Enamel matrix derivative, inflammation and soft tissue wound healing.

Over 15 years have now passed since enamel matrix derivative (EMD) emerged as an agent capable of periodontal regeneration. Following thorough investigation, evidenced-based clinical application is now established for a multitude of clinical settings to promote regeneration of periodontal hard tissues. Despite the large number of studies and review articles written on this topic, no single review has compiled the influence of EMD on tissue inflammation, an area of research that merits substantial attention in periodontology. The aim of the present review was to gather all studies that deal with the effects of EMD on tissue inflammation with particular interest in the cellular mechanisms involved in inflammation and soft tissue wound healing/resolution. The effects of EMD on monocytes, macrophages, lymphocytes, neutrophils, fibroblasts and endothelial cells were investigated for changes in cell behavior as well as release of inflammatory markers, including interleukins, prostaglandins, tumor necrosis factor-α, matrix metalloproteinases and members of the OPG-RANKL pathway. In summary, studies listed in this review have reported that EMD is able to significantly decrease interleukin-1b and RANKL expression, increase prostaglandin E2 and OPG expression, increase proliferation and migration of T lymphocytes, induce monocyte differentiation, increase bacterial and tissue debris clearance, as well as increase fibroplasias and angiogenesis by inducing endothelial cell proliferation, migration and capillary-like sprout formation. The outcomes from the present review article indicate that EMD is able to affect substantially the inflammatory and healing responses and lay the groundwork for future investigation in the field.

Periodontal healing after application of enamel matrix derivative in surgical supra/infrabony periodontal defects in rats with streptozotocin-induced diabetes.

BACKGROUND AND OBJECTIVE: Epidemiologic and clinical studies have indicated that diabetes is a risk factor for periodontal disease progression and healing. The aim of the present study was to evaluate short-term healing after enamel matrix derivative (EMD) application in combined supra/infrabony periodontal defects in diabetic rats. MATERIAL AND METHODS: Thirty male Wistar rats were initially divided into two groups, one with streptozotocin-induced diabetes and another one with healthy (non-diabetic) animals. Bony defects were surgically created on the mesial root of the first maxillary molars. After root surface planing and EDTA conditioning, EMD was applied to the roots at one side of the maxillae, while those on the contralateral sides were left untreated. Animals were killed 3 wk after surgery, and block sections were prepared for histologic and histomorphometric analysis. RESULTS: There was statistically significant more gingival recession in diabetic animals than in non-diabetic animals. The length of the junctional epithelium was significantly shorter in the EMD-treated sites in both diabetic and normoglycemic rats. Sulcus depth and length of supracrestal soft connective tissue showed no statistically significant differences between groups. In all animals, new bone formation was observed. Although new bone occurred more frequently in healthy animals, the extent of new bone was not significantly different between groups. In none of the teeth, a layer of new cementum was detectable. EMD had no influence on bone or cementum regeneration. Adverse reactions such as excessive inflammation due to bacterial root colonization, ankylosis and bone fractures were exclusively observed in diabetic animals, irrespective of EMD treatment. CONCLUSION: Within the limits of the present study, it can be concluded that periodontal healing was impaired in streptozotocin-induced diabetic rats. EMD had no beneficial effects on new bone and cementum formation during short-term healing in this defect model and could not ameliorate the adverse effects in the systemically compromised animals.

Streptozotocin-induced diabetes in rats diminishes the size of the osteoprogenitor pool in bone marrow.

AIMS: Bone formation is reduced in animals and humans with type 1 diabetes, leading to lower bone mass and inferior osseous healing. Since bone formation greatly depends on the recruitment of osteoblasts from their bone marrow precursors, we tested whether experimental type 1 diabetes in rats diminishes the number of bone marrow osteoprogenitors. METHODS: Diabetes was induced by 65 mg/kg streptozotocin and after 4 weeks, femoral bone marrow cells were extracted and cultured. Tibia and femur were frozen for further analysis. RESULTS: The size of the osteoprogenitor pool in bone marrow of diabetic rats was significantly reduced, as evidenced by (1) lower (~35 %) fraction of adherent stromal cells (at 24h of culture); (2) lower (20-25%) alkaline phosphatase activity at 10 days of culture; and (3) lower (~40 %) mineralized nodule formation at 21 days of culture. Administration of insulin to hyperglycemic rats normalized glycemia and abrogated most of the decline in ex vivo mineralized nodule formation. Apoptotic cells in tibial bone marrow were more numerous in hyperglycemic rats. Also, the levels of malondialdehyde (indicator of oxidative stress) were significantly elevated in bone marrow of diabetic animals. CONCLUSIONS: Experimental type 1 diabetes diminishes the osteoprogenitor population in bone marrow, possibly due to increased apoptosis via Oxidative Stress. Reduced number of osteoprogenitors is likely to impair osteoblastogenesis, bone formation, and bone healing in diabetic animals.

