Morphological changes of the cartilage and bone in newborn piglets evoked by experimentally induced glucocorticoid excess during pregnancy

Long term usage of dexamethasone accelerating accelerates the initiation of osteoarthritis via enhancing chondrocyte apoptosis and the extracellular matrix calcification and apoptosis of chondrocytes

Systemic application of glucocorticoids is an essential anti-inflammatory and immune-modulating therapy for severe inflammatory or autoimmunity conditions. However, its long-term effects on articular cartilage of patients' health need to be further investigated. In this study, we studied the effects of dexamethasone (Dex) on the homeostasis of articular cartilage and the progress of destabilization of medial meniscus (DMM)-induced osteoarthritis (OA) in adult mice. Long-term administration of Dex aggravates the proteoglycan loss of articular cartilage and drastically accelerates cartilage degeneration under surgically induced OA conditions. In addition, Dex increases calcium content in calcified cartilage layer of mice and the samples from OA patients with a history of long-term Dex treatment. Moreover, long term usage of Dex results in decrease subchondral bone mass and bone density. Further studies showed that Dex leads to calcification of extracellular matrix of chondrocytes partially through activation of AKT, as well as promotes apoptosis of chondrocytes in calcified cartilage layer. Besides, Dex weakens the stress-response autophagy with the passage of time. Taken together, our data indicate that long-term application of Dex may predispose patients to OA and or even accelerate the OA disease progression development of OA patients.

β-Hydroxy-β-Methylbutyrate (HMB) Supplementation Prevents Bone Loss during Pregnancy-Novel Evidence from a Spiny Mouse (Acomys cahirinus) Model

The aim of this study was to determine the effects of ß-hydroxy-ß-methylbutyrate (HMB) supplementation during pregnancy on postpartum bone tissue quality by assessing changes in trabecular and compact bone as well as in hyaline and epiphyseal cartilage. The experiment was carried out on adult 6-month-old female spiny mice (Acomys cahirinus) divided into three groups: pregnant control (PregCont), pregnant HMB-treated (supplemented with 0.02 g/kg b.w of HMB during the second trimester of pregnancy, PregHMB), and non-pregnant females (NonPreg). Cross-sectional area and cortical index of the femoral mid-shaft, stiffness, and Young modulus were significantly greater in the PregHMB group. Whole-bone mineral density was similar in all groups, and HMB supplementation increased trabecular number. Growth plate cartilage was the thinnest, while the articular cartilage was the thickest in the PregHMB group. HMB supplementation increased the content of proteoglycans in the articular cartilage and the percentage of immature collagen content in metaphyseal trabeculae and compact bone. In summary, dietary HMB supplementation during the second trimester of pregnancy intensifies bone metabolic processes and prevents bone loss during pregnancy.

The effect of maternal HMB supplementation on bone mechanical and geometrical properties, as well as histomorphometry and immunolocalization of VEGF, TIMP2, MMP13, BMP2 in the bone and cartilage tissue of the humerus of their newborn piglets

The presented experiment focuses on assessing the impact of HMB (hydroxy-β-methobutyrate) supplementation of mothers during pregnancy on the development of the skeletal system of their offspring. For this purpose, an experiment was carried out on 12 clinically healthy sows of the Great White Poland breed, which were divided randomly into two groups the control and the HMB group. All animals were kept under standard conditions and received the same feed for pregnant females. In contrast, females from the HMB group between 70 and 90 days were supplemented with 3-hydroxy-3-methylbutyle in the amount of 0.2g/kg b.w/day. Immediately after birth, the piglets were also divided into groups based on: sex, and presence or lack HMB supplementation, and subsequently were euthanized and humerus bones from all piglets were collected. Mother's HMB supplementation during pregnancy affected the multiple index of their offspring. The higher humerus mass and length was observed with the greater effect in males. Maternal supplementation also influenced on the geometrical and mechanical properties of the humerus as in the case of mass, this effect was higher in males. Also, the collagen structure of the compacted and trabecular bone changed under the HMB addition. Maternal supplementation also affected the expression of selected proteins in growth cartilage and trabecular bone. The obtained results show that the administration to the mother during pregnancy by the HMB significantly affects the development of the humerus in many ways. The obtained results also confirm the utility of such experiments in understanding of the importance of the pregnancy diet as an develop and adaptable factor of offspring organisms and are the base for further research in that area as well as in the protein markers expression area.

The Protective Role of Alpha-Ketoglutaric Acid on the Growth and Bone Development of Experimentally Induced Perinatal Growth-Retarded Piglets

The effect of alpha-ketoglutaric acid (AKG) supplementation to experimentally-induced, perinatal growth-retarded piglets was examined. Sows were treated with a synthetic glucocorticoid (Gc) during the last 25 days of pregnancy, and after the birth, piglets were randomly divided into three groups depending on the treatment. The Gc/Gc + AKG and Gc/AKG groups born by Gc-treated sows after the birth were treated with Gc or Gc + AKG for 35 days. Significantly lower serum growth hormone, IGF-I, osteocalcin, leptin, and cortisol concentrations were observed in the Gc/Gc + AKG group, while the bone alkaline phosphatase activity was significantly higher. Serum insulin concentration was higher in the control group. Serum alanine, lysine, histidine, and tryptophan concentrations were higher in the Gc/Gc + AKG and Gc/AKG groups. The perinatal action of Gc significantly affects histomorphometry of articular cartilage and trabecular bone and bone mechanics. The results clearly showed that dietary AKG had positive effects with regards to the profile of free amino acids. Taking into account the function of AKG as an energy donor and stimulator of collagen synthesis, it can be concluded that the anabolic role of AKG may be the main mechanism responsible for its protective effect against the GC-induced perinatal intensified catabolic state.

