Arbutin ameliorates glucocorticoid-induced osteoporosis through activating autophagy in osteoblasts

Calycosin alleviates ovariectomy-induced osteoporosis by promoting BMSCs autophagy via the PI3K/Akt/mTOR pathway

Calycosin, the main extract from the traditional Chinese medicine (TCM) Astragalus membranaceus, has demonstrated anti-osteoporotic properties in ovariectomized (OVX) mice. However, the specific pathways through which it prevents osteoporosis remain unexplored. This study aimed to investigate the pathways by which calycosin promotes autophagy in bone marrow mesenchymal stem cells (BMSCs) and alleviates ovariectomy-induced osteoporosis. Mice were divided into three groups: sham, OVX, and OVX + calycosin. Following a 12-week intervention period, assessments included analysis of bone microstructure, serum concentrations of LC3II and ALP, and evaluation of Trap expression in femoral tissue. Immunohistochemical staining was used to assess the expression levels of PI3K, Runx2, and Beclin-1 in bone tissue. Additionally, levels of Runx2, ALP, p-PI3K, PI3K, mTOR, p-mTOR, Beclin-1, and ULK1 were analyzed. Osteogenic differentiation of BMSCs was evaluated using ALP and Alizarin red staining. OVX significantly impaired BMSCs osteogenic differentiation, resulting in bone loss. In contrast, calycosin increased bone mass, promoted osteogenesis, and reduced cancellous bone loss. Parameters, such as BMD, BV/TV, Tb.N, and Tb.Th, were significantly higher in the OVX + calycosin group compared to the OVX group. Additionally, Tb.Sp was notably reduced in the OVX + calycosin group. Calycosin also upregulated levels of Runx2, ALP, p-PI3K, p-mTOR, ULK1, and Beclin-1. In cellular studies, calycosin promoted BMSCs osteogenesis under OVX conditions; however, this effect was inhibited by LY294002. Calycosin effectively combats bone loss and improves bone structure. Its mechanism likely involves the promotion of autophagy in osteoblasts, thereby stimulating BMSC osteogenic differentiation. This effect may be mediated through the PI3K/Akt/mTOR pathway. These findings suggest that calycosin has the potential to serve as an alternative therapy for treating osteoporosis.

CUL1 exacerbates glucocorticoid-induced osteoporosis by enhancing ASAP1 ubiquitination

BACKGROUND

Glucocorticoid-induced osteoporosis is a leading secondary cause of osteoporosis. Cullin-1 (CUL1) levels are abnormally elevated in patients with osteoporosis, but the underlying mechanism remains unclear. The purpose of this study was to elucidate the mechanism of action of CUL1 in a glucocorticoid (dexamethasone, Dex)-induced osteoporosis model.

METHODS

C57BL/6J mice were intraperitoneally injected with Dex to establish an osteoporosis model. Mouse femur bone injury and bone formation were detected using hematoxylin-eosin or Masson staining. Apoptosis and cell cycle distribution were determined by flow cytometry. Alkaline phosphatase (ALP) activity and calcified nodules were monitored using ALP and Alizarin Red S staining. The molecular mechanism was validated by co-immunoprecipitation (Co-IP) and ubiquitination assays.

RESULTS

CUL1 expression was enhanced in the Dex-induced osteoporosis mouse model. CUL1 silencing moderated the Dex-induced cell proliferation and osteogenesis inhibition. Moreover, CUL1 promoted the ubiquitination and degradation of ASAP1 via the SKP1-CUL1-F-box (SCF)-FBXW7 complex. CUL1 induced apoptosis and repressed osteogenesis by ASAP1. CUL1 silencing alleviated the Dex-induced osteoporosis in mice.

CONCLUSION

CUL1 suppressed osteoblast proliferation and osteogenesis by promoting ASAP1 ubiquitination via the SCF-FBXW7 complex in glucocorticoid-induced osteoporosis.