Differential effects of prostaglandin E(2) and enamel matrix derivative on the proliferation of human gingival and dermal fibroblasts and gingival keratinocytes.

BACKGROUND AND OBJECTIVE: Elevated levels of prostaglandins contribute to periodontal destruction but can impair gingival healing by affecting local fibroblasts. Enamel matrix derivative (EMD) has beneficial effects on supporting and gingival tissues. We showed that prostaglandin E(2) (PGE(2) ) inhibits the proliferation of human gingival fibroblasts (hGFs) and that EMD stimulates it. Prostaglandins and EMD may also affect skin healing by targeting dermal fibroblasts (DFs). Thus, we compared the effects of these two agents on the proliferation of hGFs, human gingival keratinocytes (hGKs) and hDFs. MATERIAL AND METHODS: Cells from healthy human gingiva or skin were treated with PGE(2) and/or EMD, and proliferation was assessed by measuring cell number and DNA synthesis. RESULTS: In hGFs, PGE(2) (1 µm) inhibited proliferation while EMD stimulated it. When present together, EMD abolished the PGE(2) -induced inhibition. Serum increased (by a factor of 10) the amount of phosphorylated extracellular signal-regulated kinase (p-ERK), PGE(2) reduced it (by 70-80%) and EMD restored it when present with PGE(2). Prostaglandin E(2) stimulated cAMP production in hGFs while serum or EMD did not. Enamel matrix derivative stimulated hDF proliferation, but the inhibitory effect of PGE(2) was milder than with hGFs. When present together, EMD abolished the PGE(2) -induced inhibition. Enamel matrix derivative inhibited the proliferation of primary hGKs, but PGE(2) had no effect. Finally, we found that hDFs contained about five times less prostaglandin EP(2) receptor mRNA than hGFs, while hGKs contained none. CONCLUSION: Prostaglandin E(2) inhibits and EMD stimulates hGF proliferation via distinct pathways. The different sensitivities of hDFs and hGKs to PGE(2) can be explained by the levels of EP(2) expression.

Enamel matrix derivative induces the expression of tissue inhibitor of matrix metalloproteinase-3 in human gingival fibroblasts via extracellular signal-regulated kinase.

BACKGROUND AND OBJECTIVE: Periodontal disease is characterized by increased expression and activity of matrix metalloproteinases (MMPs) and insufficient expression/activity of their inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). This altered MMP-TIMP balance results in progressive destruction of gingival and periodontal extracellular matrix. Enamel matrix derivative (EMD), clinically used for periodontal regeneration in a device called Emdogain, has been suggested to enhance gingival healing following periodontal procedures in humans. We previously showed that EMD increases the proliferation of human and rat gingival fibroblasts and protects them from tumor necrosis factor-induced apoptosis. In the present study, the modulation of MMP and TIMP expression by EMD was investigated. MATERIAL AND METHODS: Primary human gingival fibroblasts were treated in vitro with tumor necrosis factor, EMD or both in serum-free conditions, and RNA was analyzed with an extracellular matrix-focused microarray and quantitative real-time polymerase chain reaction. RESULTS: Microarray analysis showed detectable expression of MMP-1, MMP-2, MMP-3, MMP-7 and MMP-13, as well as TIMP-1 and TIMP-3 in untreated cells. There was no apparent regulation of the expression of MMP-2, MMP-7, MMP-13 and TIMP-1 by either tumor necrosis factor or EMD. In contrast, tumor necrosis factor significantly increased MMP-1 expression, and EMD reduced it when both agents were present. Also, EMD significantly induced TIMP-3 expression, an effect which was dependent on activation of extracellular signal-regulated kinase 1/2, since it was totally abolished by a selective extracellular signal-regulated kinase pathway inhibitor. CONCLUSION: These data suggest that EMD may affect gingival health by ways other than cell proliferation/survival, i.e. by stimulation of TIMP-3 production, which could improve the MMP-TIMP balance in gingival tissue and curb extracellular matrix destruction.

