Parathyroid hormone modifies human periodontal ligament cell proliferation and survival in vitro

Intermittent parathyroid hormone enhances the healing of medication-related osteonecrosis of the jaw lesions in rice rats

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event in patients treated with antiresorptives. Management of MRONJ is challenging, and no non-antibiotic, established medical treatment exists. Intermittent parathyroid hormone (iPTH) has been used off-label to treat MRONJ with favorable results. However, its medical efficacy has rarely been substantiated in clinical or preclinical experiments. Using a validated rice rat, infection-based model of MRONJ, we evaluated the effects of iPTH on established MRONJ. We hypothesize that iPTH contributes to MRONJ resolution by enhancing alveolar bone turnover and healing oral soft tissues. Eighty-four rice rats began a standard rodent chow diet at age 4 weeks to induce localized periodontitis. Rats were simultaneously randomized to receive saline (vehicle, VEH) or zoledronic acid (ZOL, 80 μg/kg IV) every 4 weeks. Oral exams were conducted bi-weekly to assign a gross quadrant grade (GQG, 0-4) to evaluate any lesion at the lingual aspect of the interdental space between maxillary molar (M2) and M3. 14 of 20 VEH-treated rice rats (70%) developed maxillary localized periodontitis with GQG 2-3 after 30 ± 10 weeks of saline. Additionally, 40 of 64 ZOL-treated rice rats with periodontitis developed MRONJ-like lesions after 30 ± 10 weeks of ZOL treatment. Rice rats with localized periodontitis or MRONJ-like lesions were treated with saline or iPTH (40 μg/kg) subcutaneously (SC) 3 times/week For 6 weeks until euthanasia. We found that iPTH -treated ZOL rats had a lower prevalence of MRONJ (p < 0.001), with lower severity extent of oral lesions (p = 0.003) and percentage of empty osteocyte lacunae (p < 0.001). ZOL rats treated with iPTH displayed a higher osteoblast surface (p < 0.001), more osteoblasts (p < 0.001), higher osteoclast surface (p < 0.001) and more osteoclasts (p = 0.002) at alveolar bone surfaces than ZOL/VEH rats. Greater gingival epithelial thickness and epithelial cell proliferation rate was found in the oral mucosa and gingiva of ZOL/PTH rats than in ZOL/VEH rats (p < 0.001). Our data suggest that iPTH is an efficacious non-operative medicinal therapy that accelerates oral healing and enhances the resolution of MRONJ lesions in ZOL-treated rice rats.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Influence of Intermittent Parathyroid Hormone (PTH) Administration on the Outcomes of Orthodontic Tooth Movement—A Systematic Review

Objective: The aim of this review is to summarize the effects of local and systemic PTH administration on periodontal tissues during orthodontic tooth movement. Materials and methods: An electronic search was conducted on the following databases: PubMed/MEDLINE, Google Scholar, SCOPUS and Embase. On PubMed/MEDLINE, the Medical Subject Headings (MeSH) keywords used were: “orthodontic tooth movement” OR (“tooth” (All Fields) AND “tooth movement” (All Fields)) OR “tooth movement” (All Fields)) AND (“parathyroid hormone”); all studies included using CONSORT. Results: After elimination of duplicates and articles not meeting our inclusion criteria, seven animal studies were included in this review. Although the majority of the studies suggest that PTH may a have a favorable outcome on OTM, most studies were found to have several sources of bias. Conclusion: Animal studies with minimal bias and long-term clinical studies are needed to ascertain the efficacy of intermittent PTH administration in improving the rate and retention of OTM.

The Effects of Continual Intermittent Parathyroid Hormone Treatment on Human Periodontal Ligament Fibroblasts in an In Vitro Wound Repopulation Model

INTRODUCTION

Periodontal ligament fibroblasts (PDLFs) play a vital role in periodontal regeneration. Parathyroid hormone (PTH) is important in catabolic regulation on osteoclasts; it also has anabolic effects on hard tissue formation. Using an in vitro wound repopulation model, this study investigated the effect of continual intermittent administration of PTH on PDLFs wound repopulation. Methods and Materials: PDLFs were grown in 12-well plates and divided into 0 (control), 5, 10, 20, 40, and 80 nM of PTH treatments. A 3-mm wound was created on confluent and synchronized cells. Six PTH treatments were initiated using serum-free medium with supplements. Cell repopulation was measured at four time points: 5, 10, 15, and 20 days.

