Immunocytochemical demonstration of estrogen receptor β in human periodontal ligament cells

Evaluation of tooth eruption rate of incisor teeth in rats with estrogen deficiency

OBJECTIVES

To assess the influence of estrogen deficiency on tooth eruption rate (TER) and gene expression of estrogen receptor alpha and beta (ERα and ERβ) in the odontogenic region of teeth with continuous formation in a rat model.

MATERIALS AND METHODS

Ovariectomies (OVX; n = 25) and sham surgeries (SHAM; n = 25) were performed in female Wistar rats when animals were 25 days old. The TER of the lower incisors, both in impeded (hyperfunction condition) and unimpeded (trimmed incisal edge-hypofunction condition) conditions, was evaluated using standardized digital photographs acquired every 48-72 h for 3 weeks (35th-53rd day of life), using a camera coupled to a stereomicroscope. Quantitative real-time PCR was performed to evaluate the relative gene expression of ERα and ERβ in the odontogenic region.

RESULTS

The OVX group showed a significant reduction in TER when compared to the SHAM group, only in the impeded condition (p = 0.03). There was no statistically significant difference between the groups in ERα gene expression (p = 0.33). ERβ showed a significantly higher gene expression in the OVX group (p ≤ 0.05).

CONCLUSIONS

Estrogen deficiency decreases TER in teeth under impeded condition. Estrogen deficiency also increases ERβ gene expression in the odontogenic region of teeth with continuous formation.

CLINICAL RELEVANCE

Hormonal disturbances affecting estrogen levels can cause alterations in dental formation and teeth eruption.

The Effect of Menopause Hypoestrogenism on Osteogenic Differentiation of Periodontal Ligament Cells (PDLC) and Stem Cells (PDLCs): A Systematic Review

(1) Background: Menopause is a physiological condition typified by drastic hormonal changes, and the effects of this transition have long-term significant clinical implications on the general health, including symptoms or physical changes. In menopausal women, the periodontium can be affected directly or through neural mechanism by oestrogen (E2) deficiency. The majority of the biological effects of E2 are modulated via both oestrogen receptor-α (ERα) and oestrogen receptor- β (ERβ). There is evidence that hypoestrogenism has a substantial impact on the aetiology, manifestation and severity of periodontitis, via the regulation of the expression of osteoprogesterin and RANKL in human periodontal ligament cells through ERβ. However, the mechanistic understanding of oestrogen in periodontal status has been partially clarified. The aim of this paper was to synopsize the recent scientific evidence concerning the link between the menopause and periodontitis, through the investigation of physio-pathological impact of the oestrogen deficiency on osteogenic differentiation of PDLSCs and PDLSC, as well as the dynamic change of ERα and ERβ. (2) Methods: Search was conducted for significant studies by exploring electronic PubMed and EMBASE databases, and it was independently performed by two researchers. All studies on the impact of oestrogen level on alveolar bone resorption were searched from 2005 to July 2020. Data selection was in concordance with PRISMA guidelines. (3) Results: Eight studies met the criteria and were included in this systematic review. All studies reported that oestrogen deficiency impairs the osteogenic and osteoblastic differentiation of PDL cells and oestrogen affects the bone formation capacity of cells. Seven studies were conducted on animal samples, divided into two groups: the OVX animals and animals who received the sham operation. (4) Conclusions: There is a multitude of data available showing the influence of menopause on periodontal status. However, the evidence of this line to investigation needs more research and could help explain the physiological linkage between menopause state and periodontal disease.

Donor variation and sex hormone receptors in periodontal ligament cells

OBJECTIVE

This study evaluated the gene expression and protein synthesis of sex hormone receptors in human periodontal ligament cells (PDLCs) in relation to donor- and tooth-specific factors with the aim to clarify the debate about sex hormone receptors in PDLCs.

DESIGN

The expression patterns of estrogen receptors (genes: ESR1 and ESR2; proteins: ERα and ERβ), androgen receptor (AR) and progesterone receptor (PR) were investigated in the context of immortalization status, previous orthodontic tooth movement (OTM), donor age, sex and hormonal stimulation in PDLCs from 14 healthy donors (male: n = 8, female: n = 6; adolescents: n = 8, adults: n = 6) using quantitative real-time polymerase chain reaction, Western blot and immunocytochemistry.

