RESUMO
Clonal hematopoiesis of indeterminate potential (CHIP) arises from aging-associated acquired mutations in hematopoietic progenitors, which display clonal expansion and produce phenotypically altered leukocytes. We associated CHIP-DNMT3A mutations with a higher prevalence of periodontitis and gingival inflammation among 4,946 community-dwelling adults. To model DNMT3A-driven CHIP, we used mice with the heterozygous loss-of-function mutation R878H, equivalent to the human hotspot mutation R882H. Partial transplantation with Dnmt3aR878H/+ bone marrow (BM) cells resulted in clonal expansion of mutant cells into both myeloid and lymphoid lineages and an elevated abundance of osteoclast precursors in the BM and osteoclastogenic macrophages in the periphery. DNMT3A-driven clonal hematopoiesis in recipient mice promoted naturally occurring periodontitis and aggravated experimentally induced periodontitis and arthritis, associated with enhanced osteoclastogenesis, IL-17-dependent inflammation and neutrophil responses, and impaired regulatory T cell immunosuppressive activity. DNMT3A-driven clonal hematopoiesis and, subsequently, periodontitis were suppressed by rapamycin treatment. DNMT3A-driven CHIP represents a treatable state of maladaptive hematopoiesis promoting inflammatory bone loss.
Assuntos
Hematopoiese Clonal , DNA (Citosina-5-)-Metiltransferases , DNA Metiltransferase 3A , Periodontite , Animais , DNA (Citosina-5-)-Metiltransferases/metabolismo , DNA (Citosina-5-)-Metiltransferases/genética , Camundongos , Hematopoiese Clonal/genética , Humanos , Periodontite/genética , Periodontite/patologia , Mutação , Masculino , Feminino , Inflamação/genética , Inflamação/patologia , Osteoclastos/metabolismo , Camundongos Endogâmicos C57BL , Adulto , Interleucina-17/metabolismo , Interleucina-17/genética , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/metabolismo , Hematopoese/genética , Osteogênese/genética , Células-Tronco Hematopoéticas/metabolismo , Reabsorção Óssea/genética , Reabsorção Óssea/patologia , Pessoa de Meia-IdadeRESUMO
The niche is typically considered as a pre-established structure sustaining stem cells. Therefore, the regulation of its formation remains largely unexplored. Whether distinct molecular mechanisms control the establishment versus maintenance of a stem cell niche is unknown. To address this, we compared perinatal and adult bone marrow mesenchymal stromal cells (MSCs), a key component of the hematopoietic stem cell (HSC) niche. MSCs exhibited enrichment in genes mediating m6A mRNA methylation at the perinatal stage and downregulated the expression of Mettl3, the m6A methyltransferase, shortly after birth. Deletion of Mettl3 from developing MSCs but not osteoblasts led to excessive osteogenic differentiation and a severe HSC niche formation defect, which was significantly rescued by deletion of Klf2, an m6A target. In contrast, deletion of Mettl3 from MSCs postnatally did not affect HSC niche. Stem cell niche generation and maintenance thus depend on divergent molecular mechanisms, which may be exploited for regenerative medicine.
