Evidence for fibroblasts as the major source of prostacyclin and prostaglandin synthesis in dental cyst in man

Distraction Sugosteogenesis: Its Biologic Bases and Therapeutic Principles

PURPOSE

Recently, the terms sugosteogenesis and distraction sugosteogenesis have been introduced to the scientific literature. While the former describes a biologic phenomenon, the latter refers to the clinical technique which relies on the accelerated normal bone healing process that takes place at the osseous walls surrounding a cystic cavity when active negative pressure is applied. The purpose of this study is to provide the biologic bases and the therapeutic principles of this emerging technique. Employing well-stablished biologic principles, clinical evidence from analogous techniques, emerging experimental data, and circumstantial evidence, this study presents the possible mechanism of action of the evacuator for odontogenic cysts (Evocyst), a closed, vacuum-like drain system intended to treat cystic conditions using negative pressure.

METHODS

A review of the literature was done. Keywords for the Medline search were: marsupialization, decompression, odontogenic cysts, effects of negative pressure on bone, and negative pressure wound therapy. In addition, relevant publications from the reference list of the retrieved studies were considered. The matches were evaluated for relevance and analyzed accordingly. Clinical reports used to illustrate the concept of distraction sugosteogenesis were performed following the Declaration of Helsinki on medical protocol and ethics.

RESULTS

Currently, the standard of care to manage odontogenic cystic lesions includes marsupialization, enucleation and curettage, decompression, and surgical resection. However, there is a need for an alternative option in which the entity could be treated while promoting bone formation. With large odontogenic cystic conditions treated in a short period of time, distraction sugosteogenesis appears to be a choice.

CONCLUSION

The application of negative pressure to osseous cells produces a stretching that creates mechanical cues that trigger signaling pathways, promotes fluid flow, and enhances angiogenesis. All of them, combined, may explain sugosteogenesis. The clinical application of such parameters may explain the good clinical results obtained with the Evocyst.

Misoprostol enhances early fracture healing: a preliminary biochemical study on rats

The purpose of this study was to demonstrate if misoprostol, a methyl derivative of prostaglandin E1, enhanced fracture healing in 54 male adult Sprague-Dawley rats. The base level of serum alkaline phosphatase (ALP) in 6 randomly selected rats was measured. Rats were then randomly separated into 3 groups and their tibias fractured. First and second groups received misoprostol for 4 weeks, 100 and 300 microg/kg/day respectively via oral route. The third group had no misoprostol. p<0.05 was considered significant. Elevation of ALP level in the 2nd week was significant in group 1, it was not in group 2 or 3; in the 4th week it was significant in all groups. In conclusion dosage dependent osteoinductive effect of misoprostol was shown in the early bone healing period. Biochemical findings in the latter period did not show any inhibitory effect of misoprostol on bone healing. Further studies, probably biomechanical, may be required for the final verdict.

Human Follicular Dendritic Cells Express Prostacyclin Synthase: A Novel Mechanism to Control T Cell Numbers in the Germinal Center

Stromal cells in the lymphoid organs provide a microenvironment where lymphocytes undergo various biological processes such as development, homing, clonal expansion, and differentiation. Follicular dendritic cells (FDCs) in the primary and secondary follicles of the peripheral lymphoid tissues interact with lymphocytes by contacting directly or producing diffusible molecules. To understand the biological role of human FDC at the molecular level, we developed a mAb, 3C8, that recognizes FDC but not bone marrow-derived cells. Through expression cloning and proteome analysis, we identified the protein that is recognized by 3C8 mAb, which revealed that FDC expresses prostacyclin synthase. The 3C8 protein purified from FDC-like cells indeed displayed the enzymatic activity of prostacyclin synthase and converted PGH2 into prostacyclin. In addition, prostacyclin significantly inhibited proliferation of T cells but delayed their spontaneous apoptosis. These findings may help explain why T cells constitute only a minor population compared with B cells in the germinal center.