EGFR in Enamel Matrix Derivative-induced gingival fibroblast mitogenesis.

We previously reported that EMD (Enamel Matrix Derivative) induces proliferation of human gingival fibroblasts via activation of Extracellular Regulated Kinase (ERK), and this study assessed the possible mediatory role of EGFR (Epidermal Growth Factor Receptor) in this effect. Treatment of gingival fibroblasts with EMD resulted in tyrosine phosphorylation of the EGFR, as assessed by immunoblotting and ELISA, while EMD-induced ERK activation and thymidine incorporation were markedly inhibited (approximately 40-50%) by a specific EGFR tyrosine kinase inhibitor. Using appropriate inhibitors, we established that EMD-induced EGFR activation is largely due to shedding of HB-EGF (Heparin-binding EGF) from the cell membrane via a metalloproteinase-mediated process. Finally, the addition of PP1, a Src family inhibitor, abrogated both EGFR phosphorylation and ERK activation. Taken together, these results indicate that, at least in human gingival fibroblasts, EMD-induced ERK activation and proliferation are partially due to a Src-dependent, metalloproteinase-mediated transactivation of EGFR.

Enamel, dentine and pulp in talon primary maxillary central incisors: a histomorphometric study.

AIM: To examine whether a talon incisor has an abnormal shape due to excess of dental hard tissues or pulp. METHODS: Two bilateral primary maxillary central incisors with talon cusp and a supernumerary mesiodens were removed from a 6-year-old boy. Histologically, 7 undecalcified cross sections (70 microm) were harvested from each talon tooth and from two regular primary central incisors of another child. Microradiographs of the sections were prepared and examined for enamel width, dentin width, pulp tissue area, and crown size (mesio-distal, labio-palatal) using Image Analysis. RESULTS: No association to other developmental disorders was observed. The mean width of the enamel and dentin was similar in the talon and the regular incisors (difference 7.5% and 2.4%, respectively). The pulp area was greater in the talon teeth (37.4%). The latter had an effect on the increase in the mesio-distal and labio-palatal dimensions of the talon teeth (17.6% and 23.9%, respectively). CONCLUSIONS: The fact that the talon cusp has normal enamel and dentin layers with a substantial enlarged pulp tissue suggests that similar developmental anomalies occur during tooth morphodifferentiation as in taurodontism and dens evagintus of premolars.

Enamel matrix derivative protects human gingival fibroblasts from TNF-induced apoptosis by inhibiting caspase activation.

Emdogain, a formulation of enamel matrix derivative (EMD), is used clinically for regeneration of the periodontium (tooth supporting tissues), but the molecular mechanisms of its action have not been elucidated. Several clinical studies suggested that EMD may also improve gingival healing after periodontal surgery and thus affect the fate of gingival fibroblasts (GFs). Since these cells are targets for local inflammatory mediators such as TNF, a pro-apoptotic cytokine, during the course of periodontal disease, we tested whether EMD protects human GFs (hGFs) from TNF-induced cytotoxicity. Quiescent primary hGFs were challenged with TNF (10-100 ng/ml) with or without EMD (100 microg/ml) pretreatment. Cell viability was assessed by neutral red staining, cell death by LDH release and apoptosis by caspase activity. Signaling pathways were evaluated by Western blotting and pharmacological inhibitors. TNF induced classical signs of apoptosis in hGFs, including typical cellular morphology and increased caspase activity. TNF-induced cytotoxicity was entirely caspase-dependent. Pretreatment (4-24 h) with EMD dramatically inhibited the activation of initiator and executioner caspases and enhanced hGF survival. Although TNF induced the activation of p38 MAPK, JNK, ERK and PI-3K signaling, these pathways were not crucial for EMD protection of hGFs. However, EMD increased the levels of c-FLIP(L), an anti-apoptotic protein located upstream of caspase activation. These data demonstrate, for the first time, that EMD protects hGFs from inflammatory cytokines and, together with our recent reports that EMD stimulates rat and human GF proliferation, could help explain the mechanisms whereby in vivo use of EMD promotes gingival healing.