Low-activity programming of the PDGFRβ/FAK pathway mediates H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring rats after prenatal dexamethasone exposure

Dexamethasone is a common synthetic glucocorticoid drug that can promote foetal lung maturity. An increasing number of studies have shown that prenatal dexamethasone exposure (PDE) can cause a variety of short-term and long-term hazards to offspring, including bone development toxicity. H-type vessels are a newly discovered subtype of blood vessels associated with promoted bone formation and maintenance of bone mass. In this study, we aimed to explore whether H-type blood vessels are involved in PDE-induced long bone development toxicity in offspring and its mechanism. In vivo, we injected dexamethasone (0.2 mg/kg.d) subcutaneously at gestational days 9-20 and observed the H-type vessel abundance and bone mass at different time points in the offspring rats. In vitro, we investigated the effect of dexamethasone (0, 20, 100, and 500 nM) on the tube formation function of rat bone marrow-derived endothelial progenitor cells (EPCs) and explored its mechanism. Our results showed that the adult PDE female offspring rats were susceptible to osteoporosis. In addition, PDE inhibited bone mass, H-type vessel formation and the expression of bone platelet-derived growth factor receptor β (PDGFRβ)/focal adhesion kinase (FAK) pathway-related genes in antenatal and postnatal female offspring. Moreover, PDE promoted the expression of bone glucocorticoid receptor (GR), CCAAT and enhancer binding protein α (C/EBPα) and miR-34c in female foetuses. Dexamethasone suppressed the tube formation of rat bone marrow-derived EPCs and the activity of the PDGFRβ/FAK pathway, which was mediated by GR/C/EBPα/miR-34c signalling activation. In summary, PDE can cause H-type vessel dysplasia and high susceptibility to osteoporosis in female offspring, and its mechanism is related to the low-activity programming of the PDGFRβ/FAK pathway induced by GR/C/EBPα/miR-34c signalling activation. This study enhances the understanding of the molecular mechanism of dexamethasone-induced bone development toxicity and provides new insights for exploring the early intervention and therapeutic targets of foetal-derived osteoporosis.

Antenatal Corticosteroid Therapy Attenuates Angiogenesis Through Inhibiting Osteoclastogenesis in Young Mice

Antenatal corticosteroid therapy (ACT) has been shown to reduce morbidity and mortality rates in preterm delivery, but the fetus is more likely to face the risk of low bone mineralization and low fetal linear growth. However, the mechanism of ACT inducing low bone mineralization remains largely unknown. Pre-osteoclasts, which play an important role in angiogenesis and osteogenesis, are specifically regulating type H vessels (CD31^hiEmcn^hi) and vessel formation by secreting platelet-derived growth factor-BB (PDGF-BB). We find that the number of pre-osteoclasts and POC-secreted PDGF-BB is dramatically decreased in ACT mice, contributing to the reduction in type H vessels and bone mineralization during the mouse offspring. Quantitative analyses of micro-computed tomography show that the ACT mice have a significant reduction in the mass of trabecular bone relative to the control group. Mononuclear pre-osteoclasts in trabecular bone decreased in ACT mice, which leads to the amount of PDGF-BB reduced and attenuates type H vessel formation. After sorting the Rank+ osteoclast precursors using flow cytometry, we show that the enhancer of zeste homolog 2 (Ezh2) expression is decreased in Rank+ osteoclast precursors in ACT mice. Consistent with the flow data, by using small molecule Ezh2 inhibitor GSK126, we prove that Ezh2 is required for osteoclast differentiation. Downregulating the expression of Ezh2 in osteoclast precursors would reduce PDGF-BB production. Conditioned medium from osteoclast precursor cultures treated with GSK126 inhibited endothelial tube formation, whereas conditioned medium from vehicle group stimulated endothelial tube formation. These results indicate Ezh2 expression of osteoclast precursors is suppressed after ACT, which reduced the pre-osteoclast number and PDGF-BB secretion, thus inhibiting type H vessel formation and ACT-associated low bone mineralization.

Acrylamide-Induced Prenatal Programming of Bone Structure in Mammal Model

Acrylamide (AA) is a chemical substance with a potentially carcinogenic effect. Its presence in food or animal food arises from its thermal processing. The experiment was conducted to evaluate the effect of AA exposure (3.0 mg/kg. b.w./day) of pregnant dams during the second half of the pregnancy on bone development in offspring. As an model animal, guinea pig was used. While term body weight of newborns was not influenced by maternal AA treatment, shorter bones with reduced bone diaphysis cross-sectional area were observed in experimental group. Numerous negative, offspring sex-dependent effects of maternal AA exposure were observed in femoral epiphysis and metaphysis as well as the articular and growth plate cartilages. These effects resulted from the AA-induced alterations in bone metabolism, as indicated by the changes in the expression of numerous proteins involved in bone development: receptor activator of nuclear factor kappa-Β ligand (RANKL), tissue inhibitor of metalloproteinases 2 (TIMP-2), bone morphogenetic protein 2 (BMP-2), vascular endothelial growth factor (VEGF), and cartilage oligomeric matrix protein (COMP), all of whose expression was measured as well as distribution of immature collagen fibres was determined. Based on the results, it can be concluded that the exposure of pregnant dams to AA negatively affected the structure of compact bone in bone diaphysis, microarchitecture of trabecular bone in metaphysis and epiphysis as well as the structure of the articular and growth plate cartilages in their offspring. The AA-induced bone impairment increased osteoclast differentiation, as observed through the change in the RANKL/OPG ratio, which in turn inhibited osteoblast function by decreasing the expression of other proteins. The data of the present study suggests that maternal AA exposure can result in insufficient bone gain and even bone loss after the birth.

