Lead induces chondrogenesis and alters transforming growth factor-beta and bone morphogenetic protein signaling in mesenchymal cell populations

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.

Naringenin alleviate reproductive toxicity evoked by lead acetate via attenuation of sperm profile and biochemical alterations in male Wistar rat: Involvement of TGFβ/AKT/mTOR pathway

Exposure to Lead -causes testicular dysfunction through oxidative stress, inflammation, and apoptosis; however, naringenin (NGN) therapeutic impact against lead-evoked testicular dysfunction remains elusive. Herein, the point of the study was to examine the defensive impact of NGN on testicular dysfunction initiated by lead. Seventy-Two male Wistar rats were allotted into nine groups; control group, drug control groups, lead acetate group, as well as NGN treated groups (10, 25, and 50 mg/kg) respectively, given 5 days before lead acetate treatment. The result showed clearly the impact of lead on reduced sperm count, sperm motility as well as serum testosterone and LH levels. Additionally, it caused a significant rise in testicular inflammatory markers TNF-α, IL-1β, and TGFβ, effects that were accompanied by a reduction of AKT and mTOR levels. Lead acetate also caused degenerative changes in the testis, atrophy, and loss of spermatogenic series. Our findings revealed that NGN in a dose-dependent manner improved spermiotoxicity induced by lead acetate via restoration of the testicular function, preservation of spermatogenesis, halting inflammatory cytokines along with the enhancement of germ cell survival using upregulation of AKT/mTOR expressions. The present study discloses that NGN suppresses lead acetate toxicity that is involved in the antioxidant effect in a dose-dependent manner, besides its anti-inflammatory property.

Prenatal lead (Pb) exposure is associated with differential placental DNA methylation and hydroxymethylation in a human population

Prenatal lead (Pb) exposure is associated with adverse developmental outcomes and to epigenetic alterations such as DNA methylation and hydroxymethylation in animal models and in newborn blood. Given the importance of the placenta in foetal development, we sought to examine how prenatal Pb exposure was associated with differential placental DNA methylation and hydroxymethylation and to identify affected biological pathways linked to developmental outcomes. Maternal (n = 167) and infant (n = 172) toenail and placenta (n = 115) samples for prenatal Pb exposure were obtained from participants in a US birth cohort, and methylation and hydroxymethylation data were quantified using the Illumina Infinium MethylationEPIC BeadChip. An epigenome-wide association study was applied to identify differential methylation and hydroxymethylation associated with Pb exposure. Biological functions of the Pb-associated genes were determined by overrepresentation analysis through ConsensusPathDB. Prenatal Pb quantified from maternal toenail, infant toenail, and placenta was associated with 480, 27, and 2 differentially methylated sites (q < 0.05), respectively, with both increases and decreases associated with exposure. Alternatively, we identified 2, 1, and 14 differentially hydroxymethylated site(s) associated with maternal toenail, infant toenail, and placental Pb, respectively, with most showing increases in hydroxymethylation with exposure. Significantly overrepresented pathways amongst genes associated with differential methylation and hydroxymethylation (q < 0.10) included mechanisms pertaining to nervous system and organ development, calcium transport and regulation, and signalling activities. Our results suggest that both methylation and hydroxymethylation in the placenta can be variable based on Pb exposure and that the pathways impacted could affect placental function.

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.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

Environmental metal exposure and growth to 10 years of age in a longitudinal mother-child cohort in rural Bangladesh

BACKGROUND

Early-life exposure to arsenic (As), cadmium (Cd), and lead (Pb) has been linked to smaller birth and early childhood anthropometry, but little is known beyond the first years in life.

OBJECTIVES

To evaluate the impact of gestational and childhood exposures to As, Cd, and Pb on growth up to 10 years of age.

METHODS

We studied 1530 mother-child dyads from a nested sub-cohort of the MINIMat trial in rural Matlab, Bangladesh. Metal concentrations in maternal erythrocytes during pregnancy and in children's urine at 10y were measured by inductively coupled plasma mass spectroscopy. Child height and weight were measured at 19 occasions from birth until 10y and converted to height-for-age Z-scores (HAZ) and weight-for-age Z-scores (WAZ). Associations between log₂-transformed metal concentrations and growth parameters were assessed with multivariable-adjusted regression models.