Enamel matrix derivative stimulates human gingival fibroblast proliferation via ERK.

Emdogain, a formulation of Enamel Matrix Proteins, is used clinically for periodontal regeneration to stimulate PDL (periodontal ligament), cementum, and bone formation. Its effects on gingival fibroblasts and tissue have not been thoroughly studied. Therefore, we investigated the mechanisms by which Emdogain affects the cell cycle of human gingival fibroblasts. Without serum, Emdogain (50 microg/mL) induced human gingival fibroblast entry into the S phase and DNA synthesis, but not completion of the cell cycle. With low serum concentrations (0.2-0.5%), Emdogain synergistically induced completion of the cell cycle, resulting in increased cell numbers. The mitogenic response to Emdogain depended on Extracellular Regulated Kinase (ERK) activation, which occurred in two waves, peaking after 15 min and 4 to 6 hrs, since it was abolished by U0126, a specific MAPK inhibitor. Inhibition of the second wave was sufficient to abrogate mitogenesis. This study characterized the mitogenic effect of Emdogain on primary human gingival fibroblasts, its cooperation with serum growth factors, and the key mediatory role of the ERK cascade.

Prostaglandin E2 (PGE2) increases the number of rat bone marrow osteogenic stromal cells (BMSC) via binding the EP4 receptor, activating sphingosine kinase and inhibiting caspase activity.

Prostaglandin E(2) (PGE(2)) is bone-anabolic, i.e. stimulates bone formation and increases bone mass. In this study, we explored possible intracellular mechanisms of its increase of osteogenic cells in rat bone marrow. Adherent rat bone marrow cells were counted after 12-48 h or cultured for 21 days and mineralized nodules were counted. Also, apoptosis of marrow cells was measured after in vivo PGE(2) injection. PGE(2) (100 nM) increased 2-3 fold the number of adherent BMSC, an effect which was mediated via binding the EP(4) receptor since it was mimicked by forskolin and 11-deoxy-prostaglandin E(1) (PGE(1)) and was blocked by DDA and L-161982 (EP(4) antagonist). PGE(2) stimulated sphingosine kinase (SPK) activity since its effects were blocked by DMS (SPK inhibitor) and mimicked by SPP (SPK product). PGE(2) reduced the activity of caspase-3 and -8 in BMSC and their inhibitors increased BMSC number and nodule formation. In vivo, PGE(2) prevented the increase in the apoptosis of bone marrow cells caused by indomethacin. We propose that PGE(2) exerts an anti-apoptotic effect on BMSC, thereby increasing their number and subsequent osteoblastic differentiation. Such an effect could explain how PGE(2) stimulates bone formation in vivo.

[Recommendations for early identification of damage to the skeleton by malignant processes, and for early diagnosis of multiple myeloma]. / Doporucení pro casné rozpoznání postizení skeletu maligním procesem a pro casnou diagnostiku mnohocetného myelomu.