RESULTS

A 5% increase wound repopulation showed an enhancement on day 10 for all treatment groups as compared to control groups. On days 15 and 20, treatment groups showed a decrease in proliferation and migration compared to controls with significant decreases at concentrations of 40 and 80 nM.

CONCLUSION

Continual intermittent treatment with PTH has the potential to enhance proliferation and migration of PDLFs for wound repopulation at early time points. A dose-dependent correlation was seen with a positive trend on day 10 while a significant decrease on day 20.

New Perspectives in the Use of Biomaterials for Periodontal Regeneration

Periodontitis is a disease with a high prevalence among adults. If not treated, it can lead to loss of teeth. Periodontal therapy aims at maintaining patient’s teeth through infection control and correction of non-maintainable anatomies including—when possible—regeneration of lost periodontal tissues. The biological regenerative potential of the periodontium is high, and several biomaterials can be utilized to improve the outcome of periodontal therapy. Use of different natural and synthetic materials in the periodontal field has been studied for many years. The main materials used today in periodontology analyzed in this review are: Resorbable and non-resorbable barrier membranes; autogenous, allogeneic, xenogeneic, and alloplastic bone substitutes; biological agents, such as amelogenins; platelet-derived growth factor; bone morphogenic proteins; rh fibroblast growth factor 2; teriparatide hormone; platelet concentrates; and 3D scaffolds. With the development of new surgical techniques some concepts on periodontal regeneration that were strictly applied in the past seem to be not so critical today. This can have an impact on the materials that are needed when attempting to regenerate lost periodontal structures. This review aims at presenting a rationale behind the use of biomaterials in modern periodontal regeneration

CD8+ T cells mediate the regenerative PTH effect in hPDL cells via Wnt10b signaling

It was the aim of the present investigation to examine whether the stimulating effect of parathyroid hormone (PTH) on human periodontal ligament (hPDL) cell proliferation and differentiation would be enhanced by hPDL/T-cell interaction involving Wnt10b signaling as a mediating pathway. hPDL cells were cultured from healthy premolar tissues of three adolescent orthodontic patients and exposed to PTH(1-34) in monocultures or co-cultures with CD8⁺ T cells. At harvest, proliferation, alkaline phosphatase-specific activity (ALP), and osteocalcin production were determined by immunofluorescence cytochemistry, real-time PCR, biochemical assay, and ELISA. Wnt10b signaling was analyzed by the use of a specific WNT10b neutralizing antibody. PTH(1-34) stimulation of T cells significantly increased Wnt10b expression and production. Wnt10b exposure of hPDL cells enhanced proliferation and differentiation. PDL cells co-cultured with T cells showed a Wnt10b-dependent regulation of proliferation and differentiation parameters. The addition of a Wnt10b-neutralizing Ab to the co-culture medium resulted in a significant inhibition of the PTH(1-34) effect on proliferation, ALP-specific activity, and osteocalcin protein expression. Our findings provide novel insight into the mechanism of action of PTH on hPDL cells and establish the interplay of T cells and hPDL cells via the Wnt10b pathway as a modulating factor for the anabolic properties of the hormone in periodontal regeneration.

Enamel Matrix Derivative Promotes Human Periodontal Ligament Cell Differentiation and Osteoprotegerin Production in vitro

Enamel matrix derivative (EMD) has been used successfully to aid periodontal repair. We sought to elucidate the mechanism of action of EMD and hypothesized that combined exposure to EMD and parathyroid hormone (PTH), which acts anabolicly when administered intermittently, would enhance periodontal ligament cell proliferation, differentiation, and local factor production. Confluent human periodontal ligament cells were exposed to EMD continuously or to PTH(1-34) intermittently, or a combination of both. Cell number, alkaline phosphatase activity, osteocalcin, and osteoprotegerin production were determined. Continuous challenge with EMD resulted in an increase of the differentiation parameters and osteoprotegerin production, while simultaneously inhibiting proliferation. Intermittent PTH(1-34) administration exerted opposite effects. Combined administration of EMD and PTH(1-34) weakened or even nullified the effects seen for the agents alone. These results suggest that EMD promotes periodontal ligament cell differentiation and osteoprotegerin production, potentially resulting in a microenvironment supporting periodontal repair, whereas combining EMD and PTH(1-34) failed to prove beneficial in this respect.

