Musculoskeletal Disease Center

Loma Linda, California, United States

Musculoskeletal Disease Center

Loma Linda, California, United States
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Edderkaoui B.,Musculoskeletal Disease Center | Edderkaoui B.,Loma Linda University
Frontiers in Endocrinology | Year: 2017

Chemokines are a family of small cytokines that share a typical key structure that is stabilized by disulfide bonds between the cysteine residues at the NH2-terminal of the protein, and they are secreted by a great variety of cells in several different conditions. Their function is directly dependent on their interactions with their receptors. Chemokines are involved in cell maturation and differentiation, infection, autoimmunity, cancer, and, in general, in any situation where immune components are involved. However, their role in postfracture inflammation and fracture healing is not yet well established. In this article, we will discuss the response of chemokines to bone fracture and their potential roles in postfracture inflammation and healing based on data from our studies and from other previously published studies. © 2017 Edderkaoui.

Gamsjaeger S.,Hanusch Hospital | Srivastava A.K.,Frederick National Laboratory for Cancer Research | Wergedal J.E.,Musculoskeletal Disease Center | Zwerina J.,Hanusch Hospital | And 3 more authors.
Journal of Bone and Mineral Research | Year: 2014

Spondyloarthropathy and inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, are often associated with severe osteopenia/osteoporosis in both children and adults. HLA-B27 transgenic rats present a phenotype that includes severe colitis and severely accelerated alveolar bone loss. The purpose of this study was to evaluate long bone density status, systemic bone metabolic markers, and intrinsic bone material properties in HLA-B27 transgenic (TG) rats, and compare them with those of age- and sex-matched wild-type (WT) animals. The results indicate that in the HLA-B27 rat, an animal susceptible to both alveolar bone loss (ABL) and long bone osteopenia, there is a statistically significant negative correlation between ABL and long bone bone mineral density (BMD), as well as mineral/matrix ratio at active bone-forming trabecular surfaces. The TG animals had a lower mineral/matrix ratio and higher relative proteoglycan and advanced glycation end product (e-N-Carboxymethyl-L-lysine) content and pyridinoline/divalent collagen cross-link ratio compared with WT. These results may provide better understanding of the interrelationship between osteoporosis and oral bone loss, the underlying causes of the inferior bone strength in the HLA-B27 transgenic animals, and could prove to be a useful model in the elucidation of the pathophysiology of spondyloarthropathy and IBD-associated osteopenia/osteoporosis and in the evaluation of pharmacological intervention(s) against such conditions. © 2014 American Society for Bone and Mineral Research.

Xing W.,Musculoskeletal Disease Center | Pourteymoor S.,Musculoskeletal Disease Center | Mohan S.,Musculoskeletal Disease Center | Mohan S.,Loma Linda University
Physiological Genomics | Year: 2011

Mouse genetic studies reveal that ascorbic acid (AA) is essential for osteoblast (OB) differentiation and that osterix (Osx) was a key downstream target of AA action in OBs. To determine the molecular pathways for AA regulation of Osx expression, we evaluated if AA regulates Osx expression by regulating production and/or actions of local growth factors and extracellular matrix (ECM) proteins. Inhibition of actions of IGFs by inhibitory IGFBP-4, BMPs by noggin, and ECM-mediated integrin signaling by RGD did not block AA effects on Osx expression in OBs. Furthermore, blockade of components of MAPK signaling pathway had no effect on AA-induced Osx expression. Because AA is required for prolyl hydroxylase domain (PHD) activity and because PHDinduced prolyl-hydroxylation targets proteins to proteosomal degradation, we next tested if AA effect on Osx expression involves activation of PHD to hydroxylate and induce ubiquitin-proteosomemediated degradation of transcriptional repressor(s) of Osx gene. Treatment of OBs with dimethyloxallyl glycine and ethyl 3, 4-dihydroxybenzoate, known inhibitors of PHD, completely blocked AA effect on Osx expression and OB differentiation. Knockdown of PHD2 expression by Lentivirus-mediated shRNA abolished AAinduced Osx induction and alkaline phosphatase activity. Furthermore, treatment of OBs with MG115, inhibitor of proteosomal degradation, completely blocked AA effects on Osx expression. Based on these data, we conclude that AA effect on Osx expression is mediated via a novel mechanism that involves PHD2 and proteosomal degradation of a yet to be identified transcriptional repressor that is independent of BMP, IGF-I, or integrin-mediated signaling in mouse OBs. © 2011 the American Physiological Society.

