Project description:Bone regeneration is a highly efficient process allowing scarless healing after injury. Yet, musculoskeletal traumatic injury, when fracture is combined with adjacent muscle injury, alters bone healing leading to fibrous nonunion. The periosteum, the outer layer of bones, is a critical source of skeletal stem/progenitor cells (SSPCs), as well as immune, endothelial and neural cells during bone repair. We generated single nuclei datasets from the injured perioteum and hematoma at day 1-post fracture and from the hematoma/callus at day 5 post-musculoskeletal traumatic injury. These datasets were analyzed in combination with datasets from GSE234451.
Project description:Bone regeneration is a highly efficient process allowing scarless healing after injury. The periosteum, the outer layer of bones, is a critical source of skeletal stem/progenitor cells (SSPCs), as well as immune, endothelial and neural cells during bone repair. In our study, we generated a single-nuclei atlas of the murine periosteal response to bone fracture. We generated single nuclei datasets from uninjured periosteum and from injured periosteum and hematoma/fracture callus at days 5 and 7 post-injury from wild-type mice.
Project description:It is commonly observed that patients with bone fracture concomitated with traumatic brain injury (TBI) had significantly increased fracture healing while the underlying mechanisms were not fully revealed. Long non-coding RNAs (lncRNAs) were known for paly complicated roles in bone homeostasis while its role in TBI accelerated fracture were rarely reported. The present study was designed to determine the role of lncRNAs in TBI accelerated fracture via transcriptome sequencing and further bioinformatical analysis. Blood samples from 3 fracture only patients, 3 fracture concomitated with TIB patients and 3 healthy controls were harvested and were subsequently subjected to transcriptome lncRNAs sequencing. Differentially expression genes were identified, and pathway enrichment were performed by Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyze. High high-dimensional data portraying by self-organizing map (SOM) machine learning was applied to further interpret the data. A xCell method were then used to predict cellular behavior in all samples based on gene expression profiles and a lncRNA-cell interaction network were generated. A total of 874 differentially expressed genes were identified, of which about 26% were lncRNAs. Those identified lncRNAs were mainly enriched on traumatic brain injury related- and damage repair related-pathways. SOM analyzes revealed that those differentially expressed lncRNAs could be divided into three major module implications and were mainly enriched on transcriptional regulation and immune related signal pathways, which promote us to further explore cellular behaviors based on differentially expressed lncRNAs. We have predicted that basophils, CD8+ T effector memory cells, B cells, and naïve B cells were significantly down-regulated while microvascular endothelia cells were predicated significantly up-regulated with TBI/Fr group was the lowest or highest, respectively. ENSG00000278905, ENSG00000240980, ENSG00000255670, and ENSG00000196634 were the most differentially expression lcnRNA that related to all changes of cellular behavior. The present study has revealed for the first time that several critical lncRNAs may participate in TBI accelerated fracture potentially via regulating cellular behaviors of basophils, cytotoxic T cells, B cells and endothelia cells.
Project description:Traumatic brain injury (TBI) accelerates fracture healing, but the underlying mechanism remains largely unknown. Accumulating evidence indicates that the central nervous system plays a pivotal role in regulating immune system and skeleton, however, the impact of TBI on hematopoiesis commitment was overlooked. Here, we found that the dramatically elevated sympathetic tone accompanied with TBI-accelerated fracture healing; chemical sympathectomy blocks TBI-induced fracture healing. Importantly, the adrenergic hypersensitivity swiftly skews bone marrow hematopoietic lineage cells toward anti-inflammation myeloid cells within 14 days, which favor fracture healing. Knockout of β3- or β2-adrenergic receptors (ARs) eliminate TBI mediated anti-inflammation macrophage expansion and TBI-accelerated fracture healing. Moreover, β3- and β2-ARs agonists synergistically promote M2 macrophages infiltration in callus and accelerate bone healing process. Our results suggest that TBI shapes the anti-inflammation environment during early stage of fracture healing, implicating the sympathetic nerve system as a potential target that can be exploited to treat fracture.
Project description:Fracture healing is a process that involves many cell populations. In this study we characterized gene expression in a subset of cells involved in fracture healing. αSMACreERT2 mice crossed with Ai9 reporter mice that express tdTomato fluorescent protein after Cre-mediated activation were used as an experimental model. αSMA-expressing cells were labeled by tamoxifen administration, then periosteal cells from the tibia were isolated two days later (controls), or tibial fractures were performed and periosteum/soft callus tissue was collected after 2 and 6 days. The tdTomato positive cell population was isolated by flow cytometry, and subjected to microarray analysis. Histology and cell surface marker analysis indicates that αSMACreERT2 labels a mainly mesenchymal population in the periosteum that expands after fracture, and contributes to both osteogenic and chondrogenic elements of the fracture callus. We were therefore able to examine gene expression in a defined population during the early stages of fracture healing. Total RNA was obtained from the tomato positive cells within the periosteal compartment of fractures from αSMACreERT2/Ai9 mice. Control animals were given 2 doses of tamoxifen, and periosteum was collected and labeled cells sorted (8-9 sex-matched mice per group). Fractures were performed after the second dose of tamoxifen, and tomato positive cells from periosteum/callus tissue were isolated 2 and 6 days after fracture (4-8 animals per sample pooled). 3 replicates for each sample are included.
Project description:Congenital pseudarthrosis of the tibia (CPT) is a severe pediatric disorder affecting children. CPT is characterized by tibial bowing at birth leading to spontaneous fracture and fibrous non-union. Our study showed the presence of biallelic inactivation of the NF1 gene in the periosteum and in periosteal skeletal/stem progenitor cells (pSSPCs) at the pseudarthrosis site.
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.