Bone Morphogenetic Protein Signaling Pathway Research Articles

Bifunctional Role of CrkL during Bone Remodeling.

Coupled signaling between bone-forming osteoblasts and bone-resorbing osteoclasts is crucial to the maintenance of bone homeostasis. We previously reported that v-crk avian sarcoma virus CT10 oncogene homolog-like (CrkL), which belongs to the Crk family of adaptors, inhibits bone morphogenetic protein 2 (BMP2)-mediated osteoblast differentiation, while enhancing receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation. In this study, we investigated whether CrkL can also regulate the coupling signals between osteoblasts and osteoclasts, facilitating bone homeostasis. Osteoblastic CrkL strongly decreased RANKL expression through its inhibition of runt-related transcription factor 2 (Runx2) transcription. Reduction in RANKL expression by CrkL in osteoblasts resulted in the inhibition of not only osteoblast-dependent osteoclast differentiation but also osteoclast-dependent osteoblast differentiation, suggesting that CrkL participates in the coupling signals between osteoblasts and osteoclasts via its regulation of RANKL expression. Therefore, CrkL bifunctionally regulates osteoclast differentiation through both a direct and indirect mechanism while it inhibits osteoblast differentiation through its blockade of both BMP2 and RANKL reverse signaling pathways. Collectively, these data suggest that CrkL is involved in bone homeostasis, where it helps to regulate the complex interactions of the osteoblasts, osteoclasts, and their coupling signals.

Genetic variants in bone morphogenetic proteins signaling pathway might be involved in palatal rugae phenotype in humans

This study investigated, if genetic variants in BMP2, BMP4 and SMAD6 are associated with variations in the palatal rugae pattern in humans. Dental casts and genomic DNA from 75 patients were evaluated. Each patient was classified as follows: total amount of rugae; bilateral symmetry in the amount, length and shape of the palatal rugae; presence of secondary or fragmentary palatal rugae; presence of unifications; predominant shape; and predominant direction of the palatal rugae. The genetic variants in BMP2 (rs1005464 and rs235768), BMP4 (rs17563) and SMAD6 (rs2119261 and rs3934908) were genotyped. Genotype distribution was compared between palatal rugae patterns using the chi-square test (alpha = 0.05). The allele A was associated with the presence of secondary or fragmentary rugae for rs1005464 (OR = 2.5, 95%CI 1.1–6.3; p = 0.014). Secondary or fragmentary rugae were associated with the G allele in rs17563 (OR = 2.1, 95%CI 1.1–3.9; p = 0.017). rs17563 was also associated with rugae unification (p = 0.017 in the additive model). The predominant shape (wavy) was associated with rs2119261 (p = 0.023 in the additive model). The left–right symmetry of the length of primary rugae was associated with rs3934908 in the recessive model (OR = 3.6, 95%CI 1.2–11.7; p = 0.025). In conclusion, genetic variants in the BMP pathway impacted on palatal rugae pattern.

The amelioration of T2DM rat femoral bone achieved by anti-osteoporosis of caprine CSN1S2 protein through bone morphogenetic protein signaling pathway.

We investigated the potential anti-glycation and anti-osteoporosis properties of Caprine milk CSN1S2 protein on the serum AGEs and sRAGE level, osteogenic factors expressions, femoral bone mesostructure, histomorphometry, and hydroxyapatite crystals changes in T2DM rats. Varying doses of Caprine milk CSN1S2 protein (0, 375, 750, and 1500 mg/kg BW) were used to treat the control and T2DM rats. We measured AGEs and sRAGE level; RUNX2, OSX, BMP2, and Caspase-3 expressions in rats using ELISA and immunohistochemistry, respectively. The mesostructure and histomorphometry of femoral bone was analyzed using SEM Microscope and BoneJ software, then hydroxyapatite crystal size was determined using SEM-XRD. T2DM rats showed a high level of AGEs and a low level of sRAGE, the RUNX2, OSX, and BMP2 expression was down regulated, BV, BV.TV, Tb.Th, Tb.Sp, increased and SMI levels declined, respectively. Vice versa, after administration of the CSN1S2 protein to T2DM rats, improvement in all levels of molecular and cellular markers was achieved. In the CSN1S2 highest dose, AGEs level declined and sRAGE level elevated in T2DM rats. The 375 and 750 mg/kgBW of CSN1S2 protein was able to upregulate the RUNX2, OSX, and BMP2 expression in T2DM rats, thus improving the normalization of osteoclasts and osteoblasts number. The whole dose of CSN1S2 triggered the thickening of trabecular bone wall, granule formation, and normalized the trabecular thickness (Tb.Th) parameter of T2DM rats. The hydroxyapatite crystal size was increased in the highest dose of CSN1S2-treated T2DM rats. This study indicated that CSN1S2 protein had a protective effect against osteoporosis in the T2DM rat bones by means of glycation pathway inhibition, bone histomorphometry and mesostructure improvement via bone morphometric protein signaling.

