Mitigating bias in estimating epidemic severity due to heterogeneity of epidemic onset and data aggregation.

Outbreaks of infectious diseases, such as influenza, are a major societal burden. Mitigation policies during an outbreak or pandemic are guided by the analysis of data of ongoing or preceding epidemics. The reproduction number, R0, defined as the expected number of secondary infections arising from a single individual in a population of susceptibles is critical to epidemiology. For typical compartmental models such as the Susceptible-Infected-Recovered (SIR) R0 represents the severity of an epidemic. It is an estimate of the early-stage growth rate of an epidemic and is an important threshold parameter used to gain insights into the spread or decay of an outbreak. Models typically use incidence counts as indicators of cases within a single large population; however, epidemic data are the result of a hierarchical aggregation, where incidence counts from spatially separated monitoring sites (or sub-regions) are pooled and used to infer R0. Is this aggregation approach valid when the epidemic has different dynamics across the regions monitored? We characterize bias in the estimation of R0 from a merged data set when the epidemics of the sub-regions, used in the merger, exhibit delays in onset. We propose a method to mitigate this bias, and study its efficacy on synthetic data as well as real-world influenza and COVID-19 data.

Respiratory and peripheral muscular ultrasound characteristics in ICU COVID 19 ARDS patients.

PURPOSE: Severe cases of coronavirus disease 2019 develop ARDS requiring admission to the ICU. This study aimed to investigate the ultrasound characteristics of respiratory and peripheral muscles of patients affected by COVID19 who require mechanical ventilation. MATERIALS AND METHODS: This is a prospective observational study. We performed muscle ultrasound at the admission of ICU in 32 intubated patients with ARDS COVID19. The ultrasound was comprehensive of thickness and echogenicity of both parasternal intercostal and diaphragm muscles, and cross-sectional area and echogenicity of the rectus femoris. RESULTS: Patients who survived showed a significantly lower echogenicity score as compared with those who did not survive for both parasternal intercostal muscles. Similarly, the diaphragmatic echogenicity was significantly different between alive or dead patients. There was a significant correlation between right parasternal intercostal or diaphragm echogenicity and the cumulative fluid balance and urine protein output. Similar results were detected for rectus femoris echogenicity. CONCLUSIONS: The early changes detected by echogenicity ultrasound suggest a potential benefit of proactive early therapies designed to preserve respiratory and peripheral muscle architecture to reduce days on MV, although what constitutes a clinically significant change in muscle echogenicity remains unknown.

M-CSF neutralization and egr-1 deficiency prevent ovariectomy-induced bone loss.

Increased stromal cell production of M-CSF, an event caused by enhanced phosphorylation of the nuclear protein Egr-1, is central to the mechanism by which estrogen (E2) deficiency upregulates osteoclast (OC) formation. However, the contribution of enhanced M-CSF production to the bone loss induced by E2 deficiency remains to be determined. We found that treatment with an Ab that neutralizes M-CSF in vivo completely prevents the rise in OC number, the increase in bone resorption, and the resulting bone loss induced by ovariectomy (ovx). We also found that adult, intact Egr-1-deficient mice, a strain characterized by maximally stimulated stromal cell production of M-CSF, exhibit increased bone resorption and decreased bone mass. In these mice, treatment with anti-M-CSF Ab restored normal levels of bone resorption, thus confirming that increased M-CSF production accounts for the remodeling abnormalities of Egr-1-deficient mice. Consistent with the failure of ovx to further increase M-CSF production in Egr-1-deficient mice, ovx neither increased bone resorption further, nor caused bone loss in these animals. In summary, the data demonstrate that E2 deficiency induces M-CSF production via an Egr-1-dependent mechanism that is central to the pathogenesis of ovx-induced bone loss. Thus, Egr-1 and M-CSF are critical mediators of the bone sparing effects of E2 in vivo.

Estrogen decreases TNF gene expression by blocking JNK activity and the resulting production of c-Jun and JunD.

