Loss of the glycosyltransferase Galnt11 affects vitamin D homeostasis and bone composition.

O-glycosylation is a conserved posttranslational modification that impacts many aspects of organismal viability and function. Recent studies examining the glycosyltransferase Galnt11 demonstrated that it glycosylates the endocytic receptor megalin in the kidneys, enabling proper binding and reabsorption of ligands, including vitamin D-binding protein (DBP). Galnt11-deficient mice were unable to properly reabsorb DBP from the urine. Vitamin D plays an essential role in mineral homeostasis and its deficiency is associated with bone diseases such as rickets, osteomalacia, and osteoporosis. We therefore set out to examine the effects of the loss of Galnt11 on vitamin D homeostasis and bone composition. We found significantly decreased levels of serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, consistent with decreased reabsorption of DBP. This was accompanied by a significant reduction in blood calcium levels and a physiologic increase in parathyroid hormone (PTH) in Galnt11-deficient mice. Bones in Galnt11-deficient mice were smaller and displayed a decrease in cortical bone accompanied by an increase in trabecular bone and an increase in a marker of bone formation, consistent with PTH-mediated effects on bone. These results support a unified model for the role of Galnt11 in bone and mineral homeostasis, wherein loss of Galnt11 leads to decreased reabsorption of DBP by megalin, resulting in a cascade of disrupted mineral and bone homeostasis including decreased circulating vitamin D and calcium levels, a physiological increase in PTH, an overall loss of cortical bone, and an increase in trabecular bone. Our study elucidates how defects in O-glycosylation can influence vitamin D and mineral homeostasis and the integrity of the skeletal system.

The specificities, influencing factors, and medical implications of bone circadian rhythms.

Physiological processes within the human body are regulated in approximately 24-h cycles known as circadian rhythms, serving to adapt to environmental changes. Bone rhythms play pivotal roles in bone development, metabolism, mineralization, and remodeling processes. Bone rhythms exhibit cell specificity, and different cells in bone display various expressions of clock genes. Multiple environmental factors, including light, feeding, exercise, and temperature, affect bone diurnal rhythms through the sympathetic nervous system and various hormones. Disruptions in bone diurnal rhythms contribute to the onset of skeletal disorders such as osteoporosis, osteoarthritis and skeletal hypoplasia. Conversely, these bone diseases can be effectively treated when aimed at the circadian clock in bone cells, including the rhythmic expressions of clock genes and drug targets. In this review, we describe the unique circadian rhythms in physiological activities of various bone cells. Then we summarize the factors synchronizing the diurnal rhythms of bone with the underlying mechanisms. Based on the review, we aim to build an overall understanding of the diurnal rhythms in bone and summarize the new preventive and therapeutic strategies for bone disorders.

Fatty acid binding protein 4 (FABP4) induces chondrocyte degeneration via activation of the NF-κb signaling pathway.

The pathogenesis of osteoarthritis (OA) is still unclear. Fatty acid binding protein 4 (FABP4), a novel adipokine, has been found to play a role in OA. This study aimed to explore the role of NF-κB in FABP4-induced OA. In the in vivo study, four pairs of 12-week-old male FABP4 knockout (KO) and wild-type (WT) mice were included. The activation of NF-κB was assessed. In parallel, 24 6-week-old male C57/Bl6 mice were fed a high-fat diet (HFD) and randomly allocated to four groups: daily oral gavage with (1) PBS solution; (2) QNZ (NF-κB-specific inhibitor, 1 mg/kg/d); (3) BMS309403 (FABP4-specific inhibitor, 30 mg/kg/d); and (4) BMS309403 (30 mg/kg/d) + QNZ (1 mg/kg/d). The diet and treatment were sustained for 4 months. The knee joints were obtained to assess cartilage degradation, NF-κB activation, and subchondral bone sclerosis. In the in vitro study, a mouse chondrogenic cell line (ATDC5) was cultured. FABP4 was supplemented to stimulate chondrocytes, and the activation of NF-κB was investigated. In parallel, QNZ and NF-κB-specific siRNA were used to inhibit NF-κB. In vivo, the FABP4 WT mice had more significant NF-κB activation than the KO mice. Dual inhibition of FABP4 and NF-κB alleviated knee OA in mice. FABP4 has no significant effect on the activation of the JNK signaling pathway. In vitro, FABP4 directly activated NF-κB in chondrocytes. The use of QNZ and NF-κB-siRNA significantly alleviated the expression of catabolic markers of chondrocytes induced by FABP4. FABP4 induces chondrocyte degeneration by activating the NF-κB pathway.