The Smad Dependent TGF-β and BMP Signaling Pathway in Bone Remodeling and Therapies.

Bone remodeling is a continuous process that maintains the homeostasis of the skeletal system, and it depends on the homeostasis between bone-forming osteoblasts and bone-absorbing osteoclasts. A large number of studies have confirmed that the Smad signaling pathway is essential for the regulation of osteoblastic and osteoclastic differentiation during skeletal development, bone formation and bone homeostasis, suggesting a close relationship between Smad signaling and bone remodeling. It is known that Smads proteins are pivotal intracellular effectors for the members of the transforming growth factor-β (TGF-β) and bone morphogenetic proteins (BMP), acting as transcription factors. Smad mediates the signal transduction in TGF-β and BMP signaling pathway that affects both osteoblast and osteoclast functions, and therefore plays a critical role in the regulation of bone remodeling. Increasing studies have demonstrated that a number of Smad signaling regulators have potential functions in bone remodeling. Therefore, targeting Smad dependent TGF-β and BMP signaling pathway might be a novel and promising therapeutic strategy against osteoporosis. This article aims to review recent advances in this field, summarizing the influence of Smad on osteoblast and osteoclast function, together with Smad signaling regulators in bone remodeling. This will facilitate the understanding of Smad signaling pathway in bone biology and shed new light on the modulation and potential treatment for osteoporosis.

The Potential of Nail Mini-Organ Stem Cells in Skin, Nail and Digit Tips Regeneration.

Nails are highly keratinized skin appendages that exhibit continuous growth under physiological conditions and full regeneration upon removal. These mini-organs are maintained by two autonomous populations of skin stem cells. The fast-cycling, highly proliferative stem cells of the nail matrix (nail stem cells (NSCs)) predominantly replenish the nail plate. Furthermore, the slow-cycling population of the nail proximal fold (nail proximal fold stem cells (NPFSCs)) displays bifunctional properties by contributing to the peri-nail epidermis under the normal homeostasis and the nail structure upon injury. Here, we discuss nail mini-organ stem cells’ location and their role in skin and nail homeostasis and regeneration, emphasizing their importance to orchestrate the whole digit tip regeneration. Such endogenous regeneration capabilities are observed in rodents and primates. However, they are limited to the region adjacent to the nail’s proximal area, indicating the crucial role of nail mini-organ stem cells in digit restoration. Further, we explore the molecular characteristics of nail mini-organ stem cells and the critical role of the bone morphogenetic protein (BMP) and Wnt signaling pathways in homeostatic nail growth and digit restoration. Finally, we investigate the latest accomplishments in stimulating regenerative responses in regeneration-incompetent injuries. These pioneer results might open up new opportunities to overcome amputated mammalian digits and limbs’ regenerative failures in the future.

Functional Regulatory Mechanisms Underlying Bone Marrow Mesenchymal Stem Cell Senescence During Cell Passages.

Mesenchymal stem cell (MSC) transplantation is an effective periodontal regenerative therapy. MSCs are multipotent, have self-renewal ability, and can differentiate into periodontal cells. However, senescence is inevitable for MSCs. In vitro, cell senescence can be induced by long-term culture with/without cell passage. However, the regulatory mechanism of MSC senescence remains unclear. Undifferentiated MSC-specific transcription factors can regulate MSC function. Herein, we identified the regulatory transcription factors involved in MSC senescence and elucidated their mechanisms of action. We cultured human MSCs (hMSCs) with repetitive cell passages to induce cell senescence and evaluated the mRNA and protein expression of cell senescence-related genes. Additionally, we silenced the cell senescence-induced transcription factors, GATA binding protein 6 (GATA6) and SRY-box 11 (SOX11), and investigated senescence-related signaling pathways. With repeated passages, the number of senescent cells increased, while the cell proliferation capacity decreased; GATA6 mRNA expression was upregulated and that of SOX11 was downregulated. Repetitive cell passages decreased Wnt and bone morphogenetic protein (BMP) signaling pathway-related gene expression. Silencing of GATA6 and SOX11 regulated Wnt and BMP signaling pathway-related genes and affected cell senescence-related genes; moreover, SOX11 silencing regulated GATA6 expression. Hence, we identified them as pair of regulatory transcription factors for cell senescence in hMSCs via the Wnt and BMP signaling pathways.

