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

Emerging roles of nerve-bone axis in modulating skeletal system

Over the past decades, emerging evidence in the literature has demonstrated that the innervation of bone is a crucial modulator for skeletal physiology and pathophysiology. The nerve-bone axis sparked extensive preclinical and clinical investigations aimed at elucidating the contribution of nerve-bone crosstalks to skeleton metabolism, homeostasis, and injury repair through the perspective of skeletal neurobiology. To date, peripheral nerves have been widely reported to mediate bone growth and development and fracture healing via the secretion of neurotransmitters, neuropeptides, axon guidance factors, and neurotrophins. Relevant studies have further identified several critical neural pathways that stimulate profound alterations in bone cell biology, revealing a complex interplay between the skeleton and nerve systems. In addition, inspired by nerve-bone crosstalk, novel drug delivery systems and bioactive materials have been developed to emulate and facilitate the process of natural bone repair through neuromodulation, eventually boosting osteogenesis for ideal skeletal tissue regeneration. Overall, this work aims to review the novel research findings that contribute to deepening the current understanding of the nerve-bone axis, bringing forth some schemas that can be translated into the clinical scenario to highlight the critical roles of neuromodulation in the skeletal system.

Autonomic neural regulation in mediating the brain-bone axis: mechanisms and implications for regeneration under psychological stress

Efficient regeneration of bone defects caused by disease or significant trauma is a major challenge in current medicine, which is particularly difficult yet significant under the emerging psychological stress in the modern society. Notably, the brain-bone axis has been proposed as a prominent new concept in recent years, among which autonomic nerves act as an essential and emerging skeletal pathophysiological factor related to psychological stress. Studies have established that sympathetic cues lead to impairment of bone homeostasis mainly through acting on mesenchymal stem cells (MSCs) and their derivatives with also affecting the hematopoietic stem cell (HSC)-lineage osteoclasts, and the autonomic neural regulation of stem cell lineages in bone is increasingly recognized to contribute to the bone degenerative disease, osteoporosis. This review summarizes the distribution characteristics of autonomic nerves in bone, introduces the regulatory effects and mechanisms of autonomic nerves on MSC and HSC lineages, and expounds the crucial role of autonomic neural regulation on bone physiology and pathology, which acts as a bridge between the brain and the bone. With the translational perspective, we further highlight the autonomic neural basis of psychological stress-induced bone loss and a series of pharmaceutical therapeutic strategies and implications toward bone regeneration. The summary of research progress in this field will add knowledge to the current landscape of inter-organ crosstalk and provide a medicinal basis for the achievement of clinical bone regeneration in the future.

Course-, dose-, and stage-dependent toxic effects of prenatal acetaminophen exposure on fetal long bone development

Acetaminophen is a common analgesic and fever reduction medicine for pregnant women. Epidemiological studies suggest that prenatal acetaminophen exposure (PAcE) affects offspring health and development. However, the effects of PAcE on fetal long bone development and its potential mechanisms have not been elucidated. Based on clinical dosing characteristics, fetal mouse femurs were obtained for detection after oral gavage of acetaminophen at different doses (0, 100 or 400 mg/kg d), courses (single or multiple times) or stages (mid- or late pregnancy) during pregnancy in Kunming mice. The results showed that compared with the control group, PAcE reduced the length of total femur and the primary ossification center (POC), delayed the mineralization of POC and the ossification of epiphyseal region, and down-regulated the mRNA expression of osteogenic function markers (such as Runx2, Bsp, Ocn , Col1a1) in fetal femur, particularly in the high dose, multiple courses, and mid-pregnancy group. Meanwhile, the osteoclast and angiogenic function were also inhibited by PAcE at high dose, multiple courses, and mid-pregnancy, but the inhibition level was less than osteogenic function. Moreover, the alteration of canonical Wnt signalling pathway in PAcE fetal bone were consistent with its osteogenesis function changes. In conclusion, PAcE caused development toxicity and multi-cellular function inhibition in fetal long bone, particularly in the high dose, multiple treatments and mid-pregnancy group, and the alteration of canonical Wnt signalling pathway may be its potential mechanism.