Anti-aging chitosan/gelatin film crosslinked byα-arbutin for bone regeneration by free radical scavenging to prevent osteoblast senescence

Osteoblasts play a critical role in maintaining bone homeostasis. Senescence causes by free radical-mediated oxidative stress may affect the viability and osteogenic differentiation potential of osteoblast during bone formation. To eliminate the impacts of senescent cells by free radical scavenging is an optimal option for bone regeneration in age-related bone disease, such as osteoporosis (OP) and periodontitis. In this study, we fabricated an antioxidant film (CG-ARB) by crosslinking chitosan (C) and gelatin (G) usingα-Arbutin (ARB) as a crosslinker. The morphological, physicochemical, and radical scavenging characteristics of the films were investigated. Its antioxidative ability to prevent osteoblast senescence for restoration of osteogenic differentiation was analyzedin vitro. A Sprague-Dawley rat model with critical size calvarial defect was used to evaluate the bone regeneration and biosafetyin vivo. The results demonstrated that CG-ARB formed a dense fiber membrane, allowing for the gradual and sustained release of ARB for at least 10 d. ARB exerted antioxidant effect that prevented osteoblast senescencein vitroand promote bone healingin vivo. Furthermore, CG-ARB did not cause hemolysis or organ toxicity, and was therefore, considered biosafe. These results indicated that CG-ARB film could be an ideal drug delivery system for sustained released of ARB in bone defect repair.

Arbutin attenuates CFA-induced arthritis by modulating expression levels of 5-LOX, NF‑κB, IL-17, PGE-2 and TNF-α

Arbutin, a naturally soluble glycosylated phenol has antioxidant, antimicrobial, antitumor and anti-inflammatory properties. The current exploration appraises the treatment of arthritis by use of Arbutin (25, 50 and 100 mg/kg) orally in CFA-induced rat arthritis model. Body weight changes, paw size, and joint diameter were recorded till the 28th day in the arthritic-induced rats. Hematological, biochemical, oxidative and inflammatory biomarkers were measured through the blood samples of anesthetized rats. Arbutin markedly decreased paw volume, PGE-2, anti-CCP and 5-LOX levels, however, maintained metabolic and hematological balance and prevented weight loss. Radiology and histology changes improved significantly in the ankle joints of rats. Moreover, Arbutin increased gene pointers such as IL-10 and IL-4 while significantly reducing the levels of CRP and WBCs, whereas Hb, platelets and RBCs count markedly raised in post-treatments. Antioxidant levels of SOD, CAT and GSH were improved and MDA level was reduced in treated groups. Rt-PCR investigation showed a significant reduction of the interleukin-1β, TNF-α, interleukin-6, cyclooxygenase-2, NF-κB and IL-17 and increased expression of gene pointers like IL-4, and IL-10 in treated groups. Assessment of molecular docking revealed a strong binding interaction of Arbutin against 5-LOX, IL-17, TNF-alpha and interleukin-6, cyclooxygenase-2, nuclear factor-κB, IL-4 and iNOS providing a strong association between experimental and theoretical results. As a result, Arbutin has significantly reduced CFA-induced arthritis by modulation of anti-inflammatory cytokines, i.e., IL-10 and IL-4, the pro-inflammatory cytokines panel such as NF-κB, TNF-alpha, IL-1β, IL-6, PGE-2, 5-LOX and COX-2 and oxidative biomarkers.

Programmed cell death of periodontal ligament cells

The periodontal ligament is a crucial tissue that provides support to the periodontium. Situated between the alveolar bone and the tooth root, it consists primarily of fibroblasts, cementoblasts, osteoblasts, osteoclasts, periodontal ligament stem cells (PDLSCs), and epithelial cell rests of Malassez. Fibroblasts, cementoblasts, osteoblasts, and osteoclasts are functionally differentiated cells, whereas PDLSCs are undifferentiated mesenchymal stem cells. The dynamic development of these cells is intricately linked to periodontal changes and homeostasis. Notably, the regulation of programmed cell death facilitates the clearance of necrotic tissue and plays a pivotal role in immune response. However, it also potentially contributes to the loss of periodontal supporting tissues and root resorption. These findings have significant implications for understanding the occurrence and progression of periodontitis, as well as the mechanisms underlying orthodontic root resorption. Further, the regulation of periodontal ligament cell (PDLC) death is influenced by both systemic and local factors. This comprehensive review focuses on recent studies reporting the mechanisms of PDLC death and related factors.