Relation between size of odontogenic jaw cysts and the pressure of fluid within

Intracystic fluid pressure may have a crucial role in the growth of odontogenic jaw cysts. In this study, we investigated the relation between the size of the cyst and the pressure of the fluid within odontogenic keratocysts, dentigerous cysts, and radicular cysts. The radiolucent area of the cyst on a panoramic radiograph was linearly related to the volume in the cavity, and the correlation coefficient (gamma) was 0.70 (n = 25, P < 0.001). Intracystic fluid pressure correlated negatively with the radiolucent area in odontogenic keratocysts (gamma = -0.76, n = 9, P = 0.02), dentigerous cysts (gamma = -0.54, n = 16, P = 0.03), and radicular cysts (gamma = -0.69, n = 10, P = 0.03). The values of [(intracystic fluid pressure (mmHg)) x (radiolucent area (cm(2)))] did not differ significantly among the three types of cyst. Intracystic fluid pressure may therefore be negatively related to the size of all three types of cyst.

Contribution of membrane-associated prostaglandin E2 synthase to bone resorption

This study initially confirmed that, among prostaglandins (PGs) produced in bone, only PGE(2) has the potency to stimulate osteoclastogenesis and bone resorption in the mouse coculture system of osteoblasts and bone marrow cells. For the PGE(2) biosynthesis two isoforms of the terminal and specific enzymes, membrane-associated PGE(2) synthase (mPGES) and cytosolic PGES (cPGES) have recently been identified. In cultured mouse primary osteoblasts, both mPGES and cyclooxygenase-2 were induced by the bone resorptive cytokines interleukin-1, tumor necrosis factor-alpha, and fibroblast growth factor-2. Induction of mPGES was also seen in the mouse long bone and bone marrow in vivo by intraperitoneal injection of lipopolysaccharide. In contrast, cPGES was expressed constitutively both in vitro and in vivo without being affected by these stimuli. An antisense oligonucleotide blocking mPGES expression inhibited not only PGE(2) production, but also osteoclastogenesis and bone resorption stimulated by the cytokines, which was reversed by addition of exogenous PGE(2). We therefore conclude that mPGES, which is induced by and mediates the effects of bone resorptive stimuli, may make a target molecule for the treatment of bone resorptive disorders.

Levels of GM-CSF, IL-3, and IL-6 in fluid and tissue from human radicular cysts

Cytokines released by immune system cells play an important role in cyst enlargement. This study aimed to determine, by ELISA, the levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), and IL-6 in fluid and tissue from human radicular cysts. GM-CSF was found in 42.8% of the fluid samples (164.3 pg/mL) and IL-6 in 92.8% (641.4 pg/mL). No IL-3 was detected in any fluid samples. In the tissue samples, 28.6% were positive for IL-3 (369.2 pg/mL), 86.4% for IL-6 (92.4 pg/mL), and 95.8% for GM-CSF (200.5 pg/mL). It can be concluded that GM-CSF and IL-6 were widely found in the fluid and tissue samples. In contrast, IL-3 was found only in the cystic tissue, even though in few lesions. These cytokines may contribute to the inflammation, cystic growth, and bone resorption that characterize cystic lesions.

Fibrous tissue of subchondral cystic lesions in horses produce local mediators and neutral metalloproteinases and cause bone resorption in vitro

OBJECTIVES

To define the release of nitric oxide (NO), prostaglandin E2 (PGE2), and the neutral metalloproteinases (NMPs) in horses with subchondral cystic lesions (SCL) and to study bone resorption triggered by conditioned media of fibrous tissue of SCL in vitro.

STUDY DESIGN

Equine explant cultures of fibrous tissue of SCL, and synovial membrane and articular cartilage of normal horses and horses affected with moderate and severe osteoarthritis were performed. NO, PGE2, and NMP concentrations of media samples were measured, and osteoclast formation and activation was studied in vitro.

ANIMALS

Experiment 1: 32 horses with SCL (n = 8), normal joints (7), and joints with moderate (7) and severe (10) osteoarthritis (OA). Experiment 2: 22 horses with SCL (n = 3), normal joints (7), and chip fractures (12). Experiment 3: Conditioned media of fibrous tissue from 3 horses with SCL of the medial femoral condyle (n = 1), distal metacarpal bone (1), and tarsal bone (1).