Intrauterine exposure to nicotine through maternal vaping disrupts embryonic lung and skeletal development via the Kcnj2 potassium channel

Smoking cigarettes during pregnancy is associated with adverse effects on infants including low birth weight, defective lung development, and skeletal abnormalities. Pregnant women are increasingly turning to vaping [use of electronic (e)-cigarettes] as a perceived safer alternative to cigarettes. However, nicotine disrupts fetal development, suggesting that like cigarette smoking, nicotine vaping may be detrimental to the fetus. To test the impact of maternal vaping on fetal lung and skeletal development in mice, pregnant dams were exposed to e-cigarette vapor throughout gestation. At embryonic day (E)18.5, vape exposed litter sizes were reduced, and some embryos exhibited growth restriction compared to air exposed controls. Fetal lungs were collected for histology and whole transcriptome sequencing. Maternally nicotine vaped embryos exhibited histological and transcriptional changes consistent with impaired distal lung development. Embryonic lung gene expression changes mimicked transcriptional changes observed in adult mouse lungs exposed to cigarette smoke, suggesting that the developmental defects may be due to direct nicotine exposure. Fetal skeletons were analyzed for craniofacial and long bone lengths. Nicotine directly binds and inhibits the Kcnj2 potassium channel which is important for bone development. The length of the maxilla, palatal shelves, humerus, and femur were reduced in vaped embryos, which was further exacerbated by loss of one copy of the Kcnj2 gene. Nicotine vapor exposed Kcnj2KO/+ embryos also had significantly lower birth weights than unexposed animals of either genotype. Kcnj2 mutants had severely defective lungs with and without vape exposure, suggesting that potassium channels may be broadly involved in mediating the detrimental developmental effects of nicotine vaping. These data indicate that intrauterine nicotine exposure disrupts fetal lung and skeletal development likely through inhibition of Kcnj2.

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.

Nerves within bone and their application in tissue engineering of bone regeneration

Nerves within bone play an irreplaceable role in promoting bone regeneration. Crosstalk between the nerve system and bone has arisen to the attention of researchers in the field of basic medicine, clinical medicine, and biomaterials science. Successful bone regeneration relies on the appropriate participation of neural system components including nerve fibers, signaling molecules, and neural-related cells. Furthermore, more about the mechanisms through which nerves took part in bone regeneration and how these mechanisms could be integrated into tissue engineering scaffolds were under exploration. In the present review, we aimed to systematically elaborate on the structural and functional interrelationship between the nerve system and bone. In particular, peripheral nerves interact with the bone through innervated axons, multiple neurotrophins, and bone resident cells. Also, we aimed to summarize research that took advantage of the neuro-osteogenic network to design tissue engineering scaffolds for bone repair.

Developmental toxicity and programming alterations of multiple organs in offspring induced by medication during pregnancy

Medication during pregnancy is widespread, but there are few reports on its fetal safety. Recent studies suggest that medication during pregnancy can affect fetal morphological and functional development through multiple pathways, multiple organs, and multiple targets. Its mechanisms involve direct ways such as oxidative stress, epigenetic modification, and metabolic activation, and it may also be indirectly caused by placental dysfunction. Further studies have found that medication during pregnancy may also indirectly lead to multi-organ developmental programming, functional homeostasis changes, and susceptibility to related diseases in offspring by inducing fetal intrauterine exposure to too high or too low levels of maternal-derived glucocorticoids. The organ developmental toxicity and programming alterations caused by medication during pregnancy may also have gender differences and multi-generational genetic effects mediated by abnormal epigenetic modification. Combined with the latest research results of our laboratory, this paper reviews the latest research progress on the developmental toxicity and functional programming alterations of multiple organs in offspring induced by medication during pregnancy, which can provide a theoretical and experimental basis for rational medication during pregnancy and effective prevention and treatment of drug-related multiple fetal-originated diseases.

Hallmarks of peripheral nerve function in bone regeneration

Skeletal tissue is highly innervated. Although different types of nerves have been recently identified in the bone, the crosstalk between bone and nerves remains unclear. In this review, we outline the role of the peripheral nervous system (PNS) in bone regeneration following injury. We first introduce the conserved role of nerves in tissue regeneration in species ranging from amphibians to mammals. We then present the distribution of the PNS in the skeletal system under physiological conditions, fractures, or regeneration. Furthermore, we summarize the ways in which the PNS communicates with bone-lineage cells, the vasculature, and immune cells in the bone microenvironment. Based on this comprehensive and timely review, we conclude that the PNS regulates bone regeneration through neuropeptides or neurotransmitters and cells in the peripheral nerves. An in-depth understanding of the roles of peripheral nerves in bone regeneration will inform the development of new strategies based on bone-nerve crosstalk in promoting bone repair and regeneration.

