Mechanical fragmentation and transportation of calcium phosphate substrate by filopodia and lamellipodia in a mature osteoclast.

The functions of filopodia and lamellipodia in mature osteoclasts are not well known in the process of bone resorption. We investigated the function of filopodial/lamellipodial movement in mature osteoclasts by video-enhanced contrast-differential interference contrast (VEC-DIC) microscopy. Mature osteoclasts, which were isolated from Japanese white rabbits, were cultured on calcium phosphate (CP)-coated quartz coverslips to observe filopodial/lamellipodial movement and the formation of CP-free areas precisely. Filopodia broke the CP substrate into pieces and transported them to the cell body by capturing them at the tip. Lamellipodia destroyed the CP substrate, and transported it to the cell body by capturing small particles in a mass. This study suggests two functions of filopodia and lamellipodia in mature osteoclasts, i.e., the mechanical fragmentation of the CP substrate and the transportation of the CP particles to the cell body.

The effect of infliximab on bone metabolism markers in patients with rheumatoid arthritis.

OBJECTIVE: The aim of this study was to evaluate urinary excretion of N-telopeptide of type I collagen (NTX) and deoxypyridinoline (DPD), markers of bone resorption, and serum bone alkaline phosphatase (BAP) level, a marker of bone formation and an early marker of osteoblast differentiation, in patients with rheumatoid arthritis (RA) treated with infliximab. METHODS: Seventeen male and female patients (age 60.7+/-2.53 yr; mean disease duration 12.9+/-3.01 yr; Steinbrocker's class II-IV) with RA, diagnosed according to the criteria of the American College of Rheumatology (ACR), took part in the study between March 2003 and January 2005. None of the patients had a history of oestrogen replacement therapy. All patients were treated with infliximab combined with methotrexate. Infliximab was infused intravenously at 3 mg/kg at baseline, 2 and 6 weeks, then every 8 weeks. To evaluate disease activity, ESR, CRP, the numbers of swollen and tender joints, modified Stanford Health Assessment Questionnaire (mHAQ) score and ACR score were measured. Levels of NTX and DPD in urine and BAP in serum were measured in all patients. RESULTS: ESR, CRP, the number of swollen joints and tender joints, and mHAQ score had decreased significantly 6 weeks after initial treatment and were still low 6 months after initial treatment. NTX levels had decreased significantly 6 weeks after the initial treatment and were still low 6 months after initial treatment. DPD levels had decreased 6 months after initial infusion. Mean serum BAP level did not differ significantly among the three time points. NTX levels were statistically corresponding with the number of swollen joints and mHAQ scores. DPD levels were statistically lower corresponding with ESR. CONCLUSION: Infliximab therapy may inhibit generalized bone loss in patients with RA. NTX is a more sensitive marker than DPD.