• Journal of Periodontal and Implant Science
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• v.34 no.2
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• pp.367-375
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• 2004

As the periodontal ligament cells show similar phenotype with osteoblasts, periodontal ligament cells are thought to play an important role in alveolar bone remodeling. According to recent studies, receptor activation of nuclear factor $^{\kappa}B$ ligand (RANKL) and osteoprotegerin (OPG) are expressed in periodontal ligament cells during tooth movement. Also periodontal ligament cells is known to play an important role in the progression of periodontal disease. This study was designed how the expression of RANKL and OPG in periodontal ligament cells was regulated by IL-1 ${\beta}in$ the concentration of $0.01{\sim}10$ ng/ml. The results are as follows; 1. Periodontal ligament cells which stimulated by 1L-1 ${\beta}$ increased soluble RANKL synthesis by dose-dependent pattern in the concentration of $0.01{\sim}10$ ng/ml. 2. 1L-1 ${\beta}$ induced mRANKL expression in dose-dependent manner in the concentration of $0.01{\sim}5$ ng/ml. 3. mOPG expression was not to be influenced by 1L-1 ${\beta}$. These results suggested that rat periodontal ligament cells could regulate osteoclastogenesis by stimulation of production of RANKL.

• Journal of Periodontal and Implant Science
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• v.35 no.3
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• pp.747-760
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• 2005

Periodontal therapy has dealt primarily with attempts at arresting progression of disease. however, more recent techniques have focused on regenerating the periodontal ligament having the capacity to regenerate the periodontium. Recombinant human bone morphogenetic protein-7(rhBMP-7) can differentiate the osteoprogenitor cells and induce bone formation. The purpose of this study was to evaluate the effect of BMP-7 on rat periodontal ligament cells differentiation, in vitro. In the control group, cells was cultured with DMEM media. In the experimental groups, cells were cultured with rhBMP-7 in concentration of 10, 25, 50 and 100 ng/ml. Each group was characterized by examining alkaline phosphatase activity at 3 and 5 days of culture and the ability to produce mineralized nodules of rat calvarial cells at 14 days of culture. Synthesis of type I collagen(COL-I), osteocalcin(OCN), and bone sialoprotein(BSP) was evaluated by RT-PCR at 7 days of culture. Activation of Smad proteins and p38 MAP kinase was determined by western blot analysis of the cell lysates. Alkaline phosphatase activity was significantly increased in the concentration of BMP-7 50 ng/ml and 100 ng/ml compared to the control(p<0.05). The mineralized bone nodule formation was greater with addition of 50 ng/ml and 100 ng/ml BMP-7 than the control(p<0.01). In 7 days' culture, the expressions of COL-I, BSP, and OCN was increased by BMP-7 in concentration of 10 $ng/ml{\sim}100$ ng/ml. In western blot analysis, BMP-7 treated culture cells expressed Smad 1,5,8 in dose-dependent manner, whereas BMP-7 did not activate phosphorylated form of p38 MAP kinase. These result suggested that BMP-7 stimulate rat periodontal ligament cells to differentiate toward osteoblast phenotype and increase bone matrix production by activation of BMP-Smad pathway.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.335-344
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• 2006

Osteoblast or bone marrow stromal cell-derived RANKL is the major effector molecule essential for osteoclastogenesis. Previous studies have shown that tetracyclines have beneficial therapeutic effects in the prevention and treatment of inflammatory bone disease including periodontal disease. Periodontal ligament cells are thought not only to play an important role in the progression of periodontal disease, but to play an important role in alveolar bone remodeling. Previous studies indicated that receptor activation of nuclear factor $\kappa\;B$ ligand (RANKL) and osteoprotegerin (OPG) are expressed in periodontal ligament cells by pro-inflammatory cytokine, such as $IL-1{\beta}$ and $TNF-{\alpha}$. This study was designed to investigate the inhibitory effect of doxycycline on RANKL and OPG mRNA in rat periodontal ligament cells induced by $IL-1{\beta}$ (1 ng/ml). The results are as follows; 1. MTT assay showed that doxycycline at the concentration of $1-50\;{\mu}g/m{\ell}$ didn't result in statistically significant cell death at day 1 and 3. 2. RANKL mRNA expression was increased to 2.6 folds by $IL-1{\beta}$. When cells were treated with doxycycline ($50{\mu}g/m{\ell}$), $IL-1{\beta}$ -induced mRANKL expression was reduced by 33%. In contrast to RANKL, OPG mRNA expression was not inhibited by pre-treatment with doxycycline. These results suggest that doxycycline decrease the expression of mRANKL resulting in regulation of osteoclastogenesisp in rat periodontal ligament cells.

