CMT3 alters mitochondrial function in murine osteoclast lineage cells

A Novel Analysis via Micro-CT Imaging Indicates That Chemically Modified Tetracycline-3 (CMT-3) Inhibits Tooth Relapse after Orthodontic Movement: A Pilot Experimental Study

Objective

To evaluate the effect of chemically modified tetracycline-3 (CMT-3) and simvastatin on tooth relapse after orthodontic movement in rats using a novel analysis method employing high-resolution micro-CT (Micro-CT) images. In addition, the correlation between bone density and orthodontic relapse was also evaluated for each experimental group.

Methods

Forty adult male Wistar rats had stainless steel springs installed on their left upper first molars in order to generate tooth movement for 18 days. After this initial period, the animals were divided into three groups: (1) 30 mg/kg of CMT-3; (2) 5 mg/kg of simvastatin; and (3) 0.5% carboxymethylcellulose, and each group was treated for 20 days. Micro-CT images were analyzed (conventional method and 3D reconstruction) on the 7th and 18th days following spring fixation and finally, 20 days after treatment either with CMT-3 or simvastatin (38th day). Bone mineral density (BMD) of the mesial and distal roots of the upper first molar was also analyzed.

Results

The difference was statistically significant between the groups as to recurrence (p=0.048), and the post hoc test identified the value of p=0.007 between the control group and the CMT-3 group. Simvastatin was not able to inhibit tooth relapse. The bone mineral densities of both the mesial and distal roots were different between the three groups, after the 20th day of drug use (p=0001 and p < 0001).

Conclusion

Our findings support the initial evidence that CMT-3 is able to prevent relapse after tooth movement. Future trials in humans should evaluate such treatment as a promising approach to preventing this common phenomenon.

Clinical Relevance

Considering the results obtained, CMT-3 can be used to avoid relapse after tooth movement.

Effects of 1α,25-(OH)2D3 on the formation and activity of osteoclasts in RAW264.7 cells

The hormonally active form of vitamin D3, 1α,25-(OH)2D3, has an important role in bone metabolism. This study examined the effects of 1α,25-(OH)2D3 on the ability of two cytokines, receptor activator of nuclear factor-κB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), to induce RAW 264.7 cells to form osteoclasts. A TRAP histochemical staining assay and bone resorption analysis were used to identify the rate of formation and activity of osteoclasts. The numbers of osteoclasts formed, and their bone resorption activity, was enhanced by the addition of 1α,25-(OH)2D3. The expression levels of osteoclast-specific proteins that are essential for bone resorption, integrin β3, V-ATPase, CAII, CTSK, TRAP and MMP-9, were detected by western blotting. During 48 h, the expression levels of all these proteins significantly increased. Quantitative real-time polymerase chain reaction was used to determine the expression levels of the transcription factors, c-Fos and NFATcl. The expression levels of c-Fos and NFATc1 also increased 24h after treatment with 1α,25-(OH)2D3. These results suggest that 1α,25-(OH)2D3 can regulate bone metabolism by directly enhancing the formation and maturation of osteoclasts.

The effect of poly(d,l-lactide-co-glycolide)-alendronate conjugate nanoparticles on human osteoclast precursors

Nanoparticles (NPs) formed from polymers conjugated with bisphosphonates (BPs) allow the bone targeting of loaded drugs, such as doxorubicin, for the treatment of skeletal tumours. The additional antiosteoclastic effect of the conjugated BP could contribute to the inhibition of tumour-associated bone degradation. With this aim, we have produced NPs made of poly(d,l-lactide-co-glycolide) (PLGA) conjugated with alendronate (ALE). To show if ALE retained the antiosteoclastic properties after the conjugation with PLGA and the production of NPs, we treated human osteoclasts, derived from circulating precursors, with PLGA-ALE NPs and compared the effects on actin ring generation, apoptosis and type-I collagen degradation with those of free ALE and with NPs made of pure PLGA. PLGA-ALE NPs disrupted actin ring, induced apoptosis and inhibited collagen degradation. Unexpectedly, also NPs made of pure PLGA showed similar effects. Therefore, we cannot exclude that in addition to the observed antiosteoclastic activity dependent on ALE in PLGA-ALE NPs, there was also an effect due to pure PLGA. Still, as PLGA-ALE NPs are intended for the loading with drugs for the treatment of osteolytic bone metastases, the additional antiosteoclastic effect of PLGA-ALE NPs, and even of PLGA, may contribute to the inhibition of the disease-associated bone degradation.

Tetracyclines inhibit rat osteoclast formation and activity in vitro and affect bone turnover in young rats in vivo

An experiment was designed to investigate whether systemic administration of tetracyclines (TCs) as bone fluorochrome labels could interfere with bone modeling in vivo and inhibit osteoclast formation and activity in vitro. Cell cultures of rat bone marrow macrophages revealed that TC and oxytetracycline inhibited osteoclastogenesis and bone resorption and stimulated apoptosis. Forty rats in five groups were treated with saline, calcein green, alizarin red S, TC, or oxytetracycline. Their tibias were used for histomorphometric analysis, including bone static, dynamic, and resorption parameters in the tibial proximal metaphysis. No significant differences in bone volume per tissue volume, trabecular number, trabecular thickness, trabecular separation, bone formation rate per bone surface, mineralizing surface, or mineral apposition rate were observed. TC or oxytetracycline decreased eroded surface, number of osteoclasts per bone perimeter, and osteoclast surface per bone surface by about 50%. The results demonstrated that TC and oxytetracycline inhibit rat osteoclast formation and activity in vitro, and histomorphometric parameters involved in bone turnover may be affected by the use of oxytetracycline and TC as fluorescent bone labels in vivo.