RESULTS

Children's concurrent urinary Cd (median 0.24 µg/L), reflecting long-term exposure, was inversely associated with WAZ (B: -0.072; 95% confidence interval (CI): -0.12, -0.020; p = 0.007), and possibly HAZ (B: -0.046; 95% CI: -0.096, 0.0014; p = 0.057), at 10y. The association with WAZ was stronger in boys than in girls. Maternal erythrocyte Cd (median 0.90 µg/kg) during pregnancy was inversely associated with WAZ during childhood only in boys (B: -0.071, 95% CI: -0.14, -0.0047, p = 0.036). Concurrent urinary Pb (median 1.6 µg/L) was inversely associated with WAZ (B: -0.084; 95% CI: -0.16, -0.0085; p = 0.029) and HAZ (B: -0.087; 95% CI: -0.15, -0.021; p = 0.010) in boys, but not in girls. Neither gestational nor childhood As exposure (median maternal erythrocyte As 4.3 µg/kg and children's urinary As 57 µg/L) was associated with growth up to 10y.

CONCLUSIONS

While all effect estimates were small, environmental exposure to Cd and Pb is common and impaired growth is of public health concern, especially for children already at risk of reduced growth due to malnutrition. Gender differences in susceptibility need further investigation.

Environmental Exposure to Heavy Metals Contributes to Diseases Via Deregulated Wnt Signaling Pathways

Wnt signaling plays a critical role during embryogenesis and is responsible for regulating the homeostasis of the adult stem cells and cells fate via a multitude of signaling pathways and associated transcription factors, receptors, effectors, and inhibitors. For this review, published articles were searched from PubMed Central, Embase, Medline, and Google Scholar. The search terms were Wnt, canonical, noncanonical, signaling pathway, β-catenin, environment, and heavy metals. Published articles on Wnt signaling pathways and heavy metals as contributing factors for causing diseases via influencing Wnt signaling pathways were included. Wnt canonical or noncanonical signaling pathways are the key regulators of stem cell homeostasis that control many mechanisms. There is an adequate balance between β-catenin dependent and independent Wnt signaling pathways and remain highly conserved throughout different development stages. Environmental heavy metal exposure may cause either inhibition or overexpression of any component of Wnt signaling pathways such as Wnt protein, transcription factors, receptors, ligands, or transducers to impede normal cellular function via negatively affecting Wnt signaling pathways. Environmental exposure to heavy metals potentially contributes to diseases via deregulated Wnt signaling pathways. 

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.].

Impact of Coenzyme Q10 Administration on Lead Acetate-Induced Testicular Damage in Rats

Exposure to lead (Pb) causes multiorgan dysfunction including reproductive impairments. Here, we examined the protective effects of coenzyme Q10 (CoQ10) administration on testicular injury induced by lead acetate (PbAc) exposure in rats. This study employed four experimental groups (n = 7) that underwent seven days of treatment as follows: control group intraperitoneally (i.p.) treated with 0.1 ml of 0.9% NaCl containing 1% Tween 80 (v : v), CoQ10 group that was i.p. injected with 10 mg/kg CoQ10, PbAc group that was i.p. treated with PbAc (20 mg/kg), and PbAc+CoQ10 group that was i.p. injected with CoQ10 2 h after PbAc. PbAc injection resulted in increasing residual Pb levels in the testis and reducing testosterone, luteinizing hormone, and follicle-stimulating hormone levels. Additionally, PbAc exposure resulted in significant oxidative damage to the tissues on the testes. PbAc raised the levels of prooxidants (malondialdehyde and nitric oxide) and reduced the amount of endogenous antioxidative proteins (glutathione and its derivative enzymes, catalase, and superoxide dismutase) available in the cell. Moreover, PbAc induced the inflammatory response as evidenced by the upregulation of inflammatory mediators (tumor necrosis factor-alpha and interleukin-1 beta). Further, PbAc treatment induced apoptosis in the testicular cells, as indicated by an increase in Bax and caspase 3 expression, and reduced Bcl2 expression. CoQ10 supplementation improved testicular function by inhibiting Pb accumulation, oxidative stress, inflammation, cell death, and histopathological changes following PbAc exposure. Our findings suggest that CoQ10 can act as a natural therapeutic agent to protect against the reproductive impairments associated with PbAc exposure.

