Lead exposure inhibits fracture healing and is associated with increased chondrogenesis, delay in cartilage mineralization, and a decrease in osteoprogenitor frequency

Decrypting the skeletal toxicity of vertebrates caused by environmental pollutants from an evolutionary perspective: From fish to mammals

The rapid development of modern society has led to an increasing severity in the generation of new pollutants and the significant emission of old pollutants, exerting considerable pressure on the ecological environment and posing a serious threat to both biological survival and human health. The skeletal system, as a vital supportive structure and functional unit in organisms, is pivotal in maintaining body shape, safeguarding internal organs, storing minerals, and facilitating blood cell production. Although previous studies have uncovered the toxic effects of pollutants on vertebrate skeletal systems, there is a lack of comprehensive literature reviews in this field. Hence, this paper systematically summarizes the toxic effects and mechanisms of environmental pollutants on the skeletons of vertebrates based on the evolutionary context from fish to mammals. Our findings reveal that current research mainly focuses on fish and mammals, and the identified impact mechanisms mainly involve the regulation of bone signaling pathways, oxidative stress response, endocrine system disorders, and immune system dysfunction. This study aims to provide a comprehensive and systematic understanding of research on skeletal toxicity, while also promoting further research and development in related fields.

Molecular mechanisms of environmental pollutant-induced cartilage damage: from developmental disorders to osteoarthritis

The objective of the present study was to review the molecular mechanisms of the adverse effects of environmental pollutants on chondrocytes and extracellular matrix (ECM). Existing data demonstrate that both heavy metals, including cadmium (Cd), lead (Pb), and arsenic (As), as well as organic pollutants, including polychlorinated dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCB), bisphenol A, phthalates, polycyclic aromatic hydrocarbons (PAH), pesticides, and certain other organic pollutants that target cartilage ontogeny and functioning. Overall, environmental pollutants reduce chondrocyte viability through the induction apoptosis, senescence, and inflammatory response, resulting in cell death and impaired ECM production. The effects of organic pollutants on chondrocyte development and viability were shown to be mediated by binding to the aryl hydrocarbon receptor (AhR) signaling and modulation of non-coding RNA expression. Adverse effects of pollutant exposures were observed in articular and growth plate chondrocytes. These mechanisms also damage chondrocyte precursors and subsequently hinder cartilage development. In addition, pollutant exposure was shown to impair chondrogenesis by inhibiting the expression of Sox9 and other regulators. Along with altered Runx2 signaling, these effects also contribute to impaired chondrocyte hypertrophy and chondrocyte-to-osteoblast trans-differentiation, resulting in altered endochondral ossification. Several organic pollutants including PCDD/Fs, PCBs and PAHs, were shown to induce transgenerational adverse effects on cartilage development and the resulting skeletal deformities. Despite of epidemiological evidence linking human environmental pollutant exposure to osteoarthritis or other cartilage pathologies, the data on the molecular mechanisms of adverse effects of environmental pollutant exposure on cartilage tissue were obtained from studies in laboratory rodents, fish, or cell cultures and should be carefully extrapolated to humans, although they clearly demonstrate that cartilage should be considered a putative target for environmental pollutant toxicity.

Bullet Fragment Retrieval During Intramedullary Nailing: A Report of 2 Cases

CASE

Two young adult patients, 22 and 27 years, who sustained ballistic long bone fractures, presented for incarcerated, retained metallic fragments in the medullary canal, which blocked fixation. Owing to the presence and location of the fragments, each case required a bullectomy (removal of the metallic fragment) before intramedullary nail fixation because the projectile impeded the appropriate insertion of the intramedullary rod and, in one case, induced fracture malalignment. Attempts at removal using conventional tools did not provide adequate length or grasp of the retained projectile, necessitating the use of the novel technique. The Babcock Laparoscopic Endopath is an easy-to-use, ubiquitous tool that facilitates the removal of content within the intramedullary canal, including metallic or bony fragments.

CONCLUSION

There is limited literature describing accessible, cost-effective techniques for the removal of intramedullary retained metallic foreign fragments when it is unremovable through conventional means. This article reports on a novel, minimally invasive technique for bullet removal from the intramedullary canal of the femur and tibia using the Babcock Laparoscopic Endopath, a tool typically used by urologists. Both patients were followed for at least 8 weeks postoperatively with no complications secondary to the procedure. The article describes the technique and advantages of using this readily available tool that is both flexible enough to navigate through the intramedullary canals as well as rigid enough to obtain and manipulate metallic objects.

Combined exposure to lead and high-fat diet induced neuronal deficits in rats: Anti-neuroinflammatory role of SIRT1

INTRODUCTION

Lead (Pb) exposure and high-fat diet (HFD) trigger neurotoxicity, which may involve neuroinflammation. However, the mechanism by which combined Pb and HFD exposure induces nucleotide oligomerization domain-like receptor family pyrin domain 3 (NLRP3) inflammasome activation has not been fully elucidated.

MATERIAL AND METHODS

The Sprague-Dawley (SD) rat model of exposure to Pb and HFD was established to reveal the influence of co-exposure on cognition and identify signaling clues that mediate neuroinflammation and synaptic dysregulation. PC12 cells was treated with Pb and PA in vitro. Silent information regulator 1 (SIRT1) agonist (SRT 1720) was employed as intervention agent.

RESULTS

Our results showed that Pb and HFD exposure induced cognitive impairment and lead to neurological damage in rats. Meanwhile, Pb and HFD could stimulate the NLRP3 inflammasome assembly and activate caspase 1, releasing proinflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18), further promoting neuronal cell activation and amplifying neuroinflammatory responses. Additionally, our findings suggest that SIRT1 plays a role in Pb and HFD induced neuroinflammation. However, the use of SRT 1720 agonists showed some potential in alleviating these impairments.

CONCLUSION

Pb exposure and HFD intake could induce neuronal damage through activation of the NLRP3 inflammasome pathway and synaptic dysregulation, while the NLRP3 inflammasome pathway may be rescued via activating SIRT1.

High-fat diet in mice led to increased severity of spermatogenesis impairment by lead exposure: perspective from gut microbiota and the efficacy of probiotics

BACKGROUND

The mechanism of multifactorial spermatogenesis impairment is unclear. This study aimed to investigate the reproductive toxicity of lead (Pb) in mice fed a high-fat diet (HFD) and to delineate the important role of gut microbiota.

RESULTS

Results showed that, compared with mice fed a normal diet (ND), Pb exposure caused more severe spermatogenesis impairment in HFD-fed mice, including decreased sperm count and motility, seminiferous tubule injury, serum and intratesticular testosterone decline, and downregulated expression level of spermatogenesis-related genes. Besides, 16S sequencing indicated that HFD-fed mice had increased severity of gut microbiota dysbiosis by Pb exposure compared to ND-fed mice. With fecal microbiota transplantation, the same trend of spermatogenesis impairment occurred in recipient mice, which confirmed the important role of gut microbiota. Moreover, probiotics supplementation restored the gut microbial ecosystem, and thus improved spermatogenic function.

CONCLUSION

Our work suggested that a population with HFD might face more reproductive health risks upon Pb exposure, and revealed an intimate linkage between microbiota dysbiosis and spermatogenesis impairment, accompanied by the potential usefulness of probiotics as prophylactic and therapeutic. © 2022 Society of Chemical Industry.

