Da Silva-Álvarez S et al. (2020), Developmentally-programmed cellular senescence ...

XB-ART-57404

Aging (Albany NY) 2020 Sep 29;1218:17895-17901. doi: 10.18632/aging.103968.

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Developmentally-programmed cellular senescence is conserved and widespread in zebrafish.

Da Silva-Álvarez S , Guerra-Varela J , Sobrido-Cameán D , Quelle A , Barreiro-Iglesias A , Sánchez L , Collado M .

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Cellular senescence is considered a stress response imposing a stable cell cycle arrest to restrict the growth of damaged cells. More recently however, cellular senescence was identified during mouse embryo development at particular structures during specific periods of time. This programmed cell senescence has been proposed to serve developmental and morphogenetic functions and to potentially represent an evolutionary origin of senescence. Cellular senescence has also been described to take place during bird (chick and quail) and amphibian (xenopus and axoltl) development. Fish however, have been described to show a very narrow and restricted pattern of developmental cell senescence. Here we carried out a detailed characterization of senescence during zebrafish development and found it to be conserved and widespread. Apart from yolk and cloaca, previously described structures, we also identified senescence in the developing central nervous system, intestine, liver, pronephric ducts, and crystalline. Interestingly, senescence at these developing structures disappeared upon treatment with senolytic compound ABT-263, supporting their senescent identity and opening the possibility of studying the contribution of this process to development. In summary, our findings extend the description of developmentally-programmed cell senescence to lower vertebrates contributing to the notion of the relevance of this process for embryo development.

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Genes referenced: cdkn1a rps11

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	Figure 1. Photomicrographs of whole-mounted developing zebrafish showing the presence of SA–β–gal staining. Representative images of 2, 3, 4, 5, 6, 7 and 11 dpf zebrafish are shown. The asterisks indicate the presence of intense SA–β–gal staining in the yolk. Thin arrows indicate the presence of intense SA–β–gal staining in the caudal (cloacal) end of the intestine. Thick black arrows indicate the presence of SA–β–gal staining in the brain. Thick empty arrows indicate the presence of SA–β–gal staining in the spinal cord. Arrowheads indicate the presence of SA–β–gal staining in the liver. Circles indicate the presence of SA–β–gal staining in the oesophagus. Scale bar: 200 μm. Images are a composition of different pictures taken under the microscope overlapped together and modified using the same parameters.
	Figure 2. Photomicrographs of transverse sections of developing zebrafish showing the presence of SA–β–gal staining in different organs. (A) Photomicrographs showing the presence of SA–β–gal staining in the rostral part of the intestine. (B) Photomicrographs showing the presence of SA–β–gal staining in the spinal cord. (C) Photomicrographs showing the presence of strong SA–β–gal staining in the outer layer of the crystalline and weak SA–β–gal staining in the brain. (D) Photomicrographs showing the presence of SA–β–gal staining in the liver. Note that the intensity of staining in the liver is weaker in 2 dpf animals. (E) Photomicrographs showing the presence of SA–β–gal staining in the pronephric ducts. Note that the intensity of staining in the pronephric duct is weaker in 2 dpf animals. Dorsal is to the top in all sections. Abbreviations: B: brain, C: crystalline, I: intestine, N: notochord, L: liver, PD: pronephric ducts, R: retina, Y: yolk. Scale bars: 50 μm.
	Figure 3. (A) Photomicrographs of whole-mounted developing zebrafish (5 dpf) stained for SA–β–gal in the absence (upper panels) or presence (lower panels) of senolytic compound ABT-263 for 24 h. Right panels show an amplified area showing a detail of positive structures. Scale bars: 50 μm. P: pronephric ducts; L: liver; I: intestine; Y: yolk. (B) Expression levels by QPCR of cdkn1a (left panel) and cdkn2ab (right panel) genes at 2 and 7 dpf relative to the housekeeping gene rps11. (C) Expression levels by QPCR of cdkn1a (left panel) and cdkn2ab (right panel) genes relative to the housekeeping gene rps11 at 4 dpf after treatment with ABT-263 or vehicle (VEH) for 48 h. Data in (B) and (C) correspond to the average ± s.d. Statistical significance was assessed by the two-tailed Student’ s t-test: * p < 0.001; p < 0.01. Samples were assessed in triplicates of pools of 30 larvae.

References [+] :

Chang, Clearance of senescent cells by ABT263 rejuvenates aged hematopoietic stem cells in mice. 2016, Pubmed