GR/Sp3/HDAC1/UGDH signaling participated in the maternal dexamethasone-induced dysplasia of the rat fetal growth plate

Maternal dexamethasone decreases the body length of the newborn. However, whether dexamethasone inhibits the development of the growth plate of the fetal long bone is still unknown. Here, we found that lengths of fetal femur and growth plate were both shorter in the fetuses with maternal dexamethasone (0.2 mg/kg.d from gestation day 9 to 20), with a decreased proteoglycan content of the growth plate in the fetal rat. Notable decreases in both the gene expression and H3K9 acetylation of UDP-glucose dehydrogenase (Ugdh) gene, which codes a key enzyme in the proteoglycan biosynthesis in the chondrocyte, were also observed. Meanwhile, up-regulation of glucocorticoid receptor (GR), specific protein 3 (Sp3), and histone deacetylase 1 (Hdac1) gene expression were detected in the fetal growth plate. Similar changes were also observed in the chondrogenic rat bone marrow stromal cells (BMSCs) with excessive exogenous dexamethasone. However, antagonizing GR with RU486 and silencing Hdac1 or Sp3 with specific siRNAs could all stimulate the H3K9 acetylation and gene expression of Ugdh previously inhibited by dexamethasone. Meanwhile, dexamethasone also induced the nuclear translocation of GR, which further directly bound to the Ugdh promoter and interacted with HDAC1 and Sp3, respectively. Collectively, our study revealed that maternal dexamethasone induced the direct binding of GR to the Ugdh promoter of the chondrocyte in the rat fetal growth plate, which recruited HDAC1 and Sp3, induced deacetylation of the H3K9, and subsequently inhibited Ugdh gene expression. Such changes further led to attenuated proteoglycan synthesis in the developing chondrocyte and therefore disrupted the development of growth plate and fetal long bone.

Is Dietary 2-Oxoglutaric Acid Effective in Accelerating Bone Growth and Development in Experimentally-Induced Intrauterine Growth Retarded Gilts?

Simple Summary

Intrauterine growth restriction (IUGR) is a significant health issue that not only affects infant mortality or term body weight, but may also predispose individuals to a reduced rate of weight gain and the development of numerous diseases later in life. In livestock production, growth restricted (IUGR) animals require more time to reach slaughter weight. In this study, we examined the effects of long-term administration of 2-oxoglutaric acid (2-Ox) to experimentally-induced intrauterine growth retarded gilts.

Abstract

In this study, the effect of long-term 2-oxoglutaric acid (2-Ox) supplementation to experimentally-induced intrauterine growth retarded gilts was examined. Sows were treated with synthetic glucocorticoid (dexamethasone) every second day, during the last 45 days of pregnancy, at a dose of 0.03 mg/kg b.w. At birth, the gilts were randomly divided into two groups: unsupplemented and supplemented with 2-Ox for nine months (0.4 g/kg body weight/day). Oral supplementation of 2-Ox to experimentally-induced intrauterine growth retarded gilts increased body weight at weaning as well as final body weight at the age of nine months, and showed a regenerative effect on bone mineralization and morphology of trabeculae and articular cartilage. The positive effects on bone structure were attributed to the 2-Ox-induced alterations in bone metabolism, as evidenced by the changes in the expression of proteins involved in bone formation and remodeling: osteocalcin (OC), osteoprotegerin (OPG), receptor activator of nuclear factor kappa-Β ligand (RANKL), tissue inhibitor of metalloproteinases 2 (TIMP-2), bone morphogenetic protein 2 (BMP-2), cartilage oligomeric matrix protein (COMP), and vascular endothelial growth factor (VEGF).

Dexamethasone: chondroprotective corticosteroid or catabolic killer?

While glucocorticoids have been used for over 50 years to treat rheumatoid and osteoarthritis pain, the prescription of glucocorticoids remains controversial because of potentially harmful side effects at the molecular, cellular and tissue levels. One member of the glucocorticoid family, dexamethasone (DEX) has recently been demonstrated to rescue cartilage matrix loss and chondrocyte viability in animal studies and cartilage explant models of tissue injury and post-traumatic osteoarthritis, suggesting the possibility of DEX as a disease-modifying drug if used appropriately. However, the literature on the effects of DEX on cartilage reveals conflicting results on the drug's safety, depending on the dose and duration of DEX exposure as well as the model system used. Overall, DEX has been shown to protect against arthritis-related changes in cartilage structure and function, including matrix loss, inflammation and cartilage viability. These beneficial effects are not always observed in model systems using initially healthy cartilage or isolated chondrocytes, where many studies have reported significant increases in chondrocyte apoptosis. It is crucially important to understand under what conditions DEX may be beneficial or harmful to cartilage and other joint tissues and to determine potential for safe use of this glucocorticoid in the clinic as a disease-modifying drug.

Dose-related histopathology and bone remodeling characteristics of the knee articular cartilage and subchondral bone induced by glucocorticoids in rats

The aim of the current study was to investigate histopathological changes and bone remodeling in the knee articular cartilage and subchondral bone in rats following treatment with glucocorticoids. A total of 30 3-month-old female Sprague-Dawley rats were randomly divided into either a vehicle control group or one of three experimental groups wherein dexamethasone (Dex) was administered at a dose of 1.0, 2.5 or 5.0 mg/kg (Dex1.0, Dex2.5 and Dex5.0, respectively), for 8 weeks. Articular cartilage and the epiphyseal subchondral bone of the proximal tibias were evaluated by histopathology or for bone remodeling using histomorphometry. No histological changes were identified in the knee articular cartilage but the bone formation rate of the subchondral bone was lower in the Dex1.0 group compared with that of the control group. Compared with the control and the Dex1.0 group, the width of the articular cartilage and the subchondral plate were larger, with abnormal morphology and increased apoptosis of chondrocytes, decreased cell/matrix volume ratio in the cartilage and fewer blood vessels in the subchondral plate in the Dex2.5 and Dex5.0 groups. A higher Dex dose resulted in more severe inhibition of bone formation, a greater number of apoptotic osteocytes and constrained bone resorption. All microstructure parameters indicated no significant changes in the Dex2.5 group but exhibited deterioration in the Dex5.0 group compared with the normal and Dex1.0 group. There were no significant differences in morphological changes, or in static and dynamic bone indices between the Dex2.5 and Dex5.0 groups. In conclusion, long-term glucocorticoid use induced dose-related histopathological changes in the knee articular cartilage, along with unbalanced bone remodeling and osteopenia in the subchondral bone. The degree of damage to the articular cartilage was milder and transformed from compensation to degeneration at higher doses.

