Role of Ferroptosis in Bone Homeostasis and Traditional Chinese Medicine Intervention： A Review / 中国实验方剂学杂志

Osteoporosis （OP） is a systemic metabolic bone disease characterized by bone microstructure degeneration and bone mass loss， which has a high prevalence and disability rate. Effective prevention and treatment of OP is a major difficulty in the medical community. The nature of OP is that multiple pathological factors lead to the imbalance of human bone homeostasis maintained by osteoblasts and osteoclasts. Ferroptosis is a non-apoptotic cell death pathway， and its fundamental cause is cell damage caused by iron accumulation and lipid peroxidation. Studies have shown that ferroptosis is involved in and affects the occurrence and development of OP， which leads to OP by mediating the imbalance of bone homeostasis. Ferroptosis is an adjustable form of programmed cell death. The intervention of ferroptosis can regulate the damage degree and death process of osteoblasts and osteoclasts， which is beneficial to maintain bone homeostasis， slow down the development process of OP， improve the clinical symptoms of patients， reduce the risk of disability， and improve their quality of life. However， there are few studies on ferroptosis in OP. Traditional Chinese medicine （TCM） is a medical treasure with unique characteristics and great application value in China. It has been widely used in China and has a long history. It has the multi-target and multi-pathway advantages in the treatment of OP， with high safety， few toxic and side effects， and low treatment cost， and has a significant effect in clinical application. The intervention of TCM in ferroptosis to regulate bone homeostasis may be a new direction for the prevention and treatment of OP in the future. This article summarized the regulatory mechanisms related to ferroptosis， discussed the role of ferroptosis in bone homeostasis， and reviewed the current status and progress of active ingredients in TCM compounds and monomers in the regulation of OP through ferroptosis， so as to provide a theoretical basis for the participation of TCM in the prevention and treatment of OP in the future.

Mechanism of Bone Homeostasis Regulation by Autophagy in Osteoporosis and Intervention of Traditional Chinese Medicine： A Review / 中国实验方剂学杂志

Osteoporosis （OP） is a systemic metabolic bone disease caused by various factors， with a high incidence， and its pathogenesis is not yet clear. There is no specific drug for prevention and treatment， making it a significant global public health issue. In recent years， research has found that autophagy plays a role in the development of OP， and intervention in autophagy has become a hot topic in OP treatment. With further research， there has been a gradual increase in studies related to autophagy regulation by traditional Chinese medicine （TCM） to treat OP， and the treatment efficacy has been recognized. However， there is still a lack of systematic reviews on the mechanisms of autophagy in OP and the specific targets of TCM intervention in autophagy for OP treatment. Therefore， this article systematically reviewed the impact of autophagy on bone marrow mesenchymal stem cells （BMSCs）， osteoblasts， osteoclasts， and bone cells in the development of OP， as well as studies on TCM intervention in cell autophagy for OP treatment， aiming to provide a theoretical reference for the treatment of OP and further research in this field.

Targeting Kindlin-2 in adipocytes increases bone mass through inhibiting FAS/PPARγ/FABP4 signaling in mice

Osteoporosis (OP) is a systemic skeletal disease that primarily affects the elderly population, which greatly increases the risk of fractures. Here we report that Kindlin-2 expression in adipose tissue increases during aging and high-fat diet fed and is accompanied by decreased bone mass. Kindlin-2 specific deletion (K2KO) controlled by Adipoq-Cre mice or adipose tissue-targeting AAV (AAV-Rec2-CasRx-sgK2) significantly increases bone mass. Mechanistically, Kindlin-2 promotes peroxisome proliferator-activated receptor gamma (PPARγ) activation and downstream fatty acid binding protein 4 (FABP4) expression through stabilizing fatty acid synthase (FAS), and increased FABP4 inhibits insulin expression and decreases bone mass. Kindlin-2 inhibition results in accelerated FAS degradation, decreased PPARγ activation and FABP4 expression, and therefore increased insulin expression and bone mass. Interestingly, we find that FABP4 is increased while insulin is decreased in serum of OP patients. Increased FABP4 expression through PPARγ activation by rosiglitazone reverses the high bone mass phenotype of K2KO mice. Inhibition of FAS by C75 phenocopies the high bone mass phenotype of K2KO mice. Collectively, our study establishes a novel Kindlin-2/FAS/PPARγ/FABP4/insulin axis in adipose tissue modulating bone mass and strongly indicates that FAS and Kindlin-2 are new potential targets and C75 or AAV-Rec2-CasRx-sgK2 treatment are potential strategies for OP treatment.

