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

Circular RNA Gtdc1 Protects Against Offspring Osteoarthritis Induced by Prenatal Prednisone Exposure by Regulating SRSF1-Fn1 Signaling

Chondrodysplasia is closely associated with low birth weight and increased susceptibility to osteoarthritis in adulthood. Prenatal prednisone exposure (PPE) can cause low birth weight; however, its effect on offspring cartilage development remains unexplored. Herein, rats are administered clinical doses of prednisone intragastrically on gestational days (GDs) 0-20 and underwent long-distance running during postnatal weeks (PWs) 24-28. Knee cartilage is assayed for quality and related index changes on GD20, PW12, and PW28. In vitro experiments are performed to elucidate the mechanism. PPE decreased cartilage proliferation and matrix synthesis, causing offspring chondrodysplasia. Following long-distance running, the PPE group exhibited more typical osteoarthritis-like changes. Molecular analysis revealed that PPE caused cartilage circRNomics imbalance in which circGtdc1 decreased most significantly and persisted postnatally. Mechanistically, prednisolone reduced circGtdc1 expression and binding with Srsf1 to promote degradation of Srsf1 via K48-linked polyubiquitination. This further inhibited the formation of EDA/B+Fn1 and activation of PI3K/AKT and TGFβ pathways, reducing chondrocyte proliferation and matrix synthesis. Finally, intra-articular injection of offspring with AAV-circGtdc1 ameliorated PPE-induced chondrodysplasia, but this effect is reversed by Srsf1 knockout. Altogether, this study confirms that PPE causes chondrodysplasia and susceptibility to osteoarthritis by altering the circGtdc1-Srsf1-Fn1 axis; in vivo, overexpression of circGtdc1 can represent an effective intervention target for ameliorating PPE-induced chondrodysplasia.

Prenatal amoxicillin exposure induces developmental toxicity in fetal mice and its characteristics

Amoxicillin, a widely used antibiotic in human and veterinary pharmaceuticals, is now considered as an "emerging contaminant" because it exists widespreadly in the environment and brings a series of adverse outcomes. Currently, systematic studies about the developmental toxicity of amoxicillin are still lacking. We explored the potential effects of amoxicillin exposure on pregnancy outcomes, maternal/fetal serum phenotypes, and fetal multiple organ development in mice, at different doses (75, 150, 300 mg/(kg·day)) during late-pregnancy, or at a dose of 300 mg/(kg·day) during different stages (mid-/late-pregnancy) and courses (single-/multi-course). Results showed that prenatal amoxicillin exposure (PAmE) had no significant influence on the body weights of dams, but it could inhibit the physical development and reduce the survival rate of fetuses, especially during the mid-pregnancy. Meanwhile, PAmE altered multiple maternal/fetal serum phenotypes, especially in fetuses. Fetal multi-organ function results showed that PAmE inhibited testicular/adrenal steroid synthesis, long bone/cartilage and hippocampal development, and enhanced ovarian steroid synthesis and hepatic glycogenesis/lipogenesis, and the order of severity might be gonad (testis, ovary) > liver > others. Further analysis found that PAmE-induced multi-organ developmental and functional alterations had differences in stages, courses and fetal gender, and the most obvious changes might be in high-dose, late-pregnancy and multi-course, but there was no typical rule of a dose-response relationship. In conclusion, this study confirmed that PAmE could cause abnormal development and multi-organ function alterations, which deepens our understanding of the risk of PAmE and provides an experimental basis for further exploration of the long-term harm.

The changes in adrenal developmental programming and homeostasis in offspring induced by glucocorticoids exposure during pregnancy

Clinically, synthetic glucocorticoids are often used to treat maternal and fetal related diseases, such as preterm birth and autoimmune diseases. Although its clinical efficacy is positive, it will expose the fetus to exogenous glucocorticoids. Adverse environments during pregnancy (e.g., exogenous glucocorticoids exposure, malnutrition, infection, hypoxia, and stress) can lead to fetal overexposure to endogenous maternal glucocorticoids. Basal glucocorticoids levels in utero are crucial in determining fetal tissue maturation and its postnatal fate. As the synthesis and secretion organ of glucocorticoids, the adrenal development is crucial for the growth and development of the body. Studies have found that glucocorticoids exposure during pregnancy could cause abnormal fetal adrenal development, which could last after birth or even adulthood. As the key organ of fetal-originated adult disease, the adrenal developmental programming has a profound impact on the health of offspring, which can lead to many chronic diseases in adulthood. However, the aberrant adrenal development in offspring caused by glucocorticoids exposure during pregnancy and its intrauterine programming mechanism have not been systematically clarified. Therefore, this review summarizes recent research progress on the short and long-term hazards of aberrant adrenal development induced by glucocorticoids exposure during pregnancy, which is of great significance for the analysis of aberrant adrenal development and clarify the intrauterine origin mechanism of fetal-originated adult disease.

Stage-, dose-, and course-dependent inhibition of prenatal amoxicillin exposure on fetal articular cartilage development in fetal mice

Amoxicillin is widely used in the treatment of infectious diseases during pregnancy; however, the effects of prenatal amoxicillin exposure (PAE) on fetal development remain largely unknown. Therefore, this study aimed to investigate the toxic effects of PAE on fetal cartilage at different stage-, dose-, and course. Pregnant Kunming mice were orally administered 300 mg/kg·d (converted from clinical dose) amoxicillin on gestational days (GD) 10-12 or 16-18 (mid or late pregnancy stage), 150 or 300 mg/kg.d amoxicillin on GD16-18 (different doses), 300 mg/kg·d amoxicillin on GD16 (single course) or 16-18 (multiple courses), respectively. The fetal articular cartilage of the knee was collected on GD18. The number of chondrocytes and the expression of matrix synthesis/degradation, proliferation/apoptosis-related markers, and the TGF-β signaling pathway were detected. The results showed that the number of chondrocytes and the expression of matrix synthesis markers were reduced in male fetal mice treated with PAE (GD16-18, 300 mg/kg.d, single course and multiple courses), whereas the above indices in female mice showed no changes. The inhibited expression of PCNA, increased expression of Caspase-3, and down-regulated expression of the TGF-β signaling pathway were found in male PAE fetal mice. Accordingly, PAE exerted its "toxic effect window" on the knee cartilage development in male fetal mice, which manifested as reduced chondrocyte number and inhibited expression of matrix synthesis at a clinical dose of multiple courses in the late pregnancy stage. This study provides a theoretical and experimental basis for elucidating the risk of chondrodevelopmental toxicity associated with amoxicillin during pregnancy.

