Cell senescence contributes to tissue regeneration in zebrafish

Abstract

Cellular senescence is a stress response that limits the proliferation of damaged cells by establishing a permanent cell cycle arrest. Different stimuli can trigger senescence but excessive production or impaired clearance of these cells can lead to their accumulation during aging with deleterious effects. Despite this potential negative side of cell senescence, its physiological role as a pro-regenerative and morphogenetic force has emerged recently after the identification of programmed cell senescence during embryogenesis and during wound healing and limb regeneration. Here, we explored the conservation of tissue injury-induced senescence in a model of complex regeneration, the zebrafish. Fin amputation in adult fish led to the appearance of senescent cells at the site of damage, and their removal impaired tissue regeneration. Despite many conceptual similarities, this tissue repair response is different from developmental senescence. Our results lend support to the notion that cell senescence is a positive response promoting tissue repair and homeostasis.

Keywords: cellular senescence; regeneration; tissue injury; zebrafish.

Figure 1

Pectoral fin amputation induces features of cell senescence. (a) Schematic representation of the fin amputation system used throughout the study. (b) Representative photomicrographs of fins stained for SAbetaGal or phospho‐histone 3 (P‐H3, right panel) after amputations (NA: nonamputated; 8, 16, and 30 dpa: days postamputation). Co‐staining of P‐H3 was done at 8 dpa. Arrowhead shows the amputation plane. (c) Schematic representation showing the different types of samples used in the study (NA: nonamputated; A: amputated; DIS: distal area; PROX: proximal). (d) SAbetaGal activity measured using Galacton substrate after 8, 16, and 30 days postamputation (dpa) (from 5–10 animals per condition). (e) Expression levels by QPCR of cdkn1a (left panel) and cdkn2ab (right panel) genes relative to the housekeeping gene rps11 after 8, 16, and 30 days postamputation (dpa). Results are presented as mean ± SD ***p < .001, **p < .01,*p < .05, n.s. nonsignificant

Figure 2

Removal of senescent cells impairs fin regeneration. (a) Schematic representation of the experimental strategy followed to analyze the effect of removing senescent cells from amputated fins after incubation with ABT‐263 for 48 or 72 hr, or treated with vehicle (VEH). (b) SAbetaGal activity measured using Galacton substrate at 8 days postamputation and after treatment with ABT‐263 for 48 or 72 hr, or with vehicle (VEH) (from 5–10 animals per condition). (c) Expression levels by QPCR of cdkn1a (left panel) and cdkn2ab (right panel) genes relative to the housekeeping gene rps11 at 8 dpa and after treatment with ABT‐263 for 48 or 72 hr, or with vehicle (VEH). (d) Length of regenerate (%) reached by amputated fins at 8 days postamputation and after treatment with ABT‐263 relative to untreated amputated fins (five animals per group). (e) Representative photomicrographs of larval fins stained for SAbetaGal or p21, 24 hr after amputation and control fin (CTRL). Scale bars: SAbetaGAL: 200 µm; p21: 75 µm. Results are presented as mean ± SD ***p < .001, **p < .01, *p < .05, n.s. nonsignificant