PTH/SDF-1α cotherapy promotes proliferation, migration and osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVES

Stromal cell-derived factor-1α (SDF-1α) plays an important role in tissue regeneration in various tissues including the periodontium. A potential limitation for its use derives from its sensitivity to cleavage by dipeptidyl peptidase-IV (DPP-IV). Parathyroid hormone (PTH) reduces enzymatic activity of DPP-IV and is suggested to be a promising agent for periodontal tissue repair. The purpose of this study was to provide insight into how SDF-1α and intermittent PTH treatment might affect proliferation, migration and osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) in vitro.

MATERIALS AND METHODS

PDLSCs were isolated by the limiting dilution method. Surface markers were quantified by flow cytometry. Cell-counting kit-8 (CCK8), cell migration assay, alkaline phosphatase (ALP) activity assay, alizarin red staining and RT-PCR were used to determine viability, migration and osteogenic differentiation of PDLSCs.

RESULTS

PDLSCs were positive for CD44, CD73, CD90, CD105, CD166 and STRO-1 and negative for CD14, CD34 and CD45. PTH/SDF-1α cotherapy significantly promoted cell proliferation, chemotactic capability, ALP activity and mineral deposition (P<.05). Gene expression level of bone sialoprotein (BSP), runt-related transcription factor 2 (Runx2) and osteocalcin (OCN) were all up-regulated (P<.05).

CONCLUSIONS

PTH/SDF-1α cotherapy promoted proliferation, migration and osteogenic differentiation of PDLSCs in vitro. Cotherapy seemed to have potential to promote periodontal tissue regeneration by facilitating chemotaxis of PDLSCs to the injured site, followed by promoting proliferation and osteogenic differentiation of these cells.

Biologic Agents for Periodontal Regeneration and Implant Site Development

The advancement of molecular mediators or biologic agents has increased tremendously during the last decade in periodontology and dental implantology. Implant site development and reconstruction of the lost periodontium represent main fields in which these molecular mediators have been employed and investigated. Different growth factors trigger different reactions in the tissues of the periodontium at various cellular levels. Proliferation, migration, and differentiation constitute the main target areas of these molecular mediators. It was the purpose of this comprehensive review to describe the origin and rationale, evidence, and the most current understanding of the following biologic agents: Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB), Enamel Matrix Derivate (EMD), Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF), Recombinant Human Fibroblast Growth Factor-2 (rhFGF-2), Bone Morphogenic Proteins (BMPs, BMP-2 and BMP-7), Teriparatide PTH, and Growth Differential Factor-5 (GDF-5).

Tissue engineering for bone regeneration and osseointegration in the oral cavity

OBJECTIVE

The focus of this review is to summarize recent advances on regenerative technologies (scaffolding matrices, cell/gene therapy and biologic drug delivery) to promote reconstruction of tooth and dental implant-associated bone defects.

METHODS

An overview of scaffolds developed for application in bone regeneration is presented with an emphasis on identifying the primary criteria required for optimized scaffold design for the purpose of regenerating physiologically functional osseous tissues. Growth factors and other biologics with clinical potential for osteogenesis are examined, with a comprehensive assessment of pre-clinical and clinical studies. Potential novel improvements to current matrix-based delivery platforms for increased control of growth factor spatiotemporal release kinetics are highlighting including recent advancements in stem cell and gene therapy.

RESULTS

An analysis of existing scaffold materials, their strategic design for tissue regeneration, and use of growth factors for improved bone formation in oral regenerative therapies results in the identification of current limitations and required improvements to continue moving the field of bone tissue engineering forward into the clinical arena.