Prenatal smoke (Nicotine) exposure and offspring's metabolic disease susceptibility in adulthood

Exposure to smoking (nicotine) during pregnancy not only directly affects fetal development, but also increases susceptibility to metabolic diseases in adulthood, but the mechanism of action remains unclear. Here, we review epidemiological and laboratory studies linking these relationships. In addition to the direct effect of nicotine on the fetus, intrauterine neuroendocrine-metabolic programming mediated by maternal glucocorticoid overexposure also plays an important role, involving glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis, hypothalamic-pituitary-adrenal (HPA) axis, renin-angiotensin system (RAS) and other endocrine systems. Epigenetics is involved in intrauterine neuroendocrine-metabolic programming, metabolic disease susceptibility and multigenerational inheritance. There are "two programming" and "two strikes" mechanisms for the occurrence of fetal-originated metabolic diseases in adulthood. These innovative research summaries and academic viewpoints provide experimental and theoretical basis for systematically elucidating the occurrence and development of fetal-originated metabolic diseases.

Transforming growth factor-β receptor 1: An intervention target for genetic poor cartilage quality induced by prenatal dexamethasone exposure

INTRODUCTION

Fetal-originated osteoarthritis is relative to poor cartilage quality and may exhibit transgenerational genetic effects. Previous findings revealed prenatal dexamethasone exposure (PDE) induced poor cartilage quality in offspring.

OBJECTIVES

This study focused on further exploring molecular mechanism, heritability, and early intervention of fetal-originated osteoarthritis.

METHODS

Pregnant rats (F0) were segregated into control and PDE groups depending upon whether dexamethasone was administered on gestational days (GDs) 9-20. Some female offspring were bred with healthy males during postnatal week (PW) 8 to attain the F2 and F3 generations. The F3-generation rats were administrated with glucosamine intragastrically at PW12 for 6 weeks. The knee cartilages of male and female rats at different time points were harvested to assay their morphologies and functions. Furthermore, primary chondrocytes from the F3-generation rats were isolated to confirm the mechanism and intervention target of glucosamine.

RESULTS

Compared with the control, female and male rats in each generation of PDE group showed thinner cartilage thicknesses; shallower and uneven staining; fewer chondrocytes; higher Osteoarthritis Research Society International scores; and lower mRNA and protein expression of SP1, TGFβR1, Smad2, SOX9, ACAN and COL2A1. After F3-generation rats were treated with glucosamine, all of the above changes could be reversed. In primary chondrocytes isolated from the F3-generation rats of PDE group, glucosamine promoted SP1 expression and binding to TGFβR1 promoter to increase the expression of TGFβR1, p-Smad2, SOX9, ACAN and COL2A1, but these were prevented by SB431542 (a potent and selective inhibitor of TGFβR1).

CONCLUSIONS

PDE induced chondrodysplasia in offspring and stably inherited in F3-generation rats, which was related to decreased expression of SP1/TGFβR1/Smad2/SOX9 pathway to reduce the cartilage matrix synthesis, without major sex-based variations. Glucosamine could alleviate the poor genetic cartilage quality in offspring induced by PDE by up-regulating SP1/TGFβR1 signaling, which was prevented by a TGFβR1 inhibitor. This study elucidated the molecular mechanism and therapeutic target (TGFβR1) of genetic chondrodysplasia caused by PDE, which provides a research basis for precisely treating fetal-originated osteoarthritis.

Sex differences and heritability of adrenal steroidogenesis in offspring rats induced by prenatal nicotine exposure

The epidemiological investigation has suggested prenatal nicotine exposure (PNE) induces multiorgan developmental toxicity and increases the risk of metabolic diseases in offspring. Our previous study found that the occurrence of fetal-originated diseases was associated with abnormal adrenal development in offspring. However, the long-term harmful effects on adrenal development in offspring induced by PNE remain unclear. Pregnant Wistar rats were injected subcutaneously with nicotine (2 mg/kg·d) from gestation day (GD) 9 to GD20 to obtain the adrenal gland from fetal and adult offspring rats of F1 and F2 generations. We found that the adrenal insulin-like growth factor 1 (IGF1) signaling pathway and steroidogenic function were increased in male while decreased in female of PNE fetal rats, which could extend into adulthood. Furthermore, the primary adrenal cells of fetal rats were treated with nicotine to observe the phenomena and clarify the possible mechanism of the sex difference. The results suggested that there are sex differences in IGF1 signaling pathway and steroidogenic function induced by PNE, which may be associated with sex differences in nAChRβ1 expression. In addition, the adrenal steroidogenic function was reduced in F2 offspring of F1 PNE female rats (regardless of mating with control or Male PNE rats). Therefore, the decrease of adrenal steroidogenic function in female offspring rats induced by PNE has maternal heritability. In conclusion, PNE could lead to sex differences and heritability of adrenal steroidogenic function in offspring rats.