The number of newly diagnosed cases of multiple myeloma in the Czech Republic is about 3-4 per 100 000 persons per year. In the higher age groups, the incidence increases. Multiple myeloma is an illness that reacts well to treatment which can result in periods of remission lasting for years. Some of the patients are even able to return to work. A pre-requisite for successful treatment is early diagnosis and this is usually in the hands of first line physicians. This is the reason why the Czech Myeloma Group, in conjunction with neurologists, orthopedicians and radio diagnosticians has issued the following recommendations for first line physicians containing a more detailed description of the symptoms and the diagnostic pitfalls of the disease. This disease reminds a chameleon for the variety of its symptoms. For the sake of clarification, we shall divide multiple myeloma symptoms into five points, each of which is reason enough to warrant an examination to confirm or rule out a malignant cause of health problems (a negative result does not automatically mean exclusion). If any of the recommended examinations results positive, the diagnostic process must be continued, in which case a general practitioner refers the patient to a specialist health centre. Observing these recommendations should minimize the number of cases of late diagnosis. 1. Bone destruction symptoms. - Unexplained backache for more than one month in any part of spine even without nerve root irritability or without pain in other part of skeleton (ribs, hips, or long bones). - Pain at the beginning of myeloma disease is very similar to benigne common discopathy, however the intensity of backache is decreasing within one months in benigne disease. In the case of malignant process the intensity of bone pain is steadily increasing. - Immediate imaging and laboratory investigation are indicated by resting and night pain in spinal column or in any part of skeleton. - Backache with the sign of spinal cord or nerve compression should be sent for immediate X Ray, and focussed CT/MRI followed by acute surgery if needed. - Osteoporosis especially in men and premenopausal women. 2. Features of changed immunity or bone marrow function. Persistent and recurrent infection, typical is normochromic anaemia, with leucopenia and trombocytopenia. 3. Raised erythrocyte sedimentation rate even increase concentration of total plasma protein. 4. Impaired renal function. Increased level of creatinin or proteinuria, nephrotic syndrome with bilateral legs oedema. 5. Hypercalcemia with typical clinical symptoms (polyuria with dehydratation, constipation, nausea, low level conscience, coma). Every one from these points has to be reason for general medical doctor to start battery of tests: -X-ray of bones focused to painful area (mandatory before physiotherapy, local anaesthesia or other empiric therapy). If plain X-ray does not elucidate pain and symptoms are lasting more than one month, please consider all circumstances and results from laboratory investigation. This patient needs referral to the centre with MRI/CT facilities (CT or MRI is necessary investigation in case of nerve root or spine compression). -Investigation of erythrocyte sedimantion rate (high level of sedimentation of erythrocyte can indicate multiple myeloma). -Full blood count. -Basic biochemical investigation serum and urine: serum urea, creatinin, ionts including calcium, total protein, and albumin CRP (high concentration of total protein indicates myeloma, low level of albumin indicates general pathological process, similary increased concentration of fibrinogen, impaired renal function indicates myeloma kidney, however hypercalcemia is typical for highly aggressive myeloma). -Quantitative screening for IgG, IgM and IgA in serum (isolated raised level one of immunoglobulin with decreased level of the others indicates myeloma). -Common electrophoresis of serum is able to detect monoclonal immunoglobulin level at few gramm concentration. If all the laboratory investigation are in normal level the possibility that the current problems are multiple myeloma origine is smaller, but it does not exclude one of rare variant--non secretory myeloma (undifferentiated plasmocyt lost characteristic feature to produce monoclonal immunoglobulin). If any of tests indicate the possibility of myeloma, patient require urgent specialist referral to department with possibility to make diagnosis of malignant myeloma.

In vitro effects of enamel matrix proteins on rat bone marrow cells and gingival fibroblasts.

Emdogain (EMD), a formulation of Enamel Matrix Proteins (EMP), is used clinically for periodontal regeneration, where it stimulates cementum formation and promotes gingival healing. In this study, we investigated the in vitro effects of EMD on rat bone marrow stromal cells (BMSC) and gingival fibroblasts (GF). EMD (at 25 micro g/mL) increased the osteogenic capacity of bone marrow, as evidenced by approximately three-fold increase in BMSC cell number and approximately two-fold increase in alkaline phosphatase (ALP) activity and mineralized nodule formation. The presence of EMD in the initial stages (first 48 hrs) of the culture was crucial for this effect. In contrast, EMD did not induce osteoblastic differentiation of GF (evidenced by lack of mineralization or ALP activity) but increased up to two-fold both their number and the amount of matrix produced. These in vitro data on BMSC and GF could explain the promotive effect of EMD on bone formation and connective tissue regeneration, respectively.

A selective EP4 receptor antagonist abrogates the stimulation of osteoblast recruitment from bone marrow stromal cells by prostaglandin E2 in vivo and in vitro.

Recent evidence indicates that systemic administration of PGE2 increases bone formation and bone mass via activation of the EP4 receptor. Previously, we demonstrated that osteoblastic recruitment from rat bone marrow stromal cells (BMSC) is a major mechanism for the anabolic effect of PGE2. In this study, we used a selective EP4 antagonist to test if the stimulation of osteoblast differentiation from rat BMSC in vitro and in vivo involves the EP4 receptor. In vitro, PGE2 (100 nM) increased nodule formation and alkaline phosphatase (ALP) activity in cultures of rat BMSC 1.5- to 2-fold. These effects were abolished by the EP4 antagonist at 10(-6) M but not 10(-9) M. Furthermore, PGE2 increased the number of surviving adherent BMSC by approximately 225% and the EP4 antagonist prevented this effect as well. The antagonist had no effect on basal levels of nodule formation and adherent cell number. In vivo, daily systemic administration of PGE2 at 6 mg/kg for 2 weeks increased cancellous bone area (by approximately 50%) and increased nodule formation (measured as mineralized area) in ex vivo stromal cultures by approximately 50%. Pre-administration of the EP4 antagonist at 10 mg/kg abrogated both the increase in bone mass as well as the increase in nodule formation. These data indicate that PGE2 stimulates osteoblastic commitment of BMSC via activation of the EP4 receptor.

