Treadmill running exercise prevents senile osteoporosis and upregulates the Wnt signaling pathway in SAMP6 mice

Skeletal phenotypes and molecular mechanisms in aging mice

Aging is an inevitable physiological process, often accompanied by age-related bone loss and subsequent bone-related diseases that pose serious health risks. Research on skeletal diseases caused by aging in humans is challenging due to lengthy study durations, difficulties in sampling, regional variability, and substantial investment. Consequently, mice are preferred for such studies due to their similar motor system structure and function to humans, ease of handling and care, low cost, and short generation time. In this review, we present a comprehensive overview of the characteristics, limitations, applicability, bone phenotypes, and treatment methods in naturally aging mice and prematurely aging mouse models (including SAMP6, POLG mutant, LMNA, SIRT6, ZMPSTE24, TFAM, ERCC1, WERNER, and KL/KL-deficient mice). We also summarize the molecular mechanisms of these aging mouse models, including cellular DNA damage response, senescence-related secretory phenotype, telomere shortening, oxidative stress, bone marrow mesenchymal stem cell (BMSC) abnormalities, and mitochondrial dysfunction. Overall, this review aims to enhance our understanding of the pathogenesis of aging-related bone diseases.

An examination of the effect of exercise and creatine monohydrate on oral tissues

Although physical exercise is extremely important for health and a good lifestyle, it can trigger oxidative stress, inflammation, and muscle fatigue. The aim of this study was to determine changes in dental tissues and the mandible created by creatines monohydrate (CrM) supplementation together with low and high-intensity exercise (HIE). The study material comprised Balb/c male mices, which were separated into two groups for the application of low and HIE on a running band. CrM supplement was administered together with the exercise. At the end of the experiment period, dental tissue samples were surgically removed and examined histopathologically and immunohistochemically (TNF-α and lL-1β).As a result of the histopathological examinations, in the pulp, oedema, vascular congestion, and capillary dilatation were seen to be statistically significantly increased in the Group 3 mices that performed HIE compared to the control group (p = 0.001, p = 0.003, p = 0.001, respectively). A statistically significant increase was observed in periodontal ligament (PDL) degeneration, and disruption of the continuity and separation of collagen fibers in Group 3 compared to the control group (p = 0.001). In the immunohistochemical examination, TNF-α and IL-1β positivity was observed in Group 3, and this was significantly increased compared to the control group (p = 0.001, p = 0.000).Exposure of the mices to low and HIE caused histological and immunohistochemical changes in dental pulp and PDL, and it was determined that the use of CrM could have a protective effect against these changes. RESEARCH HIGHLIGHTS: The results of this study showed negative effects of HIE in the dental pulp and PDL, which play an important role in dental health. CrM was seen to be effective in preventing these negative effects.

The current insights of mitochondrial hormesis in the occurrence and treatment of bone and cartilage degeneration

It is widely acknowledged that aging, mitochondrial dysfunction, and cellular phenotypic abnormalities are intricately associated with the degeneration of bone and cartilage. Consequently, gaining a comprehensive understanding of the regulatory patterns governing mitochondrial function and its underlying mechanisms holds promise for mitigating the progression of osteoarthritis, intervertebral disc degeneration, and osteoporosis. Mitochondrial hormesis, referred to as mitohormesis, represents a cellular adaptive stress response mechanism wherein mitochondria restore homeostasis and augment resistance capabilities against stimuli by generating reactive oxygen species (ROS), orchestrating unfolded protein reactions (UPRmt), inducing mitochondrial-derived peptides (MDP), instigating mitochondrial dynamic changes, and activating mitophagy, all prompted by low doses of stressors. The varying nature, intensity, and duration of stimulus sources elicit divergent degrees of mitochondrial stress responses, subsequently activating one or more signaling pathways to initiate mitohormesis. This review focuses specifically on the effector molecules and regulatory networks associated with mitohormesis, while also scrutinizing extant mechanisms of mitochondrial dysfunction contributing to bone and cartilage degeneration through oxidative stress damage. Additionally, it underscores the potential of mechanical stimulation, intermittent dietary restrictions, hypoxic preconditioning, and low-dose toxic compounds to trigger mitohormesis, thereby alleviating bone and cartilage degeneration.

