Neutralizing Monoclonal Antibody (neutralizing + monoclonal_antibody)

Distribution by Scientific Domains

Selected Abstracts

Analysis of N-cadherin function in limb mesenchymal chondrogenesis in vitro,

Anthony M. Delise
Abstract During embryonic limb development, cartilage formation is presaged by a crucial mesenchymal cell condensation phase. N-Cadherin, a Ca2+ -dependent cell,cell adhesion molecule, is expressed in embryonic chick limb buds in a spatiotemporal pattern suggestive of its involvement during cellular condensation; functional blocking of N-cadherin homotypic binding, by using a neutralizing monoclonal antibody, results in perturbed chondrogenesis in vitro and in vivo. In high-density micromass cultures of embryonic limb mesenchymal cells, N-cadherin expression level is high during days 1 and 2, coincident with active cellular condensation, and decreases upon overt chondrogenic differentiation from day 3 on. In this study, we have used a transfection approach to evaluate the effects of gain- and loss-of-function expression of N-cadherin constructs on mesenchymal condensation and chondrogenesis in vitro. Chick limb mesenchymal cells were transfected by electroporation with recombinant expression plasmids encoding wild-type or two mutant extracellular/cytoplasmic deletion forms of N-cadherin. Expression of the transfected N-cadherin forms showed a transient profile, being high on days 1,2 of culture, and decreasing by day 3, fortuitously coincident with the temporal profile of endogenous N-cadherin gene expression. Examined by means of peanut agglutinin (PNA) staining for condensing precartilage mesenchymal cells, cultures overexpressing wild-type N-cadherin showed enhanced cellular condensation on culture days 2 and 3, whereas expression of the deletion mutant forms (extracellular/cytoplasmic) of N-cadherin resulted in a decrease in PNA staining, suggesting that a complete N-cadherin protein is required for normal cellular condensation to occur. Subsequent chondrogenesis was also affected. Cultures overexpressing the wild-type N-cadherin protein showed enhanced chondrogenesis, indicated by increased production of cartilage matrix (sulfated proteoglycans, collagen type II, and cartilage proteoglycan link protein), as well as increased cartilage nodule number and size of individual nodules, compared with control cultures and cultures transfected with either of the two mutant N-cadherin constructs. These results demonstrate that complete N-cadherin function, at the levels of both extracellular homotypic binding and cytoplasmic linkage to the cytoskeleton by means of the catenin complex, is required for chondrogenesis by mediating functional mesenchymal cell condensation. 2002 Wiley-Liss, Inc. [source]

Insulin-Like Growth Factor I Production Is Essential for Anabolic Effects of Thyroid Hormone in Osteoblasts,

Bill K. Huang
Abstract Thyroid hormone (T3) and insulin-like growth factor I (IGF-I) are critical regulators of skeletal function. T3 increases IGF-I production in bone. To assess the potential role of IGF-I as a mediator of T3 actions, we characterized phenotypic markers of osteoblast activity in two osteoblast models, normal mouse osteoblasts and MC3T3-E1 cells, exposed to T3 alone or under conditions that interfere with IGF-I actions. T3 significantly increased osteoblast 3H-proline incorporation, alkaline phosphatase (ALP), and osteocalcin. Both ,IR3, a neutralizing monoclonal antibody to the IGF-I receptor, and JB1, an IGF-I analogue antagonist, attenuated the stimulatory effects of T3. T3 effects also were decreased in cells transfected with antisense oligonucleotide (AS-ODN) to the IGF-I receptor gene. Both IGF-I and T3 had mitogenic effects that were inhibited by the antagonists. IGF-I by itself did not stimulate 3H-proline incorporation, ALP, and osteocalcin in the models used, revealing that although IGF-I is essential for the anabolic effects of T3, it acts in concert with other factors to elicit these phenotypic responses. (J Bone Miner Res 2000;15:188,197) [source]

A critical role of Cyr61 in interleukin-17,dependent proliferation of fibroblast-like synoviocytes in rheumatoid arthritis

Qiuyu Zhang
Objective Fibroblast-like synoviocytes (FLS) are a major component of the hyperplastic synovial pannus that aggressively invades cartilage and bone during the course of rheumatoid arthritis (RA). Cyr61 (CCN1) is a product of a growth factor,inducible immediate early gene and is involved in cell adhesion, proliferation, and differentiation. However, the role that Cyr61 plays in FLS proliferation has remained undetermined. The aim of this study was to identify the role of Cyr61 in regulating the proliferation of FLS derived from patients with RA. Methods Expression of Cyr61 in synovial tissue (ST) and in FLS was determined simultaneously using immunohistochemistry, real-time polymerase chain reaction, and Western blotting. Cyr61 levels in synovial fluid (SF) were determined by enzyme-linked immunosorbent assay. FLS proliferation stimulated by SF, Cyr61, and interleukin-17 (IL-17) was measured by thymidine incorporation. Activation of signal transduction pathways was determined by Western blotting and confocal microscopy. Results Cyr61 was overexpressed in ST, FLS, and SF samples from RA patients as compared with samples from normal controls. Elevated levels of Cyr61 in RA SF promoted the proliferation of FLS, an effect that was abrogated by a neutralizing monoclonal antibody against human Cyr61. Furthermore, in samples from RA patients, Cyr61 was found to protect FLS from apoptosis and to sustain the expression of Bcl-2 in FLS. Most importantly, the expression of Cyr61 in FLS was regulated by IL-17 mainly via the p38 MAPK and NF-,B signaling pathways. Knockdown of expression of the Cyr61 gene inhibited IL-17,stimulated FLS proliferation. Conclusion Our findings indicate that Cyr61 plays a critical role in IL-17,mediated proliferation of FLS in RA and likely contributes to hyperplasia of synovial lining cells and eventually to joint destruction in patients with RA. [source]

Prevention of glucocorticoid-induced bone loss in mice by inhibition of RANKL

Lorenz C. Hofbauer
Objective RANKL has been implicated in the pathogenesis of glucocorticoid-induced osteoporosis. This study was undertaken to evaluate the efficacy of denosumab, a neutralizing monoclonal antibody against human RANKL (hRANKL), in a murine model of glucocorticoid-induced osteoporosis. Methods Eight-month-old male homozygous hRANKL-knockin mice expressing a chimeric RANKL protein with a humanized exon 5 received 2.1 mg/kg of prednisolone or placebo daily over 4 weeks via subcutaneous slow-release pellets and were additionally treated with phosphate buffered saline or denosumab (10 mg/kg subcutaneously twice weekly). Two groups of wild-type mice were also treated with either prednisolone or vehicle. Results The 4-week prednisolone treatment induced loss of vertebral and femoral volumetric bone mineral density in the hRANKL-knockin mice. Glucocorticoid-induced bone loss was associated with suppressed vertebral bone formation and increased bone resorption, as evidenced by increases in the number of tartrate-resistant acid phosphatase (TRAP),positive osteoclasts, TRAP-5b protein in bone extracts, serum levels of TRAP-5b, and urinary excretion of deoxypyridinoline. Denosumab prevented prednisolone-induced bone loss by a pronounced antiresorptive effect. Biomechanical compression tests of lumbar vertebrae revealed a detrimental effect of prednisolone on bone strength that was prevented by denosumab. Conclusion Our findings indicate that RANKL inhibition by denosumab prevents glucocorticoid-induced loss of bone mass and strength in hRANKL-knockin mice. [source]