Novel insights into the coupling of osteoclasts and resorption to bone formation.

Bone remodeling consists of resorption by osteoclasts (OCs) and formation by osteoblasts (OBs). Precise coordination of these activities is required for the resorbed bone to be replaced with an equal amount of new bone in order to maintain skeletal mass throughout the lifespan. This coordination of remodeling processes is referred to as the "coupling" of resorption to bone formation. In this review, we discuss the essential role for OCs in coupling resorption to bone formation, mechanisms for this coupling, and how coupling becomes less efficient or disrupted in conditions of bone loss. Lastly, we provide perspectives on targeting coupling to treat human bone disease.

Erythropoietin regulates osteoclast formation via up-regulating PPARγ expression.

Erythropoietin (EPO), expressed in red blood progenitor cells, primarily regulates erythropoiesis by binding to its receptor. Besides anemia, recent studies have identified new therapeutic indications for EPO that are not connected to red blood cell formation. Elevated EPO levels harm bone homeostasis in adult organisms and are associated with increased osteoclast; however, the underlying molecular mechanisms remain unclear. This study demonstrated that EPO enhanced osteoclast differentiation and bone resorption in vitro. We showed that EPO promoted osteoclast formation by up-regulating PPARγ expression through activating the Jak2/ERK signaling pathway. Consistently, PPARγ antagonists rescued the hyperactivation of osteoclasts due to EPO, while PPARγ agonists reversed the EMP9-mediated decrease in osteoclast differentiation. Further, exposing female mice to EPO for two months led to a decrease in bone mass and increased osteoclast numbers. The present results suggested that EPO promotes osteoclastogenesis by regulating the Jak2/ERK/ PPARγ signaling pathway. From a clinical perspective, the risk of compromised bone health should be considered when using EPO to treat anemia in post-operative patients with intertrochanteric fractures of the femur, as it could significantly impact the patient's recovery and quality of life.

Phf7 has impacts on the body growth and bone remodeling by regulating testicular hormones in male mice.

PHD finger protein 7 (Phf7) is a member of the PHF family proteins, which plays important roles in spermiogenesis. Phf7 is expressed in the adult testes and its deficiency causes male infertility. In this study, we tried to find the causal relationship between Phf7 deficiency and reduced growth retardation which were found in null knock-out (Phf7-/-) mice. Phf7-/- mice were born normally in the Mendelian ratio. However, the Phf7-/- males showed decreased body weight gain, bone mineral density, and bone mineral content compared to those in wild-type (WT) mice. Histological analysis for tibia revealed increased number of osteoclast cells in Phf7-/- mice compared with that in WT mice. When we analyzed the expressions for marker genes for the initial stage of osteoclastogenesis, such as receptor activator of nuclear factor kappa B (Rank) in tibia, there was no difference in the mRNA levels between Phf7-/- and WT mice. However, the expression of tartrate-resistant acid phosphatase (Trap), a mature stage marker gene, was significantly higher in Phf7-/- mice than in WT mice. In addition, the levels of testosterone and dihydrotestosterone (DHT), more potent and active form of testosterone, were significantly reduced in the testes of Phf7-/- mice compared to those in WT mice. Furthermore, testicular mRNA levels for steroidogenesis marker genes, namely Star, Cyp11a1, Cyp17a1 and 17ß-hsd, were significantly lower in Phf7-/- mice than in WT mice. In conclusion, these results suggest that Phf7 deficiency reduces the production of male sex hormones and thereby impairs associated bone remodeling.