Finite element modeling and analysis of effect of preexisting cervical degenerative disease on the spinal cord during flexion and extension

Recent studies have emphasized the importance of dynamic activity in the development of myelopathy. However, current knowledge of how degenerative factors affect the spinal cord during motion is still limited. This study aimed to investigate the effect of various types of preexisting herniated cervical disc and the ligamentum flavum ossification on the spinal cord during cervical flexion and extension. A detailed dynamic fluid-structure interaction finite element model of the cervical spine with the spinal cord was developed and validated. The changes of von Mises stress and maximum principal strain within the spinal cord in the period of normal, hyperflexion, and hyperextension were investigated, considering various types and grades of disc herniation and ossification of the ligamentum flavum. The flexion and extension of the cervical spine with spinal canal encroachment induced high stress and strain inside the spinal cord, and this effect was also amplified by increased canal encroachments and cervical hypermobility. The spinal cord might evade lateral encroachment, leading to a reduction in the maximum stress and principal strain within the spinal cord in local-type herniation. Although the impact was limited in the case of diffuse type, the maximum stress tended to appear in the white matter near the encroachment site while compression from both ventral and dorsal was essential to make maximum stress appear in the grey matter. The existence of canal encroachment can reduce the safe range for spinal cord activities, and hypermobility activities may induce spinal cord injury. Besides, the ligamentum flavum plays an important role in the development of central canal syndrome.Significance. This model will enable researchers to have a better understanding of the influence of cervical degenerative diseases on the spinal cord during extension and flexion.

Effects of acute- and long-term aerobic exercises at different intensities on bone in mice

INTRODUCTION

Exercise intensity determines the benefits of aerobic exercise. Our objectives were, in aerobic exercise at different intensities, to determine (1) changes in bone metabolism-related genes after acute exercise and (2) changes in bone mass, strength, remodeling, and bone formation-related proteins after long-term exercise.

MATERIALS AND METHODS

Total 36 male C57BL/6J mice were divided into a control group and exercise groups at 3 different intensities: low, moderate, or high group. Each exercise group was assigned to acute- or long-term exercise groups. Tibias after acute exercise were evaluated by real-time PCR analysis. Furthermore, hindlimbs of long-term exercise were assessed by micro-CT, biomechanical, histological, and immunohistochemical analyses.

RESULTS

Acute moderate-intensity exercise decreased RANKL level as bone resorption marker, whereas low- and high-intensity exercise did not alter it. Additionally, only long-term exercise at moderate intensity increased bone mass and strength. Moderate-intensity exercise promoted osteoblast activity and suppressed osteoclast activity. After low- and high-intensity exercise, osteoblast and osteoclast activity were unchanged. An increase in the number of β-catenin-positive cells and a decrease in sclerostin-positive cells were observed in the only moderate group.

CONCLUSION

These results showed that moderate-intensity exercise can inhibit bone resorption earlier, and long-term exercise can increase bone mass and strength through promoted bone formation via the Wnt/β-catenin activation. High-intensity exercise, traditionally considered better for bone, may fail to stimulate bone remodeling, leading to no change in bone mass and strength. Our findings suggest that moderate-intensity exercise, neither too low nor high, can maintain bone health.

Exercise improved bone health in aging mice: a role of SIRT1 in regulating autophagy and osteogenic differentiation of BMSCs

Introduction

This study was designed to investigate the effect of running exercise on improving bone health in aging mice and explore the role of the SIRT1 in regulating autophagy and osteogenic differentiation of Bone marrow Mesenchymal Stem Cells (BMSCs).

Methods

Twelve-month-old male C57BL/6J mice were used in this study as the aging model and were assigned to treadmill running exercise for eight weeks. Non-exercise male C57BL/6J mice of the same old were used as aging control and five-month-old mice were used as young controls. BMSCs were isolated from mice and subjected to mechanical stretching stimulation in vitro.

Results

The results showed that aging mice had lower bone mass, bone mineral density (BMD), and autophagy than young mice, while running exercise improved BMD and bone mass as well as upregulated autophagy in bone cells. Mechanical loading increased osteogenic differentiation and autophagy in BMSCs, and knockdown of SIRT1 in BMSCs demonstrated that SIRT1-regulated autophagy involved the mechanical loading activation of osteogenic differentiation.

