Bone Morphogenetic Protein Signal Transduction Research Articles

The miR-182/Myadm axis regulates hypoxia-induced pulmonary hypertension by balancing the BMP- and TGF-β-signalling pathways in an SMC/EC-crosstalk-associated manner.

We recently identified oncologic miR-182 as a new regulator of pulmonary artery hypertension (PAH) that targets myeloid-associated differentiation marker (Myadm), which is expressed in bone marrow stem cells and multipotent progenitors. Both miR-182 and Myadm are expressed in the cardiopulmonary system and correlated with the balance between the bone morphogenetic protein (BMP) and the transforming growth factor (TGF)-β signalling pathways, which are disturbed in PAH. We hypothesize that miR-182/Myadm are involved in BMP-TGF-β-signalling way in PAH. Hypoxia triggered pathological progression in cardiopulmonary PAH in vivo and in vitro; these changes were accompanied by strongly dowregulated BMP/SMAD1/5/8 expression and enhanced TGF-β/SMAD2/3 signalling pathway, favouring SMAD4/SMAD2 transcript formation and inhibiting the PAH negative regulator Id1 expression. miR-182 gain-of-function significantly inhibited the pathological progression in hypoxia-induced PAH (HPH) in vivo and in vitro, with a restoration of the balance in BMP-TGF-β signalling pathway. This recovery was abrogated by overexpression of Myadm. Conversely, loss-of-function of miR-182 increased the pathological progression of HPH followed by severe disturbance of BMP and TGF-β signal transduction and reduced Id1 expression, which was restored by Myadm knockdown. We also showed that the miR-182/Myadm relate BMP-TGF-β pathway is associated with NOS3/NO/cGMP via the crosstalk between endothelial cells and smooth muscle cells. Our findings further support the therapeutic significance of miR-182/Myadm in PAH via the balance of BMP- and TGF-β-associated mechanisms.

Research progress of hair follicle and related stem cells in scar-free wound healing

To explore the research progress of hair follicle and related stem cells in scar-free skin healing in recent years. The literature related to hair follicle and related stem cells, wound healing, and scar formation in recent years was extensively reviewed and summarized from the aspects of cell function and molecular mechanism. Scar tissue after wound healing treated with hair follicle transplantation and related stem cell therapy is more mild or even without scar formation. The cell types and molecular mechanisms of the above phenomena are complex, and the bone morphogenetic protein signal transduction pathway and Wnt signal transduction pathway are strongly correlated. The research of hair follicle and related stem cells in scar-free skin healing is at the initial stage at present. Strengthening the mechanism research may provide new ideas for the treatment of wound and scar.

Opposing SMAD-6 and SMAD-7 Expression Profiles Correlate with the Sensitivity of Multiple Myeloma Cells to Bone Morphogenetic Protein (BMP)-2

Objective: Multiple myeloma (MM) is a hematologic disease characterized by hyper-proliferation of antibody secreting B-cells. One of the most severe accompanying symptoms in MM is the destruction of bone tissue. Thus, the use of bone morphogenetic proteins (BMPs) for MM treatment seems to be a good option since these proteins are capable to induce formation of bone tissue in vivo and additionally can suppress cell proliferation of malignant Bcells. But, the different BMP family members vary in their biological activities also in terms of donor specific differences of addressed cells. In this study we analyzed signal transduction of two different TGFβ family members, BMP2 and GDF5, in different MM cell lines.Methods: Ten MM cell lines were stimulated either with BMP2 or GDF5 and cell proliferation was analyzed by WST-1 assays. Receptor expression levels were determined by qRT-PCR for relevant BMP receptors. SMAD-1/5/8 phosphorylation was analyzed by Western blot and correlated to the expression levels of inhibitory (i)-SMADs, SMAD-6 and SMAD-7 proteins, respectively.Results: Only three out of ten investigated cell lines were BMP2 responsive, one of which was additionally sensitive to GDF5. Depending on the expression of the required receptors the different cell lines could be divided into three subgroups. The first group expressed all receptor chains which are crucial for proper signal transduction and was ligand sensitive, the second also expressed the required receptors, but appeared ligand-resistant. The third subgroup instead missed at least one or more essential receptor rendering these cells also resistant to ligand exposure. Western blot analyses addressing phosphorylated SMAD-1/5/8 proteins revealed that the second group showed no or at least extremely reduced levels of SMAD-1/5/8 phosphorylation levels upon ligand exposure. Furthermore, Western blot analyses also showed that non-responsive cells expressed the inhibitory SMAD-7 protein at high levels prior to ligand stimulation. In contrast, the BMP2 responsive cells did not express SMAD-7 but instead expressed SMAD-6 at high levels prior to ligand stimulation.Conclusion: Aside of the expression of essential receptors, further factors are decisive for proper BMP signal transduction in MM cells such as the individual expression levels of SMAD-6 and SMAD-7 in unstimulated cells. The conspicuous opposing basal expression levels of either SMAD-6 or SMAD-7 might be used as prediction whether a particular MM cell line appears ligand-responsive or ligand-resistant.

