The transcriptional cofactor Lbh regulates angiogenesis and endochondral bone formation during fetal bone development.
Ontology highlight
ABSTRACT:
SUBMITTER: Conen KL
PROVIDER: S-EPMC2760734 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:To investigate the effect of the maternal gut microbiome on fetal endochondral bone formation, fetuses at embryonic day 18 were obtained from germ-free (GF) and specific-pathogen-free (SPF) pregnant mothers. Skeletal preparation of the fetuses' whole bodies did not show significant morphological alterations; however, micro-CT analysis of the tibiae showed a lower bone volume fraction in the SPF tibia. Primary cultured chondrocytes from fetal SPF rib cages showed a lower cell proliferation and lower accumulation of the extracellular matrix. RNA-sequencing analysis showed the induction of inflammation-associated genes such as the interleukin (IL) 17 receptor, IL 6, and immune-response genes in SPF chondrocytes. These data indicate that the maternal gut microbiome in SPF mice affects fetal embryonic endochondral ossification, possibly by changing the expression of genes related to inflammation and the immune response in fetal cartilage. The gut microbiome may modify endochondral ossification in the fetal chondrocytes passing through the placenta.
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Project description:Skeletal development is regulated by the coordinated activity of signaling molecules that are both produced locally by cartilage and bone cells and also circulate systemically. During embryonic development and postnatal bone remodeling, receptor tyrosine kinase (RTK) superfamily members play critical roles in the proliferation, survival, and differentiation of chondrocytes, osteoblasts, osteoclasts, and other bone cells. Recently, several molecules that regulate RTK signaling have been identified, including the four members of the Sprouty (Spry) family (Spry1-4). We report that Spry2 plays an important role in regulation of endochondral bone formation. Mice in which the Spry2 gene has been deleted have defective chondrogenesis and endochondral bone formation, with a postnatal decrease in skeletal size and trabecular bone mass. In these constitutive Spry2 mutants, both chondrocytes and osteoblasts undergo increased cell proliferation and impaired terminal differentiation. Tissue-specific Spry2 deletion by either osteoblast- (Col1-Cre) or chondrocyte- (Col2-Cre) specific drivers led to decreased relative bone mass, demonstrating the critical role of Spry2 in both cell types. Molecular analyses of signaling pathways in Spry2(-/-) mice revealed an unexpected upregulation of BMP signaling and decrease in RTK signaling. These results identify Spry2 as a critical regulator of endochondral bone formation that modulates signaling in both osteoblast and chondrocyte lineages.
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Project description:P63, a member of the P53 tumor suppressor family, is known to play important functions in cancer and development. Interestingly, previous studies have shown that p63 null mice are absent or have truncated limbs, while mutations in human P63 cause several skeletal syndromes that also show limb and digit abnormalities, suggesting its essential role in long bone development. Indeed, we detected increased level of p63 transcript in hypertrophic MCT cells (an established cell model of chondrocyte maturation) than in proliferative MCT cells. To investigate the in vivo role of P63 upon endochondral bone formation, we have established transgenic mouse lines in which HA- and Flag-tagged TAP63? (the longest P63 isoform) is driven by the hypertrophic chondrocyte-specific Col10a1 regulatory elements. Skeletal staining of Col10a1-TAP63? transgenic mice at either embryonic day 17.5 (E17.5) or postnatal day 1 (P1) observed accelerated ossification in long bone, digit and tail bones compared to their wild-type littermates, suggesting a putative function of P63 during skeletal development. We also detected decreased level of Sox9 and Bcl-2 transcripts, while Alp and Ank are slightly upregulated in Col10a1-TAP63? transgenic mouse limbs. Further immunohistochemical analysis confirmed the decreased Sox9 expression in the proliferative and hypertrophic zone of these mice. Von Kossa staining suggests increased mineralization in hypertrophic zone of transgenic mice compared to littermate controls. Together, our results suggest a role of TAP63? upon skeletal development. TAP63a may promote endochondral ossification through interaction with genes relevant to matrix mineralization and chondrocyte maturation or apoptosis.
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Project description:MicroRNAs (miRNAs) play critical roles in a variety of biological processes in diverse organisms, including mammals. In the mouse skeletal system, a global reduction of miRNAs in chondrocytes causes a lethal skeletal dysplasia. However, little is known about the physiological roles of individual miRNAs in chondrocytes. The miRNA-encoding gene, Mir140, is evolutionarily conserved among vertebrates and is abundantly and almost exclusively expressed in chondrocytes. In this paper, we show that loss of Mir140 in mice causes growth defects of endochondral bones, resulting in dwarfism and craniofacial deformities. Endochondral bone development is mildly advanced due to accelerated hypertrophic differentiation of chondrocytes in Mir140-null mice. Comparison of profiles of RNA associated with Argonaute 2 (Ago2) between wild-type and Mir140-null chondrocytes identified Dnpep as a Mir140 target. As expected, Dnpep expression was increased in Mir140-null chondrocytes. Dnpep overexpression showed a mild antagonistic effect on bone morphogenetic protein (BMP) signaling at a position downstream of Smad activation. Mir140-null chondrocytes showed lower-than-normal basal BMP signaling, which was reversed by Dnpep knockdown. These results demonstrate that Mir140 is essential for normal endochondral bone development and suggest that the reduced BMP signaling caused by Dnpep upregulation plays a causal role in the skeletal defects of Mir140-null mice.