Central to the bone-sparing effect of estrogen (E(2)) is its ability to block the monocytic production of the osteoclastogenic cytokine TNF-alpha (TNF). However, the mechanism by which E(2) downregulates TNF production is presently unknown. Transient transfection studies in HeLa cells, an E(2) receptor-negative line, suggest that E(2) inhibits TNF gene expression through an effect mediated by estrogen receptor beta (ERbeta). We also report that in RAW 264.7 cells, an E(2) receptor-positive murine monocytic line, E(2) downregulates cytokine-induced TNF gene expression by decreasing the activity of the Jun NH(2)-terminal kinase (JNK). The resulting diminished phosphorylation of c-Jun and JunD at their NH(2)-termini decreases the ability of these nuclear proteins to autostimulate the expression of the c-Jun and JunD genes, thus leading to lower production of c-Jun and JunD. The consequent decrease in the nuclear levels of c-Jun and JunD leads to diminished binding of c-Jun/c-Fos and JunD/c-Fos heterodimers to the AP-1 consensus sequence in the TNF promoter and, thus, to decreased transactivation of the TNF gene.

Estrogen deficiency induces bone loss by enhancing T-cell production of TNF-alpha.

Estrogen deficiency induces bone loss by upregulating osteoclastogenesis by mechanisms not completely defined. We found that ovariectomy-enhanced T-cell production of TNF-alpha, which, acting through the TNF-alpha receptor p55, augments macrophage colony-stimulating factor-induced (M-CSF-induced) and RANKL-induced osteoclastogenesis. Ovariectomy failed to induce bone loss, stimulate bone resorption, or increase M-CSF- and RANKL-dependent osteoclastogenesis in T-cell deficient mice, establishing T cells as essential mediators of the bone-wasting effects of estrogen deficiency in vivo. These findings demonstrate that the ability of estrogen to target T cells, suppressing their production of TNF-alpha, is a key mechanism by which estrogen prevents osteoclastic bone resorption and bone loss.

[Vaginal intraepithelial neoplasia and human papillomavirus infection: a report of 75 cases]. / La neoplasia intraepiteliale vaginale e l'infezione da virus del papilloma umano. Un resoconto di 75 casi.

AIM: Vaginal intraepithelial neoplasia (VaIN) is an uncommon and poorly understood disease. Risk factors other than human papillomavirus (HPV) infection could be linked to the onset and evolution of some VaIN. METHODS: In this paper, the results achieved from the analysis of 75 patients with VaIN are reported. From these cases, women with HIV, previous hysterectomy, autoimmune diseases and radio- and chemotherapy have been excluded. Thus, most of these selected cases should be linked to the HPV infection. They have been examined after a distinction between grade and association with coilocytosis. VaIN preferential localization, mean age of patients and manifestation pattern after vaginal colposcopy have then been examined. RESULTS: Although the population size cannot allow evidences, it seems that VaIN with coilocytosis and VaIN I without coilocytosis have preferential localization in the upper third of the vagina. It does not appear that mean age of patients for each grade of VaIN differs significativly, both associated and not associated with coilocytosis. Finally, after vaginal colposcopy, the pattern of VaIN for each grade is absolutely not typical, and it seems that white thin epithelium or negative Lugol area are usually the manifestation of high grades of VaIN too. CONCLUSIONS: These results, if confirmed, could mean that VaIN due to HPV may have a different natural history relating to the site of localization in the vagina and, moreover, that also VaIN of high grade could appear with an innocent vaginal pattern.

T cell activation induces human osteoclast formation via receptor activator of nuclear factor kappaB ligand-dependent and -independent mechanisms.