RESULTS

For ERβ, the full-length isoform ERβ1 and truncated variants were detected. For ERα, the expected isoform ERα66 was not observed, but a novel isoform ERα36 was detected. Immortalization status, previous OTM and donor age had no impact on ESR1 and ESR2 expression. Estradiol stimulation for 24 h doubled the ratio of ESR2/ESR1 in PDLCs from female but not male donors, indicating sex-specific patterns of receptor expression. AR and PR demonstrated insufficient protein synthesis in PDLCs.

CONCLUSIONS

The data revealed a pivotal role for and complex interplay between ERα and ERβ in human PDLCs regardless of variable donor characteristics. Therefore, PDLC biology might be altered in patients of each age group and both sexes due to hormonal changes. This should be kept in mind during periodontic and orthodontic treatment of patients with special hormonal status.

Sociodemographic Differences in Health Awareness and Oral Health in Pregnant Women

Objective The aim of this study was to determine the present oral health status of pregnant women depending on selected sociodemographic differences and deduce any resulting consequences for health prevention.

Methods The participantsʼ data of relevance to the study such as age, school leaving qualification, migration background, smoking habits or last dentist visit were recorded using a questionnaire. The subsequent dental check-up concentrated on open carious lesions, any initiated root canal treatments and missing teeth. Finally, the Periodontal Screening Index was recorded to diagnose the presence of any gingivitis or periodontitis. The subsequent biometric evaluation comprised descriptive data analysis, χ2 test and logistical regression.

Results The higher the school leaving qualification, the lower the probability that a pregnant woman smoked prior to pregnancy (OR 0.291; 95% CI 0.114 – 0.743) and that tartar was diagnosed (OR 0.424; 95% CI 0.185 – 0.973). Regular dentist visits (OR 4.026; 95% CI 1.613 – 10.049) increase with the attained school leaving qualification. There is a greater chance that women born in Germany taking part in the study were aware of dental risks in pregnancy (OR 2.652; 95% CI 1.285 – 5.472) and attended the dentist during pregnancy (OR 2.507; 95% CI 1.281 – 4.907).

Conclusion The rate of awareness of the risks and consequences of pregnancy for oral health must be increased. The main aim for primary prophylaxis should be a reduction in the periodontal bacteria and caries of the mother and father.

Periodontal diseases and adverse pregnancy outcomes: Is there a role for vitamin D?

Studies have shown a relationship between maternal periodontal diseases (PDs) and premature delivery. PDs are commonly encountered oral diseases which cause progressive damage to the periodontal ligament and alveolar bones, leading to loss of teeth and oral disabilities. PDs also adversely affect general health by worsening of cardiovascular and metabolic diseases. Moreover, maternal PDs are thought to be related to increasing the frequency of preterm-birth with low birth weight (PBLBW) in new-borns. Prematurity and immaturity are the leading causes of prenatal and infant mortality and is a major public health problem around the world. Inflamed periodontal tissues generate significantly high levels of proinflammatory cytokines that may have systemic effects on the host mother and the fetus. In addition, the bacteria that cause PDs produce endotoxins which can harm the fetus. Furthermore, studies have shown that microorganisms causing PDs can get access to the bloodstream, invading uterine tissues, to induce PBLBW. Another likely mechanism that connects PDs with adverse pregnancy outcome is maternal vitamin D status. A role of inadequate vitamin D status in the genesis of PDs has been reported. Administration of vitamin D supplementation during pregnancy could reduce the risk of maternal infections and adverse pregnancy outcomes. As maternal PDs are significant risk factors for adverse pregnancy outcome, preventive antenatal care for pregnant women in collaboration with the obstetric and dental professions are required.

Ipriflavone promotes proliferation and osteogenic differentiation of periodontal ligament cells by activating GPR30/PI3K/AKT signaling pathway

Objectives

This study was performed to investigate the effects and mechanism of ipriflavone (IP) on the proliferation and osteoblastic differentiation of periodontal ligament cells in vitro and periodontal tissue remodeling following orthodontic tooth movement (OTM) in vivo.