Stichopus japonicus Polysaccharide Stimulates Osteoblast Differentiation through Activation of the Bone Morphogenetic Protein Pathway in MC3T3-E1 Cells.

This study aimed to examine the combined use of bone morphogenetic protein-2 (BMP-2) and polysaccharide isolated from Stichopus japonicus on osteogenic differentiation of MC3T3-E1 cells. Osteogenic differentiation was measured via histochemical staining of alkaline phosphatase (ALP) assay, alizarin red staining of mineralization assay, Western blotting, ELISA, and a qRT-PCR evaluation for the expression of BMP-2, runt-related transcription factor-2 (Runx-2), osteocalcin (OCN), osteopontin (OPN), and collagen type I (Col I) in MC3T3-E1 cells. Immunofluorescence assay was utilized to assess the BMP-2 localized on the cell surface. The results illustrated that SP-2 was able to increase ALP expression and accelerate the mineralization. Osteoblasts cultured on BMP-2/SP-2 substrate increased the expression levels of BMP-2, Runx-2, Col I, OCN, and OPN. SP-2 increased the binding efficiency involving a BMP-2 and its cell surface receptor. The dose of 5 μg/mL SP-2 used showed the best function of inducing osteoblast differentiation. These findings indicated that SP-2 is a more effective enhancer that cooperated with BMP-2 to induce osteoblastic differentiation by utilizing the BMP-2 signaling pathway.

Boron-incorporated micro/nano-topographical calcium silicate coating dictates osteo/angio-genesis and inflammatory response toward enhanced osseointegration

Orthopedic implant coatings with optimal surface features to achieve favorable osteo/angio-genesis and inflammatory response would be of great importance. However, to date, few coatings are capable of fully satisfying these requirements. In this work, to take advantage of the structural complexity of micro/nano-topography and benefits of biological trace elements, two types of boron-containing nanostructures (nanoflakes and nanolamellars) were introduced onto plasma-sprayed calcium silicate (F-BCS and L-BCS) coatings via hydrothermal treatment. The C-CS coating using deionized water as hydrothermal medium served as control. Boron-incorporated CS coating stimulated osteoblastic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Specifically, the combination of β1 integrin-vinculin-mediated cell spreading and activation of bone morphogenetic protein signaling pathway acted synergistically to cause significant upregulation of runt-related transcription factor 2 (RUNX2) protein and Runx2 gene expression in BMSCs on the F-BCS coating surface, which induced the transcription of downstream osteogenic differentiation marker genes. F-BCS coating allowed specific boron ion release, which favored angiogenesis as evidenced by the enhanced migration and tube formation of human umbilical vein endothelial cells in the coating extract. Boron-incorporated coatings significantly suppressed the expression of toll-like receptor adaptor genes in RAW264.7 macrophages and subsequently the degradation of nuclear factor-κB inhibitor α, accompanied by the inactivation of the downstream pro-inflammatory genes. In vivo experiments confirmed that F-BCS-coated Ti implant possessed enhanced osseointegration compared with L-BCS- and C-CS-coated implants. These data highlighted the synergistic effect of specific nanotopography and boron release from orthopedic implant coating on improvement of osseointegration.

Monitoring of canonical BMP and Wnt activities during postnatal stages of mouse first molar root formation

Objective This study aimed to explore the precise temporospatial distributions of bone morphogenetic protein (BMP) and Wnt signaling pathways during postnatal development of mammalian tooth roots after the termination of crown morphogenesis.Methodology A total of two transgenic mouse lines, BRE-LacZ mice and BAT-gal mice, were undertaken. The mice were sacrificed on every postnatal (PN) day from PN 3d up to PN 21d. Then, the first lower molars were extracted, and the dissected mandibles were stained with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-gal) and fixed. Serial sections at 10 µm were prepared after decalcification, dehydration, and embedding in paraffin.Results We observed BMP/Smads and Wnt/β-catenin signaling activities in the dental sac, dental pulp, and apical papilla with a certain degree of variation. The position of activation of the BMP/Smad signaling pathway was located more coronally in the early stage, which then gradually expanded as root elongation proceeded and was associated with blood vessels in the pulp and developing complex apical tissues in the later stage. However, Wnt/β-catenin signaling was highly concentrated in the mesenchyme below the cusps in the early stage, gradually expanded to regions around the root in the transition/root stage, and then disappeared entirely in the later stage.Conclusions These results further confirmed the participation of both BMP and Wnt canonical signaling pathways in tooth root development, as well as formed the basis for future studies on how precisely integrated signaling pathways regulate root morphogenesis and regeneration.