METHODS

Determinations of local mediator concentrations were made with the Griess assay for NO and an enzyme immunoassay kit for PGE2 concentrations in biological fluids. Enzyme activities were assessed with radiolabeled substrates indicating collagenolytic, gelatinolytic, and caseinolytic activities. The resorption pit assay was used to assess osteoclast recruitment and activity.

RESULTS

Fibrous tissue of SCL produced NO, PGE2, and NMPs. Of all the variables measured, PGE2 concentrations were the highest in cystic tissue of SCL compared with synovial membrane and articular cartilage from normal joints and joints with chip fractures, indicating that this mediator may play an important role in pathological bone resorption associated with SCL. These findings were supported by the observation that conditioned media of SCL tissue were capable of recruiting osteoclasts and increasing their activity.

CONCLUSION

Fibrous tissue of SCL released NO, PGE2, and NMPs into the culture media. It is suspected that intralesional fibrous tissue may play an active role in the pathological process of bone resorption occurring in SCL in horses and may be partly responsible for the maintenance, slow healing rate, and expansion of these lesions.

CLINICAL RELEVANCE

Understanding the pathogenesis of SCL will help to establish successful therapy in horses affected with SCL.

The use of analgesics in the management of pain in rheumatic diseases

Pain is the most common complaint of patients who see rheumatologists. In this article, the current treatment options for pain are reviewed; these include acetaminophen, nonsteroidal anti-inflammatory drugs, new specific cyclooxygenase-2 inhibitors, opioid analgesics, centrally acting muscle relaxants, antidepressants, and topical analgesics and counterirritants. The doses of medication and known adverse effects of these medications are highlighted.

Immunohistochemical detection of prostaglandins E2, F2 alpha, and 6-keto-prostaglandin F1 alpha in experimentally induced periapical inflammatory lesions in rats

The immunohistochemical localization of prostaglandin (PG) E2, PGF2 alpha, and 6-keto-PGF1 alpha (a stable metabolite of PGI2) was demonstrated in rat periapical inflammatory lesions induced by opening the pulp chamber. Two wk postoperatively, suppurative periapical lesions were formed, and active bone resorption was seen surrounding these lesions. Immunohistochemical examination showed that macrophages infiltrating in inflammatory tissue were positively stained for the examined PGs. In some lesions, wherein acute inflammatory changes subsided and proliferation of fibroblasts started, the fibroblasts were positively stained for 6-keto-PGF1 alpha. Osteocytes and osteoblasts were also positive for 6-keto-PGF1 alpha not only in experimental animals, but also in untreated animals. However the staining intensity of the PG in these cells was higher in periapical lesions than in normal condition. These findings suggested that the cellular sources of the PGs in the periapical lesions are mainly macrophages and fibroblasts, and that the PGs produced by these cells, and possibly osteoblast and osteocytes, may contribute to the osteolytic resorption of periapical lesions.

The role of endotoxin and cytokines in the pathogenesis of odontogenic cysts

Odontogenic cysts arise from tooth-forming epithelial residues. The stimulus for the formation of radicular cysts is thought to be endotoxin released from the infected necrotic tooth pulp. However, in keratocysts and follicular cysts, such a stimulus is not present. In order to investigate what drives the cyst epithelium to proliferate, explant media and fluids from 16 radicular cysts, eight keratocysts and seven follicular cysts and explant media from four specimens of non-inflamed gingival tissue were examined for the presence of endotoxin and cytokines. Cyst fluids were also cultured for 72 h in anaerobic and aerobic conditions to detect micro-organisms. Endotoxin from three different bacteria, cytokines [interleukin-(IL) 1 alpha, IL-1 beta and IL-6] as well as prostaglandin E2 (PGE2) were tested in an epithelial cell-proliferation assay. As the cyst epithelium is supported by a connective tissue capsule, the effect of fibroblast culture media on epithelial cell proliferation was also investigated. The results showed significantly higher concentrations of endotoxin in radicular cyst fluid than in the keratocyst or the follicular cyst. None of the cyst fluids contained micro-organisms. Immunoassays demonstrated the presence of IL-1 alpha and -6 in all fluids and explants tested; IL-1 beta was only found in the inflammatory radicular cysts. However, reverse transcriptase-polymerase chain reaction showed that mRNAs for IL-1 alpha, -1 beta and -6 were present in all cyst types. Proliferation studies indicated that endotoxin and the cytokines had a mitogenic effect on epithelia at low concentrations; PGE2 had very little effect at low concentrations, and had an inhibitory effect at high concentrations. Cyst fibroblast culture media had a mitogenic effect on the epithelia that was enhanced by the presence of endotoxin.

