RESUMO
Neurofibromatosis type 1 (NF1) is a tumor predisposition syndrome caused by heterozygous NF1 gene mutations. Patients with NF1 present with pleiotropic somatic secondary manifestations, including development of bone pseudarthrosis after fracture. Somatic NF1 gene mutations were reproducibly identified in patient-derived pseudarthrosis specimens, suggesting a local mosaic cell population including somatic pathologic cells. The somatic cellular pathogenesis of NF1 pseudarthroses remains unclear, though defects in osteogenesis have been posited. Here, we applied time-series single-cell RNA-sequencing (scRNA-seq) to patient-matched control and pseudarthrosis-derived primary bone stromal cells (BSCs). We show that osteogenic specification to an osteoblast progenitor cell population was evident for control bone-derived cells and haploinsufficient pseudarthrosis-derived cells. Similar results were observed for somatic patient fracture-derived NF1-/- cells; however, expression of genetic pathways associated with skeletal mineralization were significantly reduced in NF1-/- cells compared with fracture-derived NF1+/- cells. In mice, we show that Nf1 expressed in bone marrow osteoprogenitors is required for the maintenance of the adult skeleton. Results from our study implicate impaired Clec11a-Itga11-Wnt signaling in the pathogenesis of NF1-associated skeletal disease. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
Assuntos
Fraturas Ósseas , Neurofibromatose 1 , Pseudoartrose , Camundongos , Animais , Neurofibromatose 1/complicações , Neurofibromatose 1/genética , Neurofibromatose 1/patologia , Pseudoartrose/genética , Pseudoartrose/metabolismo , Pseudoartrose/patologia , Fraturas Ósseas/patologia , Osteoblastos/metabolismo , Osteogênese/genéticaRESUMO
Proper embryonic and postnatal skeletal development require coordination of myriad complex molecular mechanisms. Disruption of these processes, through genetic mutation, contributes to variation in skeletal development. We developed a high-throughput N-ethyl-N-nitrosourea (ENU)-induced saturation mutagenesis skeletal screening approach in mice to identify genes required for proper skeletal development. Here, we report initial results from live-animal X-ray and dual-energy X-ray absorptiometry (DXA) imaging of 27,607 G3 mice from 806 pedigrees, testing the effects of 32,198 coding/splicing mutations in 13,020 genes. A total of 39.7% of all autosomal genes were severely damaged or destroyed by mutations tested twice or more in the homozygous state. Results from our study demonstrate the feasibility of in vivo mutagenesis to identify mouse models of skeletal disease. Furthermore, our study demonstrates how ENU mutagenesis provides opportunities to create and characterize putative hypomorphic mutations in developmentally essential genes. Finally, we present a viable mouse model and case report of recessive skeletal disease caused by mutations in FAM20B. Results from this study, including engineered mouse models, are made publicly available via the online Mutagenetix database. © 2021 American Society for Bone and Mineral Research (ASBMR).
Assuntos
Doenças Ósseas/genética , Células Germinativas , Mutagênese , Animais , Etilnitrosoureia , Humanos , Camundongos , Mutação , Fenótipo , Fosfotransferases (Aceptor do Grupo Álcool)/genéticaRESUMO
GATA4 is a transcription factor that regulates osteoblast differentiation. However, GATA4 is expressed at a higher level in mesenchymal stem cells (MSCs) than in osteoblasts. Therefore, the role of GATA4 in limb bud mesenchyme differentiation was investigated in mice by knocking out Gata4 using Cre-recombinase controlled by the Prx1 promoter (herein called Gata4 Prx-cKO mice). µCT analysis of the Gata4 Prx-cKO mice showed a decrease in trabecular bone properties compared with wildtype (Gata4fl/fl) littermates. Gata4 Prx-cKO mice have fewer MSCs as measured by CFU-F assays, mesenchymal progenitor cells (MPC2) (flow cytometry of Sca1+/CD45-/CD34-/CD44hi) and nestin immunofluorescence. Gata4 Prx-cKO bone marrow-derived MSCs have a significant reduction in WNT ligands, including WNT10B, and WNT signalosome components compared to control cells. Chromatin immunoprecipitation demonstrates that GATA4 is recruited to enhancers near Wnt3a, Wnt10b, Fzd6 and Dkk1. GATA4 also directly represses YAP in wildtype cells, and the absence of Gata4 leads to increased YAP expression. Together, we show that the decrease in MSCs is due to loss of Gata4 and a WNT10B-dependent positive autoregulatory loop. This leads to a concurrent increase of YAP and less activated ß-catenin. These results explain the decreased trabecular bone in Gata4 Prx-cKO mice. We suggest that WNT signalosome activity in MSCs requires Gata4 and Wnt10b expression for lineage specification.
