Akihide Nampei

Matrix extracellular phosphoglycoprotein (MEPE) is highly expressed in osteocytes in human bone

The matrix extracellular phosphoglycoprotein (MEPE) gene is highly expressed in tumors that cause oncogenic hypophosphatemic osteomalacia (OHO). MEPE is also known as one of the bone-tooth matrix proteins and is associated with bone mineralization. We developed a rabbit polyclonal antibody directed against recombinant human MEPE (rhMEPE) after cloning its cDNA from the cDNA library of a nasal tumor tissue causing OHO. Using this antibody, we analyzed the distribution of MEPE in human bones by immunohistochemistry. In bone specimens from normal subjects, MEPE was predominantly expressed by osteocytes and not by osteoblasts. In bone specimens from patients with osteomalacia, however, MEPE was focally expressed by deeply located osteocytes. We also compared the MEPE positivity of osteocytes in mineralized bone and non-mineralized osteoid obtained from patients with osteomalacia and osteoporosis. Among osteomalacia patients, MEPE positivity was seen in 87.5 ± 8.6% of the osteocytes from mineralized bone compared with 7.8 ± 6.4% of those from osteoid. Among osteoporosis patients, MEPE positivity was found in 95.3 ± 0.5% of the osteocytes from mineralized bone compared with 4.9 ± 5.7% of those from osteoid. MEPE was mainly expressed by osteocytes embedded in the matrix of mineralized bone from patients with osteomalacia or osteoporosis. Our data provide the first histological evidence that MEPE is predominantly expressed by osteocytes in human bone, with significant expression by osteocytes within mineralized bone.

Imatinib mesylate inhibits osteoclastogenesis and joint destruction in rats with collagen-induced arthritis (CIA).

Macrophage colony-stimulating factor (M-CSF) is a key factor for osteoclastogenesis at the bone–pannus interface in patients with rheumatoid arthritis as well as a receptor activator of NF-κB ligand (RANKL). Imatinib mesylate inhibits the phosphorylation of c-fms, a receptor for M-CSF. The present study investigates the effect of imatinib mesylate on joint destruction in rats with collagen-induced arthritis (CIA) and on osteoclastogenesis in vitro. Imatinib mesylate (50 or 150 mg/kg), dexamethasone, or vehicle was administered daily to CIA rats for 4 weeks from the onset of arthritis. Hind-paw swelling and body weight were measured weekly. At weeks 2 and 4, the metatarsophalangeal (MTP) joints and the ankle and subtalar joints were radiographically and histologically assessed. The effect of imatinib mesylate on osteoclast formation from rat bone marrow cells with M-CSF and soluble RANKL (sRANKL) in vitro was also examined. Radiographic assessment showed that 150 mg/kg imatinib mesylate suppressed the destruction of the MTP and the ankle and subtalar joints at week 2, and MTP joint destruction at week 4 in CIA rats, although hind-paw swelling was not suppressed. The number of TRAP-positive cells at the bone–pannus interface was significantly reduced in the group administered with 150 mg/kg imatinib mesylate compared with that given vehicle at week 4. Imatinib mesylate dose-dependently inhibited the proliferation of M-CSF-dependent osteoclast precursor cells in vitro as well as osteoclast formation induced by M-CSF and sRANKL. These findings suggest that imatinib mesylate could prevent joint destruction in patients with rheumatoid arthritis.

Laboratory and febrile features after joint surgery in patients with rheumatoid arthritis treated with tocilizumab

Objectives: To understand the acute phase responses to surgical intervention in patients with rheumatoid arthritis (RA) treated with the anti-interleukin (IL)6 receptor antibody, tocilizumab. Methods: In a retrospective 1:1 pair-matched case-control study, 22 tocilizumab-treated RA cases and 22 cases treated with conventional disease-modifying antirheumatic drugs (DMARDs) and matched for type of surgery, age and sex were evaluated for body temperature every day, and blood C-reactive protein (CRP) levels and white blood cell (WBC), neutrophil and lymphocyte counts on days −1, 1, 3 and weeks 1 and 2 after joint surgery. Safety issues were also monitored. Results: No complications of infection or delay of wound healing occurred in either patient group. Tocilizumab partially, but significantly, suppressed the increase in body temperature on postoperative days 1 and 2, compared with DMARDs (average (SD) maximum increase in temperature was 0.45 (0.1)°C in the tocilizumab group and 0.78 (0.1)°C in the DMARD group; p<0.01). Tocilizumab completely suppressed the increase in CRP after surgery, whereas all cases treated with DMARDs showed a significant increase of CRP at postoperative day 1 (5.5 (0.6) mg/dl; p<0.001). WBC, neutrophil and lymphocyte counts showed no remarkable change after surgery, and there was no significant difference in any cell counts between the patient groups. Conclusions: Within this small number of cases, safe operations on patients were performed during tocilizumab treatment. Tocilizumab suppressed fever and increase of CRP after surgery, whereas there was no influence on the transition in number of leukocytes. This characteristic postoperative response should be considered during tocilizumab treatment.

