Otsuki: Principles of vertebrate tissue regeneration Back to research group The Otsuki group investigates how complex vertebrate tissues – such as limbs and jaws – can be regenerated. What kind of cells do we need for regeneration? How many, and in which combinations? What are the molecular mechanisms that ensure that a regenerated tissue has the correct size, shape and function? To answer these types of questions, we study a highly regenerative salamander species called the axolotl – one of the only four-legged vertebrates able to regenerate tissues as diverse as skeleton, nervous system and internal organs. We de-construct the regeneration process in vivo using top-down methods such as -omics tools, genetics, and live imaging. Reciprocally, we construct tissues from the ground up by engineering the regenerative principles that we discover into cells in vitro. Uncovering regenerative principles in the axolotl could help identify and overcome roadblocks to regeneration in humans. Illuminating regeneration To identify cells important for regeneration, we make use of genetic reporters that light up specific groups of cells in the living tissue. This illumination allows us to track cells under the microscope and determine their contributions to the regenerated tissue in time and space. We can selectively profile the illuminated cells to identify the genes that they express and the mechanisms that support their functions. A genetic reporter that illuminates the expression of a pro-regeneration gene (Shh) during axolotl limb regeneration. Modified from Otsuki et al. 2025. Decoding regeneration We use -omics approaches to decode the gene regulation mechanisms that underlie regeneration. Targeting these mechanisms can allow us to control and reprogram the functions of regenerative cells. For example, we recently discovered that a transcription factor called Hand2 is responsible for ‘little finger-side’ (posterior) identity in the axolotl limb. We found that treating ‘thumb-side’ (anterior) cells with a molecule called Shh forced them to switch on Hand2 and switch over to a posterior identity, thereby changing their functions during regeneration. Left: Gene profiling reveals differences between anterior and posterior axolotl limb cells. Right: We reprogrammed anterior cells towards a posterior identity by transplanting them close to a source of Shh signal. The principal component analysis (PCA) plot shows that anterior cells transplanted posteriorly (A>P) more closely resemble posterior cells (P) than anterior cells (A) in their gene expression signatures. Modified from Otsuki et al. 2025. Using regenerative principles to build tissues in vitro The lessons that we learn from studying regeneration in vivo can act as stepping stones towards building tissues in vitro. We are creating 3D assemblies of axolotl cells – called spheroids – that serve as a platform to explore the potential of regenerative cells for tissue engineering. Fusion of anterior (red) and posterior (cyan) axolotl limb spheroids to form ‘assembloids’. Credit: Sarah Plattner. All research is conducted in accordance with national and EU ethical regulations, with a commitment to welfare and the 3Rs principles.