Immunohistochemical characterisation of odontogenic cysts with mesenchymal and myofilament markers

The aim of the present investigation was to analyse the fibroblast phenotype in the main groups of odontogenic cysts. We have examined the muscle differentiation markers alpha-smooth muscle actin (ASMA) and desmin and the presence of vimentin using immunocytochemistry. Fibroblasts of other cyst types, hyperplastic fibrous lesions, and from several normal sites were used as controls. All fibroblasts stained for vimentin, but a variable proportion of cyst wall fibroblasts were also positive for the antibody to ASMA. Their distribution was not random and two positive zones could be distinguished, an inner subepithelial layer and an outer region adjacent to the bone-facing surface. This staining pattern was observed for all the types of odontogenic cysts studied, although the subepithelial staining was more frequent in the presence of an inflammatory infiltrate. The contractile nature of these cells was supported by their ultrastructural appearance. Some non-odontogenic cysts showed subepithelial fibroblasts strongly labelled with ASMA; in the control tissues ASMA was negative except for pericytes and some groups of cells in supracrestal gingiva. These results demonstrate a distinct cell population with a myofibroblast phenotype in the odontogenic cyst wall and with a distribution which may enable them to contribute to wall elasticity constraining cyst expansion. Their presence in all types of odontogenic cyst studied would suggest that myofibroblast formation is independent of the pattern of cyst growth.

Interleukin-1: the principal osteolytic cytokine produced by keratocysts

Fragments of keratocysts removed at operation were maintained in explant culture and the media were assayed for the biological activity of the potent osteolytic cytokines--interleukin (IL)-1, interleukin (IL)-6 and tumour necrosis factor (TNF). Media were also assayed for their ability to stimulate bone resorption. All six cysts examined released IL-1 and IL-6 bioactivity but TNF bioactivity was unmeasurable. Dialysed cyst media stimulated bone resorption and this could be completely inhibited by a monospecific antibody which neutralized IL-1 alpha and IL-1 beta. Immunohistochemical staining of cryostat sections of keratocysts revealed the presence of IL-1 alpha and IL-6 in cyst epithelial cells but not in other cell types. Sections did not react with antibodies to IL-1 beta or TNF. It is therefore proposed that IL-1 alpha is the major osteolytic cytokine produced by keratocysts and that IL-6 and IL-1 may contribute to keratocyst growth by promoting epithelial cell proliferation and bone resorption, respectively.

Effect of lipopolysaccharide from Porphyromonas gingivalis on prostaglandin E2 and interleukin-1-beta release from rat periosteal and human gingival fibroblasts in vitro

Lipopolysaccharide (LPS) was extracted from Porphyromonas gingivalis (W83) by the Westphal procedure, nuclease-digested and ultracentrifuged. Fibroblasts were obtained from human gingival tissue and rat periosteum, grown to confluence then stimulated in serum-free medium with 0.1, 1.0 and 10.0 micrograms/ml LPS. The levels of prostaglandin E2 (PGE2) and interleukin-1 beta (IL-1 beta) released were measured after 2, 4 and 6 d by specific radioimmunoassays. Unstimulated gingival fibroblasts produced low levels of PGE2 (24.5 +/- 1.5 (SD) ng/ml) and IL-1 beta (0.34 +/- 0.29 ng/ml). LPS stimulated statistically significant dose-related increases in PGE2 and IL-1 beta at the concentrations of LPS tested. At 10.0 micrograms/ml, LPS-stimulated fibroblasts produced 363.5 +/- 40.3 ng/ml PGE2 and 1.81 +/- 0.1 ng/ml IL-1 beta in 6 d. These results demonstrate that LPS from P. gingivalis is capable of stimulating PGE2 and IL-1 beta release from fibroblasts. This would appear to be an additional mechanism by which LPS can induce tissue breakdown in periodontal disease.