Conclusion

Taken together, this study revealed that exercise improved bone health during aging by activating bone formation, which can be attributed to osteogenic differentiation of BMSCs through the activation of SIRT1-mediated autophagy. The mechanisms underlying this effect may involve mechanical loading.

The role and regulation mechanism of Chinese traditional fitness exercises on the bone and cartilage tissue in patients with osteoporosis: A narrative review

Osteoporosis (ops) is a systemic degenerative bone disease characterized by bone mass reduction, bone mineral density loss, bone microstructure destruction, bone fragility, and increased fracture susceptibility. Thus far, drug therapy is the main method used to prevent and treat osteoporosis. However, long-term drug treatment will inevitably lead to drug resistance and certain side effects. In response, rehabilitation treatment is generally recommended, which involves drug supplementation combined with the treatment. A Chinese traditional fitness exercise is an organic combination of sports and traditional Chinese medicine with a series of advantages such as being safe, convenient, non-toxic, and harmless. Hence, it is one of the rehabilitation methods widely used in clinical practice. By searching the CNKI, PubMed, Web of Science, Embase, Cochrane Library, and other relevant databases, our research clarifies the current situation of four kinds of Chinese traditional fitness exercises widely used in clinical practice, namely, Taijiquan, Baduanjin, Wuqinxi, and Yijin Jing. In addition, the molecular mechanism of osteoporosis is summarized in this study. Based on the research, Chinese traditional fitness exercises are expected to directly stimulate the bone through a mechanical load to improve bone density. Moderate and regular traditional Chinese fitness exercises also improve osteoporosis by regulating the endocrine system with the secretion of hormones and factors such as estrogen and irisin, which are beneficial for bone formation. Finally, the purpose of promoting bone formation, reducing bone loss, and preventing and treating osteoporosis is achieved. The various means of Chinese traditional fitness exercises have different emphases, and the effect of improving bone density differs in various parts of the body. The exercisers may choose the exercise flexibly based on their own needs. Chinese traditional fitness exercises can improve the bone density of the exercisers and relieve pain, improve balance, and regulate the psychological state. Consequently, it is worth promoting to be applied in clinical practices.

Study on the Role of MicroRNA-214 in the Rehabilitation of Cartilage in Mice with Exercise-Induced Traumatic Osteoarthritis

This study aimed to explore the possible relationship between the expression of Micro RNA-214 (miR-214) and the pathogenesis and recovery in mice with post-traumatic osteoarthritis (PTOA). In this study, 40 male C57BL/6 mice were randomly divided into five groups: model control (MC) group, model (M) group, rehabilitation control (RC) group, model + rehabilitation (M + R) group, and model + convalescent (M + C) group. Four weeks of high-intensity treadmill exercise (HITE) and 4 weeks of moderate-intensity treadmill exercise (MITE) were implemented for PTOA modeling and rehabilitation, respectively. In vitro, 10% elongation mechanical strain was used for IL-1β stimulated chondrocytes. We found that compared with the MC group, there was a significant increase in the aspect of inflammation and catabolism while a dramatic fall in miR-214 expression was observed in the M group. After the 4 weeks of MITE, the level of inflammation and metabolism, as well as miR-214 expression, was partially reversed in the M + R group compared with the M + C group. The expression of miR-214 decreased dramatically after chondrocyte stimulation by IL-1β and then increased significantly after 10% strain was applied to IL-1β-treated cells. These results suggest that a suitable mechanical load can increase the expression of miR-214, and that miR-214 may play a chondroprotective effect in the development of OA.

Effects of different-intensity exercise and creatine supplementation on mitochondrial biogenesis and redox status in mice

Objectives

Dietary supplementation combined with exercise may potentiate the beneficial effects of exercise by reducing exercise-induced oxidative stress and improving mitochondrial quality and capacity. In this study, the effects of creatine monohydrate (CrM) supplementation with low and high-intensity exercise on mitochondrial biogenesis regulators, Nrf2 anti-oxidant signaling pathway and muscle damage levels were investigated.

