelial stem cells within the context of neighboring niche populations. We will monitor the above cellular and signaling mechanisms for each additional component that comes into contact with the regenerating epithelium: mesenchymal cells, immune cells including tissue resident macrophages, and structural elements such as the extracellular matrix. We use our established cell elimination approaches, such as laser ablation and inducible toxin expression, to evaluate the functional role of these different populations in epithelial regeneration.