Regeneration: Signaling superhighways

Neuronal activation in the axolotl brain promotes tail regeneration

The axolotl retains a remarkable capacity for regenerative repair and is one of the few vertebrate species capable of regenerating its brain and spinal cord after injury. To date, studies investigating axolotl spinal cord regeneration have placed particular emphasis on understanding how cells immediately adjacent to the injury site respond to damage to promote regenerative repair. How neurons outside of this immediate injury site respond to an injury remains unknown. Here, we identify a population of dpErk+/etv1+ glutamatergic neurons in the axolotl telencephalon that are activated in response to injury and are essential for tail regeneration. Furthermore, these neurons project to the hypothalamus where they upregulate the neuropeptide neurotensin in response to injury. Together, these findings identify a unique population of neurons in the axolotl brain whose activation is necessary for successful tail regeneration, and sheds light on how neurons outside of the immediate injury site respond to an injury.

LiverZap: a chemoptogenetic tool for global and locally restricted hepatocyte ablation to study cellular behaviours in liver regeneration

The liver restores its mass and architecture after injury. Yet, investigating morphogenetic cell behaviours and signals that repair tissue architecture at high spatiotemporal resolution remains challenging. We developed LiverZap, a tuneable chemoptogenetic liver injury model in zebrafish. LiverZap employs the formation of a binary FAP-TAP photosensitiser followed by brief near-infrared illumination inducing hepatocyte-specific death and recapitulating mammalian liver injury types. The tool enables local hepatocyte ablation and extended live imaging capturing regenerative cell behaviours, which is crucial for studying cellular interactions at the interface of healthy and damaged tissue. Applying LiverZap, we show that targeted hepatocyte ablation in a small region of interest is sufficient to trigger local liver progenitor-like cell (LPC)-mediated regeneration, challenging the current understanding of liver regeneration. Surprisingly, the LPC response is also elicited in adjacent uninjured tissue, at up to 100 µm distance to the injury. Moreover, dynamic biliary network rearrangement suggests active cell movements from uninjured tissue in response to substantial hepatocyte loss as an integral step of LPC-mediated liver regeneration. This precisely targetable liver cell ablation tool will enable the discovery of key molecular and morphogenetic regeneration paradigms.