Assuntos
Células-Tronco Hematopoéticas , Células-Tronco Mesenquimais , Metiltransferases , Camundongos Endogâmicos C57BL , Nicho de Células-Tronco , Animais , Camundongos , Adenosina/metabolismo , Adenosina/análogos & derivados , Diferenciação Celular , Epigênese Genética , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/citologia , Fatores de Transcrição Kruppel-Like , Células-Tronco Mesenquimais/metabolismo , Células-Tronco Mesenquimais/citologia , Metiltransferases/metabolismo , Metiltransferases/genética , Osteoblastos/metabolismo , Osteoblastos/citologia , Osteogênese , RNA Mensageiro/metabolismo , RNA Mensageiro/genética , Transcriptoma/genética , HumanosRESUMO
Stroma is a poorly defined non-parenchymal component of virtually every organ with key roles in organ development, homeostasis, and repair. Studies of the bone marrow stroma have defined individual populations in the stem cell niche regulating hematopoietic regeneration and capable of initiating leukemia. Here, we use single-cell RNA sequencing (scRNA-seq) to define a cellular taxonomy of the mouse bone marrow stroma and its perturbation by malignancy. We identified seventeen stromal subsets expressing distinct hematopoietic regulatory genes spanning new fibroblastic and osteoblastic subpopulations including distinct osteoblast differentiation trajectories. Emerging acute myeloid leukemia impaired mesenchymal osteogenic differentiation and reduced regulatory molecules necessary for normal hematopoiesis. These data suggest that tissue stroma responds to malignant cells by disadvantaging normal parenchymal cells. Our taxonomy of the stromal compartment provides a comprehensive bone marrow cell census and experimental support for cancer cell crosstalk with specific stromal elements to impair normal tissue function and thereby enable emergent cancer.
Assuntos
Células da Medula Óssea/metabolismo , Diferenciação Celular , Homeostase , Leucemia Mieloide Aguda/metabolismo , Osteoblastos/metabolismo , Osteogênese , Microambiente Tumoral , Animais , Células da Medula Óssea/patologia , Humanos , Leucemia Mieloide Aguda/patologia , Camundongos , Osteoblastos/patologia , Células Estromais/metabolismo , Células Estromais/patologiaRESUMO
Osteoclasts have a unique bone-destroying capacity, playing key roles in steady-state bone remodeling and arthritic bone erosion. Whether the osteoclasts in these different tissue settings arise from the same precursor states of monocytoid cells is presently unknown. Here, we show that osteoclasts in pannus originate exclusively from circulating bone marrow-derived cells and not from locally resident macrophages. We identify murine CX3CR1hiLy6CintF4/80+I-A+/I-E+ macrophages (termed here arthritis-associated osteoclastogenic macrophages (AtoMs)) as the osteoclast precursor-containing population in the inflamed synovium, comprising a subset distinct from conventional osteoclast precursors in homeostatic bone remodeling. Tamoxifen-inducible Foxm1 deletion suppressed the capacity of AtoMs to differentiate into osteoclasts in vitro and in vivo. Furthermore, synovial samples from human patients with rheumatoid arthritis contained CX3CR1+HLA-DRhiCD11c+CD80-CD86+ cells that corresponded to mouse AtoMs, and human osteoclastogenesis was inhibited by the FoxM1 inhibitor thiostrepton, constituting a potential target for rheumatoid arthritis treatment.
Assuntos
Artrite Experimental/imunologia , Artrite Reumatoide/imunologia , Células da Medula Óssea/fisiologia , Proteína Forkhead Box M1/metabolismo , Macrófagos/fisiologia , Osteoclastos/fisiologia , Animais , Receptor 1 de Quimiocina CX3C/metabolismo , Diferenciação Celular , Células Cultivadas , Modelos Animais de Doenças , Proteína Forkhead Box M1/antagonistas & inibidores , Proteína Forkhead Box M1/genética , Humanos , Masculino , Camundongos , Camundongos Endogâmicos DBA , Camundongos Transgênicos , Osteogênese , Tioestreptona/farmacologiaRESUMO
Maintaining homeostasis of Ca(2+) stores in the endoplasmic reticulum (ER) is crucial for proper Ca(2+) signaling and key cellular functions. The Ca(2+)-release-activated Ca(2+) (CRAC) channel is responsible for Ca(2+) influx and refilling after store depletion, but how cells cope with excess Ca(2+) when ER stores are overloaded is unclear. We show that TMCO1 is an ER transmembrane protein that actively prevents Ca(2+) stores from overfilling, acting as what we term a "Ca(2+) load-activated Ca(2+) channel" or "CLAC" channel. TMCO1 undergoes reversible homotetramerization in response to ER Ca(2+) overloading and disassembly upon Ca(2+) depletion and forms a Ca(2+)-selective ion channel on giant liposomes. TMCO1 knockout mice reproduce the main clinical features of human cerebrofaciothoracic (CFT) dysplasia spectrum, a developmental disorder linked to TMCO1 dysfunction, and exhibit severe mishandling of ER Ca(2+) in cells. Our findings indicate that TMCO1 provides a protective mechanism to prevent overfilling of ER stores with Ca(2+) ions.
