Consideration of hormonal changes for orthodontic treatment during pregnancy and lactation - a review

Hormonal changes in pregnant and lactating women significantly affect bone metabolism and overall stress levels, positioning them as a unique group within the orthodontic population. Fluctuations in estrogen, progesterone, prolactin, and other hormones are closely linked to bone remodeling and the periodontal tissue's response to inflammation caused by dental plaque. Hormones such as thyrotropin, leptin, and melatonin also play crucial roles in pregnancy and bone remodeling, with potential implications for orthodontic tooth movement. Additionally, adverse personal behaviors and changes in dietary habits worsen periodontal conditions and complicate periodontal maintenance during orthodontic treatment. Notably, applying orthodontic force during pregnancy and lactation may trigger stress responses in the endocrine system, altering hormone levels. However, these changes do not appear to adversely affect the mother or fetus. This review comprehensively examines the interaction between hormone levels and orthodontic tooth movement in pregnant and lactating women, offering insights to guide clinical practice.

Estrogen Signaling Dictates Musculoskeletal Stem Cell Behavior: Sex Differences in Tissue Repair

Sexual dimorphisms in humans and other species exist in visually evident features such as body size and less apparent characteristics, including disease prevalence. Current research is adding to a growing understanding of sex differences in stem cell function and response to external stimuli, including sex hormones such as estrogens. These differences are proving significant and directly impact both the understanding of stem cell processes in tissue repair and the clinical implementation of stem cell therapies. Adult stem cells of the musculoskeletal system, including those used for development and repair of muscle, bone, cartilage, fibrocartilage, ligaments, and tendons, are no exception. Both in vitro and in vivo studies have found differences in stem cell number, proliferative and differentiation capabilities, and response to estrogen treatment between males and females of many species. Maintaining the stemness and reducing senescence of adult stem cells is an important topic with implications in regenerative therapy and aging. As such, this review discusses the effect of estrogens on musculoskeletal system stem cell response in multiple species and highlights the research gaps that still need to be addressed. The following evidence from investigations of sex-related phenotypes in adult progenitor and stem cells are pieces to the big puzzle of sex-related effects on aging and disease and critical information for both fundamental tissue repair and regeneration studies and safe and effective clinical use of stem cells. Impact Statement This review summarizes current knowledge of sex differences in and the effects of estrogen treatment on musculoskeletal stem cells in the context of tissue engineering. Specifically, it highlights the impact of sex on musculoskeletal stem cell function and ability to regenerate tissue. Furthermore, it discusses the varying effects of estrogen on stem cell properties, including proliferation and differentiation, important to tissue engineering. This review aims to highlight the potential impact of estrogens and the importance of performing sex comparative studies in the field of tissue engineering.

Inhibition of circular RNA circ_0138959 alleviates pyroptosis of human gingival fibroblasts via the microRNA-527/caspase-5 axis

Circular RNA (circRNA) plays a regulatory role in periodontitis. This study explored whether circ_0138959 affected lipopolysaccharide (LPS)-induced pyroptosis in human gingival fibroblasts (HGFs). The periodontal ligament (PDL) tissues and HGFs were derived from patients with periodontitis and healthy volunteers. HGFs treated with LPS were considered to mimic periodontitis in vitro. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to evaluate the mRNA expression levels of circRNAs, miR-527, and caspase-5 (CASP5), and Western blotting assay was used to measure protein expression levels of caspase-1, caspase-4, and cleaved N-terminal gasdermin D (GSDMD-N). Cell viability was evaluated by cell counting kit-8 (CCK-8) assay. The concentration of lactate dehydrogenase (LDH), interleukin (IL)-1β, and IL-18 and the pyroptosis rate were determined to evaluate pyroptosis. The interaction between miR-527 and circ_0138959 or CASP5 was verified by dual-luciferase reporter and RNA pull-down assays. Circ_0138959 expression was higher in the PDL tissues of patients with periodontitis than in the healthy group; likewise, circ_0138959 was also upregulated in LPS-treated HGFs. Suppressed circ_0138959 increased cell viability and decreased pyroptosis of HGFs induced by LPS. miR-527 was a target of circ_0138959, and inhibition of miR-527 contributed to the dysfunction of LPS-treated HGFs and reversed the protective effects of downregulated circ_0138959. Additionally, miR-527 targeted CASP5. Increased CASP5 abrogated the effects of overexpressed miR-527 on cell viability and pyroptosis of LPS-treated HGFs. Inhibition of circ_0138959 promoted cell viability and suppressed pyroptosis of HGFs via the miR-527/CASP5 axis. Therefore, knockdown of circ_0138959 may be a promising therapy for periodontitis.

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.

PELP1 promotes the expression of RUNX2 via the ERK pathway during the osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVE

The aim of this study was to determine the physiological function and mechanism of proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) in the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) at the molecular level in vitro.