SIGNIFICANCE

Development of optimized scaffolding matrices for the predictable regeneration of structurally and physiologically functional osseous tissues is still an elusive goal. The introduction of growth factor biologics and cells has the potential to improve the biomimetic properties and regenerative potential of scaffold-based delivery platforms for next-generation patient-specific treatments with greater clinical outcome predictability.

Parathyroid hormone and its effects on dental tissues

In the current era, various pharmacological agents exist for osteoporosis management, and synthetic parathyroid hormone (PTH) (Teriparatide, Forteo) is one of the treatment options. Depending on the timing of administration, PTH has a unique ability to cause both bone apposition and bone resorption. This review focuses on the effects of PTH on the bone, specifically the jaw bones mandible and maxilla. The article briefly describes the fundamental mechanism of PTH action at the molecular level, as well as in experimental animals and in humans. It differentiates intermittent administration of PTH, especially at doses tolerated by humans that increase bone strength and prevent bone fractures, from continuous use that may lead to bone loss. In particular, it shows how intermittent administration of PTH can play a significant role in periodontal repair and implant success via stimulation of bone mineral content especially in the pre-alveolar region.

PTH(1-34)-induced changes in RANKL and OPG expression by human PDL cells modify osteoclast biology in a co-culture model with RAW 264.7 cells

Parathyroid hormone (PTH) is widely accepted as an anabolic agent when administered intermittently. Here, we explored the influence of intermittent PTH(1-34) on the expression of local factors by human periodontal ligament (PDL) cells that modify osteoclast biology. This approach aimed at a further elucidation of the role of the hormone and of PDL cells in the regulation of periodontal tissue homeostasis and of repair processes. In a co-culture model of mature PDL cells and RAW 264.7 cells, intermittent PTH(1-34) induced an increased gene expression for tartrate-resistant acid phosphatase (+84%), cathepsin K (+56%), and vitronectin-receptor (+56%); and an enhanced resorptive activity of differentiated osteoclasts (+154%). These findings were correlated with a reduction of the osteoprotegerin (OPG)/receptor activator of nuclear factor kappaB ligand (RANKL) ratio in the presence of PTH(1-34; -44%). Similar results were obtained when RAW cells were cultured with the conditioned medium of PTH(1-34)-stimulated PDL cells. In contrast, when less mature PDL cells were co-cultured with RAW cells, PTH(1-34) induced an inhibition of osteoclastic differentiation (TRAP, -35%; cathepsin K, -28%; vitronectin-receptor, -35%), a reduction of the resorbed substrate area (-77%) and an increase of the OPG/RANKL ratio (+11%). The conditioned medium of PTH(1-34)-pretreated less mature PDL cells led to a down-regulation of the number and activity of multinucleated cells. These data indicate that intermittent PTH(1-34) modifies the expression of membrane-bound and secreted factors by PDL cells which then in turn alter osteoclast biology. The PDL cell response to PTH(1-34) is specific in terms of cell maturation and the mechanism involved.

The role of periodontal ligament cells in delayed tooth eruption in patients with cleidocranial dysostosis

OBJECTIVE

The clinical appearance of patients with cleidocranial dysplasia (CCD), which is caused by mutations in the RUNX2 gene, is characterized by anomalies of the clavicles, thorax, spine, pelvis and extremities and by disturbances of the skull and tooth development. Of orthodontic relevance are multiple supernumerary teeth associated with delayed tooth eruption. The present investigation is based on the hypothesis that an altered phenotypic expression of periodontal ligament (PDL) cells from CCD patients and a reduced ability of those cells to support the differentiation of bone-resorbing osteoclasts might contribute to delayed tooth eruption.

MATERIALS AND METHODS

To test this hypothesis, PDL cells from healthy donors and from two patients with clinically and molecular biologically diagnosed CCD were characterized for the basal and induced mRNA expression of osteoblast marker genes. The physiological relevance of the findings for the differentiation of osteoclasts was examined in an osteoclast assay, as well as in a co-culture model of PDL cells and osteoclast precursors.