In unstimulated conditions, osteoclast (OC) formation is regulated by stromal cell production of the key osteoclastogenic factors receptor activator of nuclear factor kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). However, the mechanisms of accelerated osteoclastogenesis and bone loss characteristic of inflammatory conditions are poorly understood but appear to involve T cells. In addition, the mechanism by which OCs arise spontaneously in cultures of peripheral blood mononuclear cells in the absence of stromal cells or added cytokines remains unclear. Using a stromal cell free human osteoclast generating system, we investigated the ability of activated T cells to support osteoclastogenesis. We show that when activated by phytohemagglutinin-P (PHA), T cells (both CD4+ and CD8+) stimulate human OC formation in vitro. Although both soluble M-CSF and RANKL were detected in activated T cell supernatants, the presence of M-CSF was not essential for macrophage survival or RANKL-dependent osteoclast formation, suggesting that other soluble T cell-derived factors were capable of substituting for this cytokine. We also found that saturating concentrations of osteoprotegerin (OPG) failed to neutralize 30% of the observed OC formation and that T cell conditioned medium (CM) could superinduce osteoclastogenesis in cultures of purified monocytes maximally stimulated by RANKL and M-CSF. Together, these data suggest that activated T cells support osteoclastogenesis via RANKL-dependent and -independent mechanisms. Although not relevant for T cell-induced osteoclastogenesis, secretion of soluble M-CSF is a previously undescribed property of activated T cells.

Role of TNF-alpha producing T-cells in bone loss induced by estrogen deficiency.

Many study in literature have suggested a possible role of T cells and tumor necrosis factor-alpha (TNF-alpha) in the pathogenesis of bone loss that occurs in pathological conditions, such as systemic inflammatory diseases; the molecular bases through which this phenomenon occurs and the relevance of this mechanism also in estrogen deficiency induced bone loss remain unclear. In our study we observed that TNF-alpha knock-out mice (TNF-/-), as well as transgenic mice without thymus (and therefore without mature T cell), do not lose bone after ovariectomy like observed for mice of normal genetic background (wild type, WT). Moreover, after transfer into athymic mice of T cell isolated from WT ovariectomized animals (and so stimulated by estrogen deficiency to proliferate and to produce TNF-alpha), ovariectomy recovers its ability to induce bone loss; whereas there is no change in bone density after injection into athymic mice of T-cell purified from TNF-/- animals which, even if mature, are unable to produce TNF-alpha. Therefore the presence of TNF-alpha producing T-cell is essential for estrogen deficiency to influence bone metabolism. In the following study of the research group of Prof. Pacifici it has been shown that the increased activation of TNF-alpha producing T-cell in the ovariectomized mice is due to increased INF-gamma levels, resulting from ovariectomy-induced enhanced secretion of IL-12 and IL-18 by macrophages. INF-gamma promotes expression in immunocompetent cells of class II transactivator (CIITA), that, up-regulating expression of the major system of histocompatibility of class II, makes the macrophages more active in antigen presentation to T-cells, which in turn start producing TNF. For the first time an immune mechanism is involved in the pathogenesis of post-menopausal osteoporosis; nevertheless the applicability of these conclusions also in humans remains still to be proved.

[A natural alternative to menopausal hormone replacement therapy. Phytoestrogens]. / Un'alternativa naturale alla terapia ormonale sostitutiva in menopausa.. I fitoestrogeni.

Phytoestrogens are non-steroidal plant molecules whose structure differs from gonadal hormones, but with an estrogen-type bioactivity: they are capable of interacting with estrogen receptors, showing both agonist and antagonist methods of action. The beneficial effects of various classes of phytoestrogens present in nature are now known, but the main isoflavone present in soya, genistein, appears to be particularly effective. Interest in this substance is concentrated in particular on its therapeutic role in menopause. This paper is a review of the main studies published to date on the efficacy of phytoestrogens in reducing the symptoms of menopause. A diet rich in isoflavones is associated with a reduced incidence of vasomotor episodes; the average supplement of genistein is approximately 50 mg/day. After supplementing the diet with phytoestrogens, studies show a reduction in total cholesterol and LDL fraction. This is accompanied by an increase in BMD (Bone mineral density) after taking 90 mg of isoflavones for 6 months. Isoflavones may reduce the risk of developing breast cancer. The data examined confirm the excellent clinical efficacy of supplementing the diet with soy extracts, particularly genistein which is indicated to alleviate both the short-term symptoms of menopause and the long-term effects, although the latter finding requires further subsantiation.