Increased Bone Morphogenetic Protein Signaling in the Cutaneous Vasculature of Patients with Calciphylaxis

Background: The objective of this study was to investigate the role of bone morphogenetic protein (BMP) signal transduction in the pathogenesis of calciphylaxis. Methods: Skin biopsy specimens were obtained from 18 patients with, and 12 patients without, calciphylaxis. Tissue sections were stained with antibodies directed against BMP effector proteins phosphorylated-SMAD (p-SMAD) 1/5/9, inhibitor of DNA 1 (Id1), inhibitor of DNA 3 (Id3), and Runx2. The intensity of staining was scored semi-quantitatively as strong versus weak or absent. Results: Of the 18 patients with calciphylaxis (mean age: 59 ± 8 years), 9 were women and 15 had end-stage renal disease. Of the 12 control patients (mean age: 57 ± 10 years), 8 were women and 8 had end-stage renal disease. Strong staining for p-SMAD 1/5/9 was detected in blood vessels from all calciphylaxis patients. In 1 patient with calciphylaxis, strong staining for p-SMAD 1/5/9 was detected in a blood vessel that did not have evidence of calcification. Id1 and Id3 immunoreactivity was detected in blood vessels from all 12 patients with calciphylaxis that were tested. Runx2 staining was detected in all 6 patients with calciphylaxis who were tested. p-SMAD 1/5/9 immunoreactivity was weak or absent in blood vessels of 10 of the 12 control samples. Conclusions: The BMP signal transduction pathway is activated in the cutaneous vasculature of calciphylaxis patients. The ability to detect p-SMAD 1/5/9, Id1, and Id3 in cutaneous vasculature may assist in the diagnosis of calciphylaxis. As BMP signaling inhibitors become available, this pathway may serve as a future therapeutic target for calciphylaxis.

Inflammation-driven colon neoplasmatogenesis in uPA-deficient mice is associated with an increased expression of Runx transcriptional regulators

Deregulation of the bone morphogenetic protein (BMP) pathway has been documented in colorectal cancer (CRC). Previously, we investigated possible associations between urokinase-type plasminogen activator (uPA) deficiency and expression of extracellular constituents of BMP signaling in a newly developed mouse model of inflammation-driven intestinal neoplasmatogenesis, in which chronic colitis and CRC are induced using dextran sodium sulfate (DSS). In this report, we explored the contribution of intracellular components of Smad-mediated BMP signal transduction using the same model. Interestingly, upon DSS treatment, we noticed an overexpression of Runx1/2/3 transcription factors in both wild-type and uPA-deficient mice. Moreover, Runx1 and Runx2 expression levels exhibited an even higher increase in DSS-treated/uPA-deficient mice as compared to DSS-treated/wild-type animals. In all experimental conditions, in situ investigation of Runx-expressing cell types, revealed detection of all three Runx in the immune cells, yet in the DSS-treated/uPA-deficient mice Runx1 and Runx2 were also identified in the preneoplastic epithelium of advanced high-grade dysplasia and carcinoma in-situ colonic lesions. Finally, the uPA-deficient pro-tumorigenic colitic microenvironment exhibited increased levels of the Runx-induced target genes Snai2, Bim and Claudin1, known to have a role in tumor development and progression. These findings suggest that the absence of uPA correlates with increased levels of Runx transcriptional regulators in a way that promotes inflammation-associated carcinogenesis.

