miR-122-5p Mediates Fluoride-Induced Osteoblast Activation by Targeting CDK4

Ellagic acid inhibits CDK12 to increase osteoblast differentiation and alleviate osteoporosis in hindlimb-unloaded and ovariectomized mice

BACKGROUND

Osteoporosis is a highly prevalent bone disease occurred commonly in astronauts and postmenopausal women due to mechanical unloading and estrogen deficiency, respectively. At present, there are some traditional Chinese medicine compounds for preventing and treating osteoporosis induced by simulated microgravity, but the detailed components of the traditional Chinese medicines still need to be confirmed and osteoporosis is still untreatable due to a lack of effective small-molecule natural medicine.

PURPOSE

To explore the role of cyclin-dependent kinase 12 (CDK12) in osteoporosis induced by simulated microgravity and the therapeutic effect of CDK12-targeted Ellagic Acid (EA) on osteoporosis.

METHODS

Our previous study has suggested that CDK12 as a potential target for treating and preventing osteoporosis. In this study, the role of CDK12 in osteoblasts and mice bone tissues was further studied under simulated microgravity. And by targeting CDK12, natural small-molecule product EA was screened out based on a large scale through the weighted set similarity (WES) method and the therapeutic effects of EA on osteoporosis was investigated in hindlimb-unloaded (HU) mouse model and ovariectomized (OVX) model.

RESULTS

The results demonstrated that simulated microgravity inhibited bone formation and up-regulated the expression of CDK12. Furthermore, CDK12-siRNA or THZ531 (an inhibitor of CDK 12) promoted osteoblast differentiation, while the overexpression of CDK12 inhibited osteoblasts differentiation. And we further proved that CDK12-targeted EA showed a rescue effect on osteoblast differentiation inhibition caused by simulated microgravity. EA (50 mg·kg^-1·day^-1) daily intragastric administration alleviated the symptoms of osteoporosis and accompanied with the improvement of trabecular bone and cortical bone parameters with significantly overexpression of CDK12.

CONCLUSION

EA efficiently improves osteoporosis by targeting CDK12, which is a suppresser of osteoblast differentiation and a novel therapeutic target for treating osteoporosis.

Biphasic Functions of Sodium Fluoride (NaF) in Soft and in Hard Periodontal Tissues

Sodium fluoride (NaF) is widely used in clinical dentistry. However, the administration of high or low concentrations of NaF has various functions in different tissues. Understanding the mechanisms of the different effects of NaF will help to optimize its use in clinical applications. Studies of NaF and epithelial cells, osteoblasts, osteoclasts, and periodontal cells have suggested the significant roles of fluoride treatment. In this review, we summarize recent studies on the biphasic functions of NaF that are related to both soft and hard periodontal tissues, multiple diseases, and clinical dentistry.

Exosomal miR-122-5p is Related to the Degree of Myelosuppression Caused by Chemotherapy in Patients with Colorectal Cancer

Purpose

As rapidly dividing cells are usually the target of anticancer chemotherapy, it is inevitable that rapidly dividing normal cells become damaged, with myelosuppressive effects being a serious side effect of this therapy. Many recent studies have found that exosomal microRNAs (miRNAs) are related to the occurrence of some diseases.

Patients and Methods

Small RNA sequencing was used to investigate differential exosomal miRNAs with the same expression trend between groups after chemotherapy: MildA (before chemotherapy in patients with mild myelosuppression) and MildB (after chemotherapy in patients with mild myelosuppression); SevereA (before chemotherapy in patients with severe myelosuppression) and SevereB (after chemotherapy in patients with severe myelosuppression). A Venn diagram was generated to screen exosomal miRNAs related to chemotherapy. Small RNA sequencing was also used to investigate differentially expressed exosomal miRNAs among these groups, and exosomal miRNAs related to myelosuppression after chemotherapy was explored using a Venn diagram. RT-qPCR was applied to further verify the sequencing results. We performed target gene prediction and functional analysis for candidate exosomal miRNAs.

Results

Compared with that in the MildA or SevereA group, an increase in exosomal miR-122-5p was found in the MildB or SevereB group, and the expression level was lower in the SevereB group than in the MildB group. However, we found no notable difference in its expression level between the MildA and SevereA groups. Similar results were not obtained for the remaining miRNAs. RT-qPCR confirmed the screening results. Further analyses indicated that exosomal miR-122-5p targets CDK4 to inhibit the cell cycle.

Conclusion

The expression level of exosomal miR-122-5p in the serum of patients with colorectal cancer correlates with the severity of myelosuppression caused by chemotherapy, and miR-122-5p targets CDK4 to inhibit cell cycle progression.

miR-486-3p regulates CyclinD1 and promotes fluoride-induced osteoblast proliferation and activation

Fluoride is a persistent environmental pollutant, and its excessive intake contributes to skeletal and dental fluorosis. The mechanisms underlying fluoride-induced abnormal osteoblast proliferation and activation, which are related to skeletal fluorosis, have not yet been fully clarified. As important epigenetic regulators, microRNAs (miRNAs) participate in bone metabolism. On the basis of our previous miRNA-seq results and bioinformatics analysis, this study investigated the role and specific molecular mechanism of miR-486-3p in fluoride-induced osteoblast proliferation and activation via CyclinD1. Herein, in the fluoride-challenged population, we observed that miR-486-3p expression decreased while CyclinD1 and transforming growth factor (TGF)-β1 increased, and miR-486-3p level correlated negatively with the expression of CyclinD1 and TGF-β1 genes. Further, we verified that sodium fluoride (NaF) decreases miR-486-3p expression in human osteoblasts and overexpression of miR-486-3p reduces fluoride-induced osteoblast proliferation and activation. Meanwhile, we demonstrated that miR-486-3p regulates NaF-induced upregulation of CyclinD1 by directly targeting its 3'-untranslated region (3'-UTR). In addition, we observed that NaF activates the TGF-β1/Smad2/3/CyclinD1 axis and miR-486-3p mediates transcriptional regulation of CyclinD1 by TGF-β1/Smad2/3 signaling pathway via targeting TGF-β1 3'-UTR in vitro. This study, thus, contributes significantly in revealing the mechanism of miR-486-3p-mediated CyclinD1 upregulation in skeletal fluorosis and sheds new light on endemic fluorosis treatment.