Assuntos
Fator de Transcrição GATA4/fisiologia , Células-Tronco Mesenquimais , Via de Sinalização Wnt , Animais , Diferenciação Celular , Regulação da Expressão Gênica , Células-Tronco Mesenquimais/metabolismo , Camundongos , Proteínas do Tecido Nervoso , Osteoblastos/metabolismo , Osteogênese , Proteínas Wnt , beta Catenina/metabolismoRESUMO
Talipes equinovarus (clubfoot, TEV) is a congenital rotational foot deformity occurring in 1 per 1000 births with increased prevalence in males compared with females. The genetic etiology of isolated clubfoot (iTEV) remains unclear. Using a genome-wide association study, we identified a locus within FSTL5, encoding follistatin-like 5, significantly associated with iTEV. FSTL5 is an uncharacterized gene whose potential role in embryonic and postnatal development was previously unstudied. Utilizing multiple model systems, we found that Fstl5 was expressed during later stages of embryonic hindlimb development, and, in mice, expression was restricted to the condensing cartilage anlage destined to form the limb skeleton. In the postnatal growth plate, Fstl5 was specifically expressed in prehypertrophic chondrocytes. As Fstl5 knockout rats displayed no gross malformations, we engineered a conditional transgenic mouse line (Fstl5LSL) to overexpress Fstl5 in skeletal osteochondroprogenitors. We observed that hindlimbs were slightly shorter and that bone mineral density was reduced in adult male, but not female, Prrx1-cre;Fstl5LSL mice compared with control. No overt clubfoot-like deformity was observed in Prrx1-cre;Fstl5LSL mice, suggesting FSTL5 may function in other cell types to contribute to iTEV pathogenesis. Interrogating published mouse embryonic single-cell expression data showed that Fstl5 was expressed in cell lineage subclusters whose transcriptomes were associated with neural system development. Moreover, our results suggest that lineage-specific expression of the Fstl genes correlates with their divergent roles as modulators of transforming growth factor beta and bone morphogenetic protein signaling. Results from this study associate FSTL5 with iTEV and suggest a potential sexually dimorphic role for Fstl5 in vivo.
Assuntos
Pé Torto Equinovaro/genética , Proteínas Relacionadas à Folistatina/genética , Predisposição Genética para Doença , Proteínas de Homeodomínio/genética , Animais , Pé Torto Equinovaro/patologia , Modelos Animais de Doenças , Extremidades/patologia , Regulação da Expressão Gênica/genética , Técnicas de Inativação de Genes , Estudos de Associação Genética , Humanos , Camundongos , RatosRESUMO
Triple-negative breast cancers (TNBCs), which lack specific targeted therapy options, evolve into highly chemo-resistant tumors that metastasize to multiple organs simultaneously. We have previously shown that TNBCs maintain an activated WNT10B-driven network that drives metastasis. Pharmacologic inhibition by ICG-001 decreases ß-catenin-mediated proliferation of multiple TNBC cell lines and TNBC patient-derived xenograft (PDX)-derived cell lines. In vitro, ICG-001 was effective in combination with the conventional cytotoxic chemotherapeutics, cisplatin and doxorubicin, to decrease the proliferation of MDA-MB-231 cells. In contrast, in TNBC PDX-derived cells doxorubicin plus ICG-001 was synergistic, while pairing with cisplatin was not as effective. Mechanistically, cytotoxicity induced by doxorubicin, but not cisplatin, with ICG-001 was associated with increased cleavage of PARP-1 in the PDX cells only. In vivo, MDA-MB-231 and TNBC PDX orthotopic primary tumors initiated de novo simultaneous multi-organ metastases, including bone metastases. WNT monotherapy blocked multi-organ metastases as measured by luciferase imaging and histology. The loss of expression of the WNT10B/ß-catenin direct targets HMGA2, EZH2, AXIN2, MYC, PCNA, CCND1, transcriptionally active ß-catenin, SNAIL and vimentin both in vitro and in vivo in the primary tumors mechanistically explains loss of multi-organ metastases. WNT monotherapy induced VEGFA expression in both tumor model systems, whereas increased CD31 was observed only in the MDA-MB-231 tumors. Moreover, WNT-inhibition sensitized the anticancer response of the TNBC PDX model to doxorubicin, preventing simultaneous metastases to the liver and ovaries, as well as to bone. Our data demonstrate that WNT-inhibition sensitizes TNBC to anthracyclines and treats multi-organ metastases of TNBC.
