The Critical Role of IL-34 in Osteoclastogenesis

It has been widely believed that the cytokines required for osteoclast formation are M-CSF (also known as CSF-1) and RANKL. Recently, a novel cytokine, designated IL-34, has been identified as another ligand of CSF1R. This study was to explore the biological function, specifically osteoclastogenesis and bone metabolism, of the new cytokine. We produced recombinant mouse IL-34 and found that together with RANKL it induces the formation of osteoclasts both from splenocytes as well as dose-dependently from bone marrow cells in mouse and these cells also revealed bone resorption activity. It also promotes osteoclast differentiation from human peripheral blood mononucleated cells. Finally, we show that systemic administration of IL-34 to mice increases the proportion of CD11b+ cells and reduces trabecular bone mass. Our data indicate that IL-34 is another important player in osteoclastogenesis and thus may have a role in bone diseases. Strategies of targeting CSF1/CSF1R have been developed and some of them are already in preclinical and clinical studies for treatment of inflammatory diseases. Our results strongly suggest the need to revisit these strategies as they may provide a new potential pharmaceutical target for the regulation of bone metabolism in addition to their role in the treatment of inflammatory diseases

Analysis by siRNA_profile program displays novel thermodynamic characteristics of highly functional siRNA molecules

<p>Abstract</p> <p>Objective</p> <p>Here we report the improved results of a new siRNA design program and analysis tool called <b><it>siRNA_profile </it></b>that reveals an additional criterion for bioinformatic search of highly functional siRNA sequences.</p> <p>Methods</p> <p>We retrospectively analysed over 2400 siRNA sequences from 34 genes and with known efficacies to categorize factors that differentiate highly, moderately and non-functional siRNA sequences in more detail. We tested the biological relevance of <b><it>siRNA_profile </it></b>in CHO cells stably expressing human TRACP.</p> <p>Results</p> <p>The highly functional siRNA molecules exhibited lower overall stabilities than non-functional siRNAs after taking into consideration all the nucleotides from 5'-terminus to the 3'-terminus along the siRNA molecule, in addition to the 5'-section of the antisense strand and the region between 9–14 nucleotides as previously has been acknowledged. Comparison of the <b><it>siRNA_profile </it></b>program to five other programs resulted in a wide range of selected siRNA sequences with diverse gene silencing capacities, even when the target was only 197 nucleotides long. Six siRNA design programs selected 24 different siRNA sequences, and only 6 of them were selected by two or more programs. The other 18 sequences were individually selected by these six programs.</p> <p>Conclusion</p> <p>Low general stability of dsRNA plays a significant role in the RNAi pathway and is a recommended criterion to consider, in addition to 5'-instability, internal instability, nucleotide preferences and target mRNA position, when designing highly efficient siRNAs.</p

The effects of acute hyperinsulinemia on bone metabolism

Peer reviewe

Alendronate decreases orthotopic PC-3 prostate tumor growth and metastasis to prostate-draining lymph nodes in nude mice

<p>Abstract</p> <p>Background</p> <p>Metastatic prostate cancer is associated with a high morbidity and mortality but the spreading mechanisms are still poorly understood. The aminobisphosphonate alendronate, used to reduce bone loss, has also been shown to inhibit the invasion and migration of prostate cancer cells <it>in vitro</it>. We used a modified orthotopic PC-3 nude mouse tumor model of human prostate cancer to study whether alendronate affects prostate tumor growth and metastasis.</p> <p>Methods</p> <p>PC-3 cells (5 × 10⁵) were implanted in the prostates of nude mice and the mice were treated with alendronate (0.5 mg/kg/day in PBS, s.c.) or vehicle for 4 weeks. After sacrifice, the sizes of tumor-bearing prostates were measured and the tumors and prostate-draining regional iliac and sacral lymph nodes were excised for studies on markers of proliferation, apoptosis, angiogenesis and lymphangiogenesis, using histomorphometry and immunohistochemistry.</p> <p>Results</p> <p>Tumor occurrence in the prostate was 73% in the alendronate-treated group and 81% in the control group. Mean tumor size (218 mm³, range: 96–485 mm³, <it>n </it>= 11) in the alendronate-treated mice was 41% of that in the control mice (513 mm³, range: 209–1350 mm³, <it>n </it>= 13) (<it>p </it>< 0.05). In the iliac and sacral lymph nodes of alendronate-treated mice, the proportion of metastatic area was only about 10% of that in control mice (<it>p </it>< 0.001). Immunohistochemical staining of tumor sections showed that alendronate treatment caused a marked decrease in the number of CD34-positive endothelial cells in tumors (<it>p </it>< 0.001) and an increase in that of ISEL positive apoptotic cells in tumors as well as in lymph node metastases (<it>p </it>< 0.05) compared with those in the vehicle-treated mice. The density of m-LYVE-1-stained lymphatic capillaries was not changed.</p> <p>Conclusion</p> <p>Our results demonstrate that alendronate treatment opposes growth of orthotopic PC-3 tumors and decreases tumor metastasis to prostate-draining lymph nodes. This effect could be at least partly explained by decreased angiogenesis and increased apoptosis. The results suggest that bisphosphonates have anti-tumoral and anti-invasive effects on primary prostate cancer.</p

