Joseph Shanfeld

Interleukin 1 beta and prostaglandin E are involved in the response of periodontal cells to mechanical stress in vivo and in vitro

Cytokines are local mediators released by cells of the immune system in response to stimulation by a variety of agents. These polypeptides may interact directly or indirectly with bone cells. The objectives of this study were (1) to localize prostaglandin E (PGE) and the cytokine interleukin-1 beta (IL-1 beta) in the periodontal ligament after the application of mechanical force to teeth in vivo and (2) to determine the effects of mechanical stress or IL-1 beta (or the two in combination) on PGE synthesis and bone resorption by fibroblasts in the human periodontal ligament (PDL). In 24 female cats, one maxillary canine was tipped distally by 80 gm force for 12 hours, 24 hours, or 7 days. PGE and IL-1 beta were localized immunohistochemically in serial jaw sections, and semiquantitation of cellular-staining intensity was done by microphotometry. Unstressed periodontal ligament cells stained mildly for PGE and IL-1 beta, but the staining intensity increased significantly in sites of tension. Human periodontal ligament fibroblasts were preincubated with mechanical stress and/or IL-1 beta in the presence or absence of indomethacin for 1 hour. Then the media were replaced by BGJb (Fitton-Jackson modification) medium (GIBCO), and incubation was continued for 4, 8, or 24 hours in conditioned media. PGE concentrations in conditioned media were determined by radioimmunoassay, and bone-resorbing activity in conditioned media was assessed by 45Ca release from prelabeled neonatal mouse calvaria. The conditioned media derived from cells stimulated by mechanical stress plus IL-1 beta caused significantly more bone resorption than the conditioned media obtained from cells that had been treated by each factor alone. The addition of indomethacin did not inhibit bone resorption completely. These results demonstrate that periodontal ligament cells respond to mechanical stress by increased production of PGE, and that IL-1 beta enhances this response.

Electric currents, bone remodeling, and orthodontic tooth movement: II. Increase in rate of tooth movement and periodontal cyclic nucleotide levels by combined force and electric current☆

Piezoelectric currents in mechanically stressed bone were implicated in the activation of bone cells. The objectives of this experiment were to determine the usefulness of exogenous electric currents in accelerating orthodontic tooth movement and to study the effect of electric-orthodontic treatment on periodontal cyclic nucleotides. Maxillary canines were tipped in five cats by 80 g force. Two groups of five cats each were treated by an electric-orthodontic procedure to one maxillary canine for 7 and 14 days, respectively. Teeth treated by force and electricity moved significantly faster than those treated by force alone. Enhanced bone resorption was observed near the anode (PDL compression site), while bone formation was pronounced near the cathode (PDL tension site). Staining for cyclic nucleotides was increased when electric stimulation was added to the mechanical force. These results suggest that orthodontic tooth movement may be accelerated by the use of locally applied electric currents.

Electric currents, bone remodeling, and orthodontic tooth movement

Piezoelectric currents in mechanically stressed bone were implicated in the activation of bone cells. The objectives of this experiment were to determine the usefulness of exogenous electric currents in accelerating orthodontic tooth movement and to study the effect of electric-orthodontic treatment on periodontal cyclic nucleotides. Maxillary canines were tipped in five cats by 80 g force. Two groups of five cats each were treated by an electric-orthodontic procedure to one maxillary canine for 7 and 14 days, respectively. Teeth treated by force and electricity moved significantly faster than those treated by force alone. Enhanced bone resorption was observed near the anode (PDL compression site), while bone formation was pronounced near the cathode (PDL tension site). Staining for cyclic nucleotides was increased when electric stimulation was added to the mechanical force. These results suggest that orthodontic tooth movement may be accelerated by the use of locally applied electric currents.Osteogenesis has been found to occur in response to the application of electric currents to bone. The objective of this experiment was to study the effects of D.C. electric currents on periodontal tissues in cats. Cyclic nucleotides, compounds known to be involved in cellular activation, were studied by immunohistochemistry in the involved tissues. Three groups of three young adult cats each were treated for 1, 3, and 7 days, respectively, by a device delivering 15 microamperes of direct current to bone osteoblasts and PDL cells stained intensely for cAMP and cGMP were observed adjacent to the cathode and anode, and bone apposition was found near the cathode. These results suggest that electric stimulation enhances cellular enzymatic phosphorylation activities in periodontal tissues and may be a potent tool in accelerating alveolar bone turnover.

