Bone morphogenetic protein 7 or BMP7 (also known as osteogenic protein-1 or OP-1) is a protein that in humans is encoded by the BMP7 gene. [5]
Bone morphogenetic protein 7 or BMP7 (also known as osteogenic protein-1 or OP-1) is a protein that in humans is encoded by the BMP7 gene. [5]
The protein encoded by this gene is a member of the TGF-β superfamily. Like other members of the bone morphogenetic protein family of proteins, it plays a key role in the transformation of mesenchymal cells into bone and cartilage. It is inhibited by noggin and a similar protein, chordin, which are expressed in the Spemann-Mangold Organizer. BMP7 may be involved in bone homeostasis. It is expressed in the brain, kidneys and bladder. [6]
BMP7 induces the phosphorylation of SMAD1 and SMAD5, which in turn induce transcription of numerous osteogenic genes. [7] It has been demonstrated that BMP7 treatment is sufficient to induce all of the genetic markers of osteoblast differentiation in many cell types. [6]
The role of BMP7 in mammalian kidney development is through induction of MET of the metanephrogenic blastema. [8] The epithelial tissue emerging from this MET process eventually forms the tubules and glomeruli of the nephron. [8] BMP-7 is also important in homeostasis of the adult kidney by inhibiting ephithelial-mesenchymal transition (EMT). BMP-7 expression is attenuated when the nephron is placed under inflammatory or ischemic stress, leading to EMT, which can result in fibrosis of the kidney. [9] This type of fibrosis often leads to renal failure, and is predictive of end stage renal disease. [10]
BMP7 has been discovered to be crucial in the determination of ventral-dorsal organization in zebrafish. BMP7 causes the expression of ventral phenotypes while its complete inhibition creates a dorsal phenotype. Moreover, BMP7 is eventually partially "turned off" in embryonic development in order to create the dorsal parts of the organism. [11]
In many early developmental experiments using zebrafish, scientists used caBMPR (constitutively active) and tBMP (truncated receptor) to determine the effect of BMP7 in embryogenesis. They found that the constitutively active, which causes BMP to be expressed everywhere creates a ventralized phenotype, whereas truncated, dorsalized.
Human recombinant BMP7 has surgical uses and was originally marketed under the brand name OP1 (discontinued by Olympus Biotech, who bought it from Stryker). It can be used to aid in the fusion of vertebral bodies to prevent neurologic trauma. [12] Also in the treatment of tibial non-union, frequently in cases where a bone graft has failed. [13] rhBMP-2 is much more widely used clinically because it helps grow bone better than rhBMP-7 and other BMPs. [14]
BMP7 also has the potential for treatment of chronic kidney disease. [15] [16] Kidney disease is characterized by derangement of the tubular architecture by both myofibroblast buildup and monocyte infiltration [17] Because endogenous BMP-7 is an inhibitor of the TGF-β signaling cascade that induces fibrosis, the use of exogenous recombinant BMP-7 (rhBMP-7) could be a viable treatment of chronic kidney disease. [8] It is also thought that BMP-7 reverses fibrosis and EMT through reduction in monocyte infiltration into inflamed tissue. [15] On a molecular level, BMP-7 represses inflammation by knocking down the expression of several pro-inflammatory cytokines produced by monocytes. [15] Reducing this inflammatory stress, in turn, reduces the chance of fibrosis. [9]
Regardless of the mechanism of fibrosis or the origin of myofibroblasts, exogenous BMP-7 has been shown to reverse the EMT process and trigger MET. [8] Eventually this restores the healthy epithelial cell population, and normal function of the kidneys in mice. [8] This is pertinent in humans as well, because many diseases stemming from organ fibrosis occur via the EMT process. [9] The epithelial-menenchymal transition is also problematic in cancer metastasis, so the diminution of EMT with recombinant DNA could have great implications in future cancer treatment options. [9]
BMP7 administration has been proposed as a possible treatment for human infertility due to poor response to FSH treatment. [18]
It was discovered that mice injected with BMP7 increased their production of "good" brown fat cells, while keeping their levels of the normal white fat cells constant. A BMP7 therapy for obesity in humans may be developed as a result. [19] [20]
BMP7 not only stimulates brown adipogenesis, [20] [21] it also stimulates the "browning" of brite or beige adipocytes, turning them from a white-like phenotype into a brown-like phenotype (with induction of UCP1 and able to perform non-shivering thermogenesis, which allows to disperse energy as heat). [22]
Several studies suggest that BMP7 may regulate or affect food intake. [23] [21]
In cellular biology, paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance, as opposed to cell signaling by endocrine factors, hormones which travel considerably longer distances via the circulatory system; juxtacrine interactions; and autocrine signaling. Cells that produce paracrine factors secrete them into the immediate extracellular environment. Factors then travel to nearby cells in which the gradient of factor received determines the outcome. However, the exact distance that paracrine factors can travel is not certain.