Sources of Lead Exposure in West Africa

This commentary is an investigation of sources of lead (Pb) exposure in West Africa. Pb is generally acknowledged as one of the most widespread environmental health hazards in West Africa, and there is heightened concern over adverse health effects at various levels of exposure (at doses once considered safe) in the West African region. A literature review for the possible health implications of Pb exposure on human health showed nervous system dysfunction, anemia, and potential cognitive diseases as the major health issues among children, while adults were found to suffer more from cardiovascular dysfunction, neurological decline, and reproductive diseases. Despite a decline in blood lead levels (BLLs), lead exposure continues to be a major public health concern as no level of Pb exposure can be considered safe. Moreover, lowering BLLs entails identifying various lead sources such as gasoline emissions, leaded paint, canned foods, and beverages, as well as plausible biological pathways of lead exposure and response. However, only countries such as Nigeria and Ghana have extensive research available regarding the different sources of Pb exposure. Further, it is not apparent which country is affected the most by Pb exposure. Therefore, this commentary was aimed to explore different literature sources to describe and list the different sources of Pb exposure in 15 West African countries. The findings indicated water, food, and occupational exposure as the major sources of Pb exposure in the region. People with occupations such as e-waste and Pb acid battery recycling, auto mechanics, fuel attending, welding, electronic repairing, farming/spraying, and mining were found to be at immediate risk. Tobacco, spices and paints constituted additional potential sources of exposure. For residents living near landfills or urban area, the major sources of Pb exposure were soil, air, and dust particles. The review revealed a vast research gap on the sources and implications of Pb exposure. Exposure to Pb could further increase due to uncontrolled traffic, urban growth, inadequate urban planning, and the inadequate enforcement of regulations. Therefore, more extensive research on the changing trends of Pb exposure among West African populations is needed.

Lead inhibits the odontogenic differentiation potential of dental pulp stem cells by affecting WNT1/β-catenin signaling and related miRNAs expression

Lead (Pb) is ubiquitous in environment that accumulates in teeth and calcified tissues from where it releases gradually with aging and adversely affects dental health. This study aimed to determine the effect of Pb exposure on odontogenic differentiation potential of isolated human dental pulp stem cells and investigate the possible underlying epigenetic factors. In the absence of Pb exposure, stem cells displayed significant odontogenic markers including elevated Alkaline Phosphatase (ALP) activity, Alizarin red staining intensity, and increased expression of odontogenic DMP1 and DSPP genes. Exposure to 60 μM Pb resulted in reduced ALP activity and calcium deposition. Also, diminished expression of RUNX2, DMP1, and DSPP, as well as Wnt signaling mediators including WNT1, and β-catenin were detected. The expression of Wnt signaling related microRNAs, miRNA-139-5p and miRNA-142-3p, on the other hand, were shown to have a significant increase. We concluded that Pb could adversely affect the odontogenic differentiation potential of dental pulp stem cell. The underlying mechanism might related to Pb-induced epigenetic dysregulation of WNT1/β-catenin pathway-related miRNAs leading to down-regulation of Wnt/β-catenin related odontogenic genes and eventually impaired odontogenic differentiation process.

The Abundance of Trace Elements in Human Bone Relative to Bone Type and Bone Pathology

As the global population ages and the proportion of individuals afflicted with musculoskeletal disease spirals upward, there is an increasing interest in understanding and preventing bone-related diseases. Bone diseases, such as osteoporosis and osteoarthritis, are known to be influenced by a variety of factors including age, gender, nutrition, and genetics, but are also inherently linked to the human body's ability to produce biominerals of suitable quality. Because the crystal lattice structure and mineralogy of bone hydroxyapatite is surprisingly analogous to geological hydroxyapatite, trace element levels and exposure have long been proposed to influence the structure of biominerals as they do geological minerals (e.g., strontium substitution changes the crystal lattice of bone minerals, while toxic lead disrupt bone cellular processes leading to bone disease). Here, we explore the distribution of trace elements in human bones to evaluate the distribution of these elements with respect to bone type (cortical vs. trabecular) and bone disease (osteoarthritis vs. osteoporosis). We find higher concentrations of many metabolically active transition metals, as well as lead, in cortical bone compared to trabecular bone. When compared to patients who have osteoarthritis, and thus presumably normal bone minerals, osteoporosis patients have higher concentrations of scandium and chromium (Cr) in trabecular bone, and Cr and lead in cortical bone. Lower concentrations of barium and titanium are associated with osteoporotic trabecular bone. This survey is an exploratory cross-sectional geochemical examination of several trace element concentrations previously understudied in human bone minerals.

Association between Musculoskeletal Pain and Bone Turnover Markers in Long-Term Pb-Exposed Workers

Background: On chronic exposure, Lead (Pb) deposits in the skeletal system, replaces calcium ions, and alters the normal physiological processes, which in turn, lead to stunting, delayed fracture healing, and high resorption of collagen molecules. The present study aimed to assess the association of musculoskeletal pain and discomfort with bone turnover markers (BTMs) among long-term Pb-exposed workers.

Study design: A cross-sectional study.

Methods: The study recruited 176 male Pb-exposed workers and 80 control subjects who were matched for age, gender, and socio-economic status. Blood lead levels (BLLs), bone growth markers, such as serum osteocalcin (OC), alkaline phosphatase (ALP), bone alkaline phosphatase (BAP), and bone resorption markers: serum pyridinoline (Pry), deoxypyridinoline (DPry), tartrate-resistant acid phosphatase-5b(TRACP-5b), and hydroxyproline in urine (HyP-U) of participants were investigated. Pain and discomfort in the musculoskeletal system were assessed using Nordic Musculoskeletal Questionnaire.

Results: Pb-exposure was significantly associated with musculoskeletal discomfort of the lower back (P<0.001), upper back (P<0.001), and ankle/foot (P=0.011). Among bone formation markers, serum OC was significantly lower in musculoskeletal discomfort of elbows (P=0.033) and ankle/foot (P=0.042). Among bone resorption markers, serum DPry was significantly lower in musculoskeletal discomfort of the neck (P=0.049) and shoulders (P=0.023). HyP-U was significantly higher in musculoskeletal discomfort of shoulders (P=0.035) and lower back (P=0.036).

Conclusion: As evidenced by the obtained results, Pb-exposure was associated with musculoskeletal discomfort of the lower back, upper back, and ankle/foot. Lower bone formation (serum OC) marker was noted with musculoskeletal discomfort of elbows and ankle/foot. Furthermore, bone resorption markers were associated with musculoskeletal discomfort of the neck, shoulders, and lower back. The findings of the present study suggested that long-term Pb-exposure and BTMs were associated with musculoskeletal discomfort.

Lead Levels in Wild Boar Meat Sauce (Ragù) Sold on the Italian Market

Game meat is endowed with excellent nutritional value, but it may also be a possible source of harmful substances, such as mycotoxins and heavy metals. In particular, several studies showed that lead fragments from hunting ammunition are able to represent a residual contaminant in the meat of wild boars or deer, representing a possible source of lead absorption. Even though wild boar meat consumption in Italy is rather limited, this meat could also be present in very popular Italian recipes, such as the typical meat sauce called ragù. We evaluated the lead levels in 48 samples (three different batches for each of the 16 brands) of ready-to-eat wild boar meat ragù sold on the Italian market in food stores and online distribution with the inductively coupled plasma-mass spectrometry (ICP-MS) technique. A high variability was found in the lead levels detected in the samples, with a median lead level of 0.10 mg/kg (0.01–18.3 mg/kg) and some of the samples showing very high lead concentrations. Since no intake level of lead is considered completely safe, and maximum levels for game meat have so far not been established, a greater attention on the risks to consumers’ health related to the presence of this heavy metal in game meat is recommended.

