Bone physiological microenvironment and healing mechanism: Basis for future bone-tissue engineering scaffolds

Bone-tissue defects affect millions of people worldwide. Despite being common treatment approaches, autologous and allogeneic bone grafting have not achieved the ideal therapeutic effect. This has prompted researchers to explore novel bone-regeneration methods. In recent decades, the development of bone tissue engineering (BTE) scaffolds has been leading the forefront of this field. As researchers have provided deep insights into bone physiology and the bone-healing mechanism, various biomimicking and bioinspired BTE scaffolds have been reported. Now it is necessary to review the progress of natural bone physiology and bone healing mechanism, which will provide more valuable enlightenments for researchers in this field. This work details the physiological microenvironment of the natural bone tissue, bone-healing process, and various biomolecules involved therein. Next, according to the bone physiological microenvironment and the delivery of bioactive factors based on the bone-healing mechanism, it elaborates the biomimetic design of a scaffold, highlighting the designing of BTE scaffolds according to bone biology and providing the rationale for designing next-generation BTE scaffolds that conform to natural bone healing and regeneration.

Umbilical cord and bone marrow mesenchymal stem cell seeding on macroporous calcium phosphate for bone regeneration in rat cranial defects

Human umbilical cord mesenchymal stem cells (hUCMSCs) are inexhaustible and can be harvested at a low cost without an invasive procedure. However, there has been no report on comparing hUCMSCs with human bone marrow MSCs (hBMSCs) for bone regeneration in vivo. The aim of this study was to investigate hUCMSC and hBMSC seeding on macroporous calcium phosphate cement (CPC), and to compare their bone regeneration in critical-sized cranial defects in rats. Cell attachment, osteogenic differentiation and mineral synthesis on RGD-modified macroporous CPC were investigated in vitro. Scaffolds with cells were implanted in 8-mm defects of athymic rats. Bone regeneration was investigated via micro-CT and histological analysis at 4, 12, and 24 weeks. Three groups were tested: CPC with hUCMSCs, CPC with hBMSCs, and CPC control without cells. Percentage of live cells and cell density on CPC in vitro were similarly good for hUCMSCs and hBMSCs. Both cells had high osteogenic expressions of alkaline phosphatase, osteocalcin, collagen I, and Runx2. Bone mineral density and trabecular thickness in hUCMSC and hBMSC groups in vivo were greater than those of CPC control group. New bone amount for hUCMSC-CPC and hBMSC-CPC constructs was increased by 57% and 88%, respectively, while blood vessel density was increased by 15% and 20%, than CPC control group at 24 weeks. hUCMSC-CPC and hBMSC-CPC groups generally had statistically similar bone mineral density, new bone amount and vessel density. In conclusion, hUCMSCs seeded on CPC were shown to match the bone regeneration efficacy of hBMSCs in vivo for the first time. Both hUCMSC-CPC and hBMSC-CPC constructs generated much more new bone and blood vessels than CPC without cells. Macroporous RGD-grafted CPC with stem cell seeding is promising for craniofacial and orthopedic repairs.

Human induced pluripotent stem cell-derived mesenchymal stem cell seeding on calcium phosphate scaffold for bone regeneration

Tissue engineering provides an important approach for bone regeneration. Calcium phosphate cement (CPC) can be injected to fill complex-shaped bone defects with excellent osteoconductivity. Induced pluripotent stem cells (iPSCs) are exciting for regenerative medicine due to their potential to proliferate and differentiate into cells of all three germ layers. To date, there has been no report on iPSC seeding with CPC scaffolds. The objectives of this study were to (1) obtain iPSC-derived mesenchymal stem cells (iPSC-MSCs); (2) seed iPSC-MSCs on CPC scaffold for the first time to investigate cell attachment and proliferation; and (3) investigate osteogenic differentiation of iPSC-MSCs on CPC and mineral synthesis by the cells. iPSCs were derived from adult marrow CD34+ cells that were reprogrammed by a single episomal vector pEB-C5. iPSCs were cultured to form embryoid bodies (EBs), and MSCs were migrated out of EBs. Flow cytometry indicated that iPSC-MSCs expressed typical surface antigen profile of MSCs. Mesenchymal differentiation of iPSC-MSCs demonstrated that the iPSC-MSCs had the potential to differentiate into adipocytes, chondrocytes, and osteoblasts. iPSC-MSCs had good viability when attached on CPC scaffold. iPSC-MSCs differentiated into the osteogenic lineage and synthesized bone minerals. iPSC-MSCs on CPC in osteogenic medium yielded higher gene expressions of osteogenic markers including alkaline phosphatase (ALP), osteocalcin, collagen type I, and Runt-related transcription factor 2 than those in control medium (p<0.05). iPSC-MSCs on CPC in osteogenic medium had 10-fold increase in ALP protein than that in control medium (p<0.05). Bone mineral synthesis by iPSC-MSCs adherent to CPC scaffold was increased with time, and mineralization in osteogenic medium was three to four fold that in control medium. In conclusion, iPSCs were derived from adult marrow CD34+ cells that were reprogrammed by a single episomal vector pEB-C5, and MSCs were generated from the EBs. iPSC-MSCs showed good viability and osteogenic differentiation on CPC scaffold for the first time; hence, the novel iPSC-MSC-CPC construct is promising to promote bone regeneration in dental, craniofacial, and orthopedic repairs.