Developmental programming of macrophages by early life adversity

Macrophages are central elements of all organs, where they have a multitude of physiological and pathological functions. The first macrophages are produced during fetal development, and most adult organs retain populations of fetal-derived macrophages that self-maintain without major input of hematopoietic stem cell-derived monocytes. Their developmental origins make macrophages highly susceptible to environmental perturbations experienced in early life, in particular the fetal period. It is now well recognized that such adverse developmental conditions contribute to a wide range of diseases later in life. This chapter explores the notion that macrophages are key targets of environmental adversities during development, and mediators of their long-term impact on health and disease. We first briefly summarize our current understanding of macrophage ontogeny and their biology in tissues and consider potential mechanisms by which environmental stressors may mediate fetal programming. We then review evidence for programming of macrophages by adversities ranging from maternal immune activation and diet to environmental pollutants and toxins, which have disease relevance for different organ systems. Throughout this chapter, we contemplate appropriate experimental strategies to study macrophage programming. We conclude by discussing how our current knowledge of macrophage programming could be conceptualized, and finally highlight open questions in the field and approaches to address them.

The cholinergic system in joint health and osteoarthritis: a narrative-review

Osteoarthritis (OA) poses a major health and economic burden worldwide due to an increasing number of patients and the unavailability of disease-modifying drugs. In this review, the latest understanding of the involvement of the cholinergic system in joint homeostasis and OA will be outlined. First of all, the current evidence on the presence of the cholinergic system in the normal and OA joint will be described. Cholinergic innervation as well as the non-neuronal cholinergic system are detected. In a variety of inflammatory diseases, the classic cholinergic anti-inflammatory pathway lately received a lot of attention as via this pathway cholinergic agonists can reduce inflammation. The role of this cholinergic anti-inflammatory pathway in the context of OA will be discussed. Activation of this pathway improved the progression of the disease. Secondly, chondrocyte hypertrophy plays a pivotal role in osteophyte formation and OA development; the impact of the cholinergic system on hypertrophic chondroblasts and endochondral ossification will be evaluated. Cholinergic stimulation increased chondrocyte proliferation, delayed chondrocyte differentiation and caused early mineralisation. Moreover, acetylcholinesterase and butyrylcholinesterase affect the endochondral ossification via an acetylcholine-independent pathway. Thirdly, subchondral bone is critical for cartilage homeostasis and metabolism; the cholinergic system in subchondral bone homeostasis and disorders will be explored. An increase in osteoblast proliferation and osteoclast apoptosis is observed. Lastly, current therapeutic strategies for OA are limited to symptom relief; here the impact of smoking on disease progression and the potential of acetylcholinesterase inhibitors as candidate disease-modifying drug for OA will be discussed.

Crosstalk between Bone and Nerves within Bone

For the past two decades, the function of intrabony nerves on bone has been a subject of intense research, while the function of bone on intrabony nerves is still hidden in the corner. In the present review, the possible crosstalk between bone and intrabony peripheral nerves will be comprehensively analyzed. Peripheral nerves participate in bone development and repair via a host of signals generated through the secretion of neurotransmitters, neuropeptides, axon guidance factors and neurotrophins, with additional contribution from nerve-resident cells. In return, bone contributes to this microenvironmental rendezvous by housing the nerves within its internal milieu to provide mechanical support and a protective shelf. A large ensemble of chemical, mechanical, and electrical cues works in harmony with bone marrow stromal cells in the regulation of intrabony nerves. The crosstalk between bone and nerves is not limited to the physiological state, but also involved in various bone diseases including osteoporosis, osteoarthritis, heterotopic ossification, psychological stress-related bone abnormalities, and bone related tumors. This crosstalk may be harnessed in the design of tissue engineering scaffolds for repair of bone defects or be targeted for treatment of diseases related to bone and peripheral nerves.