Chondrocytes are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans. Although the word chondroblast is commonly used to describe an immature chondrocyte, the term is imprecise, since the progenitor of chondrocytes can differentiate into various cell types, including osteoblasts.
Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body. The important functioning of BMP signals in physiology is emphasized by the multitude of roles for dysregulated BMP signalling in pathological processes. Cancerous disease often involves misregulation of the BMP signalling system. Absence of BMP signalling is, for instance, an important factor in the progression of colon cancer, and conversely, overactivation of BMP signalling following reflux-induced esophagitis provokes Barrett's esophagus and is thus instrumental in the development of esophageal adenocarcinoma.
The epithelial–mesenchymal transition (EMT) is a process by which epithelial cells lose their cell polarity and cell–cell adhesion, and gain migratory and invasive properties to become mesenchymal stem cells; these are multipotent stromal cells that can differentiate into a variety of cell types. EMT is essential for numerous developmental processes including mesoderm formation and neural tube formation. EMT has also been shown to occur in wound healing, in organ fibrosis and in the initiation of metastasis in cancer progression.
T-box transcription factor T, also known as Brachyury protein, is encoded for in humans by the TBXT gene. Brachyury functions as a transcription factor within the T-box family of genes. Brachyury homologs have been found in all bilaterian animals that have been screened, as well as the freshwater cnidarian Hydra.
Intermediate mesoderm or intermediate mesenchyme is a narrow section of the mesoderm located between the paraxial mesoderm and the lateral plate of the developing embryo. The intermediate mesoderm develops into vital parts of the urogenital system.
Bone morphogenetic protein 2 or BMP-2 belongs to the TGF-β superfamily of proteins.
Bone morphogenetic protein 4 is a protein that in humans is encoded by BMP4 gene. BMP4 is found on chromosome 14q22-q23.
Bone morphogenetic protein 8B is a protein that in humans is encoded by the BMP8B gene.
Bone morphogenetic protein 6 is a protein that in humans is encoded by the BMP6 gene.
Bone morphogenetic protein 5 is a protein that in humans is encoded by the BMP5 gene.
Smads comprise a family of structurally similar proteins that are the main signal transducers for receptors of the transforming growth factor beta (TGF-B) superfamily, which are critically important for regulating cell development and growth. The abbreviation refers to the homologies to the Caenorhabditis elegans SMA and MAD family of genes in Drosophila.
Mesenchyme is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every organ in the developing embryo.
Growth differentiation factor 2 (GDF2) also known as bone morphogenetic protein (BMP)-9 is a protein that in humans is encoded by the GDF2 gene. GDF2 belongs to the transforming growth factor beta superfamily.
Gremlin is an inhibitor in the TGF beta signaling pathway. It primarily inhibits bone morphogenesis and is implicated in disorders of increased bone formation and several cancers.
Kruppel-like factor 4 is a member of the KLF family of zinc finger transcription factors, which belongs to the relatively large family of SP1-like transcription factors. KLF4 is involved in the regulation of proliferation, differentiation, apoptosis and somatic cell reprogramming. Evidence also suggests that KLF4 is a tumor suppressor in certain cancers, including colorectal cancer. It has three C2H2-zinc fingers at its carboxyl terminus that are closely related to another KLF, KLF2. It has two nuclear localization sequences that signals it to localize to the nucleus. In embryonic stem cells (ESCs), KLF4 has been demonstrated to be a good indicator of stem-like capacity. It is suggested that the same is true in mesenchymal stem cells (MSCs).
Integrin beta-6 is a protein that in humans is encoded by the ITGB6 gene. It is the β6 subunit of the integrin αvβ6. Integrins are αβ heterodimeric glycoproteins which span the cell’s membrane, integrating the outside and inside of the cell. Integrins bind to specific extracellular proteins in the extracellular matrix or on other cells and subsequently transduce signals intracellularly to affect cell behaviour. One α and one β subunit associate non-covalently to form 24 unique integrins found in mammals. While some β integrin subunits partner with multiple α subunits, β6 associates exclusively with the αv subunit. Thus, the function of ITGB6 is entirely associated with the integrin αvβ6.
Cysteine-rich motor neuron 1 protein is a protein that in humans is encoded by the CRIM1 gene.
A mesenchymal–epithelial transition (MET) is a reversible biological process that involves the transition from motile, multipolar or spindle-shaped mesenchymal cells to planar arrays of polarized cells called epithelia. MET is the reverse process of epithelial–mesenchymal transition (EMT) and it has been shown to occur in normal development, induced pluripotent stem cell reprogramming, cancer metastasis and wound healing.
Madin-Darby canine kidney (MDCK) cells are a model mammalian cell line used in biomedical research. MDCK cells are used for a wide variety of cell biology studies including cell polarity, cell-cell adhesions, collective cell motility, toxicity studies, as well as responses to growth factors. It is one of few cell culture models that is suited for 3D cell culture and multicellular rearrangements known as branching morphogenesis.
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