Reprogramming of mesenchymal stem cells derived from iPSCs seeded on biofunctionalized calcium phosphate scaffold for bone engineering

Human induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) are a promising choice of patient-specific stem cells with superior capability of cell expansion. There has been no report on bone morphogenic protein 2 (BMP2) gene modification of iPSC-MSCs for bone tissue engineering. The objectives of this study were to: (1) genetically modify iPSC-MSCs for BMP2 delivery; and (2) to seed BMP2 gene-modified iPSC-MSCs on calcium phosphate cement (CPC) immobilized with RGD for bone tissue engineering. iPSC-MSCs were infected with green fluorescence protein (GFP-iPSC-MSCs), or BMP2 lentivirus (BMP2-iPSC-MSCs). High levels of GFP expression were detected and more than 68% of GFP-iPSC-MSCs were GFP positive. BMP2-iPSC-MSCs expressed higher BMP2 levels than iPSC-MSCs in quantitative RT-PCR and ELISA assays (p < 0.05). BMP2-iPSC-MSCs did not compromise growth kinetics and cell cycle stages compared to iPSC-MSCs. After 14 d in osteogenic medium, ALP activity of BMP2-iPSC-MSCs was 1.8 times that of iPSC-MSCs (p < 0.05), indicating that BMP2 gene transduction of iPSC-MSCs enhanced osteogenic differentiation. BMP2-iPSC-MSCs were seeded on CPC scaffold biofunctionalized with RGD (RGD-CPC). BMP2-iPSC-MSCs attached well on RGD-CPC. At 14 d, COL1A1 expression of BMP2-iPSC-MSCs was 1.9 times that of iPSC-MSCs. OC expression of BMP2-iPSC-MSCs was 2.3 times that of iPSC-MSCs. Bone matrix mineralization by BMP2-iPSC-MSCs was 1.8 times that of iPSC-MSCs at 21 d. In conclusion, iPSC-MSCs seeded on CPC were suitable for bone tissue engineering. BMP2 gene-modified iPSC-MSCs on RGD-CPC underwent osteogenic differentiation, and the overexpression of BMP2 in iPSC-MSCs enhanced differentiation and bone mineral production on RGD-CPC. BMP2-iPSC-MSC seeding on RGD-CPC scaffold is promising to enhance bone regeneration efficacy.

Colour stabilities of three types of orthodontic clear aligners exposed to staining agents

The aim of this study was to evaluate and compare the colour stabilities of three types of orthodontic clear aligners exposed to staining agents in vitro. Sixty clear orthodontic aligners produced by three manufacturers (Invisalign, Angelalign, and Smartee) were immersed in three staining solutions (coffee, black tea, and red wine) and one control solution (distilled water). After 12-h and 7-day immersions, the aligners were washed in an ultrasonic cleaner and measured with a colourimeter. The colour changes (ΔE*) were calculated on the basis of the Commission Internationale de I'Eclairage L*a*b* colour system (CIE L*a*b*), and the results were then converted into National Bureau of Standards (NBS) units. Fourier transformation infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were conducted to observe the molecular and morphologic alterations to the aligner surfaces, respectively. The three types of aligners exhibited slight colour changes after 12 h of staining, with the exception of the Invisalign aligners stained with coffee. The Invisalign aligners exhibited significantly higher ΔE* values (ranging from 0.30 to 27.81) than those of the Angelalign and Smartee aligners (ΔE* values ranging from 0.33 to 1.89 and 0.32 to 1.61, respectively, P<0.05). FT-IR analysis confirmed that the polymer-based structure of aligners did not exhibit significant chemical differences before and after the immersions. The SEM results revealed different surface alterations to the three types of aligner materials after the 7-day staining. The three types of aesthetic orthodontic appliances exhibited colour stability after the 12-h immersion, with the exception of the Invisalign aligners stained by coffee. The Invisalign aligners were more prone than the Angelalign and Smartee aligners to pigmentation. Aligner materials may be improved by considering aesthetic colour stability properties.

