Isolation and Culture of Neonatal Mouse Calvarial Osteoblasts

Osteoblasts-Derived Exosomal lncRNA-MALAT1 Promotes Osteoclastogenesis by Targeting the miR-124/NFATc1 Signaling Axis in Bone Marrow-Derived Macrophages

Objective

Emerging studies have explained the crucial role of non-coding RNA (lncRNA) in various pathological progressions. The study was designed to examine the role of lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and miRNA-124 in the differentiation of osteoclasts, to provide new clues or evidences for the pathogenesis of periodontitis.

Methods

We constructed an osteoblast-osteoclast Transwell co-culture system and osteoblast-derived exosomes (OB-exo) intervention model. We assessed the osteoclastogenesis as well as the level of lncRNA-MALAT1 and miRNA-124. The mechanism for lncRNA MALAT1 targeting miR-124 modulating the differentiation of osteoclasts was investigated by cell transfection, quantitative real-time reverse transcription PCR (RT-qPCR), Western blot, and Dual-Luciferase reporter assays.

Results

Osteoblast-derived exosomes were isolated and identified. Co-culture and OB-exo intervention can promote osteoclastogenesis, also significantly up-regulate the expression of MALAT1, while the level of miR-124 is the opposite. Transfection of cells with small interfering RNA (si-MALAT1) and miR-124 mimic decreased the formation of TRAP⁺ osteoclasts and inhibited the expression of NFATc1. However, the effect was reversed when transfected with miR-124 inhibitor and si-MALAT1. The Dual-Luciferase reporter assay confirmed the binding sites between MALAT1 and miR-124, and miR-124 and NFATc1.

Conclusion

LncRNA MALAT1 functioned as an endogenous sponge by competing for miR-124 binding to regulate NFATc1 expression, accelerating the progression of osteoclastogenesis.

A Comparison of the Antiosteoporotic Effects of Cornelian Cherry (Cornus mas L.) Extracts from Red and Yellow Fruits Containing Different Constituents of Polyphenols and Iridoids in Osteoblasts and Osteoclasts

Methods

Polyphenolic and iridoid constituents of extracts were analyzed qualitatively and quantitatively using the ultraperformance liquid chromatography system coupled with a quadrupole-time of flight mass spectrometry. Primary cultured osteoblasts isolated from mouse calvarias and osteoclast-lineage primary cultured monocytes isolated from mouse bone marrow were used for the assessment of osteoblast and osteoclast differentiation. In the osteoblast culture, cellular viability, alkaline phosphatase (ALP) activity, ALP staining, and mRNA expression of Alpl and Runx2 were examined. In the osteoclast culture, the examined parameters were cellular viability, tartrate-resistant acid phosphatase (TRAP) activity and staining, and mRNA expression of Nfatc1, Ctsk, and Acp.

Results

A total of 41 main compounds of iridoids, anthocyanins, hydrolysable tannins, phenolic acids, and flavonols were identified in the three extracts. RED EXT1 contained most of the tested polyphenols and iridoids and was the only extract containing anthocyanins. YL EXT2 contained only one iridoid, loganic acid and gallic acid. YL EXT3 comprised a mixture of iridoids and polyphenols. RED EXT1, YL EXT 2, and to a lesser extent YL EXT3 promoted osteoblast differentiation increasing significantly ALP activity and the amount of ALP-positive stained cells. All extracts upregulated mRNA expression of Alpl and Runx2. RED EXT1 caused the most significant decrease in TRAP activity and the numbers of TRAP-positive multinucleated cells. RED EXT1 caused also the most significant downregulation of mRNA expression of osteoclast related genes Nfatc1, Ctsk, and Acp5. Extracts from yellow fruits, mostly YL EXT2 caused lower, but still significant inhibitory effect on TRAP and osteoclast related genes.

Conclusions

The main conclusion of our study is that all three extracts, especially RED EXT1 from red cornelian cherry fruits, possess the antiosteoporotic potential and may be a promising phytomedicine candidate for the prevention and treatment of osteoporosis.