Biochemical markers of bone turnover are influenced by recently sustained fracture.

Abstract is not available. This is the final accepted and revised manuscript of the article

Inhibition of the osteoclast V-ATPase by small interfering RNAs

AbstractThe multisubunit enzyme V-ATPase harbours isoforms of individual subunits. a3 is one of four 116kDa subunit a isoforms, and it is crucial for bone resorption. We used small interfering RNA (siRNA) molecules to knock down a3 in rat osteoclast cultures. Labeled siRNA-molecules entered osteoclasts via endocytosis and knocked down the a3 mRNA. Bone resorption was decreased in siRNA-treated samples due to decreased acidification and osteoclast inactivation. Expression of a1 did not respond to decreased a3 levels, suggesting that a1 does not compensate for a3 in osteoclast cultures. Subunit a3 is thus an interesting target for novel nucleic acid therapy

Serial assessment of serum bone metabolism markers identifies women with the highest rate of bone loss and osteoporosis risk.

Context: One of the important challenges in the management of osteoporosis is to identify women who are at high risk of developing osteoporosis and fragility fractures. Objective: To evaluate if assessment of bone metabolism at multiple occasions can identify women with the highest risk for bone loss. Design: The Malmö OPRA study is an ongoing longitudinal study. Participants have been evaluated at baseline and after 1, 3 and 5 years. Setting: Population-based study. Participants: 1044 women, all 75 years old at baseline. Main outcome measures: Seven bone turnover markers were assessed at baseline, 1, 3 and 5 years (n=573). Five year change in areal bone mineral density (aBMD) was also determined. Results: Baseline markers correlated weakly to change in total body aBMD. The associations were more pronounced when the average of the baseline and 1-year measurements was used (standardized regression coefficients -0.12 to -0.23, p<0.01). Adding the 3-year and 5-year measurement further strengthened the correlation (regression coefficients up to -0.30 (p<0.001)). Women with constantly high turnover lost significantly more bone at total body (-2.6%) than women with intermediate (-1.6%) or low turnover (-0.2%, p for trend <0.001). They also had a greater decrease in hip BMD (-8.3%, -6.0% and -5.1%, respectively, p=0.010). Results were similar also in the subgroup of women with osteopenia. Conclusions: Our results suggest that serial assessment of bone turnover improves the identification of women with the highest rate of bone loss and osteoporosis risk

The effects of tamoxifen and toremifene on bone cells involve changes in plasma membrane ion conductance

Selective estrogen receptor modulators (SERMs), tamoxifen (Tam) and toremifene (Tor), are widely used in the treatment of breast cancer. In addition, they have been demonstrated to prevent estrogen deficiency-induced bone loss in postmenopausal women. These effects are thought to be caused by the interaction of the SERMs with the estrogen receptor, although SERMs have also been shown to conduct non-receptor-mediated effects such as rapid changes in membrane functions. We compared the effects of Tam, Tor, and 17β-estradiol (E2) on the viability of rat osteoclasts and osteoblasts. Both Tam and Tor were found to cause osteoclast apoptosis in in vitro cultures, which was reversed by E2. In addition, at higher concentration (10 μM), both SERMs had an estrogen receptor-independent effect, which involved interaction with the plasma membrane as demonstrated with UMR-108 osteosarcoma cells by Tam and Tor, but not E2. A leak of protons leading to changes in intracellular pH was shown both in medullary bone derived membrane vesicles and in intact cells. These effects were followed by a rapid loss of cell viability and subsequent cell lysis. Our results show that both Tam and Tor have an ionophoric effect on the plasma membranes of bone cells and that these SERMs differed in this ability: Tor induced rapid membrane depolarization only in the presence of high concentration of potassium. These non-receptor-mediated effects may be involved in therapeutic responses and explain some clinical side effects associated with the treatment of patients with these SERM