Patients on liver transplantation waiting list with Model for End-Stage Liver Disease score ≥ 30: experience in the Organizzazione Centro Sud Trapianti macro area.

INTRODUCTION: From 2011 a program was developed for liver transplant recipients with Model for End-Stage Liver Disease (MELD) score ≥30. We examined its effectiveness and impact on the other subjects on the waiting list. MATERIALS AND METHODS: We analyzed requests received between January 2011 and May 2012 for the primary pathology, the outcome, the average waiting time, and the origin of the organ. We examined the ordinary waiting list for mortality rates and numbers of transplantations over this period (group A) versus a comparable preceding period (group B). RESULTS: There were 38 requests for 33 patients. Their primary pathologies were cirrhosis associated with viral infection (n = 15), delayed graft failure (DGF; n = 5), biliary cirrhosis (n = 4), hepatocellular carcinoma (HCC; n = 3 including 2 with cirrhosis), cryptogenic cirrhosis (n = 3), postalcoholic cirrhosis (n = 2), metabolic disease (n = 2), and iatrogenic disease (n = 1). Of the requests, 25 were successfully dealt with, whereas 5 requests were temporarily suspended and 2 were permanently suspended because of better or worse patient conditions. There were 6 deceased patients. Transplanted organs came from the inter-regional area in 64% of cases. The average waiting time was 5.9 days. Within group A were a 311 transplantations among 723 waiting list patients on with a 13.7% mortality rate. Within group B were 305 transplantations among 871 wait-listed patients with a 14% mortality rate. DISCUSSION: The liver transplantation program for recipients with MELD scores ≥ 30 allowed recipients in critical condition to receive grafts without altering substantially the opportunities for recipients on the elective waiting list.

Disease-relevant proteostasis regulation of cystic fibrosis transmembrane conductance regulator.

Mismanaged protein trafficking by the proteostasis network contributes to several conformational diseases, including cystic fibrosis, the most frequent lethal inherited disease in Caucasians. Proteostasis regulators, as cystamine, enable the beneficial action of cystic fibrosis transmembrane conductance regulator (CFTR) potentiators in ΔF508-CFTR airways beyond drug washout. Here we tested the hypothesis that functional CFTR protein can sustain its own plasma membrane (PM) stability. Depletion or inhibition of wild-type CFTR present in bronchial epithelial cells reduced the availability of the small GTPase Rab5 by causing Rab5 sequestration within the detergent-insoluble protein fraction together with its accumulation in aggresomes. CFTR depletion decreased the recruitment of the Rab5 effector early endosome antigen 1 to endosomes, thus reducing the local generation of phosphatidylinositol-3-phosphate. This diverts recycling of surface proteins, including transferrin receptor and CFTR itself. Inhibiting CFTR function also resulted in its ubiquitination and interaction with SQSTM1/p62 at the PM, favoring its disposal. Addition of cystamine prevented the recycling defect of CFTR by enhancing BECN1 expression and reducing SQSTM1 accumulation. Our results unravel an unexpected link between CFTR protein and function, the latter regulating the levels of CFTR surface expression in a positive feed-forward loop, and highlight CFTR as a pivot of proteostasis in bronchial epithelial cells.

The use of neoplastic donors to increase the donor pool.

