Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation.

A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. Here, we hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation.

Treatment of Osteosarcoma of the Talus With a 3D-Printed Talar Prosthesis.

A 31-year-old male was diagnosed with osteoblastic osteosarcoma of the talus. Limb-salvage surgery for talar osteosarcoma was performed by replacing the intact talus with a 3D-printed talar prosthesis made from medical-grade titanium. The prosthesis had 3 tunnels for simulating the ligaments around the talus.

Unique anabolic action of stem cell gene therapy overexpressing PDGFB-DSS6 fusion protein in OVX osteoporosis mouse model.

In the present study we sought to improve the efficacy and safety of our Sca1 PDGFB stem cell gene therapy for osteoporosis in ovariectomized (OVX) mouse model. This therapy is administered by marrow transplantation. We established the promise of this approach by previously showing that this therapy in normal mice increase bone density, increased endosteal cortical and trabecular bone formation, caused de novo trabecular bone formation, increased cortical thickness and improve bone strength.

Mechanistic study of the cause of decreased blood 1,25-Dihydroxyvitamin D in sepsis.

Background: Vitamin D deficiency, determined by blood levels of 25-hydroxyvitamin D [25(OH) D, i.e. the major vitamin D form in blood], has been shown to associate with all-cause mortalities.

Cyclooxygenase 2 augments osteoblastic but suppresses chondrocytic differentiation of CD90 skeletal stem cells in fracture sites.

Cyclooxygenase 2 (COX-2) is essential for normal tissue repair. Although COX-2 is known to enhance the differentiation of mesenchymal stem cells (MSCs), how COX-2 regulates MSC differentiation into different tissue-specific progenitors to promote tissue repair remains unknown. Because it has been shown that COX-2 is critical for normal bone repair and local COX-2 overexpression in fracture sites accelerates fracture repair, this study aimed to determine the MSC subsets that are targeted by COX-2.

In Vivo Generation of Gut-Homing Regulatory T Cells for the Suppression of Colitis.

Current therapies for gut inflammation have not reached the desired specificity and are attended by unintended immune suppression. This study aimed to provide evidence for supporting a hypothesis that direct in vivo augmentation of the induction of gut-homing regulatory T (Treg) cells is a strategy of expected specificity for the treatment of chronic intestinal inflammation (e.g.

Dendritic cells, engineered to overexpress 25-hydroxyvitamin D 1α-hydroxylase and pulsed with a myelin antigen, provide myelin-specific suppression of ongoing experimental allergic encephalomyelitis.

Multiple sclerosis (MS) is caused by immune-mediated damage of myelin sheath. Current therapies aim to block such immune responses. However, this blocking is not sufficiently specific and hence compromises immunity, leading to severe side effects.

Unique Regenerative Mechanism to Replace Bone Lost During Dietary Bone Depletion in Weanling Mice.

The present study was undertaken to determine the mechanism whereby calcitropic hormones and mesenchymal stem cell progeny changes are involved in bone repletion, a regenerative bone process that restores the bone lost to calcium deficiency. To initiate depletion, weanling mice with a mixed C57BL/6 (75%) and CD1 (25%) genetic background were fed a calcium-deficient diet (0.01%) for 14 days.

Targeting Non-classical Myelin Epitopes to Treat Experimental Autoimmune Encephalomyelitis.

Qa-1 epitopes, the peptides that bind to non-classical major histocompatibility complex Ib Qa-1 molecules and are recognized by Qa-1-restricted CD8 regulatory T (Treg) cells, have been identified in pathogenic autoimmune cells that attack myelin sheath in experimental autoimmune encephalomyelitis (EAE, an animal model for multiple sclerosis [MS]). Additionally, immunization with such epitopes ameliorates the EAE. However, identification of such epitopes requires knowledge of the pathogenic autoimmune cells which are largely unknown in MS patients.

Leucine-rich repeat kinase-1 regulates osteoclast function by modulating RAC1/Cdc42 Small GTPase phosphorylation and activation.

Leucine-rich repeat kinase-1 (Lrrk1) consists of ankyrin repeats (ANK), leucine-rich repeats (LRR), a GTPase-like domain of Roc (ROC), a COR domain, a serine/threonine kinase domain (KD), and WD40 repeats (WD40). Previous studies have revealed that knockout (KO) of Lrrk1 in mice causes severe osteopetrosis, and a human mutation of Lrrk1 leads to osteosclerotic metaphysial dysplasia. The molecular mechanism by which Lrrk1 regulates osteoclast function is unknown.

