Bone morphogenetic proteins and their antagonists: current and emerging clinical uses

Effect of the TGF-β/BMP Signaling Pathway on the Proliferation of Yak Pulmonary Artery Smooth Muscle Cells under Hypoxic Conditions

To survive in low-oxygen environments, yaks effectively avoid hypoxia-induced pulmonary arterial hypertension through vascular remodeling. The TGF-β/BMP signaling pathway plays a key role in maintaining the homeostasis of pulmonary artery smooth muscle cells (PASMCs). However, little is known about the molecular regulatory mechanisms by which the TGF-β/BMP signaling pathway contributes to the proliferation of yak PASMCs. In this study, yak PASMCs were cultured in vitro, and a hypoxia model was constructed to investigate the effect of TGFβ/BMP signaling on yak PASMC proliferation. Hypoxia treatment increased the proliferation of yak PASMCs significantly. As the duration of hypoxia increased, the expression levels of TGF-β1 and the phosphorylation levels of Smad2/3 were upregulated significantly. The BMP signaling pathway was transiently activated by hypoxia, with increases in BMPR2 expression and Smad1/5 phosphorylation, and these changes were gradually reversed with prolonged hypoxia exposure. In addition, exogenous TGF-β1 activated the TGF-β signaling pathway, increased the phosphorylation levels of the downstream proteins Smad2 and Smad3, and increased the proliferation and migration rates of yak PASMCs significantly. Finally, treatment with noggin (an inhibitor of BMP signaling) significantly reduced BMPR2 protein expression levels and Smad1/5 phosphorylation levels and increased yak PASMC proliferation and migration rates. In summary, these results revealed that under hypoxic conditions, the dynamic regulation of the TGF-β/BMP signaling pathway promotes the proliferation of yak PASMCs.

Therapeutic Potential of Quercetin as an Antioxidant for Bone-Muscle-Tendon Regeneration and Aging

Quercetin (QC), a naturally occurring bioflavonoid found in various fruits and vegetables, possesses many potential health benefits, primarily attributed to its robust antioxidant properties. The generation of oxidative stress in bone cells is a key modulator of their physiological behavior. Moreover, oxidative stress status influences the pathophysiology of mineralized tissues. Increasing scientific evidence demonstrates that manipulating the redox balance in bone cells might be an effective technique for developing bone disease therapies. The QC antioxidant abilities in skeletal muscle significantly enhance muscle regeneration and reduce muscle atrophy. In addition, QC has been shown to have protective effects against oxidative stress, inflammation, apoptosis, and matrix degradation in tendons, helping to maintain the structural integrity and functionality of tendons. Thus, the antioxidant properties of QC might be crucial for addressing age-related musculoskeletal disorders like osteoporosis, sarcopenia, and tendon-related inflammatory conditions. Understanding how QC influences redox signaling pathways involved in musculoskeletal disorders, including their effect on bone, muscle, and tendon differentiation, might provide insights into the diverse advantages of QC in promoting tissue regeneration and preventing cellular damage. Therefore, this study reviewed the intricate relationship among oxidative stress, inflammation, and tissue repair, affected by the antioxidative abilities of QC, in age-related musculoskeletal tissues to improve the overall health of bones, muscles, and tendons of the skeletal system. Also, reviewing the ongoing clinical trials of QC for musculoskeletal systems is encouraging. Given the positive effect of QC on musculoskeletal health, further scientific investigations and controlled human intervention studies are necessary to explore the therapeutic potential to its optimum strength.

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Lysyl Oxidase Regulates Epithelial Differentiation and Barrier Integrity in Eosinophilic Esophagitis

BACKGROUND & AIMS

Epithelial disruption in eosinophilic esophagitis (EoE) encompasses both impaired differentiation and diminished barrier integrity. We have shown that lysyl oxidase (LOX), a collagen cross-linking enzyme, is up-regulated in the esophageal epithelium in EoE. However, the functional roles of LOX in the esophageal epithelium remains unknown.

METHODS

We investigated roles for LOX in the human esophageal epithelium using 3-dimensional organoid and air-liquid interface cultures stimulated with interleukin (IL)13 to recapitulate the EoE inflammatory milieu, followed by single-cell RNA sequencing, quantitative reverse-transcription polymerase chain reaction, Western blot, histology, and functional analyses of barrier integrity.

RESULTS

Single-cell RNA sequencing analysis on patient-derived organoids revealed that LOX was induced by IL13 in differentiated cells. LOX-overexpressing organoids showed suppressed basal and up-regulated differentiation markers. In addition, LOX overexpression enhanced junctional protein genes and transepithelial electrical resistance. LOX overexpression restored the impaired differentiation and barrier function, including in the setting of IL13 stimulation. Transcriptome analyses on LOX-overexpressing organoids identified an enriched bone morphogenetic protein (BMP) signaling pathway compared with wild-type organoids. In particular, LOX overexpression increased BMP2 and decreased the BMP antagonist follistatin. Finally, we found that BMP2 treatment restored the balance of basal and differentiated cells.

CONCLUSIONS

Our data support a model whereby LOX exhibits noncanonical roles as a signaling molecule important for epithelial homeostasis in the setting of inflammation via activation of the BMP pathway in the esophagus. The LOX/BMP axis may be integral in esophageal epithelial differentiation and a promising target for future therapies.

The inhibitory effect of Gremlin-2 on adipogenesis suppresses breast cancer cell growth and metastasis

BACKGROUND

Gremlin-1 (GREM1) and Gremlin-2 (GREM2) are bone morphogenetic protein antagonists that play important roles in organogenesis, tissue differentiation, and tissue homeostasis. Although GREM1 has been reported to be involved in promoting various cancers, little has been reported about effects of GREM2 on cancer. Recently, it has been reported that GREM2 can inhibit adipogenesis in adipose-derived stromal/stem cells. However, as an inhibitor of adipogenesis, the role of GREM2 in cancer progression is not well understood yet.

METHODS

Pre-adipocyte 3T3-L1 cells overexpressing mock or Grem2 were established using a lentiviral transduction system and differentiated into adipocytes-mock and adipocytes-Grem2, respectively. To investigate the effect of adipocyte-Grem2 on breast cancer cells, we analyzed the proliferative and invasion abilities of spheroids using a 3D co-culture system of breast cancer cells and adipocytes or conditioned medium (CM) of adipocytes. An orthotopic breast cancer mouse model was used to examine the role of adipocytes-Grem2 in breast cancer progression.

RESULTS

Grem2 overexpression suppressed adipogenesis of 3T3-L1 cells. Proliferative and invasion abilities of spheroids formed by co-culturing MTV/TM-011 breast cancer cells and adipocytes-Grem2 were significantly reduced compared to those of spheroids formed by co-culturing MTV/TM-011 cells and adipocytes-mock. Compared to adipocytes-mock, adipocytes-Grem2 showed decreased mRNA expression of several adipokines, notably IL-6. The concentration of IL-6 in the CM of these cells was also decreased. Proliferative and invasive abilities of breast cancer cells reduced by adipocytes-Grem2 were restored by IL-6 treatment. Expression levels of vimentin, slug, and twist1 in breast cancer cells were decreased by treatment with CM of adipocytes-Grem2 but increased by IL-6 treatment. In orthotopic breast cancer mouse model, mice injected with both MTV/TM-011 cells and adipocytes-Grem2 showed smaller primary tumors and lower lung metastasis than controls. However, IL-6 administration increased both the size of primary tumor and the number of metastatic lung lesions, which were reduced by adipocytes-Grem2.