Assuntos
Canais de Cálcio/metabolismo , Retículo Endoplasmático/metabolismo , Sequência de Aminoácidos , Animais , Ataxia/genética , Células COS , Cálcio/metabolismo , Canais de Cálcio/genética , Chlorocebus aethiops , Células HEK293 , Células HeLa , Humanos , Deficiência Intelectual/genética , Membranas Intracelulares/metabolismo , Camundongos , Camundongos Knockout , Osteogênese/genética , Alinhamento de SequênciaRESUMO
The mechanisms by which transcription factor haploinsufficiency alters the epigenetic and transcriptional landscape in human cells to cause disease are unknown. Here, we utilized human induced pluripotent stem cell (iPSC)-derived endothelial cells (ECs) to show that heterozygous nonsense mutations in NOTCH1 that cause aortic valve calcification disrupt the epigenetic architecture, resulting in derepression of latent pro-osteogenic and -inflammatory gene networks. Hemodynamic shear stress, which protects valves from calcification in vivo, activated anti-osteogenic and anti-inflammatory networks in NOTCH1(+/+), but not NOTCH1(+/-), iPSC-derived ECs. NOTCH1 haploinsufficiency altered H3K27ac at NOTCH1-bound enhancers, dysregulating downstream transcription of more than 1,000 genes involved in osteogenesis, inflammation, and oxidative stress. Computational predictions of the disrupted NOTCH1-dependent gene network revealed regulatory nodes that, when modulated, restored the network toward the NOTCH1(+/+) state. Our results highlight how alterations in transcription factor dosage affect gene networks leading to human disease and reveal nodes for potential therapeutic intervention.
Assuntos
Epigênese Genética , Redes Reguladoras de Genes , Receptor Notch1/genética , Células Endoteliais/metabolismo , Feminino , Haploinsuficiência , Código das Histonas , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Inflamação/metabolismo , Masculino , Osteogênese , Linhagem , Receptor Notch1/metabolismo , Estresse Mecânico , Transcrição GênicaRESUMO
The synthesis of type I collagen, the main component of bone matrix, precedes the expression of Runx2, the earliest determinant of osteoblast differentiation. We hypothesized that the energetic needs of osteoblasts might explain this apparent paradox. We show here that glucose, the main nutrient of osteoblasts, is transported in these cells through Glut1, whose expression precedes that of Runx2. Glucose uptake favors osteoblast differentiation by suppressing the AMPK-dependent proteasomal degradation of Runx2 and promotes bone formation by inhibiting another function of AMPK. While RUNX2 cannot induce osteoblast differentiation when glucose uptake is compromised, raising blood glucose levels restores collagen synthesis in Runx2-null osteoblasts and initiates bone formation in Runx2-deficient embryos. Moreover, RUNX2 favors Glut1 expression, and this feedforward regulation between RUNX2 and Glut1 determines the onset of osteoblast differentiation during development and the extent of bone formation throughout life. These results reveal an unexpected intricacy between bone and glucose metabolism.