Triclosan induces apoptosis in Burkitt lymphoma-derived BJAB cells through caspase and JNK/MAPK pathways

Burkitt's lymphoma (BL) is the fastest growing human tumor. Current treatment consists of a multiagent regimen of cytotoxic drugs with serious side effjects including tumor lysis, cardiotoxicity, hepatic impairment, neuropathy, myelosuppression, increased susceptibility to malignancy, and death. Furthermore, therapeutic interventions in areas of BL prevalence are not as feasible as in high-income countries. Therefore, there exists an urgent need to identify new therapies with a safer profile and improved accessibility. Triclosan (TCS), an antimicrobial used in personal care products and surgical scrubs, has gained considerable interest as an antitumor agent due to its interference with fatty acid synthesis. Here, we investigate the antitumor properties and associated molecular mechanisms of TCS in BL-derived BJAB cells. Dose-dependent cell death was observed following treatment with 10-100 µM TCS for 24 h, which was associated with membrane phospholipid scrambling, compromised permeability, and cell shrinkage. TCS-induced cell death was accompanied by elevated intracellular calcium, perturbed redox balance, chromatin condensation, and DNA fragmentation. TCS upregulated Bad expression and downregulated that of Bcl2. Moreover, caspase and JNK MAPK signaling were required for the full apoptotic activity of TCS. In conclusion, this report identifies TCS as an antitumor agent and provides new insights into the molecular mechanisms governing TCS-induced apoptosis in BL cells.

Oral Exposure to ZnO Nanoparticles Disrupt the Structure of Bone in Young Rats via the OPG/RANK/RANKL/IGF-1 Pathway

Purpose

To evaluate the effects of ZnO NPs on bone growth in rats and explore the possible mechanisms of action.

Materials and Methods

Three-week-old male rats received ultrapure water or 68, 203, and 610 mg/kg zinc oxide nanoparticles (ZnO NPs) for 28 days, orally.

Results

The high-dosage groups caused significant differences in weight growth rate, body length, and tibia length (P<0.05), all decreasing with increased ZnO NP dosage. There were no significant differences in body mass index (BMI) (P>0.05). The zinc concentration in liver and bone tissue increased significantly with increased ZnO NP dosage (P<0.05). Clearly increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were observed in the 610 mg/kg ZnO NP group (P>0.05), whereas alkaline phosphatase (ALP) increased in the 610 mg/kg ZnO NP group (P<0.05). Significant differences in insulin-like growth factor type 1 (IGF-1) levels and a decrease in calcium (Ca) levels were observed in 203 and 610 mg/kg ZnO NP groups (P<0.05). Phosphorus (P) levels increased and the Ca/P ratio decreased in the 610 mg/kg ZnO NP group (P<0.05). Micro-computed tomography (micro-CT) of the tibia demonstrated signs of osteoporosis, such as decreased bone density, little trabecular bone structure and reduced cortical bone thickness. Micro-CT data further demonstrated significantly decreased bone mineral density (BMD), trabecular number (Tb.N), and relative bone volume (BV/TV) with increasing dosage of ZnO NPs. Osteoprotegerin (OPG) expression and the ratio of OPG to receptor activator of nuclear factor-κB ligand (RANKL) were statistically lower in the 610 mg/kg ZnO NP group (P<0.05), whereas RANKL expression did not change significantly (P>0.05).

Conclusion

We infer that ZnO NPs affect bone growth in young rats directly or indirectly by altering IGF-1 levels. Overall, the results indicate that ZnO NPs promote osteoclast activity and increase bone loss through the OPG/RANK/RANKL/IGF-1 pathway.