Human umbilical cord stem cell encapsulation in novel macroporous and injectable fibrin for muscle tissue engineering

There has been little research on the seeding of human umbilical cord mesenchymal stem cells (hUCMSCs) in three-dimensional scaffolds for muscle tissue engineering. The objectives of this study were: (i) to seed hUCMSCs in a fibrin hydrogel containing fast-degradable microbeads (dMBs) to create macropores to enhance cell viability; and (ii) to investigate the encapsulated cell proliferation and myogenic differentiation for muscle tissue engineering. Mass fractions of 0-80% of dMBs were tested, and 35% of dMBs in fibrin was shown to avoid fibrin shrinkage while creating macropores and promoting cell viability. This construct was referred to as "dMB35". Fibrin without dMBs was termed "dMB0". Microbead degradation created macropores in fibrin and improved cell viability. The percentage of live cells in dMB35 reached 91% at 16 days, higher than the 81% in dMB0 (p<0.05). Live cell density in dMB35 was 1.6-fold that of dMB0 (p<0.05). The encapsulated hUCMSCs proliferated, increasing the cell density by 2.6 times in dMB35 from 1 to 16 days. MTT activity for dMB35 was substantially higher than that for dMB0 at 16 days (p<0.05). hUCMSCs in dMB35 had high gene expressions of myotube markers of myosin heavy chain 1 (MYH1) and alpha-actinin 3 (ACTN3). Elongated, multinucleated cells were formed with positive staining of myogenic specific proteins including myogenin, MYH, ACTN and actin alpha 1. Moreover, a significant increase in cell fusion was detected with myogenic induction. In conclusion, hUCMSCs were encapsulated in fibrin with degradable microbeads for the first time, achieving greatly enhanced cell viability and successful myogenic differentiation with formation of multinucleated myotubes. The injectable and macroporous fibrin-dMB-hUCMSC construct may be promising for muscle tissue engineering applications.

Calcium phosphate cement with biofunctional agents and stem cell seeding for dental and craniofacial bone repair

OBJECTIVE

Calcium phosphate cement (CPC) can be injected to harden in situ and is promising for dental and craniofacial applications. However, human stem cell attachment to CPC is relatively poor. The objectives of this study were to incorporate biofunctional agents into CPC, and to investigate human umbilical cord mesenchymal stem cell (hUCMSC) seeding on biofunctionalized CPC for osteogenic differentiation for the first time.

METHODS

Five types of biofunctional agents were used: RGD (Arg-Gly-Asp) peptides, human fibronectin (Fn), fibronectin-like engineered polymer protein (FEPP), extracellular matrix Geltrex, and human platelet concentrate. Five biofunctionalized CPC scaffolds were fabricated: CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. The hUCMSC attachment, proliferation, osteogenic differentiation and mineral synthesis were measured.

RESULTS

The hUCMSCs on biofunctionalized CPCs had much better cell attachment, proliferation, actin fiber expression, osteogenic differentiation and mineral synthesis, compared to the traditional CPC control. Cell proliferation was increased by an order of magnitude via incorporation of biofunctional agents in CPC (p<0.05). Mineral synthesis on biofunctionalized CPCs was 3-5 folds of those of control (p<0.05). hUCMSCs differentiated with high alkaline phosphatase, Runx2, osteocalcin, and collagen I gene expressions. Mechanical properties of biofunctionalized CPC matched the reported strength and elastic modulus of cancellous bone.

SIGNIFICANCE

A new class of biofunctionalized CPCs was developed, including CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. hUCMSCs on biofunctionalized CPCs had cell density, cell proliferation, actin fiber density, and bone mineralization that were dramatically better than those on traditional CPC. Novel biofunctionalized CPC scaffolds with greatly enhanced human stem cell proliferation and differentiation are promising to facilitate bone regeneration in a wide range of dental, craniofacial and orthopedic applications.