A histochemical study of bone remodeling during experimental apical periodontitis in rats

An apical periodontitis experimental model was produced by means of opening the pulp chamber of the mandibular first molar in Wistar strain rats. In particular, the behavior of bone tissue in the vicinity of the root apex was investigated histochemically, ultrastructurally, and quantitatively. In addition, in order to demonstrate the effects of prostaglandin on the formation process of apical periodontitis, we examined the effects of indomethacin on bone remodeling during experimental apical periodontitis. These experiments suggested that prostaglandin may stimulate osteoclastic bone resorption and that the relationship between bone resorption and formation in apical periodontitis is a coupling phenomenon.

The role of prostaglandins in bone in vivo

Prostaglandins of the E series, primarily E2 and E1, have the greatest activity in bone. Following discovery of their potent ability to stimulate bone resorption in vitro, clinical investigations have placed prostaglandins at sites of localized bone resorption associated with inflammatory or space occupying lesions in vivo. These studies have shown that prostaglandin production at such sites may be increased by cytokines such as interleukin-1 but the mechanisms by which prostaglandins stimulate bone resorption are not yet known. Observation of periosteal bone formation in patients given, pharmacological doses of prostaglandin has led to investigation of its bone forming activity. Young, growing rats have increased metaphyseal bone formation and this is accompanied by increased periosteal and endocortical bone formation in older animals. In the mature animals there is a generalized activation of remodelling with increased formation in the remodeling cycle. This is also seen in oophorectomized rats and results in repletion of the lost bone in this model of osteoporosis. In animal models of localized disuse osteopenia, prostaglandins are found to be elevated at the site of bone loss and prostaglandin inhibitors at least partially protect against the exaggerated resorption that occurs. This is also seen in models of orthodontic tooth movement, periodontitis and osteomyelitis. Prostaglandin synthesis inhibitors have been shown to delay healing of bone and this has led to limitations on their use clinically in some situations. Exogenously administered prostaglandins have been found to enhance periosteal callus formation, but healing is not uniformly enhanced. Prostaglandins have also been associated with hypercalcemia in certain animal tumors that model human hypercalcemia of malignancy but are probably most important in this condition as mediators in the localized resorption of bone at tumor sites. These in vivo studies have shown that prostaglandins are involved with increases in both bone formation and bone resorption. In vitro studies have shown that prostaglandins stimulate osteoblasts as well as osteoclastic bone resorption but understanding these effects under in vivo conditions will require further investigation.

Parathyroid hormone, but not prostaglandin E2, changes the shape of osteoblasts maintained on bone in vitro

Parietal bones from 2-week-old rats were dissected free from the sutural regions, dura mater, and periosteum, leaving the surface covered with osteoblasts and some osteoclasts. Prostaglandin (PG) production by these "stripped" bones under basal conditions and after exposure to parathyroid hormone (PTH) was measured by radioimmunoassay of the culture medium (minimum essential medium with or without added 10% heat-inactivated fetal calf serum). Cultured specimens were examined by scanning electron microscopy for changes in osteoblast length, orientation, ruffling, and overlap. As demonstrated previously, PTH caused the osteoblasts to elongate, align, and show fewer ruffles compared to controls. PTH increased PG synthesis by the stripped bones. Indomethacin inhibited PG formation but did not affect the osteoblast shape change. PGE2, indomethacin, or both drugs together had no discernible effect on any morphologic features. These findings indicate that PGE2 does not change osteoblast shape and that the cell shape change with PTH is not mediated by endogenous prostanoids.