RESUMO
Osteosarcoma is a malignant tumor in the bone, which originates from normal osteoblasts or osteoblast precursors. Normal osteoblasts express estrogen receptor alpha (ERα); however, osteosarcomas do not express ERα due to promoter DNA methylation. Here we show that treatment of 143B osteosarcoma cells with decitabine (DAC, 5-Aza-2'-deoxycytidine) induces expression of ERα and leads to decreased proliferation and concurrent induction of osteoblast differentiation. DAC exposure reduced protein expression of metastasis-associated markers VIMENTIN, SLUG, ZEB1, and MMP9, with a concurrent decrease in mRNA expression of known stem cell markers SOX2, OCT4, and NANOG. Treatment with 17ß-estradiol (E2) synergized with DAC to reduce proliferation. Overexpression of ERα inhibited proliferation and induced osteoblast differentiation, whereas knockout of ERα by CRISPR/Cas9 prevented the effects of DAC. In an orthotopic model of osteosarcoma, DAC inhibited tumor growth and metastasis of 143B cells injected into the tibia of NOD SCID gamma mice. Furthermore, ERα overexpression reduced tumor growth and metastasis, and ERα knockout prevented the effects of DAC in vivo. Together, these experiments provide preclinical evidence that the FDA-approved DNA methylation inhibitor DAC may be repurposed to treat patients with osteosarcoma based on its efficacy to decrease proliferation, to induce osteoblast differentiation, and to reduce metastasis to visceral organs.Significance: These findings describe the effects of DNA methyltransferase inhibition on ERα and its potential role as a tumor suppressor in osteosarcoma.See related commentary by Roberts, p. 1034 See related article by El Ayachi and colleagues; Cancer Res 79(5);982-93.
Assuntos
Metilação de DNA , Decitabina/farmacologia , Receptor alfa de Estrogênio/metabolismo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Pulmonares/tratamento farmacológico , Osteossarcoma/tratamento farmacológico , Animais , Antimetabólitos Antineoplásicos/farmacologia , Apoptose , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Neoplasias Ósseas/tratamento farmacológico , Neoplasias Ósseas/metabolismo , Neoplasias Ósseas/patologia , Proliferação de Células , Receptor alfa de Estrogênio/antagonistas & inibidores , Receptor alfa de Estrogênio/genética , Humanos , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/secundário , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/secundário , Masculino , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Osteossarcoma/metabolismo , Osteossarcoma/patologia , Prognóstico , Regiões Promotoras Genéticas , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
GATA4 is a zinc-finger transcription factor that is a pioneer factor in various tissues and regulates tissue-specific gene regulation. In vivo deletion of Gata4 using Cre-recombinase under the control of the Col1a1 2.3 kb promoter showed significantly reduced values for trabecular bone properties by microCT analysis of femur and tibia of 14-week-old male and female mice, suggesting GATA4 is necessary for maintaining normal adult bone phenotype. Quantitative PCR analysis revealed higher expression of Gata4 in trabecular bone compared with cortical bone, suggesting a role for GATA4 in maintaining normal trabecular bone mass. In vivo and in vitro, reduction of Gata4 correlates with reduced Runx2 gene expression, along with reduced osteoblast mineralization. To determine if Runx2 is a direct target of GATA4, chromatin immunoprecipitation (ChIP) was performed, and it demonstrated that GATA4 is recruited to the two Runx2 promoters and an enhancer region. Furthermore, when Gata4 is knocked down, the chromatin at the Runx2 region is not open, as detected by DNase assays and ChIP with antibodies to the open chromatin marks H3K4me2 (histone 3 lysine 4 dimethylation) and H3K27ac (histone 3 lysine 27 acetylation) and the closed chromatin mark H3K27me2 (histone 3 lysine 27 trimethylation). Together, the data suggest that GATA4 binds near the Runx2 promoter and enhancer and helps maintain open chromatin to regulate Runx2 expression leading to bone mineralization.