DESIGN

During the osteogenic differentiation of hPDLSCs, the change of PELP1 and the osteogenic commitment markers runt-related transcription factor 2(RUNX2), alkaline phosphatase (ALP) and osteocalcin (OCN) were monitored by quantitative real-time PCR (qRT-PCR) and western blots. To elucidate how PELP1 regulates RUNX2, the expression of RUNX2, the phosphorylation of extracellular regulated protein kinases (ERK) and subcellular location of PELP1 were detected under conditions that PELP1 was either knockdown by specific siRNA or overexpressed. A pharmacological inhibitor of ERK, U0126 was used while PELP1 was overexpressed, and the expression of RUNX2 was monitored by qRT-PCR.

RESULTS

PELP1 was upregulated during the osteogenic differentiation of hPDLSCs. Knockdown of PELP1 suppressed the expression of RUNX2, whereas overexpression of PELP1 increased RUNX2 expression. Moreover, PELP1 knockdown resulted in reduced ERK phosphorylation and RUNX2 expression, and PELP1 overexpression induced RUNX2 expression was inhibited by U0126 in the hPDLSCs.

CONCLUSIONS

PELP1 regulates the expression of RUNX2 during the osteogenic differentiation of hPDLSCs and that the ERK pathway is involved in this process.

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.

Plants and Their Bioactive Constituents in Mesenchymal Stem Cell-Based Periodontal Regeneration: A Novel Prospective

Periodontitis is a common chronic inflammatory disease, which causes the destruction of both the soft and mineralized tissues. However, current treatments such as bone graft materials, barrier membranes, and protein products all have difficulties in regenerating the complete periodontal tissue structure. Stem cell-based tissue engineering has now emerged as one of the most effective treatments for the patients suffering from periodontal diseases. Plants not only can be substrates for life processes, but also contain hormones or functional molecules. Numbers of preclinical studies have revealed that products from plant can be successfully applied in modulating proliferation and differentiation of human mesenchymal stem cells. Plant-derived substances can induce stem cells osteogenic differentiation, and they also possess angiogenic potency. Furthermore, in the field of tissue engineering, plant-derived compounds or plant extracts can be incorporated with biomaterials or utilized as biomaterials for cell transplantation. So it is speculated that botanical products may become a new perspective in stem cell-based periodontal regeneration. However, the lack of achieving predict clinical efficacy and quality control has been the major impediment to its extensive application. This review gives an overview of the prospect of applying different plant-derived substances in various human mesenchymal stem cells-based periodontal regeneration.

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.

17β-estradiol regulates the differentiation of cementoblasts via Notch signaling cascade

Estrogen has been well recognized as a key factor in the homeostasis of bone and periodontal tissue, but the way it regulates the activities of cementoblasts, the cell population maintaining cementum has not been fully understood. In this study, we examined the expression of estrogen receptor in OCCM-30 cells and the effect of 17β-estradiol (E2) on the proliferation and differentiation of OCCM-30 cells. We found that both estrogen receptor α and β were expressed in OCCM-30 cells. E2 exerted no significant influence on the proliferation of OCCM-30 cells, but inhibited the transcription and translation of BSP and Runx2 in the early phase of osteogenic induction except the BSP mRNA. Afterwards in the late phase of osteogenic induction, E2 enhanced the transcription and translation of BSP and Runx2 and promoted the calcium deposition. In addition, the expression level of Notch1, NICD and Hey1 mRNAs responded to exogenous E2 in a pattern similar to that of the osteoblastic markers. DAPT could attenuate the effect of E2 on the expression of osteoblastic markers. These findings indicated that E2 might regulate the differentiation of cementoblasts via Notch signaling.

Crucial role of Notch signaling in osteogenic differentiation of periodontal ligament stem cells in osteoporotic rats

Estrogen deficiency-induced osteoporosis typically occurs in postmenopausal women and has been strongly associated with periodontal diseases. Periodontal ligament stem cells (PDLSCs) isolated from the periodontal ligament can differentiate into many types of specialized cells, including osteoblast-like cells that contribute to periodontal tissue repair. The Notch signaling pathway is highly conserved and associated with self-renewal potential and cell-fate determination. Recently, several studies have focused on the relationship between Notch signaling and osteogenic differentiation. However, the precise mechanisms underlying this relationship are largely unknown. We have successfully isolated PDLSCs from both ovariectomized (OVX) and sham-operated rats. Both the mRNA and protein levels of Notch1 and Jagged1 were upregulated when PDLSCs were cultured in osteogenic induction media. Mineralization assays showed decreased calcium deposits in OVX-PDLSCs treated with a γ-secretase inhibitor compared with control cells. Thus Notch signaling is important in maintaining the osteogenic differentiation of PDLSCs in osteoporotic rats, which help in the development of a potential therapeutic strategy for periodontal disease in postmenopausal women.