Asthma susceptibility in prenatal nicotine-exposed mice attributed to β-catenin increase during CD4+ T cell development

Cigarette smoke is a common global environmental pollutant. Asthma, the most frequent allergic airway disease, is related to maternal exposure to cigarette smoke. Our previous studies demonstrated that prenatal exposure to nicotine (PNE), the major active product of smoking, impairs fetal thymopoiesis and CD4⁺ T cell development after birth. This study aimed to investigate whether PNE contributes to asthma susceptibility through CD4⁺ T cell development alterations. First, A PNE model was established by administering 3 mg/kg/day nicotine to maternal mice, and then an ovalbumin-induced asthma model was established in the offspring. Further, β-catenin and downstream pathways were inhibited in vitro to confirm the molecular mechanisms underlying the phenotype observed during the in vivo phase. The results showed that PNE induced Th2 and Th17 biases at developmental checkpoints and aggravated asthma symptoms in the offspring. In fetuses, PNE up-regulated α7 nAChR, activated PI3K-AKT, promoted β-catenin level increase, and established potential Th2- and Th17-biased gene expression patterns during thymopoiesis, which persisted after birth. Similar results were also observed in 1 μM nicotine-treated thymocytes in vitro. Moreover, inhibiting PI3K-AKT by LY294002 abrogated nicotine-mediated β-catenin level increase and thymopoiesis abnormalities, and an α7 nAChR antagonist (α-btx) also reversed nicotine-induced PI3K-AKT activation. Our findings provide strong evidence that PNE is a risk factor for T cell deviation and postnatal asthma, and revealed that nicotine-induced β-catenin level increase induces thymopoiesis abnormalities.

Intrauterine endogenous high glucocorticoids program ovarian dysfunction in female offspring secondary to prenatal caffeine exposure

Ovarian dysfunction has an intrauterine origin, and prenatal caffeine exposure (PCE) could lead to abnormal follicle counts in offspring after birth. However, the effect of PCE on offspring ovarian function and its mechanism of intrauterine programming have not been reported thus far. In this study, pregnant Wistar rats were intragastrically administered caffeine (30 and 120 mg/kg·d) at gestational days 9-20 (GD9-20). Certain tests were performed on the blood, ovaries and hypothalamus of female offspring at different time points. PCE female offspring had ovarian dysfunction in adulthood compared with the control. Further results showed that in utero ovarian morphological development and estradiol synthesis were inhibited but rapidly increased during puberty in the PCE group. The histone 3 lysine 27 acetylation (H3K27ac) level of the insulin-like growth factor 1 (IGF1) promoter region and its expression were decreased in the ovary, which was due to exposure to high levels of fetal blood corticosterone, and the H3K27ac level of IGF1 and its expression shifted to increase after birth with a decrease in serum corticosterone levels. Chronic stress led to increased serum corticosterone levels in adult offspring, whereas ovarian morphological development, the H3K27ac level of IGF1 and its expression, and estradiol synthesis were significantly inhibited. Moreover, the activity of the hypothalamic-pituitary-ovarian (HPO) axis was increased in the early postnatal period of PCE offspring, and chronic stress reversed these changes. In the KGN cell line, it was found that cortisol could promote the translocation of the glucocorticoid receptor (GR) into the nucleus and upregulate histone deacetylase 10 (HDAC10) to inhibit the H3K27ac level of IGF1 and its expression and estradiol synthesis. In summary, PCE is associated with ovarian dysfunction in female adult offspring, and the potential mechanism is related to intrauterine high glucocorticoid exposure by activating the GR and recruiting HDAC10 to affect ovarian glucocorticoid-IGF1 axis programming and to inhibit estradiol synthesis.

Maternal nicotine exposure aggravates metabolic associated fatty liver disease via PI3K/Akt signaling in adult offspring mice

AIM

The aim of this study is to investigate the effect of maternal nicotine exposure (MNE) on the development of metabolic associated fatty liver disease (MAFLD) in adulthood offspring and the underlying mechanism.

METHODS

Pregnant mice (n = 22) were subcutaneously injected with either saline vehicle (n = 11) or nicotine (n = 11) twice a day on gestational days 11-21. Offspring mice (n = 176) from both groups were weaned at postnatal day 21, and for 6 months after postnatal day 21, 96 mice were fed either a standard chow diet (n = 48) or a high-fat diet (n = 48). Serum lipid indicators, liver function indicators, insulin, and liver mitochondrial respiration were analyzed. The expression levels of fibrosis-related proteins, phosphorylated PI3K, phosphorylated Akt, sterol regulatory element-binding transcription factor 1 (SREBP1c), and peroxisome proliferator-activated receptor alpha (PPAR-α) were detected in the liver by immunohistochemistry and Western blotting.

RESULTS

MNE significantly decreased the weight of both maternal and offspring mice (~30%) and inhibited organ growth in offspring mice (P < .05). MNE also significantly increased serum levels of total bile acid, triglycerides, total cholesterol, glucose, alanine aminotransferase, aspartate aminotransferase, low-density lipoprotein, and insulin while decreasing serum high-density lipoprotein levels and mitochondrial respiration activity in mice fed either the normal diet or high-fat diet (all P < .05). These effects of MNE on lipid metabolism and insulin resistance were mediated via PI3K and Akt phosphorylation and down-regulation of SREBP1c and PPAR-α.

CONCLUSION

Our data indicate MNE induces lipid metabolism disorder and insulin resistance to promote MAFLD progression in adult offspring through activation of PI3K/Akt signaling and suppression of SREBP1c and PPARα protein expression.