Involvement of the skeletal GH-IGF system in an experimental model of diabetes-induced growth retardation.

Uncontrolled diabetes is associated with growth retardation. We investigated the effect of insulin-dependent diabetes on animal growth and IGF-I gene expression in the epiphyseal growth plate region of the long bones. We also studied the effect of GH administration on somatic growth in the diabetic state. Streptozotocin (STZ)-injected diabetic rats had a decreased somatic growth rate in comparison to controls. GH administration (2.5 U/kg day) in the diabetic animals (DGH group) prevented this decrease. Serum IGF-I levels were decreased in both diabetic and DGH animals. Within 72 h from diabetes onset, IGF-I mRNA levels in epiphyseal growth plate homogenates decreased whereas IGF-I receptor mRNA levels increased in diabetic animals. The decrease in IGF-I mRNA transcript levels was localized to the metaphyseal region by in situ hybridization. We conclude that in the STZ-induced diabetic state, the reduction in linear growth is associated with a parallel decrease in IGF-I gene expression at the epiphyseal growth plate area. Diabetic growth retardation can be reversed with GH administration, which does not reconstitute serum IGF-I levels. Therefore, we speculate that GH in this model may act locally through the skeletal GH-IGF-I system.

Inhibition of cyclo-oxigenase-2 activity does not abolish the anabolic effect of prostaglandin E2 in vivo or in vitro.

It was previously reported that the expression of cyclo-oxigenase-2 (COX-2) is induced by prostaglandin E(2) (PGE(2)) in vitro in an osteogenic cell line and organ culture, suggesting an autoamplification mechanism. In this study, we first tested whether this phenomenon also occurs in bone tissue in vivo and found that a single anabolic dose of PGE(2) (5 mg/kg) induced (between 30 and 120 min) in rat tibiae, an increase in the mRNA level of COX-2 (2.5- to 9-fold) but not that of COX-1. Secondly, to test whether COX-2 activity in generating endogenous prostaglandins (PGs) is required for the in vivo anabolic properties of PGE(2), young male rats were injected daily with either vehicle (8% ethanol) or 5 mg/kg PGE(2) for 21 days. PGE(2)-injected rats received, 45 min prior to PGE(2), either dimethyl sulphoxide (as vehicle) or one of two doses of NS-398, a selective COX-2 inhibitor: a low dose (3 mg/kg) or a high dose (10 mg/kg). PGE(2) increased bone formation (measured as cancellous mineralizing surface, mineral apposition rate and bone formation rate) and bone mass (measured as cancellous bone area and surface and cortical width). None of these increases was suppressed by pre-administration of NS-398. In contrast, the high dose of NS-398 effectively suppressed an increase in rat hind-paw volume induced by a local carrageenan injection. Furthermore, since COX-2 inactivation may affect PG receptor expression, we found that pre-administration of NS-398 did not abolish the induction in EP(4) receptor mRNA levels, caused by PGE(2) in rat bone tissue. For in vitro testing, rat femoral bone marrow stromal cell cultures were initiated and were incubated in the absence or presence of PGE(2) at 100 nM (as an inducer) and with increasing concentrations of NS-398 (10(-8) M to 10(-5) M) for 21 days, after which time mineralized (Von-Kossa positive) nodules were counted. PGE(2) increased nodule formation as previously reported; however, NS-398 reduced nodule formation in both control and PGE(2)-treated cultures to the same extent. We conclude that while the level of COX-2 mRNA is increased in vivo by administration of PGE(2), inhibition of its activity (i.e. generation of endogenous PGs) does not abolish the anabolic effect of PGE(2).

South Asian ethnicity and material deprivation increase the risk of Epstein-Barr virus infection in childhood Hodgkin's disease.