Impacto del tratamiento de adultos mayores con ISRS y su relación con los tratamientos odontológicos / The impact of treating older adults with SSRI and its relationship with dental treatments

La población mayor de 60 años es el grupo etario de mayor crecimiento en el mundo. Debido a que la depresión es una patología frecuente en la persona adulta mayor y anciana, los inhibidores de la recap- tación de la serotonina (ISRS) son el tratamiento de primera línea de elección. Este trabajo referencia la asociación del consumo de estos fármacos con la disminución de la densidad ósea mineral (DMO), el riesgo de fracturas y su repercusión en la atención odontológica. Además, incluye una breve descripción de la homeostasis ósea y la relación depresión-carga alostática. El trabajo interdisciplinario y una correcta anamnesis pueden detectar posibles complicaciones y riesgos vinculados con este tipo de medicamen- tos. Ello facilitaría un mejor manejo, más aún en el adulto mayor, donde una pequeña variable puede repercutir en su integridad (AU)

The population over 60 is the fastest growing age group in the world. Depression is a frequent pathology in the elderly and the elderly, with serotonin reuptake inhibitors (SSRI) being the 1st line treatment of choice. The association of the consumption of this drug with a decrease in bone mineral density (BMD), risk of fractures and its impact on dental care are referenced in this work. In addition, it includes a brief description of bone homeostasis and the depression-allostatic load relationship. Interdisciplinary work and a correct anamnesis can detect possible complications and risks linked to this type of medication, facilitating better management and even more so in the elderly, where a small variable can affect their integrity (AU)

The pivotal role of autophagy in bone cells:bone-related cell activity and bone metabolism / 中国组织工程研究

BACKGROUND:The importance of autophagy for maintaining cellular homeostasis and stress response has long been recognized.As a way for cells to selectively clear their damaged organelles to achieve the recycling of cellular components,autophagy has a pivotal role in bone metabolism.OBJECTIVE:To review the role and possible mechanisms of autophagy in regulating bone-related cell activity and function among bone marrow mesenchymal stem cells,osteoblasts,osteocytes,and osteoclasts.METHODS:PubMed was searched for studies related to autophagy using the keywords of "autophagy;bone marrow mesenchymal stem cells;osteoblasts;osteocytes;osteoclasts."RESULTS AND CONCLUSION:We finally included 84 papers.Autophagy plays an important role in bone metabolism.Autophagy is involved in maintaining the balance between mineralization and absorption,and then maintaining bone homeostasis.An appropriate autophagy inducer may also benefit bone remodeling.Abnormal autophagy can lead to disorders of bone balance,leading to diseases such as osteoporosis.We may prevent or treat bone-related diseases by regulating the level of autophagy as its function in maintaining the balance of mineralization and resorption in bone homeostasis.

Study on the molecular mechanism of Cinnamomi Cortex-Rehmanniae Radix in preventing and treating osteoporosis based on multi-directional regulation of inflammatory factors, estrogen and bone homeostasis / 药学学报

In this study, the molecular mechanism of Cinnamomi Cortex-Rehmanniae Radix (CR) in the prevention and treatment of osteoporosis (OP) was investigated by integrating compatibility analysis of compound, bioinformatics and metabolomics. The rat OP models were established, and the Micro-CT indexes and pathological sections were comprehensively evaluated. The results showed that compared with the model group, the indexes such as bone mineral density (BMD) and bone volume/tissue volume (BV/TV) were significantly increased after CR treatment (P < 0.05), and the bone trabeculae were arranged into mesh. The results of UHPLC-Q-TOF/MS mainly involved amino acid metabolism, lipid metabolism and estrogen metabolism pathways. Integrating bioinformatics and metabolomics analysis, it was finally found that: ① cinnamic acid and ethylcinnamate inhibit inflammatory factors such as TNF, IL-1β, and IL-13, thereby preventing and treating OP; ② multiple active ingredients of CR target ESR2, PPARG, and CYP19A1, GABRA1 and other targets, regulate cAMP synthesis, AMPK signaling pathway and lipid metabolism, thereby regulating estrogen levels to prevent and treat OP; ③ oleic acid, arachic acid, etc. act on AR, VDR and other targets, and regulate HIF-1 signaling pathway and AGE-RAGE signaling pathway, thereby regulating osteoblasts and osteoclasts, and affecting calcium and phosphorus absorption to maintain bone homeostasis. This study clarified the molecular mechanism of CR in preventing and treating OP from the perspective of multi-directional regulation of inflammatory factors, estrogen and bone homeostasis, and provided theoretical basis for the clinical application of CR and the development of compound. This experiment complied with the ethical standards of animal experiments and was approved by the Animal Ethics Committee of Shaanxi University of Chinese Medicine (No. SUCMDL20210309002).