The associations between serum trace elements and bone mineral density in children under 3 years of age

We examined the associations of age and serum magnesium, iron, lead, copper, and zinc levels with bone mineral density (BMD) in 2412 children under 3 years of age in order to find a tool to monitor BMD in children without the use of expensive imaging techniques. One-way ANOVA and chi-square tests were used to determine the associations of age and serum trace elements with BMD. Multivariable logistic regression analysis was used to test the correlation of five serum trace elements with BMD after adjustments for potential confounding factors in children under 3 years of age. Significant associations between age and four serum trace elements and BMD were found. Compared to the group with the lowest serum levels detected, the adjusted odds ratio (OR) for the incidence of normal bone mineral density in the third magnesium concentration tertile, the third iron concentration tertile, the fifth copper concentration quintile, the third zinc concentration quintile, and the fifth zinc concentration quintile were 1.30 (95% confidence interval (CI) 1.02–1.67), 1.43 (95% CI 1.11–1.84), 1.42 (95% CI 1.04–1.94), 1.46 (95% CI 1.05–2.04), and 1.48 (95% CI 1.06–2.06), respectively. However, there was no significant correlation between serum lead level and BMD in this study. Age and serum magnesium, iron, copper, and zinc levels are positively associated with BMD in children under 3 years old.

Protection of lead-induced cytotoxicity using paramagnetic nickel–insulin quantum clusters

Pb-toxicity is associated with inflammation which leads to delay in wound healing. Pb²⁺ utilizes calcium ion channels to enter the cell. Therefore, to achieve effective healing in a Pb-poisoned system, capturing Pb²⁺ from the circulatory system would be an effective approach without hampering the activity of the calcium ion channel. In this work insulin–nickel fluorescent quantum clusters (INiQCs) have been synthesized and used for the specific detection of Pb²⁺ ions in vitro and in cell-free systems. INiQCs (0.09 μM) can detect Pb²⁺ concentrations as low as 10 pM effectively in a cell-free system using the fluorescence turn-off method. In vitro INiQCs (0.45 μM) can detect Pb²⁺ concentrations as low as 1 μM. INiQCs also promote wound healing which can easily be monitored using the bright fluorescence of INiQCs. INiQCs also help to overcome the wound recovery inhibitory effect of Pb²⁺in vitro using lead nitrate. This work helps to generate effective biocompatible therapeutics for wound recovery in Pb²⁺ poisoned individuals.

Receptor targeted ferromagnetic Insulin–Nickel Quantum fluorescence Clusters (INiQCs) can specifically detect Pb²⁺ and prevents Pb²⁺ poisoning.

The role of arthroscopy in bullet removal: A systematic review of the literature

Purpose

The purpose of this study was to systematically review the literature to gain a greater understanding of the role and usage of arthroscopy in removal of retained bullet fragments. Secondarily, we intend to examine the level of evidence and methodologic quality of studies reporting on this topic.

Methods

A search of PubMed, MEDLINE, and Cochrane Database of Systematic Reviews was performed using the search terms ("Arthroscopic" OR "Arthroscopy") AND ("Bullet" OR "Gunshot" OR "Ballistic" OR "Removal"). Inclusion criteria included articles published in English reporting on arthroscopic or arthroscopically-assisted bullet removal. Studies lacking sufficient data to separate arthroscopic and open procedures were excluded. Level of evidence, study information (i.e., country, journal, etc.), and patient data was collected from each eligible article. The methodological index for non-randomized studies (MINORS) score were assigned to each article.

Results

A total of 2676 studies were identified in the initial search with 31 studies meeting criteria for inclusion in the study. Twenty-eight of the 31 studies were case reports. The MINORS score averaged 8.8 ± 1.5 (range 5-10) for included studies. Sixty-two patients were identified, the majority (94%) of whom were male with an average age of 36.2 ± 12.3 years. All 62 patients underwent successful arthroscopic bullet removal. One patient was reported to have a complication (compartment syndrome). Outcome measures were underreported in the majority of studies.

Conclusions

Our study found that very little literature exists on the role of arthroscopy in bullet removal. Of this literature, no high-quality studies exist. Based on the limited existing literature, arthroscopy appears to be a safe, reliable alternative to open surgery for bullet removal. Potential benefits of arthroscopic bullet removal exist and warrant further investigation to further define the role of arthroscopy.

Level of evidence

Level V.

Orthopedic Manifestations of Lead Toxicity

Given the recent news regarding the water supply in Flint, Michigan, lead toxicity has become an increasingly important topic in health care. Lead toxicity can have a widespread effect on the human body. Because lead has a significant effect on mineralized tissue such as bone, the purpose of this review was to identify and analyze the orthopedic manifestations of lead poisoning. The effects of lead at the cellular level, on the hematopoietic system, in osteoporosis, and in pediatric patients are discussed. Possible treatment options and recommendations for further monitoring are presented. [Orthopedics. 2020;43(4):e202-e207.].

Long-Term Exposure to Low-Dose Lead Induced Deterioration in Bone Microstructure of Male Mice

The aim of this study was to investigate the long-term effects of low-dose lead exposure on bone microstructure in mice. Ten SPF 12-week-old male C57BL/6J mice were randomly divided into two groups: control (deionized water) and lead exposure (150 ppm of lead acetate in drinking water). After 24 weeks treatment, mice were weighed and the left femurs were collected and stored at - 80 °C. The right femurs of the mice were scanned by Micro-CT for three-dimensional reconstruction, and bone mineral density, bone volume fraction, trabeculae thickness, trabeculae number, and trabeculae separation were measured. The right tibia was collected to investigate histopathological changes in H&E-stained sections. The gene expression of osteoprotegerin (OPG), RANKL, and runt-related transcription factor 2 (Runx2) was determined using real-time PCR. The bone density of femoral cancellous bone and the number of cancellous bone trabeculae in the lead exposure group were both significantly decreased compared with the control group. Bone marrow stromal cell numbers were decreased following lead administration, and lipid droplet vacuoles were observed in the lead group. Levels of OPG were significantly decreased in the lead group, and lead also inhibited the expression of Runx2 compared with the control group. Long-term exposure to low doses of lead can cause bone damage without inducing other obvious symptoms through decreasing bone density and the number of cancellous bone trabeculae, further suppressing bone formation. It suggests that lead may exacerbate bone loss and osteoporosis, especially in the elderly.

Therapeutic role of garlic and vitamins C and E against toxicity induced by lead on various organs

Due to industrial and urban sewage, the metal contaminations in aquatic and terrestrial environments are increasing day by day, especially in developing countries. Despite the study of several years, we are inert far away from an actual medication for prolonged toxicity of heavy metals such as mercury, lead, cadmium etc. Lead is one of the most common heavy metals that possess toxicological effects on numerous tissues of animals as well as humans. Several toxic effects of lead on reproductive organs, renal system, central nervous system, liver, lungs, blood parameters, and bones have been reported. On the other hand, several reports depicted that garlic is operative in declining the absorption of lead in bones as well as soft tissues. A combination of vitamin C and vitamin E enhances the biological recovery induced by lead and mobilize the heavy metal such as lead from intra-cellular positions. This review provides therapeutic approaches such as vitamin C, vitamin E, and extract of garlic to treat the detrimental effects caused after the exposure of lead. These therapeutic strategies are beneficial for both the prevention and alleviation of lead noxiousness.

Elevated levels of lead exposure and impact on the anti-inflammatory ability of oral sialic acids among preschool children in e-waste areas

The oral health of preschool children in an electronic waste (e-waste) area is susceptible to lead (Pb) exposure increasing the risk of dental caries and causing periodontitis and other oral diseases. The aim of the present study is to investigate the relationship between chronic exposure to Pb and oral anti-inflammatory potential of preschool children. For this analysis, 574 preschool children from 2.5 to 6 years of age were recruited between November and December 2017, in which 357 preschool children were from Guiyu (n = 357), an e-waste-contaminated town, and 217 from Haojiang Shantou. We measured the levels of child blood Pb, salivary sialic acid, serum interleukin-6 (IL-6) and serum tumor necrosis factor-α (TNF-α), and investigated the prevalence of dental caries in deciduous teeth. The medians of blood Pb levels, serum IL-6 and TNF-α were significantly higher in the Guiyu children than in Haojiang children. Concomitantly, salivary sialic acids were lower in the Guiyu children [9.58 (3.97, 18.42) mg/dL] than in Haojiang [17.57 (5.95, 24.23) mg/dL]. Additionally, the prevalence of dental caries in deciduous teeth was significantly higher in the Guiyu children than in Haojiang (62.5% vs. 53.9%). Blood Pb levels were negatively correlated with salivary sialic acids, in which IL-6 played as a mediator of the association between blood Pb levels and saliva sialic acid concentrations according to the mediation model. To our knowledge, this is the first report on the potential association between chronic Pb exposure and the anti-inflammatory ability of oral sialic acids among preschool children. These results suggest that the chronic Pb exposure can reduce salivary sialic acid levels, attenuate oral anti-inflammatory potential and increase the potential risk of dental caries in deciduous teeth among preschool children in an e-waste site.