Stromal Co-Cultivation for Modeling Breast Cancer Dormancy in the Bone Marrow

Cancers metastasize to the bone marrow before primary tumors can be detected. Bone marrow micrometastases are resistant to therapy, and while they are able to remain dormant for decades, they recur steadily and result in incurable metastatic disease. The bone marrow microenvironment maintains the dormancy and chemoresistance of micrometastases through interactions with multiple cell types and through structural and soluble factors. Modeling dormancy in vitro can identify the mechanisms of these interactions. Modeling also identifies mechanisms able to disrupt these interactions or define novel interactions that promote the reawakening of dormant cells. The in vitro modeling of the interactions of cancer cells with various bone marrow elements can generate hypotheses on the mechanisms that control dormancy, treatment resistance and reawakening in vivo. These hypotheses can guide in vivo murine experiments that have high probabilities of succeeding in order to verify in vitro findings while minimizing the use of animals in experiments. This review outlines the existing data on predominant stromal cell types and their use in 2D co-cultures with cancer cells.

Inhibitory Effect of Ulmus davidiana and Cornus officinalis Extracts on Osteoporotic Bone Loss In Vitro and In Vivo

Background and Objectives: Traditional herbal medicines are becoming more popular as a complementary medication as they have the advantages of being mostly harmless and safe, causing fewer side-effects than conventional medications. Here, we demonstrate the inhibitory effects of the combination of Ulmus davidiana (UD) and Cornus officinalis (CO) extracts on osteoporotic bone loss. Materials and Methods: This study presented osteogenic effects in primary cultured osteoblasts, pre-osteoblastic MC3T3-E1 cell lines, and osteoclastogenic effects in osteoclasts derived from bone marrow monocytes, and finally, protective effects on bone loss in an ovariectomy (OVX)-induced osteoporotic animal model. Results: A significant increase in alkaline phosphatase (ALP) activity was observed following treatment with UD and CO mixtures (8:2, 7:3, and 5:5 ratios) and individual UD and CO extracts, with the highest ALP activity being detected for the treatment with UD and CO extracts at a 5:5 ratio. An optimal ratio of UD and CO (UC) extract promoted osteoblast differentiation in both pre-osteoblastic cells and primary osteoblasts by increasing osteoblastic markers such as Alpl, Runx2, and Bglap. However, treatment with the UC extract inhibited osteoclast differentiation with a decreased expression of osteoclastogenesis-related genes, including Ctsk, Acp5, Mmp9, and Nfatc1. In addition, UC treatment prevented osteoporotic bone loss in OVX mice and improved impaired skeletal structure parameters. Conclusions: This study suggests that combined UD and CO extracts may be a beneficial traditional medicine for the prevention of postmenopausal osteoporosis.

Interleukin-17 promotes osteoclastogenesis and periodontal damage via autophagy in vitro and in vivo

OBJECTIVE

Because of its potent pro-inflammatory properties, interleukin-17 (IL-17) contributes to the pathogenesis of various inflammatory diseases. This study explored the effects of IL-17 on osteoclastogenesis in an osteoclast monoculture and osteoblast-osteoclast co-culture system, as tools to investigate the molecular mechanisms underlying the interactions between osteoclastogenesis and autophagy.

METHODS

Various ratios of calvarial osteoblasts (OB) and osteoclast precursor cells (mouse macrophage cell line RAW264.7, hereinafter referred to as OC) were tested. Tartrate-resistant acid phosphatase (TRAP) staining was used to detect the optimum osteoblasts:osteoclasts ratio. IL-17 was added to the co-culture system to test its effects on multinucleated osteoclast formation and osteoclast-related proteins. We assessed the effects of IL-17 on receptor activator of nuclear factor-kappa B ligand (RANKL) expression in osteoblasts, and determined if IL-17 alone could modulate osteoclast formation in an osteoclast monoculture. Administration of exogenous RANKL combined with IL-17 was employed to stimulate RAW264.7 cells osteoclastogenesis and to determine production of osteoclasts and autophagy-related proteins. We knocked down Beclin1 expression in RAW264.7 cells and examined the expression of autophagy-related and osteoclast-related proteins in RAW264.7 cells and the co-culture system, and the TAK1-binding protein 3 (TAB3)/ extracellular signal regulated kinase (ERK) pathway.