Laboratory and febrile features after joint surgery in rheumatoid arthritis patients treated with tocilizumab

Objectives: To understand the acute phase responses to surgical intervention in patients with rheumatoid arthritis (RA) treated with the anti-interleukin (IL)6 receptor antibody, tocilizumab. Methods: In a retrospective 1:1 pair-matched case-control study, 22 tocilizumab-treated RA cases and 22 cases treated with conventional disease-modifying antirheumatic drugs (DMARDs) and matched for type of surgery, age and sex were evaluated for body temperature every day, and blood C-reactive protein (CRP) levels and white blood cell (WBC), neutrophil and lymphocyte counts on days −1, 1, 3 and weeks 1 and 2 after joint surgery. Safety issues were also monitored. Results: No complications of infection or delay of wound healing occurred in either patient group. Tocilizumab partially, but significantly, suppressed the increase in body temperature on postoperative days 1 and 2, compared with DMARDs (average (SD) maximum increase in temperature was 0.45 (0.1)°C in the tocilizumab group and 0.78 (0.1)°C in the DMARD group; p<0.01). Tocilizumab completely suppressed the increase in CRP after surgery, whereas all cases treated with DMARDs showed a significant increase of CRP at postoperative day 1 (5.5 (0.6) mg/dl; p<0.001). WBC, neutrophil and lymphocyte counts showed no remarkable change after surgery, and there was no significant difference in any cell counts between the patient groups. Conclusions: Within this small number of cases, safe operations on patients were performed during tocilizumab treatment. Tocilizumab suppressed fever and increase of CRP after surgery, whereas there was no influence on the transition in number of leukocytes. This characteristic postoperative response should be considered during tocilizumab treatment.

Tartrate resistant acid phosphatase (TRAP) positive cells in rheumatoid synovium may induce the destruction of articular cartilage

Objective: To examine the role of tartrate resistant acid phosphatase (TRAP) positive mononuclear and multinucleated cells in the destruction of articular cartilage in patients with rheumatoid arthritis (RA). Methods: The presence of TRAP positive cells in the synovial tissue of patients with RA was examined by enzyme histochemistry and immunohistochemistry. Expression of mRNAs for matrix metalloproteinases (MMPs) was assessed by the reverse transcriptase-polymerase chain reaction (RT-PCR) and northern blot analysis. Production of MMPs by mononuclear and multinucleated TRAP positive cells was examined by immunocytochemistry, enzyme linked immunosorbent assay (ELISA) of conditioned medium, and immunohistochemistry of human RA synovial tissue. In addition, a cartilage degradation assay was performed by incubation of 35S prelabelled cartilage discs with TRAP positive cells. Results: TRAP positive mononuclear cells and multinucleated cells were found in proliferating synovial tissue adjacent to the bone-cartilage interface in patients with RA. Expression of MMP-2 (gelatinase A), MMP-9 (gelatinase B), MMP-12 (macrophage metalloelastase), and MMP-14 (MT1-MMP) mRNA was detected in TRAP positive mononuclear and multinucleated cells by both RT-PCR and northern blot analysis. Immunocytochemistry for these MMPs showed that MMP-2 and MMP-9 were produced by both TRAP positive mononuclear and multinucleated cells, whereas MMP-12 and MMP-14 were produced by TRAP positive multinucleated cells. MMP-2 and MMP-9 were detected in the conditioned medium of TRAP positive mononuclear cells. TRAP positive mononuclear cells also induced the release of 35S from prelabelled cartilage discs. Conclusion: This study suggests that TRAP positive mononuclear and multinucleated cells located in the synovium at the cartilage-synovial interface produce MMP-2 and MMP-9, and may have an important role in articular cartilage destruction in patients with RA.

Serum level of oxidative stress marker is dramatically low in patients with rheumatoid arthritis treated with tocilizumab

Regarding the pathobiology of rheumatoid arthritis, oxidative stress induced by reactive oxygen species is an important mechanism that underlies destructive and proliferative synovitis. Abundant amounts of reactive oxygen species have been detected in the synovial fluid of inflamed rheumatoid joints. It is reported that drugs that block tumor necrosis factor-α reduce the oxidative stress marker levels in patients with rheumatoid arthritis. In this study, we measured reactive oxygen species using a free radical analytical system in patients with rheumatoid arthritis treated with disease-modifying antirheumatic drugs, tumor necrosis factor-α-blocking drugs (infliximab, etanercept), and an interleukin-6-blocking drug (tocilizumab). The serum level of oxidative stress was drastically low in patients with rheumatoid arthritis treated with tocilizumab, suggesting that interleukin-6 blocking therapy reduces not only joint damage, but also vascular degeneration in patients with rheumatoid arthritis. We believe that such a drastic effect would reduce the incidence of cardiovascular events and mortality in patients with rheumatoid arthritis.