Jintiange proteins promote osteogenesis and inhibit apoptosis of osteoblasts by enhancing autophagy via PI3K/AKT and ER stress pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Tiger bone, which had long been used in traditional Chinese medicine, had the action of removing wind and alleviating pain, strengthening the sinews and bones, and often used to treat bone impediment, and atrophic debility of bones in TCM clinical practice. As a substitute of natural bone tiger, artificial tiger bone Jintiange (JTG), has been approved by the State Food and Drug Administration of China for relief the symptom of osteoporosis, such as lumbago and back pain, lassitude in loin and legs, flaccidity and weakness legs, and walk with difficulty based on TCM theory. JTG has similar chemical profile to natural tiger bone, and contains mineral substance, peptides and proteins, and has been shown to protect bone loss in ovariectomized mice and exert the regulatory effects on osteoblast and osteoclast activities. But how the peptides and proteins in JTG modulate bone formation remains unclear.

AIM

To investigate the stimulating effects of JTG proteins on osteogenesis and explore the possible underlying mechanisms.

MATERIALS AND METHODS

JTG proteins were prepared from JTG Capsules by extracting calcium, phosphorus and other inorganic elements using SEP-PaktC18 desalting column. MC3T3-E1 cells were treated with JTG proteins to evaluate their effects and explore the underlying mechanisms. Osteoblast proliferation was detected by CCK-8 method. ALP activity was detected using a relevant assay kit, and bone mineralized nodules were stained with alizarin red-Tris-HCl solution. Cell apoptosis was analyzed by flow cytometry. Autophagy was observed by MDC staining, and autophagosomes were observed by TEM. Nuclear translocations of LC3 and CHOP were detected by immunofluorescence and observed under a laser confocal microscope. The expression of key proteins related to osteogenesis, apoptosis, autophagy and PI3K/AKT and ER stress pathways was analyzed by Western Blot analysis.

RESULTS

JTG proteins improved osteogenesis as evidenced by the alteration of proliferation, differentiation and mineralization of MC3T3-E1 osteoblasts, inhibited their apoptosis, and enhanced autophagosome formation and autophagy. They also regulated the expression of key proteins of PI3K/AKT and ER stress pathways. In addition, PI3K/AKT and ER stress pathway inhibitors could reverse the regulatory effects of JTG proteins on osteogenesis, apoptosis, autophagy and PI3K/AKT and ER stress pathways.

CONCLUSION

JTG proteins increased the osteogenesis and inhibited osteoblast apoptosis by enhancing autophagy via PI3K/AKT and ER stress signaling pathways.

Ameliorative effects of Kyung-Ok-Ko and its mixture with Pueraria lobata Ohwi on postmenopausal osteoporosis by promoting phytoestrogenic activity in rats

Introduction

Kyung-Ok-Ko (KOK) is a popular traditional medicine used as a natural alternative to hormone replacement therapy for treating postmenopausal symptoms in Asia. Pueraria lobata Ohwi (P. lobata) is rich in isoflavones and has been traditionally used in combination with other herbs to produce synergistic and pharmaceutical effects via a multi-target approach for disease treatment. We aimed to investigate the phytoestrogenic effects of KOK extract against postmenopausal symptoms in ovariectomized (OVX) rats and confirm its efficacy by mixing KOK and P. lobata extracts.

