Nkd2 promotes the differentiation of dental follicle stem/progenitor cells into osteoblasts

Naked cuticle homolog 2 controls the differentiation of osteoblasts and osteoclasts and ameliorates bone loss in ovariectomized mice

Naked cuticle homolog 2 (NKD2) has been recognized as an antagonist of Wnt/β-catenin signaling and a tumor suppressor. The role of NKD2 in osteoblast and osteoclast differentiation and the mechanism are not fully understood. In this study, we identified the up-regulation of NKD2 during osteoblast and adipocyte differentiation. Functional experiments revealed that NKD2 stimulated osteoblast differentiation and suppressed adipocyte formation. Furthermore, NKD2 down-regulated the expression of receptor activator of nuclear factor-κB ligand in bone marrow mesenchymal stem cells and inhibited osteoclast formation from osteoclast precursor cells. Mechanistic investigations revealed that the regulation of osteoblast and adipocyte differentiation by NKD2 involved Wnt/β-catenin and tuberous sclerosis complex subunit 1 (TSC1)/mechanistic target of rapamycin complex 1 (mTORC1) signaling pathways. Unlike in undifferentiated mesenchymal cells where NKD2 promoted Dishevelled-1 degradation, in the cells differentiating toward osteoblasts or adipocytes NKD2 down-regulated secreted frizzled related protein 1/4 expression and failed to destabilize Dishevelled-1, thereby activating Wnt/β-catenin signaling. Moreover, NKD2 bound to TSC1 and inhibited mTORC1 signaling. Further investigation uncovered an interplay between TSC1/mTORC1 and Wnt/β-catenin signaling pathways. Finally, transplantation of NKD2-overexpressing bone marrow mesenchymal stem cells into the marrow of mice increased osteoblasts, reduced osteoclasts and marrow fat, and partially prevented bone loss in ovariectomized mice. This study provides evidence that NKD2 in mesenchymal stem/progenitor cells reciprocally regulates the differentiation of osteoblasts and adipocytes by modulating Wnt/β-catenin and mTORC1 pathways and inhibits osteoclast formation by down-regulating receptor activator of nuclear factor-κB ligand. It suggests that NKD2 up-regulation may ameliorate postmenopausal bone loss.

Spatiotemporal cellular dynamics and molecular regulation of tooth root ontogeny

Tooth root development involves intricate spatiotemporal cellular dynamics and molecular regulation. The initiation of Hertwig's epithelial root sheath (HERS) induces odontoblast differentiation and the subsequent radicular dentin deposition. Precisely controlled signaling pathways modulate the behaviors of HERS and the fates of dental mesenchymal stem cells (DMSCs). Disruptions in these pathways lead to defects in root development, such as shortened roots and furcation abnormalities. Advances in dental stem cells, biomaterials, and bioprinting show immense promise for bioengineered tooth root regeneration. However, replicating the developmental intricacies of odontogenesis has not been resolved in clinical treatment and remains a major challenge in this field. Ongoing research focusing on the mechanisms of root development, advanced biomaterials, and manufacturing techniques will enable next-generation biological root regeneration that restores the physiological structure and function of the tooth root. This review summarizes recent discoveries in the underlying mechanisms governing root ontogeny and discusses some recent key findings in developing of new biologically based dental therapies.

NKD2 Trigger NF-κB Signaling Pathway and Facilitates Thyroid Cancer Cell Proliferation

NKD inhibitor of WNT signaling pathway 2 (NKD2) is an emerging player in cancer onset and progression. Here, it was confirmed that THCA patients have robustly expressed NKD2, which was linked to an advanced pathologic stage. The prognosis was worse for those with high NKD2 levels. Functionally, ectopically produced NKD2 promotes THCA cell proliferation, whereas NKD2 knockdown impairs the ability of THCA cells to proliferate. Mechanically, ectopically expressed NKD2 activated NF-κB transcriptional activity, whereas NKD2-deficient THCA cells showed lower NF-κB transcriptional activity. As a result, NKD2 activates the NF-κB signaling pathway, encouraging the growth of THCA cells.

Construction and analysis of a lncRNA–miRNA–mRNA competing endogenous RNA network from inflamed and normal synovial tissues after anterior cruciate ligament and/or meniscus injuries

Background: Despite ample evidence demonstrating that anterior cruciate ligament (ACL) and meniscus tears are associated with posttraumatic osteoarthritis (PTOA) development, the contributing factors remain unknown. Synovial inflammation has recently been recognized as a pivotal factor in the pathogenesis of OA. However, there is a lack of data on synovial profiles after ACL or meniscus injuries, which may contribute to PTOA.

Methods: Twelve patients with ACL tears and/or meniscus injuries were recruited. During surgery, synovial tissues were obtained from the injured knees. The inflammation status of the synovium was characterized according to macroscopic criteria and histological synovitis grades. Then the synovial tissues were classified as control group or inflamed group. High-throughput RNA sequencing of the synovial samples (3 vs. 3) was conducted to identify differentially expressed (DE) RNAs. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein–protein interaction (PPI) analyses were performed to investigate DE mRNAs. Next, competing endogenous RNA (ceRNA) networks were constructed based on bioinformatics analyses. Associations of the identified DE genes (DEGs) with infiltrating immune cells were explored using Pearson correlation analysis.