Lau K.-H.W.,Loma Linda University | Lau K.-H.W.,Musculoskeletal Disease Center | Kothari V.,Loma Linda University | Das A.,Loma Linda University | And 2 more authors.
Bone | Year: 2013

This study sought to determine the cellular and molecular mechanisms of cyclooxygenase-2 (COX2) gene therapy to accelerate fracture repair in a mouse multiple tibial fractures model. The lenti-COX2 (or lenti-gfp control vector) was injected into fractures on day 1 post-fracture. At days 3-7, the COX2 treatment increased Sdf1-, Cxcr4-, Nes-, and Podxl-expressing mesenchymal stem cells (MSCs) within fracture calluses, suggesting an enhanced MSC recruitment or expansion. The COX2-treated mice formed smaller cartilaginous calluses that had less cartilage tissues than control mice. The expression of Sox9 mRNA was 7-fold less in COX2-treated than in control calluses at day 14, implying that COX2 reduces chondrocytic differentiation of MSCs. The therapy also enhanced angiogenesis as reflected by increased immunostaining of CD31, vWF, and α-SMA over controls in the cartilaginous callus at day 14-21. At which time, the COX2 gene therapy promoted bony remodeling of the cartilaginous callus to bridge the fracture gap that was accompanied by 2-fold increase in osteoclasts along the surface of the woven bone and an onset of osteogenesis. Blocking angiogenesis with daily injection of endostatin from day 4 to day 10 into fracture sites blocked the COX2-mediated reduction of callus size that was associated with an increase in hypertrophic chondrocytes and concomitant reduction in osteoclasts. In conclusion, COX2 accelerates fracture healing in part through three biological actions: 1) increased recruitment/expansion of MSCs; 2) decreased cartilaginous callus formation; and 3) increased angiogenesis-dependent cartilage remodeling. These effects were associated with an earlier onset of bony bridging of the fracture gap. © 2013.

Mohan S.,Musculoskeletal Disease Center | Mohan S.,Loma Linda University | Kesavan C.,Musculoskeletal Disease Center | Kesavan C.,Loma Linda University
Current Osteoporosis Reports | Year: 2012

The importance of the insulin-like growth factor (IGF)-I axis in the regulation of bone size and bone mineral density, two important determinants of bone strength, has been well established from clinical studies involving patients with growth hormone deficiency and IGF-I gene disruption. Data from transgenic animal studies involving disruption and overexpression of components of the IGF-I axis also provide support for a key role for IGF-I in bone metabolism. IGF-I actions in bone are subject to regulation by systemic hormones, local growth factors, as well as mechanical stress. In this review we describe findings from various genetic mouse models that pertain to the role of endocrine and local sources of IGF-I in the regulation of skeletal growth. © Springer Science+Business Media, LLC 2012.

William Lau K.-H.,Musculoskeletal Disease Center | William Lau K.-H.,Loma Linda University | Stiffel V.,Musculoskeletal Disease Center | Amoui M.,Musculoskeletal Disease Center
American Journal of Physiology - Cell Physiology | Year: 2012