Methods

OVX rats were daily oral administrated with KOK and KOK + P. lobata mixture extracts (300-400 mg/kg) and their body weight and tail temperature were monitored for 12 weeks. The biochemical parameters, estradiol levels, and bone turnover markers were measured in the serum samples. Moreover, the estrogen receptor, ER-α and ER-β expression in the uterus and the uterus morphology were evaluated. AMPK, ATG1/ULK1, and mTOR protein expression in the liver were assessed.

Results

The 12-week treatment with KOK and KOK + P. lobata mixture extracts did not cause liver damage or hormonal changes in the OVX rats. The treatments reduced the high lipid accumulation-related body weight gain and the tail temperature increase that was induced by ovariectomy. Further, it exhibited protective effects against hyperlipidemia and osteoporosis. No significant difference was observed in uterine weight compared to the OVX-treated group, while endometrial thickness reduction inhibition was observed due to ovariectomy. Bone mineral density (BMD) and serum osteocalcin levels, which decreased in OVX rats, increased with both treatments. Western blotting analysis showed that ER-α and ER-β were not expressed in the treated rats, whereas these proteins were expressed in Sham-operated rats. No significant differences in the phosphorylation of AMPK were observed; however, the ATG1/ULK1 and mTOR protein phosphorylation levels were upregulated and downregulated in the treated rats compared to those of OVX rats, respectively.

Conclusion

This is the first in vivo study observing the efficacy and synergistic effects of the mixture of KOK and P. lobata. Our results suggest the potential of KOK and KOK + P. lobata mixture as an alternative therapy for alleviating menopausal symptoms.

Cell death regulation: A new way for natural products to treat osteoporosis

Osteoporosis is a common metabolic bone disease that results from the imbalance of homeostasis within the bone. Intra-bone homeostasis is dependent on a precise dynamic balance between bone resorption by osteoclasts and bone formation by mesenchymal lineage osteoblasts, which comprises a series of complex and highly standardized steps. Programmed cell death (PCD) (e.g., apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis) is a cell death process that involves a cascade of gene expression events with tight structures. These events play a certain role in regulating bone metabolism by determining the fate of bone cells. Moreover, existing research has suggested that natural products derived from a wide variety of dietary components and medicinal plants modulate the PCDs based on different mechanisms, which show great potential for the prevention and treatment of osteoporosis, thus revealing the emergence of more acceptable complementary and alternative drugs with lower costs, fewer side effects and more long-term application. Accordingly, this review summarizes the common types of PCDs in the field of osteoporosis. Moreover, from the perspective of targeting PCDs, this review also discussed the roles of currently reported natural products in the treatment of osteoporosis and the involved mechanisms. Based on this, this review provides more insights into new molecular mechanisms of osteoporosis and provides a reference for developing more natural anti-osteoporosis drugs in the future.

Casticin promotes osteogenic differentiation of bone marrow stromal cells and improves osteoporosis in rats by regulating nuclear factor-κB/mitogen-activated protein kinase

BACKGROUND

Osteoporosis has influenced millions of people, especially postmenopausal women, which has become a big burden to the whole world. Although the diverse roles of casticin (CAS) on different diseases were identified, whether it was implicated with osteoporosis was unknown.

METHODS

A rat model of osteoporosis was established through dexamethasone (DEX) treatment and a cell model reflecting the osteogenic and osteoclast induction was constructed in bone marrow stromal cells (BMSCs). The calcification at the late stage of induction was measured via Alizarin Red S staining. Western blot was applied to evaluate the levels of proteins.

RESULTS

Hematoxylin and eosin staining revealed that the number of bone trabecular in DEX-induced osteoporosis rats was decreased, while increased doses of CAS treatment elevated the number of bone trabecular. CAS treatment alleviated DEX-induced osteoporosis in rats. Moreover, we found that CAS inhibited the nuclear factor-κB/mitogen-activated protein kinase (NF-κB/MAPK) pathway. In addition, CAS promoted osteogenic differentiation of BMSCs and reduced osteoclastogenesis of bone marrow monocytes. Finally, CAS was observed to retard the receptor activator of NFκ-B ligand-induced NF-κB/MAPK pathway.