The effect of ibuprofen on the level of discomfort inpatients undergoing orthodontic treatment

Studies have shown that patients undergoing orthodontic tooth movement can experience varyingdegrees of discomfort. The objective of this study was to determine whether nonsteroidal antiinflammatory agents, such as aspirin or ibuprofen, which inhibit prostaglandin synthesis through acetylation and inactivation of the enzyme cyclooxygenase, can suppress orthodontic discomfort by inhibiting the inflammatory response normally observed after orthodontic adjustments. A total of 77 patients were included in a double-blind, randomized, parallel, placebo-controlled, single-dose, analgesic efficacy evaluation of ibuprofen and aspirin. Patients were divided into three groups. Group A received one dose of the drug ibuprofen (400 mg), group B received aspirin (650 mg), and group C received a placebo (beta-lactose). The level of discomfort was assessed using a visual analogue scale at 2, 6, and 24 hours and 2, 3, and 7 days after the insertion of either orthodontic separators or an initial arch wire. A repeated measures analysis of variance and post hoc studentized range statistics showed that the placebo group had significantly more discomfort than either the ibuprofen or the aspirin group at all the time intervals tested. In addition, ibuprofen produced significantly less discomfort than aspirin at the 6 and 24-hour and 2-day time phase after separator placement; and 2 and 6 hours and 2, 3, and 7 days after arch wire placement. These results support a recommendation for ibuprofen as a preferred analgesic in the treatment of discomfort because of postorthodontic adjustments.

Cyclic AMP levels in alveolar bone of orthodontically-treated cats

Abstract Specific biochemical changes in mechanically stressed bone were studied in cats, orthodontically treated for periods of time ranging from 1 hr to 28 days. Alveolar bone samples were obtained from compression and tension sites surrounding tipping maxillary and mandibular canines. The samples were extracted with water, boiled, homogenized and the supernatants were assayed for cyclic AMP by a protein-binding method. It was found that cyclic AMP levels in treated sites initially decreased, then increased after 1–2 days and remained elevated to the end of the experimental period. It was suggested that the initial decrease in cyclic AMP at the compression sites was due to periodontal ligament cell-necrosis, while at the tension sites the decrease was due to a rapid increase in the cell population. The elevation in the level of cyclic AMP observed 2 weeks after the initiation of treatment was probably due to increased bone remodelling activity by a maturing cell population with a slow rate of growth. The level of cyclic AMP in bone after application of orthodontic forces may be the result of increased phosphodiesterase activity, and/or the involvement of a relatively small number of cells. It is concluded that mechanical forces can act as a first messenger and facilitate bone formation and resorption by activation of the cyclic nucleotide system.

Biochemical mediators of the effects of mechanical forces and electric currents on mineralized tissues

SummaryCyclic nucleotides (cAMP and cGMP) and prostaglandin E (PGE) have been implicated as possible mediators of the effects of external stimuli on bone cells. The objective of this study was to determine changes in relative levels of these substances in mineralized tissue cells in response to mechanical and electrical stimuli, by the use of a combined immunohistochemical-microphotometric procedure. Canine teeth of eight 10–12 month-old female cats were tipped distally with 80 g force for either 1 h or 14 days. After 1 h, a slight elevation of staining intensity in alveolar bone osteoblasts and periodontal ligament (PDL) cells was observed at sites of tension and compression. After 14 days of treatment, this effect was markedly increased. Fifteen female cats, 10–12 months old, received electric stimulation (20 µ amperes d.c.) to the gingiva of 1 maxillary canine for 1, 5, 15, 30, or 60 min. At the cathode, significant increases of staining intensity in periosteal osteoblasts for cAMP, cGMP, and PGE were found at 15 and 60 min. At the anode, a significant rise in the staining intensity of these cells for PGE was seen at 15 min; at 60 min, cGMP and PGE, but not cAMP, were elevated. These results demonstrate the usefulness of the immunohistochemical technique in detecting relative changes in mineralized tissue cell content of cyclic nucleotides and prostaglandins in response to local application of physical stimuli of short and long duration.

A new experimental model for studying the response of periodontal ligament cells to hydrostatic pressure

An apparatus was developed to apply positive or negative hydrostatic pressure dynamically to periodontal ligament (PDL) cells in vitro. The objective of this investigation was to construct this apparatus and to determine its effects on PDL cells. Human PDL cells were collected from freshly extracted premolars. At the sixth passage, the cells were mechanically stimulated by this apparatus at different magnitudes of continuous positive or negative hydrostatic pressures (PHP or NHP, respectively). The application of PHP between 0.3 and 30 gm/cm2 significantly enhanced prostaglandin E (PGE) production and intracellular cyclic AMP (cAMP) of the cells. In contrast, perturbation by NHP significantly decreased PGE production and intracellular level of cAMP. Proliferation rate increased significantly at 24 and 48 hours due to stimulation of these cells with -30 gm/cm2 of NHP. Challenging these cells with +30 gm/cm2 of PHP significantly decreased the proliferation rate of these cells at 24 and 48 hours. Stimulation by PHP between +30 to +600 gm/cm2 increased cell length and width and appeared to increase surface area attachment to the bottom of the culture dishes. In contrast, NHP (between -30 and -600 gm/cm2) decreased these dimensions and appeared to reduce the surface area of attachment. These results indicate that this type of mechanical perturbation of PDL cells produces physiologic responses and is not detrimental to their vitality.