CONCLUSIONS

Our study suggests that GREM2 overexpression in adipocytes can inhibit adipogenesis, reduce the expression and secretion of several adipokines, including IL-6, and ultimately inhibit breast cancer progression.

Regeneration of Critical-Sized Mandibular Defects Using 3D-Printed Composite Scaffolds: A Quantitative Evaluation of New Bone Formation in In Vivo Studies

Mandibular tissue engineering aims to develop synthetic substitutes for the regeneration of critical size defects (CSD) caused by a variety of events, including tumor surgery and post-traumatic resections. Currently, the gold standard clinical treatment of mandibular resections (i.e., autologous fibular flap) has many drawbacks, driving research efforts toward scaffold design and fabrication by additive manufacturing (AM) techniques. Once implanted, the scaffold acts as a support for native tissue and facilitates processes that contribute to its regeneration, such as cells infiltration, matrix deposition and angiogenesis. However, to fulfil these functions, scaffolds must provide bioactivity by mimicking natural properties of the mandible in terms of structure, composition and mechanical behavior. This review aims to present the state of the art of scaffolds made with AM techniques that are specifically employed in mandibular tissue engineering applications. Biomaterials chemical composition and scaffold structural properties are deeply discussed, along with strategies to promote osteogenesis (i.e., delivery of biomolecules, incorporation of stem cells, and approaches to induce vascularization in the constructs). Finally, a comparison of in vivo studies is made by taking into consideration the amount of new bone formation (NB), the CSD dimensions, and the animal model.

Post-Transcriptional Regulatory Crosstalk between MicroRNAs and Canonical TGF-β/BMP Signalling Cascades on Osteoblast Lineage: A Comprehensive Review

MicroRNAs (miRNAs) are a family of small, single-stranded, and non-protein coding RNAs about 19 to 22 nucleotides in length, that have been reported to have important roles in the control of bone development. MiRNAs have a strong influence on osteoblast differentiation through stages of lineage commitment and maturation, as well as via controlling the activities of osteogenic signal transduction pathways. Generally, miRNAs may modulate cell stemness, proliferation, differentiation, and apoptosis by binding the 3'-untranslated regions (3'-UTRs) of the target genes, which then can subsequently undergo messenger RNA (mRNA) degradation or protein translational repression. MiRNAs manage the gene expression in osteogenic differentiation by regulating multiple signalling cascades and essential transcription factors, including the transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP), Wingless/Int-1(Wnt)/β-catenin, Notch, and Hedgehog signalling pathways; the Runt-related transcription factor 2 (RUNX2); and osterix (Osx). This shows that miRNAs are essential in regulating diverse osteoblast cell functions. TGF-βs and BMPs transduce signals and exert diverse functions in osteoblastogenesis, skeletal development and bone formation, bone homeostasis, and diseases. Herein, we highlighted the current state of in vitro and in vivo research describing miRNA regulation on the canonical TGF-β/BMP signalling, their effects on osteoblast linage, and understand their mechanism of action for the development of possible therapeutics. In this review, particular attention and comprehensive database searches are focused on related works published between the years 2000 to 2022, using the resources from PubMed, Google Scholar, Scopus, and Web of Science.

Lysyl oxidase regulates epithelial differentiation and barrier integrity in eosinophilic esophagitis

Background & Aims

Epithelial disruption in eosinophilic esophagitis (EoE) encompasses both impaired differentiation and diminished barrier integrity. We have shown that lysyl oxidase (LOX), a collagen cross-linking enzyme, is upregulated in the esophageal epithelium in EoE. However, the functional roles of LOX in the esophageal epithelium remains unknown.

Methods

We investigated roles for LOX in the human esophageal epithelium using 3-dimensional organoid and air-liquid interface cultures stimulated with interleukin (IL)-13 to recapitulate the EoE inflammatory milieu, followed by single-cell RNA sequencing, quantitative reverse transcription-polymerase chain reaction, western blot, histology, and functional analyses of barrier integrity.

Results

Single-cell RNA sequencing analysis on patient-derived organoids revealed that LOX was induced by IL-13 in differentiated cells. LOX-overexpressing organoids demonstrated suppressed basal and upregulated differentiation markers. Additionally, LOX overexpression enhanced junctional protein genes and transepithelial electrical resistance. LOX overexpression restored the impaired differentiation and barrier function, including in the setting of IL-13 stimulation. Transcriptome analyses on LOX-overexpressing organoids identified enriched bone morphogenetic protein (BMP) signaling pathway compared to wild type organoids. Particularly, LOX overexpression increased BMP2 and decreased BMP antagonist follistatin. Finally, we found that BMP2 treatment restored the balance of basal and differentiated cells.

Conclusions

Our data support a model whereby LOX exhibits non-canonical roles as a signaling molecule important for epithelial homeostasis in the setting of inflammation via activation of BMP pathway in esophagus. The LOX/BMP axis may be integral in esophageal epithelial differentiation and a promising target for future therapies.

Improving bone morphogenetic protein (BMP) production in CHO cells through understanding of BMP synthesis, signaling and endocytosis

Bone morphogenetic proteins (BMPs) are a group of growth factors with the clinical potential to regulate cartilage and bone formation. Functionally active mature recombinant human BMPs (rhBMPs), produced primarily in Chinese hamster ovary (CHO) cells for clinical applications, are considered difficult to express because they undergo maturation processes, signaling pathways, or endocytosis. Although BMPs are a family of proteins with similar mature domain sequence identities, their individual properties are diverse. Thus, understanding the properties of individual rhBMPs is essential to improve rhBMP production in CHO cells. In this review, we discuss various approaches to improve rhBMP production in CHO cells by understanding the overall maturation process, signaling pathways and endocytosis of individual rhBMPs.

The association of polymorphisms in BMP2/MYO1H and skeletal Class II div.1 maxillary and mandibular dimensions. A preliminary ‘report

Introduction

The genetic impact directly or indirectly predefines maxillofacial dimensions, potentially leading to an inappropriate relationship of the jaws and subsequently skeletal malocclusion. Previous studies focused mainly on genetic polymorphisms and class III malocclusion. This study was set out to investigate the association between genetic polymorphisms in two genes BMP2 (rs235768) and MYO1H (rs11066446) with Class II division 1 malocclusion, skeletal variation in vertical plane, and maxillary and mandibular jaws length.

Subjects and methods

Sixty patients classified as Skeletal Class I (n = 30) and Class II division 1 (n = 30) were recruited. DNA was extracted from saliva and analyzed by Sanger sequencing. Lateral cephalometric radiographs were measured for the anterio-posterior relationship of maxillary and mandibular arch using digital tracing. Hardy-Weinberg equilibrium analysis of genotype frequencies was performed using Chi-square test to compare genotype distribution among groups and multiple logistic regression analysis adjusted by gender was also performed.

Results

The rs235768 polymorphism in BMP2 was associated with hypodivergent face, increased maxillary length, and decreased mandibular length. Meanwhile, the rs11066446 polymorphism in MYO1H was associated with decreased mandibular length. New polymorphism was identified in MYO1H (rs10850090) in association with decreased mandibular length.

Conclusion

A potential association between polymorpisms in BMP2 rs235768 and MOY1H rs11066446 and rs10850090 and Class II division 1 skeletal malocclusion related phenotypes exists, however, the degree of it has to be further investigated and yet to be discovered.