GPN-1/glypican and UNC-52/perlecan do not appear to function in BMP signaling to pattern the C. elegans postembryonic mesoderm.

Heparan sulfate proteoglycans (HSPGs) are diverse macromolecules consisting of a protein core modified with glycosaminoglycan (GAG) chains. HSPGs, including glypicans and perlecans, have been implicated in shaping the extracellular matrix (ECM) to affect growth factor signaling. Here, we tested if GPN-1/glypicanor UNC-52/perlecan plays a role in the bone morphogenetic protein (BMP) signaling pathway in patterning the C. elegans postembryonic mesoderm. Using the suppression of sma-9(0) (Susm)assay, we found that animals carrying mutant alleles of gpn-1 or unc-52 do not exhibit any Susm phenotype. We also tested and found that the two glypicans GPN-1 and LON-2 do not share functional redundancy in the BMP pathway. Our results suggest that GPN-1/glypican and UNC-52/perlecan do not play a major role in the C. elegans BMP pathway, at least in patterning of the postembryonic mesoderm.

Romidepsin hepatocellular carcinoma suppression in mice is associated with deregulated gene expression of bone morphogenetic protein and Notch signaling pathway components.

Recently, our group showed that Romidepsin, a histone deacetylase inhibitor (HDACi), suppressed diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) in mice. In the present study, we investigated the effect of Romidepsin-treatment on gene expression levels of components of Bmp and Notch signaling pathways, which are both known to be aberrantly regulated in hepatocarcinogenesis. Total RNA from liver tissue samples and paraffin-embedded livers were retrieved from a recent experiment where C57BL/6 mice were treated with Romidepsin 10months after DEN challenge and sacrificed 2months later. RT qPCR was used for quantification of gene expression and immunohistochemistry for in situ protein detection. Regarding Bmp pathway, Romidepsin HCC-suppression was found to correlate significantly with Bmp2 and Bmp7 ligand up- and down-regulation, respectively. Intracellularly, Romidepsin-treated HCC mice exhibited a significant elevation of Bmp-inhibitor Smurf2 and Bmp-target gene Id3, as compared to the HCC untreated controls. Concerning Notch signaling, higher expression levels of ligands Jag1/Dll4, accompanied by a decreased expression of receptor Notch2, were identified in the Romidepsin-treated group. Τhe anti-oncogenic effect of Romidepsin, also correlated significantly with an increased expression of Hes1 target, as well as an up- and down-regulation of Klf4 and Sox9 transcription factors, respectively. Moreover, the cancer-related genes Snai2 and p21, known to be involved in many signaling pathways, including Bmp and Notch, were also found to be downregulated in Romidepsin-treated mice. Romidepsin HCC suppression is associated with gene expression deregulation of selective components of both Bmp and Notch signaling cascades.

Critical role of astrogenesis and neurodevelopment in Fragile X Syndrome and Rett Syndrome

Astrocytes play an important role in the development of functional neural circuits in the brain. They are responsible for coordinating synapse formation and function, axon guidance, and ensuring neuronal survival. Normal astrogenesis begins during late gestation. Neural stem cells (NSCs) become primarily gliogenic and differentiate to become astrocyte precursors. Through local proliferation and functional maturation, the precursors develop into mature astrocytes, which can either be fibrous or protoplasmic. Astrogenesis is regulated by both cell intrinsic programs and cell extrinsic cues. Intrinsic chromatin changes, such as demethylation of astrocyte-specific genes, allows the NSCs to become responsive to astrocyte-inducing exogenous cues. These cues involve a collaboration of multiple pathways, namely the Notch pathway, the bone morphogenetic protein (BMP) signaling pathway, interleukin-6 (IL-6) signaling, and the Janus Kinase/Signal Transducer and Activator of Transcription (JAK-STAT) pathway. Together, they allow for normal astrogenesis to occur. However, disruption to these pathways lead to abnormal astrocyte development and results in pathologies such as the Fragile X Syndrome (FXS) and Rett Syndrome (RS). Both neurodevelopmental disorders are a result of genetic mutations that causes either transcriptional silence or transcriptional activation at inappropriate stages during development. These genetic mutations result in depressed astrocyte function in FXS, and the overexcitement of astrocytes in RS. The current hypothesis under investigation is that altered gene transcription during neurodevelopment disrupts astrogenesis, and subsequently, the behavior and function of mature astrocytes in the brain. Future research should focus on understanding the timing of the transition from neurogenesis to astrogenesis and identifying astrocyte-specific markers that are critical to its function in neurodevelopment.

