Live Imaging of Axolotl Digit Regeneration Reveals Spatiotemporal Choreography of Diverse Connective Tissue Progenitor Pools

TLDR

Connective tissues such as skeleton, dermis, pericytes, and fascia are key sources for regenerating the patterned skeleton in axolotl appendage regeneration, but their complexity has hindered identification of the specific cells involved, impeding mechanistic understanding of blastema formation. Using brainbow transgenic axolotls to trace cells during digit tip regeneration, the study shows that each connective tissue compartment exhibits distinct spatial and temporal patterns of proliferation, migration, and differentiation. Chondrocytes proliferate without migrating into the regenerate, whereas pericytes proliferate, migrate into the blastema, and differentiate only into pericytes, periskeletal cells and fibroblasts dominate the blastema adopting diverse fates through successive migration waves, and platelet‑derived growth factor signaling drives fibroblast.

Abstract

Connective tissues—skeleton, dermis, pericytes, fascia—are a key cell source for regenerating the patterned skeleton during axolotl appendage regeneration. This complexity has made it difficult to identify the cells that regenerate skeletal tissue. Inability to identify these cells has impeded a mechanistic understanding of blastema formation. By tracing cells during digit tip regeneration using brainbow transgenic axolotls, we show that cells from each connective tissue compartment have distinct spatial and temporal profiles of proliferation, migration, and differentiation. Chondrocytes proliferate but do not migrate into the regenerate. In contrast, pericytes proliferate, then migrate into the blastema and give rise solely to pericytes. Periskeletal cells and fibroblasts contribute the bulk of digit blastema cells and acquire diverse fates according to successive waves of migration that choreograph their proximal-distal and tissue contributions. We further show that platelet-derived growth factor signaling is a potent inducer of fibroblast migration, which is required to form the blastema.