An epigenome-wide DNA methylation study of workers with an occupational exposure to lead

Using the Illumina Infinium Methylation EPIC BeadChip (850 K), we report genome-wide differences in DNA methylation between occupational workers with high blood Pb levels (BLL) and low BLL. We observed 356 significant CpG sites. In particular, GSTM1 methylation was negatively associated with high BLL. Gene ontology and KEGG pathway enrichment analysis were performed to determine the complex biological systems of Pb exposure. Enriched gene sets were involved in the oxidation-reduction process, glutathione derivative biosynthetic process and nervous system development. To our knowledge, this is the first study to employ an 850 K array to examine whether workers with occupational exposure to high levels of Pb can have an epigenetic effect on the DNA methylation pattern.

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.

Elevated Lifetime Lead Exposure Impedes Osteoclast Activity and Produces an Increase in Bone Mass in Adolescent Mice

The heavy metal lead (Pb) has a deleterious effect on skeletal health. Because bone mass is maintained through a balance of bone formation and resorption, it is important to understand the effect of Pb levels on osteoblastic and osteoclastic activity. Pb exposure is associated with low bone mass in animal models and human populations; however, the correlation between Pb dosing and corresponding bone mass has been poorly explored. Thus, mice were exposed to increasing Pb and at higher levels (500 ppm), there was unexpectedly an increase in femur-tibial bone mass by 3 months of age. This is contrary to several studies alluded to earlier. Increased bone volume (BV) was accompanied by a significant increase in cortical thickness of the femur and trabecular bone that extended beyond the epiphyseal area into the marrow cavity. Subsequent evaluations revealed an increase in osteoclast numbers with high Pb exposure, but a deficiency in osteoclastic activity. These findings were substantiated by observed increases in levels of the resorption-altering hormones calcitonin and estrogen. In addition we found that pro-osteoclastic nuclear factor-kappa beta (NF-κB) pathway activity was dose dependently elevated with Pb, both in vivo and in vitro. However, the ability of osteoclasts to resorb bone was depressed in the presence of Pb in media and within test bone wafers. These findings indicate that exposure to high Pb levels disrupts early life bone accrual that may involve a disruption of osteoclast activity. This study accentuates the dose dependent variation in Pb exposure and consequent effects on skeletal health.

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.

Effects of thirty elements on bone metabolism

The human skeleton, made of 206 bones, plays vital roles including supporting the body, protecting organs, enabling movement, and storing minerals. Bones are made of organic structures, intimately connected with an inorganic matrix produced by bone cells. Many elements are ubiquitous in our environment, and many impact bone metabolism. Most elements have antagonistic actions depending on concentration. Indeed, some elements are essential, others are deleterious, and many can be both. Several pathways mediate effects of element deficiencies or excesses on bone metabolism. This paper aims to identify all elements that impact bone health and explore the mechanisms by which they act. To date, this is the first time that the effects of thirty minerals on bone metabolism have been summarized.

Suppression of Nkx3.2 by phosphatidylinositol-3-kinase signaling regulates cartilage development by modulating chondrocyte hypertrophy

Phosphatidylinositol-3-kinase (PI3K) is a key regulator of diverse biological processes including cell proliferation, migration, survival, and differentiation. While a role of PI3K in chondrocyte differentiation has been suggested, its precise mechanisms of action are poorly understood. Here we show that PI3K signaling can down-regulate Nkx3.2 at both mRNA and protein levels in various chondrocyte cultures in vitro. In addition, we have intriguingly found that p85β, not p85α, is specifically employed as a regulatory subunit for PI3K-mediated Nkx3.2 suppression. Furthermore, we found that regulation of Nkx3.2 by PI3K requires Rac1-PAK1, but not Akt, signaling downstream of PI3K. Finally, using embryonic limb bud cultures, ex vivo long bone cultures, and p85β knockout mice, we demonstrated that PI3K-mediated suppression of Nkx3.2 in chondrocytes plays a role in the control of cartilage hypertrophy during skeletal development in vertebrates.