Discovery of a novel class of benzimidazoles as highly effective agonists of bone morphogenetic protein (BMP) receptor signaling

Increasing or restoring Bone Morphogenetic Protein receptor signaling is an effective therapy for conditions such as bone fracture and pulmonary arterial hypertension. However, direct use of recombinant BMPs has encountered significant obstacles. Moreover, synthetic, full agonists of BMP receptor signaling have yet to be identified. Here, we report the discovery of a novel class of indolyl-benzimidazoles, synthesized using a one-pot synthetic methodology, which appear to mimic the biochemical and functional activity of BMPs. The first-in-series compounds, SY-LB-35 and SY-LB-57, stimulated significant increases in cell number and cell viability in the C2C12 myoblast cell line. Cell cycle analysis revealed that these compounds induced a shift toward proliferative phases. SY-LB-35 and SY-LB-57 stimulated canonical Smad and non-canonical PI3K/Akt, ERK, p38 and JNK intracellular signaling pathways, similar to BMP2-stimulated responses. Importantly, increases in Smad phosphorylation and cell viability were dependent on type I BMP receptor activity. Thus, these compounds robustly activate intracellular signaling in a BMP receptor-dependent manner and may signify the first known, full agonists of BMP receptor signaling. Moreover, discovery of small molecule activators of BMP pathways, which can be efficiently formulated and targeted to diseased or damaged areas, could potentially substitute recombinant BMPs for treatment of BMP-related pathologies.

Structural Mapping of BMP Conformational Epitopes and Bioengineering Design of Osteogenic Peptides to Specifically Target the Epitope-Binding Sites

Introduction

Human bone morphogenetic proteins (BMPs) constitute a large family of cytokines related to members of the transforming growth factor-β superfamily, which fulfill biological functions by specificity binding to their cognate type I (BRI) and type II (BRII) receptors through conformational wrist and linear knuckle epitopes, respectively.

Methods and Results

We systematically examined the intermolecular recognition and interaction between the BMP proteins and BRI receptor at structural, energetic and dynamic levels. The BRI-binding site consists of three hotspot regions on BMP surface, which totally contribute ~70% potency to the BMP-BRI binding events and represent the core sections of BMP conformational wrist epitope; the contribution increases in the order: hotspot 2 (~ 8%) < hotspot 3 (~ 20%) < hotspot 1 (~ 40%). Multiple sequence alignment and structural superposition revealed a consensus sequence pattern and a similar binding mode of the three hotspots shared by most BMP members, indicating a high conservation of wrist epitope in BMP family. The three hotspots are natively folded into wellstructured U-shaped,, loop and double-stranded conformations in BMP proteins, which, however, would become largely disordered when splitting from the protein context to derive osteogenic peptides in free state, thus largely impairing their rebinding capability to BRI receptor. In this respect, cyclization strategy was employed to constrain hotspot 1/3-derived peptides into a native-like conformation, which was conducted by adding a disulfide bond across the ending arms of linear peptides based on their native conformations. Fluorescence-based assays substantiated that the cyclization can effectively improve the binding affinities of osteogenic peptides to BRI receptor by 3-6-fold. The cyclic peptides also exhibit a good selectivity for BRI over BRII (> 5-fold), confirming that they can specifically target the wrist epitope-binding site of BRI receptor.

Conclusion

The rationally designed cyclic peptides can be regarded as the promising lead entities that should be further chemically modified to enhance their in vivo biological stability for further bioengineering therapeutic osteogenic peptides against chondrocyte senescence and bone disorder.

Biology of Bone Morphogenetic Proteins in Skeleton Disease: Osteonecrosis in Sickle Cell Disease Patients

Abstract:

Sickle cell disease (SCD) is an autosomal recessive trait of genetic hemoglobin disorder whose prevalence is varied from 5 to 25 % of the world population. It is characterized by the presence of hemoglobin (HbS) instead of normal hemoglobin (HbA). An individual suffering from sickle cell disease is likely to be at risk of osteonecrosis which is a form of ischemic bone infarction which causes intolerable degenerative joint problems and can affect 30-50% of people with sickle cell disease. The femoral head is the most frequent epiphyseal location in osteonecrosis with sickle cell disease. In this review, the Bone morphogenetic protein (BMP)-a subfamily of transforming growth factor-β (TGF-β) characteristics, outlined the osteoblastogenesis potentiality via using combinatorial or advanced treatment approaches. In this review, we aim to describe the Bone morphogenetic proteins' role in Skeleton diseases and discuss the potent osteogenic BMPs (majorly BMP-2, BMP-6, and BMP-7) with therapeutic benefits.

miR-122-5p targets GREM2 to protect against glucocorticoid-induced endothelial damage through the BMP signaling pathway

Glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH) accounts for a big portion of non-traumatic ONFH; nevertheless, the pathogenesis has not yet been fully understood. GC-induced endothelial dysfunction might be a major contributor to ONFH progression. The Gene Expression Omnibus (GEO) dataset was analyzed to identify deregulated miRNAs in ONFH; among deregulated miRNAs, the physiological functions of miR-122-5p on ONFH and endothelial dysfunction remain unclear. In the present study, miR-122-5p showed to be under-expressed within GC-induced ONFH femoral head tissues and GC-stimulated bone microvascular endothelial cells (BMECs). In human umbilical vein endothelial cells (HUVECs) and BMECs, GC stimulation significantly repressed cell viability, promoted cell apoptosis and increased the mRNA expression of proinflammatory cytokines, such as TNF-α, IL-1β, and IFN-γ. After overexpressing miR-122-5p, GC-induced endothelial injuries were attenuated, as manifested by rescued cell viability, cell migration, and tube formation capacity. Regarding the BMP signaling, GC decreased the protein levels of BMP-2/6/7 and SMAD-1/5/8, whereas miR-122-5p overexpression significantly attenuated the inhibitory effects of GC on these proteins. Online tool and experimental analyses revealed the direct binding between miR-122-5p and GREM2, a specific antagonist of BMP-2. In contrast to miR-122-5p overexpression, GREM2 overexpression aggravated GC-induced endothelial injury; GREM2 silencing partially eliminated the effects of miR-122-5p inhibition on GC-stimulated HUVECs and BMECs. Finally, GREM2 silencing reversed the suppressive effects of GC on BMP-2/6/7 and SMAD-1/5/8, and attenuated the effects of miR-122-5p inhibition on these proteins upon GC stimulation. Conclusively, the present study demonstrates a miR-122-5p/GREM2 axis modulating the GC-induced endothelial damage via the BMP/SMAD signaling. Considering the critical role of endothelial function in ONFH pathogenesis, the in vivo role and clinical application of the miR-122-5p/GREM2 axis is worthy of further investigation.

Effect of BMP6 on the proliferation and apoptosis of chicken chondrocytes induced by thiram

The development of skeleton system is a complex biological process and be regulated by many transcription factors. Previous studies have shown that BMP6 is involved in skeleton development and other cells transforming to chondrocytes, but it is still not known whether do something to tibial dyschondroplasia (TD) broilers chondrocytes. In this study, RT-PCR revealed that the expression level of BMP6 in TD broiler chondrocytes at 7 days age was significantly decreased compared with normal group (P < 0.05). CCK-8 and EdU assay showed that the proliferation of cells transfected with interference BMP6 was significantly decreased compared with control siRNA, while cell proliferation was significantly increased after overexpression of BMP6. Meanwhile, the proportion of G0/G1 phase cells was significantly increased and the proportion of G2/M phase cells was significantly decreased after interference of BMP6 for 48 h in TD chicken chondrocytes (P < 0.05). In addition, flow cytometry analysis exhibited that interference BMP6 significantly increased apoptosis rate and necrotizing rate of cells. In conclusion, these results suggest that BMP6 plays a positive role in the growth and development of TD broiler chondrocytes. Our findings reveal a new target for TD prevention in broiler chickens.