The aim of the study was to evaluate the experience of the Centre-Sud Transplant Organization (OCST) area using cadaveric donor with neoplastic diseases to evaluate the possibility of transmission to recipients. From January 1, 2003, to December 31, 2010, the neoplastic risk has been reported to be 5.4% (377/4654 referred donors). In 2003, the number of donors with a tumor and their mean age were respectively: 60 (10.3%) and 59.6 ± 19.9; 2004: 33 (5.2%) and 61.4 ± 15.9; 2005: 32 (6%) and 62.8 ± 15.5; 2006: 46 (7%) and 60.7 ± 19.1; 2007: 51 (7%) and 58.9 ± 16; in 2008: 58 (7%) and 59.7 ± 19.6; 2009: 47 (7%) and 57 ± 26; 2010: 49 (7%) and 64 ± 16. The organ most affected by tumor has been the central nervous system (18%). The tumor was diagnosed before in 325 (86%) cases, versus during organ retrieval in 48 (12.7%) donor operations but before, which four cases (1%) occured after transplantation. According to the histological types and grades, 28 evaluated donors (8.2%) were suitable for transplantation. The histological types were: thyroid carcinoma (n = 3); prostate carcinoma (n = 8), renal clear cell carcinoma (n = 7), oncocytoma (n = 1), meningiomas (n = 2), dermofibrosarcoma (n = 1); verrucous carcinoma of the vulva (n = 1), colon adenocarcinoma (n = 1), grade II astrocytoma (n = 1), adrenal gland tumor (n = 1), gastric GIST (n = 1), oligodendroglioma (n = 1). Forty-five organs were retrieved (22 livers, 19 kidneys, 3 hearts, and 1 pancreas) and transplanted into 44 recipients with 1 liver-kidney combined transplantation. Four recipients died due to causes not related to the tumor. No donor-transmitted tumor was detected among the recipients. Donation is absolutely not indicated in cases of tumors with high metastatic potential and high grades. Performing an accurate evaluation of the donor, taking into account the histological grade, currently can allow, organ retrieval and transplantation with an acceptable risk.

Risk management systems for health care and safety development on transplantation: a review and a proposal.

UNLABELLED: Starting from the report on medical errors published in 1999 by the US Institute of Medicine, a number of different approaches to risk management have been developed for maximum risk reduction in health care activities. The health care authorities in many countries have focused attention on patient safety, employing action research programs that are based on quite different principles. MATERIALS AND METHODS: We performed a systematic Medline research of the literature since 1999. The following key words were used, also combining boolean operators and medical subheading terms: "adverse event," "risk management," "error," and "governance." Studies published in the last 5 years were particularly classified in various groups: risk management in health care systems; safety in specific hospital activities; and health care institutions' official documents. Methods of action researches have been analysed and their characteristics compared. Their suitability for safety development in donation, retrieval, and transplantation processes were discussed in the reality of the Italian transplant network. DISCUSSION: Some action researches and studies were dedicated to entire national healthcare systems, whereas others focused on specific risks. Many research programs have undergone critical review in the literature. Retrospective analysis has centered on so-called sentinel events to particularly analyze only a minor portion of the organizational phenomena, which can be the origin of an adverse event, an incident, or an error. Sentinel events give useful information if they are studied in highly engineered and standardized organizations like laboratories or tissue establishments, but they show several limits in the analysis of organ donation, retrieval, and transplantation processes, which are characterized by prevailing human factors, with high intrinsic risk and variability. Thus, they are poorly effective to deliver sure elements to base safety management improvement programs, especially regarding multidisciplinary systems with high complexity. CONCLUSION: In organ transplantation, the possibility to increase safety seems greater using proactive research, mainly centred on organizational processes together with retrospective analyses but not limited to sentinel event reports.

Interleukin-7 stimulates osteoclast formation by up-regulating the T-cell production of soluble osteoclastogenic cytokines.