Xenopus gpx3 Mediates Posterior Development by Regulating Cell Death during Embryogenesis.

Glutathione peroxidase 3 (GPx3) belongs to the glutathione peroxidase family of selenoproteins and is a key antioxidant enzyme in multicellular organisms against oxidative damage. Downregulation of GPx3 affects tumor progression and metastasis and is associated with liver and heart disease. However, the physiological significance of GPx3 in vertebrate embryonic development remains poorly understood. The current study aimed to investigate the functional roles of gpx3 during embryogenesis. To this end, we determined gpx3’s spatiotemporal expression using Xenopus laevis as a model organism. Using reverse transcription polymerase chain reaction (RT-PCR), we demonstrated the zygotic nature of this gene. Interestingly, the expression of gpx3 enhanced during the tailbud stage of development, and whole mount in situ hybridization (WISH) analysis revealed gpx3 localization in prospective tail region of developing embryo. gpx3 knockdown using antisense morpholino oligonucleotides (MOs) resulted in short post-anal tails, and these malformed tails were significantly rescued by glutathione peroxidase mimic ebselen. The gene expression analysis indicated that gpx3 knockdown significantly altered the expression of genes associated with Wnt, Notch, and bone morphogenetic protein (BMP) signaling pathways involved in tailbud development. Moreover, RNA sequencing identified that gpx3 plays a role in regulation of cell death in the developing embryo. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and phospho-histone 3 (PH3) staining confirmed the association of gpx3 knockdown with increased cell death and decreased cell proliferation in tail region of developing embryos, establishing the involvement of gpx3 in tailbud development by regulating the cell death. Furthermore, these findings are inter-related with increased reactive oxygen species (ROS) levels in gpx3 knockdown embryos, as measured by using a redox-sensitive fluorescent probe HyPer. Taken together, our results suggest that gpx3 plays a critical role in posterior embryonic development by regulating cell death and proliferation during vertebrate embryogenesis.

Stem cell and niche regulation in human short bowel syndrome.

Loss of functional small bowel surface area following surgical resection for disorders such as Crohn’s disease, intestinal ischemic injury, radiation enteritis, and in children, necrotizing enterocolitis, atresia, and gastroschisis, may result in short bowel syndrome, with attendant high morbidity, mortality, and health care costs in the United States. Following resection, the remaining small bowel epithelium mounts an adaptive response, resulting in increased crypt cell proliferation, increased villus height, increased crypt depth, and enhanced nutrient and electrolyte absorption. Although these morphologic and functional changes are well described in animal models, the adaptive response in humans is less well understood. Clinically the response is unpredictable and often inadequate. Here we address the hypotheses that human intestinal stem cell populations are expanded and that the stem cell niche is regulated following massive gut resection in short bowel syndrome (SBS). We use intestinal enteroid cultures from patients with SBS to show that the magnitude and phenotype of the adaptive stem cell response are both regulated by stromal niche cells, including intestinal subepithelial myofibroblasts, which are activated by intestinal resection to enhance epithelial stem and proliferative cell responses. Our data suggest that myofibroblast regulation of bone morphogenetic protein signaling pathways plays a role in the gut adaptive response after resection.