CONCLUSION

CAS promoted osteogenic differentiation of BMSCs and improved osteoporosis in rats by regulating the NF-κB/MAPK pathway. This might shed a light into using CAS as a drug treating osteoporosis in the future.

Autophagy: An important target for natural products in the treatment of bone metabolic diseases

Bone homeostasis depends on a precise dynamic balance between bone resorption and bone formation, involving a series of complex and highly regulated steps. Any imbalance in this process can cause disturbances in bone metabolism and lead to the development of many associated bone diseases. Autophagy, one of the fundamental pathways for the degradation and recycling of proteins and organelles, is a fundamental process that regulates cellular and organismal homeostasis. Importantly, basic levels of autophagy are present in all types of bone-associated cells. Due to the cyclic nature of autophagy and the ongoing bone metabolism processes, autophagy is considered a new participant in bone maintenance. Novel therapeutic targets have emerged as a result of new mechanisms, and bone metabolism can be controlled by interfering with autophagy by focusing on certain regulatory molecules in autophagy. In parallel, several studies have reported that various natural products exhibit a good potential to mediate autophagy for the treatment of metabolic bone diseases. Therefore, we briefly described the process of autophagy, emphasizing its function in different cell types involved in bone development and metabolism (including bone marrow mesenchymal stem cells, osteoblasts, osteocytes, chondrocytes, and osteoclasts), and also summarized research advances in natural product-mediated autophagy for the treatment of metabolic bone disease caused by dysfunction of these cells (including osteoporosis, rheumatoid joints, osteoarthritis, fracture nonunion/delayed union). The objective of the study was to identify the function that autophagy serves in metabolic bone disease and the effects, potential, and challenges of natural products for the treatment of these diseases by targeting autophagy.

Counteractions of a Novel Hydroalcoholic Extract from Lens Culinaria against the Dexamethasone-Induced Osteoblast Loss of Native Murine Cells

The cytoprotective effects of a novel hydroalcoholic extract (0.01–5 mg/mL) from Lens culinaria (Terre di Altamura Srl) were investigated within murine native skeletal muscle fibers, bone marrow cells, and osteoblasts, and in cell lines treated with the apoptotic agent staurosporine (2.14 × 10⁻⁶ M), the alkylating drug cisplatin (10⁻⁴ M), the topoisomerase I inhibitor irinotecan (10⁻⁴ M), the antimitotic pro-oxidant doxorubicin (10⁻⁶ M), and the immunosuppressant dexamethasone (2 × 10⁻⁶ M). An amount of 10g of plant material was used to obtain a 70% ethanol/water product, following two-step extraction, evaporation, lyophilization, and storage at −20 °C. For the murine osteoblasts, doxorubicin reduced survival by −65%, dexamethasone by −32% and −60% after 24 and 48 h of incubation time, respectively. The extract was effective in preventing the osteoblast count-reduction induced by dexamethasone; it was also effective at preventing the inhibition of mineralization induced by dexamethasone. Doxorubicin and cisplatin caused a significant reduction in cell growth by −77% for bone marrow cells, −43% for irinotecan, and −60% for dexamethasone, but there was no evidence for the cytoprotective effects of the extract in these cells. Staurosporine and doxorubicin caused a fiber death rate of >−40% after 18 and 24 h of incubation, yet the extract was not effective at preventing these effects. The extract was effective in preventing the staurosporine-induced reduction of HEK293 proliferation and colony formation in the crystal violet DNA staining and the clonogenic assays. It was also effective for the cisplatin-induced reduction in HEK293 cell proliferation. The extract, however, failed to protect the SHSY5Y neurons against cisplatin and irinotecan-induced cytotoxicity. A UV/VIS spectroscopy analysis showed three peaks at the wavelengths of 350, 260, and 190 nm, which correspond to flavonoids, proanthocyanins, salicylates, and AA, constituting the extract. These data suggest the possible development of this extract for use against dexamethasone-induced bone loss and renal chemotherapy-induced damage.