• Journal of Periodontal and Implant Science
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• v.35 no.2
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• pp.289-298
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• 2005

Bone morphogenetic protein-7(BMP-7), a member of the transforming growth factor superfamily, stimulates osteoblast differentiation and bone formation. There are lots of evidences supporting a direct participation of periodontal ligament(PDL) cells on periodontal tissue regeneration. The purpose of this study was to evaluate the effect of recombinant human(rh) BMP-7 on primary rat PDL cells in vitro, with special focus on the ability of bone formation. The PDL cells were cultured with rhBMP-7 at the concentration of 0, 10, 25, 50, 100 and 200ng/ml for MTT assay. We evaluated the alkaline phosphatase activity at 3 and 5 days of incubation and the ability to produce mineralized nodules of rat PDL cells at 14 days of cell culture in concentration of 0, 10, 25, 50 and 100ng/ml. The cell activity was not reduced in cells treated with BMP-7 at $10{\sim}100ng/ml$, whereas the cell activity was reduced in the concentration of 200ng/ml than the control at day 1 and 3(p<0.01). At 3 and 5 day, alkaline phosphatase activity was significantly increased in cells treated with BMP-7 at 50ng/ml and 100ng/ml(p<0.05). The area of mineralized bone nodule was greater in cells treated with BMP-7 at 50 and 100 ng/ml than the control(p<0.01). These results suggest that rhBMP-7 stimulate rat PDL cells to differentiate toward osteoblast phenotype and secretion of the extracellular matrix of rat PDL cells.

• Journal of Periodontal and Implant Science
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• v.27 no.4
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• pp.923-939
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• 1997

This study was performed to evaluate the effect of mixed culture of rat's calvaria cells and periodontal ligament cells on calcification. These cells have been known to do important role on the periodontal tissue regeneration, especially alveolar bone and cementum. Experimental groups were made which based on the different rate of rat's calvaria cells and periodontal ligament cells, and then these cells were cultured with Dulbecco's Modified Eagle's Medium contained with 10% fetal bovine serum, $50{\mu}g/ml$ ascorbic acid, and 10mM/ ml $Na-{\beta}-glycerophosphate$. Each group was characterized by examining the cell proliferation rate, amount of total protein synthesis, alkaline phosphatase activity, and the number of calcified nodules in vitro. In cell proliferation rate , the cells of control groups were cultured Dulbecco's Modified Eagle's Medium contained with 10 % fetal bovine serum. The results were as follows : 1. The cell proliferation rate in control groups decreased stastically significantly along with the decrease of the rate of bone cells at 7 day and 20 day(P < 0.01). 2. The cell proliferation rate in experimental groups decreased stastically significantly along with decrease of the rate of bone cells at 3 day and 14 day(P < 0.01). 3. The amount of total protein synthesis was significantly decreased along with decrease of the rate of bone cells at 3 day and 6 day(p < 0.01). 4. Alkaline phosphatase activity showed reverse time dependent pattern and was significantly decreased along with decrease of the rate of bone cells during the experimental periods (P < 0.01). 5. Calcified nodules were observed in group 1 (Rat calvaria cells alone) for the first time, and the number of calcified nodule decreased stastically significantly along with the decrease of the rate of bone cells at 12 day(P < 0.01). From the above results, When bone cells and periodontal ligament cells were mixed cultured, the cell proliferation rate was mostly dependent on the actual rate of bone cells and same pattern was showed in amount of total protein synthesis, alkalinephosphatase activity, and the number of calcified nodules. And the calcified nodule forming capacity of bone cells was inhibited by periodontal ligament cells