IRS4, a novel modulator of BMP/Smad and Akt signalling during early muscle differentiation

Elaborate regulatory networks of the Bone Morphogenetic Protein (BMP) pathways ensure precise signalling outcome during cell differentiation and tissue homeostasis. Here, we identified IRS4 as a novel regulator of BMP signal transduction and provide molecular insights how it integrates into the signalling pathway. We found that IRS4 interacts with the BMP receptor BMPRII and specifically targets Smad1 for proteasomal degradation consequently leading to repressed BMP/Smad signalling in C2C12 myoblasts while concomitantly activating the PI3K/Akt axis. IRS4 is present in human and primary mouse myoblasts, the expression increases during myogenic differentiation but is downregulated upon final commitment coinciding with Myogenin expression. Functionally, IRS4 promotes myogenesis in C2C12 cells, while IRS4 knockdown inhibits differentiation of myoblasts. We propose that IRS4 is particularly critical in the myoblast stage to serve as a molecular switch between BMP/Smad and Akt signalling and to thereby control cell commitment. These findings provide profound understanding of the role of BMP signalling in early myogenic differentiation and open new ways for targeting the BMP pathway in muscle regeneration.

Bone Morphogenetic Protein-Based Therapeutic Approaches.

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the transforming growth factor (TGF)-β family of ligands and exert most of their effects through the canonical effectors Smad1, 5, and 8. Appropriate regulation of BMP signaling is critical for the development and homeostasis of numerous human organ systems. Aberrations in BMP pathways or their regulation are increasingly associated with diverse human pathologies, and there is an urgent and growing need to develop effective approaches to modulate BMP signaling in the clinic. In this review, we provide a wide perspective on diseases and/or conditions associated with dysregulated BMP signal transduction, outline the current strategies available to modulate BMP pathways, highlight emerging second-generation technologies, and postulate prospective avenues for future investigation.

Regulation of Bone Morphogenetic Protein Signaling by ADP-ribosylation

We previously established a mechanism of negative regulation of transforming growth factor β signaling mediated by the nuclear ADP-ribosylating enzyme poly-(ADP-ribose) polymerase 1 (PARP1) and the deribosylating enzyme poly-(ADP-ribose) glycohydrolase (PARG), which dynamically regulate ADP-ribosylation of Smad3 and Smad4, two central signaling proteins of the pathway. Here we demonstrate that the bone morphogenetic protein (BMP) pathway can also be regulated by the opposing actions of PARP1 and PARG. PARG positively contributes to BMP signaling and forms physical complexes with Smad5 and Smad4. The positive role PARG plays during BMP signaling can be neutralized by PARP1, as demonstrated by experiments where PARG and PARP1 are simultaneously silenced. In contrast to PARG, ectopic expression of PARP1 suppresses BMP signaling, whereas silencing of endogenous PARP1 enhances signaling and BMP-induced differentiation. The two major Smad proteins of the BMP pathway, Smad1 and Smad5, interact with PARP1 and can be ADP-ribosylated in vitro, whereas PARG causes deribosylation. The overall outcome of this mode of regulation of BMP signal transduction provides a fine-tuning mechanism based on the two major enzymes that control cellular ADP-ribosylation.

Dynamin-dependent endocytosis of Bone Morphogenetic Protein2 (BMP2) and its receptors is dispensable for the initiation of Smad signaling

Bone Morphogenetic Protein (BMP) signal transduction via the canonical Smad158 pathway has previously been linked to dynamin-dependent endocytosis, since the application of chemical inhibitors of clathrin or dynamin in functional cell culture based assays negatively affects initiation and propagation of the Smad response. More recent studies, however, demonstrated efficient Smad signaling by non-internalizable BMP2. The role of endocytosis in BMP signal transduction thus remained controversial. In our study we aimed to refine cell biological assays and to apply novel tools, including a new site-directed fluorescently labeled BMP2 ligand, to revisit key steps in BMP Smad signaling. We found that dynamin2 function was required for BMP2 uptake but was dispensable for C-terminal phosphorylation, nuclear translocation and transcriptional activity of BMP-dependent Smads. Furthermore, we demonstrated a role of dynamin2 in the regulation of steady-state and surface BMP receptor levels, as well as an impact on Smad1 protein level. Thus, dynamin2 allows for modulation of basal and ligand-dependent Smad signaling capacity. High levels of functional dynamin2 enhanced the myogenic differentiation of precursor cells. From our study we conclude that dynamin-dependent endocytosis serves as a regulatory mechanism to fine-tune Smad signaling, but it is not a prerequisite for signal initiation and propagation. Our findings contribute to the understanding of fundamental mechanisms of BMP signaling and thus provide important information for future consideration in the context of therapeutic applications of BMPs.

Inhibition of bone morphogenetic protein signal transduction prevents the medial vascular calcification associated with matrix Gla protein deficiency.