The Role of BMP Signaling in Female Reproductive System Development and Function

Bone morphogenetic proteins (BMPs) are a group of multifunctional growth factors that belong to the transforming growth factor-β (TGF-β) superfamily of proteins. Originally identified by their ability to induce bone formation, they are now known as essential signaling molecules that regulate the development and function of the female reproductive system (FRS). Several BMPs play key roles in aspects of reproductive system development. BMPs have also been described to be involved in the differentiation of human pluripotent stem cells (hPSCs) into reproductive system tissues or organoids. The role of BMPs in the reproductive system is still poorly understood and the use of FRS tissue or organoids generated from hPSCs would provide a powerful tool for the study of FRS development and the generation of new therapeutic perspectives for the treatment of FRS diseases. Therefore, the aim of this review is to summarize the current knowledge about BMP signaling in FRS development and function.

The Organizer and Its Signaling in Embryonic Development

Germ layer specification and axis formation are crucial events in embryonic development. The Spemann organizer regulates the early developmental processes by multiple regulatory mechanisms. This review focuses on the responsive signaling in organizer formation and how the organizer orchestrates the germ layer specification in vertebrates. Accumulated evidence indicates that the organizer influences embryonic development by dual signaling. Two parallel processes, the migration of the organizer’s cells, followed by the transcriptional activation/deactivation of target genes, and the diffusion of secreting molecules, collectively direct the early development. Finally, we take an in-depth look at active signaling that originates from the organizer and involves germ layer specification and patterning.

Berberine for bone regeneration: Therapeutic potential and molecular mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Berberine is a quaternary ammonium isoquinoline alkaloid, mainly extracted from plants berberaceae, papaveraceae, ranunculaceae and rutaceae such as coptis chinensis Franch, Phellodendron chinense, and berberis pruinosa. The plants are extensively used in traditional medicine for treating infection, diabetes, arrhythmia, tumor, osteoporosis et al. Pharmacological studies showed berberine has effects of anti-inflammation, anti-tumor, lower blood lipid, lower blood glucose, anti-osteoporosis, anti-osteoarthritis et al. AIM OF THE STUDY: This review aims to summarize the application of natural herbs that contain berberine, the further use and development of berberine, the effects as well as mechanism of berberine on osteoblasts and osteoclasts, the recent advances of in vivo studies, in order to provide a scientific basis for its traditional uses and to prospect of the potential applications of berberine in clinics.

METHOD

The research was achieved by retrieving from the online electronic database, including PubMed, Web of Science, Google Scholar and China national knowledge infrastructure (CNKI). Patents, doctoral dissertations and master dissertations are also searched.

RESULTS

Berberine has a long history of medicinal use to treat various diseases including bone disease in China. Recent studies have defined its function in promoting bone regeneration and great potential in developing new drugs. But the systemic mechanism of berberine on bone regeneration still needs more research to clarify.

CONCLUSION

This review has systematically summarized the application, pharmacological effects, mechanism as well as in vivo studies of berberine and herbs which contain berberine. Berberine has a definite effect in promoting the proliferation and differentiation of osteoblasts as well as inhibiting the production of osteoclasts to promote bone regeneration. However, the present studies about the system mechanisms and pharmacological activity of berberine were incomplete. Applying berberine for new drug development remains an exciting and promising alternative to bone regeneration engineering, with broad potential for therapeutic and clinical practice.

The BMP antagonist gremlin 1 contributes to the development of cortical excitatory neurons, motor balance and fear responses

Bone morphogenetic protein (BMP) signaling is required for early forebrain development and cortical formation. How the endogenous modulators of BMP signaling regulate the structural and functional maturation of the developing brain remains unclear. Here, we show that expression of the BMP antagonist Grem1 marks committed layer V and VI glutamatergic neurons in the embryonic mouse brain. Lineage tracing of Grem1-expressing cells in the embryonic brain was examined by administration of tamoxifen to pregnant Grem1creERT; Rosa26LSLTdtomato mice at 13.5 days post coitum (dpc), followed by collection of embryos later in gestation. In addition, at 14.5 dpc, bulk mRNA-seq analysis of differentially expressed transcripts between FACS-sorted Grem1-positive and -negative cells was performed. We also generated Emx1-cre-mediated Grem1 conditional knockout mice (Emx1-Cre;Grem1^flox/flox) in which the Grem1 gene was deleted specifically in the dorsal telencephalon. Grem1^Emx1cKO animals had reduced cortical thickness, especially layers V and VI, and impaired motor balance and fear sensitivity compared with littermate controls. This study has revealed new roles for Grem1 in the structural and functional maturation of the developing cortex.

Summary: The BMP antagonist Grem1 is expressed by committed deep-layer glutamatergic neurons in the embryonic mouse cortex. Grem1 conditional knockout mice display cortical and behavioral abnormalities.

Identification and Functional Annotation of Genes Related to Bone Stability in Laying Hens Using Random Forests

Skeletal disorders, including fractures and osteoporosis, in laying hens cause major welfare and economic problems. Although genetics have been shown to play a key role in bone integrity, little is yet known about the underlying genetic architecture of the traits. This study aimed to identify genes associated with bone breaking strength and bone mineral density of the tibiotarsus and the humerus in laying hens. Potentially informative single nucleotide polymorphisms (SNP) were identified using Random Forests classification. We then searched for genes known to be related to bone stability in close proximity to the SNPs and identified 16 potential candidates. Some of them had human orthologues. Based on our findings, we can support the assumption that multiple genes determine bone strength, with each of them having a rather small effect, as illustrated by our SNP effect estimates. Furthermore, the enrichment analysis showed that some of these candidates are involved in metabolic pathways critical for bone integrity. In conclusion, the identified candidates represent genes that may play a role in the bone integrity of chickens. Although further studies are needed to determine causality, the genes reported here are promising in terms of alleviating bone disorders in laying hens.

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.

Recombinant human bone morphogenetic protein-4 enhances tendon-to-bone attachment healing in a murine model of rotator cuff tear

Background

Injuries of tendon-to-bone attachments (TBA) are common clinical challenges. Bone morphogenetic protein-4 (BMP-4) is potent in chondrogenesis. However, studies focusing on the influence of BMP-4 on the healing of TBA are scarce. Thus, this study's objective was to explore the effect of BMP-4 on the healing of TBA in a murine model of rotator cuff tear.

Methods

An injury model of the supraspinatus tendon (SST) insertion was established on a total of 120 mature C57 black (BL)/6 mice (12 weeks old), who were then randomly allocated into 3 groups: BMP-4, noggin (an inhibitor of all BMP activities), and control, At weeks 2 and 4 after surgery, the supraspinatus tendon-humerus complexes (SSTHC) were harvested for microradiographic, histologic, immunofluorescent, and biomechanical evaluations.

Results

Radiographic data showed that BMP-4 was able to improve the quality of subchondral bone, manifested as higher bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and lower trabecular spacing (Tb.Sp). Histologically, the BMP-4 group at week-2 and -4 showed a better TBA healing interface, characterized by better organizational integration and remodeling, thicker fibrocartilage layer, and more fibrocartilage cells. Immunofluorescence evaluation demonstrated that the number of SOX 9 positive cells in the BMP-4 group was significantly more than that in the control or noggin groups at postoperative weeks 2 and 4 (P<0.05 for all). Mechanical testing results at postoperative weeks 4 demonstrated the failure load, and stiffness in the BMP-4 group were significantly higher (P<0.05 for both), while in the noggin group were significantly lower (P<0.05 for both), compared to the control group.

Conclusions

The BMP-4 might enhance TBA healing by promoting the regeneration of fibrocartilaginous enthesis and mineralization, while this process was inhibited by noggin. Thus, BMP-4 may be a potential therapy to augment TBA healing and finally lead to more rapid rehabilitation and reduce recurrent injury risk.