Materials and methods

Human periodontal ligament cells (hPDLCs) were cultured in vitro and cell counting kit-8, alkaline phosphatase (ALP) activity assay, plate clone formation assay, and alizarin red staining were used to test proliferation and osteogenic differentiation of hPDLCs. What is more, the expression of ALP, Runx2, and GPR30 was examined by real-time polymerase chain reaction and Western blot. To find out if PI3K/AKT signaling pathway was involved in the process, AKT and p-AKT were examined by Western blot. LY294002 (PI3K signaling pathway inhibitor) and small interfering RNA targeting GPR30 mRNA (siGPR30) were used to verify the function of GPR30-mediated PI3K/AKT pathway in this process. Twenty-four male Wistar rats were randomized into 2 groups, the control group with force application and the IP group with force application plus IP. Morphological changes in the periodontal tissue between roots of teeth were investigated using hematoxylin and eosin (HE) staining and bone morphogenetic protein-2 was detected to assess bone remodeling by immunohistochemical staining.

Results

In vitro, 10⁻⁷ M IP was selected significantly promoting proliferation, ALP activity, colony forming efficiency, and mineral deposition (P<0.05) on hPDLCs. Gene expressions of ALP, Runx2, GPR30, and p-AKT were all upregulated than the control group (P<0.05). According to the mechanism, promotion of ALP and Runx2 interdicted by LY294002 and siGPR30 reduced the activation of PI3K/AKT signaling pathway. In addition, HE staining and immunohistochemical staining results showed that the IP group had more new bone formation in the periodontal tissue compared to the control group in vivo.

Conclusion

IP can promote the expression of ALP and Runx2 which was probably related to the GPR30-mediated PI3K/AKT signaling pathway. Moreover, IP coordination seemed to have the potential to prevent relapsing following OTM.

Oestrogen receptor β (ERβ) regulates osteogenic differentiation of human dental pulp cells

Estradiol (E₂) has many important actions in the tissues of the oral cavity. Disruption of E₂ metabolism or alterations in systemic E₂ concentrations have been associated with compromised periodontal health. In many instances such changes occur secondarily to the well characterised effects of E₂ on bone physiology -especially maintenance of bone mineral density (BMD). Despite these important epidemiological findings, little is known about the mechanism of action of E₂ in oral tissues or the expression and function of oestrogen receptor (ER) isoforms in these tissues. We have isolated human dental pulp cells (hDPCs), which are able to differentiate towards an osteogenic lineage under appropriate culture conditions. We show that hDPCs express ERα, ERβ1, ERβ2 and the cell membrane associated G protein-coupled ER (GPR30). Following osteogenic differentiation of hDPCs, ERβ1 and ERβ2 were up regulated approximately 50-fold while ERα and GPR30 were down regulated, but to a much lesser degree (approximately 2-fold). ERβ was characterised as a 59kDa protein following Western blot analysis with validated antibodies and ERβ was detected in both nuclear and cytoplasmic cell compartments following immunofluorescence (IF) and immunohistochemical (IHC) analysis of cultured cells. Furthermore isoform specific antibodies detected both ERβ1 and ERβ2 in DPC cultures and in situ analysis of ERβ expression in decalcified tooth/pulp sections identified the odontoblast layer of pulp cells juxtaposed to the tooth enamel as strongly reactive for both ERβ isoforms. Finally the use of isoform specific agonists identified ERβ as the main receptor responsible for the pro-osteogenic effect of oestrogenic hormones in this tissue. Our data suggest that oestrogens stimulated osteogenic differentiation in hDPCs and that this action is mediated principally through the ERβ isoform. These findings may have important consequences for the investigation and treatment of oral and periodontal pathologies which are associated with imbalances in oestrogen concentrations and action.

Influence of sex steroids on inflammation and bone metabolism

Sex steroids are central to sexual development and reproduction, exerting pleiotropic effects on multiple tissues and organs throughout the lifespan of humans. Sex steroids are fundamental to skeletal development, bone homeostasis and immune function. The composite effect of sex-specific genetic architecture and circulating levels of sex-steroid hormones closely parallels differences in the immune response and may account for corresponding sex-related differences in risk for chronic periodontitis, with men exhibiting greater susceptibility than women. Age-associated reductions in sex steroids also provide insight into apparent temporal increases in susceptibility to periodontitis and alveolar bone loss, particularly among women. Chronic infection and inflammatory conditions, such as periodontal disease, provide a unique platform for exploring the interface of sex steroids, immunity and bone metabolism.