Bone Homeostasis in Experimental Fumonisins Intoxication of Rats

Fumonisins are strongly toxic metabolites of Fusarium proliferatum and Fusarium verticillioides commonly present in corn-based feed. The aim of the study was to evaluate bone homeostasis in experimental fumonisins B1 and B2 intoxication of rats, a vertebrate animal model of toxicological studies, as still little is known about the possible disturbing effect of fumonisins on bone homeostasis. Adolescent (5-week-old) male Wistar rats were randomly assigned into a control group and a group FB intoxicated with fumonisins by daily intragastric administration of fumonisins at the dose of 90 mg/kg of body weight per animal in the FB group for 21 days. The fumonisin intoxication did not affect body and bone mass, although the mechanical and geometric properties were decreased in fumonisin-intoxicated rats. Bone volumetric and mineral density did not differ between groups, but bone mineral content and bone ash percentage was lower in the FB group. Detailed analysis showed that Ca, Cu, Fe, Mn, Sr, and Zn bone content significantly decreased in fumonisin intoxicated rats and the alterations in structure of bone mineral phase (reduction of the apatite-bone crystals size) were noted. While the negative structural alterations in growth plate and articular cartilages were also observed, fumonisin intoxication improved histomorphometrical parameters of trabecular bone. Concluding, the dose of fumonisins used in the present study caused hepatotoxic effect, which was sufficient to trigger the disturbance in mineral homeostasis resulting in altered bone metabolism and decreased mechanical endurance.

Maternal HMB treatment affects bone and hyaline cartilage development in their weaned piglets via the leptin/osteoprotegerin system

It has been demonstrated in animal studies that prenatal administration of β-hydroxy-β-methylbutyrate (HMB, metabolite of leucine) influences general growth and mechanical endurance of long bones in newborn offspring in sex-dependent manner. The present experiment was conducted to evaluate the effect of HMB treatment of pregnant sows on bone development in offspring at weaning. From 70th day until the 90th day of gestation, sows received either a basal diet (n = 12) or the same diet supplemented with HMB (n = 12) at the dose of 0.2 g/kg of body weight/day. Femora obtained from six males and females in each group weaned at the age of 35 days were examined. Maternal HMB treatment significantly enhanced body weight and changed bone morphology increasing femur mechanical strength in both sexes. Maternal HMB supplementation also elevated bone micro- and macroelement concentrations and enhanced content of proteoglycans in articular cartilage. Based on the obtained results, it can be concluded that maternal HMB supplementation in the mid-gestation period significantly accelerated bone development in both sexes by upregulation of a multifactorial system including leptin and osteoprotegerin. However, the sex (irrespective of the HMB treatment) was the factor which influenced the collagen structure in cartilages and trabecular bone, as demonstrated both by the Picrosirius red staining and performed analysis of thermal stability of collagenous tissues. The structural differences in collagen between males and females were presumably related to a different collagen maturity. No studies conducted so far provided a detailed morphological analysis of bone, articular cartilage, growth plate and the activities of the somatotropic and pituitary-gonadal axes, as well as leptin/osteoprotegerin system in weaned offspring prenatally treated with HMB. This study showed also the relationship between the maternal HMB treatment and bone osteometric and mechanical traits, hormones, and growth and bone turnover markers such as leptin, osteoprotegerin and insulin-like growth factor-1.

White Tea is More Effective in Preservation of Bone Loss in Adult Rats Co-Exposed to Lead and Cadmium Compared to Black, Red or Green Tea

Lead (Pb) and cadmium (Cd) are toxic metals occurring commonly in the human environment that show mutagenic, genotoxic and carcinogenic effects. Dietary components could prevent heavy metals intoxication by reducing their accumulation in the body. The purpose of the study was to check possible protective effect of regular consumption of white, black, red, or green tea on bone metabolism during long-term exposure to Pb and Cd in adult rats. The 12 week-long exposure to Pb and Cd (50 mg Pb and 7 mg Cd/kg of the diet) in a rat model was studied. Twelve-week-old adult male Wistar rats were randomly divided into a negative control group (Pb and Cd exposure without tea), a control (without Pb and Cd and teas), and groups co-exposed to Pb and Cd and supplemented with green, red, black, or white tea (n=12 each group). The experiment lasted for 12 weeks. The co-exposure to Pb and Cd led to the increase of bone resorption depending on the tea treatment, which was confirmed by the mechanical testing and histomorphometrical examination of cancellous bone. Pb and Cd influenced mechanical strength, reduced the densitometric and geometric parameters and the thickness of growth plate and articular cartilages. Concluding, white tea exerted the best protective effect on bone tissue and hyaline cartilage against heavy metal action.