Impacts of lead exposure and chelation therapy on bone metabolism during different developmental stages of rats

OBJECTIVE

To explore the impacts of Pb exposure and the dimercaptosuccinic acid (DMSA) chelation therapy on bone metabolisms in young rats of different ages, as well as the potential mechanisms.

METHOD

Young rats were exposed to 0.05%-0.1% Pb acetate for 19 days, during infanthood (postnatal day, PND2-20), childhood (PND21-39) and adolescenthood (PND40-58) respectively. In each developmental stage, rats were further divided into three subgroups: lead-exposed, one-course and two-course DMSA chelation therapy subgroups. Blood/bone lead concentrations, serum calciotropic hormones concentrations, and mRNA and protein expressions of bone turnover markers in the serum and bones were measured. Bone microstructures were analyzed using Micro-CT.

RESULTS

Compared with lead-exposed during childhood and adolescenthood, increases in blood/bone lead levels, and the changes of blood/bone lead and trabecular bone microstructures after one-course DMSA chelation were most significant in rats lead-exposed during infanthood (P < .05). The serum osteocalcin (OC) concentrations, mRNA/protein expressions of OC and runt-related transcription factor 2 (RUNX2) in bones all decreased after Pb exposure, along with significant increases in serum C-terminal telopeptide of type I collagen (CTX) concentrations (P < .05). These effects were accompanied by changes of serum parathormone (PTH) and 1,25-dihydroxyvitamin D₃ (1,25-(OH₂)-D₃) concentrations. DMSA chelation partially reversed the changes of bone microarchitectures, bone formation and resorption markers, and calciotropic-hormones, and the efficiency was greatest when the therapy was provided during infanthood.

CONCLUSION

Developmental Pb exposure impaired bone microstructures and interfered bone metabolism, and the exposure effect was more obvious during infanthood than during childhood and adolescenthood. Lead effects were partially reversed by chelation therapy, and the efficacy may be most significant when the therapy was provided at younger ages.

Dechelation (Transmetalation): Consequences and Safety Concerns With the Linear Gadolinium-Based Contrast Agents, In View of Recent Health Care Rulings by the EMA (Europe), FDA (United States), and PMDA (Japan)

The issue of dechelation (transmetallation) in vivo after administration of the linear gadolinium-based contrast agents, and potential safety concerns, is considered on the basis of an extensive, focused literature review. Early indications of potential problems included the high level of excess ligand used in the formulation of 2 agents (indeed the 2 least stable thermodynamically) and interference with laboratory tests when blood was drawn from patients relatively soon after administration of these same agents. The advent of nephrogenic systemic fibrosis in the late 2000s raised additional major concerns.The correlation in 2014 of dentate nucleus hyperintensity on precontrast T1-weighted scans with multiple prior injections of linear gadolinium chelates, in patients with normal renal function, has driven subsequent research concerning dechelation of these agents in vivo. Unexpectedly high levels of gadolinium in the bone, skin, and liver have been found long term after administration, in animal models and in humans, although the latter data are limited. Bone may serve as a long-term reservoir, with a residual excretion phase for gadolinium after intravenous injection of the linear agents due to a subsequent slow release from bone. Many different patient populations could be vulnerable and potentially later develop clinical symptoms, although at this stage there are only limited data and small retrospective uncontrolled studies. Possible vulnerable populations include children, menopausal women, patients with osteoporosis (who are predisposed to fractures and often slow to heal or heal poorly), those receiving multiple doses, those with proinflammatory conditions, moderate renal dysfunction, or an undefined genetic predisposition. Of particular concern would be nephrogenic systemic fibrosis-like symptoms-including particularly pain and skin/joint symptoms, or disease related to the incorporation of gadolinium in hydroxyapatite in bone, in small subgroups of patients with a not yet defined propensity and/or cofactor. These concerns have led to withdrawal of the linear agents from the largest clinical market, Europe, with the exception of the hepatobiliary agents for delayed liver imaging, an indication that cannot be fulfilled by the current macrocyclic gadolinium chelates (for which these concerns do not apply).

The effects of lead on the development of somites in chick embryos (Gallus gallus domesticus) under in vitro conditions: a histological study

Lead (Pb) is one of the most abundant toxic metals in the environment that can cause a variety of harmful effects. During embryonic development of vertebrates, somites are temporary organs that give rise to skeletal muscle, cartilage, tendon, endothelial cells, and dermis. In this study, we investigated the effects of lead on the development of somites and their derivatives in chick embryos under in vitro conditions. For this propose, fertilized eggs of Gallus gallus domesticus were incubated until they reached the stage of 15-20 somites. The somites and notochord were isolated and treated with different concentrations of lead acetate (500, 1000, 2000, and 4000 ng ml-1) for 72 h. Our results indicated that high concentrations of lead reduced the nucleus diameter, reduced the synthesis of collagen, inhibited the formation of the cartilage matrix in somite cells, and disturbed the formation and order of myotubes. In conclusion, the results of the current study for the first time indicated the disturbing effects of lead on the development of somites in the chick embryo. Our results revealed that lead disturbed the development of somites in the chick embryo, which suggested that at high concentrations it can cause a serious mortal danger to life.

Lead and copper in hunted wild boars and radiographic evaluation of bullet fragmentation between ammunitions

The purpose of the present study was to evaluate the content of lead in carcasses of wild boars shot with lead bullets, in comparison with that of copper caused by lead-free ammunitions. Radiographic images of hunted boars were obtained in order to assess the degree of bullet fragmentation in the carcasses. Samples of meat were collected from different body areas at increasing distance from bullet trajectory, to be analysed by ICP-MS for lead and copper levels. In wild boars shot with lead ammunitions, a massive dispersion of bullet fragments and very high lead levels were detected. By contrast, in wild boars killed with copper ammunitions no radiographic signs of bullet fragmentation were observed. Copper ammunitions seem therefore a safer alternative to standard lead-core ones, due to their minimal fragmentation and the relatively low toxicity of this metal.

A Review of Metal Exposure and Its Effects on Bone Health

The presence of metals in the environment is a matter of concern, since human activities are the major cause of pollution and metals can enter the food chain and bioaccumulate in hard and soft tissues/organs, which results in a long half-life of the metal in the body. Metal intoxication has a negative impact on human health and can alter different systems depending on metal type and concentration and duration of metal exposure. The present review focuses on the most common metals found in contaminated areas (cadmium, zinc, copper, nickel, mercury, chromium, lead, aluminum, titanium, and iron, as well as metalloid arsenic) and their effects on bone tissue. Both the lack and excess of these metals in the body can alter bone dynamics. Long term exposure and short exposure to high concentrations induce an imbalance in the bone remodeling process, altering both formation and resorption and leading to the development of different bone pathologies.