In order to further define the factors associated with the observed variations in the Epstein-Barr virus-positive rate in childhood Hodgkin's disease, we have studied the effect of material deprivation (measured by the Townsend score) and ethnic origin on the frequency of Epstein-Barr virus-positivity in 55 cases of childhood Hodgkin's disease, diagnosed between 1981 and 1999, from a multi-ethnic region of the United Kingdom. Epstein-Barr virus status was determined by immunohistochemistry for the Epstein-Barr virus-encoded latent membrane protein-1. 62% of cases were Epstein-Barr virus-positive. Ethnic group was the strongest predictor of Epstein-Barr virus-positivity, with South Asians having a more than 20-fold risk of being Epstein-Barr virus-positive compared with non-South Asians. An increased risk was still present after adjusting for deprivation. Townsend scores were significantly higher (indicating more deprivation) in the Epstein-Barr virus-positive group, particularly in males. The relative risk of Epstein-Barr virus-positivity showed a gradient with increasing Townsend score; the risk being 7-times higher in the most deprived quartile compared with the least deprived group. Although the association between Townsend score and Epstein-Barr virus-positivity was reduced after adjusting for ethnic group, the risk of Epstein-Barr virus-positivity was still 3-times higher in the most deprived compared with the least deprived quartile. In addition, cases having 2 or more siblings were 5-times as likely to be Epstein-Barr virus-positive as those from smaller families. These results provide the first evidence of a strong association between Epstein-Barr virus-positive Hodgkin's disease and South Asian children from the United Kingdom. In addition, deprivation may increase the likelihood of Epstein-Barr virus-positive disease independently of ethnicity.

Expression of the prostaglandin E(2) (PGE(2)) receptor subtype EP(4) and its regulation by PGE(2) in osteoblastic cell lines and adult rat bone tissue.

Prostaglandins E (especially PGE(2)) stimulate bone formation and increase bone mass in several species including man. The mechanism for this effect, the target cells, and the receptors involved are not known. Specific cell-surface receptors for PGE(2) (EP(1-4)) have been cloned and characterized. EP(4) was reported to be the major receptor in embryonic and neonatal bone tissue in mice, especially in preosteoblasts; however, no data are available regarding its expression in adult bone. This study examines the expression of EP(4) in bone tissue of young adult rats, in which PGE(2) is markedly anabolic, and in various osteoblastic cell lines. Using northern blot analysis, we found that osteoblastic cell lines RCT-1, RCT-3, TRAB-11, and RP-1, primary osteoblastic cells harvested from fetal rat calvaria, as well as tibiae and calvariae of 5-week-old rats express 3.8 kb EP(4) messenger RNA (mRNA). Treatment of periosteal cells (RP-1) in vitro with 10(-6) mol/L PGE(2) increased the levels of both EP(4) mRNA and EP(4) protein, peaking at 1-2 h. Similarly, systemic administration of an anabolic dose of PGE(2) (3-6 mg/kg) to young adult rats upregulated the expression of EP(4) in the tibia and calvaria, also peaking at 1-2 h. Using in situ hybridization, we found increased expression of EP(4) in bone marrow cells of the tibial metaphysis in response to systemic PGE(2) treatment. The preosteoblastic nature of these EP(4)-expressing cells was suggested by the fact that dexamethasone-treated bone marrow stromal cells in culture express EP(4) mRNA, which is upregulated by PGE(2). Northern blot analysis failed to detect both basal and PGE(2)-induced EP(2) mRNA in the bone samples or cell lines tested. Taken together, these data implicate EP(4) as the major cyclic AMP-related PGE(2) receptor subtype expressed in bone tissue and osteoblastic cells and indicate that this receptor is upregulated by its ligand, PGE(2).

Systemic prostaglandin E2 increases cancellous bone formation and mass in aging rats and stimulates their bone marrow osteogenic capacity in vivo and in vitro.