ObjectiveMatrix Gla protein (MGP) is reported to inhibit bone morphogenetic protein (BMP) signal transduction. MGP deficiency is associated with medial calcification of the arterial wall, in a process that involves both osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs) and mesenchymal transition of endothelial cells (EndMT). In this study, we investigated the contribution of BMP signal transduction to the medial calcification that develops in MGP-deficient mice. Approach and ResultsMGP-deficient mice (MGP-/-) were treated with one of two BMP signaling inhibitors, LDN-193189 or ALK3-Fc, beginning one day after birth. Aortic calcification was assessed in 28-day-old mice by measuring the uptake of a fluorescent bisphosphonate probe and by staining tissue sections with Alizarin red. Aortic calcification was 80% less in MGP-/- mice treated with LDN-193189 or ALK3-Fc compared with vehicle-treated control animals (P<0.001 for both). LDN-193189-treated MGP-/- mice survived longer than vehicle-treated MGP-/- mice. Levels of phosphorylated Smad1/5 and Id1 mRNA (markers of BMP signaling) did not differ in the aortas from MGP-/- and wild-type mice. Markers of EndMT and osteogenesis were increased in MGP-/- aortas, an effect that was prevented by LDN-193189. Calcification of isolated VSMCs was also inhibited by LDN-193189. ConclusionsInhibition of BMP signaling leads to reduced vascular calcification and improved survival in MGP-/- mice. The EndMT and osteogenic transdifferentiation associated with MGP deficiency is dependent upon BMP signaling. These results suggest that BMP signal transduction has critical roles in the development of vascular calcification in MGP-deficient mice.

Specific control of BMP signaling and mesenchymal differentiation by cytoplasmic phosphatase PPM1H.

Bone morphogenetic proteins (BMPs) belong to the TGF-β superfamily of structurally related signaling proteins that regulate a wide array of cellular functions. The key step in BMP signal transduction is the BMP receptor-mediated phosphorylation of transcription factors Smad1, 5, and 8 (collectively Smad1/5/8), which leads to the subsequent activation of BMP-induced gene transcription in the nucleus. In this study, we describe the identification and characterization of PPM1H as a novel cytoplasm-localized Smad1/5/8-specific phosphatase. PPM1H directly interacts with Smad1/5/8 through its Smad-binding domain, and dephosphorylates phospho-Smad1/5/8 (P-Smad1/5/8) in the cytoplasm. Ectopic expression of PPM1H attenuates BMP signaling, whereas loss of PPM1H activity or expression greatly enhances BMP-dependent gene regulation and mesenchymal differentiation. In conclusion, this study suggests that PPM1H acts as a gatekeeper to prevent excessive BMP signaling through dephosphorylation and subsequent nuclear exclusion of P-Smad1/5/8 proteins.

Autocrine activation of canonical BMP signaling regulates PD‐L1 and PD‐L2 expression in human dendritic cells

Bone morphogenetic proteins (BMPs) are multifunctional growth factors regulating differentiation and proliferation in numerous systems including the immune system. Previously, we described that the BMP signaling pathway is functional in human monocyte-derived dendritic cells (MoDCs), which were found to express both the specific receptors and the Smad proteins required for signal transduction. In this study, we provide evidence that human MoDCs produce BMP-4 and that this production is increased over the maturation process as is BMP signal transduction. When DCs are matured in the presence of an inhibitor of the BMP pathway, the expression of the maturation markers PD-L1 and PD-L2 is reduced, while cytokine production is not affected. As a result, these mature DCs present an augmented ability to stimulate both T cells and NK cells. Eventually, the inhibition of BMP signaling during maturation causes a reduced expression of IRF-1, a transcription factor that positively regulates the expression of PD-L1 and PD-L2. The present study indicates that the BMP signaling pathway regulates PD-L1 and PD-L2 expression in human MoDCs during the maturation process, probably through the IRF-1 transcription factor, and also points out that the manipulation of BMP signaling might considerably improve the immunogenicity of MoDCs used in immunotherapy.