Alterations of mineralized matrix by lead exposure in osteoblast (MC3T3-E1) culture

The present study investigated the effect of lead (Pb) on bone ultrastructure and chemistry using an in vitro bone model. MC3T3-E1 preosteoblasts were differentiated and treated with lead acetate at 0.4, 2, 10, and 50 μM. No abnormalities in either cell growth or bone nodule formation were observed with the treated dose of lead acetate. However, Pb treatments could significantly increase Pb accumulation in differentiated osteoblast cultures and upregulate expression of Divalent metal transporter 1 (Dmt1) in a dose dependent manner. Pb treatments also altered the expression of osteogenic genes, including secreted phosphoprotein 1, osteocalcin, type I collagen, and osteoprotegerin. Moreover, in mineralized osteoblast cultures, Pb was found to be mainly deposited as Pb salts and oxides, respectively. Ultrastructure analysis revealed Pb localizing with calcium and phosphorus in the mineralized matrix. In mineralizing osteoblast cells, Pb was found in the intracellular calcified vesicles which is one of the bone mineralization mechanisms. Pb was also present in mineral deposits with various shapes and sizes, such as small and large globular or needle-like mineral deposits representing early to mature stages of mineral deposits. Furthermore, Pb was found more in the globular deposits than the needle shaped mineral crystals. Taken together, our observations revealed how Pb incorporates into bone tissue, and showed a close association with bone apatite.

Study on the relationship between age and the concentrations of heavy metal elements in human bone

Background

Excessive amounts of heavy metals such as cadmium, chromium, cobalt, lead, thallium, and manganese are extremely harmful to the human body. These elements can accumulate in bone and impact bone metabolism. In this study, we investigated the relationship between age and the concentrations of these elements in human bone and blood.

Methods

Bone and blood samples were obtained from both older and younger patients. The concentrations of the elements under investigation were measured by inductively coupled plasma mass spectrometry (ICP-MS), and the specific concentrations in the bone and blood were then calculated.

Results

The results showed that with increasing age, the concentrations of chromium, cobalt, and thallium in bone decreased significantly, while the concentration of cadmium in bone markedly increased. However, there was no clear correlation between age and the concentrations of these heavy metals in blood. Notably, there was a close correlation between the concentration of cobalt in bone and the presence of osteopenia.

Conclusions

Senescence of the human body is accompanied by the shifting of cobalt, chromium, and thallium from the bone to the outer- bone. However, the concentration of cadmium in bone increases with age. These changes are very likely to be related to the equilibrium of bone metabolism in senescent individuals. In addition, only cobalt was shown to be significantly related to osteopenia.

Nuclear receptor and VEGF pathways for gene-blood lead interactions, on bone mineral density, in Korean smokers

Osteoporosis has a complex etiology and is considered a multifactorial polygenic disease, in which genetic determinants are modulated by hormonal, lifestyle, environmental, and nutritional factors. Therefore, investigating these multiple factors, and the interactions between them, might lead to a better understanding of osteoporosis pathogenesis, and possible therapeutic interventions. The objective of this study was to identify the relationship between three blood metals (Pb, Cd, and Al), in smoking and nonsmoking patients' sera, and prevalence of osteoporosis. In particular, we focused on gene-environment interactions of metal exposure, including a dataset obtained through genome-wide association study (GWAS). Subsequently, we conducted a pathway-based analysis, using a GWAS dataset, to elucidate how metal exposure influences susceptibility to osteoporosis. In this study, we evaluated blood metal exposures for estimating the prevalence of osteoporosis in 443 participants (aged 53.24 ± 8.29), from the Republic of Korea. Those analyses revealed a negative association between lead blood levels and bone mineral density in current smokers (p trend <0.01). By further using GWAS-based pathway analysis, we found nuclear receptor (FDR<0.05) and VEGF pathways (FDR<0.05) to be significantly upregulated by blood lead burden, with regard to the prevalence of osteoporosis, in current smokers. These findings suggest that the intracellular pathways of angiogenesis and nuclear hormonal signaling can modulate interactions between lead exposure and genetic variation, with regard to susceptibility to diminished bone mineral density. Our findings may provide new leads for understanding the mechanisms underlying the development of osteoporosis, including possible interventions.

Laser-induced plasma spectroscopy (LIPS): use of a geological tool in assessing bone mineral content

Bone may be similar to geological formulations in many ways. Therefore, it may be logical to apply laser-based geological techniques in bone research. The mineral and element oxide composition of bioapatite can be estimated by mathematical models. Laser-induced plasma spectrometry (LIPS) has long been used in geology. This method may provide a possibility to determine the composition and concentration of element oxides forming the inorganic part of bones. In this study, we wished to standardize the LIPS technique and use mathematical calculations and models in order to determine CaO distribution and bone homogeneity using bovine shin bone samples. We used polished slices of five bovine shin bones. A portable LIPS instrument using high-power Nd++YAG laser pulses has been developed (OpLab, Budapest). Analysis of CaO distribution was carried out in a 10 × 10 sampling matrix applying 300-μm sampling intervals. We assessed both cortical and trabecular bone areas. Regions of interest (ROI) were determined under microscope. CaO peaks were identified in the 200-500 nm wavelength range. A mathematical formula was used to calculate the element oxide composition (wt%) of inorganic bone. We also applied two accepted mathematical approaches, the Bartlett's test and frequency distribution curve-based analysis, to determine the homogeneity of CaO distribution in bones. We were able to standardize the LIPS technique for bone research. CaO concentrations in the cortical and trabecular regions of B1-5 bones were 33.11 ± 3.99% (range 24.02-40.43%) and 27.60 ± 7.44% (range 3.58-39.51%), respectively. CaO concentrations highly corresponded to those routinely determined by ICP-OES. We were able to graphically demonstrate CaO distribution in both 2D and 3D. We also determined possible interrelations between laser-induced craters and bone structure units, which may reflect the bone structure and may influence the heterogeneity of CaO distributions. By using two different statistical methods, we could confirm if bone samples were homogeneous or not with respect to CaO concentration distribution. LIPS, a technique previously used in geology, may be included in bone research. Assessment of element oxide concentrations in the inorganic part of bone, as well as mathematical calculations may be useful to determine the content of CaO and other element oxides in bone, further analyze bone structure and homogeneity and possibly apply this research to normal, as well as diseased bones.

Sclerostin activity plays a key role in the negative effect of glucocorticoid signaling on osteoblast function in mice

Stress during prenatal development is correlated with detrimental cognitive and behavioral outcomes in offspring. However, the long-term impact of prenatal stress (PS) and disrupted glucocorticoid signaling on bone mass and strength is not understood. In contrast, the detrimental effect of lead (Pb) on skeletal health is well documented. As stress and Pb act on common biological targets via glucocorticoid signaling pathways and co-occur in the environment, this study first sought to assess the combined effect of stress and Pb on bone quality in association with alterations in glucocorticoid signaling. Bone parameters were evaluated using microCT, histomorphometry, and strength determination in 8-month-old male mouse offspring subjected to PS on gestational days 16 and 17, lifetime Pb exposure (100 p.p.m. Pb in drinking water), or to both. Pb reduced trabecular bone mass and, when combined with PS, Pb unmasked an exaggerated decrement in bone mass and tensile strength. Next, to characterize a mechanism of glucocorticoid effect on bone, prednisolone was implanted subcutaneously (controlled-release pellet, 5 mg·kg^-1 per day) in 5-month-old mice that decreased osteoblastic activity and increased sclerostin and leptin levels. Furthermore, the synthetic glucocorticoid dexamethasone alters the anabolic Wnt signaling pathway. The Wnt pathway inhibitor sclerostin has several glucocorticoid response elements, and dexamethasone administration to osteoblastic cells induces sclerostin expression. Dexamethasone treatment of isolated bone marrow cells decreased bone nodule formation, whereas removal of sclerostin protected against this decrement in mineralization. Collectively, these findings suggest that bone loss associated with steroid-induced osteoporosis is a consequence of sclerostin-mediated restriction of Wnt signaling, which may mechanistically facilitate glucocorticoid toxicity in bone.