Zuogui Pill Ameliorates Glucocorticoid-Induced Osteoporosis through ZNF702P-Based ceRNA Network: Bioinformatics Analysis and Experimental Validation

Glucocorticoid-induced osteoporosis (GIOP) is a musculoskeletal disease with increased fracture risk caused by long-term application of glucocorticoid, but there exist few effective interventions. Zuogui Pill (ZGP) has achieved clinical improvement for GIOP as an ancient classical formula, but its molecular mechanisms remain unclear due to scanty relevant studies. This study aimed to excavate the effective compounds and underlying mechanism of ZGP in treating GIOP and construct relative ceRNA network by using integrated analysis of bioinformatics analysis and experimental validation. Results show that ZNF702P is significantly upregulated in GIOP than normal cases based on gene chip sequencing analysis. Totally, 102 ingredients and 535 targets of ZGP as well as 480 GIOP-related targets were selected, including 122 common targets and 8 intersection targets with the predicted mRNAs. The ceRNA network contains one lncRNA (ZNF702P), 6 miRNAs, and 8 mRNAs. Four hub targets including JUN, CCND1, MAPK1, and MAPK14 were identified in the PPI network. Six ceRNA interaction axes including ZNF702P-hsa-miR-429-JUN, ZNF702P-hsa-miR-17-5p/hsa-miR-20b-5p-CCND1, ZNF702P-hsa-miR-17-5p/hsa-miR-20b-5p-MAPK1, and ZNF702P-hsa-miR-24-3p-MAPK14 were obtained. By means of molecular docking, we found that all the hub targets could be effectively combined with related ingredients. GO enrichment analysis showed 649 biological processes, involving response to estrogen, response to steroid hormone, inflammatory response, macrophage activation, and osteoclast differentiation, and KEGG analysis revealed 102 entries with 36 relative signaling pathways, which mainly contained IL-17 signaling pathway, T cell receptor signaling pathway, FoxO signaling pathway, the PD-L1 expression and PD-1 checkpoint pathway, MAPK signaling pathway, TNF signaling pathway, Estrogen signaling pathway, and Wnt signaling pathway. Our experiments confirmed that ZNF702P exhibited gradually increasing expression levels during osteoclast differentiation of human peripheral blood monocytes (HPBMs) induced by RANKL, while ZGP could inhibit osteoclast differentiation of HPBMs induced by RANKL in a concentration-dependent manner. Therefore, by regulating inflammatory response, osteoclast differentiation, and hormone metabolism, ZGP may treat GIOP by regulating hub target genes, such as JUN, CCND1, MAPK1, and MAPK14, and acting on numerous key pathways, which involve the ZNF702P-based ceRNA network.

Pyracantha fortuneana (Maxim.) Li: A comprehensive review of its phytochemistry, pharmacological properties, and product development

Pyracantha fortuneana (Maxim.) Li has been used as a herbal medicine in China in its long history. Since ancient times, the fruits of P. fortuneana has been considered a functional food to improve various diseases. Many bioactive substances, including proanthocyanidins, phenols, polysaccharides, and dietary fibers, have been isolated and identified from the P. fortuneana, which possess diverse biological properties both in vitro and in vivo. Although the researches on the P. fortuneana have achieved extensive progress, the systematic study of its biological activities is still relatively lacking. In addition, accumulating researches focus on the landscape value of the P. fortuneana and the development of its by-products. The by-products of P. fortuneana, which show good development potentials in the field of agricultural production and environmental protection, are important for improving the economic value of P. fortuneana and its significance. After extensive reviewing and analyzing the existing published articles, books, and patents, this study aims to a systematic and summarized research trends of P. fortuneana and its phytochemical compositions, nutritional values, pharmacological effects and health benefits of its extracts/monomers, which would be beneficial for the future development of this medicinal plant as functional food or drugs.