Materials and Methods

Balb/c male mice were divided into six experimental groups: control, control+CrM, high-intensity exercise, high-intensity exercise+CrM, low-intensity exercise, and low-intensity exercise+CrM. Mice were given CrM supplementation and at the same time, low and high-intensity exercise was applied to the groups on the treadmill at 30min/5day/8week. Then, mitochondrial biogenesis marker (PGC-1α, NRF-1, TFAM), Nrf2 and HO-1 protein expressions, total oxidant-anti-oxidant status level, and histopathological changes were investigated in serum and muscle tissue.

Results

Exercise intensity and CrM supplementation were found to be effective factors in mitochondrial biogenesis induction via the PGC-1α signaling pathway. Nrf2 and HO-1 protein levels increased with exercise intensity, and this result was directly related to serum oxidative stress markers. In addition, CrM supplementation was effective in reducing exercise-induced muscle damage.

Conclusion

This combination induced skeletal muscle adaptations, including mitochondrial biogenesis and enhanced anti-oxidant reserves. This synergistic effect of dietary supplementation with low-intensity exercise may be valuable as a complement to treatment, especially in diseases caused by mitochondrial dysfunction.

Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis

Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.

Effects of exercise on the expression of long non-coding RNAs in the bone of mice with osteoporosis

Physical activity or exercise are known to promote bone formation and decrease bone resorption to maintain skeletal and bone health both in animal models and in humans with osteoporosis. Previous studies have indicated that long non-coding RNAs (lncRNAs) are able to regulate bone metabolism. Therefore, the present study aimed to evaluate whether lncRNAs responded to exercise by regulating the balance of bone metabolism in order to prevent osteoporosis. To meet this end, ovariectomized mice were used in the present study to establish an osteoporosis model. The exercise treatment groups were subjected to 9 weeks of treadmill running exercise in 4 weeks of the operation was performed Femurs were collected to measure bone mineral density, bone mass, bone formation and resorption. The expression levels of lncRNAs were subsequently measured using microarray and gene function analyses. The pairwise comparison results [ovariectomy (OVX) vs. OVX + exercise (EX); OVX vs. SHAM; SHAM vs. SHAM + EX; OVX + EX vs. SHAM + EX] of the gene microarray analysis revealed that the expression of 2,424 lncRNAs (1718 upregulated and 706 downregulated) were significantly altered in the mouse femurs following treadmill running. Gene Ontology (GO) analysis, incorporating the GO annotations ‘biological processes’, ‘molecular function’ and ‘cellular components’, of osteoporosis revealed that the VEGF, mTOR and NF-κB signaling pathways were potential targets of the lncRNAs. Moreover, it was possible to predict the target microRNAs (miRNAs) of six lncRNAs (LOC105246953, LOC102637959, NONMMUT014677, NONMMUT027251, ri|D130079K21|PX00187K16|1491 and NONMMUT006626), which suggested that the underlying mechanism by which lncRNAs respond to exercise involved bone regulation via lncRNA-miRNA sponge adsorption. Overall, these results suggested that the treadmill running exercise did regulate lncRNA expression in the bone, and that this was involved in the prevention of osteoporosis.

Multiple Applications of Different Exercise Modalities with Rodents

A large proportion of chronic diseases can be derived from a sedentary lifestyle. Raising physical activity awareness is indispensable, as lack of exercise is the fourth most common cause of death worldwide. Animal models in different research fields serve as important tools in the study of acute or chronic noncommunicable disorders. With the help of animal-based exercise research, exercise-mediated complex antioxidant and inflammatory pathways can be explored, which knowledge can be transferred to human studies. Whereas sustained physical activity has an enormous number of beneficial effects on many organ systems, these animal models are easily applicable in several research areas. This review is aimed at providing an overall picture of scientific research studies using animal models with a focus on different training modalities. Without wishing to be exhaustive, the most commonly used forms of exercise are presented.

Physical Exercise Exacerbates Acute Kidney Injury Induced by LPS via Toll-Like Receptor 4

Introduction: Lipopolysaccharide (LPS) is a systemic response-triggering endotoxin, which has the kidney as one of its first targets, thus causing acute injuries to this organ. Physical exercise is capable of promoting physiological alterations and modulating inflammatory responses in the infectious process through multiple parameters, including the toll-like receptor (TLR)-4 pathway, which is the main LPS signaling in sepsis. Additionally, previous studies have shown that physical exercise can be both a protector factor and an aggravating factor for some kidney diseases. This study aims at analyzing whether physical exercise before the induction of LPS endotoxemia can protect kidneys from acute kidney injury.