Prenatal caffeine exprosure increases adult female offspring rat's susceptibility to osteoarthritis via low-functional programming of cartilage IGF-1 with histone acetylation

Our previous in vivo studies showed that prenatal caffeine exposure (PCE) could restrain the development of chondrogenesis, which may delay fetal articular cartilage development and increase susceptibility to osteoarthritis in adults. So, the goal of the current study is to clarify theincreasing susceptibility to adult osteoarthritis in caffeine-exposed female offspring and its'mechanism. Pregnant rats were treated with 120 mg/kg·d caffeine or equal volumes of saline from gestational day (GD) 9 to 20. knee joints were collected from GD20 female fetuses and 18-week old female offspring which was treated with strenuous running for 6 weeks (55 min/day at 20 m/min) load to induce osteoarthritis. Knee joints from GD20 fetuses and adult offspring were collected for histochemistry and immunohistochemistry. Next, chondrocytes were isolated from 1-day-old newborn rats and in vitro studies were conducted where the cells in primary culture were exposed to 1, 10, and 100 μM caffeine and 250, 500, and 1,250 nM corticosterone. Insulin-like growth factor 1 (IGF-1) signal pathway genes' expression levels in fetal chondrocytes were studied, and IGF-1 histone acetylation was detected in vitro. Immunohistochemical results showed low expression levels of IGF-1 signaling genes (IGF-1, IRS-1, AKT, and COL2A1) both in fetal and adult cartilage with PCE. For adult offspring, histological results and Mankin score revealed increased cartilage destruction and accelerated osteoarthritis progression in PCE group with strenuous running exercise. Analysis in vitro revealed that caffeine and corticosterone impeded the expression of IGF-1 signaling pathway aggrecan and COL2A1 genes, but only corticosterone decreased H3K9 and H3K27 acetylation in the IGF-1 promoter region. In concluson, PCE low functional programmed cartilage IGF-1 by histone acetylation modification via overexposure to corticosterone and delayed articular cartilage development from fetus to adults. Then, the delayed cartilage development increased susceptibility to osteoarthritis in offsprings.

The effect of tannic acid on bone mechanical and geometric properties, bone density, and trabecular histomorphometry as well as the morphology of articular and growth cartilages in rats co-exposed to cadmium and lead is dose dependent

Cadmium (Cd) and lead (Pb) are toxic elements that accumulate to the largest extent in bones. Rats were used to investigate whether tannic acid (TA; 0.5%, 1.0%, 1.5%. 2.0%, or 2.5%) would have a protective effect on the structure and properties of bones in the case of exposure to Cd and Pb (diet: 7 mg Cd/kg and 50 mg Pb/kg) for 6 weeks. The effects of administration of TA in Cd- and Pb-poisoned rats on bone characteristics and the morphology of articular and growth cartilages were determined. All the rats administered Cd and Pb had an enhanced Cd and Pb concentration in blood plasma and bone and reduced bone Ca content irrespective of the TA administration. Cd and Pb alone reduced the mechanical endurance and histomorphometric parameters of trabecular bone and the thickness of the growth plate and articular cartilage. Tannic acid improved cancellous bone parameters in the rat exposed to Cd and Pb. A diet rich in TA improved articular cartilage constituents in heavy metal-poisoned rats. These results suggest that alimentary TA supplementation can counteract in a dose-dependent manner some of the destructive changes evoked by Cd and Pb possibly by reducing the exposure.

The Influence of the Dietary Cu-Glycine Complex on the Histomorphology of Cancellous Bone, Articular Cartilage, and Growth Plate as well as Bone Mechanical and Geometric Parameters Is Dose Dependent

Copper (Cu) is required for all basic biochemical and physiological processes. The objective of this study was to compare the effect of two different chemical forms (sulfates and glycinate chelates also below the recommended dose) of Cu administered to adult rats on the biomechanical and morphometric properties of femur. Male rats at the age of 12 weeks were used in the 12-week experiment. The control diet provided the required Cu level from sulfate (S-Cu), and the other diets were supplemented with Cu-glycine complex. The Cu-Gly-treatment, irrespective of its concentration, did not influence the bone mass and length. The Cu-Gly-treatment in 100 and 75% of daily demand increased mechanical endurance. The Cu-Gly-treatment (regardless of its concentration) increased the real bone volume in epiphysis and decreased the total thickness and zone I of the articular cartilage compared to the control group supplemented with S-Cu. The Cu-Gly-treatment enhanced the content of proteoglycans (except the OG50 group). Dietary Cu given to adult rats in the Cu-Gly complex covering the daily demand in 75% exerted a positive effect on bone metabolism and appeared to be the most effective among the investigated doses of the organic form.

A metabolite of leucine (β-hydroxy-β-methylbutyrate) given to sows during pregnancy alters bone development of their newborn offspring by hormonal modulation

The effects of dietary β-hydroxy-β-methylbutyrate (HMB) supplementation during gestation on bone, growth plate, and articular cartilage in newborns were determined. Thermal analysis of articular cartilage was performed to examine the structural changes in collagen. At day 70 of gestation, a total of 12 sows (Large White Polish breed, at the second parity) were randomly assigned to two groups, with each group receiving either a basal diet or the same diet supplemented with 0.2 g/day HMB until the 90^th day. Maternal HMB supplementation enhanced body weight, bone length, and diameter in males. It also improved geometric and mechanical properties contributing to increased bone morphology and endurance. In turn, alteration of the length was only observed in females. The positive effects were mediated by increased serum concentrations of insulin-like growth factor-1 and leptin. HMB-treatment enhanced the concentration of FSH, LH, estradiol, and testosterone. Serum TAP was enhanced by the HMB-treatment by 34% in females and 138% in males. Beneficial effects of the HMB-treatment on trabecular bone and content of proteoglycans in articular cartilage were shown. The HMB-treatment significantly changed the collagen structure in cartilages, especially in the females, which was demonstrated by the PSR analysis. Differences between the HMB-supplemented and the control females in the calorimetric peak temperatures were presumably related to different collagen fibril density in the articular cartilage structure. In summary, maternal HMB supplementation in the mid-gestation period significantly improved general growth and mechanical endurance of long bones by the influence on the somatotropic and pituitary-gonadal axes in the offspring.

