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RANKL Increase in Compressed Periodontal Ligament Cells from Root Resorption

Department of Orthodontics, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-Nishi, Matsudo City, Chiba 271-8587, Japan

View larger version (20K): [in this window] [in a new window]   Figure 1. Effects of incubation time with compressive force on sRANKL (A) and OPG (B) production in conditioned media of human PDL cells. Production of these cytokines was assayed as described in MATERIALS & METHODS. Data are expressed as the mean ± SD of 5 independent cultures. Cytokine production was changed by application of compressive force (2.0 g/cm2), and the pattern was time-dependent (p < 0.001, by two-way ANOVA). Significantly different from the corresponding control at each incubation time: *p < 0.001. Significantly different from non-resorption (with compressive force) at each incubation time: #p < 0.001.

View larger version (24K): [in this window] [in a new window]   Figure 2. Effects of different magnitudes of compressive force on sRANKL (A) and OPG (B) production by human PDL cells. Human PDL cells were cultured with or without the indicated magnitudes of compressive force for 12 hrs. Data are expressed as the mean ± SD of 5 independent cultures. The cytokines were changed by application of compressive force in a force-magnitude-dependent manner (p < 0.001, by two-way ANOVA). Significantly different from the corresponding control: *p < 0.001. Significantly different from non-resorption (with compressive force) at each magnitude: #p < 0.001.

View larger version (12K): [in this window] [in a new window]   Figure 3. The number of TRAP-positive cells and the pit formation on dentin slices on the addition of conditioned medium or by co-culture of osteoclast precursor cells and compressed PDL cells. (A,B) Human osteoclast precursor cells cultured in commercial medium (-MEM supplemented with 10 unit/mL of penicillin, 10 µg/mL of gentamicin, and 10% fetal calf serum) with both macrophage colony-stimulating factor (M-CSF) and RANKL (both at 10 ng/mL) for 8 days. After the osteoclasts matured, the medium was changed to that obtained from human PDL cells after incubation with or without compressive-force-conditioned medium (2.0 g/cm2) for 12 hrs. The numbers of TRAP-positive cells (A) and resorption pits (B) were significantly increased by the conditioned medium (with compressive force) as compared with those in the respective controls (without compressive force). Further, the numbers of TRAP-positive cells and resorption pits were more abundant in the severe root resorption group (with compressive force) than in the non-resorption group (with compressive force). (C) Co-culture with compressed PDL cells (2.0 g/cm2, 12 hrs) activated the differentiation of osteoclast precursor cells into mature osteoclasts for 8 days. The number of TRAP-positive cells in the compressed PDL cells was significantly differenr from that in the non-compressed PDL cells in both the severe root resorption and non-resorption groups. Furthermore, the increase was greater in the severe root resorption group than in the non-resorption group. We measured the numbers of TRAP-positive cells and resorption pits, and subjected them to statistical analysis. Data are expressed as the mean ± SD of 5 independent cultures. Significantly different from the corresponding control (*p < 0.001). Significantly different from non-resorption (with compressive force) (#p < 0.001).

View larger version (28K): [in this window] [in a new window]   Figure 4. The expression of RANKL protein increased with compressive force. PDL cells obtained from normal resorption and severe resorption groups were exposed to compressive force (2.0 g/cm2) for 12 hrs, and then whole-cell lysate from the cells was subjected to Western blot analysis with antibody against RANKL.

Journal of Dental Research, Vol. 85, No. 8, 751-756 (2006)
DOI: 10.1177/154405910608500812


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