Methods: C57BL/6J male mice, 12 weeks old, were distributed into four groups: (1) sedentary (control, N = 7); (2) sedentary + LPS (N = 7); (3) trained (N = 7); and (4) trained + LPS (N = 7). In the training groups, the animals exercised 5×/week in a treadmill, 60 min/day, for 4 weeks (60% of max. velocity). Sepsis was induced in the training group by the application of a single dose of LPS (5 mg/kg i.p.). Sedentary animals received LPS on the same day, and the non-LPS groups received a saline solution instead. All animals were euthanized 24 h after the administration of LPS or saline.

Results: The groups receiving LPS presented a significant increase in serum urea (p < 0.0001) and creatinine (p < 0.001) concentration and renal gene expression of inflammatory markers, such as tumor necrosis factor alpha and interleukin-6, as well as TLRs. In addition, LPS promoted a decrease in reduced glutathione. Compared to the sedentary + LPS group, trained + LPS showed overexpression of a gene related to kidney injury (NGAL, p < 0.01) and the protein levels of LPS receptor TLR-4 (p < 0.01). Trained + LPS animals showed an expansion of the tubulointerstitial space in the kidney (p < 0.05) and a decrease in the gene expression of hepatic AOAH (p < 0.01), an enzyme involved in LPS clearance.

Conclusion: In contrast to our hypothesis, training was unable to mitigate the renal inflammatory response caused by LPS. On the contrary, it seems to enhance injury by accentuating endotoxin-induced TLR-4 signaling. This effect could be partly due to the modulation of a hepatic enzyme that detoxifies LPS.

Impact of long-lasting spontaneous physical activity on bone morphogenetic protein 4 in the heart and tibia in murine model of heart failure

Bone morphogenetic protein 4 (BMP4) plays an important role in bone remodeling and in heart failure pathogenesis. The aim of this study was to evaluate the effect of spontaneous physical activity on the expression of BMP4 in the heart and tibia of the transgenic (Tgαq*44) mice, representing a model of chronic heart failure. Tgαq*44 and wild-type FVB mice (WT) were randomly assigned either to sedentary or to trained groups undergoing 8 weeks of spontaneous wheel running. The BMP4 protein expression in heart and tibiae was evaluated using Western immunoblotting and the phosphorus and calcium in the tibiae was assessed using the X-ray microanalysis. BMP4 content in the hearts of the Tgαq*44-sedentary mice was by ~490% higher than in the WT-sedentary mice, whereas in tibiae the BMP4 content of the Tgαq*44-sedentary mice was similar to that in the WT-sedentary animals. Tgαq*44 mice revealed by ~28% poorer spontaneous physical activity than the WT mice. No effect of performed physical activity on the BMP4 content in the hearts of either in the Tgαq*44 or WT mice was observed. However, 8-week spontaneous wheel running resulted in a decrease in the BMP4 expression in tibiae (by ~43%) in the group of Tgαq*44 mice only, with no changes in their bone phosphorus and calcium contents. We have concluded that prolonged period of spontaneous physical exercise does not increase the risk of the progression of the BMP4-mediated pathological cardiac hypertrophy and does not affect bone mineral status in the chronic heart failure mice.

Impacts of exercise interventions on different diseases and organ functions in mice

Background

In recent years, much evidence has emerged to indicate that exercise can benefit people when performed properly. This review summarizes the exercise interventions used in studies involving mice as they are related to special diseases or physiological status. To further understand the effects of exercise interventions in treating or preventing diseases, it is important to establish a template for exercise interventions that can be used in future exercise-related studies.

Methods

PubMed was used as the data resource for articles. To identify studies related to the effectiveness of exercise interventions for treating various diseases and organ functions in mice, we used the following search language: (exercise [Title] OR training [Title] OR physical activity [Title]) AND (mice [title/abstract] OR mouse [title/abstract] OR mus [title/abstract]). To limit the range of search results, we included 2 filters: one that limited publication dates to "in 10 years" and one that sorted the results as "best match". Then we grouped the commonly used exercise methods according to their similarities and differences. We then evaluated the effectiveness of the exercise interventions for their impact on diseases and organ functions in 8 different systems.