Snail/HDAC1/2 mediate skeletal growth retardation in fetuses caused by prenatal nicotine exposure

Previous findings have confirmed that prenatal nicotine exposure (PNE) leads to retarded cartilage development in the fetal growth plate. It is characterized by insufficient matrix synthesis and decreased expression of matrix phenotype genes aggrecan (ACAN) and Col2A1 in the fetal growth plate chondrocytes; however, the specific molecular mechanism is yet unclear. This study intends to clarify the specific molecular mechanism of fetal osteochondral retardation caused by PNE through animal and cellular experiments. The present study demonstrated that in male offspring of the PNE group (the pregnant rats were subcutaneously administered nicotine 1.0 mg/kg twice per day (2.0 mg/kg.d) at GD11-20), the cartilage matrix of the fetal growth plate was lightly stained, the collagen was reduced, and expression of the matrix phenotype genes, ACAN and Col2A1, was significantly decreased. It was further found that PNE decreased histone acetylation (H3K9/H3K14) levels in the ACAN and Col2A1 promoter regions. Moreover, the expression of Snail and HDAC1/2 was increased in the PNE group. in vitro, the nicotine treatment at different concentrations elevated the expression of Snail/HDAC1/2 while decreasing the H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions. Snail-siRNA transfection partially abolished the nicotine-induced increase in HDAC1/2 expression and decreased the histone acetylation levels in the ACAN and Col2A1 promoter regions. Trichostatin A (TSA) treatment partially reversed the nicotine-induced changes in downstream parameters. In summary, PNE-induced decreased cartilage matrix synthesis in the fetal growth plate of male offspring is effectuated by Snail/HDAC1/2-mediated decreased H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions.

H3K9ac of TGFβRI in human umbilical cord: a potential biomarker for evaluating cartilage differentiation and susceptibility to osteoarthritis via a two-step strategy

Background

Epidemiological investigation and our previous reports indicated that osteoarthritis had a fetal origin and was closely associated with intrauterine growth retardation (IUGR). Human Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) could be programmable to “remember” early-life stimuli. Here, we aimed to explore an early-warning biomarker of fetal-originated adult osteoarthritis in the WJ-MSCs.

Methods

Firstly, two kinds of WJ-MSCs were applied to evaluate their chondrogenic potential in vitro through inducing chondrogenic differentiation as the first step of our strategy, one from newborns with IUGR and the other from normal newborns but treated with excessive cortisol during differentiation to simulate the excessive maternal glucocorticoid in the IUGR newborns. As for the second step of the strategy, the differentiated WJ-MSCs were treated with interleukin 1β (IL-1β) to mimic the susceptibility to osteoarthritis. Then, the expression and histone acetylation levels of transforming growth factor β (TGFβ) signaling pathway and the expression of histone deacetylases (HDACs) were quantified, with or without cortisol receptor inhibitor RU486, or HDAC4 inhibitor LMK235. Secondly, the histone acetylation and expression levels of TGFβRI were further detected in rat cartilage and human umbilical cord from IUGR individuals.

Results

Glycosaminoglycan content and the expression levels of chondrogenic genes were decreased in the WJ-MSCs from IUGR, and the expression levels of chondrogenic genes were further reduced after IL-1β treatment, while the expression levels of catabolic factors were increased. Then, serum cortisol level from IUGR individuals was found increased, and similar changes were observed in normal WJ-MSCs treated with excessive cortisol. Moreover, the decreased histone 3 lysine 9 acetylation (H3K9ac) level of TGFβRI and its expression were observed in IUGR-derived WJ-MSCs and normal WJ-MSCs treated with excessive cortisol, which could be abolished by RU486 and LMK235. At last, the decreased H3K9ac level of TGFβRI and its expression were further confirmed in the cartilage of IUGR rat offspring and human umbilical cords from IUGR newborn.

Conclusions

WJ-MSCs from IUGR individuals displayed a poor capacity of chondrogenic differentiation and an increased susceptibility to osteoarthritis-like phenotype, which was attributed to the decreased H3K9ac level of TGFβRI and its expression induced by high cortisol through GR/HDAC4. The H3K9ac of TGFβRI in human umbilical cord could be a potential early-warning biomarker for predicting neonatal cartilage dysplasia and osteoarthritis susceptibility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02234-8.

Effects of GH/IGF axis on bone and cartilage

Growth hormone (GH) and its mediator, the insulin-like growth factor-1 (IGF-1) regulate somatic growth, metabolism and many aspects of aging. As such, actions of GH/IGF have been studied in many tissues and organs over decades. GH and IGF-1 are part of the hypothalamic/pituitary somatotrophic axis that consists of many other regulatory hormones, receptors, binding proteins, and proteases. In humans, GH/IGF actions peak during pubertal growth and regulate skeletal acquisition through stimulation of extracellular matrix production and increases in bone mineral density. During aging the activity of these hormones declines, a state called somatopaguss, which associates with deleterious effects on the musculoskeletal system. In this review, we will focus on GH/IGF-1 action in bone and cartilage. We will cover many studies that have utilized congenital ablation or overexpression of members of this axis, as well as cell-specific gene-targeting approaches used to unravel the nature of the GH/IGF-1 actions in the skeleton in vivo.

Selection and Validation of the Optimal Panel of Reference Genes for RT-qPCR Analysis in the Developing Rat Cartilage

Real-time fluorescence quantitative PCR (RT-qPCR) is widely used to detect gene expression levels, and selection of reference genes is crucial to the accuracy of RT-qPCR results. Minimum Information for Publication of RT-qPCR Experiments (MIQE) proposes that using the panel of reference genes for RT-qPCR is conducive to obtaining accurate experimental results. However, the selection of the panel of reference genes for RT-qPCR in rat developing cartilage has not been well documented. In this study, we selected eight reference genes commonly used in rat cartilage from literature (GAPDH, ACTB, 18S, GUSB, HPRT1, RPL4, RPL5, and SDHA) as candidates. Then, we screened out the optimal panel of reference genes in female and male rat cartilage of fetus (GD20), juvenile (PW6), and puberty (PW12) in physiology with stability analysis software of genes expression. Finally, we verified the reliability of the selected panel of reference genes with the rat model of intrauterine growth retardation (IUGR) induced by prenatal dexamethasone exposure (PDE). The results showed that the optimal panel of reference genes in cartilage at GD20, PW6, and PW12 in physiology was RPL4 + RPL5, which was consistent with the IUGR model, and there was no significant gender difference. Further, the results of standardizing the target genes showed that RPL4 + RPL5 performed smaller intragroup differences than other panels of reference genes or single reference genes. In conclusion, we found that the optimal panel of reference genes in female and male rat developing cartilage was RPL4 + RPL5, and there was no noticeable difference before and after birth.