Mast cells in human odontogenic cysts

Mast cells have been shown to be present in substantial numbers in both nonkeratinizing and keratinizing odontogenic cysts and could be seen in the connective tissue capsule and the epithelial lining. Within the cyst capsule, mast cells were more prevalent just beneath the epithelium than in deeper areas. This distribution pattern for mast cells is in accord with the histochemical picture for heparin staining in odontogenic cysts. In the non-keratinizing cysts, there appeared to be some trend towards mast cells being associated with increasing inflammation but not in the odontogenic keratocyst. No evidence could be found for distinct mast cell subpopulations in odontogenic cysts. The presence of mast cells in odontogenic cyst could contribute to their pathogenesis in several ways.

Interleukin 1-like activity in cystic lesions of the jaw

Odontogenic cyst capsules were cultured in vitro and the culture media analysed for bone-resorption and interleukin 1-like activity. Five cysts synthesised a non-dialysable bone resorbing factor with significant interleukin 1-like activity. One specimen thought to be a cyst with little interleukin 1 activity proved to be antral lining. The results indicate that interleukin 1 may play an important role in cyst expansion by its direct effects on fibroblast proliferation and bone resorption and by stimulating prostaglandin synthesis in stromal fibroblasts of the cyst capsule.

Characteristics of collagenase in experimental periapical granulomas from the teeth of dogs

Periapical granulomas were induced, with a success rate of about 60% (66 granulomas produced out of 109 roots treated) in mandibular premolars. The average wet weight of the granulomas, 46.1 +/- 34.5 mg (mean +/- SD, n = 22), was sufficient to allow individual specimens to be used for most of the biochemical analyses. High collagenase activity was extracted directly from the granulomas with 4 M urea solution. The enzyme was a typical animal collagenase (EC 3.4.24.7) which clove native collagen molecules into three-quarter (alpha A) and one-quarter (alpha B) length fragments. The collagenase was activated by 1 mM p-aminophenylmercuric acetate. This activated enzyme broke down collagen I rather than collagen III preferentially, which is similar to the activity of human polymorphonuclear leucocyte collagenase. The molecular weights of the latent and activated collagenases were 67 and 49 K, respectively.

Enhancement of human dental cyst PGI2 formation by platelet derived growth factor and its role in cyst growth and bone resorption

Various prostaglandins, particularly PGE2 and PGI2, appear to play a major role in osteolytic processes. Radiochromatographic studies have demonstrated that 6-oxo-PGF1-alpha is a major product of exogenously added arachidonic acid in human dental cysts. As platelets may also act as inflammatory cells, platelet-derived growth factor might also have a PGI2-stimulating influence in such cysts. Eleven human dental cysts were examined by a radioimmunoassay and bioassay which can show PGI2 synthesis in human dental cysts without addition of PDGF. Incremental PDGF addition caused a highly significant increase in the rate of PGI2 synthesis. PGDF thus stimulates PGI2 synthesis in chronic inflammatory processes in vitro and may thereby elicit or accelerate osteolysis.

Stimulation of bone resorption by lipoxygenase metabolites of arachidonic acid

We have studied the effect of leukotrienes, (LT): B4, C4, D4 and E4 and the hydroxyeicosatetraenoic acids (HETEs) 5-HETE and 12-HETE on bone resorption in vitro. Resorption was measured by colorimetric assay of calcium released from neonatal mouse calvaria maintained in organ culture for 72h. All the LTs and HETEs stimulated bone resorption, with optimum responses at picomolar or nanomolar concentrations. The responses were biphasic, with a decreasing effect at higher concentrations. In contrast, prostaglandin E2 (PGE2) stimulated resorption only at 10nM and above. Indomethacin partially inhibited resorption by LTB4, LTC4 and LTD4, but did not affect resorption stimulated by LTE4, 5-HETE and 12-HETE. These results indicate that lipoxygenase products of arachidonic acid are highly potent bone resorbing factors and may play an important role in the localised bone loss associated with inflammatory lesions.

