Dataset Information

FGFR3 in Periosteal Cells Drives Cartilage-to-Bone Transformation in Bone Repair.

ABSTRACT: Most organs and tissues in the body, including bone, can repair after an injury due to the activation of endogenous adult stem/progenitor cells to replace the damaged tissue. Inherent dysfunctions of the endogenous stem/progenitor cells in skeletal repair disorders are still poorly understood. Here, we report that Fgfr3Y637C/+ over-activating mutation in Prx1-derived skeletal stem/progenitor cells leads to failure of fracture consolidation. We show that periosteal cells (PCs) carrying the Fgfr3Y637C/+ mutation can engage in osteogenic and chondrogenic lineages, but following transplantation do not undergo terminal chondrocyte hypertrophy and transformation into bone causing pseudarthrosis. Instead, Prx1Cre;Fgfr3Y637C/+ PCs give rise to fibrocartilage and fibrosis. Conversely, wild-type PCs transplanted at the fracture site of Prx1Cre;Fgfr3Y637C/+ mice allow hypertrophic cartilage transition to bone and permit fracture consolidation. The results thus highlight cartilage-to-bone transformation as a necessary step for bone repair and FGFR3 signaling within PCs as a key regulator of this transformation.

SUBMITTER: Julien A

PROVIDER: S-EPMC7561512 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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FGFR3 in Periosteal Cells Drives Cartilage-to-Bone Transformation in Bone Repair.

Julien Anais A Perrin Simon S Duchamp de Lageneste Oriane O Carvalho Caroline C Bensidhoum Morad M Legeai-Mallet Laurence L Colnot Céline C

Stem cell reports 20200910 4

Most organs and tissues in the body, including bone, can repair after an injury due to the activation of endogenous adult stem/progenitor cells to replace the damaged tissue. Inherent dysfunctions of the endogenous stem/progenitor cells in skeletal repair disorders are still poorly understood. Here, we report that Fgfr3<sup>Y637C/+</sup> over-activating mutation in Prx1-derived skeletal stem/progenitor cells leads to failure of fracture consolidation. We show that periosteal cells (PCs) carrying ...[more]

PMID: 32916123

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Project description:IntroductionThe phases of fracture healing have been well characterized. However, the exact source and genetic profile of the skeletal progenitors that participate in bone repair is somewhat unclear. Sox9 expression in skeletal elements precedes bone and cartilage formation and a Sox9+ cell type is retained in the adult periosteum. We hypothesized that Sox9+ periosteal cells are multipotent skeletal progenitors normally participating in fracture repair.MethodsTo test this hypothesis we used tamoxifen (TM)-mediated lineage tracing of Sox9+ cells in Sox9CreErt2:Td-Tomato mice. Intact femora were analyzed with immunostaining and RNA sequencing to evaluate the skeletal distribution and gene expression profile of Td-Tomato positive, Sox9-descendent cells in the adult femur. To assess the role of Td-tomato+cells in the fracture healing process, mice underwent a closed mid-diaphyseal femoral fracture. Fractured hind limbs were analyzed by X-ray, histology and immuno-staining at 3, 9 or 56days post-fracture.ResultsIn the intact adult mouse femur, Td-Tomato-labeled cells were observed in the primary spongiosa, periosteum and endosteum. RNA sequencing showed that Td-Tomato positive periosteal cells were co-enriched for Sox9 transcripts, and mRNAs for osteoblast and chondrocyte specific genes. In a femoral fracture model, we showed that pre-labeled Td-Tomato positive descendent cells were mobilized during the early stages of bone repair (day 3 post-op) contributing to the fracture repair process by differentiating into chondrocytes, osteoblasts and osteocytes.ConclusionA Sox9+ skeletal progenitor population resides in the adult periosteum. Fate tracing studies show that descendants of the Sox9+ periosteal progenitors give rise to chondrocytes, osteoblasts and mature cortical osteocytes in repair of the fractured femur. To our knowledge this is the first report of a reparative Sox9+ progenitor population in the periosteum of the adult long bone. Taken together with developmental studies, our data suggest a broad role for Sox9+ osteochondroprogenitors in development and repair of the mammalian skeleton.

Project description:The phases of fracture healing have been well characterized. However, the exact source and genetic profile of the skeletal progenitors that participate in bone repair is somewhat unclear. Sox9 expression in skeletal elements precedes bone and cartilage formation and a Sox9+ cell type is retained in the adult periosteum. We hypothesized that Sox9+ periosteal cells are multipotent skeletal progenitors normally participating in fracture repair. To test this hypothesis we used tamoxifen (TM)-mediated lineage tracing of Sox9+ cells in Sox9CreErt2:Td-Tomato mice. TM injection indelibly labels Sox9+ cells and all their descendants with the fluorescent reporter protein Td-Tomato. Intact mouse femora were harvested 2 weeks after TM injection and analyzed by histology and immunostaining and RNA sequencing, to evaluate the skeletal distribution and gene expression profile of Td-Tomato positive cells in the adult femur. To assess the role of these cells in fracture repair, mice underwent a closed mid-diaphyseal femoral fracture and their hind limbs were harvested at 3, 9 or 56 days post-fracture to assess the contribution of Sox9+ and Td-tomato+ cells in the fracture healing process. In the intact adult mouse femur, Td-Tomato-labelled cells were observed in articular and growth plate cartilage where Sox9 is known to be expressed, but also in the primary spongiosa, periosteum, and endosteum. RNA sequencing and subsequent analysis showed that Td-Tomato positive periosteal cells were enriched in Sox9 transcripts, and transcripts for various osteogenic and chondrocyte specific genes. In a femoral fracture model, we showed that pre-labeled Td-Tomato positive descendent cells were mobilized during the fracture repair process, expanding and migrating towards the fracture site 3 days post-fracture. Here, Td-Tomato positive cells differentiate into chondrocytes and osteoblasts in the soft and hard callus, respectively, 9 days post-fracture. By 2 months post-fracture, descendants of the original Sox9 labelled cell population were prevalent in the cortex and periosteum, and amongst the differentiated osteocyte population embedded within the cortical bone. Thus, a Sox9+ progenitor population resides in the adult periosteum. Fate tracing shows that these cells likely play a substantial role in repair of the fractured femur giving rise to chondrocytes, osteoblasts and mature cortical osteocytes. To our knowledge this is the first report of this Sox9+ cell population in the periosteum of the adult long bone. Taken together with developmental studies on skeletal formation, our data suggest that Sox9+ osteochondroprogenitors play a continuous role in skeletal formation throughout life.

Dataset Information

FGFR3 in Periosteal Cells Drives Cartilage-to-Bone Transformation in Bone Repair.

Publications

FGFR3 in Periosteal Cells Drives Cartilage-to-Bone Transformation in Bone Repair.

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