Articular damages in multi-generational female offspring due to prenatal caffeine exposure correlates with H3K9 deacetylation of TGFβ signaling pathway

Adverse environment during pregnancy could lead to maternal glucocorticoid overexposure in utero, and then induce the intrauterine growth retardation (IUGR) and the programmed change in cartilage development. The transforming growth factor β (TGFβ) signaling pathway plays a crucial role in the process of chondrogenesis, cartilage growth, development, maturation, and phenotype maintenance. Our previous results had shown that prenatal caffeine exposure (PCE) could result in the damaged articular cartilage in offspring rats. However, whether this change could transmit to multiple generations was still unknown. In this study, pregnant Wistar rats received either saline or caffeine (120 mg/kg, i.g.) once daily from gestational day 9-20 (GD9-20). The female offspring mated with normal male rats to generate the following generations. We obtained the articular cartilages in subsequent F1 to F3 female offspring. The H3K9 acetylation and expression of the TGFβ signaling pathway were detected; the content of the cartilage matrix was detected. The results showed that PCE reduced the H3K9 acetylation and the expression of the TGFβ signaling pathway, then reduced the extracellular matrix in F1, F2, and F3 generations. in vitro, corticosterone could induce the H3K9 deacetylation of the TGFβ signaling pathway, thus inhibiting the expression of the TGFβ signaling pathway and extracellular matrix. The overall results revealed that PCE induced a multi-generational damaged articular cartilage in female offspring rats, which was partially related to the maternal high glucocorticoid-induced H3K9 hypoacetylation of TGFβ signaling pathway.

Ryanodine receptor 1 mediated dexamethasone-induced chondrodysplasia in fetal rats

BACKGROUND

Osteoarthritis is caused by cartilage dysplasia and has fetal origin. Prenatal dexamethasone exposure (PDE) induced chondrodysplasia in fetal rats by inhibiting transforming growth factor β (TGFβ) signaling. This study aimed to determine the effect of dexamethasone on fetal cartilage development and illustrate the underlying molecular mechanism.

METHODS

Dexamethasone (0.2 mg/kg.d) was injected subcutaneously every morning in pregnant rats from gestational day (GD) 9 to GD21. Harvested fetal femurs and tibias at GD21 for immunofluorescence and gene expression analysis. Fetal chondrocytes were treated with dexamethasone (100, 250 and 500 nM), endoplasmic reticulum stress (ERS) inhibitor, and ryanodine receptor 1 (RYR1) antagonist for subsequent analyses.

RESULTS

In vivo, prenatal dexamethasone exposure (PDE) decreased the total length of the fetal cartilage, the proportion of the proliferation area and the cell density and matrix content in fetal articular cartilage. Moreover, PDE increased RYR1 expression and intracellular calcium levels and elevated the expression of ERS-related genes, while downregulated the TGFβ signaling pathway and extracellular matrix (ECM) synthesis in fetal chondrocytes. In vitro, we verified dexamethasone significantly decreased ECM synthesis through activating RYR 1 mediated-ERS.

CONCLUSIONS

PDE inhibited TGFβ signaling pathway and matrix synthesis through RYR1 / intracellular calcium mediated ERS, which ultimately led to fetal dysplasia. This study confirmed the molecular mechanism of ERS involved in the developmental toxicity of dexamethasone and suggested that RYR1 may be an early intervention target for fetal-derived adult osteoarthritis.

Subchondral bone dysplasia partly participates in prenatal dexamethasone induced-osteoarthritis susceptibility in female offspring rats

Prenatal dexamethasone exposure (PDE) induces developmental toxicities of multi-organs and susceptibility to multi-diseases in offspring. However, the effects of PDE on osteoarthritis susceptibility in adult offspring and its mechanism have not been reported. In the present study, we treated pregnant Wistar rats with dexamethasone (0.2 mg/kg) daily on gestational days (GD) 9-20. Some pregnant rats were sacrificed on GD20, and the rest were delivered to obtain the postnatal offspring. The adult female offspring rats were performed with ovariectomy or sham operation during postnatal weeks 22-28. We found that PDE led to osteoarthritis phenotypes in articular cartilage and an increase in modified Mankin's score, but reduced the cartilage thickness in female adult offspring rats, which were more evident after ovariectomy. Moreover, PDE reduced the bone mass of subchondral bone in female adult offspring, which was aggravated by ovariectomy. The correlation analysis results indicated that the osteoarthritic phenotype and cartilage thickness were closely associated with the decreased bone mass of subchondral bone induced by PDE. Further, PDE retarded the development of primary and secondary ossification centers, then led to subchondral bone dysplasia, which could be partly mediated by the inhibited osteogenic function before and after birth. Collectively, the subchondral bone dysplasia partly participated in osteoarthritis susceptibility induced by PDE in female offspring rats.