Contrasting roles for BMP-4 and ventromorphins (BMP agonists) in TGFβ-induced lens EMT

Transforming growth factor beta (TGFβ) and bone morphogenetic protein (BMP) signaling play opposing roles in epithelial-mesenchymal transition (EMT) of lens epithelial cells, a cellular process integral to the pathogenesis of fibrotic cataract. We previously showed that BMP-7-induced Smad1/5 signaling blocks TGFβ-induced Smad2/3-signaling and EMT in rat lens epithelial cell explants. To further explore the antagonistic role of BMPs on TGFβ-signaling, we tested the capability of BMP-4 or newly described BMP agonists, ventromorphins, in blocking TGFβ-induced lens EMT. Primary rat lens epithelial explants were treated with exogenous TGFβ2 alone, or in combination with BMP-4 or ventromorphins. Treatment with TGFβ2 induced lens epithelial cells to undergo EMT and transdifferentiate into myofibroblastic cells with upregulated α-SMA and nuclear translocation of Smad2/3 immunofluorescence. BMP-4 was able to suppress this EMT without blocking TGFβ2-nuclear translocation of Smad2/3. In contrast, the BMP agonists, ventromorphins, were unable to block TGFβ2-induced EMT, despite a transient and early ability to significantly reduce TGFβ2-induced nuclear translocation of Smad2/3. This intriguing disparity highlights new complexities in the responsiveness of the lens to differing BMP-related signaling. Further research is required to better understand the antagonistic relationship between TGFβ and BMPs in lens EMT leading to cataract.

Polo Like Kinase 4 (PLK4) impairs human bone marrow mesenchymal stem cell (BMSC) viability and osteogenic differentiation

Human bone marrow mesenchymal stem cell (hBMSC) viability and osteogenic differentiation play a critical role in bone disorders such as osteoporosis. In the present study, we identified the aberrant PLK4 upregulation in osteoporosis and downregulation in BMSCs during osteogenic differentiation. In isolated hBMSCs, PLK4 overexpression significantly inhibited, whereas PLK4 knockdown promoted cell viability and hBMSC osteogenic differentiation. For molecular mechanism, PLK4 overexpression decreased, whereas PLK4 knockdown increased WNT1 and β-catenin protein levels and the phosphorylation of Smad1/5/8. The Wnt/β-catenin signaling antagonist Dickkopf 1 (DKK1) or the BMP-Smads antagonist LDN193189 dramatically suppressed hBMSC osteoblast differentiation, and partially attenuated the promotive effects of PLK4 knockdown on hBMSC osteogenic differentiation. Altogether, PLK4 overexpression impairs hBMSC viability and osteogenic differentiation potential, possibly through the Wnt/β-catenin signaling and BMP/Smads signaling.

Characterization of the different oligomeric states of the DAN family antagonists SOSTDC1 and SOST

The DAN (differential screening-selected gene aberrative in neuroblastoma) family are a group of secreted extracellular proteins which typically bind to and antagonize BMP (bone morphogenetic protein) ligands. Previous studies have revealed discrepancies between the oligomerization state of certain DAN family members, with SOST (a poor antagonist of BMP signaling) forming a monomer while Grem1, Grem2, and NBL1 (more potent BMP antagonists) form non-disulfide linked dimers. The protein SOSTDC1 (Sclerostin domain containing protein 1) is sequentially similar to SOST, but has been shown to be a better BMP inhibitor. In order to determine the oligomerization state of SOSTDC1 and determine what effect dimerization might have on the mechanism of DAN family antagonism of BMP signaling, we isolated the SOSTDC1 protein and, using a battery of biophysical, biochemical, and structural techniques, showed that SOSTDC1 forms a highly stable non-covalent dimer. Additionally, this SOSTDC1 dimer was shown, using an in vitro cell based assay system, to be an inhibitor of multiple BMP signaling growth factors, including GDF5, while monomeric SOST was a very poor antagonist. These results demonstrate that SOSTDC1 is distinct from paralogue SOST in terms of both oligomerization and strength of BMP inhibition.

BMP11 regulates thermogenesis in white and brown adipocytes

Bone morphogenetic protein-11 (BMP11), also known as growth differentiation factor-11 (GDF11), is implicated in skeletal development and joint morphogenesis in mammals. However, its functions in adipogenesis and energy homeostasis are mostly unknown. The present study investigates crucial roles of BMP11 in cultured 3T3-L1 white and HIB1B brown adipocytes, using Bmp11 gene depletion and pharmacological inhibition of BMP11. The silencing of Bmp11 markedly decreases the expression levels of brown-fat signature proteins and beige-specific genes in white adipocytes and significantly down-regulates the expression levels of brown fat-specific genes in brown adipocytes. The deficiency of Bmp11 reduces the expressions of lipolytic protein markers in white and brown adipocytes. Moreover, BMP11 induces browning of 3T3-L1 adipocytes via coordination of multiple signalling pathways, including mTORC1-COX2 and p38MAPK-PGC-1α as non-canonical pathways, as well as Smad1/5/8 as a canonical pathway. We believe this study is the first to provide evidence of the potential roles of BMP11 for improvement of lipid catabolism in both cultured white and brown adipocytes, as well as the effect on browning of white adipocytes. Taken together, these results demonstrate the therapeutic potential for the treatment of obesity.

Innovative Strategies in Tendon Tissue Engineering

The tendon is a highly aligned connective tissue that transmits force from muscle to bone. Each year, more than 32 million tendon injuries have been reported, in fact, tendinopathies represent at least 50% of all sports injuries, and their incidence rates have increased in recent decades due to the aging population. Current clinical grafts used in tendon treatment are subject to several restrictions and there is a significant demand for alternative engineered tissue. For this reason, innovative strategies need to be explored. Tendon replacement and regeneration are complex since scaffolds need to guarantee an adequate hierarchical structured morphology and mechanical properties to stand the load. Moreover, to guide cell proliferation and growth, scaffolds should provide a fibrous network that mimics the collagen arrangement of the extracellular matrix in the tendons. This review focuses on tendon repair and regeneration. Particular attention has been devoted to the innovative approaches in tissue engineering. Advanced manufacturing techniques, such as electrospinning, soft lithography, and three-dimensional (3D) printing, have been described. Furthermore, biological augmentation has been considered, as an emerging strategy with great therapeutic potential.

BMP6 Regulates Corneal Epithelial Cell Stratification by Coordinating Their Proliferation and Differentiation and Is Upregulated in Pterygium

Purpose

Proper balance between cell proliferation and differentiation is essential for corneal epithelial (CE) stratification and homeostasis. Although bone morphogenetic protein-6 (BMP6) is known to be expressed in the CE for over 25 years, its function in this tissue remains unknown. Here, we test the hypothesis that BMP6 promotes CE cell stratification and homeostasis by regulating their proliferation and differentiation.

Methods

We employed postnatal day-12 (PN-12), PN-14, PN-20, and PN-90 mouse eyes; human corneal limbal epithelial (HCLE) cells; and ocular surface fibrovascular disease pterygium tissues to evaluate the role of BMP6 in CE proliferation, differentiation, and pathology by RT-qPCR, immunoblots, and/or immunofluorescent staining. Cell proliferation was quantified by immunostaining for Ki67.