Results: The results showed that 2793 mRNAs, 3392 lncRNAs and 211 miRNAs were significantly DE between two groups. The top 3 significantly upregulated GO terms and KEGG pathways were immune response, adaptive immune response and immune system process, systemic lupus erythematosus, haematopoietic cell lineage and cytokine–cytokine receptor interaction, respectively. In PPI networks, the top 10 hub genes were IL6, CCR7, C3, CCR5, CXCR3, CXCL8, IL2, CCR3, CCR2 and CXCL1. Seven mRNAs (EPHA5, GSN, ORC1, TLN2, SOX6, NKD2 and ADAMTS19), 4 lncRNAs (MIR4435-2HG, TNXA, CEROX1 and TMEM92-AS1) and 3 miRNAs (miR-486-5p, miR-199a-3p and miR-21-3p) were validated by quantitative real-time polymerase chain reaction and sub-networks were constructed. In correlation analysis, MMP9 correlated positively with M0 macrophages and plasma cells, NKD2 positively with CD8 T cells, and CCR7 and IL2RB positively with naive B cells.

Conclusion: Our study provides foundational synovial inflammation profiles following knee trauma. The ceRNA and PPI networks provide new insight into the biological processes and underlying mechanisms of PTOA. The differential infiltration profiles of immune cells in synovium may contribute to PTOA development. This study also highlights immune-related DEGs as potential PTOA treatment biomarkers.

Mechanisms during Osteogenic Differentiation in Human Dental Follicle Cells

Human dental follicle cells (DFCs) as periodontal progenitor cells are used for studies and research in regenerative medicine and not only in dentistry. Even if innovative regenerative therapies in medicine are often considered the main research area for dental stem cells, these cells are also very useful in basic research and here, for example, for the elucidation of molecular processes in the differentiation into mineralizing cells. This article summarizes the molecular mechanisms driving osteogenic differentiation of DFCs. The positive feedback loop of bone morphogenetic protein (BMP) 2 and homeobox protein DLX3 and a signaling pathway associated with protein kinase B (AKT) and protein kinase C (PKC) are presented and further insights related to other signaling pathways such as the WNT signaling pathway are explained. Subsequently, some works are presented that have investigated epigenetic modifications and non-coding ncRNAs and their connection with the osteogenic differentiation of DFCs. In addition, studies are presented that have shown the influence of extracellular matrix molecules or fundamental biological processes such as cellular senescence on osteogenic differentiation. The putative role of factors associated with inflammatory processes, such as interleukin 8, in osteogenic differentiation is also briefly discussed. This article summarizes the most important insights into the mechanisms of osteogenic differentiation in DFCs and is intended to be a small help in the direction of new research projects in this area.

Function of Dental Follicle Progenitor/Stem Cells and Their Potential in Regenerative Medicine: From Mechanisms to Applications

Dental follicle progenitor/stem cells (DFPCs) are a group of dental mesenchyme stem cells that lie in the dental follicle and play a critical role in tooth development and maintaining function. Originating from neural crest, DFPCs harbor a multipotential differentiation capacity. More importantly, they have superiorities, including the easy accessibility and abundant sources, active self-renewal ability and noncontroversial sources compared with other stem cells, making them an attractive candidate in the field of tissue engineering. Recent advances highlight the excellent properties of DFPCs in regeneration of orofacial tissues, including alveolar bone repair, periodontium regeneration and bio-root complex formation. Furthermore, they play a unique role in maintaining a favorable microenvironment for stem cells, immunomodulation and nervous related tissue regeneration. This review is intended to summarize the current knowledge of DFPCs, including their stem cell properties, physiological functions and clinical application potential. A deep understanding of DFPCs can thus inspire novel perspectives in regenerative medicine in the future.

Dental Follicle Cells: Roles in Development and Beyond

Dental follicle cells (DFCs) are a group of mesenchymal progenitor cells surrounding the tooth germ, responsible for cementum, periodontal ligament, and alveolar bone formation in tooth development. Cascades of signaling pathways and transcriptional factors in DFCs are involved in directing tooth eruption and tooth root morphogenesis. Substantial researches have been made to decipher multiple aspects of DFCs, including multilineage differentiation, senescence, and immunomodulatory ability. DFCs were proved to be multipotent progenitors with decent amplification, immunosuppressed and acquisition ability. They are able to differentiate into osteoblasts/cementoblasts, adipocytes, neuron-like cells, and so forth. The excellent properties of DFCs facilitated clinical application, as exemplified by bone tissue engineering, tooth root regeneration, and periodontium regeneration. Except for the oral and maxillofacial regeneration, DFCs were also expected to be applied in other tissues such as spinal cord defects (SCD), cardiomyocyte destruction. This article reviewed roles of DFCs in tooth development, their properties, and clinical application potentials, thus providing a novel guidance for tissue engineering.