Dietary 2-oxoglutarate prevents bone loss caused by neonatal treatment with maximal dexamethasone dose

Synthetic glucocorticoids (GCs) are widely used in the variety of dosages for treatment of premature infants with chronic lung disease, respiratory distress syndrome, allergies, asthma, and other inflammatory and autoimmune conditions. Yet, adverse effects such as glucocorticoid-induced osteoporosis and growth retardation are recognized. Conversely, 2-oxoglutarate (2-Ox), a precursor of glutamine, glutamate, and collagen amino acids, exerts protective effects on bone development. Our aim was to elucidate the effect of dietary administered 2-Ox on bone loss caused by neonatal treatment with clinically relevant maximal therapeutic dexamethasone (Dex) dose. Long bones of neonatal female piglets receiving Dex, Dex+2-Ox, or untreated were examined through measurements of mechanical properties, density, mineralization, geometry, histomorphometry, and histology. Selected hormones, bone turnover, and growth markers were also analyzed. Neonatal administration of clinically relevant maximal dose of Dex alone led to over 30% decrease in bone mass and the ultimate strength ( P < 0.001 for all). The length (13 and 7% for femur and humerus, respectively) and other geometrical parameters (13-45%) decreased compared to the control ( P < 0.001 for all). Dex impaired bone growth and caused hormonal imbalance. Dietary 2-Ox prevented Dex influence and vast majority of assessed bone parameters were restored almost to the control level. Piglets receiving 2-Ox had heavier, denser, and stronger bones; higher levels of growth hormone and osteocalcin concentration; and preserved microarchitecture of trabecular bone compared to the Dex group. 2-Ox administered postnatally had a potential to maintain bone structure of animals simultaneously treated with maximal therapeutic doses of Dex, which, in our opinion, may open up a new opportunity in developing combined treatment for children treated with GCs. Impact statement The present study has showed, for the first time, that dietary 2-oxoglutarate (2-Ox) administered postnatally has a potential to improve/maintain bone structure of animals simultaneously treated with maximal therapeutic doses of dexamethasone (Dex). It may open the new direction in searching and developing combined treatment for children treated with glucocorticoids (GCs) since growing group of children is exposed to synthetic GCs and adverse effects such as glucocorticoid-induced osteoporosis and growth retardation are recognized. Currently proposed combined therapies have numerous side effects. Thus, this study proposed a new direction in combined therapies utilizing dietary supplementation with glutamine derivative. Impairment caused by Dex in presented long bones animal model was prevented by dietary supplementation with 2-Ox and vast majority of assessed bone parameters were restored almost to the control level. These results support previous thesis on the regulatory mechanism of nutrient utilization regulated by glutamine derivatives and enrich the nutritional science.

Alteration in bone geometric and mechanical properties, histomorphometrical parameters of trabecular bone, articular cartilage, and growth plate in adolescent rats after chronic co-exposure to cadmium and lead in the case of supplementation with green, black, red and white tea

Adolescent male Wistar rats were used to check whether regular consumption of black, red, white, or green tea would have a protective effect on femur development during 12-week exposure to Cd and Pb (7mg Cd and 50mg Pb in 1kg of the diet). The animals were randomly divided (n=12) into a positive control (without Cd, Pb and teas), a negative control group (Cd and Pb), and groups supplemented additionally with green (GT), black (BT), red (RT), and white tea (WT). Heavy metals reduced the geometric and densitometric parameters and the total thickness of articular cartilage irrespective of tea administration and influenced mechanical endurance, growth plate thickness, and trabecular histomorphometry depending on the tea type. It is difficult to indicate which tea has the best protective effects on bone and hyaline cartilage against heavy metal action.

Molecular Actions of Glucocorticoids in Cartilage and Bone During Health, Disease, and Steroid Therapy

Cartilage and bone are severely affected by glucocorticoids (GCs), steroid hormones that are frequently used to treat inflammatory diseases. Major complications associated with long-term steroid therapy include impairment of cartilaginous bone growth and GC-induced osteoporosis. Particularly in arthritis, GC application can increase joint and bone damage. Contrarily, endogenous GC release supports cartilage and bone integrity. In the last decade, substantial progress in the understanding of the molecular mechanisms of GC action has been gained through genome-wide binding studies of the GC receptor. These genomic approaches have revolutionized our understanding of gene regulation by ligand-induced transcription factors in general. Furthermore, specific inactivation of GC signaling and the GC receptor in bone and cartilage cells of rodent models has enabled the cell-specific effects of GCs in normal tissue homeostasis, inflammatory bone diseases, and GC-induced osteoporosis to be dissected. In this review, we summarize the current view of GC action in cartilage and bone. We further discuss future research directions in the context of new concepts for optimized steroid therapies with less detrimental effects on bone.

Mitogen-inducible gene-6 partly mediates the inhibitory effects of prenatal dexamethasone exposure on endochondral ossification in long bones of fetal rats

BACKGROUND AND PURPOSE

Prenatal exposure to dexamethasone slows down fetal linear growth and bone mineralization but the regulatory mechanism remains unknown. Here we assessed how dexamethasone regulates bone development in the fetus.

EXPERIMENTAL APPROACH

Dexamethasone (1 mg·kg(-1) ·day(-1) ) was injected subcutaneously every morning in pregnant rats from gestational day (GD)9 to GD20. Fetal femurs and tibias were harvested at GD20 for histological and gene expression analysis. Femurs of 12-week-old female offspring were harvested for microCT (μCT) measurement. Primary chondrocytes were treated with dexamethasone (10, 50, 250 and 1000 nM).

