Hiroko Matsumoto

Effect of calcium-channel blockers on cell proliferation, DNA synthesis and collagen synthesis of cultured gingival fibroblasts derived from human nifedipine responders and non-responders.

Human gingival fibroblasts from six patients who developed gingival hyperplasia as a result of nifedipine medication and five who did not were studied for the effects of calcium-channel blockers (nifedipine, diltiazem, verapamil and nicardipine) on cell proliferation, DNA synthesis and collagen synthesis. Phenytoin was used as a positive control. The fibroblasts from reactive patients gave trends toward better cell proliferation rates, DNA synthesis ([3H]-thymidine incorporation), and collagen synthesis ([3H]-proline incorporation) than those from non-reactive patients in the presence of 1 microM of calcium-channel blockers or phenytoin.

Mandible bone loss in osteoporosis rats.

Change in the mandible during the development of osteoporosis has not been studied extensively. Thus, the present study was undertaken to clarify the target loci in the mandible during the development of experimental osteoporosis in aged female rats. Experimental osteoporosis was studied in 76 Wistar strain female rats, 35 weeks old, by means of ovariectomy and dietary calcium deficiency. The rats were divided into the following three groups: (1) group 1, unoperated basal control (Basal), maintained on a diet containing 1.0% calcium; (2) group 2, sham-operated (Sham), maintained on a diet containing 0.01% calcium; and (3) group 3, ovariecomized (OVX), maintained on a diet containing 0.01% calcium. Fifteen rats of each group, except the basal rats (10 and 6 rats), were killed at 3 and 6 months following ovariectomy, respectively. The mandible was extracted, cleaned, and then subjected to bone mineral content (BMC) and bone mineral density (BMD) analyses using a peripheral quantitative computed tomography (pQCT) bone scanner. Each mandible was scanned from the mesial margin of the first molar to distal margin of the second molar. The results showed that dietary calcium deficiency and ovariectomy caused significant decreases of trabecular and cortical BMCs and BMDs in Sham and OVX rats compared with Basal rats. Decreases due to dietary calcium deficiency were greater than those caused by ovariectomy. However, significant age-related changes were not observed in BMC and BMD in Sham and OVX rats for 3–6 months. In addition, the cortical and trabecular BMCs and BMDs obtained were found to relate to location in the mandible for each group.

Effect of vitamin B complex on neurotransmission and neurite outgrowth

1. The effect of vitamin B complex (vitamin B1, B6 and B12) was studied on nerve conduction velocity in acrylamide-neuropathy rats maintained on refined semisynthetic complete vitamin and vitamin B-deficient diets in vivo and on neurite outgrowth in vitro using cells obtained from dorsal root ganglions of mice. 2. Acrylamide neuropathy was clearer in the group maintained on a refined semisynthetic vitamin B-deficient diet than in those on a refined semisynthetic complete vitamin diet. The neurotoxicity was lowest in the group given vitamin B complex prophylactic-therapeutically, next higher following therapeutic administration and last with no vitamin B complex administration in both groups maintained on a refined semisynthetic vitamin B-deficient diet and a refined semisynthetic complete vitamin diet. 3. The nerve conduction velocity tended to decrease by treatment with acrylamide. The decrement of nerve conduction velocity was partially inhibited by vitamin B complex. No significant difference was found in the groups treated with acrylamide and given vitamin B complex prophylactic-therapeutically and the control (no acrylamide treatment) in the group maintained on a refined semisynthetic vitamin B-deficient diet. 4. The greatest neurite outgrowth was found in the group treated with vitamins B1, B6 and B12-enriched medium, followed by the group of vitamin B12-enriched and vitamin B1-enriched media. All groups treated with a vitamin B-enriched medium had significantly greater (P < 0.01) outgrowth than the controls.

Correlation among geometric, densitometric, and mechanical properties in mandible and femur of osteoporotic rats

We have previously demonstrated bone loss of the mandible and femur in experimental osteoporotic rats and its prevention by medication, using peripheral quantitative computed tomography (pQCT). In the present study, the mechanical properties of the mandible and femur and the correlation to their geometric and densitometric properties were studied in ovariectomized rats with or without etidronate treatment. Fifty-four Wistar strain SPF female rats, 26 weeks old, were randomly assigned to four groups: (1) Basal group (12 rats, 1.0% Ca diet); (2) Sham group (Sham-operated, 12 rats, 0.1% Ca diet); (3) OVX group (ovariectomized, 15 rats, 0.1% Ca diet); (4) Treated group (OVX + etidronate, 15 rats, 0.1% Ca diet). Total bone mineral density (BMD), cortical BMD, cross-sectional cortical bone area, cross-sectional cortical bone thickness, crosssectional moment of inertia (CSMI), and polar strength index (SSI) of the mandible and femur were measured by pQCT. The failure load of mandible and femur was evaluated by three-point bending. The failure load of both bones was significantly lower in the Sham group compared with the Basal group. The OVX group further had a 8% and 7% decrease in the failure load for mandible and femur, respectively, compared to the Sham group. Treatment with etidronate led to an increase in the failure load compared with the OVX group. The failure load was related to the pQCT-assessed variables, especially with cortical bone area and total BMD. Moreover, the geometric and densitometric properties and failure load in the mandible showed a correlation to those in the femur.

