CircRFWD2 Promotes Osteogenic Differentiation of human Dental Pulp Stem Cells by Targeting miR-6817-5p Through BMP-Smad and p38 MAPK Pathway

Regulation of TGF-β/BMP signaling during osteoblast development by non-coding RNAs: Potential therapeutic applications

Bone is a connective tissue that is metabolically active and serves multiple functions, including movement, structural support, and organ protection. It is comprised primarily of three types of bone cells, namely osteoblasts, osteocytes, and osteoclasts. Osteoblasts are bone-forming cells, and the differentiation of mesenchymal stem cells towards osteoblasts is regulated by several growth factors, cytokines, and hormones via various signaling pathways, including TGF-β/BMP (transforming growth factor-beta/bone morphogenetic protein) signaling as a primary one. Non-coding RNAs (ncRNAs), such as microRNAs and long ncRNAs, play crucial roles in regulating osteoblast differentiation via the TGF-β/BMP signaling cascade. Dysregulation of these ncRNAs leads to bone-pathological conditions such as osteoporosis, skeletal dysplasia, and osteosclerosis. This review provides a concise overview of the latest advancements in understanding the involvement of ncRNAs/TGF-β/BMP axis in osteoblast differentiation. These findings have the potential to identify new molecular targets for early detection of bone metabolism disorders and the development of innovative therapy strategies.

Potential of Dental Pulp Stem Cell Exosomes: Unveiling miRNA-Driven Regenerative Mechanisms

Human dental pulp stem cells (hDPSCs) have emerged as a promising resource in regenerative medicine due to their unique ability to secrete exosomes containing a diverse array of bioactive molecules, particularly microRNAs (miRNAs). These exosomes appear to be essential for stimulating regenerative mechanisms, especially those associated with stem cell pluripotency and tissue repair. However, several challenges such as cargo specificity and delivery efficiency need to be addressed to maximise the therapeutic potential of hDPSC-derived exosomes and miRNA-based therapies. This narrative review explores hDPSCs' potential in regenerative medicine by examining their role in tissue engineering, secretome composition, exosome function, exosomal miRNA in diverse models, and miRNA profiling. Therefore, it is imperative to sustain ongoing research on miRNA to advance clinical applications in the field of regenerative medicine and dentistry. A comprehensive understanding of the specific miRNA composition within hDPSC-derived exosomes is essential to elucidate their mechanistic roles in diverse disease states and to inform the development of innovative therapeutic strategies. These findings hold significant potential for the development of innovative regenerative therapies and emphasises the importance of establishing a strong connection between translational research discoveries and clinical applications. hDPSC-derived exosomes and miRNA-based therapies play a crucial role in immune modulation, regenerative dentistry, and tissue repair.

Dental pulp stem cells - A basic research and future application in regenerative medicine

Dental pulp is a valuable and accessible source of stem cells (DPSCs) with characteristics similar to mesenchymal stem cells. DPSCs can regenerate a range of tissues and their potential for clinical application in regenerative medicine is promising. DPSCs have been found to express low levels of Class II HLA-DR (MHC) molecules, making them potential candidates for allogeneic transplantation without matching the donor's tissue. Research on the correlation between non-coding RNAs (ncRNAs) and human dental pulp stem cells (DPSCs) provides promising insights into the use of these cells in clinical settings for a wide range of medical conditions. It is possible to use a number of ncRNAs in order to restore the functional role of downregulated ncRNAs that are correlated with osteoblastogenesis, or to suppress the functional role of overexpressed ncRNAs associated with osteoclast differentiation in some cases.

A novel approach in biomedical engineering: The use of polyvinyl alcohol hydrogel encapsulating human umbilical cord mesenchymal stem cell-derived exosomes for enhanced osteogenic differentiation and angiogenesis in bone regeneration

Developing effective methods for alveolar bone defect regeneration is a significant challenge in orthopedics. Exosomes from human umbilical cord mesenchymal stem cells (HUMSC-Exos) have shown potential in bone repair but face limitations due to undefined application methods and mechanisms. To address this, HUMSC-Exos were encapsulated in polyvinyl alcohol (PVA) hydrogel (Exo@PVA) to create a novel material for alveolar bone repair. This combination enhanced the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) more effectively than Exos alone. Additionally, Exo@PVA significantly improved alveolar bone regeneration and defect repair in rats. The microRNA-21-5p (miR-21-5p) in Exo@PVA, identified through the GEO database and analyzed via in silico methods, played a crucial role. miR-21-5p promoted BMSC osteogenic differentiation by inhibiting WWP1-mediated KLF5 ubiquitination and enhanced HUVEC angiogenesis by targeting ATP2B4. These findings underscore the potential of an Exo-based approach with PVA hydrogel scaffolds for bone defect repair, operating through the miR-21-5p/WWP1/ATP2B4 signaling axis.

