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In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone.

ABSTRACT: Osteoblasts are matrix-depositing cells that can divide and heal bone injuries. Their deep-tissue location and the slow progression of bone regeneration challenge attempts to capture osteoblast behaviors in live tissue at high spatiotemporal resolution. Here, we have developed an imaging platform to monitor and quantify individual and collective behaviors of osteoblasts in adult zebrafish scales, skeletal body armor discs that regenerate rapidly after loss. Using a panel of transgenic lines that visualize and manipulate osteoblasts, we find that a founder pool of osteoblasts emerges through de novo differentiation within one day of scale plucking. These osteoblasts undergo division events that are largely uniform in frequency and orientation to establish a primordium. Osteoblast proliferation dynamics diversify across the primordium by two days after injury, with cell divisions focused near, and with orientations parallel to, the scale periphery, occurring coincident with dynamic localization of fgf20a gene expression. In posterior scale regions, cell elongation events initiate in areas soon occupied by mineralized grooves called radii, beginning approximately 2 days post injury, with patterned osteoblast death events accompanying maturation of these radii. By imaging at single-cell resolution, we detail acquisition of spatiotemporally distinct cell division, motility, and death dynamics within a founder osteoblast pool as bone regenerates.

SUBMITTER: Cox BD

PROVIDER: S-EPMC6298855 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone.

Cox Ben D BD De Simone Alessandro A Tornini Valerie A VA Singh Sumeet P SP Di Talia Stefano S Poss Kenneth D KD

Current biology : CB 20181129 24

Osteoblasts are matrix-depositing cells that can divide and heal bone injuries. Their deep-tissue location and the slow progression of bone regeneration challenge attempts to capture osteoblast behaviors in live tissue at high spatiotemporal resolution. Here, we have developed an imaging platform to monitor and quantify individual and collective behaviors of osteoblasts in adult zebrafish scales, skeletal body armor discs that regenerate rapidly after loss. Using a panel of transgenic lines that ...[more]

PMID: 30503623

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Project description:Wnt signaling executes an indispensable performance in osteoblast differentiation, bone development, homeostasis, and remodeling. Wnt signals trigger the intracellular Wnt signaling cascade to initiate regulating the implication of β-catenin in the bone environment. Going through the novel discoveries done via high-throughput sequencing technologies on genetic mouse models, we highlighted the significant contribution of Wnt ligands, co-receptors, inhibitors, their related skeletal phenotypes in mouse models and the similar bone disorders clinically observed in human beings. Moreover, the crosstalk between Wnt signaling pathway and BMP, TGF-β, FGF, Hippo, Hedgehog, Notch and PDGF signaling pathways is thoroughly demonstrated to be the underlying gene regulatory network that orchestrates osteoblast differentiation and bone development. We also introspected the significance of Wnt signaling transduction in the reorganization of cellular metabolism by stimulating glycolysis, glutamine catabolism, and fatty acid oxidation in osteoblast-lineage cells that display an important regulatory arbor in the cellular bioenergetics of the bone. Throughout this evaluation, most to date therapeutical approaches towards osteoporosis and other bone maladies found in human beings, are formulated with an aspiration to holistically revamp the present clinical applications involving various monoclonal antibodies therapies that lack specificity, efficacy, and safety into more requisite advanced therapeutics that satisfy these three requirements for further clinical considerations. Conclusively, our review provides comprehensive scientific findings related to the fundamental significance of Wnt signaling cascades in skeletal system and the underlying gene regulatory network with other signaling pathways enlightening researchers with the possibility to further integrate the identified target molecules into therapeutic strategies for skeletal disorders treatment in the clinic.

Project description:The coupling of osteoblasts and osteocytes by connexin43 (Cx43) gap junctions permits the sharing of second messengers that coordinate bone cell function and cortical bone acquisition. However, details of how Cx43 converts shared second messengers into signals that converge onto essential osteogenic processes are incomplete. Here, we use in vitro and in vivo methods to show that Cx43 and Runx2 functionally interact to regulate osteoblast gene expression and proliferation, ultimately affecting cortical bone properties. Using compound hemizygous mice for the Gja1 (Cx43) and Runx2 genes, we observed a skeletal phenotype not visible in wild-type or singly hemizygous animals. Cortical bone analysis by micro-computed tomography (?CT) revealed that 8-week-old male, compound Gja1+/- Runx2+/- mice have a marked increase in cross-sectional area, endosteal and periosteal bone perimeter, and an increase in porosity compared to controls. These compound Gja1+/- Runx2+/- mice closely approximate the cortical bone phenotypes seen in osteoblast-specific Gja1-conditional knockout models. Furthermore, ?CT analysis of skulls revealed an altered interparietal bone geometry in compound hemizygotes. Consistent with this finding, Alizarin red/Alcian blue staining of 2-day-old Gja1+/- Runx2+/- neonates showed a hypomorphic interparietal bone, an exacerbation of the open fontanelles, and a further reduction in the hypoplastic clavicles compared to Runx2+/- neonates. Expression of osteoblast genes, including osteocalcin, osterix, periostin, and Hsp47, was markedly reduced in tibial RNA extracts from compound hemizygous mice, and osteoblasts from compound hemizygous mice exhibited increased proliferative capacity. Further, the reduced osteocalcin expression and hyperproliferative nature of osteoblasts from Cx43 deficient mice was rescued by Runx2 expression. In summary, these findings provide evidence that Cx43 and Runx2 functionally intersect in vivo to regulate cortical bone properties and affect osteoblast differentiation and proliferation, and likely contributes to aspects of the skeletal phenotype of Cx43 conditional knockout mice. © 2017 American Society for Bone and Mineral Research.

Dataset Information

In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone.

Publications

In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone.

Similar Datasets

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