The Role of Signal Transducer and Activator of Transcription 3 in Bone Homeostasis and Load-Driven Bone Remodeling / 医用生物力学

Bone homeostasis is a relative balance between bone formation and resorption. Signal transducer and activator of transcription 3 (STAT3), which is closely related to bone homeostasis, takes part in multiple intracellular and extracellular signal pathways. STAT3 participates in the process of osteoblast differentiation regulated by several factors. It can also maintain bone homeostasis by regulating the recruitment, differentiation and activation of osteoclasts. In addition, STAT3 is involved in the interaction between osteoblasts and osteoclasts. Patients with STAT3 mutations can have several inherited bone metabolism diseases. Furthermore, STAT3 plays a critical role in load-driven bone remodeling. Mechanical stimulation promotes osteoblast differentiation and bone formation through activating or enhancing STAT3 expression during bone remodeling process. This review summarizes the participation of STAT3 in maintaining bone homeostasis together with its possible mechanisms and discusses the connection between STAT3 and mechanical stimulation in bone remodeling, so as to provide a potential pharmacological target for the treatment of bone diseases.

Role of Cytokines in Osteoporosis and Intervention with Traditional Chinese Medicine： A Review / 中国实验方剂学杂志

Osteoporosis （OP） is one of the most common diseases in the aged population worldwide. Due to the rapid change in world population structure， the effective prevention and treatment of OP is increasingly becoming the health problem of global concern and also the hot spot of clinical research. OP can be affected by many factors such as heredity， endocrine dyscrasia， nutritional deficiency， and bad living habits. The breakdown of coupling of osteoclast-mediated bone resorption to osteoblast-mediated bone formation leads to stronger bone resorption than bone formation， which is currently recognized as the main pathogenesis of OP. The exploration of OP in modern medicine based on molecular immunology has revealed that related cytokines play an important role in the pathogenesis of OP，and regulating the osteoclast-mediated bone resorption and osteoblast-mediated bone formation is essential for controlling the occurrence and development of OP. Tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， and interleukin-6 （IL-6） are able to stimulate bone formation and inhibit osteoblast function， thus playing a key role in bone destruction. By contrast， such cytokines as vascular endothelial growth factor （VEGF）， transforming growth factor-β （TGF-β）， bone morphogenetic protein （BMP）， and osteoprotegerin （OPG） strengthen osteoblast differentiation and promote bone formation. At present， western medicine like calcitonin， estrogen， and bisphosphonate are mostly used for clinical treatment of OP， but a long-term use of these drugs will result in poor compliance and obvious gastrointestinal adverse reactions. Traditional Chinese medicine （TCM） occupies an important position in the treatment of OP due to its advantages of overall regulation， low price， and few side effects. In addition， with the deepening of research on network pharmacology and molecular biology， it has been found that TCM exerts the therapeutic effect against OP by interfering with the expression of various cytokines and adjusting bone homeostasis. This paper has elaborated the role of related cytokines in the pathogenesis of OP and reviewed the research results concerning the regulation of related cytokines by TCM， in order to provide reference for the prevention and treatment of OP with TCM.

Macrophages can regulate bone homeostasis and erythropoiesis: Problems and prospects / 中国组织工程研究

BACKGROUND: Regulation of erythropoiesis in the bone marrow microenvironment is a carefully orchestrated process dependent upon systemic and local cues. Systemic erythropoietin production by renal interstitial cells plays a critical role in maintaining erythropoietic homeostasis. Increasing evidences have shown that erythropoietin and erythropoiesis can alter skeletal homeostasis, suggesting a functional relationship between the regulation of erythropoiesis and bone homeostasis. In recent years, macrophages play a regulatory role in erythropoietin, bone homeostasis and erythropoiesis. OBJECTIVE: To summarize the research advance concerning the role of macrophages in erythropoiesis and bone homeostasis. METHODS: PubMed, Medline, Web of Science, Wanfang and CNKI databases were retrieved with the keywords of “erythropoiesis, macrophage, erythropoietin, bone formation, bone homeostasis” in English and Chinese, respectively for relevant articles published from January 1999 to October 2019. Finally 48 articles eligible for inclusion and exclusion criteria were included for further analysis. RESULTS AND CONCLUSION: As key local components of the bone marrow microenvironment and erythropoietic niche, macrophage subsets play important roles in both processes. Peritoneum macrophages, glial macrophages and liver resident macrophages promote the production of erythropoietin in renal interstitium. Bone marrow macrophages or osteoma, osteoclasts and central macrophages regulate bone homeostasis, and further promote erythropoiesis.