Induced pluripotent stem cell-derived mesenchymal stem cell seeding on biofunctionalized calcium phosphate cements

Induced pluripotent stem cells (iPSCs) have great potential due to their proliferation and differentiation capability. The objectives of this study were to generate iPSC-derived mesenchymal stem cells (iPSC-MSCs), and investigate iPSC-MSC proliferati on and osteogenic differentiation on calcium phosphate cement (CPC) containing biofunctional agents for the first time. Human iPSCs were derived from marrow CD34+ cells which were reprogrammed by a single episomal vector. iPSCs were cultured to form embryoid bodies (EBs), and MSCs migrated out of EBs. Five biofunctional agents were incorporated into CPC: RGD (Arg-Gly-Asp) peptides, fibronectin (Fn), fibronectin-like engineered polymer protein (FEPP), extracellular matrix Geltrex, and platelet concentrate. iPSC-MSCs were seeded on five biofunctionalized CPCs: CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. iPSC-MSCs on biofunctional CPCs had enhanced proliferation, actin fiber expression, osteogenic differentiation and mineralization, compared to control. Cell proliferation was greatly increased on biofunctional CPCs. iPSC-MSCs underwent osteogenic differentiation with increased alkaline phosphatase, Runx2 and collagen-I expressions. Mineral synthesis by iPSC-MSCs on CPC-Platelets was 3-fold that of CPC control. In conclusion, iPSCs showed high potential for bone engineering. iPSC-MSCs on biofunctionalized CPCs had cell proliferation and bone mineralization that were much better than traditional CPC. iPSC-MSC-CPC constructs are promising to promote bone regeneration in craniofacial/orthopedic repairs.

Analysis of time-course gene expression profiles of a periodontal ligament tissue model under compression

OBJECTIVE

We recently reported establishment of a periodontal ligament (PDL) tissue model, which may mimic the biological behaviour of human PDL under static compression in orthodontic tooth movement (OTM). In the present study, we aimed at investigating the time-course gene expression profiles of the PDL tissue model under compression.

DESIGN

The PDL tissue model was established through 3-D-culturing human PDL cells (PDLCs) in a thin sheet of porous poly lactic-co-glycolic acid (PLGA) scaffolds, which was subjected to 25g/cm(2) static compression for 6, 24 and 72h respectively. After that, its gene expression profiles were investigated using microarray assay, followed by signalling pathway and gene ontology (GO) analysis. Real-time RT-PCR verification was done for 15 identified genes of interest. The cell proliferation alteration was detected through EdU labelling.

RESULTS

(1) Among the genes identified as differentially expressed, there were numerous osteoclastogenesis inducers (including CCL20, COX-1, COX-2, RANKL, PTHrP, IL-11, IL-8, etc.), osteoclastogenesis inhibitors (including IL-1Ra, NOG, OPG, etc.), and other potential bone remodelling regulators (including STC1, CYR61, FOS, etc.). (2) According to analysis of the microarray data, the most significant pathways included Cytokine-cytokine receptor interaction (containing CCL20, RANKL, IL-11, IL-8, etc.), MAPK (containing FGF7, FOS, MAP3K8, JUN, etc.) and Cell cycle (containing CDK1, CCNA2, etc.); the most significant GOs included Cell-cell signalling (containing CCL20, STC1, FGF7, PTHrP, IL-11, IL-8, etc.), Extracellular space (containing CCL20, IL-1Ra, NOG, PTHrP, IL-11, IL-8, etc.) and Microtubule-based movement (containing KIF11, KIF23, etc.). (3) After prolonged compression, cell proliferation was significantly inhibited.

CONCLUSION

The present findings have expanded our understandings to the roles that PDL plays under static compression in OTM.

The relevance between the immune response-related gene module and clinical traits in head and neck squamous cell carcinoma

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer in the world, accounting for more than 90% of head and neck malignant tumors. However, its molecular mechanism is largely unknown. To help elucidate the potential mechanism of HNSCC tumorigenesis, we investigated the gene interaction patterns associated with tumorigenesis.

METHODS

Weighted gene co-expression network analysis (WGCNA) can help us to predict the intrinsic relationship or correlation between gene expression. Additionally, we further explored the combination of clinical information and module construction.

