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Cell Death and Differentiation Jul 2016Mesenchymal stem cells (MSCs), a non-hematopoietic stem cell population first discovered in bone marrow, are multipotent cells capable of differentiating into mature... (Review)
Review
Mesenchymal stem cells (MSCs), a non-hematopoietic stem cell population first discovered in bone marrow, are multipotent cells capable of differentiating into mature cells of several mesenchymal tissues, such as fat and bone. As common progenitor cells of adipocytes and osteoblasts, MSCs are delicately balanced for their differentiation commitment. Numerous in vitro investigations have demonstrated that fat-induction factors inhibit osteogenesis, and, conversely, bone-induction factors hinder adipogenesis. In fact, a variety of external cues contribute to the delicate balance of adipo-osteogenic differentiation of MSCs, including chemical, physical, and biological factors. These factors trigger different signaling pathways and activate various transcription factors that guide MSCs to commit to either lineage. The dysregulation of the adipo-osteogenic balance has been linked to several pathophysiologic processes, such as aging, obesity, osteopenia, osteopetrosis, and osteoporosis. Thus, the regulation of MSC differentiation has increasingly attracted great attention in recent years. Here, we review external factors and their signaling processes dictating the reciprocal regulation between adipocytes and osteoblasts during MSC differentiation and the ultimate control of the adipo-osteogenic balance.
Topics: Adipocytes; Animals; Cell Differentiation; Dexamethasone; Humans; Mesenchymal Stem Cells; MicroRNAs; Osteoblasts; Signal Transduction
PubMed: 26868907
DOI: 10.1038/cdd.2015.168 -
Physiological Reviews Jul 2018CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion... (Review)
Review
CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl channels, whereas ClC-3 through ClC-7 are 2Cl/H-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
Topics: Animals; Chloride Channels; Deafness; Endocytosis; Endosomes; Humans; Kidney; Kidney Diseases; Muscle, Skeletal; Mutation; Myotonia; Neurodegenerative Diseases; Neurons; Osteopetrosis
PubMed: 29845874
DOI: 10.1152/physrev.00047.2017 -
Nature Apr 2019Osteoclasts are multinucleated giant cells that resorb bone, ensuring development and continuous remodelling of the skeleton and the bone marrow haematopoietic niche....
Osteoclasts are multinucleated giant cells that resorb bone, ensuring development and continuous remodelling of the skeleton and the bone marrow haematopoietic niche. Defective osteoclast activity leads to osteopetrosis and bone marrow failure, whereas excess activity can contribute to bone loss and osteoporosis. Osteopetrosis can be partially treated by bone marrow transplantation in humans and mice, consistent with a haematopoietic origin of osteoclasts and studies that suggest that they develop by fusion of monocytic precursors derived from haematopoietic stem cells in the presence of CSF1 and RANK ligand. However, the developmental origin and lifespan of osteoclasts, and the mechanisms that ensure maintenance of osteoclast function throughout life in vivo remain largely unexplored. Here we report that osteoclasts that colonize fetal ossification centres originate from embryonic erythro-myeloid progenitors. These erythro-myeloid progenitor-derived osteoclasts are required for normal bone development and tooth eruption. Yet, timely transfusion of haematopoietic-stem-cell-derived monocytic cells in newborn mice is sufficient to rescue bone development in early-onset autosomal recessive osteopetrosis. We also found that the postnatal maintenance of osteoclasts, bone mass and the bone marrow cavity involve iterative fusion of circulating blood monocytic cells with long-lived osteoclast syncytia. As a consequence, parabiosis or transfusion of monocytic cells results in long-term gene transfer in osteoclasts in the absence of haematopoietic-stem-cell chimerism, and can rescue an adult-onset osteopetrotic phenotype caused by cathepsin K deficiency. In sum, our results identify the developmental origin of osteoclasts and a mechanism that controls their maintenance in bones after birth. These data suggest strategies to rescue osteoclast deficiency in osteopetrosis and to modulate osteoclast activity in vivo.
Topics: Animals; Animals, Newborn; Bone Development; Female; Genes, Recessive; Hematopoietic Stem Cells; Male; Mice; Osteoclasts; Osteopetrosis; Tooth Eruption
PubMed: 30971820
DOI: 10.1038/s41586-019-1105-7 -
Genes Oct 2022Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases.... (Review)
Review
Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.