Ciliopathic micrognathia is caused by aberrant skeletal differentiation and remodeling.

Ciliopathies represent a growing class of diseases caused by defects in microtubule-based organelles called primary cilia. Approximately 30% of ciliopathies are characterized by craniofacial phenotypes such as craniosynostosis, cleft lip/palate and micrognathia. Patients with ciliopathic micrognathia experience a particular set of difficulties, including impaired feeding and breathing, and have extremely limited treatment options. To understand the cellular and molecular basis for ciliopathic micrognathia, we used the talpid2 (ta2 ), a bona fide avian model for the human ciliopathy oral-facial-digital syndrome subtype 14. Histological analyses revealed that the onset of ciliopathic micrognathia in ta2 embryos occurred at the earliest stages of mandibular development. Neural crest-derived skeletal progenitor cells were particularly sensitive to a ciliopathic insult, undergoing unchecked passage through the cell cycle and subsequent increased proliferation. Furthermore, whereas neural crest-derived skeletal differentiation was initiated, osteoblast maturation failed to progress to completion. Additional molecular analyses revealed that an imbalance in the ratio of bone deposition and resorption also contributed to ciliopathic micrognathia in ta2 embryos. Thus, our results suggest that ciliopathic micrognathia is a consequence of multiple aberrant cellular processes necessary for skeletal development, and provide potential avenues for future therapeutic treatments.

The emerging role of the semaphorin family in cartilage and osteoarthritis.

In the pathogenesis of osteoarthritis, various signaling pathways may influence the bone joint through a common terminal pathway, thereby contributing to the pathological remodeling of the joint. Semaphorins (SEMAs) are cell-surface proteins actively involved in and primarily responsible for regulating chondrocyte function in the pathophysiological process of osteoarthritis (OA). The significance of the SEMA family in OA is increasingly acknowledged as pivotal. This review aims to summarize the mechanisms through which different members of the SEMA family impact various structures within joints. The findings indicate that SEMA3A and SEMA4D are particularly relevant to OA, as they participate in cartilage injury, subchondral bone remodeling, or synovitis. Additionally, other elements such as SEMA4A and SEMA5A may also contribute to the onset and progression of OA by affecting different components of the bone and joint. The mentioned mechanisms demonstrate the indispensable role of SEMA family members in OA, although the detailed mechanisms still require further exploration.

Analysis of the causal relationship between gut microbiota and bone remodeling growth factor from the gene association.

BACKGROUND: A growing body of evidence indicates a close association between the gut microbiota (GM) and the bone remodeling (BR) process, raising suspicions that the GM may actively participate in BR by modulating the levels of growth factors. However, the precise causal relationship between them remains unclear. Due to many confounding factors, many microorganisms related to BR growth factors have not been identified. We aimed to elucidate the causal relationship between the GM and BR growth factors. METHODS: We evaluated the genome-wide association study (GWAS) summary statistics for GM and five common growth factors associated with BR: namely, bone morphogenetic proteins (BMP), transforming growth factors(TGF), insulin growth factors (IGFs), epidermal growth factors (EGFs), and fibroblast growth factors (FGF). The causal relationship between the GM and BR growth factors was studied by double-sample Mendelian randomized analysis. We used five Mendelian randomization (MR) methods, including inverse variance-weighted (IVW), MR-Egger, simple mode, weighted median, and weighted model methods. RESULTS: Through MR analysis, a total of 56 bacterial genera were co-identified as associated with BMP, TGF, IGF, EGF, and FGF. Among them, eight genera were found to have a causal relationship with multiple growth factors: Marvinbryantia was causally associated with BMP-6 (P = 0.018, OR = 1.355) and TGF-ß2 (P = 0.002, OR = 1.475); Lachnoclostridium, BMP-7 (P = 0.021, OR = 0.73) and IGF-1 (P = 0.046, OR = 0.804); Terrisporobacter, TGF-ß (P = 0.02, OR = 1.726) and FGF-23 levels (P = 0.016, OR = 1.76); Ruminiclostridium5, TGF-ß levels (P = 0.024, OR = 0.525) and FGFR-2 (P = 0.003, OR = 0.681); Erysipelatoclostridium, TGF-ß2 (P = 0.001, OR = 0.739) and EGF and its receptor (EGFR) (P = 0.012, OR = 0.795); Eubacterium_brachy_group, FGFR-2 (P = 0.045, OR = 1.153) and EGF (P = 0.013, OR = 0.7); Prevotella9 with EGFR (P = 0.022, OR = 0.818) and FGFR-2 (P = 0.011, OR = 1.233) and Faecalibacterium with FGF-23 (P = 0.02, OR = 2.053) and IGF-1 (P = 0.005, OR = 0.843). CONCLUSION: We confirmed the causal relationship between the GM and growth factors related to BR, which provides a new perspective for the study of BR, through targeted regulation of specific bacteria to prevent and treat diseases and growth factor-mediated BR disorders.