N-linked glycosylation of the bone morphogenetic protein receptor type 2 (BMPR2) enhances ligand binding

The bone morphogenetic protein (BMP) signaling pathway is essential for normal development and tissue homeostasis. BMP signal transduction occurs when ligands interact with a complex of type 1 and type 2 receptors to activate downstream transcription factors. It is well established that a single BMP receptor may bind multiple BMP ligands with varying affinity, and this has been largely attributed to conformation at the amino acid level. However, all three type 2 BMP receptors (BMPR2, ACVR2A/B) contain consensus N-glycosylation sites in their extracellular domains (ECDs), which could play a role in modulating interaction with ligand. Here, we show a differential pattern of N-glycosylation between BMPR2 and ACVR2A/B. Site-directed mutagenesis reveals that BMPR2 is uniquely glycosylated near its ligand binding domain and at a position that is mutated in patients with heritable pulmonary arterial hypertension. We further demonstrate using a cell-free pulldown assay that N-glycosylation of the BMPR2-ECD enhances its ability to bind BMP2 ligand but has no impact on binding by the closely-related ACVR2B. Our results illuminate a novel aspect of BMP signaling pathway mechanics and demonstrate a functional difference resulting from post-translational modification of type 2 BMP receptors. Additionally, since BMPR2 is required for several aspects of normal development and defects in its function are strongly implicated in human disease, our findings are likely to be relevant in several biological contexts in normal and abnormal human physiology.

Decreased Hemojuvelin Protein Levels in Mask Mice Lacking Matriptase-2-Dependent Proteolytic Activity

Matriptase-2, a membrane protein encoded by the Tmprss6 gene, is a negative regulator of hepcidin expression. Although matriptase-2 has been proposed to cleave membrane hemojuvelin, we have recently found decreased hemojuvelin protein levels in Tmprss6 -/- mice. The purpose of this study was to confirm this observation by determining hemojuvelin protein levels in another strain of mice with disrupted Tmprss6 gene, and to determine the effect of matriptase-2 deficiency on the expression of other membrane proteins participating in the bone morphogenetic protein signal transduction. Mask mice, which lack the proteolytic domain of matriptase-2, displayed decreased liver hemojuvelin protein content, while Id1 mRNA level, an indicator of hemojuvelin-dependent signal transduction, was increased. Protein levels of bone morphogenetic protein receptors Alk3 and Acvr2a were unchanged, and transferrin receptor 2 and neogenin protein levels were slightly decreased. The results confirm that the loss of matriptase-2 increases bone morphogenetic protein-dependent signaling, while paradoxically decreasing liver hemojuvelin protein content. The regulation of transferrin receptor 2 protein levels by transferrin saturation was not affected in mask mice. How the loss of matriptase-2 proteolytic activity leads to decreased hemojuvelin protein levels is at present unclear.

Repulsive guidance molecules (RGMs) and neogenin in bone morphogenetic protein (BMP) signaling

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGFβ) superfamily. BMPs mediate a highly conserved signal transduction cascade through the type-I and type-II serine/threonine kinase receptors and intracellular Smad proteins, which regulate multiple developmental and homeostatic processes. Mutations in this pathway can cause various diseases in humans, such as skeletal disorders, cardiovascular diseases, and various cancers. Multiple levels of regulation, including extracellular regulation, help to ensure proper spatiotemporal control of BMP signaling in the right cellular context. The family of repulsive guidance molecules (RGMs) and the type-I transmembrane protein neogenin, a paralog of DCC (Deleted in Colorectal Cancer), have been implicated in modulating the BMP pathway. In this review, we discuss the properties and functions of RGM proteins and neogenin, focusing on their roles in the modulation of BMP signal transduction.

Mummy, A UDP-N-acetylglucosamine pyrophosphorylase, modulates DPP signaling in the embryonic epidermis of Drosophila

The evolutionarily conserved JNK/AP-1 (Jun N-terminal kinase/activator protein 1) and BMP (Bone Morphogenetic Protein) signaling cascades are deployed hierarchically to regulate dorsal closure in the fruit fly Drosophila melanogaster. In this developmental context, the JNK/AP-1 signaling cascade transcriptionally activates BMP signaling in leading edge epidermal cells. Here we show that the mummy (mmy) gene product, which is required for dorsal closure, functions as a BMP signaling antagonist. Genetic and biochemical tests of Mmy's role as a BMP-antagonist indicate that its function is independent of AP-1, the transcriptional trigger of BMP signal transduction in leading edge cells. pMAD (phosphorylated Mothers Against Dpp) activity data show the mmy gene product to be a new type of epidermal BMP regulator – one which transforms a BMP ligand from a long- to a short-range signal. mmy codes for the single UDP-N-acetylglucosamine pyrophosphorylase in Drosophila, and its requirement for attenuating epidermal BMP signaling during dorsal closure points to a new role for glycosylation in defining a highly restricted BMP activity field in the fly. These findings add a new dimension to our understanding of mechanisms modulating the BMP signaling gradient.