Lead Induces Apoptosis and Histone Hyperacetylation in Rat Cardiovascular Tissues

Acute and chronic lead (Pb) exposure might cause hypertension and cardiovascular diseases. The purpose of this study was to evaluate the effects of early acute exposure to Pb on the cellular morphology, apoptosis, and proliferation in rats and to elucidate the early mechanisms involved in the development of Pb-induced hypertension. Very young Sprague-Dawley rats were allowed to drink 1% Pb acetate for 12 and 40 days. Western blot analysis indicated that the expression of proliferating cell nuclear antigen (PCNA) decreased in the tissues of the abdominal and thoracic aortas and increased in the cardiac tissue after 12 and 40 days of Pb exposure, respectively. Bax was upregulated and Bcl-2 was downregulated in vascular and cardiac tissues after 40 days of Pb exposure. In addition, an increase in caspase-3 activity was observed after 40 days of exposure to Pb. In terms of morphology, we found that the internal elastic lamina (IEL) of aorta lost the original curve and the diameter of cardiac cell was enlarged after 40 days. Furthermore, the exposure led to a marked increase in acetylated histone H3 levels in the aortas and cardiac tissue after 12 and 40 days, than that in the control group. These findings indicate that Pb might increase the level of histone acetylation and induce apoptosis in vascular and cardiac tissues. However, the mechanism involved need to be further investigated.

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.

Mangiferin reduces the inhibition of chondrogenic differentiation by IL-1β in mesenchymal stem cells from subchondral bone and targets multiple aspects of the Smad and SOX9 pathways

Mangiferin is a natural immunomodulator found in plants including mango trees. The effects of mangiferin on chondrogenesis and cartilage repair have not yet been reported. This study was designed to determine the effect of mangiferin on chondrogenic differentiation in IL-1β-stimulated mesenchymal stem cells (MSCs) from subchondral bone and to explore the mechanisms underlying these effects. MSCs were isolated from the subchondral bone of rabbit and treated with mangiferin alone and/or interleukin-1β (IL-1β). Mangiferin induced chondrogenic differentiation in MSCs by upregulating transforming growth factor (TGF)-β, bone morphogenetic protein (BMP)-2, and BMP-4 and several key markers of chondrogenesis, including sex-determining region Y-box (SRY-box) containing gene 9 (SOX9), type 2α1 collagen (Col2α1), cartilage link protein, and aggrecan. In IL-1β-stimulated MSCs, mangiferin significantly reversed the production of TGF-β, BMP-2, BMP-4, SOX9, Col2α1, cartilage link protein, and aggrecan, as well as matrix metalloproteinase (MMP)-1, MMP-13, and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS5). Mangiferin upregulated the phosphorylation of Smad 2, Smad 3, Smad 1/5/8, and SOX9 in IL-1β-stimulated MSCs. In the presence of mangiferin, SOX9 siRNA suppressed the activation of Smad 2, Smad 3, Smad 1/5/8, aggrecan, and Col2α1 expression. In conclusion, mangiferin exhibits both chondrogenic and chondroprotective effects on damaged MSCs and mediates these effects by targeting multiple aspects of the Smad and SOX9 signaling pathways.

Diverse effects of lead nitrate on the proliferation, differentiation, and gene expression of stem cells isolated from a dental origin

Lead (Pb²⁺) exposure continues to be a significant public health problem. Therefore, it is vital to have a continuous epidemiological dataset for a better understanding of Pb²⁺ toxicity. In the present study, we have exposed stem cells isolated from deciduous and permanent teeth, periodontal ligament, and bone marrow to five different types of Pb²⁺ concentrations (160, 80, 40, 20, and 10 µM) for 24 hours to identify the adverse effects of Pb²⁺ on the proliferation, differentiation, and gene expression on these cell lines. We found that Pb²⁺ treatment altered the morphology and adhesion of the cells in a dose-dependent manner. There were no significant changes in terms of cell surface phenotypes. Cells exposed to Pb²⁺ continued to differentiate into chondrogenesis and adipogenesis, and a severe downregulation was observed in osteogenesis. Gene expression studies revealed a constant expression of key markers associated with stemness (Oct 4, Rex 1) and DNA repair enzyme markers, but downregulation occurred with some ectoderm and endoderm markers, demonstrating an irregular and untimely differentiation trail. Our study revealed for the first time that Pb²⁺ exposure not only affects the phenotypic characteristics but also induces significant alteration in the differentiation and gene expression in the cells.