Relationship between gingival inflammation and pregnancy

An increase in the prevalence and severity of gingival inflammation during pregnancy has been reported since the 1960s. Though the etiology is not fully known, it is believed that increasing plasma sex steroid hormone levels during pregnancy have a dramatic effect on the periodontium. Current works of research have shown that estrogen and progesterone increasing during pregnancy are supposed to be responsible for gingivitis progression. This review is focused not only on epidemiological studies, but also on the effects of progesterone and estrogen on the change of subgingival microbiota and immunologic physiological mediators in periodontal tissue (gingiva and periodontal ligament), which provides current information about the effects of pregnancy on gingival inflammation.

Effect of the menstrual cycle on inflammatory cytokines in the periodontium

BACKGROUND AND OBJECTIVE

The effects of different levels of steroid hormones, as experienced during puberty, pregnancy and menopause, on the periodontium have been demonstrated, but changes in sex hormone levels during the menstrual cycle, and the influence of these changes on the periodontium, remain unresolved. The aim of this study was to investigate the effect of the menstrual cycle on the levels of interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) in gingival crevicular fluid and on periodontal clinical parameters, including the gingival bleeding index (GBI) and the modified gingival index (MGI), in periodontally healthy women.

MATERIAL AND METHODS

Twenty-seven periodontally healthy women with a regular menstrual cycle were included in the study. Clinical parameters, including the GBI, the MGI and the simplified oral health index, were recorded during menstruation, ovulation and premenstruation phases (e.g. on days 1-2, 12-14 and 22-24, respectively) of the menstrual cycle. Gingival crevicular fluid and unstimulated saliva were collected, at each study phase, for assessment of IL-1β, TNF-α, estrogen and progesterone.

RESULTS

Both the GBI and the MGI increased significantly during the menstrual cycle, and were significantly higher during ovulation than during menstruation or premenstruation (p < 0.001). No significant change in the simplified oral health index was observed during the menstrual cycle ( p = 0.18). The levels of IL-1β and TNF-α increased during the different phases of the menstrual cycle, but only the change in the TNF-α concentration was significant ( p < 0.05).

CONCLUSION

This study indicated that changes occurring during the menstrual cycle influence the periodontium and induce inflammatory conditions.

Oral contraceptives and the periodontium

Oral contraceptives are a safe and effective means of contraception for millions of women worldwide. The first formulations of these drugs contained much higher doses of estrogens and progestins than those available today, and these were associated with an unacceptably high rate of unwanted effects including serious cardiovascular events. In addition, a number of case reports and clinical studies suggested that use of the first generation oral contraceptives was also associated with an increased risk for gingival and/or periodontal disease. Unfortunately, many of these early studies suffered from significant methodological flaws which throw their findings into question. Nonetheless, these studies provided the basis for a perception among the dental profession that oral contraceptives increase the risk for gingivitis and/or periodontitis. Realisation that the adverse events profile of oral contraceptives was dose dependant led to the development of the modern low dose formulations that are in use today. There have been far fewer studies to investigate whether modern oral contraceptives have any impact on the periodontium compared to studies of the early contraceptive formulations, but the quality of the more recent research is undoubtedly better. Following extensive review of the relevant literature and consideration of the historical perspective, the best available evidence strongly supports that oral contraceptives no longer place users at any increased risk for gingivitis or periodontitis. Oral contraceptives should not be viewed as a risk factor for gingival or periodontal disease.

Differential effects of LPS from Escherichia coli and Porphyromonas gingivalis on IL-6 production in human periodontal ligament cells

OBJECTIVE

Periodontal ligament (PDL) cells produce IL-6 upon stimulation with inflammation promoters, but the signaling pathways involved have not been characterized. This study investigates underlying mechanisms behind regulation of PDL cell IL-6 production by E. coli and P. gingivalis LPS.

MATERIALS AND METHODS

Human PDL cells, endothelial cells and monocytes were stimulated with E. coli or P. gingivalis LPS in the presence or absence of pharmacological agents in order to disclose pathways involved in LPS signaling. Gene expression and cellular protein levels were assessed by quantitative real-time PCR and ELISA, respectively.

RESULTS

Stimulation with LPS from E. coli (1 µg/ml) for 24 h enhanced PDL cell IL-6 expression several fold, demonstrated both on transcript and protein levels, but P. gingivalis LPS (1-5 µg/ml) had no effect. TLR2 mRNA was more highly expressed than TLR4 transcript in PDL cells. Treatment with the non-selective nitric oxide synthase inhibitor L-NAME (100 µM) reduced E. coli LPS-induced PDL cell IL-6 by 30%, while neither aminoguanidine (10 µM), an inhibitor of inducible nitric oxide synthase, nor estrogen (17β-estradiol, 100 nM) influenced IL-6. Treatment with the glucocorticoid dexamethasone (1 µM) totally prevented the E. coli LPS-induced PDL cell IL-6. In endothelial cells, neither E. coli LPS nor P. gingivalis LPS promoted IL-6 production. In monocytes, serving as positive control, both E. coli and P. gingivalis LPS stimulated IL-6.