Effects of prenatal nicotine exposure on hepatic glucose and lipid metabolism in offspring rats and its hereditability

Prenatal nicotine exposure (PNE) could induce an increased susceptibility to multiple chronic diseases in adult offspring, that mainly caused by intrauterine maternal glucocorticoid (GC) over-exposure. We investigated the changes and inheritability of hepatic glucose and lipid metabolism caused by PNE, to decipher the possible intrauterine programming mechanism. Pregnant Wistar rats were administered subcutaneously with 2 mg/kg·d nicotine from gestational day (GD) 9∼20, and second-generation (F2) were set according to the mating between control females and PNE males. The results showed that serum phenotypes and hepatic enzymes of glucose and lipid metabolism were lower in F1 fetal rats of PNE but higher in the F1 adult rats. Meanwhile, the activated states of hepatic glucocorticoid-activation system, including type 1 and type 2 11β-hydroxysteroid dehydrogenases (Hsd11b1/2), nuclear receptor subfamily 3, group C, member 1 (Nr3c1) and CCAAT enhancer binding protein α (Cebpa), were positively correlated with serum corticosterone levels but negatively correlated with the histone acetylation (H3K27ac) and expression levels of insulin-like growth factor 1 (Igf1) before and after birth. Furthermore, serum phenotypes and hepatic enzymes of glucose and lipid metabolism were lower in both F2 fetal and adult rats of PNE, which were consistent with the hepatic changes of GC-IGF1 axis and the glucocorticoid-activation system. In conclusion, PNE could lead to inheritable changes of hepatic glucose and lipid metabolism, which are related to the intrauterine programming of GC-IGF1 axis induced by the glucocorticoid-activation system.

Reduced testicular steroidogenesis in rat offspring by prenatal nicotine exposure: Epigenetic programming and heritability via nAChR/HDAC4

Prenatal nicotine exposure (PNE) may lead to offspring's testicular dysplasia. Here, we confirmed the intergenerational effect of PNE on testosterone synthetic function and explored its epigenetic programming mechanism. Pregnant Wistar rats were injected subcutaneously with nicotine (2 mg/kg.d) from gestational day 9-20. Some dams were anesthetized to obtain fetal rats, the rest were allowed to spontaneous labor to generate F1 and F2 generation. In utero, PNE impaired testicular development and testosterone production. Meanwhile, the expression of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) were decreased both in F1 and F2 generations. Furthermore, PNE enhanced the expression of fetal testicular nicotinic acetylcholine receptors (nAChRs) and histone deacetylase 4 (HDAC4), while obviously weakened histone 3 lysine 9 acetylation (H3K9ac) level of StAR/3β-HSD promoter from GD20 to postnatal week 12 and even in F2 generation. In vitro, nicotine increased nAChRs and HDAC4 expression, and decreased the StAR/3β-HSD H3K9ac level and expression, as well as the testosterone production in Leydig cells. Antagonism of nAChRs and inhibition of HDAC4 reversed the aforementioned changes. In conclusion, PNE programmed testicular low steroidogenesis and its heritability in male offspring rats. The underlying mechanism was associated to the low-level programming of StAR/3β-HSD H3K9ac via nAChR/HDAC4.

Programming changes in GLUT1 mediated the accumulation of AGEs and matrix degradation in the articular cartilage of female adult rats after prenatal caffeine exposure

Osteoarthritis is associated with intrauterine growth retardation (IUGR) and abnormal glucose metabolism. Our laboratory previously reported that prenatal caffeine exposure (PCE) can induce intrauterine maternal glucocorticoid (GC) overexposure in IUGR offspring and increase susceptibility to osteoarthritis after birth. In the present study, we demonstrated the essential role of glucose transporter 1 (GLUT1) programming changes in the increased matrix degradation of articular cartilage and susceptibility to osteoarthritis in female PCE adult offspring. In vivo, we found that PCE decreased the matrix content but did not significantly change the expression of matrix degradation-related genes in the articular cartilage of female fetal rats. The decreased expression of IGF1 and GLUT1 and the content of advanced-glycation-end-products (AGEs) were also detected. At different postnatal stages (2, 6, and 12 weeks), the cartilage matrix content decreased while the degradation-related genes expression increased in the PCE group. Meanwhile, the expression of IGF1 and GLUT1 and AGEs content in the local cartilage increased. In vitro, the expression levels of IGF1 and GLUT1 were inhibited by corticosterone but remained unchanged under caffeine treatment. Exogenous IGF1 can reverse the corticosterone-induced decrease in GLUT1 expression and promote AGEs production, while mifepristone (a glucocorticoid receptor inhibitor) reversed the corticosterone-induced low expression of IGF1 and GLUT1. Exogenous AGEs can increase the expression of inflammatory factors (IL-6 and TNF-α) and degradation-related genes, and decrease the matrix synthesis-related genes expression in chondrocyte. In conclusion, the GC-IGF1-GLUT1 axis mediated intrauterine dysplasia of articular cartilage, increased accumulation of AGEs and matrix degradation after birth in PCE female offspring, thereby increasing their susceptibility to osteoarthritis in adulthood.

Association of Nicotine with Osteochondrogenesis and Osteoarthritis Development: The State of the Art of Preclinical Research

The deleterious effects of nicotine on various health conditions have been well documented. Although many orthopedic diseases are adversely affected by nicotine, little is known about its preclinical effects on chondrogenesis or osteogenesis, cartilage formation, osteoarthritis (OA), and osteochondral repair. A systematic review was conducted examining the current scientific evidence on the effects of nicotine on chondrogenesis or osteogenesis in vitro, possible consequences of prenatal nicotine exposure (PNE) on cartilage and OA susceptibility in the offspring, and whether nicotine affects OA development and osteochondral repair in vivo, always focusing on their underlying mechanisms. The data reveal dose-dependent effects on articular chondrocytes and on the chondrogenesis and osteogenesis of medicinal signaling cells in vitro, with lower doses often resulting in positive effects and higher doses causing negative effects. PNE negatively affects articular cartilage development and induces OA in the offspring without or with nicotine exposure. In contrast, protective effects on OA development were only reported in monosodium iodoacetate-induced small animal models. Finally, nicotine repressed MSC-based osteochondral repair in vivo. Future studies need to investigate dose-dependent clinical effects of smoking on cartilage quality in offspring, OA susceptibility and progression, and osteochondral repair more in detail, thus identifying possible thresholds for its pathological effects.