Diagnosis and therapeutic approach to bone health in patients with hypopituitarism.

The results of many studies in recent years indicate a significant impact of pituitary function on bone health. The proper function of the pituitary gland has a significant impact on the growth of the skeleton and the appearance of sexual dimorphism. It is also responsible for achieving peak bone mass, which protects against the development of osteoporosis and fractures later in life. It is also liable for the proper remodeling of the skeleton, which is a physiological mechanism managing the proper mechanical resistance of bones and the possibility of its regeneration after injuries. Pituitary diseases causing hypofunction and deficiency of tropic hormones, and thus deficiency of key hormones of effector organs, have a negative impact on the skeleton, resulting in reduced bone mass and susceptibility to pathological fractures. The early appearance of pituitary dysfunction, i.e. in the pre-pubertal period, is responsible for failure to achieve peak bone mass, and thus the risk of developing osteoporosis in later years. This argues for the need for a thorough assessment of patients with hypopituitarism, not only in terms of metabolic disorders, but also in terms of bone disorders. Early and properly performed treatment may prevent patients from developing the bone complications that are so common in this pathology. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary disease.

Consideration of hormonal changes for orthodontic treatment during pregnancy and lactation - a review.

Hormonal changes in pregnant and lactating women significantly affect bone metabolism and overall stress levels, positioning them as a unique group within the orthodontic population. Fluctuations in estrogen, progesterone, prolactin, and other hormones are closely linked to bone remodeling and the periodontal tissue's response to inflammation caused by dental plaque. Hormones such as thyrotropin, leptin, and melatonin also play crucial roles in pregnancy and bone remodeling, with potential implications for orthodontic tooth movement. Additionally, adverse personal behaviors and changes in dietary habits worsen periodontal conditions and complicate periodontal maintenance during orthodontic treatment. Notably, applying orthodontic force during pregnancy and lactation may trigger stress responses in the endocrine system, altering hormone levels. However, these changes do not appear to adversely affect the mother or fetus. This review comprehensively examines the interaction between hormone levels and orthodontic tooth movement in pregnant and lactating women, offering insights to guide clinical practice.

Effects of Cannabidiol on Bone Quality in Ovariectomized Rats.