In unstimulated conditions osteoclast renewal occurs as a result of the stromal cell production of the key osteoclastogenic factors, receptor activator of NFkB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Inflammation is known to cause increased osteoclastogenesis; however, the mechanisms responsible for this phenomenon are poorly understood. We now show that interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha), cytokines typically produced in inflammatory conditions, increase the stromal cell production of IL-7. This factor, in turn, up-regulates production of osteoclastogenic cytokines by T cells leading to stimulation of osteoclast (OC) formation. Although T cells were found to produce soluble forms of both RANKL and M-CSF, saturating concentrations of osteoprotegerin failed to inhibit approximately 40% of the OC formation, suggesting that IL-7 acts via both RANKL-dependent and RANKL-independent pathways. Despite the identification of T-cell-secreted M-CSF, this cytokine was not essential for either RANKL-dependent or -independent OC formation, suggesting that T cells secrete other cytokines capable of substituting for M-CSF action. On the basis of our data, we propose a novel mechanism for inflammatory bone loss in which induction of IL-7 from stromal cells by IL-1 and TNFalpha leads to the production of soluble osteoclastogenic cytokines by T cells. Thus, the mechanism by which IL-7 causes bone resorption involves the activation of T cells and the T-cell-dependent augmentation of osteoclastogenesis. (Blood. 2000;96:1873-1878)

Estrogen decreases osteoclast formation by down-regulating receptor activator of NF-kappa B ligand (RANKL)-induced JNK activation.

The differentiation of cells of the monocytic lineage into mature osteoclasts (OC) is specifically induced by the tumor necrosis factor-related factor, RANKL (receptor activator of NF-kappaB ligand; also known as OPGL, ODF, or TRANCE). Because inhibition of osteoclastogenesis is one of the main mechanisms by which estrogen (E2) prevents bone loss, it is likely that E2 may regulate either the production of, or the target cell responsiveness to RANKL. We found that E2 decreases the differentiation into OC of both murine bone marrow monocytes and RAW 264.7 cells, a monocytic line, by down-regulating the activation of Jun N-terminal kinase 1 (JNK1). Diminished JNK1 activity results in decreased nuclear levels of the key osteoclastogenic transcription factors, c-Fos and c-Jun, and lower binding of these transcriptional inducers to DNA. Thus, one novel mechanism by which E2 down-regulates osteoclastogenesis is by decreasing the responsiveness of OC precursors to RANKL.

B lymphocytes inhibit human osteoclastogenesis by secretion of TGFbeta.

The role of B lymphocytes in osteoclast (OC) formation is controversial, because both stimulatory and inhibitory effects of B-lineage cells on osteoclastogenesis and life span have been reported. In this study, we have investigated the effects of mature B cells on human osteoclastogenesis using cultures of peripheral blood stem cells (PBSC), a system that generates functional OCs in the absence of stromal cells. We report that B cells inhibit the formation of OCs and shorten the life span of mature OCs by secreting transforming growth factor beta (TGFbeta), a factor that induces apoptosis in these cells. The antiosteoclastogenic effects of B cells are abolished by addition of anti-TGFbeta antibody to osteoclast cultures and mimicked by treatment of B cell-deprived PBSC cultures with recombinant TGFbeta, thus confirming TGFbeta as the B cell produced antiosteoclastogenic activity. Thus, the ability of B cells to downregulate osteoclastogenesis by secretion of the apoptotic cytokine TGFbeta provides new insights into the ability of immune cells to regulate OC formation under basal and inflammatory conditions.

Hip fracture in nursing homes: an Italian study on prevalence, latency, risk factors, and impact on mobility.