CONCLUSIONS

E. coli LPS but not P. gingivalis LPS stimulates PDL cell IL-6 production through a glucocorticoid-sensitive mechanism involving nitric oxide formation, probably via endothelial nitric oxide synthase.

Estrogen regulates DNA synthesis in human gingival epithelial cells displaying strong estrogen receptor β immunoreactivity

BACKGROUND AND OBJECTIVE

Estrogen acts via estrogen receptor (ER) α and β. The expression pattern of ERs and their importance in gingival tissues are not fully understood. In this study, we investigate gingival ER expression and effects of estrogen on gingival epithelial cell proliferation.

MATERIAL AND METHODS

Gingival biopsies were obtained from both healthy and diseased sites in three male and three female subjects. Expression of ERα and β was determined by immunohistochemistry. Effects of 17β-estradiol (E(2) ) on cell proliferation, monitored by measuring DNA synthesis, were studied in cultured human gingival epithelial HGEPp.05 cells.

RESULTS

Estrogen receptor β, but not ERα, immunoreactivity was demonstrated in nuclei of epithelial cells in all layers of the gingival epithelium, but also in cells of the lamina propria. No differences were observed between male and female subjects. The same pattern, i.e. high ERβ expression but no ERα expression, was observed in both healthy and diseased sites within each individual. No differences in the intensity of the ERβ immunoreactive signal and the number of ERβ-positive nuclei were observed between healthy and diseased gingiva. Treatment with a physiological concentration of E(2) (10 nm) had no effect on DNA synthesis in ERβ- and ERα-expressing HGEPp.05 cells. In contrast, E(2) at high concentrations (500 nm and 10 μm) reduced DNA synthesis by 60-70%.

CONCLUSION

Human gingival epithelial cells display strong ERβ but low ERα immunoreactivity both in vivo and in culture. Estrogen attenuates gingival epithelial cell DNA synthesis at high but not low concentrations, suggesting a concentration-dependent mechanism.

Oestrogen regulates proliferation, osteoblastic differentiation, collagen synthesis and periostin gene expression in human periodontal ligament cells through oestrogen receptor beta

OBJECTIVE

The present study was designed to examine how oestrogen regulates proliferation, osteoblastic differentiation, collagen synthesis and periostin gene expression in primary human periodontal ligament (hPDL) cells.

DESIGN

The short interfering RNA (siRNA) technique was used to inhibit oestrogen receptor beta (ERβ) expression hPDL cells. hPDL cell were isolated and fully characterized. A colorimetric assay was applied for the determination of alkaline phosphatase (ALP). An ELISA kit was used to detect osteocalcin (OCN) levels. Collagen synthesis was determined by measuring the incorporation of L-[3H] praline. RT-PCR was performed to detection of periostin mRNA relative gene expression.

RESULTS

ERβ mRNA was expressed in hPDL cells and significant inhibition of mRNA expression and ERβ mature protein of the ERβ was evident in the siRNA group. At 72h, there was a significant increase in non-transfected hPDL cell proliferation after estradiol stimulation. Addition of 17β-estradiol significantly enhanced ALP activity and production of OCN in non-transfected cells but had no effect on collagen synthesis. A clear increase in periostin mRNA expression levels was observed after incubating hPDL cells with estradiol. In hPDL-siERβ cells, the application of estradiol did not produce any evident differences in periostin mRNA expression

CONCLUSIONS

ERβ may play important roles in oestrogen-induced effects on hPDL cell proliferation, osteoblastic differentiation and expression of key molecules for the functional and structural integrity of the periodontium (i.e. periostin).