RESULTS

A ratio of 20 OB : 1 OC yielded the highest rate of osteoclast formation. Low IL-17 concentrations increased osteoclastogenesis in co-cultures significantly, but high levels of IL-17 had the opposite effect. IL-17 alone could not induce formation of TRAP⁺ multinucleated cells in RAW264.7 cells. Low IL-17 concentrations promoted osteoclast differentiation and autophagy in RAW264.7 cells induced by exogenous RANKL, but high IL-17 concentrations inhibited this process. Knockdown of Beclin1 reversed the enhanced effects of 0.1 ng/mL IL-17 on osteoclastogenesis and autophagy in RAW264.7 cells. The TAB3/ERK pathway was also blocked after autophagy inhibition.

CONCLUSION

In the co-culture model used in this study, a ratio of 20 OB:1 OC proved to be the optimal ratio to facilitate osteoclast formation. IL-17 regulated RANKL-induced osteoclastogenesis via autophagy. The Beclin1/TAB3/ERK pathway was involved in osteoclast autophagy.

Evaluation of MC3T3-E1 Cell Osteogenesis in Different Cell Culture Media

Many biomaterials have been evaluated using cultured cells. In particular, osteoblast-like cells are often used to evaluate the osteocompatibility, hard-tissue-regeneration, osteoconductive, and osteoinductive characteristics of biomaterials. However, the evaluation of biomaterial osteogenesis-inducing capacity using osteoblast-like cells is not standardized; instead, it is performed under laboratory-specific culture conditions with different culture media. However, the effect of different media conditions on bone formation has not been investigated. Here, we aimed to evaluate the osteogenesis of MC3T3-E1 cells, one of the most commonly used osteoblast-like cell lines for osteogenesis evaluation, and assayed cell proliferation, alkaline phosphatase activity, expression of osteoblast markers, and calcification under varying culture media conditions. Furthermore, the various media conditions were tested in uncoated plates and plates coated with collagen type I and poly-L-lysine, highly biocompatible molecules commonly used as pseudobiomaterials. We found that the type of base medium, the presence or absence of vitamin C, and the freshness of the medium may affect biomaterial regeneration. We posit that an in vitro model that recapitulates in vivo bone formation should be established before evaluating biomaterials.

Interleukin-17 induces pyroptosis in osteoblasts through the NLRP3 inflammasome pathway in vitro

OBJECTIVE

Interleukin-17 (lL-17), a pro-inflammatory cytokine produced by Th17 cells, is also considered to play an important role in bone metabolism, but the exact mechanism of bone destruction remains unclear. In this study, we explored whether IL-17 could induce osteoblasts pyroptosis in vitro.

METHODS

The murine primary osteoblasts were isolated from the calvarial bones of mice. The proliferation of osteoblasts was evaluated by cell counting kit-8 (CCK-8) assay. The mRNA levels of NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis associated speck like protein containing a card (ASC), caspase-1, gasdermin-D (GSDMD), IL-1β and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured by real-time quantitative PCR. Pyroptosis after IL-17 treatment was evaluated by lactate dehydrogenase (LDH) Release Assay Kit and the morphological characteristics of osteoblasts were observed via Scanning Electron Microscopy (SEM). Pyroptosis associated proteins, cleaved IL-1β and RANKL were evaluated through western blot. The release of IL-1β and RANKL was measured by ELISA. In addition, calcium nodule was tested by alizarin red staining.

RESULTS

High concentration IL-17 (100 ng/mL) could affect the proliferation of osteoblasts, promote the gene expression of NLRP3, caspase-1, GSDMD, IL-1β and RANKL. In contrast to control group, osteoblasts treated with IL-17 had the appearance of numerous pores, swelling and rupture. Also, the release of LDH, IL-1β and RANKL increased in the presence of IL-17. However, inhibition of NLRP3 prevented activation of the NLRP3 inflammasome, thereby restoring osteoblasts morphology and function.

CONCLUSION

IL-17 induced osteoblasts pyroptosis, and the pyroptosis of osteoblasts may prompt the release of IL-1β and RANKL,which may further contribute to disruption of bone metabolism. Besides, the NLRP3 inflammasome pathway was involved in the pyroptosis of osteoblasts.