Genome-wide association study of periodontal health measured by probing depth in adults ages 18-49 years

The etiology of chronic periodontitis clearly includes a heritable component. Our purpose was to perform a small exploratory genome-wide association study in adults ages 18–49 years to nominate genes associated with periodontal disease−related phenotypes for future consideration. Full-mouth periodontal pocket depth probing was performed on participants (N = 673), with affected status defined as two or more sextants with probing depths of 5.5 mm or greater. Two variations of this phenotype that differed in how missing teeth were treated were used in analysis. More than 1.2 million genetic markers across the genome were genotyped or imputed and tested for genetic association. We identified ten suggestive loci (p-value ≤ 1E-5), including genes/loci that have been previously implicated in chronic periodontitis: LAMA2, HAS2, CDH2, ESR1, and the genomic region on chromosome 14q21-22 between SOS2 and NIN. Moreover, we nominated novel loci not previously implicated in chronic periodontitis or related pathways, including the regions 3p22 near OSBPL10 (a lipid receptor implicated in hyperlipidemia), 4p15 near HSP90AB2P (a heat shock pseudogene), 11p15 near GVINP1 (a GTPase pseudogene), 14q31 near SEL1L (an intracellular transporter), and 18q12 in FHOD3 (an actin cytoskeleton regulator). Replication of these results in additional samples is needed. This is one of the first research efforts to identify genetic polymorphisms associated with chronic periodontitis-related phenotypes by the genome-wide association study approach. Though small, efforts such this are needed in order to nominate novel genes and generate new hypotheses for exploration and testing in future studies.

20-Hydroxyecdysone-induced bone morphogenetic protein-2-dependent osteogenic differentiation through the ERK pathway in human periodontal ligament stem cells

20-Hydroxyecdysone, an ecdysteroid hormone, can induce osteogenic differentiation in mesenchymal stem cells. Periodontal ligament stem cells (PDLS cells) have mesenchymal-stem-cell-like qualities and are considered as one of the candidates of future clinical application in periodontitis treatment. However, there are no studies describing the effect of 20-Hydroxyecdysone on PDLS cells. In this paper, we report a detailed study on the effect of 20-Hydroxyecdysone on PDLS cell proliferation in vitro. PDLS cells were developed from human PDL cells and were treated with 20-Hydroxyecdysone to understand different aspects of its effects. 20-Hydroxyecdysone promoted PDLS cell proliferation; significantly increased the gene expression levels of runt-related transcription factor 2, alkaline phosphatase (ALP), type I collagen, and osteocalcin. Moreover, 20-Hydroxyecdysone enhanced bone formation by PDLS cells and significantly increased bone morphogenetic protein-2 (BMP-2) mRNA and protein expression. However, 20-Hydroxyecdysonemediated increase in ALP activity was blocked with a BMP-2-specific neutralizing antibody or with the antagonist noggin; and20-Hydroxyecdysone mediated induction of BMP-2 expression and increase of ALP activity were abolished by the extracellular regulated protein kinase (ERK) MAPK pathway inhibitor PD98059. 20-Hydroxyecdysone also increased the phosphorylation of ERK. These findings provide evidence to state that 20-Hydroxyecdysone stimulates cell proliferation and induces osteogenic differentiation through the induction of BMP-2 expression in PDLS cells. It also shows that the ERK pathway is involved in 20-Hydroxyecdysone induced BMP-2 expression and osteogenic differentiation. These results are suggesting its potential as a drug for periodontal regenerative therapy.

Estrogen-related receptor α is involved in the osteogenic differentiation of mesenchymal stem cells isolated from human periodontal ligaments

Recently, it has been reported that the orphan nuclear receptor estrogen-related receptor α (ERRα) is involved in the osteogenic differentiation of mesenchymal stem cells (MSCs). Moreover, ERRα has been identified as a novel therapeutic target for treating osteoporosis and other bone diseases. Human periodontal ligament tissue-derived mesenchymal stem cells (hPDLSCs) have recently been used in stem cell-mediated therapies because of their multipotency, particularly toward osteogenic differentiation. However, it is still unclear whether ERRα can regulate the osteogenic differentiation of hPDLSCs. In the present study, we investigated the role of ERRα in the osteogenic differentiation of hPDLSCs in vitro. We isolated hPDLSCs and confirmed their capacity for multipotent differentiation. Furthermore, we examined ERRα expression in hPDLSCs by RT-PCR and immunocytochemistry. We found that the expression of ERRα mRNA was significantly increased during the late stage of osteogenic differentiation of hPDLSCs. Moreover, transfection of recombinant lentiviral-mediated miRNA targeting ERRα significantly suppressed ALP activity, mineralization capacity, and the mRNA expression of osteogenesis-related genes (ALP, OCN, RUNX2 and OPN) in hPDLSCs. Our results indicate that ERRα may promote the osteogenic differentiation of hPDLSCs in vitro.