High oxygen tension prolongs the survival of osteoclast precursors via macrophage colony-stimulating factor.

The oxygen tension affects the function, differentiation, and transformation of various cells, including bone cells. In pathological conditions such as rheumatoid arthritis (RA), rapidly destructive arthropathy, and primary or metastatic tumors, severe bone destruction or osteolysis occurs. Abundant blood vessels are often observed around these destructive lesions. At such sites, we have confirmed the increased production of reactive oxygen species (ROS) induced by a high oxygen tension and/or oxidative stress, as well as numerous osteoclasts detectable by immunohistochemistry. These findings suggest that osteoclasts are influenced by the high oxygen tension in pathological bone lesions because the zone around blood vessels has a relatively high oxygen tension. In this study, we investigated the effects of oxygen tension on osteoclastogenesis by culturing human CD14-positive cells (osteoclast precursors) with or without osteoblast-like supporting cells (Saos-4/3 cells) under a normal oxygen tension (20% O(2)) or a high oxygen tension (40% O(2)). A high oxygen tension markedly prolonged the duration of osteoclast precursor formation in the presence of supporting cells, and also markedly and persistently increased the production of macrophage colony stimulating factor (M-CSF) by supporting cells. Furthermore, we found an increase of cells expressing M-CSF and cells positive for tartrate-resistant acid phosphatase (TRAP) in hypervascular destructive bone lesions of RA patients where ROS were also abundant.

Diagnostic features of mild cellulitis phlegmon in patients with rheumatoid arthritis treated with tocilizumab: a report of two cases

Two cases of subcutaneous soft tissue infection in 30 RA patients treated with tocilizumab are reported. In both patients, local redness, swelling, and heat were observed around the affected site. WBC spikes and such local findings were suggested to be clinically useful for the early detection of low-grade subcutaneous infection in RA patients whose disease is tightly controlled with tocilizumab. Of note, the C-reactive protein (CRP) level and temperature lacked clinical utility for such detection.

The efficacy and safety of additional administration of tacrolimus in patients with rheumatoid arthritis who showed an inadequate response to tocilizumab.

Abstract Objectives: Tocilizumab (TCZ) shows good retention in patients with rheumatoid arthritis (RA), but no previous reports demonstrated hopeful treatment options against inadequate response to TCZ. Tacrolimus (TAC) has proved to show efficacy against inadequate response to tumor necrosis factor alpha inhibitors, yet its add-on effects on TCZ remain unknown. Methods: Twenty patients with RA (17 women, age 58.6 years, disease duration 12.1 years, prior TCZ duration 2.6 years, 18 intravenous [8 mg/kg/month] and 2 subcutaneous [324 mg/month] TCZ treatments, methotrexate 6.1 mg/week [70.0%]) who showed an inadequate response to TCZ (clinical disease activity index [CDAI] ≥ 5.8, 18 secondary non-responders) were additionally treated with TAC (1.1 mg/day), and enrolled in this 24-week, prospective study. Results: Seventeen patients (85.0%) continued the treatment for 24 weeks. Statistically significant decreases in outcome measures were as follows: disease activity score based on 28 joints with C-reactive protein (DAS28-CRP) from 3.3 at baseline to 2.1 at week 24 (p < 0.001), CDAI from 17.7 to 7.6 (p < 0.001), and serum matrix metalloproteinase-3 levels from 232.8 to 66.2 ng/ml (p < 0.001). About 15 patients (75%) achieved low disease activity or remission (DAS28-CRP ≤2.7 or CDAI ≤10) at week 24. Conclusions: Adding low-dose TAC to inadequate responders to TCZ may be a promising complementary treatment option.

Treatment of juxta-articular intraosseous cystic lesions in rheumatoid arthritis patients with interconnected porous calcium hydroxyapatite ceramic.

In patients with rheumatoid arthritis (RA), juxta-articular intraosseous cystic lesions may cause spontaneous pathological fractures. The outcome of curettage and the packing of such lesions with interconnected porous calcium hydroxyapatite ceramic (IP-CHA) was investigated. Twelve lesions were treated in ten RA patients (three men and seven women with a mean age of 59 years). Ten lesions were associated with impending pathological fracture involving the articular surface. In all patients, curettage and packing of the bone cavity with IP-CHA were done. Assessment was based on final radiographs obtained an average of 30 months after surgery (range 10–47 months). Absorption of the implanted IP-CHA, expansion of the lesion, implant incorporation into host bone, and postoperative fractures were investigated. At final follow-up, there was no absorption of the implanted IP-CHA in any of the lesions. Expansion of the radiolucent area was only noted in one lesion. Seven of the other 11 lesions showed major incorporation of IP-CHA into host bone, while minor incorporation was seen in four lesions. There were no postoperative fractures. In conclusion, curettage and packing with IP-CHA is a feasible method of preventing pathological fracture due to juxta-articular intraosseous cystic lesions in RA patients.