Excitotoxicity and compensatory upregulation of GAD67 in fetal rat hippocampus caused by prenatal nicotine exposure are associated with inhibition of the BDNF pathway

Prenatal nicotine exposure (PNE) can cause hypersensitivity of hypothalamic-pituitary-adrenal (HPA) axis in offspring with intrauterine growth retardation. The purpose of this study was to explore the original mechanism of intrauterine development that mediates hypersensitivity of the HPA axis in offspring due to PNE. Pregnant Wistar rats were injected subcutaneously with 2 mg/kg·d of nicotine on the 9th to the 20th gestational day (GD9-GD20) and the fetuses were extracted at GD20. Compared with the control group, fetal rats by PNE showed increased hippocampal apoptosis, reduced synaptic plasticity and downregulation of the brain-derived neurotrophic factor (BDNF) pathway, whereas glutamic acid decarboxylase 67 (GAD67) expression was upregulated. Rat fetal hippocampal H19-7/IGF1R cell lines were treated with different concentrations of nicotine (1, 10 and 100 μM) for 3 days, the extracellular fluid glutamate (Glu) level increased and similar effects were observed as in vivo. Intervention treatments caused the opposite results. These results indicated that PNE downregulates the BDNF pathway and mediates the hippocampal excitotoxicity; then, the compensatory upregulation of GAD67 causes the imbalance of signal output in the fetal hippocampus. The negative feedback regulation of the paraventricular hypothalamic nucleus by the hippocampus is unbalanced, eventually causing hypersensitivity of the HPA axis of the offspring.

Prenatal nicotine exposure retards osteoclastogenesis and endochondral ossification in fetal long bones in rats

This study investigated the mechanisms underlying the retarded development of long bone in fetus by prenatal nicotine exposure (PNE) which had been demonstrated by our previous work. Nicotine (2.0 mg/kg.d) or saline was injected subcutaneously into pregnant rats every morning from gestational day (GD) 9 to 20. Fetal femurs or tibias were harvested for analysis on GD 20. We found massive accumulation of hypertrophic chondrocytes and a delayed formation of primary ossification center (POC) in the fetal femur or tibia of rat fetus after PNE, which was accompanied by a decreased amount of osteoclasts in the POC and up-regulated expression of osteoprotegerin (OPG) but by no obvious change in the expression of receptor activator of NF-κB ligand (RANKL). In primary osteoblastic cells, both nicotine (0, 162, 1620, 16,200 ng/ml) and corticosterone (0, 50, 250, 1250 nM) promoted the mRNA expression of OPG but concentration-dependently suppressed that of RANKL. Furthermore, blocking α4β2-nicotinic acetylcholine receptor (α4β2-nAChR) or glucocorticoid receptor rescued the above effects of nicotine and corticosterone, respectively. In conclusion, retarded osteoclastogenesis may contribute to delayed endochondral ossification in long bone in fetal rats with PNE. The adverse effects of PNE may be mediated via the direct effect of nicotine and indirect effect of maternal corticosterone on osteoblastic cells.

Role of TGFβ Signaling in Maternal Ethanol-Induced Fetal Articular Cartilage Dysplasia and Adult Onset of Osteoarthritis in Male Rats

Based on our previous findings that prenatal ethanol exposure in offspring increased susceptibility to adult osteoarthritis, this study aimed to further investigate the direct toxicity of ethanol on fetal articular cartilage development. Rat bone marrow-derived stroma cells were capsulated in alginate beads, incubated in a chondrogenic differentiation medium, and cultured for 4 weeks with ethanol treatment at concentrations of 0, 4, 20, and 100 mM. Pregnant rats were treated with ethanol (4 g/kg/day) from gestational days (GDs) 9 to 20. At GD20 and postnatal weeks 2, 6, and 12, 8 male offspring were sacrificed, and 8 male offspring rats of 8-weeks old in each group were treated with or without intraarticular injection of papain for 4 weeks to verify the susceptibility of adult osteoarthritis. Ethanol treatment resulted in poor differentiation of bone marrow-derived stroma cells to chondrocytes and suppressed the expression of the transforming growth factor-β (TGFβ)-smad2/3-Sox9 signaling pathway. In animal experiments, the shape of articular cartilage in the ethanol treatment group was more disordered than that of the control group, the matrix was not deep, and the cartilage was thin, which showed poor cartilage development. The TGFβ signaling pathway in the ethanol treatment group was persistently low at all time points. After intraarticular injection of papain, histological analyses, and the Mankin score revealed increased cartilage destruction in the ethanol treatment group. Ethanol caused articular cartilage dysplasia that was programmed in adulthood via a low-functional TGFβ signaling pathway, and the tolerance of this articular cartilage to external stimuli was significantly decreased.

Histone hypo-acetylation of Sox9 mediates nicotine-induced weak cartilage repair by suppressing BMSC chondrogenic differentiation

BACKGROUND

Nicotine has negative effects on tissue repair, little research concerns its effect on the cartilage repair of tissue engineering stem cells. The present study aimed to investigate the effects of nicotine on the bone marrow-derived mesenchymal stem cells' (BMSCs) chondrogenic repair function of cartilage defects and explored the molecular mechanism.