KEY RESULTS

Prenatal dexamethasone exposure resulted in accumulation of hypertrophic chondrocytes and delayed formation of the primary ossification centre in fetal long bone. The retardation was accompanied by reduced maturation of hypertrophic chondrocytes, decreased osteoclast number and down-regulated expression of osteocalcin and bone sialoprotein in long bone. In addition, the mitogen-inducible gene-6 (Mig6) and osteoprotegerin (OPG) expression were stimulated, and the receptor activator of NF-κB ligand (RANKL) expression was repressed. Moreover, dexamethasone activated OPG and repressed RANKL expression in both primary chondrocytes and primary osteoblasts, and the knockdown of Mig6 abolished the effect of dexamethasone on OPG expression. Further, μCT measurement showed loss of bone mass in femur of 12-week-old offspring with prenatal dexamethasone exposure.

CONCLUSIONS AND IMPLICATIONS

Prenatal dexamethasone exposure delays endochondral ossification by suppressing chondrocyte maturation and osteoclast differentiation, which may be partly mediated by Mig6 activation in bone. Bone development retardation in the fetus may be associated with reduced bone mass in later life.

Prenatally administered dexamethasone impairs folliculogenesis in spiny mouse offspring

This study was designed to determine whether prenatal dexamethasone treatment has an effect on follicular development and atresia in the ovary of spiny mouse (Acomys cahirinus) offspring. Dexamethasone (125µg kg-1 bodyweight per day) was administered to pregnant spiny mice from Day 20 of gestation to parturition. The processes of follicle loss were analysed using classical markers of apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling reaction, active caspase-3) and autophagy (Lamp1). The present study indicated that dexamethasone reduced the pool of healthy primordial follicles. Moreover, the oocytes from these follicles showed intensive caspase-3 and Lamp1 staining. Surprisingly, dexamethasone caused an increase in the number of secondary follicles; however, most of these follicles were characterised by extensive degeneration of the oocyte and caspase-3 and Lamp1 labelling. Western-blot analysis indicated that the glucocorticoid receptor as well as apoptosis and autophagy markers were more strongly expressed in the DEX-treated group than in the control. On the basis of these findings, we have concluded that dexamethasone impairs spiny mouse folliculogenesis and enhances follicular atresia through induction of autophagy or combined autophagy and apoptosis.

The effect of supplementation of a glutamine precursor on the growth plate, articular cartilage and cancellous bone in fundectomy-induced osteopenic bone

The aim of the study was to investigate the effect of 2-oxoglutaric acid (2-Ox) supplementation (a precursor of glutamine and hydroxyproline, the most abundant amino acid of collagen) on cartilage and bone in pigs after fundectomy. Pigs at the age of forty days were subjected to fundectomy and divided into two groups depending on 2-Ox supplementation (at the daily dosage of 0.4 g/kg of body weight). Other pigs were sham operated. Pigs were euthanized at the age of eight months. An analysis of the morphometry of trabeculae, growth plate and articular cartilage in fundectomy-induced osteopenic bone was performed. Moreover, the levels of expression of osteocalcin, osteopontin and osteoprotegerin in trabecular bone and osteocalcin in articular cartilage were evaluated. Articular cartilage was thinnest in fundectomized pigs and thickest in 2-Ox-supplemented animals after fundectomy. Moreover, 2-Ox supplementation after fundectomy enhanced the total thickness of the growth plate and trabeculae in fundectomized pigs. The most evident signal for osteocalcin and osteoprotegerin in trabecular bone was in sham-operated and 2-Ox-supplemented pigs; a low reaction was observed in the fundectomized group. Additionally, as a long-term postoperative consequence, a change was observed in the expression of osteocalcin in articular cartilage. It seems that 2-Ox is suitable for use in preventing the negative effects of fundectomy on cancellous bone and cartilage.

The influence of dexamethasone administered prenatally on cartilage of newborn spiny mouse (Acomys cahirinus) offspring

Considering the negative effects of glucocorticoid treatment, especially during fetal development it is important to investigate effectors decreasing such disadvantages. The aim of this study was to investigate the effect of prenatally administered dexamethasone (Dex), a synthetic glucocorticoid, on the histomorphometry of the femur in the offspring of spiny mice. The study was performed on 24 pregnant spiny mice. The time of the experiment included the prenatal period between the 20th day of gestation until birth (pregnancy lasts on average of 36–38 days). The mice from the experimental group received dexamethasone per os in a dose of 125 mg/kg birth weight daily. At the end, the newborns from the experimental and control group were weighted and euthanized. Maternal Dex treatment resulted in a 17% decrease in birth weight in newborns. Dex administration significantly reduced the thickness of the hypertrophy zone of the growth plate by 34% and total thickness by 8,7%. In addition, Dex decreased the number of cells in the articular cartilage by 27% and significantly decreased their diameter by 5%. Dex also affected the structure and spatial distribution of thick and thin collagen fibers, lowering the proportion of thin fibers compared with the control group. Moreover, Dex treatment considerably lowered the amount of proteoglycans in articular and growth cartilages. Exposure to glucocorticoids in pregnant spiny mice affects cartilage development by accelerating maturity of collagen fibers and growth plate, presumably along with further disruption of longitudinal growth of long bones.

Effects of 2-oxoglutaric acid on bone morphometry, densitometry, mechanics, and immunohistochemistry in 9-month-old boars with prenatal dexamethasone-induced osteopenia

The structural quality of the connective tissue is genetically determined and is influenced by hormonal and nutritional modification. An effect of a 2-Ox-rich diet on bone mineralization and structure and expression of non-collagenous protein in articular and growth cartilages of maternal dexamethasone-treated 9-month-old boars was considered in this study. Sows were treated i.m. with dexamethasone at the dose of 0.03 mg kg(-1) body weight every second day during the last 45 days of pregnancy. After the birth, the boars were divided into two groups: administered and not supplemented with 2-Ox for 9 months (0.4 g/kg body weight/day). Dexamethasone given during the prenatal time inhibited the growth and negatively influenced the mechanics, geometry and histomorphometrical parameters of long bones and cartilage irrespective of the diet. Moreover, maternal dexamethasone treatment resulted in expression of osteocalcin in the articular cartilage, and the diet rich in 2-Ox limited the OC expression. This study demonstrated that changes observed in adult boars initiated by dexamethasone treatment in the prenatal period were persistent and long-term use of alimentary 2-Ox supplementation can counteract only some of the destructive changes evoked by prenatal dexamethasone excess.