The incidence of osteoporosis and related fractures increases significantly with age, impacting public health and associated costs. Postmenopausal osteoporosis results from increased bone resorption due to decreased estrogen levels. The endocannabinoid system, especially cannabidiol (CBD), has shown therapeutic potential in modulating bone formation. This study investigated the effects of administration of CBD in rats after the onset of with ovariectomy-induced osteopenia (OVX). Forty-eight female Sprague‒Dawley rats were divided into four groups (n = 12): OVX + CBD, SHAM + CBD, OVX + vehicle, and SHAM + vehicle. CBD was administered intraperitoneally for 3 weeks. After euthanasia, the bone quality, mechanical properties, and bone microarchitecture of the femurs and lumbar vertebrae were assessed by microcomputed tomography (micro-CT), bone densitometry, mechanical tests, and histological and immunohistochemical analyses. CBD treatment improved the bone mineral density (BMD) of the lumbar vertebrae and increased the BV/TV% and Tb.N in the femoral neck. There were also improvements in the mechanical properties, such as the maximum force and stiffness of the femurs and vertebrae. CBD significantly increased the bone matrix in osteopenic femurs and vertebrae, Although did not significantly influence the expression of RANKL and OPG, in ovariectomized animals, there was an increase in osteoblasts and a decrease in osteoclasts. Determining the optimal timing for CBD use in relation to postovariectomy bone loss remains a crucial issue. Understanding when and how CBD can be most effective in preventing or treating bone loss is essential to emphasize the importance of early diagnosis and treatment of osteoporosis. However, further studies are needed to explore in more detail the efficacy and safety of CBD in the treatment of postmenopausal osteoporosis.

A static magnetic field improves bone quality and balances the function of bone cells with regulation on iron metabolism and redox status in type 1 diabetes.

Osteoporosis is one of the chronic complications of type 1 diabetes with high risk of fracture. The prevention of diabetic osteoporosis is of particular importance. Static magnetic fields (SMFs) exhibit advantages on improvement of diabetic complications. The biological effects and mechanism of SMFs on bone health of type 1 diabetic mice and functions of bone cells under high glucose have not been clearly clarified. In animal experiment, six-week-old male C57BL/6J mice were induced to type 1 diabetes and exposed to SMF of 0.4-0.7 T for 4 h/day lasting for 6 weeks. Bone mass, biomechanical strength, microarchitecture and metabolism were determined by DXA, three-point bending assay, micro-CT, histochemical and biochemical methods. Exposure to SMF increased BMD and BMC of femur, improved biomechanical strength with higher ultimate stress, stiffness and elastic modulus, and ameliorated the impaired bone microarchitecture in type 1 diabetic mice by decreasing Tb.Pf, Ct.Po and increasing Ct.Th. SMF enhanced bone turnover by increasing the level of markers for bone formation (OCN and Collagen I) as well as bone resorption (CTSK and NFAT2). In cellular experiment, MC3T3-E1 cells or primary osteoblasts and RAW264.7 cells were cultured in 25 mM high glucose-stimulated diabetic marrow microenvironment under differentiation induction and exposed to SMF. SMF promoted osteogenesis with higher ALP level and mineralization deposition in osteoblasts, and it also enhanced osteoclastogenesis with higher TRAP activity and bone resorption in osteoclasts under high glucose condition. Further, SMF increased iron content with higher FTH1 expression and regulated the redox level through activating HO-1/Nrf2 in tibial tissues, and lowered hepatic iron accumulation by BMP6-mediated regulation of hepcidin and lipid peroxidation in mice with type 1 diabetes. Thus, SMF may act as a potential therapy for improving bone health in type 1 diabetes with regulation on iron homeostasis metabolism and redox status.

Culture system for longitudinal monitoring of bone dynamics ex vivo.

To quantify and visualize both bone formation and resorption within osteochondral explants cultured ex vivo is challenging with the current analysis techniques. An approach that enables monitoring of bone remodeling dynamics is longitudinal microcomputed tomography (µCT), a non-destructive technique that relies on repeated µCT scanning and subsequent registration of consecutive scans. In this study, a two-compartment culture system suitable for osteochondral explants that allowed for µCT scanning during ex vivo culture was established. Explants were scanned repeatedly in a fixed orientation, which allowed assessment of bone remodeling due to adequate image registration. Using this method, bone formation was found to be restricted to the outer surfaces when cultured statically. To demonstrate that the culture system could capture differences in bone remodeling, explants were cultured statically and under dynamic compression as loading promotes osteogenesis. No quantitative differences between static and dynamic culture were revealed. Still, only in dynamic conditions, bone formation was visualized on trabecular surfaces located within the inner cores, suggesting enhanced bone formation towards the center of the explants upon mechanical loading. Taken together, the ex vivo culture system in combination with longitudinal µCT scanning and subsequent registration of images demonstrated potential for evaluating bone remodeling within explants.