Assuntos
Diferenciação Celular , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Glucose/metabolismo , Osteoblastos/metabolismo , Osteogênese , Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Proteínas Quinases Ativadas por AMP/genética , Sequência de Aminoácidos , Animais , Embrião de Mamíferos/citologia , Embrião de Mamíferos/metabolismo , Transportador de Glucose Tipo 1/metabolismo , Homeostase , Camundongos , Osteoblastos/citologia , Alinhamento de Sequência , Crânio/citologiaRESUMO
In vitro modeling of human disease has recently become feasible with induced pluripotent stem cell (iPSC) technology. Here, we established patient-derived iPSCs from a Li-Fraumeni syndrome (LFS) family and investigated the role of mutant p53 in the development of osteosarcoma (OS). LFS iPSC-derived osteoblasts (OBs) recapitulated OS features including defective osteoblastic differentiation as well as tumorigenic ability. Systematic analyses revealed that the expression of genes enriched in LFS-derived OBs strongly correlated with decreased time to tumor recurrence and poor patient survival. Furthermore, LFS OBs exhibited impaired upregulation of the imprinted gene H19 during osteogenesis. Restoration of H19 expression in LFS OBs facilitated osteoblastic differentiation and repressed tumorigenic potential. By integrating human imprinted gene network (IGN) into functional genomic analyses, we found that H19 mediates suppression of LFS-associated OS through the IGN component DECORIN (DCN). In summary, these findings demonstrate the feasibility of studying inherited human cancer syndromes with iPSCs.
Assuntos
Redes Reguladoras de Genes , Células-Tronco Pluripotentes Induzidas/citologia , Síndrome de Li-Fraumeni/complicações , Osteossarcoma/etiologia , Adolescente , Adulto , Animais , Criança , Decorina/metabolismo , Feminino , Humanos , Síndrome de Li-Fraumeni/genética , Síndrome de Li-Fraumeni/patologia , Masculino , Células-Tronco Mesenquimais/metabolismo , Camundongos , Modelos Biológicos , Transplante de Neoplasias , Osteoblastos/citologia , Osteoblastos/metabolismo , Osteogênese , Osteossarcoma/genética , Osteossarcoma/patologia , RNA Longo não Codificante/metabolismo , Transplante Heterólogo , Proteína Supressora de Tumor p53/metabolismoRESUMO
In lactating mothers, the high calcium (Ca2+) demand for milk production triggers significant bone loss1. Although oestrogen normally counteracts excessive bone resorption by promoting bone formation, this sex steroid drops precipitously during this postpartum period. Here we report that brain-derived cellular communication network factor 3 (CCN3) secreted from KISS1 neurons of the arcuate nucleus (ARCKISS1) fills this void and functions as a potent osteoanabolic factor to build bone in lactating females. We began by showing that our previously reported female-specific, dense bone phenotype2 originates from a humoral factor that promotes bone mass and acts on skeletal stem cells to increase their frequency and osteochondrogenic potential. This circulatory factor was then identified as CCN3, a brain-derived hormone from ARCKISS1 neurons that is able to stimulate mouse and human skeletal stem cell activity, increase bone remodelling and accelerate fracture repair in young and old mice of both sexes. The role of CCN3 in normal female physiology was revealed after detecting a burst of CCN3 expression in ARCKISS1 neurons coincident with lactation. After reducing CCN3 in ARCKISS1 neurons, lactating mothers lost bone and failed to sustain their progeny when challenged with a low-calcium diet. Our findings establish CCN3 as a potentially new therapeutic osteoanabolic hormone for both sexes and define a new maternal brain hormone for ensuring species survival in mammals.
Assuntos
Densidade Óssea , Osso e Ossos , Encéfalo , Hormônios , Mães , Proteína Sobre-Expressa em Nefroblastoma , Osteogênese , Adolescente , Animais , Feminino , Humanos , Masculino , Camundongos , Envelhecimento , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/metabolismo , Osso e Ossos/citologia , Osso e Ossos/metabolismo , Remodelação Óssea , Reabsorção Óssea/metabolismo , Encéfalo/citologia , Encéfalo/metabolismo , Cálcio/administração & dosagem , Cálcio/metabolismo , Lactação/metabolismo , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Células-Tronco/metabolismo , Células-Tronco/citologia , Proteína Sobre-Expressa em Nefroblastoma/metabolismo , Hormônios/metabolismoRESUMO
In addition to their conventional role as a versatile transport system, blood vessels provide signals controlling organ development, regeneration, and stem cell behavior. In the skeletal system, certain capillaries support perivascular osteoprogenitor cells and thereby control bone formation. Blood vessels are also a critical component of niche microenvironments for hematopoietic stem cells. Here we discuss key pathways and factors controlling endothelial cell behavior in bone, the role of vessels in osteogenesis, and the nature of vascular stem cell niches in bone marrow.
