title: Osteoblast de- and redifferentiation are controlled by a dynamic response to retinoic acid during zebrafish fin regeneration.
abstract: Zebrafish restore amputated fins by forming tissue-specific blastema cells that coordinately regenerate the lost structures. Fin amputation triggers the synthesis of several diffusible signaling factors that are required for regeneration, raising the question of how cell lineage-specific programs are protected from regenerative crosstalk between neighboring fin tissues. During fin regeneration, osteoblasts revert from a non-cycling, mature state to a cycling, preosteoblastic state to establish a pool of progenitors within the blastema. After several rounds of proliferation, preosteoblasts redifferentiate to produce new bone. Blastema formation and proliferation are driven by the continued synthesis of retinoic acid (RA). Here, we find that osteoblast dedifferentiation and redifferentiation are inhibited by RA signaling, and we uncover how the bone regenerative program is achieved against a background of massive RA synthesis. Stump osteoblasts manage to contribute to the blastema by upregulating expression of the RA-degrading enzyme cyp26b1. Redifferentiation is controlled by a presumptive gradient of RA, in which high RA levels towards the distal tip of the blastema suppress redifferentiation. We show that this might be achieved through a mechanism involving repression of Bmp signaling and promotion of Wnt/β-catenin signaling. In turn, cyp26b1(+) fibroblast-derived blastema cells in the more proximal regenerate serve as a sink to reduce RA levels, thereby allowing differentiation of neighboring preosteoblasts. Our findings reveal a mechanism explaining how the osteoblast regenerative program is protected from adverse crosstalk with neighboring fibroblasts that advances our understanding of the regulation of bone repair by RA.
authors.affiliation: Developmental Biology, University of Bayreuth, Bayreuth 95440, Germany RTG1331, Department of Biology, University of Konstanz, Konstanz 78457, Germany.
authors.forename: Nicola
authors.initials: N
authors.lastname: Blum
authors.affiliation: Developmental Biology, University of Bayreuth, Bayreuth 95440, Germany gerrit.begemann@uni-bayreuth.de.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Begemann
mesh_terms: D058500:Animal Fins / Q000166:cytology* / Q000502:physiology*; D000818:Animals; D001857:Bone Matrix / Q000378:metabolism; D054337:Cell Dedifferentiation; D049109:Cell Proliferation; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D012038:Regeneration; D000072516:Retinoic Acid 4-Hydroxylase; D015398:Signal Transduction; D014212:Tretinoin / Q000378:metabolism*; D015854:Up-Regulation; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism
chemical_list: D029961:Zebrafish Proteins; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D000072516:Retinoic Acid 4-Hydroxylase; C502199:cyp26b1 protein, zebrafish
keywords: Bone; Caudal fin; Cyp26b1; Osteoblast; Osteoclast; R115866; Zebrafish