Oestrogen receptors are involved in the osteogenic differentiation of periodontal ligament stem cells

The existence of PDLSCs [PDL (periodontal ligament) stem cells] in PDL has been identified and such cells may function in periodontal reconstruction, including bone formation. Oestrogens/ERs (oestrogen receptors; ERα and ERβ) exert important effects in bone formation, however, the relationship between ERs and PDLSCs has not been established. In the present study, PDLSCs were isolated and assays for detecting stem-cell biomarkers and multipotential differentiation potential confirmed the validity of human PDLSCs. The results of RT–PCR (reverse transcription–PCR) and Western blotting showed that ERα and ERβ were expressed at higher levels in PDLSCs as compared with PDLCs (PDL cells), and 17β-oestradiol obviously induced the osteogenic differentiation of PDLSCs in vitro. Furthermore, a pan-ER inhibitor or lentivirus-mediated siRNA (small interfering RNA) targeting ERα or ERβ blocked the oestrogen-induced osteogenic differentiation of PDLSCs. The results indicate that both ERα and ERβ were involved in the process of osteogenic differentiation of PDLSCs.

Effects of ovariectomy and aging on tooth attachment in female mice assessed by morphometric analysis

OBJECTIVE

Non-human primates, dogs, rats, hamsters and ferrets, have frequently been used as laboratory animals in periodontal biology and pathology. In the past, mice have been used less for this purpose, but nowadays attract a lot of interest because gene knockout and transgenic technologies utilize mice primarily. In this study, we investigate the effects of ovariectomy and aging on tooth attachment in female mice.

MATERIAL AND METHODS

Eight-week-old mice (n=15) were divided into three experimental groups (control, n=5; sham-operated, n=5; ovariectomy, n=5) and ovaries removed bilaterally. Attachment level, assessed by measuring alveolar bone height and apical termination of the junctional epithelium, was determined 6 weeks post-ovariectomy by digital morphometric analysis in sagittal sections of the mandible. The plasma level of the inflammation marker serum amyloid A (SAA) was determined by ELISA. In another series of experiments, tooth attachment was determined in female mice (n=7) at 8-26 weeks of age.

RESULTS

Withdrawal of female sex hormone production by ovariectomy had no effect on alveolar bone height and apical termination of the junctional epithelium. The SAA level in plasma was unaffected by removal of the ovaries, suggesting that systemic inflammation is not induced by ovariectomy. Bone height was similar in mice sacrificed at 8-26 weeks of age and apical termination of the junctional epithelium was at the cemento-enamel junction at all ages.

CONCLUSIONS

Removal of ovarian production of female sex hormones by ovariectomy has no influence on tooth attachment, and further tooth attachment is preserved with age in female mice.

LPS induces GROalpha chemokine production via NF-kappaB in oral fibroblasts

OBJECTIVE AND DESIGN

Chemotaxis of neutrophils from blood to the inflammation process plays an important role in development of periodontal inflammation. The novel chemokine GROalpha, also named CXCL1, is a strong chemoattractant for neutrophils. Data on production and regulation of GROalpha by oral fibroblasts have not previously been presented.

MATERIALS AND METHODS

GROalpha mRNA and protein levels were determined in human periodontal ligament cells and mouse gingival fibroblasts by quantitative real-time PCR and ELISA.

RESULTS

We disclose that both human periodontal ligament cells and mouse gingival fibroblasts produce GROalpha in response to LPS stimulation. Stimulation with LPS for 24 h increased both mRNA for GROalpha and GROalpha protein. The steroid hormone estrogen had no effect on LPS-induced GROalpha mRNA expression. Treatment with the glucocorticoid dexamethasone attenuated LPS-induced GROalpha production, and the NF-kappaB blocker MG 132 fully prevented LPS-induced GROalpha.

CONCLUSIONS

Oral fibroblasts respond to LPS stimulation by increasing GROalpha production via the transcription factor NF-kappaB, suggesting that this mechanism may be involved in development of periodontal inflammation.

Effect of estrogen receptor beta on the osteoblastic differentiation function of human periodontal ligament cells

OBJECTIVE

To investigate the effect of estrogen receptor beta (ERbeta) on osteoblastic differentiation function of human periodontal ligament (hPDL) cells by measuring the alkaline phosphatase (ALP) activity and the production of osteocalcin (OCN) in vitro.

DESIGN

We employed a short interfering RNA (siRNA) technique to inhibit ERbeta expression in hPDL cells; the cells were cultured with a saturating concentration of 17beta-estradiol (10(-7)M). ALP activity was analysed by colorimetric assay using ALP kit and the amount of OCN was assessed by osteocalcin ELISA kit.