Prostaglandin E(2) (PGE(2)) has been shown to exert a bone anabolic effect in young and adult rats. In this study we tested whether it possesses a similar effect on bone formation and bone mass in aging rats. Fifteen-month-old rats were injected daily with either PGE(2) at 5 mg/kg or vehicle for 14 days. PGE(2) treatment stimulated the rate of cancellous bone formation (a approximately 5.5-fold increase in bone formation rate), measured by the incorporation of calcein into bone-forming surfaces at the tibial proximal metaphysis. This effect resulted in increased cancellous bone area (+54%) at the same site. Since PGE(2) treatment resulted in a much higher proportion of bone surface undergoing bone formation and thus lined with osteoblasts, we tested the hypothesis that PGE(2) stimulates osteoblast differentiation from bone marrow precursor cells both in vivo and in vitro. We found that ex vivo cultures of bone marrow stromal cells from rats injected for 2 weeks with PGE(2) at 5 mg/kg per day yielded more ( approximately 4-fold) mineralized nodules and exhibited a greater (by 30-40%) alkaline phosphatase activity compared with cultures from vehicle-injected rats, attesting to a stimulation of osteoblastic differentiation by PGE(2). We also compared the osteogenic capacity of bone marrow from aging (15-month-old) versus young (5-week-old) rats and its regulation by PGE(2) in vitro. Bone marrow stromal cell cultures from aging rats exhibited a greatly diminished osteogenic capacity, reflected in reduced nodule formation ( approximately 6% of young animals) and lower alkaline phosphatase activity ( approximately 60% of young animals). However, these parameters could be stimulated in both groups of animals by incubation with 10-100 nM PGE(2). The magnitude of this stimulation was greater in cultures from aging rats (+550% vs +70% in nodule formation of aging compared with young rats). In conclusion, we demonstrate here that PGE(2) exerts a bone anabolic effect in aging rats, similar to the effect we and others have reported in young, growing rats. The PGE(2)-stimulated bone formation, which augments bone mass, most likely results from recruitment of osteoblasts from their bone marrow stromal precursors.

Restrained chondrocyte proliferation and maturation with abnormal growth plate vascularization and ossification in human FGFR-3(G380R) transgenic mice.

Achondroplasia, the most common genetic form of human dwarfism, results from a point mutation (G380R) in the gene for fibroblast growth factor receptor 3 (FGFR-3). Heterozygotes for the mutation share disproportionate, proximal shortening of the limbs, mid-face hypoplasia and relative macrocephaly due to a failure in endochondral ossification. Here we have generated transgenic mice expressing the human mutant FGFR-3 under the transcriptional control of the mouse gene. Mice that are hemizygous for the mutant human gene display disproportionate dwarfism with skeletal phenotypes remarkably similar to those of human achondroplasia. Mice that are homozygous for the transgene suffer from a profound delay in skeletal development and die at birth, similar in that respect to humans homozygous for the achondroplasia mutant gene. Microscopic analysis of long bones demonstrates growth plate morphology compatible with that of human achondroplasia cases, sharing endochondral growth inhibition with restrained chondrocyte proliferation and maturation, penetration of ossification tufts and aberrant vascularization.

The anabolic effect of PGE2 in rat bone marrow cultures is mediated via the EP4 receptor subtype.

Prostaglandin E2 (PGE2) is an anabolic agent in vivo that stimulates bone formation by recruiting osteoblasts from bone marrow precursors. To understand which of the known PGE2 receptors (EP1-4) is involved in this process, we tested the effect of PGE2 and various EP agonists and/or antagonists on osteoblastic differentiation in cultures of bone marrow cells by counting bone nodules and measuring alkaline phosphatase activity. PGE2 increased both parameters, peaking at 100 nM, an effect that was mimicked by forskolin and was abolished by 2',3'-dideoxyadenosine (an adenylate cyclase inhibitor) and was thus cAMP dependent, pointing to the involvement of EP2 or EP4. Consistently, 17-phenyl-omega-trinor PGE2 (EP1 agonist) and sulprostone (EP3/EP1 agonist) lacked any anabolic activity. Furthermore, butaprost (EP2 agonist) was inactive, 11-deoxy-PGE1 (EP4/EP2 agonist) was as effective as PGE2, and the PGE2 effect was abolished dose dependently by the selective EP4 antagonist AH-23848B, suggesting the involvement of EP4. We also found that PGE2 increased nodule formation and AP activity when added for the initial attachment period of 24 h only. Thus this study shows that PGE2 stimulates osteoblastic differentiation in bone marrow cultures, probably by activating the EP4 receptor, and that this effect may involve recruitment of noncommitted (nonadherent) osteogenic precursors, in agreement with its suggested mode of operation in vivo.