Results

A total of 331 articles were included in the analysis procedure. The articles were then segmented into 8 systems for which the exercise interventions were used in targeting and treating disorders: motor system (60 studies), metabolic system (45 studies), cardio-cerebral vascular system (58 studies), nervous system (74 studies), immune system (32 studies), respiratory system (7 studies), digestive system (1 study), and the system related to the development of cancer (54 studies). The methods of exercise interventions mainly involved the use of treadmills, voluntary wheel-running, forced wheel-running, swimming, and resistance training. It was found that regardless of the specific exercise method used, most of them demonstrated positive effects on various systemic diseases and organ functions. Most diseases were remitted with exercise regardless of the exercise method used, although some diseases showed the best remission effects when a specific method was used.

Conclusion

Our review strongly suggests that exercise intervention is a cornerstone in disease prevention and treatment in mice. Because exercise interventions in humans typically focus on chronic diseases, national fitness, and body weight loss, and typically have low intervention compliance rates, it is important to use mice models to investigate the molecular mechanisms underlying the health benefits from exercise interventions in humans.

Molecular changes to tendons after collagenase-induced acute tendon injury in a senescence-accelerated mouse model

BACKGROUND

Aging impairs tendon healing and is a potential risk factor for chronic tendinitis. During normal aging, tendons undergo structural and biomechanical degenerative changes, accompanied by a reduction in the number of tenocytes and changes to their properties. However, molecular changes in aged tendons under inflammatory conditions are not well understood. The present study analyzed the molecular changes in collagenase induced acute tendon injury using a senescence-accelerated mouse (SAM) model.

METHODS

SAMP6 mice were used as an aging animal model and SAMR1 mice were used as a control to represent a senescence-resistant inbred strain. All the mice used in the study were 40 weeks old. Collagenase I from Clostridium histolyticum (20 μL) was injected percutaneously to the tendon-bone junction of the Achilles tendon. Two weeks after treatment, the Achilles tendons were harvested and stained using Picrosirius Red to determine collagen expression. Real-time PCR was performed to analyze gene expression of IL-6, tenomodulin, type I and type II collagen, MMP-9, TIMP-1, and TIMP-2.

RESULTS

Collagenase injection resulted in significantly higher gene expression of IL-6 but significantly lower tenomodulin expression compared with the control in SAMP6 and SAMR1 mice. In SAMP6 mice, gene expression of type III collagen and MMP-9 was significantly higher in the collagenase-injected group compared with the control group. SAMP6 mice also showed lower expression of type I collagen, TIMP-1, and TIMP-2 in the collagenase-injected group compared with the control group. Picrosirius Red staining showed the highest expression of type III collagen in the collagenase-injected SAMP6 group compared with the other groups.

CONCLUSIONS

The collagenase-injected SAMP6 group showed higher expression of IL-6, MMP-9, and type III collagen and lower expression of type I collagen, TIMP-1, and TIMP-2, which are known to suppress metalloproteinases. The results indicate that aging may lead to dysfunction of the tendon healing process after acute tendon injury.

Regulation of Wnt signaling by physical exercise in the cell biological processes of the locomotor system

In the past decade, researches on Wnt signaling in cell biology have made remarkable progress regarding our understanding of embryonic development, bone formation, muscle injury and repair, neurogenesis, and tumorigenesis. The study also showed that physical activity can reverse age-dependent decline in skeletal muscle, preventing osteoporosis, regenerative neurogenesis, hippocampal function, cognitive ability, and neuromuscular junction formation, and the age-dependent recession is highly correlated with Wnt signaling pathways. However, how the biological processes in cell and physical activity during/following exercise affect the Wnt signaling path of the locomotor system is largely unknown. In this study, we first briefly introduce the important features of the cellular biological processes of exercise in the locomotor system. Then, we discuss Wnt signaling and review the very few studies that have examined Wnt signaling pathways in cellular biological processes of the locomotor system during physical exercise.