Research progress on the relationship between osteocytes and periodontitis / 口腔疾病防治

@#Osteocytes, which develop from osteoblasts, are recognized as the main cells embedded in mature bone tissue. The traditional notion is that osteocytes exclusively play a structural role, however, with the development of related research in recent years, the role of osteocytes in bone metabolism has been explored. Periodontitis is a chronic inflammatory disease initiated by plaque biofilm, and is the main cause of adult tooth loss. Clinically, periodontitis primarily manifests as attachment loss, bleeding on probing and other symptoms. Alveolar bone resorption is the most characteristic pathological change. Current research demonstrated that osteocytes sense mechanical stress, participate in bone remodeling, regulate mineral balance, and participate in endocrine function. Thus, these cells play an important role in bone homeostasis and systemic metabolic balance. Osteocytes are actively involved in the development of periodontitis through the high expression of receptor activator of nuclear factor kappa B ligand (RANKL), secretion of sclerostin, and effect on apoptosis, senescence and autophagy. In the future, the detection of bone cell metabolism-related products will have certain application prospects for the clinical evaluation of periodontitis prevention and treatment. Therefore, this paper reviewed the role of osteocytes in bone homeostasis and the relationship between osteocytes and periodontitis, to provide new ideas for the prevention and treatment of periodontitis.

Research progress of roles of mammalian target of rapamycin signaling in bone homeostasis and associated diseases / 上海交通大学学报（医学版）

Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that integrates stimulation from intracellular and extracellular environment to control many fundamental processes through two distinct protein complexes, i.e., mTOR complex 1 (mTORC1) and mTORC2. Recent studies have found that mTOR pathways play important roles in skeletal development and homeostasis. In addition, mTORC1 mediates the bone anabolic effect through insulin-like growth factor 1 (IGF-1), Wnt, and bone morphogenetic protein (Bmp). Dysregulation of mTORC1 contributes to osteoarthritis and osteoporosis. This article reviewed the current understanding of mTOR signaling in skeletal development, bone homeostasis, and maintenance of articular cartilage, which provided a reference for the mechanism and treatment of skeletal diseases.

Essence of "Shen (Kidney) Controlling Bones": Conceptual Analysis Based on Hypothalamic-Pituitary-Adrenal-Osteo-Related Cells Axis / 中国结合医学杂志

As a traditional concept of Chinese medicine (CM), the theory of "Shen (Kidney) controlling bones" has been gradually proven. And in modern allopathic medicine, the multiple mechanisms of bone growth, development and regeneration align with the theory. Shen deficiency as a pathological condition has a negative effect on the skeleton of body, specifically the disorder of bone homeostasis. Present studies indicate that Shen deficiency shares a common disorder characterized by dysfunction of hypothalamic-pituitary-adrenal (HPA) axis. HPA axis may be an important regulator of bone diseases with abnormal homeostasis. Therefore, we posit the existence of hypothalamic-pituitary-adrenal-osteo-related cells axis: cells that comprise bone tissue (osteo-related cells) are targets under the regulation of HPA axis in disorder of bone homeostasis. Chinese herbs for nourishing Shen have potential in the development of treatments for disorder of bone homeostasis.

Recent Progress in Osteocyte Research

The last decade has seen an exponential increase in our understanding of osteocytes function and biology. These cells, once considered inert by-standers trapped into the mineralized bone, has now risen to be key regulators of skeletal metabolism, mineral homeostasis, and hematopoiesis. As tools and techniques to study osteocytes improved and expanded, it has become evident that there is more to these cells than initially thought. Osteocytes are now recognized not only as the key responders to mechanical forces but also as orchestrators of bone remodeling and mineral homeostasis. These cells are the primary source of several important proteins, such as sclerostin and fibroblast growth factor 23, that are currently target as novel therapies for bone loss (as the case for antisclerostin antibodies) or phosphate disorders. Better understanding of the intricate cellular and molecular mechanisms that govern osteocyte biology will open new avenue of research and ultimately indentify novel therapeutics to treat bone and mineral disorders. This review summarizes novel findings and discusses future avenues of research.

Recent Progress in Osteocyte Research

The last decade has seen an exponential increase in our understanding of osteocytes function and biology. These cells, once considered inert by-standers trapped into the mineralized bone, has now risen to be key regulators of skeletal metabolism, mineral homeostasis, and hematopoiesis. As tools and techniques to study osteocytes improved and expanded, it has become evident that there is more to these cells than initially thought. Osteocytes are now recognized not only as the key responders to mechanical forces but also as orchestrators of bone remodeling and mineral homeostasis. These cells are the primary source of several important proteins, such as sclerostin and fibroblast growth factor 23, that are currently target as novel therapies for bone loss (as the case for antisclerostin antibodies) or phosphate disorders. Better understanding of the intricate cellular and molecular mechanisms that govern osteocyte biology will open new avenue of research and ultimately indentify novel therapeutics to treat bone and mineral disorders. This review summarizes novel findings and discusses future avenues of research.