Myotubularin-related Protein 4 (MTMR4) Attenuates BMP/Dpp Signaling by Dephosphorylation of Smad Proteins

Bone morphogenetic proteins (BMPs) signaling essentially regulates a wide range of biological responses. Although multiple regulators at different layers of the receptor-effectors axis have been identified, the mechanisms of homeostatic BMP signaling remain vague. Herein we demonstrated that myotubularin-related protein 4 (MTMR4), a FYVE domain-containing dual-specificity protein phosphatase (DUSP), preferentially associated with and dephosphorylated the activated R-Smads in cytoplasm, which is a critical checkpoint in BMP signal transduction. Therefore, transcriptional activation by BMPs was tightly controlled by the expression level and the intrinsic phosphatase activity of MTMR4. More profoundly, ectopic expression of MTMR4 or its Drosophila homolog CG3632 genetically interacted with BMP/Dpp signaling axis in regulation of the vein development of Drosophila wings. By doing so, MTMR4 could interact with and dephosphorylate Mothers against Decapentaplegic (Mad), the sole R-Smad in Drosophila BMP pathway, and hence affected the target genes expression of Mad. In conclusion, this study has suggested that MTMR4 is a necessary negative modulator for the homeostasis of BMP/Dpp signaling.

BMP signaling in telencephalic neural cell specification and maturation

Bone morphogenetic proteins (BMPs) make up a family of morphogens that are critical for patterning, development, and function of the central and peripheral nervous system. Their effects on neural cells are pleiotropic and highly dynamic depending on the stage of development and the local niche. Neural cells display a broad expression profile of BMP ligands, receptors, and transducer molecules. Moreover, interactions of BMP signaling with other incoming morphogens and signaling pathways are crucial for most of these processes. The key role of BMP signaling suggests that it includes many regulatory mechanisms that restrict BMP activity both temporally and spatially. BMPs affect neural cell fate specification in a dynamic fashion. Initially they inhibit proliferation of neural precursors and promote the first steps in neuronal differentiation. Later on, BMP signaling effects switch from neuronal induction to promotion of astroglial identity and inhibition of neuronal or oligodendroglial lineage commitment. Furthermore, in postmitotic cells, BMPs regulate cell survival and death, to modulate neuronal subtype specification, promote dendritic and axonal growth and induce synapse formation and stabilization. In this review, we examine the canonical and non-canonical mechanisms of BMP signal transduction. Moreover, we focus on the specific role of BMPs in the nervous system including their ability to regulate neural stem cell proliferation, self-renewal, lineage specification, and neuronal function.

Overactive bone morphogenetic protein signaling in heterotopic ossification and Duchenne muscular dystrophy

Bone morphogenetic proteins (BMPs) are important extracellular cytokines that play critical roles in embryogenesis and tissue homeostasis. BMPs signal via transmembrane type I and type II serine/threonine kinase receptors and intracellular Smad effector proteins. BMP signaling is precisely regulated and perturbation of BMP signaling is connected to multiple diseases, including musculoskeletal diseases. In this review, we will summarize the recent progress in elucidation of BMP signal transduction, how overactive BMP signaling is involved in the pathogenesis of heterotopic ossification and Duchenne muscular dystrophy, and discuss possible therapeutic strategies for treatment of these diseases.

Effects of antenatal application of ambroxol and glucocorticoid on lung morphometry and signal transduction of bone morphogenetic protein in the fetal rat

Antenatal ambroxol, dexamethasone (Dex) and betamethasone (Beta) are used to prevent neonate respiratory distress syndrome. The present study aimed to investigate the role of ambroxol, Dex and Beta administered antenatally on lung morphogenesis and signal transduction of bone morphogenetic protein (BMP) in rat embryo. Fetal lungs treated with ambroxol, 1-day Beta, 3-day Dex and 3-day Beta were more mature compared to the controls as determined by light microscopy and transmission electron microscopy. Expression of BMP4 and bone morphogenetic protein receptor II (BMPR‑II) mRNA was upregulated in the 1-day-Beta-, 3-day-Dex- and 3-day-Beta-treated animals. BMP4 and BMPR-II protein were significantly increased in the 1-day-Beta-, 3-day-Dex- and 3-day-Beta-treated animals. Ambroxol, Dex and Beta promoted the morphological development of rat fetal lung; Beta was more effective than Dex. A multi-dose of glucocorticoids exhited a more beneficial effect than a single dose. The effects of Beta and Dex may be mediated by regulation of BMP signal transduction in rat fetal lung.