Circ-ZNF236 mediates stem cells from apical papilla differentiation by regulating LGR4-induced autophagy

AIM

Human stem cells from the apical papilla (SCAPs) are an appealing stem cell source for tissue regeneration engineering. Circular RNAs (circRNAs) are known to exert pivotal regulatory functions in various cell differentiation processes, including osteogenesis of mesenchymal stem cells. However, few studies have shown the potential mechanism of circRNAs in the odonto/osteogenic differentiation of SCAPs. Herein, we identified a novel circRNA, circ-ZNF236 (hsa_circ_0000857) and found that it was remarkably upregulated during the SCAPs committed differentiation. Thus, in this study, we showed the significance of circ-ZNF236 in the odonto/osteogenic differentiation of SCAPs and its underlying regulatory mechanisms.

METHODOLOGY

The circular structure of circ-ZNF236 was identified via Sanger sequencing, amplification of convergent and divergent primers. The proliferation of SCAPs was detected by CCK-8, flow cytometry analysis and EdU incorporation assay. Western blotting, qRT-PCR, Alkaline phosphatase (ALP) and Alizarin red staining (ARS) were performed to explore the regulatory effect of circ-ZNF236/miR-218-5p/LGR4 axis in the odonto/osteogenic differentiation of SCAPs in vitro. Fluorescence in situ hybridization, as well as dual-luciferase reporting assays, revealed that circ-ZNF236 binds to miR-218-5p. Transmission electron microscopy (TEM) and mRFP-GFP-LC3 lentivirus were performed to detect the activation of autophagy.

RESULTS

Circ-ZNF236 was identified as a highly stable circRNA with a covalent closed loop structure. Circ-ZNF236 had no detectable influence on cell proliferation but positively regulated SCAPs odonto/osteogenic differentiation. Furthermore, circ-ZNF236 was confirmed as a sponge of miR-218-5p in SCAPs, while miR-218-5p targets LGR4 mRNA at its 3'-UTR. Subsequent rescue experiments revealed that circ-ZNF236 regulates odonto/osteogenic differentiation by miR-218-5p/LGR4 in SCAPs. Importantly, circ-ZNF236 activated autophagy, and the activation of autophagy strengthened the committed differentiation capability of SCAPs. Subsequently, in vivo experiments showed that SCAPs overexpressing circ-ZNF236 promoted bone formation in a rat skull defect model.

CONCLUSIONS

Circ-ZNF236 could activate autophagy through increasing LGR4 expression, thus positively regulating SCAPs odonto/osteogenic differentiation. Our findings suggested that circ-ZNF236 might represent a novel therapeutic target to prompt the odonto/osteogenic differentiation of SCAPs.

Roles of circular RNAs in osteogenic/osteoclastogenic differentiation

The process of bone remodeling occurs and is regulated through interactions between osteoclasts, which resorb bone, and osteoblasts, which generate bone tissue. When the homeostatic balance between these two cell types is dysregulated, this can contribute to abnormal bone remodeling resulting in a loss of bone mass as is observed in osteoporosis (OP) and other forms of degenerative bone metabolic diseases. At present, details of molecular mechanism underlying the development of bone metabolic diseases such as OP remain to be elucidated. Circular RNAs (circRNAs) are small non-coding RNA molecules with a closed-loop structure that can regulate the differentiation of osteoclasts and osteoblasts. The present review provides a systematic overview of recent literature on the processes through which circRNAs regulate the dynamic balance between osteoblasts and osteoclasts that ultimately preserve bone homeostasis. It will also give insight that can shape current understanding of the pathogenesis of OP and other bone metabolic diseases to better guide diagnostic and treatment strategies for affected patients.

miR-20a-5p regulated SMAD6 to inhibit chondrogenesis of hDPSCs

OBJECTIVES

Chondrogenic differentiation of human dental pulp stem cells (hDPSCs) is highly promising for cartilage repair. The specific mechanism, however, still needs to be explicated.

MATERIALS AND METHODS

In this study, we isolated hDPSCs and transfected cells with lentiviruses containing an over-expression, knock-down, or negative control of miR-20a-5p. Three-D pellet cultures of hDPSCs were used for the chondrogenic induction. Following the pellet culture period, chondrogenesis was assessed by histological and immunohistochemical analysis and expression of chondrogenic-related genes. Dual-luciferase report assay was performed to determine potential targeted genes of miR-20a-5p, and the phosphorylation levels of P65 and IκBα were explored. Animal experiments were performed to determine the effect of miR-20a-5p on cartilage regeneration.

RESULTS

miR-20a-5p was showed to repress the expression of SMAD6 to inhibit the chondrogenic differentiation of hDPSCs. Accordingly, the knock-down of miR-20a-5p promoted cartilage regeneration in the osteochondral defects of rats. Mechanically, it is indicated that NF-κB signaling is the potential down-stream network of miR-20a-5p/Smad6 crosstalk during chondrogenic differentiation.

CONCLUSIONS

miR-20a-5p could target SMAD6 to activate NF-κB signaling pathway, and thus inhibit chondrogenesis of hDPSCs, which provided promising therapeutic target for cartilage defects clinically.