Macromolecular osteolytic factor synthesised by squamous carcinoma cell lines from the head and neck in vitro is interleukin 1

Three human cell lines derived from oro-pharyngeal squamous cell carcinomas of the head were investigated for bone-resorbing activity in vitro. Culture media from all three spontaneously produced a non-dialysable osteolytic factor with activity in three in vitro assays for interleukin 1 (IL1), viz. the lymphocyte activating factor (LAF) assay, stimulation of collagenase synthesis by articular chondrocytes, and stimulation of prostaglandin E2 synthesis by fibroblasts. Addition of anti-human IL1 antibody to the culture media abolished all the bone-resorbing activity. Fractionation of the cell culture media by high performance liquid chromatography (HPLC) showed a single peak of activity in the chondrocyte assay with an apparent mol.wt of 15-17,000. This co-eluted with activity in a preparation of IL1 from rat peritoneal macrophage cultures. These results indicate that IL1 is responsible for the prostaglandin-independent bone resorbing activity synthesised by these cells in vitro, and may contribute to the bone destruction associated with the tumour.

Prostaglandin synthesis in the pathogenesis of fronto-ethmoidal mucoceles

The fronto-ethmoidal mucocele is a rare condition capable of expansion and erosion of bone. Its etiology is attributed to obstruction of the fronto-nasal duct and inflammation. To elucidate the role of inflammation, mucocele fragments and fibroblasts cultured from them were examined in vitro to assess prostaglandin E2 synthesis. The cultured fibroblasts when stimulated with mononuclear cell culture supernatant produced significant levels of prostaglandin E2 and collagenase, compared with normal frontal sinus mucosa fibroblasts removed at craniotomy. These significantly elevated mucocele levels of prostaglandin E2 (p = less than 0.001) suggest that lining fibroblasts are a major source of bone-resorbing factors, acting under the stimulus of lymphocytes and monocytes and which operate at the mucocele-bone interface, facilitating expansion. This situation closely parallels that already established in odontogenic cysts.

Effect of effervescent buffered aspirin on prostaglandin synthesis by human gingival fibroblasts

Cultured human gingival fibroblasts were incubated with 14C-arachidonic acid (AA) at 37 degrees C for 2 hours. The metabolites formed were extracted from the cell-free medium in methanol, separated and identified by thin layer chromatography, using two solvent systems that allowed resolution of cyclooxygenase and lipoxygenase products. The predominant cyclooxygenase products were PGE2 and 6-keto-PGF1 alpha. PGA2, PGF2 alpha, PGD2, 15-keto-PGE2, TXB2 were also detected in smaller amounts. No detectable radioactivity corresponding to lipoxygenase products 5-HETE, 12-HETE, and 15-HETE was found. Incubation of fibroblasts with effervescent buffered aspirin (EBA) (.02%, .04%, .06%), or sodium bicarbonate, citric acid and aspirin, individually, (in concentrations equivalent to those present in EBA) resulted in stimulation of synthesis of PGs except PGE2 which was inhibited by EBA and aspirin.

Immunohistochemical detection of 6-oxo-PGF1 alpha and PGE2 in radicular cysts

Prostaglandin synthesis in the wall of radicular cysts was determined by immunohistochemistry and radiothinlayer chromatography. PGE2 is predominantly produced by plasma cells and histiocytic elements, whereas much less is synthesized by fibroblasts and endothelial cells as estimated using immunohistochemistry. 6-oxo-PGF1 alpha, however, was primarily found to be generated by endothelial cells and fibroblasts; only small amounts seem to be derived from histiocytic elements and plasma cells. The response of the cystic epithelium to anti-PGE2 and anti-6-oxo-PGF1 alpha antibodies was negative or showed only minimal staining. It can thus be concluded that the granulation tissue and its cellular components modulating the inflammatory process are the main source of prostaglandin synthesis in the wall of radicular cysts and may therefore be responsible for the resultant osteolytic activity.

Prostaglandin synthesis in dental cysts

The synthesis of prostaglandins by dental squamous cell cysts was studied. Radiothinlayer-chromatography (RTLC) showed C14-labelled arachidonic acid to be converted into the prostaglandins PGE2, 6-oxo-PGF1 alpha, PGF2 alpha and PDG2. In addition, hydroxyfatty acid synthesis in excess of total prostaglandin production was observed. The substances mentioned are thought to be causally involved in the osteolytic activity of dental cysts.