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Project description:BackgroundCholine kinase has three isoforms encoded by the genes Chka and Chkb. Inactivation of Chka in mice results in embryonic lethality, whereas Chkb(-/-) mice display neonatal forelimb bone deformations.MethodsTo understand the mechanisms underlying the bone deformations, we compared the biology and biochemistry of bone formation from embryonic to young adult wild-type (WT) and Chkb(-/-) mice.ResultsThe deformations are specific to the radius and ulna during the late embryonic stage. The radius and ulna of Chkb(-/-) mice display expanded hypertrophic zones, unorganized proliferative columns in their growth plates, and delayed formation of primary ossification centers. The differentiation of chondrocytes of Chkb(-/-) mice was impaired, as was chondrocyte proliferation and expression of matrix metalloproteinases 9 and 13. In chondrocytes from Chkb(-/-) mice, phosphatidylcholine was slightly lower than in WT mice whereas the amount of phosphocholine was decreased by approximately 75%. In addition, the radius and ulna from Chkb(-/-) mice contained fewer osteoclasts along the cartilage/bone interface.ConclusionsChkb has a critical role in the normal embryogenic formation of the radius and ulna in mice.General significanceOur data indicate that choline kinase beta plays an important role in endochondral bone formation by modulating growth plate physiology.
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Project description:C1q/TNF-related protein 3 (CTRP3) is a cytokine known to regulate a variety of metabolic processes. Though previously undescribed in the context of bone regeneration, high throughput gene expression experiments in mice identified CTRP3 as one of the most highly upregulated genes in fracture callus tissue. Hypothesizing a positive regulatory role for CTRP3 in bone regeneration, we phenotyped skeletal development and fracture healing in CTRP3 knockout (KO) and CTRP3 overexpressing transgenic (TG) mice relative to wild-type (WT) control animals. CTRP3 KO mice experienced delayed endochondral fracture healing, resulting in abnormal mineral distribution, the presence of periosteal marrow compartments, and a nonunion-like state. Decreased osteoclast number was also observed in CTRP3 KO mice, whereas CTRP3 TG mice underwent accelerated callus remodeling. Gene expression profiling revealed a broad impact on osteoblast/osteoclast lineage commitment and metabolism, including arrested progression toward mature skeletal lineages in the KO group. A single systemic injection of CTRP3 protein at the time of fracture was insufficient to phenocopy the chronic TG healing response in WT mice. By associating CTRP3 levels with fracture healing progression, these data identify a novel protein family with potential therapeutic and diagnostic value. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:00-19966, 2020.
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Project description:Chondrocytes in the epiphyseal cartilage undergo terminal differentiation prior to their removal through apoptosis. To examine the role of ERK1 and ERK2 in chondrocyte terminal differentiation, we generated Osterix (Osx)-Cre; ERK1(-/-) ; ERK2(flox/flox) mice (conditional knockout Osx [cKOosx]), in which ERK1 and ERK2 were deleted in hypertrophic chondrocytes. These cKOosx mice were grossly normal in size at birth, but by 3 weeks of age exhibited shorter long bones. Histological analysis in these mice revealed that the zone of hypertrophic chondrocytes in the growth plate was markedly expanded. In situ hybridization and quantitative real-time PCR analyses demonstrated that Matrix metalloproteinase-13 (Mmp13) and Osteopontin expression was significantly decreased, indicating impaired chondrocyte terminal differentiation. Moreover, Egr1 and Egr2, transcription factors whose expression is restricted to the last layers of hypertrophic chondrocytes in wild-type mice, were also strongly downregulated in these cKOosx mice. In transient transfection experiments in the RCS rat chondrosarcoma cell line, the expression of Egr1, Egr2, or a constitutively active mutant of MEK1 increased the activity of an Osteopontin promoter, whereas the MEK1-induced activation of the Osteopontin promoter was inhibited by the coexpression of Nab2, an Egr1 and Egr2 co-repressor. These results suggest that MEK1-ERK signaling activates the Osteopontin promoter in part through Egr1 and Egr2. Finally, our histological analysis of cKOosx mice demonstrated enchondroma-like lesions in the bone marrow that are reminiscent of human metachondromatosis, a skeletal disorder caused by mutations in PTPN11. Our observations suggest that the development of enchondromas in metachondromatosis may be caused by reduced extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK MAPK) signaling.
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