Assuntos
Vasos Sanguíneos/metabolismo , Hematopoese , Osteogênese , Transdução de Sinais , Animais , Medula Óssea/irrigação sanguínea , Células Endoteliais/metabolismo , HumanosRESUMO
Osteocytes, former osteoblasts encapsulated by mineralized bone matrix, are far from being passive and metabolically inactive bone cells. Instead, osteocytes are multifunctional and dynamic cells capable of integrating hormonal and mechanical signals and transmitting them to effector cells in bone and in distant tissues. Osteocytes are a major source of molecules that regulate bone homeostasis by integrating both mechanical cues and hormonal signals that coordinate the differentiation and function of osteoclasts and osteoblasts. Osteocyte function is altered in both rare and common bone diseases, suggesting that osteocyte dysfunction is directly involved in the pathophysiology of several disorders affecting the skeleton. Advances in osteocyte biology initiated the development of novel therapeutics interfering with osteocyte-secreted molecules. Moreover, osteocytes are targets and key distributors of biological signals mediating the beneficial effects of several bone therapeutics used in the clinic. Here we review the most recent discoveries in osteocyte biology demonstrating that osteocytes regulate bone homeostasis and bone marrow fat via paracrine signaling, influence body composition and energy metabolism via endocrine signaling, and contribute to the damaging effects of diabetes mellitus and hematologic and metastatic cancers in the skeleton.
Assuntos
Remodelação Óssea/fisiologia , Osteoclastos/citologia , Osteócitos/citologia , Osteogênese/fisiologia , Animais , Reabsorção Óssea/metabolismo , Diferenciação Celular/fisiologia , HumanosRESUMO
Craniosynostosis is a group of disorders of premature calvarial suture fusion. The identity of the calvarial stem cells (CSCs) that produce fusion-driving osteoblasts in craniosynostosis remains poorly understood. Here we show that both physiologic calvarial mineralization and pathologic calvarial fusion in craniosynostosis reflect the interaction of two separate stem cell lineages; a previously identified cathepsin K (CTSK) lineage CSC1 (CTSK+ CSC) and a separate discoidin domain-containing receptor 2 (DDR2) lineage stem cell (DDR2+ CSC) that we identified in this study. Deletion of Twist1, a gene associated with craniosynostosis in humans2,3, solely in CTSK+ CSCs is sufficient to drive craniosynostosis in mice, but the sites that are destined to fuse exhibit an unexpected depletion of CTSK+ CSCs and a corresponding expansion of DDR2+ CSCs, with DDR2+ CSC expansion being a direct maladaptive response to CTSK+ CSC depletion. DDR2+ CSCs display full stemness features, and our results establish the presence of two distinct stem cell lineages in the sutures, with both populations contributing to physiologic calvarial mineralization. DDR2+ CSCs mediate a distinct form of endochondral ossification without the typical haematopoietic marrow formation. Implantation of DDR2+ CSCs into suture sites is sufficient to induce fusion, and this phenotype was prevented by co-transplantation of CTSK+ CSCs. Finally, the human counterparts of DDR2+ CSCs and CTSK+ CSCs display conserved functional properties in xenograft assays. The interaction between these two stem cell populations provides a new biologic interface for the modulation of calvarial mineralization and suture patency.