Reduction in lipopolysaccharide-induced apoptosis of fibroblasts obtained from a patient with gingival overgrowth during nifedipine-treatment.

OBJECTIVE We have previously demonstrated that the mechanism of nifedipine (NIF)-induced gingival overgrowth is related to the observation that proliferation and cell cycle progression of gingival fibroblasts derived from NIF reactive patient (NIFr) are greater than those from NIF non-reactive patient (NIFn). Gingival overgrowth has also been reported to be a result of inhibited apoptosis of gingival fibroblasts. Apoptosis in fibroblasts is induced by lipopolysaccharide (LPS). Thus, we focused upon evaluating whether there is a difference in LPS-induced apoptosis between NIFn and NIFr. METHODS Both NIFn and NIFr were arrested in DMEM containing 0.5% FBS, stimulated by LPS, and assayed for apoptosis, cell cycle analysis, Western blotting, and caspase activity. RESULTS Compared to NIFn, the number of apoptotic cells was significantly decreased and the percentage of cells in S and G(2)/M phase was significantly increased in NIFr. The levels of Bax and cytochrome c proteins in NIFr were not up-regulated by LPS compared with NIFn. Both NIFn and NIFr displayed the following changes in protein expression: increased Bad, decreased Bcl-xL, and unchanged Bcl-2 and p53. Caspase-3 and -9 activities were significantly increased by LPS in NIFn but were unchanged in NIFr. Caspase-2 activity remained constant whilst caspase-8 activity significantly increased upon LPS treatment in both NIFn and NIFr. CONCLUSION Bad, Bax, cytochrome c, p53, and caspases-2, -3, -8, and -9 are pro-apoptotic proteins. Bcl-2 and Bcl-xL are anti-apoptotic proteins. Thus, the mechanism of NIF-induced gingival overgrowth might be related to decreased apoptosis in NIFr through a reduction of Bax, cytochrome c, and caspase-3 and -9.

Possible pharmacotherapy for nifedipine‐induced gingival overgrowth: 18α‐glycyrrhetinic acid inhibits human gingival fibroblast growth

This investigation aimed to establish the basis of a pharmacotherapy for nifedipine‐induced gingival overgrowth. Gingival overgrowth has been attributed to the enhanced growth of gingival fibroblasts. In this study, we investigated the effects of 18‐α‐glycyrrhetinic acid (18α‐GA) on growth, the cell cycle, and apoptosis and on the regulators of these processes in gingival fibroblasts isolated from patients who presented with nifedipine‐induced gingival overgrowth.

Inhibition of G1 cell cycle arrest in human gingival fibroblasts exposed to phenytoin

Gingival overgrowth is caused in response to the antiepileptic drug phenytoin (PHT). PHT‐induced gingival overgrowth is characterized by the proliferation of fibroblasts and increased collagen formation in gingiva. Fibroblast proliferation is regulated through the cell cycle. Thus, in the present study, we examined the effects of PHT on the cell cycle, the expression of cell cycle control proteins and the proliferation in human gingival fibroblasts (hGFs). Cells were stimulated in serum‐free DMEM with or without 0.25 μm PHT. Subsequently, the cell cycle phase distribution and the protein expression after 24 h and the cell proliferation after 24, 48 and 72 h were evaluated. PHT significantly inhibited synchronization at the G0/G1 phase of the cell cycle in hGFs through serum starvation. Stimulation with PHT for 48 and 72 h significantly induced a proliferative response in hGFs. PHT decreased the expression of the Cdk‐inhibitory proteins p21 and p27 and increased the levels of the S phase‐promoting proteins phospho‐Thr160‐Cdk2 and phospho‐Ser807/811‐Rb in serum‐free DMEM. The inhibition of G1 cell cycle arrest in hGFs may result from an increase in phosphorylated Cdk2 and Rb proteins and decreased levels of p21 and p27 proteins by PHT. The gingival overgrowth may be caused by the failure of the G1 cell cycle arrest in GFs exposed to PHT.