Role of O-linked N-acetylglucosamine protein modification in oxidative stress-induced autophagy: a novel target for bone remodeling.

O-linked N-acetylglucosamine protein modification (O-GlcNAcylation) is a dynamic post-translational modification (PTM) involving the covalent binding of serine and/or threonine residues, which regulates bone cell homeostasis. Reactive oxygen species (ROS) are increased due to oxidative stress in various pathological contexts related to bone remodeling, such as osteoporosis, arthritis, and bone fracture. Autophagy serves as a scavenger for ROS within bone marrow-derived mesenchymal stem cells, osteoclasts, and osteoblasts. However, oxidative stress-induced autophagy is affected by the metabolic status, leading to unfavorable clinical outcomes. O-GlcNAcylation can regulate the autophagy process both directly and indirectly through oxidative stress-related signaling pathways, ultimately improving bone remodeling. The present interventions for the bone remodeling process often focus on promoting osteogenesis or inhibiting osteoclast absorption, ignoring the effect of PTM on the overall process of bone remodeling. This review explores how O-GlcNAcylation synergizes with autophagy to exert multiple regulatory effects on bone remodeling under oxidative stress stimulation, indicating the application of O-GlcNAcylation as a new molecular target in the field of bone remodeling.

Part II: A new perspective for modeling the bone remodeling process: Biology, mechanics, and pathologies.

In this paper, we explore the effects of biological (pathological) and mechanical damage on bone tissue within a benchmark model. Using the Finite Element Methodology, we analyze and numerically test the model's components, capabilities, and performance under physiologically and pathologically relevant conditions. Our findings demonstrate the model's effectiveness in simulating bone remodeling processes and self-repair mechanisms for micro-damage induced by biological internal conditions and mechanical external ones within bone tissue. This article is the second part of a series, where the first part presented the mathematical model and the biological and physical significance of the terms used in a simplified benchmark model. It explored the bone remodeling model's application, implementation, and results under physiological conditions.

Tumor growth for remodeling process: A 2D approach.

This paper aims to present a comprehensive framework for coupling tumor-bone remodeling processes in a 2-dimensional geometry. This is achieved by introducing a bio-inspired damage that represents the growing tumor, which subsequently affects the main populations involved in the remodeling process, namely, osteoclasts, osteoblasts, and bone tissue. The model is constructed using a set of differential equations based on the Komarova's and Ayati's models, modified to incorporate the bio-inspired damage that may result in tumor mass formation. Three distinct models were developed. The first two models are based on the Komarova's governing equations, with one demonstrating an osteolytic behavior and the second one an osteoblastic model. The third model is a variation of Ayati's model, where the bio-inspired damage is induced through the paracrine and autocrine parameters, exhibiting an osteolytic behavior. The obtained results are consistent with existing literature, leading us to believe that our in-silico experiments will serve as a cornerstone for paving the way towards targeted interventions and personalized treatment strategies, ultimately improving the quality of life for those affected by these conditions.

Inhibition of cysteine protease disturbs the topological relationship between bone resorption and formation in vitro.

INTRODUCTION: Osteoporosis is a global health issue. Bisphosphonates that are commonly used to treat osteoporosis suppress both bone resorption and subsequent bone formation. Inhibition of cathepsin K, a cysteine proteinase secreted by osteoclasts, was reported to suppress bone resorption while preserving or increasing bone formation. Analyses of the different effects of antiresorptive reagents such as bisphosphonates and cysteine proteinase inhibitors will contribute to the understanding of the mechanisms underlying bone remodeling. MATERIALS AND METHODS: Our team has developed an in vitro system in which bone remodeling can be temporally observed at the cellular level by 2-photon microscopy. We used this system in the present study to examine the effects of the cysteine proteinase inhibitor E-64 and those of zoledronic acid on bone remodeling. RESULTS: In the control group, the amount of the reduction and the increase in the matrix were correlated in each region of interest, indicating the topological and quantitative coordination of bone resorption and formation. Parameters for osteoblasts, osteoclasts, and matrix resorption/formation were also correlated. E-64 disrupted the correlation between resorption and formation by potentially inhibiting the emergence of spherical osteoblasts, which are speculated to be reversal cells in the resorption sites. CONCLUSION: These new findings help clarify coupling mechanisms and will contribute to the development of new drugs for osteoporosis.