Hip fracture may cause and/or complicate institutionalization. We undertook this study to define its overall prevalence among the residents of four nursing homes in Central Italy as well as its latency and impact on mobility when it occurred within institutions. We also performed a case control analysis with the aim of identifying potential risk factors for hip fracture in nursing home. Among the 211 residents (160 women, mean age 82.2 +/- 9.29 years, and 51 men, mean age 77.1 +/- 8.9 years), 42 were hip fracture cases, with a prevalence of almost 20%, and a female/male ratio of 6/1.23 fractures preceded institutionalization; of these 19 (17 females and 2 males) occurred within the nursing homes (mean age 83.2 +/- 6.3 years). The average interval between institutionalization and fracture was 74.2 months. The impact of hip fracture on mobility was relevant. The percentage of residents ambulating autonomously fell from 95% to 32% among those who had fractured. Fractured subjects were characterized by worse mobility and function than unfractured subjects, while comorbidity, cognitive functions, and use of psychotropic drugs were similar. Prefracture mobility of fractured subjects was better than that of age-and sex-matched residents who had never fractured their hip. Regarding hip fracture in our nursing home population we can conclude that (1) hip fracture is one of the main causes of institutionalization; (2) in most cases hip fracture occurred late in the course of the nursing home stay; (3) the functional impact of the fracture was relevant when it occurred in institutions. We also suggest that preserved mobility may represent an additional risk factor for hip fracture in nursing homes.

Short-term reproducibility of proximal femur bone mineral density in the elderly.

Densitometric measurements are prone to imprecision in elderly subjects and the present study was primarily designed to dissect out the effects of age and bone mineral density on proximal femur dual energy x-ray absorptiometry (DXA) reproducibility. The study comprised 17 elderly women (mean age 74.6 years, range 65-84 years), 13 early postmenopausal women with osteopenia (mean age 56.2 years, range 50-63 years), and 17 elderly men (mean age 73.8 years, range 65-86 years). Each subject was given triplicate proximal femur scans by a QDR 2000 Densitometer (Hologic Inc., Waltham, MA) with repositioning between scans. Because of subject selection in the early postmenopausal women there were no significant differences in bone mineral density (BMD) at any site among the three groups. Despite this, reproducibility errors expressed as either coefficient of variation (CV) % or mean standard deviation (SD) were greater in the elderly subjects, regardless of gender, when compared with the younger female subjects. The variability in measurement errors with age were least marked for the total hip and trochanteric sites. Within the elderly subjects, BMD appeared to exert little influence on measurement errors. We conclude that short-term proximal femur reproducibility is dependent on age-related factors other than BMD. There is no influence of gender on the measurement errors. It is likely that local factors (e.g., hip osteoarthritis) or general frailty may influence repositioning but this needs further exploration. In the meantime, the total hip and trochanteric sites should be used as they provide the most reproducible measurements in the elderly.

Up-regulation of TNF-producing T cells in the bone marrow: a key mechanism by which estrogen deficiency induces bone loss in vivo.

In vivo studies have shown T cells to be central to the mechanism by which estrogen deficiency induces bone loss, but the mechanism involved remains, in part, undefined. In vitro, T cells from ovariectomized mice produce increased amounts of tumor necrosis factor (TNF), which augments receptor activator of NF-kappa B ligand (RANKL)-induced osteoclastogenesis. However, both the mechanism and the relevance of this phenomenon in vivo remain to be established. In this study, we found that ovariectomy increased the number of bone marrow T cell-producing TNF without altering production of TNF per T cell. Attesting to the essential contribution of TNF, ovariectomy induced rapid bone loss in wild type (wt) mice but failed to do so in TNF-deficient (TNF(-/-)) mice. Furthermore, ovariectomy induced bone loss, which was absent in T cell-deficient nude mice, was restored by adoptive transfer of wt T cells, but not by reconstitution with T cells from TNF(-/-) mice. These findings demonstrate the key causal role of T cell-produced TNF in the bone loss after estrogen withdrawal. Finally, ovariectomy caused bone loss in wt mice and in mice lacking p75 TNF receptor but failed to do so in mice lacking the p55 TNF receptor. These findings demonstrate that enhanced T cell production of TNF resulting from increased bone marrow T cell number is a key mechanism by which estrogen deficiency induces bone loss in vivo. The data also demonstrate that the bone-wasting effect of TNF in vivo is mediated by the p55 TNF receptor.