Age and sex influence on bone and blood lead concentrations in a cohort of the general population living in Toronto

OBJECTIVE

To study the age and sex influence on bone and blood lead concentrations in a cohort of the general population living in Toronto.

APPROACH

A ¹⁰⁹Cd K x-ray fluorescence (KXRF) measurement system was used from 2009 to 2011 in a study that measured the bone lead (Pb) concentration of 263 environmentally exposed individuals residing in Toronto, Ontario, Canada. Tibia (cortical bone) and calcaneus (trabecular bone) lead contents were measured in 134 males and 129 females between 1 and 82 years of age. Whole blood Pb concentration was measured by TIMS (thermal ionization mass spectrometer). Tibia (Ti) and calcaneus (Cal) Pb were examined versus the age of participants, taking into account uncertainties in bone Pb measurement values.

MAIN RESULTS

No significant sex differences were observed in any of the age categories. Participants older than 50 years of age demonstrated the highest concentrations of Pb in their blood, tibia, and calcaneus bones.

SIGNIFICANCE

In most of the previous publications, uncertainty was not considered in the regression model of bone Pb and age. However, in this paper, we adjusted the bone Pb values for the uncertainty level. This had a significant influence in regression models of bone Pb and thus we recommend that uncertainty be considered in future studies.

Repeated conservation threats across the Americas: High levels of blood and bone lead in the Andean Condor widen the problem to a continental scale

Wildlife lead exposure is an increasing conservation threat that is being widely investigated. However, for some areas of the world (e.g., South America) and certain species, research on this subject is still scarce or only local information is available. We analyzed the extent and intensity of lead exposure for a widely distributed threatened species, the Andean Condor (Vultur gryphus). We conducted the study at two different scales: 1) sampling of birds received for rehabilitation or necropsy in Argentina, and 2) bibliographic review and extensive survey considering exposure event for the species' distribution in South America. Wild condors from Argentina (n = 76) presented high lead levels consistent with both recent and previous exposure (up to 104 μg/dL blood level, mean 15.47 ± 21.21 μg/dL and up to 148.20 ppm bone level, mean 23.08 ± 31.39 ppm). In contrast, captive bred individuals -not exposed to lead contamination- had much lower lead levels (mean blood level 5.63 ± 3.08 μg/dL, and mean bone level 2.76 ± 3.06 ppm). Condors were exposed to lead throughout their entire range in continental Argentina, which represents almost sixty percent (>4000 km) of their geographical distribution. We also present evidence of lead exposure events in Chile, Ecuador, and Peru. Lead poisoning is a widespread major conservation threat for the Andean Condor, and probably other sympatric carnivores from South America. The high number and wide range of Andean Condors with lead values complement the results for the California Condor and other scavengers in North America suggesting lead poisoning is a continental threat. Urgent actions are needed to reduce this poison in the wild.

Association between urinary lead and bone health in a general population from Taiwan

Lead accumulates in adult bones for many decades; previous studies have shown lead's detrimental effects on osteoblast and osteoclast activity in association with bone remodeling. Osteoporosis is a disease of the bones resulting in low bone mass that induces fragile bones and hence susceptibility of fracture. We estimated the association between urinary lead (U-Pb) levels and bone health in adults participating in the third Nutrition and Health Survey in Taiwan (NAHSIT) from 2005 to 2008. A total of 398 participants were divided into normal (T-score>-1), osteopenic (T-score between -1 and -2.5), or osteoporotic (T-score<-2.5) groups according to the results of bone mineral density (BMD) measurements. Heavy metals were measured in urine specimens using inductively coupled plasma-mass spectrometry. In the multivariable logistic regression analysis, age (OR=1.08; 95% CI=1.05-1.10), former smokers (OR=2.95; 95% CI=1.22-7.11) and higher U-Pb levels than upper tertile (OR=2.30; 95% CI=1.19-4.48) were associated with osteopenia/osteoporosis. Furthermore, age (OR=1.06; 95% CI=1.02-1.10) and higher U-Pb levels (OR=2.81; 95% CI=1.13-6.97) were significantly associated with osteopenia and osteoporosis in women. These results suggest that adults, particularly in women, with higher U-Pb levels may have increased odds of osteopenia and osteoporosis.

Allogeneic and Autogenous Bone Grafts Are Affected by Historical Donor Environmental Exposure

BACKGROUND

Bone graft materials are routinely evaluated for infectious agents; however, data regarding contamination of bone graft from environmental exposure of the donors to osteotoxic substances such as lead are not routinely available. In animal models, stored lead in bone has been shown to impair fracture healing and osteocyte function. In clinical studies, lead is linked to skeletal disease at relatively low concentrations. Presumably the levels of lead in allografts mirror the level of lead in bone in the population; however, the degree to which processing might decrease this and the frequency with which potentially osteotoxic levels appear in bone grafts have not been studied.

QUESTIONS/PURPOSES

(1) Does processing of donor bone for allografts result in lower concentrations of lead in commercial allograft when compared with autologous bone graft; and (2) what proportion of bone grafts contain potentially osteotoxic levels of lead from > 2.0 to 20.0 µg/g corresponding to environmental exposure?

METHODS

Allograft from commercial sources and autologous bone graft materials were examined for lead content using ICP- atomic absorption spectrophotometric analysis. We analyzed bone graft specimens from 42 donors, including 26 corticocancellous tibial specimens from commercially available bone graft materials and 16 autograft corticocancellous tibial specimens. Lead levels were determined for the cortical (n = 42) and cancellous (n = 42) portions of each specimen. For quality control, all instruments, plastic and glassware, were regularly tested for lead contamination by atomic absorption spectrophotometry throughout the experiments. In addition, spectrophotometer calibration was verified using Standard Reference Material 1486 bone meal (NIST, Gaithersburg, MD, USA). Descriptive statistical analysis was performed using SPSS 20 (SPSS Inc, Chicago, IL, USA). Using these techniques, a lead level > 2 µg/g to 20 µg/g corresponds to some degree of environmental exposure to lead.

RESULTS

With the numbers available in the present study, there were no differences in mean lead level between commercial bone graft materials and autogenous bone graft, 2.1 µg/g (95% confidence interval [CI], 1.6-3.3 µg/g) versus 2.0 µg/g (95% CI, 1.0-4.5 µg/g; p = 0.86). The range for all tested samples varied from < 0.1 to 5.0 µg/g. Likewise, there were no differences in mean lead level between cortical bone grafts, which contained 2.2 µg/g (95% CI, 1.5-3.7 µg/g), and cancellous grafts, which contained 1.9 µg/g (95% CI, 1.2-3.4 µg/g; p = 0.58). Thirty-eight percent (16 of 42) of the specimens had levels between 2.0 µg/g and 20 µg/g within a range expected for individuals with known environmental exposure to lead.

CONCLUSIONS

This study demonstrates that lead is present in up to one-third of tibial allograft and autograft bone specimens at potentially osteotoxic levels regardless of the source or screening. Further research is needed to delineate the relationship with nonunion or pseudoarthrosis after procedures in which allograft is used. In addition, further study would examine concentrations of lead and other environmental contaminants in other graft types.

CLINICAL RELEVANCE

Comparable levels of lead exposure have been associated with toxic effects on skeletal tissue. Further study of bone graft used in fusion procedures and other procedures is necessary to define the magnitude of osteotoxic effects in the setting of fracture care or fusion procedures.

Effects of Combined Exposure to Lead and High-Fat Diet on Bone Quality in Juvenile Male Mice

BACKGROUND

Lead (Pb) exposure and obesity are co-occurring risk factors for decreased bone mass in the young, particularly in low socioeconomic communities.

OBJECTIVES

The goal of this study was to determine whether the comorbidities of Pb exposure and high-fat diet-induced obesity amplify skeletal deficits independently associated with each of these risk factors, and to explore associated mechanisms of the observed deficiencies.