RESUMO
GATA4 is a transcription factor that is responsible for tissue-specific gene regulation in many tissues, and more recent studies showed that it is necessary for osteoblast differentiation. Previously, we showed that in vivo deletion of Gata4 using Cre-recombinase under the control of the Col1a1 2.3â¯kb promoter, showed significantly reduced trabecular bone properties. To understand the role of GATA4 in more differentiated cells, GATA4fl/fl mice were crossed with mice expressing Cre-recombinase under the control of the osteocalcin promoter. MicroCT analysis of trabecular bone properties of the femur and tibia from 14-week-old female osteocalcin-Cre/GATA4fl/fl (OCN-cKO) mice showed a significant reduction in percentage bone volume, a decrease in trabecular number and an increase in trabecular spacing. In vivo, histomorphometric analysis revealed a decrease in the number of osteoblasts and an increase in the number of osteoclasts in the tibiae of OCN-cKO mice. In vivo and in vitro systems correlated a decrease in Gata4 mRNA with increased RANKL gene expression. To determine if RANKL is a direct target of GATA4, chromatin immunoprecipitation (ChIP)-sequencing was performed, and it demonstrated that GATA4 is recruited to seven enhancers near RANKL. Furthermore, when Gata4 is knocked down, the chromatin at the RANKL region is further opened, as detected by a reduction in histone 3 lysine 27 trimethylation (H3K27me3) and an increase in histone 3 lysine 4 dimethylation (H3K4me2) in the RANKL locus. In vitro, TRAP staining of cells from bone marrow cultures from Gata4 knockout cells show that the increased levels of RANKL are sufficient for osteoclast formation. Together, the data suggest that GATA4 directly represses RANKL expression via seven cis-regulatory regions and plays an important role in maintaining proper bone development and osteoclast formation.
Assuntos
Diferenciação Celular/genética , Elementos Facilitadores Genéticos/genética , Fator de Transcrição GATA4/metabolismo , Osteoblastos/metabolismo , Osteoclastos/citologia , Ligante RANK/metabolismo , Proteínas Repressoras/metabolismo , Animais , Reabsorção Óssea/patologia , Osso Esponjoso/citologia , Linhagem Celular Tumoral , Humanos , Camundongos Knockout , Osteoclastos/metabolismo , Osteogênese , Ligante RANK/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Estrogens attenuate bone turnover by inhibiting both osteoclasts and osteoblasts, in part through antagonizing Runx2. Apparently conflicting, stimulatory effects in osteoblast lineage cells, however, sway the balance between bone resorption and bone formation in favor of the latter. Consistent with this dualism, 17ß-estradiol (E2) both stimulates and inhibits Runx2 in a locus-specific manner, and here we provide evidence for such locus-specific regulation of Runx2 by E2 in vivo. We also demonstrate dual, negative and positive, regulation of Runx2-driven alkaline phosphatase (ALP) activity by increasing E2 concentrations in ST2 osteoblast progenitor cells. We further compared the effects of E2 to those of the Selective Estrogen Receptor Modulators (SERMs) raloxifene (ral) and lasofoxifene (las) and the phytoestrogen puerarin. We found that E2 at the physiological concentrations of 0.1-1â¯nM, as well as ral and las, but not puerarin, antagonize Runx2-driven ALP activity. At ≥10â¯nM, E2 and puerarin, but not ral or las, stimulate ALP relative to the activity measured at 0.1-1â¯nM. Contrasting the difference between E2 and SERMs in ST2 cells, they all shared a similar dose-response profile when inhibiting pre-osteoclast proliferation. That ral and las poorly mimic the locus- and concentration-dependent effects of E2 in mesenchymal progenitor cells may help explain their limited clinical efficacy.
