Physiological processes are intimately connected to environmental cues, and resolving these connections is an important challenge for biology and medicine. The intestine is a tissue under constant environmental stress, not only due to the harsh process of digestion, but also because animals ingest harmful pathogens or chemicals often duringtheir lives. The intestine provides a barrier to handle these insults, and simultaneously it must absorb nutrients needed for survival. Both functions are critical and the intestine has evolved to respond to environmental damage very effectively.
The intestine has an incredibly high turnover of cells, perhaps the fastest of any tissue in the body. Cells are constantly replaced, even at baseline levels. Following injury, the intestine transitions from this state of steady cell turnover into a state of acute regeneration, where damaged cells are replaced very quickly. This incredible capacity for cell production is driven by a population of stem cells, which divide to make all intestinal epithelial cells.
This system provides a rich and fascinating area of research. A relatively unexplored area is how intestinal tissue turnover is timed. What, if any, timing underlies the production of intestinal cells from stem cells? How are these processes connected to the timing of feeding, injury, or general physiology? Circadian rhythms are 24 hour cycles of physiological change that occur in nearly all cells of the body, including those of the intestine.
Circadian rhythms are fundamental feature of living organisms, and they are driven by a genetic pacemaker inside the cells of our body called the circadian clock. This clock is set by day/night cycles, normally caused by the 24 hour rotation of planet Earth, but increasingly changed in modern society by shift-work, travel across time-zones, and changes to our schedules from weekday to weekend. Our research applies the intestine as a basic model of how daily environmental cues are propagated in the body, and raises important questions about this work pertinent to society and healthcare. To do this, our research merges chronobiology, physiology, and stem cell biology.