This study utilized the glutathione transferase (GST) pull-down assay to identify novel substrates of an osteoclastic protein-tyrosine phosphatase, PTP-oc. Consistent with the previous findings that the phosphorylated tyr-527 (pY527) of Src is a substrate of PTP-oc, the major protein pulled down with the phosphatase-deficient (PD)-PTP-oc-GST trapping mutant in RAW264.7 cells was Src. The GST-PD-PTP-oc also pulled down pY-Syk and pY-β3-integrin, but not after PP2 pretreatment. However, PTP-oc transgenic osteoclasts or PTP-oc-overexpressing RAW264.7 cells had elevated, and not reduced, levels of pY525/526-Syk and pY759-β3 integrin, and the PTP-oc siRNA treatment drastically reduced levels of pY525/526 Syk and pY759-β3-integrin in RAW264.7 cells. These findings are incompatible with the premise that they are substrates of PTP-oc. The PTP-oc-dependent increases in pY525/526-Syk and pY759-β3-integrin levels were completely blocked by PP2, indicating that these effects are secondary to PTP-oc-mediated activation of the Src protein-tyrosine kinase (PTK). Overexpression of PTP-oc increased, and siRNA-mediated suppression of PTP-oc reduced, pY160-Vav1, pY173-Vav3, and pY783-PLCγ levels, and Rac1 activation, which are downstream mediators of the ITAM/Syk signaling. Overexpression of PTP-oc also increased, and PTP-oc siRNA treatment decreased, the pY-Shp1 levels, which were blocked by PP2. Since Shp1 is a negative regulator of osteoclast activity and is a key mediator of the ITIM signaling, these findings suggest that PTP-oc is an upstream suppressor of the ITIM/Shp1 signaling through PTP-oc-induced Src-dependent Shp1 phosphorylation. In summary, PTP-oc plays a central regulatory role in the concerted regulation of the β3-integrin, the ITAM/Syk, and the ITIM/Shp1 signaling indirectly through activation of Src PTK. Copyright © 2012 the American Physiological Society.

Xing W.,Musculoskeletal Disease Center | Xing W.,Loma Linda University | Cheng S.,Musculoskeletal Disease Center | Wergedal J.,Musculoskeletal Disease Center | And 3 more authors.
Journal of Bone and Mineral Research | Year: 2014

Thyroid hormones (THs) are known to regulate endochondral ossification during skeletal development via acting directly in chondrocytes and osteoblasts. In this study, we focused on TH effects on the secondary ossification center (SOC) because the time of appearance of SOCs in several species coincides with the time when peak levels of TH are attained. Accordingly, micro-computed tomography (μCT) evaluation of femurs and tibias at day 21 in TH-deficient and control mice revealed that endochondral ossification of SOCs is severely compromised owing to TH deficiency and that TH treatment for 10 days completely rescued this phenotype. Staining of cartilage and bone in the epiphysis revealed that whereas all of the cartilage is converted into bone in the prepubertal control mice, this conversion failed to occur in the TH-deficient mice. Immunohistochemistry studies revealed that TH treatment of thyroid stimulating hormone receptor mutant (Tshr-/-) mice induced expression of Indian hedgehog (Ihh) and Osx in type 2 collagen (Col2)-expressing chondrocytes in the SOC at day 7, which subsequently differentiate into type 10 collagen (Col10)/osteocalcin-expressing chondro/osteoblasts at day 10. Consistent with these data, treatment of tibia cultures from 3-day-old mice with 10 ng/mL TH increased expression of Osx, Col10, alkaline phosphatase (ALP), and osteocalcin in the epiphysis by sixfold to 60-fold. Furthermore, knockdown of the TH-induced increase in Osx expression using lentiviral small hairpin RNA (shRNA) significantly blocked TH-induced ALP and osteocalcin expression in chondrocytes. Treatment of chondrogenic cells with an Ihh inhibitor abolished chondro/osteoblast differentiation and SOC formation. Our findings indicate that TH regulates the SOC initiation and progression via differentiating chondrocytes into bone matrix-producing osteoblasts by stimulating Ihh and Osx expression in chondrocytes. © 2014 American Society for Bone and Mineral Research.

Sheng M.H.-C.,Loma Linda University | Zhou X.-D.,Loma Linda University | Bonewald L.F.,University of Missouri - Kansas City | Baylink D.J.,Loma Linda University | And 2 more authors.
Bone | Year: 2013