Assuntos
Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Estrogênios/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Células-Tronco Mesenquimais/metabolismo , Moduladores Seletivos de Receptor Estrogênico/farmacologia , Fosfatase Alcalina/metabolismo , Animais , Células Cultivadas , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Feminino , Humanos , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Transdução de SinaisRESUMO
We have recently demonstrated that RUNX2 promoted, and 17ß-Estradiol (E2) diminished, association of RANKL with the cell membrane in pre-osteoblast cultures. Here we show that, similar to E2, dihydrotestosterone (DHT) diminishes association of RANKL, and transiently transfected GFP-RANKL with the pre-osteoblast membrane without decreasing total RANKL mRNA or protein levels. Diminution of membrane-associated RANKL was accompanied with marked suppression of osteoclast differentiation from co-cultured pre-osteoclasts, even though DHT increased, not decreased, RANKL concentrations in pre-osteoblast conditioned media. A marked decrease in membrane-associated RANKL was observed after 30 min of either E2 or DHT treatment, and near-complete inhibition was observed by 1 hr, suggesting that the diminution of RANKL membrane association was mediated through non-genomic mechanisms. Further indicating dispensability of nuclear action of estrogen receptor, E2-mediated inhibition of RANKL membrane association was mimicked by an estrogen dendrimer conjugate (EDC) that cannot enter the cell nucleus. Finally, the inhibitory effect of E2 and DHT on RANKL membrane association was counteracted by the MMP inhibitor NNGH, and the effect of E2 (and not DHT) was antagonized by the Src inhibitor SU6656. Taken together, these results suggest that estrogens and androgens inhibit osteoblast-driven osteoclastogenesis through non-genomic mechanism(s) that entail, MMP-mediated RANKL dissociation from the cell membrane.
Assuntos
Membrana Celular/efeitos dos fármacos , Di-Hidrotestosterona/farmacologia , Estradiol/farmacologia , Osteoblastos/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ligante RANK/metabolismo , Animais , Animais Recém-Nascidos , Membrana Celular/metabolismo , Técnicas de Cocultura , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Meios de Cultivo Condicionados/metabolismo , Inibidores de Metaloproteinases de Matriz/farmacologia , Metaloproteinases da Matriz/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Osteoblastos/metabolismo , Osteoclastos/efeitos dos fármacos , Osteoclastos/metabolismo , Osteogênese/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Ligante RANK/genética , Células RAW 264.7 , Fatores de Tempo , Transfecção , Quinases da Família src/antagonistas & inibidores , Quinases da Família src/metabolismoRESUMO
Inhibition of Runx2 is one of many mechanisms that suppress bone formation in glucocorticoid (GC)-induced osteoporosis (GIO). We profiled mRNA expression in ST2/Rx2(dox) cells after treatment with doxycycline (dox; to induce Runx2) and/or the synthetic GC dexamethasone (dex). As expected, dex typically antagonized Runx2-driven transcription. Select genes, however, were synergistic stimulated and this was confirmed by RT-qPCR. Among the genes synergistically stimulated by GCs and Runx2 was Wnt inhibitory Factor 1 (Wif1), and Wif1 protein was readily detectable in medium conditioned by cultures co-treated with dox and dex, but neither alone. Cooperation between Runx2 and GCs in stimulating Wif1 was also observed in primary preosteoblast cultures. GCs strongly inhibited dox-driven alkaline phosphatase (ALP) activity in control ST2/Rx2(dox) cells, but not in cells in which Wif1 was silenced. Unlike its anti-mitogenic activity in committed osteoblasts, induction of Runx2 transiently increased the percentage of cells in S-phase and accelerated proliferation in the ST2 mesenchymal pluripotent cell culture model. Furthermore, like the inhibition of Runx2-driven ALP activity, dex antagonized the transient mitogenic effect of Runx2 in ST2/Rx2(dox) cultures, and this inhibition eased upon Wif1 silencing. Plausibly, homeostatic feedback loops that rely on Runx2 activation to compensate for bone loss in GIO are thwarted, exacerbating disease progression through stimulation of Wif1. J. Cell. Physiol. 232: 145-153, 2017. © 2016 Wiley Periodicals, Inc.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Glucocorticoides/farmacologia , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Células-Tronco Mesenquimais/efeitos dos fármacos , Osteoblastos/efeitos dos fármacos , Proteínas Adaptadoras de Transdução de Sinal , Animais , Linhagem Celular , Células Cultivadas , Dexametasona/farmacologia , Células-Tronco Mesenquimais/citologia , Camundongos , Osteoblastos/citologia , Osteoblastos/metabolismo , Fatores de Transcrição/metabolismoRESUMO
The endocannabinoid system is known for its regulatory effects on bone metabolism through the cannabinoid receptors, Cnr1 and Cnr2. In this study we analysed the mechanical and material properties of long bones from Cnr1(-/-) mice on a C57BL/6 background. Tibiae and femora from 5- and 12-week-old mice were subjected to three-point bending to measure bending stiffness and yield strength. Elastic modulus, density and mineral content were measured in the diaphysis. Second moment of area (MOA2), inner and outer perimeters of the cortical shaft and trabecular fractional bone volume (BV/TV) were measured using micro-CT. In Cnr1(-/-) males and females at both ages the bending stiffness was reduced due to a smaller MOA2. Bone from Cnr1(-/-) females had a greater modulus than wild-type controls, although no differences were observed in males. BV/TV of 12-week-old Cnr1(-/-) females was greater than controls, although no difference was seen at 5-weeks. On the contrary, Cnr1(-/-) males had the same BV/TV as controls at 12-weeks while they had significantly lower values at 5-weeks. This study shows that deleting Cnr1 decreases the amount of cortical bone in both males and females at 12-weeks, but increases the amount of trabecular bone only in females.