Bone remodeling in survivors of pediatric hematopoietic stem cell transplantation: Impact of heavy resistance training.

BACKGROUND: Early-onset osteoporosis is a frequent late effect after pediatric hematopoietic stem cell transplantation (HSCT). It remains unknown if physical training can improve bone formation in these patients, as the transplantation procedure may cause sustained dysregulation of the bone-forming osteoblast progenitor cells. OBJECTIVE: We aimed to explore the effect of resistance training on bone remodeling in long-term survivors of pediatric HSCT. PROCEDURE: In this prospective, controlled intervention study, we included seven HSCT survivors and 15 age- and sex-matched healthy controls. The participants completed a 12-week heavy load, lower extremity resistance training intervention with three weekly sessions. We measured fasting serum levels of the bone formation marker "N-terminal propeptide of type I procollagen" (P1NP), and the bone resorption marker "C-terminal telopeptide of type I collagen" (CTX). The hypothesis was planned before data collection began. The trial was registered at Clinicaltrials.gov before including the first participant, with trial registration no. NCT04922970. RESULTS: Resistance training led to significantly increased levels of fasting P1NP in both patients (from 57.62 to 114.99 ng/mL, p = .03) and controls (from 66.02 to 104.62 ng/mL, p < .001). No significant changes in fasting CTX levels were observed. CONCLUSIONS: Despite previous high-dose cytotoxic therapy, long-term survivors of pediatric HSCT respond to resistance training with improvement of bone formation, comparable to that of healthy controls. This suggests that resistance training might be a promising non-pharmacological approach to prevent the early decline in bone mass, and should be considered as part of a follow-up program to counteract long-term sequela after pediatric HSCT.

p-Smad3 differentially regulates the cytological behavior of osteoclasts before and after osteoblasts maturation.

BACKGROUND: A series of previous investigations have revealed that p-Smad3 plays a facilitative role in the differentiation and maturation of osteoblasts, while also regulating the expression of certain intercellular communication factors. However, the effects of p-Smad3 in osteoblasts before and after maturation on the proliferation, migration, differentiation, apoptosis and other cellular behaviors of osteoclasts have not been reported. METHODS: MC3T3-E1 cells were cultured in osteogenic induction medium for varying durations, After that, the corresponding conditioned medium was collected and the osteoclast lineage cells were treated. To elucidate the regulatory role of p-Smad3 within osteoblasts, we applied the activator TGF-ß1 and inhibitor SIS3 to immature and mature osteoblasts and collected corresponding conditioned media for osteoclast intervention. RESULTS: We observed an elevation of p-Smad3 and Smad3 during the early stage of osteoblast differentiation, followed by a decline in the later stage. we discovered that as osteoblasts mature, their conditioned media inhibit osteoclasts differentiation and the osteoclast-coupled osteogenic effect. However, it promotes apoptosis in osteoclasts and the angiogenesis coupled with osteoclasts. p-Smad3 in immature osteoblasts, through paracrine effects, promotes the migration, differentiation, and osteoclast-coupled osteogenic effects of osteoclast lineage cells. For mature osteoblasts, p-Smad3 facilitates osteoclast apoptosis and the angiogenesis coupled with osteoclasts. CONCLUSIONS: As pre-osteoblasts undergo maturation, p-Smad3 mediated a paracrine effect that transitions osteoclast cellular behaviors from inducing differentiation and stimulating bone formation to promoting apoptosis and coupling angiogenesis.