Results

Coincident with the mouse CE stratification between PN-12 and PN-20, BMP6 was significantly upregulated and the BMP6 antagonist Noggin downregulated. Mature CE retained high BMP6 and low Noggin expression at PN-90. BMP6 and its receptors BMPR1A and BMPR2 were upregulated during in vitro stratification of HCLE cells. Consistent with its anti-proliferative role, exogenous BMP6 suppressed HCLE cell proliferation, downregulated cyclin-D1 and cyclin-D2, and upregulated cell-cycle inhibitors Krüppel-like factor 4 (KLF4) and p21. BMP6 also upregulated the desmosomal cadherins desmoplakin and desmoglein in HCLE cells, consistent with its pro-differentiation role. Human pterygium displayed significant upregulation of BMP6 coupled with downregulation of Noggin and cell-cycle suppressors KLF4 and p21.

Conclusions

BMP6 coordinates CE stratification and homeostasis by regulating their proliferation and differentiation. BMP6 is significantly upregulated in human pterygium concurrent with downregulation of Noggin, KLF4, and p21.

Biology of bone morphogenetic protein in bone repair and regeneration: A role for autologous blood coagulum as carrier

BMPs were purified from demineralized bone matrix based on their ability to induce new bone in vivo and they represent a large member of the TGF-β superfamily of proteins. BMPs serve as morphogenic signals for mesenchymal stem cell migration, proliferation and subsequently differentiation into cartilage and bone during embryonic development. A BMP when implanted with a collagenous carrier in a rat subcutaneous site is capable of inducing new bone by mimicking the cellular events of embryonic bone formation. Based on this biological principle, BMP2 and BMP7 containing collagenous matrix as carrier have been developed as bone graft substitutes for spine fusion and long bone fractures. Here, we describe a novel autologous bone graft substitute that contains BMP6 delivered within an autologous blood coagulum as carrier and summarize the biology of osteogenic BMPs in the context of bone repair and regeneration specifically the critical role that carrier plays to support osteogenesis.

Differential expression of BMP inhibitors gremlin and noggin in Hydra suggests distinct roles during budding and patterning of tentacles

BACKGROUND

Mechanisms regulating BMP and Wnt pathways and their interactions are not well studied in Hydra.

RESULTS

We report identification of BMP inhibitor gremlin, comparison of its expression with that of noggin and possible antagonism between Wnt and BMP signaling in Hydra. Gremlin is expressed in body column with high levels in budding region and in early buds. Noggin, on the other hand, is expressed in the hypostome, base of tentacles, lower body column, and basal disc. During budding, noggin is expressed at the sites of tentacle emergence. This was confirmed in ectopic tentacles in polyps treated with alsterpaullone (ALP), a GSK-3β inhibitor that leads to upregulation of Wnt pathway. RT-PCR data show that upregulation of Wnt is accompanied by downregulation of bmp 5-8b though noggin and gremlin remain unaltered till 24 hours.

CONCLUSIONS

Different expression patterns of gremlin and noggin suggest their roles in budding and patterning of tentacles, respectively. Further, bmp 5-8b inhibition by activated Wnt signaling does not directly involve noggin and gremlin in Hydra. Our data suggest that Wnt/BMP antagonism may have evolved early for defining the oral-aboral axis, while the involvement of BMP antagonists during axial patterning is a recent evolutionary acquisition within the Bilateria lineage.

Integrated In Silico-In Vitro Identification and Optimization of Bone Morphogenic Protein-2 Armpit Epitope as Its Antagonist Binding Site

Bone morphogenic protein-2 (BMP-2) is the most documented member of BMP family and plays a crucial role in bone formation and growth. In this study, we systematically analyze and compare the complex crystal structures and interaction properties of BMP-2 with its cognate receptors BMPR-I/BMPR-II and with its natural antagonist crossveinless-2 (CV-2) using an integrated in silico-in vitro strategy. It is found that the antagonist-binding site is not fully overlapped with the two receptor-binding sites on BMP-2 surface; the antagonist can competitively disrupt BMP-2-BMPR-II interaction using a blocking-out-of-site manner, but has no substantial influence on BMP-2-BMPR-I interaction. Here, the antagonist-binding site is assigned as a new functional epitope armpit to differ from the traditional conformational epitope wrist and linear epitope knuckle at receptor-binding sites. Structural analysis reveals that the armpit comprises three sequentially discontinuous, structurally vicinal peptide segments, separately corresponding to a loop region and two β-strands crawling on the protein surface. The three segments cannot work independently when splitting from the protein context, but can restore binding capability to CV-2 if they are connected to a single peptide. A systematic combination of different-length polyglycine linkers between these segments obtains a series of designed single peptides, from which several peptides that can potently interact with the armpit-recognition site of CV-2 with high affinity and specificity are identified using energetic analysis and fluorescence assay; they are expected to target BMP-2-CV-2 interaction in a self-inhibitory manner.

Characterization and immune function of decapentaplegic (Dpp) gene from the oriental river prawn, Macrobrachium nipponense

The Decapentaplegic (Dpp) gene, which belongs to the TGF-β superfamily, is involved in multiple developmental processes in eukaryotic species. In this study, we firstly identified and characterized Dpp from Macrobrachium nipponense. Its full-length open reading frame (ORF) cDNA was 1332 bp, encoding 443 amino acids. The putative MnDpp protein contained a signal peptide, a TGF-β propeptide region and a TGF-β domain. Its TGF-β domain was highly conserved from vertebrates to invertebrates, and exhibited highly similarity to Dpp derived from Bombyx mori. qRT-PCR analysis suggested that MnDpp expressed in all tested tissues and responded to both bacterial and virus pathogens, indicating MnDpp was involved in the innate immune response of M. nipponense. Knockdown of MnDppin vivo significantly increased bacteria growth and markedly decreased the expressions of NF-κB signaling genes including dorsal, relish, TAK1, TAB1, Ikkβ and Ikkε as well as antimicrobial peptides (AMPs) including ALF2, ALF3, ALF4, ALF5, Cru1 and Cru2. Moreover, in vitro overexpression of MnDpp protein in HEK293T cells further demonstrated that it exerted antibacterial immune response by activation of NF-κB signaling cascade. In summary, these results indicated that MnDpp played an important role in the innate immunity in M. nipponense by modulating NF-κB signaling pathway, which might provide new insights about Dpp in crustaceans and paved the way for a better understanding of the crustacean innate immune system.

Three-Dimensional Printing for Craniofacial Bone Tissue Engineering

The basic concepts from the fields of biology and engineering are integrated into tissue engineering to develop constructs for the repair of damaged and/or absent tissues, respectively. The field has grown substantially over the past two decades, with particular interest in bone tissue engineering (BTE). Clinically, there are circumstances in which the quantity of bone that is necessary to restore form and function either exceeds the patient's healing capacity or bone's intrinsic regenerative capabilities. Vascularized osseous or osteocutaneous free flaps are the standard of care with autologous bone remaining the gold standard, but is commonly associated with donor site morbidity, graft resorption, increased operating time, and cost. Regardless of the size of a craniofacial defect, from trauma, pathology, and osteonecrosis, surgeons and engineers involved with reconstruction need to consider the complex three-dimensional (3D) geometry of the defect and its relationship to local structures. Three-dimensional printing has garnered significant attention and presents opportunities to use craniofacial BTE as a technology that offers a personalized approach to bony reconstruction. Clinicians and engineers are able to work together to produce patient-specific space-maintaining scaffolds tailored to site-specific defects, which are osteogenic, osseoconductive, osseoinductive, encourage angiogenesis/vasculogenesis, and mechanically stable upon implantation to prevent immediate failure. In this work, we review biological and engineering principles important in applying 3D printing technology to BTE for craniofacial reconstruction as well as present recent translational advancements in 3D printed bioactive ceramic scaffold technology.