• Journal of Periodontal and Implant Science
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• v.28 no.1
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• pp.17-35
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• 1998

Chitosan, with a chemical structure similar to hyaluronic acid, has been implicated as a wound healing agent. The purpose of this research was to evaluate the effects of chitosan on the characteristics of periodontal ligament cells, calvaria cells and gingival fibroblasts and to define the effects of chitosan on bone formation in vitro. In control group, the cells were cultured alone with Dulbecco's Modified Eagle's Medium contained with 10% Fetal bovine serum, 100unit/ml penicillin, $100{\mu}g/ml$ streptomycin, $0.5{\mu}g/ml$ amphotericin-B. In experimental group, chitosan($40{\mu}g/ml$) is added into the above culture condition. And then each group was characterized by examining the cell proliferation at 1,3,5,7,9,12,15 day, the amount of total protein synthesis, alkaline phosphatase activity at 3, 7 day and the ability to produce mineralized nodules of rat calvaria cell at 11 day. The results were as follows : 1. At early time both periodontal ligament cells and calvaria cells in chitosan-treated group proliferated more rapidly than in non-treated control group, but chitosan-treated group of periodontal ligament cells at 9 days and calvaria cells at 12days showed lower growth rate than control group. Gingival fibroblast in chitosan-treated group had lower growth rate than in control group but the difference was not statistically significant (P< 0.01).2. Both periodontal ligament cells and calvaria cells in chitosan-treated group showed much protein synthesis than in control group at 3 days, but showed fewer than in control group at 7 days. Amount of total protein synthesis of gingival fibroblast didn't have statistically significant difference among the two groups(P< 0.01). 3. At 3 and 7 days, alkaline phosphatase activity of periodontal ligament cells and calvaria cells was increased in chitosan-treated group, but at 7 days there was not statistically significant difference among the two groups of calvaria cells (P< 0.01). Alkaline phosphatase activity of gingival fibroblast didn't have statistically significant difference among the two groups(P<0.01). 4. Mineralized nodules in chitosan-treated group of rat calvaria cells were more than in control group. In summery, chitosan had an effect on the proliferation, protein systhesis, alkaline phosphatase activity of periodontal ligament cells and calvaria cells, and facilitated the formation of bone. It is thought that these effects can be used clinically in periodontal regeneration therapy.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.489-498
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• 2004

Recent studies have demonstrated that human periodontal ligament cells express receptor activation of nuclear factor ${\kappa}B$ ligand (RANKL) which enhances the bone resorbing activity of osteoclasts differentiated from hematopoietic preosteoclasts. The purpose of this study is to determine the effects of p38 MAPK and JNK kinase upon regulating RANKL and OPG in response to $IL-1{\beta}$(l ng/ml) in rat periodontal ligament cells. Soluble RANKL was measured by immunoassay. The effects of p38 MAPK on RANKL and OPG expression was determined by RT-PCR. The results were as follows: 1. Periodontal ligament cells which stimulated by $IL-1{\beta}$ increased soluble RANKL synthesis by dose-dependent pattern. 2. p38 MAP kinase inhibitor (SB203580) showed regulation of soluble RANKL expression by dose-dependent manners. 3. p38 MAP kinase inhibitor (SB203580) regulated the expression of RANKL, but it dose regulate the expresseion of OPG. 4. JNK (c-jun $NH_2-terminal$ kinase) inhibitor (PD98059) did not regulate mRANKL and mOPG. These results suggested that p38 MAPK play a significant role in RANKL gene expression.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.859-872
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• 1996