METHODS

Five-week-old male C57BL/6J mice were placed on low-fat (10% kcal, LFD) or high-fat (60% kcal, HFD) diets for 12 weeks. Mice were exposed to lifetime Pb (50 ppm) through drinking water.

RESULTS

HFD was associated with increased body mass and glucose intolerance. Both HFD and Pb increased fasting glucose and serum leptin levels. Pb and HFD each reduced trabecular bone quality and together had a further detrimental effect on these bone parameters. Mechanical bone properties of strength were depressed in Pb-exposed bones, but HFD had no significant effect. Both Pb and HFD altered progenitor cell differentiation, promoting osteoclastogenesis and increasing adipogenesis while suppressing osteoblastogenesis. In support of this lineage shift being mediated through altered Wnt signaling, Pb and non-esterified fatty acids in MC3T3 cells increased in vitro PPAR-γ activity and inhibited β-catenin activity. Combining Pb and non-esterified fatty acids enhanced these effects.

CONCLUSIONS

Pb and HFD produced selective deficits in bone accrual that were associated with alterations in progenitor cell activity that may involve reduced Wnt signaling. This study emphasizes the need to assess toxicants together with other risk factors relevant to human health and disease.

Multiple pathological fractures and delayed union associated with lead exposure in a German Shepherd Dog

CASE REPORT

An 8-year-old 40.8-kg intact male German Shepherd Dog was evaluated for bilateral antebrachial fractures. Radiographs revealed osteopenia and comminuted proximal diaphyseal fractures of the left radius and ulna, and proximal articular fracture of the right ulna. A dual energy X-ray absorptiometry scan confirmed decreased bone mineral density. Bone mineral analysis collected at the time of definitive surgical repair demonstrated high lead concentration. Analysis further demonstrated normal bone calcium and phosphorus concentrations. Serum lead concentration was normal. The left radial and ulnar fractures were surgically stabilised with an external fixator. The right ulnar fracture was splinted. The left antebrachial fractures were palpably unstable at 12 weeks after surgery. Moderate callus formation and incomplete bone union were present at 17 weeks postoperatively. The dog was re-presented 15 months later for right metacarpal and left metatarsal fractures, which were managed conservatively. Complete bone union of the right radial and ulnar fractures was not present at that time.

CONCLUSION

Excessive lead accumulation in bone should be considered as a differential diagnosis for increased susceptibility to pathologic fracture and delayed fracture healing in dogs.

Autophagy plays a protective role in cell death of osteoblasts exposure to lead chloride

Lead (Pb) is a toxic heavy metal widespreadly used in industrial field. Prior studies showed that Pb exposure had detrimental effects on osteoblasts. The mechanisms underlying Pb-induced damage are complex. Autophagy can protect cells from various cytotoxic stimuli. In the present study, the aim of our research was to investigate whether Pb could activate autophagy to play a protective role against osteoblasts apoptosis. Our results indicated that PbCl2 induced autophagy and autophagic flux in MC3T3-E1 murine osteoblastic cell by RT-PCR, western blot, as well as fluorescence microscopy analysis of GFP-LC3, AO and MDC staining. Pb increased the apoptosis of osteoblasts, evidenced by western blot and Hoechst 33258 staining assessment. In addition, inhibiting autophagy by 3-MA further increased the osteoblasts apoptosis after Pb exposure, showed by flow cytometry and Hoechst 33258 staining. Furthermore, phosphorylation of mTOR and p70S6K was inhibited by Pb exposure, indicating that Pb might induce autophagy in osteoblasts via inhibiting mTOR pathway. Altogether, these evidence suggested that Pb exporsure promoted autophagy flux in osteoblasts. The activation of autophagy by Pb played a protective role in osteoblasts apoptosis, which might be mediated through the mTOR pathway.

Ultrasonographic measurement of the femoral cartilage thickness in patients with occupational lead exposure

The objective of the present study is to compare distal femoral cartilage thicknesses of patients with occupational lead exposure with those of healthy subjects by using ultrasonography. A total of 48 male workers (a mean age of 34.8±6.8 years and mean body mass index (BMI) of 25.8±3.1 kg/m(2)) with a likely history of occupational lead exposure and age- and BMI-matched healthy male subjects were enrolled. Demographic and clinical characteristics of the patients, that is, age, weight, height, occupation, estimated duration of lead exposure, and smoking habits were recorded. Femoral cartilage thickness was assessed from the midpoints of right medial condyle (RMC), right lateral condyle (RLC), right intercondylar area (RIA), left medial condyle (LMC), left lateral condyle (LLC), and left intercondylar area (LIA) by using ultrasonography. Although the workers had higher femoral cartilage thickness values at all measurement sites when compared with those of the control subjects, the difference reached statistical significance at RLC (P=0.010), LMC (P=0.001), and LIA (P=0.039). There were no correlations between clinical parameters and cartilage-thickness values of the workers. Subjects with a history of lead exposure had higher femoral cartilage thickness as compared with the healthy subjects. Further studies, including histological evaluations, are awaited to clarify the clinical relevance of this increase in cartilage thickness and to explore the long-term follow-up especially with respect to osteoarthritis development.

Modes of action associated with uranium induced adverse effects in bone function and development

Uranium, a naturally occurring element used in military and industrial applications, accumulates in the skeletal system of animals and humans. Evidence from animal and in-vitro studies demonstrates that uranium exposure is associated with alterations in normal bone functions. The available studies suggest that upon absorption uranium directly affects bone development and maintenance by inhibiting osteoblast differentiation and normal functions, and indirectly by disrupting renal production of Vitamin D. Animal studies also provide evidence for increased susceptibility to uranium-induced bone toxicity during early life stages. The objective of this review is to provide a summary of uranium-induced bone toxicity and the potential mechanisms by which uranium can interfere with bone development and promote fragility. Since normal Vitamin D production and osteoblast functions are essential for bone growth and maintenance, young individuals and the elderly may represent potentially susceptible populations to uranium-induced bone damage.

Fractures Due to Gunshot Wounds: Do Retained Bullet Fragments Affect Union?

BACKGROUND

Many types of projectiles, including modern hollow point bullets, fragment into smaller pieces upon impact, particularly when striking bone. This study was performed to examine the effect on time to union with retained bullet material near a fracture site in cases of gunshot injury.

METHODS

All gunshot injuries operatively treated with internal fixation at a Level 1 Trauma Center between March 2008 and August 2011 were retrospectively reviewed. Retained bullet load near the fracture site was calculated based on percentage of material retained compared to the cortical diameter of the involved bone. Analyses were performed to assess the effect of the lead-cortical ratio and amount of comminution on time to fracture union.

RESULTS

Thirty-two patients (34 fractures) met the inclusion criteria, with an equal number of comminuted (17) and non-comminuted fractures (17). Seventeen of 34 fractures (50%) united within 4 months, 16/34 (47%) developed a delayed union, and 1/34 (3%) developed a nonunion requiring revision surgery. Sixteen of 17 fractures (94%) that united by 4 months had a cumulative amount of bullet fragmentation retained near the fracture site of less than 20% of the cortical diameter. Nine out of 10 fractures (90%) with retained fragments near the fracture site was equal to or exceeding 20% of the cortical diameter had delayed or nonunion. Fracture comminution had no effect on time to union.

CONCLUSIONS

The quantity of retained bullet material near the fracture site was more predictive of the rate of fracture union than was comminution. Fractures with bullet fragmentation equal to or exceeding 20% of the cortical width demonstrated a significantly higher rate of delayed union/nonunion compared to those fractures with less retained bullet material, which may indicate a local cytotoxic effect from lead on bone healing. These findings may influence decisions on timing of secondary surgeries.

LEVEL OF EVIDENCE

Level III.