Targeted 25-hydroxyvitamin D3 1α-hydroxylase adoptive gene therapy ameliorates dss-induced colitis without causing hypercalcemia in mice.

Systemic 1,25(OH)2D3 treatment ameliorating murine inflammatory bowel diseases (IBD) could not be applied to patients because of hypercalcemia. We tested the hypothesis that increasing 1,25(OH)2D3 synthesis locally by targeting delivery of the 1α-hydroxylase gene (CYP27B1) to the inflamed bowel would ameliorate IBD without causing hypercalcemia. Our targeting strategy is the use of CD11b(+)/Gr1(+) monocytes as the cell vehicle and a macrophage-specific promoter (Mac1) to control CYP27B1 expression.

Claudin 18 is a novel negative regulator of bone resorption and osteoclast differentiation.

Claudin 18 (Cldn-18) belongs to a large family of transmembrane proteins that are important components of tight junction strands. Although several claudin members are expressed in bone, the functional role for any claudin member in bone is unknown. Here we demonstrate that disruption of Cldn-18 in mice markedly decreased total body bone mineral density, trabecular bone volume, and cortical thickness in Cldn-18(-/-) mice.

Role of diabetes- and obesity-related protein in the regulation of osteoblast differentiation.

Although thyroid hormone (TH) is known to exert important effects on the skeleton, the nuclear factors constituting the TH receptor coactivator complex and the molecular pathways by which TH mediates its effects on target gene expression in osteoblasts remain poorly understood. A recent study demonstrated that the actions of TH on myoblast differentiation are dependent on diabetes- and obesity-related protein (DOR). However, the role of DOR in osteoblast differentiation is unknown.

Leptin receptor (Lepr) is a negative modulator of bone mechanosensitivity and genetic variations in Lepr may contribute to the differential osteogenic response to mechanical stimulation in the C57BL/6J and C3H/HeJ pair of mouse strains.

This study investigated the role of leptin receptor (Lepr) signaling in determining the bone mechanosensitivity and also evaluated whether differences in the Lepr signaling may contribute to the differential osteogenic response of the C57BL/6J (B6) and C3H/HeJ (C3H) pair of mouse strains to mechanical stimuli. This study shows that a loading strain of ∼2,500 με, which was insufficient to produce a bone formation response in B6 mice, significantly increased bone formation parameters in leptin-deficient ob(-)/ob(-) mice and that a loading strain of ∼3,000 με also yielded greater osteogenic responses in Lepr-deficient db(-)/db(-) mice than in wild-type littermates. In vitro, a 30-min steady shear stress increased [(3)H]thymidine incorporation and Erk1/2 phosphorylation in ob(-)/ob(-) osteoblasts and db(-)/db(-) osteoblasts much greater than those in corresponding wild-type osteoblasts.

Effect of topical glucocorticoid treatment in chinchilla model of lipopolysaccharide induced otitis media with effusion.

Objective: To compare the efficacy of topical treatment with three glucocorticoids in lipopolysaccharide induced otitis media with effusion (OME).

Methods: Chinchillas were divided into seven treatment groups consisting of vehicle and three glucocorticoids: dexamethasone sodium phosphate (DSP), fluticasone propionate (FP), and hydrocortisone, each at concentrations of 0.1% and 1.

Glutaredoxin 5 regulates osteoblast apoptosis by protecting against oxidative stress.

There is now increasing evidence which suggests an important role for reactive oxygen species (ROS) in the pathogenesis of osteoporosis. However, little is known on the molecular components of the oxidative stress pathway or their functions in bone. In this study, we evaluated the role and mechanism of action of glutaredoxin (Grx) 5, a protein that is highly expressed in bone.

Targeted transgenic expression of an osteoclastic transmembrane protein-tyrosine phosphatase in cells of osteoclastic lineage increases bone resorption and bone loss in male young adult mice.

This study evaluated whether transgenic expression of PTP-oc (osteoclastic transmembrane protein-tyrosine phosphatase) in cells of the osteoclast lineage would affect bone resorption and bone density in young adult mice. Transgenic mice were generated with a transgenic construct using a tartrate-resistant acid phosphatase exon 1C promoter to drive expression of rabbit PTP-oc in osteoclastic cells. pQCT evaluation of femurs of young adult male progeny of three lines showed that transgenic mice had reduced bone volume and area, cortical and trabecular bone mineral content, and density.