The purpose of this study was to evaluate the effect of low concentrative ${\beta}-APN$ on the periodontal ligament and relationship between lathyrintic bodies and osteoclast cells near the by alveolar bone. Mandibles including teeth and periodontiums of 24 Sprague-Dawley rat was used. ${\beta}-APN$ 0.2g/kg/day soluted in mineral water was administrated for 5 days before sacrifice in experimental group. 3 rats on each day was sacrificed on 1, 3, 7, 11 days after stop administration ${\beta}-APN$. Histologic examination and the activity of osteoclasts by tartrate resistant acid phosphatase was observed. The results were as follows : 1. In experimental group, the The small foci of lathyrintic bodies surrounded by palisading fibroblasts were seen obviously on 1, 3 days and decreased after 7 days. On 11 days, fibroblasts of periodontal ligament similar to control group. 2. The lathyrintic bodies were seen in the middle zone of periodontal ligament of pressured area like furcation area, alveolar crest, bone resorption area than tensioned area of apposition area. 3. In experimental group of 1, 3 days, lathyrintic bodies were much seen in the area that osteoclasts was much distributed area. After 7 days, experimental group was seen the control group. In conclusion, rathyrintic bodies were formed by low concentrative ${\beta}-APN$ chiefly on the pressured area like furcation area, alveolar crest, bone resorption area than tensioned area of apposition side in periodontal tissue and concerned with osteoclast cells.

• Journal of Periodontal and Implant Science
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• v.28 no.3
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• pp.475-489
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• 1998

The main goal for the treatment of periodontal diseases is the regeneration of lost cementum, bone and connective tissue. Clinical and histological research suggests that it is possible to restore periodontal structures. Seeds of Carthamus tinctorius L. has been used for the treatment of bone fracture and osteoporosis in traditional Korean medicine. The purpose of this study is to examine the effect of extract of seeds of Carthamus tinctorius L. on mineralization in periodontal ligament cells and osteoblastic cells. Periodontal ligament cells were primarily obtained from a extracted premolars with non-periodontal diseases, Osteoblastic cells were obtained from calvariae of a fetal rat, Cells were cultured with DMEM at $37^{\circ}C$ with 5% $CO_2$ in 100% humidity incubator. Alkaline phosphatase(ALP) level and the number of calcification nodules were examined and western blot analysis using osteonectin was performed, Measurements of ALP levels and calcification nodules showed that extract of seeds of Carthamus tinctorius L. had significantly higher activity than control in all of both cells. In western blot analysis, protein expression of osteonectin indicated that extract of seeds of Carthamus tinctorius L. showed an increased pattern than control in all of both cells. From the above results, it seems that extract of seeds of Carthamus tinctorius L. has excellent effect on mineralization in periodontal ligament cells and osteoblastic cells.

• Imaging Science in Dentistry
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• v.30 no.3
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• pp.159-168
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• 2000

Purpose: To elucidate the effects of the irradiation and calcium-deficient diet on expression of interleukin (IL)-1 during tooth formation of rat molar. Materials and Methods: The pregnant three-week-old Spague-Dawley rats were used for the study. The control group was non-irradiation/normal diet group, and the experimental groups were irradiation/normal diet group and irradiation/calcium-deficient diet group. The abdomen of the rats on the 9th day of pregnancy were irradiated with single dose of 350 cGy, The rat pups were sacrificed on the 14th day after delivery and the maxillae tooth germs were taken. The specimen were prepared to make sections for light microscopy, and some of tissue sections were stained immunohistochemically with anti-IL-l antibody. Results: In the irradiation/normal diet group, dental follicle showed fewer blood vessels, mononuclear cells, and fusions of mononuclear cells than in non-irradiation/normal diet group. Alveolar bone showed a few osteoblasts and osteoclasts. Periodontal ligament showed collagen fibers and fibroblasts with irregularity. Weak immunoreactivity for IL-l was shown in dental follicle, alveolar bone, and periodontal ligament. In the irradiation/calcium-deficient diet group, dental follicle showed sparse cellularity. Alveolar bone showed diminished number of osteoblasts. Periodontal ligament showed irregular collagen fibers and atrophy of cementoblasts and fibroblasts. No immunoreactivity for IL-1 was shown in dental follicle, alveolar bone, and periodontal ligament. Conclusion: Irradiation and calcium-deficient diet seems to cause disturbance of the expression of interleukin-l during tooth formation of rat molar.