RESULTS

It was shown that estradiol significantly enhanced the ALP activity and the production of OCN in hPDL cells. However, the ALP activity and the production of OCN in hPDL-siERbeta cells were not significantly changed after estradiol treatment.

CONCLUSIONS

These results indicate that ERbeta may play important roles in estrogen-induced effects on osteoblastic differentiation function of PDL cells and estrogen influences the bone formation capacity of PDL cells mainly via ERbeta.

Demonstration of mitochondrial oestrogen receptor beta and oestrogen-induced attenuation of cytochrome c oxidase subunit I expression in human periodontal ligament cells

OBJECTIVE

Periodontal ligament (PDL) cells express oestrogen receptor beta (ERbeta) protein, but cellular functions regulated by ERbeta in these cells have not been identified. In this study we determine if ERbeta is localised to mitochondria and if oestrogen regulates mitochondrial function in human PDL cells obtained from teeth extracted for orthodontic reasons.

DESIGN

Subcellular distribution of ERbeta was determined by confocal microscopy of cells co-stained with ERbeta antibody and the mitochondrion-selective probe MitoTracker and by immunogold electron microscopy. Expression of the mitochondrial enzyme cytochrome c oxidase subunit I, involved in oxidative phosphorylation, was determined by Western blotting in cells treated with or without physiological concentrations of the endogenous oestrogen 17beta-oestradiol.

RESULTS

ERbeta immunoreactivity was observed both in the nuclei and the cytoplasm. MitoTracker-labelling was observed in the cytoplasm, especially in the perinuclear region, but not in the nuclei. Co-localisation of ERbeta and MitoTracker was observed in cells derived from both male and female subjects. Mitochondrial localisation of ERbeta was confirmed by immunogold electron microscopy. Cells treated with or without 17beta-oestradiol (100 nM) displayed an identical pattern of staining for mitochondria. Treatment with 100 nM 17beta-oestradiol attenuated cytochrome c oxidase subunit I expression by about 30%, while combined treatment with 17beta-oestradiol and the ER blocker ICI 182780 (10 microM) had no effect.

CONCLUSION

This study demonstrates mitochondrial localisation of ERbeta and oestrogen-induced decrease in the expression of cytochrome c oxidase subunit I in human PDL cells, suggesting that oestrogen probably via ERbeta influences mitochondrial function and PDL cell energy metabolism.

Differential effects of estrogen on DNA synthesis in human periodontal ligament and breast cancer cells

BACKGROUND

It is important to clarify the biological function of the female sex hormones estrogen and progesterone in periodontal ligament cells, as these hormones may affect periodontal health. We have previously shown that human periodontal ligament cells express estrogen receptor beta (ERbeta) but not ERalpha, whereas human breast cancer cells (MCF7) express both ERalpha and ERbeta. Data on progesterone receptor (PgR) expression in human periodontal ligament cells have not been reported.

OBJECTIVES

Determine PgR expression in human periodontal ligament and MCF7 cells and to investigate how estrogen affects DNA and collagen synthesis in these two cell types showing different pattern of expression for ERalpha and beta.

METHODS

Periodontal ligament cells were obtained from the periodontal ligament of premolars extracted for orthodontic reasons and MCF7 cells from the American Type Culture Collection (ATCC). PgR expression was determined by immunocytochemistry. DNA and collagen synthesis was determined by [(3)H]thymidine and L-[(3)H]proline incorporation, respectively.

RESULTS

PgR immunoreactivity was observed in nuclei of MCF7 but not periodontal ligament cells. Treatment with estrogen (17beta-estradiol, E(2)) at physiological concentrations for 24 h stimulated DNA synthesis by more than two times in MCF7 cells, whereas there was no effect on periodontal ligament cell DNA synthesis. The ER blocker ICI 182780 fully reversed the stimulatory effect of E(2). Not only short-term (24 h) but also long-term (5 days) treatment with E(2) lacked effect on DNA synthesis in periodontal ligament cells. Neither periodontal ligament cell viability nor collagen synthesis was affected by E(2) treatment. Identical results were observed in periodontal ligament cells from male and female subjects.

CONCLUSIONS

Human MCF7 but not periodontal ligament cells express PgR, suggesting that progesterone via PgR affects MCF7 but not periodontal ligament cells. Further, estrogen stimulates breast cancer MCF7 cell proliferation, whereas it has no effect on proliferation of periodontal ligament cells, probably reflecting cell type specific ER expression pattern in these two cell types.