Lessons from joint development for cartilage repair in the clinic

More than 250 years ago, William Hunter stated that when cartilage is destroyed it never recovers. In the last 20 years, the understanding of the mechanisms that lead to joint formation and the knowledge that some of these mechanisms are reactivated in the homeostatic responses of cartilage to injury has offered an unprecedented therapeutic opportunity to achieve cartilage regeneration. Very large investments in ambitious clinical trials are finally revealing that, although we do not have perfect medicines yet, disease modification is a feasible possibility for human osteoarthritis.

Loss of BMP signaling mediated by BMPR1A in osteoblasts leads to differential bone phenotypes in mice depending on anatomical location of the bones

Bone morphogenetic protein (BMP) signaling in osteoblasts plays critical roles in skeletal development and bone homeostasis. Our previous studies showed loss of function of BMPR1A, one of the type 1 receptors for BMPs, in osteoblasts results in increased trabecular bone mass in long bones due to an imbalance between bone formation and bone resorption. Decreased bone resorption was associated with an increased mature-to-immature collagen cross-link ratio and mineral-matrix ratios in the trabecular compartments, and increased tissue-level biomechanical properties. Here, we investigated the bone mass, bone composition and biomechanical properties of ribs and spines in the same genetically altered mouse line to compare outcomes by loss of BMPR1A functions in bones from different anatomic sites and developmental origins. Bone mass was significantly increased in both cortical and trabecular compartments of ribs with minimal to modest changes in compositions. While tissue-levels of biomechanical properties were not changed between control and mutant animals, whole bone levels of biomechanical properties were significantly increased in association with increased bone mass in the mutant ribs. For spines, mutant bones showed increased bone mass in both cortical and trabecular compartments with an increase of mineral content. These results emphasize the differential role of BMP signaling in osteoblasts in bones depending on their anatomical locations, functional loading requirements and developmental origin.

Secreted BMP antagonists and their role in cancer and bone metastases

Bone morphogenetic proteins (BMPs) are multifunctional secreted cytokines that act in a highly context-dependent manner. BMP action extends beyond the induction of cartilage and bone formation, to encompass pivotal roles in controlling tissue and organ homeostasis during development and adulthood. BMPs signal via plasma membrane type I and type II serine/threonine kinase receptors and intracellular SMAD transcriptional effectors. Exquisite temporospatial control of BMP/SMAD signalling and crosstalk with other cellular cues is achieved by a series of positive and negative regulators at each step in the BMP/SMAD pathway. The interaction of BMP ligand with its receptors is carefully controlled by a diverse set of secreted antagonists that bind BMPs and block their interaction with their cognate BMP receptors. Perturbations in this BMP/BMP antagonist balance are implicated in a range of developmental disorders and diseases, including cancer. Here, we provide an overview of the structure and function of secreted BMP antagonists, and summarize recent novel insights into their role in cancer progression and bone metastasis. Gremlin1 (GREM1) is a highly studied BMP antagonist, and we will focus on this molecule in particular and its role in cancer. The therapeutic potential of pharmacological inhibitors for secreted BMP antagonists for cancer and other human diseases will also be discussed.

An update on the diagnosis and treatment of pediatric pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a heterogeneous disease that mainly affects the pulmonary arterioles, leading to significant morbidity and mortality. Pulmonary hypertension in children from birth to adolescence presents important differences from that of adults. The majority of pediatric pulmonary arterial hypertension (PAH) cases are idiopathic or associated with congenital heart disease. However, the management of pediatric PAH mainly depends on the results of evidence-based adult studies and the clinical experiences of pediatric experts.

AREAS COVERED

This article briefly reviews the recent updates on the definition, classification, and diagnostic evaluation of pediatric PAH and their impact on treatment strategies. The main purpose of this review is to discuss the current pediatric therapies, as well as the prospective therapies, in terms of therapeutic targets, actions, side effects, and dosages.

EXPERT OPINION

Although there is no cure for PAH, recent advances in the form of new treatment options have improved the quality of life and survival rates of PAH patients. PAH-targeted drugs and treatment strategies for adult PAH have not been sufficiently studied in children. However, the growing scientific activity in that field will surely change the treatment option recommendations in pediatric PH from experience-based to evidence-based in the near future.

Palmitoylation of BMPR1a regulates neural stem cell fate

Neural stem cells (NSCs) generate neurons and glial cells throughout embryonic and postnatal brain development. The role of S-palmitoylation (also referred to as S-acylation), a reversible posttranslational lipid modification of proteins, in regulating the fate and activity of NSCs remains largely unknown. We used an unbiased screening approach to identify proteins that are S-acylated in mouse NSCs and showed that bone morphogenic protein receptor 1a (BMPR1a), a core mediator of BMP signaling, is palmitoylated. Genetic manipulation of S-acylated sites affects the localization and trafficking of BMPR1a and leads to altered BMP signaling. Strikingly, defective palmitoylation of BMPR1a modulates NSC function within the mouse brain, resulting in enhanced oligodendrogenesis. Thus, we identified a mechanism regulating the behavior of NSCs and provided the framework to characterize dynamic posttranslational lipid modifications of proteins in the context of NSC biology.

Tetrandrine inhibits proliferation of colon cancer cells by BMP9/ PTEN/ PI3K/AKT signaling

Despite advances in screening and treatment, colon cancer remains one of the leading causes of cancer-related death. Finding novel and useful drug treatment targets is also an urgent need for clinical applications. Tetrandrine (Tet) is extracted from the Chinese medicinal herbal medicine, which is a well-known calcium blocker with a variety of pharmacological activities, including anti-cancer. In this study, we recruited cell viability assay, flow cytometry analysis, cloning formation to confirm that Tet can inhibit the proliferation of SW620 cells, and induce apoptosis. Mechanically, we confirmed that Tet up-regulates the mRNA and protein level of BMP9 in SW620 cells. Over-expression BMP9 enhances the anti-cancer effects of Tet in SW620 cells, but these effects can be partly reversed by silencing BMP9. Also, Tet reduces phosphorylation of Aktl/2/3 in SW620 cells, which could be elevated by overexpressed BMP9 and impaired by silencing BMP9. Furthermore, we demonstrated that Tet reduces phosphorylated PTEN, which can be promoted by overexpressed BMP9, analogously also be attenuated through silencing BMP9. Finally, we introduced a xenograft tumor model to investigate the anti-proliferative effect of Tet, further to explore the effects of BMP9 and PTEN in SW620 cells. Our findings suggested that the anti-cancer activity of Tet in SW620 cells may be mediated partly by up-regulating BMP9, followed by inactivation PI3K/Akt through up-regulating PTEN at least.

HBO Promotes the Differentiation of Neural Stem Cells via Interactions Between the Wnt3/β-Catenin and BMP2 Signaling Pathways

Hyperbaric oxygen (HBO) therapy may promote neurological recovery from hypoxic-ischemic encephalopathy (HIE). However, the therapeutic effects of HBO and its associated mechanisms remain unknown. The canonical Wnt/β-catenin signaling pathways and bone morphogenetic protein (BMP) play important roles in mammalian nervous system development. The present study examined whether HBO stimulates the differentiation of neural stem cells (NSCs) and its effect on Wnt3/β-catenin and BMP2 signaling pathways. We showed HBO treatment (2 ATA, 60 min) promoted differentiation of NSCs into neurons and oligodendrocytes in vitro. In addition, rat hypoxic-ischemic brain damage (HIBD) tissue extracts also promoted the differentiation of NSCs into neurons and oligodendrocytes, with the advantage of reducing the number of astrocytes. These effects were most pronounced when these two were combined together. In addition, the expression of Wnt3a, BMP2, and β-catenin nuclear proteins were increased after HBO treatment. However, blockade of Wnt/β-catenin or BMP signaling inhibited NSC differentiation and reduced the expression of Wnt3a, BMP2, and β-catenin nuclear proteins. In conclusion, HBO promotes differentiation of NSCs into neurons and oligodendrocytes and reduced the number of astrocytes in vitro possibly through regulation of Wnt3/β-catenin and BMP2 signaling pathways. HBO may serve as a potential therapeutic strategy for treating HIE.