This study evaluated the role of osteocyte-derived insulin-like growth factor 1 (IGF-1) in developmental bone growth by assessing the bone phenotype of osteocyte Igf1 conditional knockout (KO) mice, generated by crossing the Dmp1-driven Cre-expressing transgenic mice with Igf1 floxed mice containing loxP sites that flank exon 4 of the Igf1 gene. The periosteal diameter of femurs of homozygous conditional KO mutants was 8-12% smaller than wild-type (WT) littermates. The conditional mutants had 14-20%, 10-21%, and 15-31% reduction in total, trabecular, and cortical bone mineral contents, respectively. However, there were no differences in the total, trabecular, or cortical bone mineral densities, or in trabecular bone volume, thickness, number, and separation at secondary spongiosa between the mutants and WT littermates. The conditional KO mutants showed reduction in dynamic bone formation parameters at both periosteal and endosteal surfaces at the mid-diaphysis and in trabecular bone formation rate and resorption parameters at secondary spongiosa. The lower plasma levels of PINP and CTx in conditional KO mice support a regulatory role of osteocyte-derived IGF-1 in the bone turnover. The femur length of conditional KO mutants was 4-7% shorter due to significant reduction in the length of growth plate and hypertropic zone. The effect on periosteal expansion appeared to be bigger than that on longitudinal bone growth. The conditional KO mice had 14% thinner calvaria than WT littermates, suggesting that deficient osteocyte IGF-1 production also impairs developmental growth of intramembraneous bone. Conditional disruption of Igf1 in osteocytes did not alter plasma levels of IGF-1, calcium, or phosphorus. In summary, this study shows for the first time that osteocyte-derived IGF-1 plays an essential role in regulating bone turnover during developmental bone growth. © 2012 Elsevier Inc.

Yu H.,Musculoskeletal Disease Center | Wergedal J.E.,Musculoskeletal Disease Center | Zhao Y.,Columbia University | Mohan S.,Musculoskeletal Disease Center
Calcified Tissue International | Year: 2012

Transforming growth factor-beta induced (TGFBI) and periostin are two closely related proteins in structure as well as in function. A previous study found that periostin positively regulates bone size. Here, we hypothesize that TGFBI has a similar function in bone development. To test this hypothesis, we employed TGFBI-deficient mice, which were generated by targeted disruption of the TGFBI gene. We bred these mice with C57BL/6J mice to generate homozygous TGFBI-deficient (TGFBI -/-) mice and homozygous wild-type littermates. All mice were raised to 12 weeks of age. Bone mass parameters were determined by PIXImus and micro-CT, bone strength parameters by three-point bending, and bone formation and resorption parameters by histomorphometry. We found that targeted disruption of TGFBI led to reduced body size, bone mass, bone size, and bone strength. This indicates that, like periostin, TGFBI also positively regulates bone size and that changes in bone size affect bone strength. Furthermore, there was also a significant decrease in periosteal, but not endosteal, bone formation rate of cortical bone in TGFBI -/- mice, suggesting that the observed effect of TGFBI on bone mass and bone size was largely caused by the effect of TGFBI on periosteal bone formation. © 2012 Springer Science+Business Media, LLC.

Our previous work showed that a Sca-1+ cell-based FGF2 therapy was capable of promoting robust increases in trabecular bone formation and connectivity on the endosteum of long bones. Past work reported that administration of FGF2 protein promoted bone formation in red marrow but not in yellow marrow. The issue as to whether the Sca-1+ cell-based FGF2 therapy is effective in yellow marrow is highly relevant to its clinical potential for osteoporosis, as most red marrows in a person of an advanced age are converted to yellow marrows. Accordingly, this study sought to compare the osteogenic effects of this stem cell-based FGF2 therapy on red marrow-filled lumbar vertebrae with those on yellow marrow-filled caudal vertebrae of young adult W41/W41 mice. The Sca-1+ cell-based FGF2 therapy drastically increased trabecular bone formation in lumbar vertebrae, but the therapy not only did not promote bone formation but instead caused substantial loss of trabecular bone in caudal vertebrae. The lack of an osteogenic response was not due to insufficient engraftment of FGF2-expressing Sca-1+ cells or inadequate FGF2 expression in caudal vertebrae. Previous studies have demonstrated that recipient mice of this stem cell-based FGF2 therapy developed secondary hyperparathyroidism and increased bone resorption. Thus, the loss of bone mass in caudal vertebrae might in part be due to an increase in resorption without a corresponding increase in bone formation. In conclusion, the Sca-1+ cell-based FGF2 therapy is osteogenic in red marrow but not in yellow marrow.Gene Therapy advance online publication, 17 March 2016; doi:10.1038/gt.2016.21. © 2016 Macmillan Publishers Limited

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