RESULTS

Both CCD patients displayed missense mutations of the RUNX2 gene. The in vitro experiments revealed an unaltered expression of RUNX2 mRNA, however especially in CCD patient 2 there was a reduced basal expression of mRNA for the key regulatory gene for bone remodeling RANKL. Furthermore, compared to the control cells from healthy donors, these factors were less inducible by stimulation of the cultures with 1alpha,25(OH)(2)D(3). In the osteoclast assays as well as in the co-culture experiments, PDL cells from the CCD patients showed a reduced capacity to induce the differentiation of active osteoclasts.

CONCLUSIONS

These data indicate that PDL cells from CCD patients express a less distinctive osteoblastic phenotype resulting in an impaired ability to support osteoclastogenesis which might, in part, account for the delayed tooth eruption that can be observed clinically.

Anabolic effect of intermittent PTH(1-34) on the local microenvironment during the late phase of periodontal repair in a rat model of tooth root resorption

This study examined the histological changes and possible effects of intermittent parathyroid hormone (PTH) (1-34) treatment during the early and late phase of periodontal repair in a rat model of tooth root resorption. In a total of 70 animals, which either received intermittent PTH(1-34) systemically or sham injections for up to 70 days after discontinuation of an orthodontic force, histological characteristics were correlated to time-dependent distinct expression patterns of osteoprotegerin and receptor activator of nuclear factor kappaB ligand by PDL cells in the former compression and tension side of tooth movement by means of immunohistochemistry and histomorphometrical analysis. The balance of these key regulators of bone remodeling was demonstrated to be shifted in favor of hard tissue repair by intermittent PTH administration, which was demonstrated to exert anabolic effects in several cell culture and animal experiments as well as in humans, in the late phase of repair. These data indicate a role for PDL cells as potent regulators of periodontal repair by modifying the local microenvironment and point to the anabolic potential of an intermittent PTH administration to support these reparative processes.

Subculture affects the phenotypic expression of human periodontal ligament cells and their response to fibroblast growth factor-2 and bone morphogenetic protein-7 in vitro

BACKGROUND AND OBJECTIVE

Although periodontal ligament cells display several osteoblastic traits, their phenotypic expression is still not well established. It remains a matter of debate whether they resemble a terminally differentiated cell type or an intermediate maturation state that potentially can be directed towards a fibroblastic or an osteoblastic phenotype.

MATERIAL AND METHODS

To explore the characteristics of periodontal ligament cells in greater detail, fourth-passage, sixth-passage and eighth-passage human periodontal ligament cells were cultured for up to 3 wk. Ki-67, alkaline phosphatase, osteocalcin, osteoprotegerin and receptor activator of nuclear factor-kappaB ligand (RANKL) mRNA expression was quantified by real-time polymerase chain reaction. Furthermore, the cellular response to fibroblast growth factor-2 and bone morphogenetic protein-7 was examined in first-passage and fourth-passage cells. Dermal fibroblasts (1BR.3.G) and osteoblast-like cells (MG63) served as reference cell lines.

RESULTS

Proliferation decreased over time and was highest in fourth-passage cells. The expression of differentiation parameters, osteoprotegerin and RANKL increased with culture time and was higher in fourth-passage cells than in cells of later passages. The RANKL/osteoprotegerin ratio increased steadily until day 21. Administration of fibroblast growth factor-2 enhanced cell numbers in both passages, whereas alkaline phosphatase and osteocalcin production remained unchanged. By contrast, exposure of periodontal ligament cells to bone morphogenetic protein-7 resulted in a reduction of cell number in the first and fourth passages, whereas the production of alkaline phosphatase and osteocalcin was enhanced. In dermal fibroblasts, differentiation parameters did not respond to both stimuli. MG63 cells behaved similarly to periodontal ligament cells.

CONCLUSION

These results indicate that subculture affects the phenotypic expression of human periodontal ligament cells with respect to the characteristics that these cells share with osteoblasts. Furthermore, the periodontal ligament cell phenotype can be altered by fibroblastic and osteoblastic growth factors.