Topics: Humans; Bone Diseases, Metabolic; Rare Diseases
PubMed: 36292765
DOI: 10.3390/genes13101880 -
Inflammation and Regeneration 2020Receptor activator of NF-κB (RANK) ligand (RANKL) induces the differentiation of monocyte/macrophage-lineage cells into the bone-resorbing cells called osteoclasts.... (Review)
Review
Receptor activator of NF-κB (RANK) ligand (RANKL) induces the differentiation of monocyte/macrophage-lineage cells into the bone-resorbing cells called osteoclasts. Because abnormalities in RANKL, its signaling receptor RANK, or decoy receptor osteoprotegerin (OPG) lead to bone diseases such as osteopetrosis, the RANKL/RANK/OPG system is essential for bone resorption. RANKL was first discovered as a T cell-derived activator of dendritic cells (DCs) and has many functions in the immune system, including organogenesis, cellular development. The essentiality of RANKL in the bone and the immune systems lies at the root of the field of "osteoimmunology." Furthermore, this cytokine functions beyond the domains of bone metabolism and the immune system, e.g., mammary gland and hair follicle formation, body temperature regulation, muscle metabolism, and tumor development. In this review, we will summarize the current understanding of the functions of the RANKL/RANK/OPG system in biological processes.
PubMed: 32047573
DOI: 10.1186/s41232-019-0111-3 -
Bone May 2023Autosomal dominant osteopetrosis (ADO) is the most common form of osteopetrosis. ADO is characterized by generalized osteosclerosis along with characteristic... (Review)
Review
Autosomal dominant osteopetrosis (ADO) is the most common form of osteopetrosis. ADO is characterized by generalized osteosclerosis along with characteristic radiographic features such as a "bone-in-bone" appearance of long bones and sclerosis of the superior and inferior vertebral body endplates. Generalized osteosclerosis in ADO typically results from abnormalities in osteoclast function, due most commonly to mutations in the chloride channel 7 (CLCN7) gene. A variety of debilitating complications can occur over time due to bone fragility, impingement of cranial nerves, encroachment of osteopetrotic bone in the marrow space, and poor bone vascularity. There is a wide spectrum of disease phenotype, even within the same family. Currently, there is no disease specific treatment for ADO, so clinical care focuses on monitoring for disease complications and symptomatic treatment. This review describes the history of ADO, the wide disease phenotype, and potential new therapies.
Topics: Humans; Osteopetrosis; Mutation; Osteoclasts; Chloride Channels; Genes, Dominant
PubMed: 36863500
DOI: 10.1016/j.bone.2023.116723 -
Cancer Gene Therapy Nov 2022Transmembrane ATPases are membrane-bound enzyme complexes and ion transporters that can be divided into F-, V-, and A-ATPases according to their structure. The... (Review)
Review
Transmembrane ATPases are membrane-bound enzyme complexes and ion transporters that can be divided into F-, V-, and A-ATPases according to their structure. The V-ATPases, also known as H-ATPases, are large multi-subunit protein complexes composed of a peripheral domain (V1) responsible for the hydrolysis of ATP and a membrane-integrated domain (V0) that transports protons across plasma membrane or organelle membrane. V-ATPases play a fundamental role in maintaining pH homeostasis through lysosomal acidification and are involved in modulating various physiological and pathological processes, such as macropinocytosis, autophagy, cell invasion, and cell death (e.g., apoptosis, anoikis, alkaliptosis, ferroptosis, and lysosome-dependent cell death). In addition to participating in embryonic development, V-ATPase pathways, when dysfunctional, are implicated in human diseases, such as neurodegenerative diseases, osteopetrosis, distal renal tubular acidosis, and cancer. In this review, we summarize the structure and regulation of isoforms of V-ATPase subunits and discuss their context-dependent roles in cancer biology and cell death. Updated knowledge about V-ATPases may enable us to design new anticancer drugs or strategies.
Topics: Humans; Vacuolar Proton-Translocating ATPases; Cell Membrane; Neoplasms; Cell Death
PubMed: 35504950
DOI: 10.1038/s41417-022-00477-y