Assuntos
Osso Esponjoso/metabolismo , Osso Cortical/metabolismo , Técnicas de Inativação de Genes , Fenômenos Mecânicos , Receptor CB1 de Canabinoide/deficiência , Receptor CB1 de Canabinoide/genética , Animais , Fenômenos Biomecânicos , Osso Esponjoso/diagnóstico por imagem , Osso Cortical/diagnóstico por imagem , Feminino , Fêmur/diagnóstico por imagem , Fêmur/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Tíbia/diagnóstico por imagem , Tíbia/metabolismo , Microtomografia por Raio-XRESUMO
Estrogens are important for bone metabolism via a variety of mechanisms in osteoblasts, osteocytes, osteoclasts, immune cells and other cells to maintain bone mineral density. Estrogens bind to estrogen receptor alpha (ERα) and ERß, and the roles of each of these receptors are beginning to be elucidated through whole body and tissue-specific knockouts of the receptors. In vitro and in vivo experiments have shown that ERα and ERß antagonize each other in bone and in other tissues. This review will highlight the role of these receptors in bone, with particular emphasis on their antagonism.
Assuntos
Osso e Ossos/metabolismo , Receptor alfa de Estrogênio/metabolismo , Receptor beta de Estrogênio/metabolismo , Animais , Regulação da Expressão Gênica , Humanos , Osteoblastos/metabolismo , Osteoclastos/metabolismoRESUMO
Hemophilia type A is a rare inherited bleeding disorder with a diversity of clinical manifestations ranging from persistent bleeding after minor trauma, spontaneous deep muscle or joint hemorrhage, to intracranial hemorrhage. As an X-linked disorder, hemophilia is rare in females and therefore there is little experience with pregnancy and no standardized guidelines to prevent bleeding antepartum, at delivery, and postpartum. We report the clinical course and management of a woman with severe hemophilia A who on two occasions had uncomplicated pregnancies and vaginal deliveries at term utilizing bolus recombinant factor VIII concentrate.
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Bisphosphonates are effective antiresorptive agents owing to their bone-targeting property and ability to inhibit osteoclasts. It remains unclear, however, whether any non-osteoclast cells are directly affected by these drugs in vivo. Two fluorescent risedronate analogues, carboxyfluorescein-labeled risedronate (FAM-RIS) and Alexa Fluor 647-labeled risedronate (AF647-RIS), were used to address this question. Twenty-four hours after injection into 3-month-old mice, fluorescent risedronate analogues were bound to bone surfaces. More detailed analysis revealed labeling of vascular channel walls within cortical bone. Furthermore, fluorescent risedronate analogues were present in osteocytic lacunae in close proximity to vascular channels and localized to the lacunae of newly embedded osteocytes close to the bone surface. Following injection into newborn rabbits, intracellular uptake of fluorescently labeled risedronate was detected in osteoclasts, and the active analogue FAM-RIS caused accumulation of unprenylated Rap1A in these cells. In addition, CD14(high) bone marrow monocytes showed relatively high levels of uptake of fluorescently labeled risedronate, which correlated with selective accumulation of unprenylated Rap1A in CD14(+) cells, as well as osteoclasts, following treatment with risedronate in vivo. Similar results were obtained when either rabbit or human bone marrow cells were treated with fluorescent risedronate analogues in vitro. These findings suggest that the capacity of different cell types to endocytose bisphosphonate is a major determinant for the degree of cellular drug uptake in vitro as well as in vivo. In conclusion, this study shows that in addition to bone-resorbing osteoclasts, bisphosphonates may exert direct effects on bone marrow monocytes in vivo.