METHODS

A cartilage defect model of rat was repaired by BMSC transplantation, and treated with nicotine or saline at 2.0 mg/kg/d in 12 weeks. Nicotine's effect on chondrogenic differentiation was studied by exposing BMSCs to nicotine at 0.1, 1, 10, and 100 μM, and methyllycaconitine (MLA), which is a selective α7-nicotinic acetylcholine receptor (nAChR) inhibitor and si-RNA of nuclear factor of activated T cells 2 (NFATc2), were used to verify the molecular mechanism of nicotine's effect.

RESULTS

Data showed that nicotine inhibited cartilage repair function by suppressing SRY-type high-mobility group box 9 (Sox9) in regenerated tissues. Further in vitro study demonstrated that nicotine enhanced intracellular Ca²⁺ and activity of calcineurin (CaN) through α7-nAChR, increased the nucleic expressions of NFATc2 and the bindings to SOX9 promoter, and thus reduced the acetylation of H3K9 and H3K14 in SOX9 promoter.

CONCLUSIONS

Findings from this study demonstrated that nicotine suppressed the chondrogenic differentiation of BMSCs in vivo and in vitro, which offers insight into the risk assessment of cartilage defect repair in a nicotine exposure population and its therapeutic target.

Sarcopenic osteoarthritis: a new entity in geriatric medicine?

PURPOSE

Osteoarthritis, a disease characterized by cartilage degradation, abnormal subchondral bone remodeling and some grade of inflammation, and sarcopenia, a condition of low muscle mass associated with reduced strength and function, are prevalent disorders in older adults. In this review, we examine what is known about the relationship between osteoarthritis and sarcopenia, with particular focus on the older population. We also discuss how osteoarthritis and sarcopenia may interact and affect each other in clinical progression and the potential benefits from developing treatments that address such muscular-skeletal interaction.

METHODS

We searched in Pubmed and Scopus through a combination of search and MESH terms, for osteoarthritis and sarcopenia.

RESULTS

Even if more literature is needed, there is increasing evidence that decline in lower limb muscle strength is associated with knee or hip osteoarthritis in a pathological network of pain, altered joint stability, maladapted postures and defective neuromuscular communication. At the cellular levels, chondrocytes and myoblasts share common pathways, and the close anatomical location of both cell types also suggest the possibility of paracrine communication.

CONCLUSIONS

Sarcopenia and osteoarthritis are significantly intercorrelated and in the near future should be considered as an only entity, as we have recently proposed for sarcopenia and osteoporosis. The treatment of both sarcopenia and osteoarthritis is based on physical exercise and nutritional interventions with the aim of improving cartilage, bone and muscle health. Future studies are needed, particularly to know the exact prevalence of sarcopenia in people with osteoarthritis, its peculiar consequences and the most appropriate treatments.

nAChRs-ERK1/2-Egr-1 signaling participates in the developmental toxicity of nicotine by epigenetically down-regulating placental 11β-HSD2

Impaired placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) activity which inactivates maternal glucocorticoids is associated with poor fetal growth and a higher risk of chronic diseases in adulthood. This study aimed to elucidate the epigenetically regulatory mechanism of nicotine on placental 11β-HSD2 expression. Pregnant Wistar rats were administered 1.0 mg/kg nicotine subcutaneously twice a day from gestational day 9 to 20. The results showed that prenatal nicotine exposure increased corticosterone levels in the placenta and fetal serum, disrupted placental morphology and endocrine function, and reduced fetal bodyweight. Meanwhile, histone modification abnormalities (decreased acetylation and increased di-methylation of histone 3 Lysine 9) on the HSD11B2 promoter and lower-expression of 11β-HSD2 were observed. Furthermore, the expression of nicotinic acetylcholine receptor (nAChR) α4/β2, the phosphorylation of extracellular regulated kinase 1/2 (ERK1/2) and Ets-like protein-1 (Elk-1), and the expression of early growth response-1 (Egr-1) were increased in the nicotine groups. In human BeWo cells, nicotine decreased 11β-HSD2 expression, increased nAChRα9 expression, and activated ERK1/2/Elk-1/Egr-1 signaling in the concentration (0.1-10 μM)-dependent manner. Antagonism of nAChRs, inhibition of ERK1/2 and Egr-1 knockdown by siRNA were able to block/abrogate the effects of nicotine on histone modification and expression of 11β-HSD2. Taken together, nicotine can impair placental structure and function, and induce fetal developmental toxicity. The underlying mechanism involves histone modifications and down-regulation of 11β-HSD2 through nAChRs/ERK1/2/Elk-1/Egr-1 signaling, which increases active glucocorticoids levels in the placenta and fetus, and eventually inhibits the fetal development.

miRNA‑27a regulates arthritis via PPARγ in vivo and in vitro

The present study investigated the role of microRNA (miR)‑27a in the development of arthritis and its mechanism of action. Initially, collagen was used to develop an in vivo rat model of arthritis. Changes in the miRs in the rats were analyzed. It was subsequently observed that miR‑27a expression was reduced in patients with arthritis, compared with the control group. In the present study an in vitro miR‑27a overexpression model of arthritis was established and it was observed that miR‑27a increased the proliferation of osteoblast‑like cells in vitro. miR‑27a overexpression promoted osteogenic differentiation, increased alkaline phosphatase (ALP) and osteoporosis (OST) content, induced insulin‑like growth factor binding protein-5 (IGFBP‑5) protein expression, reduced inflammation and suppressed peroxisome proliferator‑activated receptor γ (PPARγ) and matrix metalloproteinase-17 (MMP‑17) protein expression in arthritis. However, miR‑27a downregulation inhibited osteogenic differentiation, increased inflammation and PPARγ and MMP‑17 protein expression and suppressed ALP and OST content in an in vitro model of arthritis. The PPARγ inhibitor reduced the function of miR‑27a downregulation on arthritis. Therefore the results of the present study revealed that miR‑27a regulates arthritis via PPARγ.