Assuntos
Craniossinostoses , Humanos , Camundongos , Animais , Craniossinostoses/genética , Osteogênese , Linhagem da Célula , Fenótipo , Células-TroncoRESUMO
Senescence and altered differentiation potential of bone marrow stromal cells (BMSCs) lead to age-related bone loss. As an important posttranscriptional regulatory pathway, alternative splicing (AS) regulates the diversity of gene expression and has been linked to induction of cellular senescence. However, the role of splicing factors in BMSCs during aging remains poorly defined. Herein, we found that the expression of the splicing factor Y-box binding protein 1 (YBX1) in BMSCs decreased with aging in mice and humans. YBX1 deficiency resulted in mis-splicing in genes linked to BMSC osteogenic differentiation and senescence, such as Fn1, Nrp2, Sirt2, Sp7, and Spp1, thus contributing to BMSC senescence and differentiation shift during aging. Deletion of Ybx1 in BMSCs accelerated bone loss in mice, while its overexpression stimulated bone formation. Finally, we identified a small compound, sciadopitysin, which attenuated the degradation of YBX1 and bone loss in old mice. Our study demonstrated that YBX1 governs cell fate of BMSCs via fine control of RNA splicing and provides a potential therapeutic target for age-related osteoporosis.
Assuntos
Células-Tronco Mesenquimais , Osteoporose , Humanos , Camundongos , Animais , Osteogênese/genética , Envelhecimento/metabolismo , Senescência Celular , Diferenciação Celular/genética , Osteoporose/metabolismo , Células da Medula Óssea , Proteína 1 de Ligação a Y-Box/metabolismoRESUMO
During endochondral ossification, chondrocytes secrete a proteoglycan (PG)-rich extracellular matrix that can inhibit the process of cartilage maturation, including expression of Ihh and Col10a1. Because bone morphogenetic proteins (BMPs) can promote cartilage maturation, we hypothesized that cartilage PGs normally inhibit BMP signalling. Accordingly, BMP signalling was evaluated in chondrocytes of wild-type and PG mutant (fam20b-/-) zebrafish and inhibited with temporal control using the drug DMH1 or an inducible dominant-negative BMP receptor transgene (dnBMPR). Compared with wild type, phospho-Smad1/5/9, but not phospho-p38, was increased in fam20b-/- chondrocytes, but only after they secreted PGs. Phospho-Smad1/5/9 was decreased in DMH1-treated or dnBMPR-activated wild-type chondrocytes, and DMH1 also decreased phospho-p38 levels. ihha and col10a1a were decreased in DMH1-treated or dnBMPR-activated chondrocytes, and less perichondral bone formed. Finally, early ihha and col10a1a expression and early perichondral bone formation of fam20b mutants were rescued with DMH1 treatment or dnBMPR activation. Therefore, PG inhibition of canonical BMP-dependent cartilage maturation delays endochondral ossification, and these results offer hope for the development of growth factor therapies for skeletal defects of PG diseases.
Assuntos
Osteogênese , Proteoglicanas , Animais , Osteogênese/genética , Proteoglicanas/genética , Proteoglicanas/metabolismo , Peixe-Zebra/genética , Cartilagem/metabolismo , Condrócitos/metabolismo , Proteínas Morfogenéticas Ósseas/metabolismoRESUMO
Cornelia de Lange syndrome (CdLS) is a congenital disorder featuring facial dysmorphism, postnatal growth deficits, cognitive disability and upper limb abnormalities. CdLS is genetically heterogeneous, with cases arising from mutation of BRD4, a bromodomain protein that binds and reads acetylated histones. In this study, we have modeled CdLS facial pathology through mouse neural crest cell (NCC)-specific mutation of BRD4 to characterize cellular and molecular function in craniofacial development. Mice with BRD4 NCC loss of function died at birth with severe facial hypoplasia, cleft palate, mid-facial clefting and exencephaly. Following migration, BRD4 mutant NCCs initiated RUNX2 expression for differentiation to osteoblast lineages but failed to induce downstream RUNX2 targets required for lineage commitment. BRD4 bound to active enhancers to regulate expression of osteogenic transcription factors and extracellular matrix components integral for bone formation. RUNX2 physically interacts with a C-terminal domain in the long isoform of BRD4 and can co-occupy osteogenic enhancers. This BRD4 association is required for RUNX2 recruitment and appropriate osteoblast differentiation. We conclude that BRD4 controls facial bone development through osteoblast enhancer regulation of the RUNX2 transcriptional program.