Effect of Tumor Growth Factor-β on Osteogenesis in Osteoporosis Rats by Regulating Bone Morphogenetic Protein Signaling Pathway

The balance of osteoblasts and osteoclasts is critical for bone formation and remodeling and imbalance causes osteoporosis (OP). TGF-β regulates bone tissue repair and regeneration, but TGF-β’s role in osteogenesis in OP has not been elucidated. OVX-induced OP rat models were constructed and rat BMSCs were isolated and assigned into control group, OP group, and TGF-β group (transfected with TGF-β1 plasmid followed by analysis of cell proliferation by MTT assay, RUNX2 and OPN expression by Real time PCR, ALP activity and secretion of TGF-β, BMP-2 and BMP-9 by ELISA. In addition, RANKL was added to induce BMSCs differentiation into to osteoclasts which were transfected with TGF-β1 followed by analysis of cell proliferation, c-Fos and TRAP expression and secretion of BMP-2 and BMP-9. OP group rats had significantly reduced secretion of TGF-β1, BMP-2 and BMP-9, reduced cell proliferation, decreased RUNX2 and OPN expression and ALP activity (P <0.05). Transfection of TGF-β1 in BMSCs of OP group rats could significantly reverse the above changes (P <0.05). TGF-β1 significantly inhibited osteoclast proliferation, decreased expression of c-Fos and TRAP, and increased secretion of BMP-2 and BMP-9 (P <0.05). TGF-β1 level in OP is decreased. Up-regulating TGF-β promotes osteoblast differentiation in OP rats by regulating BMP signaling pathway, and inhibits osteoclast proliferation and differentiation.

Wnt1 boosts fracture healing by enhancing bone formation in the fracture callus.

Despite considerable improvement in fracture care, 5-10% of all fractures still heal poorly or result in non-union formation. Therefore, there is the urgent need to identify new molecules that can be used to improve bone fracture healing. One activator of the Wnt-signaling cascade, Wnt1, has recently gained attention for its intense osteoanabolic effect on the intact skeleton. The aim of the present study was to investigate whether Wnt1 might be a promising molecule to accelerate fracture healing both in skeletally healthy and osteoporotic mice that display a diminished healing capacity. Transgenic mice for a temporary induction of Wnt1 specifically in osteoblasts (Wnt1tg) were subjected to femur osteotomy. Non-ovariectomized and ovariectomized Wnt1tg mice displayed significantly accelerated fracture healing based on a strong increase in bone formation in the fracture callus. Transcriptome profiling revealed that Hippo/YAP-signaling and BMP-signaling pathways were highly enriched in the fracture callus of Wnt1tg animals. Immunohistochemical staining confirmed increased activation of YAP1 and expression of BMP2 in osteoblasts in the fracture callus. Therefore, our data indicate that Wnt1 boosts bone formation during fracture healing via YAP/BMP signaling both under healthy and osteoporotic conditions. To further test a potential translational application of Wnt1, we applied recombinant Wnt1 embedded into a collagen gel during critical size bone defect repair. Mice treated with Wnt1 displayed increased bone regeneration compared to control mice accompanied by increased YAP1/BMP2 expression in the defect area. These findings are of high clinical relevance because they indicate that Wnt1 could be used as a new therapeutic agent to treat orthopaedic complications in the clinic.

Functional Testing of Bone Morphogenetic Protein (BMP) Pathway Variants Identified on Whole-Exome Sequencing in a Patient with Delayed-Onset Fibrodysplasia Ossificans Progressiva (FOP) Using ACVR1R206H -Specific Human Cellular and Zebrafish Models.

Bone morphogenetic protein (BMP) signaling is critical in skeletal development. Overactivation can trigger heterotopic ossification (HO) as in fibrodysplasia ossificans progressiva (FOP), a rare, progressive disease of massive HO formation. A small subset of FOP patients harboring the causative ACVR1R206H mutation show strikingly mild or delayed-onset HO, suggesting that genetic variants in the BMP pathway could act as disease modifiers. Whole-exome sequencing of one such patient identified BMPR1AR443C and ACVR2AV173I as candidate modifiers. Molecular modeling predicted significant structural perturbations. Neither variant decreased BMP signaling in ACVR1R206H HEK 293T cells at baseline or after stimulation with BMP4 or activin A (AA), ligands that activate ACVR1R206H signaling. Overexpression of BMPR1AR443C in a Tg(ACVR1-R206Ha) embryonic zebrafish model, in which overactive BMP signaling yields ventralized embryos, did not alter ventralization severity, while ACVR2AV173I exacerbated ventralization. Co-expression of both variants did not affect dorsoventral patterning. In contrast, BMPR1A knockdown in ACVR1R206H HEK cells decreased ligand-stimulated BMP signaling but did not affect dorsoventral patterning in Tg(ACVR1-R206Ha) zebrafish. ACVR2A knockdown decreased only AA-stimulated signaling in ACVR1R206H HEK cells and had no effect in Tg(ACVR1-R206Ha) zebrafish. Co-knockdown in ACVR1R206H HEK cells decreased basal and ligand-stimulated signaling, and co-knockdown/knockout (bmpr1aa/ab; acvr2aa/ab) decreased Tg(ACVR1-R206Ha) zebrafish ventralization phenotypes. Our functional studies showed that knockdown of wild-type BMPR1A and ACVR2A could attenuate ACVR1R206H signaling, particularly in response to AA, and that ACVR2AV173I unexpectedly increased ACVR1R206H -mediated signaling in zebrafish. These studies describe a useful strategy and platform for functionally interrogating potential genes and genetic variants that may impact the BMP signaling pathway. © 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).