Prepubertal OVX increases IGF-I expression and bone accretion in C57BL/6J mice.

It is generally well accepted that the pubertal surge in estrogen is responsible for the rapid bone accretion that occurs during puberty and that this effect is mediated by an estrogen-induced increase in growth hormone (GH)/insulin-like growth factor (IGF) action. To test the cause and effect relationship between estrogen and GH/IGF, we evaluated the consequence of ovariectomy (OVX) in prepubertal mice (C57BL/6J mice at 3 wk of age) on skeletal changes and the GH/IGF axis during puberty. Contrary to our expectations, OVX increased body weight (12-18%), bone mineral content (11%), bone length (4%), bone size (3%), and serum, liver, and bone IGF-I (30-50%) and decreased total body fat (18%) at 3 wk postsurgery.

Nuclear factor I transcription factors regulate IGF binding protein 5 gene transcription in human osteoblasts.

Insulin-like growth factor binding protein 5 (IGFBP5) is expressed in many cell types including osteoblasts and modulates IGF activities. IGFBP5 may affect osteoblasts and bone formation, in part by mechanisms independent of binding IGFs. The highly conserved IGFBP5 proximal promoter within 100 nucleotides of the start of transcription contains functional cis regulatory elements for C/EBP, Myb and AP-2.

Complex genetic regulation of bone mineral density and insulin-like growth factor-I in C57BL/6J-Chr #A/J/NaJ chromosome substitution strains.

Low bone mineral density (BMD) is a phenotype associated with osteoporosis and increased risk of fracture. Since 60-80% of variation in BMD is associated with genetic factors, we used the novel approach of chromosome substitution strains (CSS) to identify chromosomes that harbor genes that regulate BMD. Specifically, we evaluated 24 wk old C57BL/6J-Chr #(A/J)/NaJ CSS (n = 7 to 18) in which each chromosome in the host C57BL/6J strain is replaced by a corresponding chromosome from the donor A/J strain (19 autosomes, X, Y).

Comparison of distortion product otoacoustic emissions in 28 inbred strains of mice.

Cochlear function was evaluated in a longitudinal study of 28 inbred strains of mice at 3 and 5 mo of age using measures of distortion product otoacoustic emissions (DPOAEs) in response to a federal initiative to develop rapid mouse phenotyping methodologies. DP-grams at f(2) frequencies ranging from 6.3 to 54.

Tumor necrosis factor-alpha augments matrix metalloproteinase-9 production in skeletal muscle cells through the activation of transforming growth factor-beta-activated kinase 1 (TAK1)-dependent signaling pathway.

We have investigated the effect of tumor necrosis factor-alpha (TNF-alpha) on the production of extracellular matrix-degrading proteases in skeletal muscles. Using microarray, quantitative PCR, Western blotting, and zymography, we found that TNF-alpha drastically increases the production of matrix metalloproteinase (MMP)-9 from C2C12 myotubes. In vivo administration of TNF-alpha in mice increased the transcript level of MMP-9 in skeletal muscle tissues.

Conditional deletion of insulin-like growth factor-I in collagen type 1alpha2-expressing cells results in postnatal lethality and a dramatic reduction in bone accretion.

IGF-I acts through endocrine and local, autocrine/paracrine routes. Disruption of both endocrine and local IGF-I action leads to neonatal lethality and impaired growth in various tissues including bone; however, the severity of growth and skeletal phenotype caused by disruption of endocrine IGF-I action is far less than with total IGF-I disruption. Based on these data and the fact that bone cells express IGF-I in high abundance, we and others predicted that locally produced IGF-I is also critical in regulating growth and bone accretion.

Nuclear factor-E2-related factor-1 mediates ascorbic acid induction of osterix expression via interaction with antioxidant-responsive element in bone cells.

We recently found that deletion of the gulonolactone oxidase gene, which is involved in the synthesis of ascorbic acid (AA), was responsible for the fracture phenotype in spontaneous fracture mice. To explore the molecular mechanisms by which AA regulates osteoblast differentiation, we examined the effect of AA on osterix expression via Nrf1 (NF-E2-related factor-1) binding to antioxidant-responsive element (ARE) in bone marrow stromal (BMS) cells. AA treatment caused a 6-fold increase in osterix expression in mutant BMS cells at 24 h, which was unaffected by pretreatment with protein synthesis inhibitor.