Assuntos
Síndrome de Cornélia de Lange , Fatores de Transcrição , Animais , Camundongos , Proteínas de Ciclo Celular/genética , Diferenciação Celular , Subunidade alfa 1 de Fator de Ligação ao Core , Síndrome de Cornélia de Lange/genética , Crista Neural/metabolismo , Proteínas Nucleares/metabolismo , Osteoblastos/metabolismo , Osteogênese , Fatores de Transcrição/metabolismoRESUMO
The Forkhead box transcription factors FOXC1 and FOXC2 are expressed in condensing mesenchyme cells at the onset of endochondral ossification. We used the Prx1-cre mouse to ablate Foxc1 and Foxc2 in limb skeletal progenitor cells. Prx1-cre;Foxc1Δ/Δ;Foxc2Δ/Δ limbs were shorter than controls, with worsening phenotypes in distal structures. Cartilage formation and mineralization was severely disrupted in the paws. The radius and tibia were malformed, whereas the fibula and ulna remained unmineralized. Chondrocyte maturation was delayed, with fewer Indian hedgehog-expressing, prehypertrophic chondrocytes forming and a smaller hypertrophic chondrocyte zone. Later, progression out of chondrocyte hypertrophy was slowed, leading to an accumulation of COLX-expressing hypertrophic chondrocytes and formation of a smaller primary ossification center with fewer osteoblast progenitor cells populating this region. Targeting Foxc1 and Foxc2 in hypertrophic chondrocytes with Col10a1-cre also resulted in an expanded hypertrophic chondrocyte zone and smaller primary ossification center. Our findings suggest that FOXC1 and FOXC2 direct chondrocyte maturation towards hypertrophic chondrocyte formation. At later stages, FOXC1 and FOXC2 regulate function in hypertrophic chondrocyte remodeling to allow primary ossification center formation and osteoblast recruitment.
Assuntos
Condrócitos , Fatores de Transcrição Forkhead , Lâmina de Crescimento , Hipertrofia , Osteogênese , Animais , Fatores de Transcrição Forkhead/metabolismo , Fatores de Transcrição Forkhead/genética , Condrócitos/metabolismo , Condrócitos/citologia , Camundongos , Lâmina de Crescimento/metabolismo , Lâmina de Crescimento/patologia , Lâmina de Crescimento/embriologia , Osteogênese/genética , Extremidades/embriologia , Extremidades/patologia , Condrogênese/genética , Proteínas Hedgehog/metabolismo , Proteínas Hedgehog/genética , Regulação da Expressão Gênica no Desenvolvimento , Diferenciação Celular , Proteínas de Homeodomínio/metabolismo , Proteínas de Homeodomínio/genética , Cartilagem/metabolismo , Cartilagem/patologia , Cartilagem/embriologiaRESUMO
Piezo1 and Piezo2 are recently reported mechanosensory ion channels that transduce mechanical stimuli from the environment into intracellular biochemical signals in various tissues and organ systems. Here, we show that Piezo1 and Piezo2 display a robust expression during jawbone development. Deletion of Piezo1 in neural crest cells causes jawbone malformations in a small but significant number of mice. We further demonstrate that disruption of Piezo1 and Piezo2 in neural crest cells causes more striking defects in jawbone development than any single knockout, suggesting essential but partially redundant roles of Piezo1 and Piezo2. In addition, we observe defects in other neural crest derivatives such as malformation of the vascular smooth muscle in double knockout mice. Moreover, TUNEL examinations reveal excessive cell death in osteogenic cells of the maxillary and mandibular arches of the double knockout mice, suggesting that Piezo1 and Piezo2 together regulate cell survival during jawbone development. We further demonstrate that Yoda1, a Piezo1 agonist, promotes mineralization in the mandibular arches. Altogether, these data firmly establish that Piezo channels play important roles in regulating jawbone formation and maintenance.