Involvement of circRNA_0007059 in the regulation of postmenopausal osteoporosis by promoting the microRNA-378/BMP-2 axis.

Increasing evidence suggests that postmenopausal osteoporosis (PMO), a severe disturbance, imposes heavy physical, psychosocial, and financial burdens and dramatically influences the quality of life of postmenopausal women. Circular RNAs (circRNAs) and microRNAs (miRs) play important roles in the occurrence and development of PMO. However, the roles of circRNAs and miRs in osteoporosis regulation still need to be further investigated. circRNAs with different expression levels in patients with PMO were screened via RNA-seq and bioinformatics analysis. We found that circ_0007059 was upregulated in patients with PMO and during osteoclastogenesis of human bone marrow stromal cells (hBMSCs). Next, we investigated the effect of circ_0007059 overexpression during osteoclastogenesis of hBMSCs. circ_0007059 overexpression attenuated hBMSC differentiation into osteoclasts in vitro. This was demonstrated by downregulated bone morphogenetic protein 2 (BMP-2) expression, upregulated osteoclast-specific gene expression, and TRAP staining. circ_0007059 was demonstrated to directly target miR-378, which in turn targeted BMP-2 via bioinformatics analysis and the dual-luciferase reporter assay. Transfection of the miR-378 mimic reversed the effect of circ_0007059 on the osteoclastogenesis of hBMSCs. These results suggest that circ_0007059 plays an important role in osteoclastogenesis via the miR-378/BMP-2 signaling pathway. Targeting the circ_0007059/miR-378/BMP-2 axis is possibly a novel idea in osteoporosis treatment.

At the X-Roads of Sex and Genetics in Pulmonary Arterial Hypertension.

Group 1 pulmonary hypertension (pulmonary arterial hypertension; PAH) is a rare disease characterized by remodeling of the small pulmonary arteries leading to progressive elevation of pulmonary vascular resistance, ultimately leading to right ventricular failure and death. Deleterious mutations in the serine-threonine receptor bone morphogenetic protein receptor 2 (BMPR2; a central mediator of bone morphogenetic protein (BMP) signaling) and female sex are known risk factors for the development of PAH in humans. In this narrative review, we explore the complex interplay between the BMP and estrogen signaling pathways, and the potentially synergistic mechanisms by which these signaling cascades increase the risk of developing PAH. A comprehensive understanding of these tangled pathways may reveal therapeutic targets to prevent or slow the progression of PAH.

High expression of bone morphogenetic protein 1 (BMP1) is associated with a poor survival rate in human gastric cancer, a dataset approaches

Bone morphogenetic protein 1 (BMP1) is a secreted metalloprotease of the astacin M12A family of bone morphogenetic proteins (BMPs). BMP1 activates transforming growth factor-β (TGF-β) and BMP signaling pathways by proteolytic cleavage, which has dual roles in gastrointestinal tumor development and progression.TGF-β promotes invasion and metastasis of gastric cancer (GC) by the help of BMP1, so upregulation of the BMP1 may increase cancer invasiveness in GC. In this study,the transcriptional expression, mutations, survival rate, TFs, miRNAs, gene ontology, and signaling pathways of BMP1 were analyzed by using different web servers. We found higher transcriptional and clinicopathological characteristics expression compared to normal tissues, worsening survival rate in GC. We detected 25 missenses, 15 truncating mutations, 23 TFs, and 8 miRNAs. Finally, we identified and analyzed the co-expressed genes and found that the leukemia inhibitory factor is the most positively correlated gene. The gene ontological features and signaling pathways involved in GC development were evaluated as well. We believe that this study will provide a basis for BMP1 to be a significant biomarker for human GC prognosis.