Using a tissue-stretcher, I showed that different epithelial cells of the gut lining have different biomechanical properties. The absorptive enterocytes are elastic and can be stretched in response to mechanical stretching. Stem and progenitor cells are solid-like and are more resistant to stretching forces. When the fruit flies were subjected to mechanical stress by feeding them with micron-sized beads, I observed an increase in ISC division and a specific increase in newly produced enteroendocrine cells. Such biomechanical signaling-dependent differentiation of ISCs to secretory enteroendocrine cells required CCN function in the stem and progenitor cells. Currently, we are testing the role of CCN downstream of mechanosensory channel proteins like Piezo and TrpA1, to regulate force-dependent upregulation of secretory cell production.
Although ISCs normally remain relatively stationary within their niche, I showed that localized epithelial damage triggers rapid, directed ISC migration toward the wound within just 2–6 hours. Mechanical and chemical insults, such as short‑term exposure to DSS or brief oral infection with Pseudomonas entomophila, generate small epithelial breaches identified by the loss of E‑Cadherin and leakage of fluorescent dextran through the gut barrier. Using live imaging of whole-mount gut explants, the authors demonstrate that ISCs actively move toward these disrupted regions, forming clusters around damaged sites. Importantly, this migration occurs before any detectable ISC divisions, indicating that motility is the earliest regenerative response. The PDGF/VEGF‑related receptor Pvr was identified as an essential regulator of ISC motility. When Pvr is specifically depleted in ISCs, both ISC migration and the formation of actin-based cellular protrusions are completely abolished. These protrusions are normally induced within hours after injury and reflect dynamic cytoskeletal remodeling required for movement. As a consequence of Pvr loss, infection‑ or damage‑induced ISC proliferation and epithelial turnover are also strongly suppressed, demonstrating a tight link between ISC motility and regenerative divisions. Conversely, artificial activation of Pvr within ISCs is sufficient to trigger broad, flattened cell morphologies, robust Rac1 activation, lamellipodia formation, and accelerated tissue turnover even in the absence of damage. Together, these findings show that Pvr signaling is both necessary and sufficient to drive ISC activation during regeneration.
The gut lining is made of a single layer of cells that must constantly replace themselves to maintain proper function. This replacement is driven by special cells called stem cells. For the tissue to work correctly, these stem cells need to be evenly spaced so they can produce new cells wherever they are needed. When the gut is injured, for example, by infection or toxins, this organized pattern is disrupted. Stem cells leave their usual positions and move toward the damaged area to help repair it. Once the wound is healed, the tissue must carefully rebuild its original pattern of evenly spaced stem cells. My work sheds light on two proteins on the surfaces of gut cells, called Cirl and Toll‑8, that play an essential role in rebuilding this organization. These two proteins are found in different cell types, Cirl on stem cells and the Toll-8 on mature enterocytes. Because of this, they act like a “matching pair” that helps neighboring cells recognize each other. When stem cells and mature cells interact through these proteins, they create tiny mechanical forces at their shared boundaries. These forces help maintain proper spacing and ensure that stem cells remain in the right places.
Overall, my findings show that Cirl and Toll‑8 together act as a system that helps the gut maintain its architecture and restore it after injury. By converting differences in cell identity into physical signals, they help the tissue organize itself during both normal upkeep and regeneration. Because the molecules we studied are evolutionarily conserved, these results may shed light on how other organs in humans maintain their structure and recover from damage.