Transcriptome analysis of osteoblasts in an ovariectomized mouse model in response to physical exercise

Objectives

Osteoporosis is a metabolic disease resulting in progressive loss of bone mass as measured by bone mineral density (BMD). Physical exercise has a positive effect on increasing or maintaining BMD in postmenopausal women. The contribution of exercise to the regulation of osteogenesis in osteoblasts remains unclear. We therefore investigated the effect of exercise on osteoblasts in ovariectomized mice.

Methods

We compared the activity of differentially expressed genes of osteoblasts in ovariectomized mice that undertook exercise (OVX+T) with those that did not (OVX), using microarray and bioinformatics.

Results

Many inflammatory pathways were significantly downregulated in the osteoblasts after exercise. Meanwhile, IBSP and SLc13A5 gene expressions were upregulated in the OVX+T group. Furthermore, in in vitro assay, IBSP and SLc13A5 mRNAs were also upregulated during the osteogenic differentiation of MC3T3-E1 and 7F2 cells.

Conclusion

These findings suggest that exercise may not only reduce the inflammatory environment in ovariectomized mice, indirectly suppressing the overactivated osteoclasts, but may also directly activate osteogenesis-related genes in osteoblasts. Exercise may thus prevent the bone loss caused by oestrogen deficiency through mediating the imbalance between the bone resorptive activity of osteoclasts and the bone formation activity of osteoblasts.

Cite this article: W-B. Hsu, W-H. Hsu, J-S. Hung, W-J. Shen, R. W-W. Hsu. Transcriptome analysis of osteoblasts in an ovariectomized mouse model in response to physical exercise. Bone Joint Res 2018;7:601–608. DOI: 10.1302/2046-3758.711.BJR-2018-0075.R2.

Differential effects of high-fat diet and exercise training on bone and energy metabolism

Bone microarchitecture and strength are impaired by obesity and physical inactivity, but the underlying molecular regulation of bone metabolism in response to these factors is not well understood. Therefore, we analyzed bone and energy metabolism in male mice fed a high-fat or standard chow diet for 12 weeks with or without free access to running wheels. High-fat diet (HFD) mimicked the human condition of obesity and insulin resistance, including symptoms such as elevated serum glucose and insulin levels and reduced insulin-stimulated glucose uptake into muscle and adipose tissue. Interestingly, HFD also decreased (-44%) glucose uptake into bone marrow. Bone mass was reduced (-45%) by HFD due to a diminished (-45%) bone remodeling rate. Bone matrix quality aspects, such as biomechanical stability, were additionally decreased. Concurrently, the bone marrow adiposity increased (+63%) in response to a HFD. Further, we detected elevated expression of the Wnt signaling inhibitor dickkopf-1 (Dkk-1, +42%) in mice fed a HFD, but this was not reflected in serum samples obtained from obese humans. In mice, exercise attenuated the adverse effects of HFD by reversing the glucose uptake into bone marrow, improving the bone mass and bone matrix quality while decreasing the bone marrow adiposity. This data shows that exercise prevents some, but not all of the negative effects of HFD on bone health and suggests that insulin signaling in bone marrow and Dkk-1 signaling may be involved in the pathogenesis of bone loss induced by HFD.

Morphological and molecular characterization of the senile osteoporosis in senescence-accelerated mouse prone 6 (SAMP6)

Although the understanding of the complex pathogenesis for osteoporosis is appreciable, the underlying mechanism is not yet fully elucidated. There is a great need to further characterize the available animal models in osteoporosis research. The senescence-accelerated mouse prone 6 (SAMP6) mice have been developed as the spontaneous experimental model for senile osteoporosis. Here, we provide a comprehensive overview of current research regarding the bone morphological and molecular alterations and the possible mechanisms involved in these changes. There were significant decrease in trabecular bone mass at the axial and appendicular skeletal sites, with no marked alterations of cortical bone. Decreased bone formation on the endosteal surface and trabecular bone, and increased bone marrow adiposity were observed in SAMP6 mice. The elevated expression level of proliferator activator gamma (PPARγ) in the bone marrow suggest that PPARγ might regulate osteoblastic bone formation negatively in SAMP6 mice. The expression level of secreted frizzled-related protein 4 (Sfrp4) was found to be higher in SAMP6 mice. Sfrp4 is considered to suppress osteoblastic proliferation mediated by inhibition of Wnt signaling pathway. These findings may help us to gain more insight into the potential mechanism of senile osteoporosis.