After injury, how does an animal "know" to start regenerating the missing tissues? We wonder about this too! We are researching one of the very first signals identified after injury: reactive oxygen species (ROS).
Above: Control trunk fragment of a recently amputated planarian labelled with a dye that marks ROS acculumation.
We are interested in determining the signals that initiate regeneration and tissue repair. Signaling downstream of reactive oxygen species (ROS) is known to regulate stem cell fate decisions, and ROS accumulation occurs at the wound site immediately after injury, making ROS signaling an important candidate. ROS are byproducts of aerobic metabolism that are highly reactive. And include molecules like superoxide and the second messenger hydrogen peroxide.
Our data shows that ROS signaling is required for the downstream expression of genes, such as the heat shock protein Hsp70, that are required for the stem cell proliferative response that follows injury in planarians. Without this signaling, the new tissues of the blastema do not grow and regeneration is inhibited. We are currently investigating the mechanisms (both upstream and downstream of ROS) that are involved.
Above: Control (on left) and ROS-inhibited (on right) regenerates labelled for actively dividing stem cells (green) reveal that ROS are required for new growth.