Icariin promotes osteogenic differentiation through the mmu_circ_0000349/mmu-miR-138-5p/Jumonji domain-containing protein-3 axis

Circular RNAs (circRNAs) regulate Jumonji domain-containing protein-3 (JMJD3) by sponging with microRNAs (miRNAs). This study aimed to investigate the role of icariin on specific circRNA/miRNA/JMJD3 axis in osteogenic differentiation of MC3T3-E1 cells. CircRNA sequencing was performed on the MC3T3-E1 cells induced by osteogenic differentiation medium for 1 d (negative control (NC) group) and 14 d (osteogenesis group). And mmu_circ_0000349 was verified using Sanger sequencing, ribonuclease R degradation, and actinomycin D assay. The function of mmu_circ_0000349 was validated by detecting the expressions of osteogenic differentiation markers, alkaline phosphatase (ALP), and runt-related transcription (RUNX2), via real-time quantitative PCR (qPCR) and Western blotting or ALP and alizarin red staining assay. Dual luciferase reporter gene assay confirmed the relationship between mmu_circ_0000349 and mmu-miR-138-5p (or mmu-miR-138-5p and JMJD3). Meanwhile, the JMJD3 binding to mmu_circ_0000349 was screened using an RNA pull-down assay. qPCR and Western blotting confirmed the effect of icariin on the mmu_circ_0000349/mmu-miR-138-5p/JMJD3 axis and osteogenic differentiation. As MC3T3-E1 osteogenic differentiation progressed, the JMJD3 expression level increased. A total of 361 circRNAs exhibited differences between the NC and osteogenesis groups. After validation, mmu_circ_0000349 was further analyzed as it exhibited the largest expression. And mmu_circ_0000349 was identified as a stable circular structure. Overexpression of mmu_circ_0000349 increased the expression levels of ALP and RUNX2, enhanced ALP activity, and increased the number of mineralized nodules; contrarily, inhibition of mmu_circ_0000349 exerted opposite effects. The data also confirmed that mmu_circ_0000349 regulated JMJD3 by sponging with mmu-miR-138-5p. With the increase in icariin concentration and time for treatment, the expression levels of mmu_circ_0000349, JMJD3, ALP, and RUNX2 also increased, whereas that of mmu-miR-138-5p decreased. In conclusion, Icariin promoted osteogenic differentiation by regulating the mmu_circ_0000349/mmu-miR-138-5p/JMJD3 pathway. Therefore, this provides a theoretical basis for the treatment of diseases related to osteogenic differentiation.

Functional role of circRNAs in osteogenesis: A review

The extracellular matrixes (ECM), as well as the microenvironmental signals, play an essential role in osteogenesis by regulating intercellular pathways. Recently, it has been demonstrated that a newly identified RNA, circular RNA, contributes to the osteogenesis process. Circular RNA (circRNA), the most recently identified RNA, is involved in the regulation of gene expression at transcription to translation levels. The dysregulation of circRNAs has been observed in several tumors and diseases. Also, various studies have shown that circRNAs expression is changed during osteogenic differentiation of progenitor cells. Therefore, understanding the role of circRNAs in osteogenesis might help the diagnosis as well as treatment of bone diseases such as bone defects and osteoporosis. In this review, circRNA functions and the related pathways in osteogenesis have been discussed.

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

Hsa_circ_0001485 promoted osteogenic differentiation by targeting BMPR2 to activate the TGFβ-BMP pathway

Background

Circular RNAs (circRNAs) are a new type of stable noncoding RNA and have been proven to play a crucial role in osteoporosis. This study explored the role and mechanism of hsa_circ_0001485 in osteogenic differentiation.

Methods

Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and Gene Ontology (GO) enrichment analysis were performed according to the previous sequencing data in human bone marrow mesenchymal stem cells (BMSC) before and after the induction of osteogenic differentiation on the differentially expressed circRNAs, to screen out signaling pathways associated with osteogenic differentiation. The hFOB 1.19 cells were used to verify the function and mechanism of specific circRNAs in osteogenic differentiation. Additionally, small interfering fragments and overexpression plasmids were used to determine the role of specific circRNAs during osteogenic differentiation. Furthermore, pull-down experiments and mass spectrometry were performed to determine the proteins that bind to specific circRNAs.

Results

The KEGG and GO enrichment analyses showed that the TGFβ-BMP signaling pathway was related to the osteogenic differentiation process, and four circRNAs were associated with the pathway. The quantitative polymerase chain reaction analysis revealed that hsa_circ_0001485 expression was increased during the osteogenic differentiation process of BMSCs. Knockdown of hsa_circ_0001485 suppressed the activity of the alkaline phosphatase enzyme and the expression of RUNX2, osteopontin, and osteocalcin in the osteogenic hFOB 1.19 cells, whereas overexpression of hsa_circ_0001485 promoted their expression. Additionally, we found that hsa_circ_0001485 and BMPR2 targeted binding to activate the TGFβ-BMP signaling pathway and promoted osteogenic differentiation through mass spectrometry analysis.

Conclusion

This study demonstrates that hsa_circ_0001485 is highly expressed in the osteogenic hFOB 1.19 cells, which activate the TGFβ-BMP pathway through targeted binding of BMPR2, and plays a positive role in regulating osteogenic differentiation.