Modified Qing' e Pills exerts anti-osteoporosis effects and prevents bone loss by enhancing type H blood vessel formation

OBJECTIVE

To explore whether the modified Qing' e Pills (MQEP) exerts anti-osteoporotic effects and prevents bone loss by enhancing angiogenesis.

METHODS

Network pharmacology was used to assess whether MQEP has a pro-angiogenic capacity and to predict its potential targets. Human umbilical vein endothelial cells were treated with glucocorticoids and MQEP to assess cell viability. The expression of angiotensin II type 1 receptor, angiotensin II type 2 receptor, and angiotensin converting enzyme, which are associated with the activation of the renin-angiotensin-aldosterone system, and the expression of vascular endothelial growth factor and hypoxia-inducible factor 1 alpha, which are associated with the formation of type H blood vessels, were examined by western blot and RT-qPCR. Thereafter, the glucocorticoid-induced osteoporosis model was established and intervened with MQEP. Femur scanning was performed with micro-computed tomography; trabecular spacing, trabecular thickness, and trabecular number were observed and calculated; the expression of nuclear factor-kappa B ligand and osteoprotegerin was detected by ELISA, and the ratio was calculated to evaluate the degree of bone resorption. Finally, type H blood vessels that were highly coupled to osteogenic cells were identified by immunohistochemistry staining and flow cytometry.

RESULTS

This is the first study to reveal and confirm that MQEP could prevent bone loss in glucocorticoid-induced osteoporosis by promoting the expression of hypoxia-inducible factor 1 alpha and vascular endothelial growth factor, which are highly associated with type H blood vessel formation. In vitro experiments confirmed that MQEP could effectively promote the proliferation of vascular endothelial cells and alleviate glucocorticoids-induced activation of the renin-angiotensin-aldosterone system, thereby reducing vascular injury.

CONCLUSION

MQEP exerts anti-osteoporosis effects and prevents bone loss by alleviating vascular injury caused by renin-angiotensin-aldosterone system activation and promoting type H blood vessel formation.

Compressive force-induced LincRNA-p21 inhibits mineralization of cementoblasts by impeding autophagy

The mineralization capability of cementoblasts is the foundation for repairing orthodontic treatment-induced root resorption. It is essential to investigate the regulatory mechanism of mineralization in cementoblasts under mechanical compression to improve orthodontic therapy. Autophagy has a protective role in maintaining cell homeostasis under environmental stress and was reported to be involved in the mineralization process. Long noncoding RNAs are important regulators of biological processes, but their functions in compressed cementoblasts during orthodontic tooth movement remain unclear. In this study, we showed that compressive force downregulated the expression of mineralization-related markers. LincRNA-p21 was strongly enhanced by compressive force. Overexpression of lincRNA-p21 downregulated the expression of mineralization-related markers, while knockdown of lincRNA-p21 reversed the compressive force-induced decrease in mineralization. Furthermore, we found that autophagy was impeded in compressed cementoblasts. Then, overexpression of lincRNA-p21 decreased autophagic activity, while knockdown of lincRNA-p21 reversed the autophagic process decreased by mechanical compression. However, the autophagy inhibitor 3-methyladenine abolished the lincRNA-p21 knockdown-promoted mineralization, and the autophagy activator rapamycin rescued the mineralization inhibited by lincRNA-p21 overexpression. Mechanistically, the direct binding between lincRNA-p21 and FoxO3 blocked the expression of autophagy-related genes. In a mouse orthodontic tooth movement model, knockdown of lincRNA-p21 rescued the impeded autophagic process in cementoblasts, enhanced cementogenesis, and alleviated orthodontic force-induced root resorption. Overall, compressive force-induced lincRNA-p21 inhibits the mineralization capability of cementoblasts by impeding the autophagic process.