Intrauterine low-functional programming of IGF1 by prenatal nicotine exposure mediates the susceptibility to osteoarthritis in female adult rat offspring

This study aimed to evaluate whether female adult offspring born with intrauterine growth retardation induced by prenatal nicotine exposure (PNE) are susceptible to osteoarthritis (OA) and to explore the underlying programming mechanisms. Pregnant rats were treated with nicotine or saline at 2.0 mg/kg/d from gestational d 11 to 20. The female adult offspring with or without PNE were forced with a strenuous treadmill running for 6 wk to induce OA. Nicotine's effects on fetal articular chondrocytes were studied by exposing chondrocytes to nicotine for 10 d, and dihydro-β-erythroidine, a selective α4β2-nicotinic acetylcholine receptor (nAChR) inhibitor, was used to identify the change of nicotine's effect. For adult offspring, increased cartilage destruction and accelerated OA progression were observed in the PNE group with running; the expression of α1 chain of type II collagen (Col2A1), aggrecan, SRY-type high mobility group box 9 (Sox9), and IGF1 signaling molecules in the cartilage of PNE offspring were decreased. For fetuses, elevated serum corticosteroid and nicotine levels and suppressed IGF1 levels were observed; expression of Col2A1, aggrecan, Sox9, and IGF1 were reduced. The result of chondrocytes revealed that nicotine impeded the expression of Col2A1, aggrecan, and IGF1; blocking α4β2-nAChR rescued nicotine's suppression. In conclusion, PNE increases the susceptibility of adult offspring to OA; the potential mechanism involves IGF1 low-functional programming in articular cartilage caused directly by the action of nicotine on α4β2-nAChR.

Prenatal ethanol exposure increases osteoarthritis susceptibility in female rat offspring by programming a low-functioning IGF-1 signaling pathway

Epidemiological evidence indicates that osteoarthritis (OA) and prenatal ethanol exposure (PEE) are both associated with low birth weight but possible causal interrelationships have not been investigated. To investigate the effects of PEE on the susceptibility to OA in adult rats that experienced intrauterine growth retardation (IUGR), and to explore potential intrauterine mechanisms, we established the rat model of IUGR by PEE and dexamethasone, and the female fetus and 24-week-old adult offspring subjected to strenuous running for 6 weeks were sacrificed. Knee joints were collected from fetuses and adult offspring for histochemistry, immunohistochemistry and qPCR assays. Histological analyses and the Mankin score revealed increased cartilage destruction and accelerated OA progression in adult offspring from the PEE group compared to the control group. Immunohistochemistry showed reduced expression of insulin-like growth factor-1 (IGF-1) signaling pathway components. Furthermore, fetuses in the PEE group experienced IUGR but exhibited a higher postnatal growth rate. The expression of many IGF-1 signaling components was downregulated, which coincided with reduced amounts of type II collagen in the epiphyseal cartilage of fetuses in the PEE group. These results suggest that PEE enhances the susceptibility to OA in female adult rat offspring by down-regulating IGF-1 signaling and retarding articular cartilage development.

Dietary 2-oxoglutarate mitigates gastrectomy-evoked structural changes in cartilage of female rats

Gastrectomy (Gx) leads to osteopenia/osteoporosis in humans and animals. However, little is known about the influence of Gx on the cartilage in this regard. Recent studies have demonstrated a protective effect of 2-oxoglutaric acid (2-Ox) on bone and cartilage. Hence, the purpose of this study was to investigate whether 2-Ox can mitigate eventual Gx-induced cartilage impairment. Twenty female Sprague-Dawley rats were subjected to Gx and randomly divided into two groups: Gx + 2-Ox and Gx. Another 20 rats were sham-operated (ShO) and randomly divided into two groups: ShO + 2-Ox and ShO. The daily dose of 2-Ox administered to the rats in the drinking water was 0.43 g per 100 g rat. After eight weeks, rats were euthanized and femora and tibiae were collected. Histology and histomorphometry analyses of the articular cartilage and the growth plate were done. Gx resulted in a 32% (±44.5 femur, ±35.8 tibia) decrease in overall thickness of articular cartilage in both bones (femur: ShO 279.1 ± 48.5 vs. Gx 190.2 ± 38.4 µm, tibia: ShO 222.9 ± 50.3 µm vs. Gx 151.3 ± 52.6 µm) (in some zones up to 58 ± 28.0%), and in the growth plate up to 20% (±22.4) (femur: ShO 243.0 ± 34.0 vs. Gx 207.0 ± 33.7 µm, tibia: ShO 220.0 ± 24.6 µm vs. Gx 171.1 ± 16.1 µm). Gx altered the spatial distribution of thick and thin collagen fibers, and chondrocyte shape and size. 2-Ox administration prevented the reduction in both cartilages thickness (Gx + 2-Ox: articular cartilage 265.2 ± 53.8 µm, 235.6 ± 42.7 µm, growth plate 236.7 ± 39.2 µm, 191.3 ± 16.5 µm in femur and tibia, respectively), and abolished the spatial changes in collagen distribution and structure induced by Gx. Gx affects cartilage structure and thickness, however, 2-Ox administration mitigates these effects and showed protective and stimulatory properties. Our observations suggest that dietary 2-Ox can be used to offset some of the changes in hyaline cartilage, in particular articular cartilage, following bariatric surgeries.