Assuntos
Canais Iônicos , Arcada Osseodentária , Crista Neural , Animais , Camundongos , Regulação da Expressão Gênica no Desenvolvimento , Canais Iônicos/metabolismo , Canais Iônicos/genética , Arcada Osseodentária/embriologia , Arcada Osseodentária/metabolismo , Mandíbula/embriologia , Mandíbula/metabolismo , Camundongos Knockout , Crista Neural/metabolismo , Osteogênese/genética , Pirazinas , TiadiazóisRESUMO
In this issue of Immunity, Tyagi et al. (2018) report that the microbial metabolite butyrate orchestrates the interplay between regulatory T cells and CD8+ T cells, increasing Wnt signaling, and promoting bone formation in young mice.
Assuntos
Butiratos , Linfócitos T Reguladores , Animais , Linfócitos T CD8-Positivos , Camundongos , Osteogênese , Transdução de Sinais , Proteínas WntRESUMO
Nutritional supplementation with probiotics can prevent pathologic bone loss. Here we examined the impact of supplementation with Lactobacillus rhamnosus GG (LGG) on bone homeostasis in eugonadic young mice. Micro-computed tomography revealed that LGG increased trabecular bone volume in mice, which was due to increased bone formation. Butyrate produced in the gut following LGG ingestion, or butyrate fed directly to germ-free mice, induced the expansion of intestinal and bone marrow (BM) regulatory T (Treg) cells. Interaction of BM CD8+ T cells with Treg cells resulted in increased secretion of Wnt10b, a bone anabolic Wnt ligand. Mechanistically, Treg cells promoted the assembly of a NFAT1-SMAD3 transcription complex in CD8+ cells, which drove expression of Wnt10b. Reducing Treg cell numbers, or reconstitution of TCRß-/- mice with CD8+ T cells from Wnt10b-/- mice, prevented butyrate-induced bone formation and bone mass acquisition. Thus, butyrate concentrations regulate bone anabolism via Treg cell-mediated regulation of CD8+ T cell Wnt10b production.
Assuntos
Butiratos/farmacologia , Osteogênese/efeitos dos fármacos , Linfócitos T Reguladores/metabolismo , Proteínas Wnt/metabolismo , Animais , Butiratos/metabolismo , Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/metabolismo , Comunicação Celular , Proliferação de Células/efeitos dos fármacos , Feminino , Lacticaseibacillus rhamnosus/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Probióticos/administração & dosagem , Probióticos/metabolismo , Linfócitos T Reguladores/citologia , Proteínas Wnt/genéticaRESUMO
Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of haematopoietic stem cells and early restricted progenitors1-6. LEPR+ cells are heterogeneous, including skeletal stem cells and osteogenic and adipogenic progenitors7-12, although few markers have been available to distinguish these subsets or to compare their functions. Here we show that expression of an osteogenic growth factor, osteolectin13,14, distinguishes peri-arteriolar LEPR+ cells poised to undergo osteogenesis from peri-sinusoidal LEPR+ cells poised to undergo adipogenesis (but retaining osteogenic potential). Peri-arteriolar LEPR+osteolectin+ cells are rapidly dividing, short-lived osteogenic progenitors that increase in number after fracture and are depleted during ageing. Deletion of Scf from adult osteolectin+ cells did not affect the maintenance of haematopoietic stem cells or most restricted progenitors but depleted common lymphoid progenitors, impairing lymphopoiesis, bacterial clearance, and survival after acute bacterial infection. Peri-arteriolar osteolectin+ cell maintenance required mechanical stimulation. Voluntary running increased, whereas hindlimb unloading decreased, the frequencies of peri-arteriolar osteolectin+ cells and common lymphoid progenitors. Deletion of the mechanosensitive ion channel PIEZO1 from osteolectin+ cells depleted osteolectin+ cells and common lymphoid progenitors. These results show that a peri-arteriolar niche for osteogenesis and lymphopoiesis in bone marrow is maintained by mechanical stimulation and depleted during ageing.