Early chronic low-level lead exposure produces glomerular hypertrophy in young C57BL/6J mice

Early chronic lead exposure continues to pose serious health risks for children, particularly those living in lower socioeconomic environments. This study examined effects on developing glomeruli in young C57BL/6J mice exposed to low (30 ppm), higher (330 ppm) or no lead via dams' drinking water from birth to sacrifice on post-natal day 28. Low-level lead exposed mice [BLL mean (SD); 3.19 (0.70) μg/dL] had an increase in glomerular volume but no change in podocyte number compared to control mice [0.03 (0.01) μg/dL]. Higher-level lead exposed mice [14.68 (2.74) μg/dL] had no change in either glomerular volume or podocyte number. The increase in glomerular volume was explained by increases in glomerular capillary and mesangial volumes with no change in podocyte volume. Early chronic lead exposure yielding very low blood lead levels alters glomerular development in pre-adolescent animals.

Effects of lead and cadmium exposure from electronic waste on child physical growth

Many studies indicate that lead (Pb) and cadmium (Cd) exposure may alter bone development through both direct and indirect mechanisms, increasing the risk of osteoporosis later in life. The aim of this study was to investigate the association between Pb and Cd exposure, physical growth, and bone and calcium metabolism in children of an electronic waste (e-waste) processing area. We recruited 246 children (3-8 years) in a kindergarten located in Guiyu, China. Blood lead levels (BLLs) and blood cadmium levels (BCLs) of recruited children were measured as biomarkers for exposure. Serum calcium, osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline were used as biomarkers for bone and calcium metabolism. Physical indexes such as height, weight, and head and chest circumference were also measured. The mean values of BLLs and BCLs obtained were 7.30 μg/dL and 0.69 μg/L, respectively. The average of BCLs increased with age. In multiple linear regression analysis, BLLs were negatively correlated with both height and weight, and positively correlated with bone resorption biomarkers. Neither bone nor calcium metabolic biomarkers showed significant correlation with cadmium. Childhood lead exposure affected both physical development and increased bone resorption of children in Guiyu. Primitive e-waste recycling may threaten the health of children with elevated BLL which may eventually cause adult osteoporosis.

Investigating the effect of lead acetate on rat bone marrow-derived mesenchymal stem cells toxicity: role of apoptosis

Lead exposure continues to be a significant public health problem. Osteoporosis, inhibition of fracture healing, and cartilage functional impairment have been reported from lead exposure. Mesenchymal stem cells (MSCs) are a bone marrow population of cells with the ability to differentiate into various cell types, particularly osteocytes and chondrocytes. Despite intensive investigation on the effect of lead poisoning on various cell types, there is very little if any report on the effect of lead on MSCs. The aim of this study, therefore, was to investigate the effect of lead acetate on rat bone marrow derived MSCs toxicity and its mechanism by examining the role of pro- and anti-apoptotic proteins in this process. It was revealed that lead acetate could induce cell death in a dose-dependent manner using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium (MTT) assay. Compared to controls, the significant over-expression of pro-apoptotic proteins, including Bax, caspases-9, -3, and p53, with no significant change in anti-apoptotic Bcl(2) protein were obtained in lead-treated cells using western blotting analysis. There was a significant increase in DNA fragmentation in treated MSCs compared to controls using flow-cytometry. Finally, it might be concluded that lead acetate could induce cell toxicity and apoptosis in MSCs, causing instability in mitochondria and in turn activation of the intrinsic pathway including over-expression of Bax, caspase 9 and caspase 3, leading to DNA damage and activation of P53.

Regulation of chondrogenesis and chondrocyte differentiation by stress

Chondrogenesis and endochondral ossification are the cartilage differentiation processes that lead to skeletal formation and growth in the developing vertebrate as well as skeletal repair in the adult. The exquisite regulation of these processes, both in normal development and in pathologic situations, is impacted by a number of different types of stress. These include normal stressors such as mechanical loading and hypoxia as well pathologic stressors such as injury and/or inflammation and environmental toxins. This article provides an overview of the processes of chondrogenesis and endochondral ossification and their control at the molecular level. A summary of the influence of the most well-understood normal and pathologic stressors on the differentiation program is also presented.