Factors influencing uncertainties of in vivo bone lead measurement using a (109)Cd K X-ray fluorescence clover leaf geometry detector system

A (109)Cd K X-ray fluorescence (KXRF) measurement system consisting of four detectors in clover-leaf geometry is a non-invasive, low-radiation-dose method of measuring bone lead concentration. Its high precision in estimating the bone lead content makes it a promising tool for the determination of the low levels of lead currently found in the general population. After developing the clover-leaf geometry system, the system was used for the first time in a major survey in 2008 to measure the lead levels of 497 smelter employees (an occupationally exposed group with high lead levels). Since the delivered effective dose of the bone lead system in clover-leaf geometry is small (on the order of nSv), the technique can be used to measure the bone lead of sensitive populations such as the elderly and children. This detector system was used from 2009 to 2011, in a pilot study that measured the bone lead concentration of 263 environmentally exposed individuals (termed the EG group) residing in Toronto, Ontario, Canada. In this paper, the factors that influence uncertainties in lead content in tibia (cortical bone) and calcaneus (trabecular bone) are discussed based on gender, age, and body mass index (BMI) by using analysis of variance (ANOVA) and multiple linear regression models. Results from the two study groups (the EG group versus the occupationally exposed smelter employees) are compared where appropriate (i.e. for males older than 20). Results from univariate analyses showed that females have higher tibia uncertainty compared to males. We observed significant differences for both calcaneus and tibia uncertainty measures (p < 0.0005) among different age groups, where the uncertainties were highest in the lowest age group (<11 years). Lastly, and perhaps most significantly, we found that the product of source activity and measurement time influenced the precision of measurements greatly, and that this factor alone could account for the higher uncertainties observed for the male cohort of the EG group versus the smelter employees.

[Applicability of laser-based geological techniques in bone research: analysis of calcium oxide distribution in thin-cut animal bones]

The structural similarities between the inorganic component of bone tissue and geological formations make it possible that mathematic models may be used to determine weight percentage composition of different mineral element oxides constituting the inorganic component of bone tissue. The determined weight percentage composition can be verified with the determination of element oxide concentration values by laser induced plasma spectroscopy and inductively coupled plasma optical emission spectrometry. It can be concluded from calculated weight percentage composition of the inorganic component of bone tissue and laboratory analyses that the properties of bone tissue are determined primarily by hydroxylapatite. The inorganic bone structure can be studied well by determining the calcium oxide concentration distribution using the laser induced plasma spectroscopy technique. In the present study, thin polished bone slides prepared from male bovine tibia were examined with laser induced plasma spectroscopy in a regular network and combined sampling system to derive the calculated calcium oxide concentration distribution. The superficial calcium oxide concentration distribution, as supported by "frequency distribution" curves, can be categorized into a number of groups. This, as such, helps in clearly demarcating the cortical and trabecular bone structures. Following analyses of bovine tibial bone, the authors found a positive association between the attenuation value, as determined by quantitative computer tomography and the "ρ" density, as used in geology. Furthermore, the calculated "ρ" density and the measured average calcium oxide concentration values showed inverse correlation.

The convergence of fracture repair and stem cells: interplay of genes, aging, environmental factors and disease

The complexity of fracture repair makes it an ideal process for studying the interplay between the molecular, cellular, tissue, and organ level events involved in tissue regeneration. Additionally, as fracture repair recapitulates many of the processes that occur during embryonic development, investigations of fracture repair provide insights regarding skeletal embryogenesis. Specifically, inflammation, signaling, gene expression, cellular proliferation and differentiation, osteogenesis, chondrogenesis, angiogenesis, and remodeling represent the complex array of interdependent biological events that occur during fracture repair. Here we review studies of bone regeneration in genetically modified mouse models, during aging, following environmental exposure, and in the setting of disease that provide insights regarding the role of multipotent cells and their regulation during fracture repair. Complementary animal models and ongoing scientific discoveries define an increasing number of molecular and cellular targets to reduce the morbidity and complications associated with fracture repair. Last, some new and exciting areas of stem cell research such as the contribution of mitochondria function, limb regeneration signaling, and microRNA (miRNA) posttranscriptional regulation are all likely to further contribute to our understanding of fracture repair as an active branch of regenerative medicine.

Inhibition of beta-catenin signaling by Pb leads to incomplete fracture healing

There is strong evidence in the clinical literature to suggest that elevated lead (Pb) exposure impairs fracture healing. Since Pb has been demonstrated to inhibit bone formation, and Wnt signaling is an important anabolic pathway in chondrocyte maturation and endochondral ossification, we investigated the impact of Wnt therapy on Pb-exposed mice undergoing bone repair in a mouse tibial fracture model. We established that tibial fracture calluses from Pb-treated mice were smaller and contained less mineralized tissue than vehicle controls. This resulted in the persistence of immature cartilage in the callus and decreased β-catenin levels. Reduction of β-catenin protein was concurrent with systemic elevation of LRP5/6 antagonists DKK1 and sclerostin in Pb-exposed mice throughout fracture healing. β-catenin stimulation by the GSK3 inhibitor BIO reversed these molecular changes and restored the amount of mineralized callus. Overall, Pb is identified as a potent inhibitor of endochondral ossification in vivo with correlated effects on bone healing with noted deficits in β-catenin signaling, suggesting the Wnt/β-catenin as a pivotal pathway in the influence of Pb on fracture repair.

Lead exposure is a risk for worsening bone mineral density in middle-aged male workers

OBJECTIVE

Lead exposure linked to osteoporosis in women. However, there is no direct evidence whether lead exposure has effects on bone metabolism in middle-aged male subjects. Therefore, the present study investigated the relationship between bone mineral densitometry measurements, bone markers, endocrine hormones and blood lead levels.

MATERIAL AND METHODS

The present study included lead exposure patients (n: 30) and control subjects (n: 32). We recorded information on patient demographics and risk factors of osteoporosis. Blood lead levels were evaluated using Varian AA 240Z atomic absorption spectrophotometry. Bone mineral density measurements were measured using dual-energy X-ray absorptiometry.

RESULTS

Each lumbar T and Z scores in the lead exposure group were lower than the control group. There were no significant differences in femur neck and femur total T and Z scores between two groups. Blood lead levels were also negatively correlated with lumbar 2-4 T score, total lumbar T score, lumbar 2-4 Z score and total lumbar Z score. Urinary hydroxyproline and urinary deoxypyridinoline levels in the lead exposure group were significantly higher compared to controls. Blood lead levels were strong, positively correlated with urinary deoxypyridinoline. Endocrine hormone levels and 1,25-dihydroxy-vitamin D3 levels were comparable between lead exposure and control group.

CONCLUSION

Lead exposure in male workers is an important factor for deterioration in bone mineral density. We should be screening blood lead levels and history of lead exposure in male osteoporosis.

Lead-induced morphological changes and amyloid precursor protein accumulation in adult rat hippocampus

Lead is an important environmental pollutant that exerts potent toxic effects on many organs. The toxic effects of lead are less well known for adult brain than for children. We investigated the morphological changes and amyloid precursor protein (APP) accumulation in the adult rat hippocampus following exposure to lead. Forty rats were divided into two groups of 20. One group was exposed to 580 parts per million (ppm) lead acetate and other group to an identical concentration of sodium acetate as a control group. After exposure to lead for 3 months, the hippocampus was examined by electron microscopy and APP levels in the hippocampus were detected using immunohistochemistry. Lead levels in the blood of rats exposed to lead were significantly higher than in the controls. The morphological changes in the hippocampus included mitochondrial degeneration, apoptosis and abnormal synapses in the rats exposed to lead. APP in hippocampus was increased significantly in the group exposed to lead compared to controls. We determined that lead exposure causes accumulation of APP and morphological changes in the adult rat hippocampus.