Antenatal Dexamethasone Exposure Impairs the High-Conductance Ca2+-Activated K+ Channels via Epigenetic Alteration at Gene Promoter in Male Offspring

OBJECTIVE

Antenatal exposure to glucocorticoids increases cardiovascular risks related to vascular dysfunctions in offspring, although underlying mechanisms are still unknown. As an important vascular mediator, high-conductance Ca²⁺-activated K⁺ channels (BK) plays an essential role in determining vascular tone. Long-term effects of antenatal glucocorticoids on BK in offspring are largely unknown. This study examined the effects and mechanisms of antenatal exposure to clinically relevant doses of glucocorticoids on vascular BK in offspring. Approach and Results: Pregnant Sprague-Dawley rats received synthetic glucocorticoids dexamethasone or vehicle during the last week of pregnancy. Vascular functions, cellular electrophysiology, target gene expression, and promoter methylation were examined in mesenteric arteries of male offspring (gestational day 21 [fetus] and postnatal day 120 [adult offspring]). Antenatal dexamethasone exposure impaired BK activators-mediated relaxation and reduced whole-cell BK currents in mesenteric arteries. Antenatal dexamethasone exposure did not alter Ca²⁺/voltage-sensitivity of BK but downregulated the expressions of BK α and β1 subunits in both fetal and adult mesenteric arteries. In addition, increased promoter methylations within BKα and BKβ1 were compatible with reduced expressions of the 2 genes.

CONCLUSIONS

Our findings showed a profound and long-term impact of antenatal dexamethasone exposure on vascular BK via an altered epigenetic pattern from fetal stage to adulthood, advancing understanding of prolonged adverse effects and mechanisms of antenatal glucocorticoids exposure on vascular health in offspring.

Nicotine exposure during pregnancy programs osteopenia in male offspring rats via α4β2-nAChR-p300-ACE pathway

Prenatal nicotine exposure (PNE) induces developmental toxicity in offspring. However, the long-term harmful effects on bone development and the intrauterine programming mechanism attributed to PNE remain unclear. In the present research, pregnant Wistar rats were injected subcutaneously with nicotine (2 mg/kg/d) to obtain and analyze bone samples from the fetal and adult offspring. Bone marrow mesenchymal stem cells (BMSCs) were treated with nicotine during osteogenic differentiation to clarify the related molecular mechanisms. The results indicated that PNE led to bone dysplasia in the fetuses and reduced bone mass in the adult offspring, which was mediated by the sustained activation of the local bone renin angiotensin system (RAS) and suppressed osteogenic differentiation before and after birth. In vitro, nicotine suppressed BMSCs' osteogenic function through promoting angiotensin-converting enzyme (ACE) expression and activating RAS. Furthermore, nicotine induced histone acetylase p300 into the nuclei of the BMSCs by acting on the α4β2-nicotinic acetylcholine receptor (α4β2-nAChR), leading to the increased histone 3 lysine 9 acetylation level of ACE and RAS activation. Taken together, the sustained activation of local bone RAS mediated prenatal nicotine-induced osteopenia in adult offspring via the α4β2-nAChR-p300-ACE pathway.-Xiao, H., Wen, Y., Pan, Z., Shangguan, Y., Magdalou, J., Wang, H., Chen, L. Nicotine exposure during pregnancy programs osteopenia in male offspring rats via α4β2-nAChR-p300-ACE pathway.

Descriptive and risk factor analysis of nonsyndromic sacral agenesis: National Birth Defects Prevention Study, 1997-2011

Sacral agenesis is a rare birth defect characterized by partial or complete absence of the sacrum. We sought to (a) describe case characteristics, (b) estimate birth prevalence, and (c) identify risk factors for nonsyndromic sacral agenesis using data from the National Birth Defects Prevention Study (NBDPS). The NBDPS was a population-based, case-control study involving pregnancies with estimated dates of delivery from October 1997 through December 2011. We estimated birth prevalence using all NBDPS eligible cases. Using self-reported maternal exposure information, we conducted multivariable logistic regression analysis to identify potential risk factors overall and among women without diabetes. The birth prevalence of sacral agenesis was 2.6/100,000 live births. In the multivariable analysis, multifetal pregnancy, pre-existing Type 1 diabetes, and pre-existing Type 2 diabetes were positively and significantly associated with sacral agenesis, albeit estimates were imprecise. Preexisting Type 1 diabetes was the strongest risk factor (adjusted odds ratio = 96.6, 95% confidence interval = 43.5-214.7). Among women without diabetes, periconceptional smoking was positively and significantly associated with sacral agenesis. Our findings underscore the importance of smoking cessation programs among women planning pregnancy and the importance of better understanding the role of glycemic control before and during pregnancy when designing interventions for primary prevention of sacral agenesis.