Involvement of PGE Synthesis in the Effect of Intermittent Pressure and Interleukin-1β on Bone Resorption

Human periodontal ligament (PDL) fibroblasts, cultured from extracted healthy premolars, and a cloned osteogenic cell line (MC3T3-E1) were used in this study to determine the effect of intermittent pressure on bone resorption. Cells (1 x 105) were incubated with BGJb medium in the presence or absence of the following factors: intermittent negative ( - 30 g/cm2) or positive (30 g/cm2) hydrostatic pressure and interleukin-lp (IL-1β, 1 ng/mL), for 24 h. Conditioned media (CM) generated from cultures of either cell types were used for prostaglandin E (PGE) assay, bone resorption assay, and assessment of osteoclast (OC)-like cell formation. Unstimulated PDL fibroblasts or MC3T3-E1 cells produced measurable amounts of PGE and bone-resorbing activity as measured by 45Ca released from mouse calvaria and OC-like cells. IL-1β-treated cells showed significantly elevated levels of PGE, bone resorption, and OC-like cell formation, as compared with unstimulated cells. Intermittent positive pressure (IPP) alone stimulated PGE production, but the resultant CM did not stimulate bone resorption or OC-like cell formation when IPP was applied to either cell type. The application of IPP, together with IL-1β in CM, caused a slight increase in the number of a-like cells, as compared with that of IL-1β-treated CM in both cell types. On the other hand, direct application of IPP on mouse bone-marrow cultures significantly increased the number of OC-like cells. This effect was additive in combination with either CM from unstimulated cells or exogenous addition of PGE2. These results suggest that locally produced autocrines or paracrines can modify the effect of mechanical stress on periodontal and bone cells via PGE synthesis. One of the roles of PGE elaboration in response to mechanical or chemical stimuli is osteoclast recruitment.

Substance P immunoreactivity in periodontal tissues during orthodontic tooth movement.

Neurotransmitters, such as substance P (SP), may mediate the biological response to mechanical stress applied to teeth during orthodontic treatment. This hypothesis was investigated immunohistochemically on maxillae of cats which had one maxillary canine tipped distally for a period of time ranging from 1 h to 14 days. Horizontal histological sections 5 microns thick, collected on adhesive tape while still frozen, then freeze-dried, were stained by an immunoglobulin-enzyme bridge method using rabbit anti-SP polyclonal antibodies. The specificity of the staining was evaluated either by using the serum of non-immunized rabbits in lieu of anti-SP serum, or by pre-incubating the anti-SP serum with the antigen. Only sparse SP-like immunoreactivity was detected in the dental pulp, near or in the walls of blood vessels, or in the periodontal ligament (PDL) of unstressed canines. However, the density of neuronal elements exhibiting positive staining for SP appeared to increase markedly after application of an orthodontic force. This phenomenon occurred rapidly (3 h) in the dental pulp, but later in the PDL (24 h to 14 days), mainly at compression sites. These results demonstrate that the stimulation of periodontal nerve terminals by means of orthodontic forces may induce the peripheral release of the neurotransmitter SP, suggesting that it may be an initial trigger for a biochemical cascade which comprises the activation of various types of PDL cells.

The interactive effects of mechanical stress and interleukin-1β on prostaglandin E and cyclic AMP production in human periodontal ligament fibroblasts in vitro: Comparison with cloned osteoblastic cells of mouse (MC3T3-E1)

Human periodontal ligament fibroblasts and a cloned osteogenic cell line (MC3T3-E1) were seeded (4 x 10(5) cells) on 60 mm Petriperm dishes, which have a flexible plastic growth surface. Cells were stretched by placing the dish on top of a spheroidal convex template, equilibrated to 37 degrees C. The amount of stretch was varied by changing the curvature of the template and calculated as percentage stretch. Both types of cell responded to mechanical stress by elevated synthesis of PGE and cAMP; the addition of interleukin-1 beta to mechanically stretched cells produced further elevation. Synergism between mechanical stress and interleukin-1 beta was found at certain lengths of incubation. The production of cAMP was secondary and dependent on the newly synthesized PGE, as shown in the presence of indomethacin. The two cell types were also different in terms of the timing of their response to mechanical stress and interleukin-1 beta. In the absence of stimuli, periodontal fibroblasts tended to produce PGE continually over time, whereas the MC3T3-E1 cells did not. However, both cell types had elevated PGE levels in response to the stimuli used in this experiment. Periodontal fibroblasts responded to mechanical stress and interleukin-1 beta with significant elevations of PGE as early as 15 min, whereas the MC3T3-E1 cells required 2 h to produce significant elevations for mechanical stress and 15 min for interleukin-1 beta. These findings indicate that the chemical and mechanical signals on these cells are mediated by surface receptors. Locally produced autocrine or paracrine factors can modify the effect of mechanical stress on periodontal and bone cells via the cAMP pathway.(ABSTRACT TRUNCATED AT 250 WORDS)