Is NO the Answer? The Nitric Oxide Pathway Can Support Bone Morphogenetic Protein 2 Mediated Signaling

The growth factor bone morphogenetic protein 2 (BMP2) plays an important role in bone development and repair. Despite the positive effects of BMP2 in fracture healing, its use is associated with negative side effects and poor cost effectiveness, partly due to the large amounts of BMP2 applied. Therefore, reduction of BMP2 amounts while maintaining efficacy is of clinical importance. As nitric oxide (NO) signaling plays a role in bone fracture healing and an association with the BMP2 pathway has been indicated, this study aimed to investigate the relationship of BMP2 and NO pathways and whether NO can enhance BMP2-induced signaling and osteogenic abilities in vitro. To achieve this, the stable BMP reporter cell line C2C12BRELuc was used to quantify BMP signaling, and alkaline phosphatase (ALP) activity and gene expression were used to quantify osteogenic potency. C2C12BRELuc cells were treated with recombinant BMP2 in combination with NO donors and substrate (Deta NONOate, SNAP & L-Arginine), NOS inhibitor (LNAME), soluble guanylyl cyclase (sGC) inhibitor (LY83583) and activator (YC-1), BMP type-I receptor inhibitor (LDN-193189), or protein kinase A (PKA) inhibitor (H89). It was found that the NOS enzyme, direct NO application, and sGC enhanced BMP2 signaling and improved BMP2 induced osteogenic activity. The application of a PKA inhibitor demonstrated that BMP2 signaling is enhanced by the NO pathway via PKA, underlining the capability of BMP2 in activating the NO pathway. Collectively, this study proves the ability of the NO pathway to enhance BMP2 signaling.

CircPOMT1 and circMCM3AP inhibit osteogenic differentiation of human adipose-derived stem cells by targeting miR-6881-3p

Circular RNAs (circRNAs), novel endogenous non-coding RNAs with the special circular structure, have been found to play critical roles in various development of tissues and diseases. However, few studies have focused on the functions and mechanisms of circRNAs in the osteogenesis of human adipose-derived stem cells (hASCs). Here, we performed the circRNAs sequencing and bioinformatic analysis to investigate the expression profiles of hASCs during osteogenic differentiation. There were 150 upregulated circRNAs and 60 downregulated circRNAs expressed differentially. Among them, the expression of circPOMT1 and circMCM3AP were downregulated during the osteogenesis of hASCs. hsa-miR-6881-3p could promote the osteogenic differentiation of hASCs, while the expression of circPOMT1 and circMCM3AP were negatively correlated with it. Smad6 and Chordin, critical inhibitors of the BMPs signaling pathway, were predicted to be the targets of hsa-miR-6881-3p. Therefore, circPOMT1 and circMCM3AP might influence the osteogenic differentiation of hASCs by targeting hsa-miR-6881-3p via BMPs signaling pathway. CircPOMT1 and circMCM3AP are potential novel targets for the repairment of bone defects.

Novel therapeutic approaches in utilizing platelet lysate in regenerative medicine: Are we ready for clinical use?

Hemoderivative materials are used to treat different diseases. These derivatives include platelet-rich plasma, serum, platelet gel, and platelet lysate (PL). Among them, PL contains more growth factors than the others and its production is inexpensive and easy. PL is one of the proper sources of platelet release factors. It is used in cells growth and proliferation and is a good alternative to fetal bovine serum. In recent years, the clinical use of PL has gained more appeal by scientists. PL is a solution saturated by growth factors, proteins, cytokines, and chemokines and is administered to treat different diseases such as wound healing, bone regeneration, alopecia, oral mucositis, radicular pain, osteoarthritis, and ocular diseases. In addition, it can be used in cell culture for cell therapy and tissue transplantation purposes. Platelet-derived growth factor, fibroblast growth factor, insulin-like growth factor, transforming growth factor β, and vascular endothelial growth factor are key PL growth factors playing a major role in cell proliferation, wound healing, and angiogenesis. In this paper, we scrutinized recent advances in using PL and PL-derived growth factors to treat diseases and in regenerative medicine, and the ability to replace PL with other hemoderivative materials.

The fast degradation of β-TCP ceramics facilitates healing of bone defects by the combination of BMP-2 and Teriparatide

Accumulating evidence suggests that the degradation and resorption of calcium phosphate ceramics is always relatively slow, which may inhibit calcium phosphate ceramics' replacement by new bone tissues and the ultimate bone defect repair. Bone morphogenetic proteins (BMPs) and Teriparatide (PTH) are extensively applied in the treatment of bone pathologies, while their effects on the degradation of calcium phosphate ceramics is limited. In this study, we tested the effects of BMP and PTH on degradation of β-tricalcium phosphate (β-TCP) ceramics and bone formation on β-TCP in ovariectomized (OVX) rat models. After establishment of femur defect model on OVX rats, the BMP + PTH group's rats were injected Teriparatide (30 μg/kg) subcutaneous every other day, while rats of control group and group BMP were injected equal-to-group volume sterilized saline water. Twelve weeks after femur surgery, all rats were sacrificed for Micro-CT scanning and histology tests. The results showed that BMP facilitated degradation of β-TCP and new bone formation on β-TCP ceramics. And PTH showed an additional effect on degradation of β-TCP when combined with BMP. In addition, the results explained that PTH promoted the remodeling of the bone callus occurred during repair.

Inflammatory expression profile in peripheral blood mononuclear cells from patients with Nasu-Hakola Disease

Homozygous mutations in Triggering Receptor Expressed on Myeloid cells 2 gene (TREM2) are one of the major causes of Nasu Hakola Disease (NHD). We analysed Peripheral Blood Mononuclear Cells (PBMC) profile of 164 inflammatory factors in patients with NHD carrying the TREM2 Q33X mutation as compared with heterozygous and wild type individuals. Several molecules related to bone formation and angiogenesis were altered in NHD compared to non-carriers: Bone Morphogenetic Protein (BMP)-1 mRNA levels were significantly increased in PBMC (2.32 fold-increase; P = 0.01), as were Transforming Growth Factor Beta (TGFB)3 levels (1.51 fold-increase; P = 0.02). Conversely, CXCL5 and Pro Platelet Basic Protein (PPBP) were strongly downregulated (-28.26, -9.85 fold-decrease over non-carriers, respectively, P = 0.01), as well as Platelet Factor 4 Variant 1 (PF4V1; -41.44, P = 0.03). Among other inflammatory factors evaluated, Interleukin (IL)-15 and Tumor Necrosis Factor Superfamily Member (TNFSF)4 mRNA levels were decreased in NHD as compared with non-carriers (-2.25 and -3.87 fold-decrease, P = 0.01 and 0.001, respectively). In heterozygous individuals, no significant differences were observed, apart from IL-15 mRNA levels, that were decreased at the same extent as NHD (-2.05 fold-decrease over non-carriers, P = 0.002). We identified a signature in PBMC from patients with NHD consisting of strongly decreased mRNA levels of CXCL5, PPBP, PF4V1, mildly decreased IL-15 and TNFSF4 and mildly increased BMP-1 and TGFB3.