Potential synergies between matrix proteins and soluble factors on resorption and proteinase activities of rabbit bone cells

Human growth hormone (GH) has recently been found to stimulate osteoclastic resorption, cysteineproteinase and metalloproteinase activities (MMP-2 and MMP-9) in vitro via insulin-like growth factor-1 (IGF-1) produced by stromal cells. The present study investigated the effects of two extracellular matrix components (vitronectin and type-1 collagen) on hGHand hIGF-1-stimulated osteoclastic resorption and proteinase activities in a rabbit bone cell model. After 4 days of rabbit bone cell culture on dentin slices with vitronectin coating, hGH and hIGF-1 stimulated bone resorption and hIGF-1 upmodulated cysteine-proteinase activities. MMP-2 expression (but not resorption, cathepsin or MMP-9 activities) was upmodulated by hGH and hIGF-1 on dentin slices coated with type 1 collagen as compared to those without coating. Then, vitronectin was synergistic with hIGF-1 in the regulation of cysteine-proteinase production whereas collagen showed synergy with hGH and hIGF-1 in the regulation of MMP-2 production. Anti-αvβ3 totally abolished the effects of hGH and hIGF-1 on metalloproteinase release, but had no influence on cathepsin release. The results suggest that cysteine-proteinase modulation is not mediated by αvβ3 integrin (strongly expressed on osteoclastic surface) whereas the resorption process and metalloproteinase modulation are clearly'mediated by this integrin. Our finding about the collagen coating also suggests that hGH- and hIGF-1-stimulated MMP-2 activity are mediated, along with αvβ3 integrin, by another adhesion molecule

Receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio is increased in severe osteolysis

Pathological osteolyses are considered a consequence of a disturbance in the mechanisms that govern the bone remodeling, mainly the communication between osteoclasts and osteoblasts. Osteoprotegerin (OPG) and receptor activator of NF-kappaB ligand (RANKL) are newly discovered molecules that play a key role in these communications. RANKL is essential for osteoclast differentiation via its receptor RANK located on the osteoclast membrane. OPG is a soluble decoy receptor that inhibits osteoclast differentiation through its binding to RANKL. The aim of this study is the analysis of the RANKL/OPG balance by complementary methods (semiquantitative reverse transcription-polymerase chain reaction, immunohistochemistry, and enzyme-linked immunosorbent assay) in human osteolysis associated to various bone etiologies (n = 60), tumoral (primitive, secondary) or not, compared to healthy tissues (n = 16). Results demonstrated that RANKL/OPG ratio was significantly increased in patients suffering from severe osteolysis compared to the control group and that this imbalance is involved in bone resorption mechanisms. In this study, OPG expression appears to reflect a protective mechanism of the skeleton to compensate increased bone resorption by inhibiting osteoclast formation and bone resorbing activity. Moreover, as revealed by immunohistochemistry, RANKL and OPG were colocalized in all of the tissues analyzed. To define the veracity of RANKL/OPG index in assessing and managing patients with severe osteolysis, an extended population of patients suffering from severe osteolysis must be now monitored

Fabrication of Macrochannelled-Hydroxyapatite Bioceramic by a Coextrusion Process

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65282/1/j.1151-2916.2002.tb00500.x.pd

Spondylodiscitis due to Propionibacterium acnes: report of twenty-nine cases and a review of the literature.

International audiencePropionibacterium acnes is the most frequent anaerobic pathogen found in spondylodiscitis. A documented case required microbiological proof of P. acnes with clinical and radiological confirmation of inflammation in a localized region of the spine. Microbiological samplings were obtained by surgery or aspiration under radiological control. Twelve males and 17 females (median age, 42 years) with spondylodiscitis due to P. acnes were diagnosed within the last 15 years. Three patients were immunosuppressed. All patients reported back pain as the main symptom, and most were afebrile. Three patients had a peripheral neurological deficit, one a motor deficit, and two a sensory deficit attributable to the infection; and six patients had an epidural abscess. The most frequent risk factor was surgery, which was present in the history 28 of 29 (97%) patients. The mean delay between spinal surgery and onset of disease was 34 months, with a wide range of 0-156 months. Osteosynthesis material was present in twenty-two cases (76%). In 24 (83%) patients, additional surgery, such as débridement or spondylodesis, was performed. Previous osteosynthesis material was removed in 17 of the 22 (77%) patients where it was present. Total cure was reported in all patients, except one, after a mean duration of antibiotic therapy of 10.5 weeks (range, 2-28 weeks). In conclusion, spondylodiscitis due to P. acnes is an acute infection closely related to previous surgery. The most prominent clinical feature is pain, whereas fever is rare, and the prognosis is very good