RESULTS

Sixteen modules were constructed, among which the key module most closely associated with clinical information was identified. By analyzing the genes in this module, we found that the latter may be related to the immune response, inflammatory response and formation of the tumor microenvironment. Sixteen hub genes were identified-ARHGAP9, SASH3, CORO1A, ITGAL, PPP1R16B, TBC1D10C, IL10RA, ITK, AKNA, PRKCB, TRAF3IP3, GIMAP4, CCR7, P2RY8, GIMAP7, and SP140. We further validated these genes at the transcriptional and translation levels.

CONCLUSION

The innovative use of a weighted network to analyze HNSCC samples provides new insights into the molecular mechanism and prognosis of HNSCC. Additionally, the hub genes we identified can be used as biomarkers and therapeutic targets of HNSCC, laying the foundation for the accurate diagnosis and treatment of HNSCC in clinical and research in the future.

Prospect of circular RNA in osteogenesis: A novel orchestrator of signaling pathways

Circular RNAs (circRNAs) were initially regarded as by-products of aberrant splicing. But now, there are substantial evidence on their various roles in the regulation of genes during the development of organs and diseases. Consistent with these breakthroughs, it is experiencing rapid growth that circRNAs function as the important checkpoints during the osteogenesis. Therefore, characterizing the roles of circRNAs is useful and critical to better understanding the process of osteogenic differentiation, which could provide new avenues for the diagnosis and treatment of bone diseases, such as bone defects and osteoporosis. In this review, we presented a map of the interaction between circRNAs and the molecules of signaling pathways associated with osteogenesis, summarized the current knowledge of the biological functions of circRNAs during the osteogenic differentiation, figured out the limits of existing research works, and provided a novel look on the diagnostic and therapeutic methods of bone diseases based on circRNAs.

The roles of circRFWD2 and circINO80 during NELL-1-induced osteogenesis

Bone defects caused heavy social and economic burdens worldwide. Nel-like molecule, type 1 (NELL-1) could enhance the osteogenesis and the repairment of bone defects, while the specific mechanism remains to be elucidated. Circular RNAs (circRNAs) have been found to play critical roles in the tissue development and serve as biomarkers for various diseases. However, it remains unclear that the expression patterns of circRNAs and the roles of them played in recombinant NELL-1-induced osteogenesis of human adipose-derived stem cells (hASCs). In this study, we performed RNA-sequencing to investigate the expression profiles of circRNAs in recombinant NELL-1-induced osteogenic differentiation and identified two key circRNAs, namely circRFWD2 and circINO80. These two circRNAs were confirmed to be up-regulated during recombinant NELL-1-induced osteogenesis, and knockdown of them affected the positive effect of NELL-1 on osteogenesis. CircRFWD2 and circINO80 could interact with hsa-miR-6817-5p, which could inhibit the osteogenesis. Silencing hsa-miR-6817-5p could partially reverse the negative effect of si-circRFWD2 and si-circINO80 on the osteogenesis. Therefore, circRFWD2 and circINO80 could regulate the expression of hsa-miR-6817-5p and influence the recombinant NELL-1-induced osteogenic differentiation of hASCs. It opens a new window to better understanding the effects of NELL-1 on the osteogenic differentiation of hASCs and provides potential molecular targets and novel methods for bone regeneration efficiently and safely.

Knowledge of orthodontic tooth movement through the maxillary sinus: a systematic review

BACKGROUND

To investigate the feasibility, safety and stability of current interventions for moving teeth through the maxillary sinus (MTTMS) by performing a systematic review of the literature.

METHODS

The electronic databases PubMed, Embase, CENTRAL, Web of Science, CBM, CNKI and SIGLE were searched without a language restriction. The primary outcomes were parameters related to orthodontic treatment, including orthodontic protocols, magnitude of forces, type of tooth movement, duration and rate of tooth movement, and remolding of alveolar bone and the maxillary sinus floor. The secondary outcomes were safety and stability, including root resorption, perforation of the sinus floor, loss of pulp vitality and periodontal health and relapse.

RESULTS

Nine case reports with 25 teeth were included and systematically analyzed. Fifty to two hundred g of force was applied to move teeth through the maxillary sinus. Bodily movement was accomplished, but initial tipping was observed in 7 cases. The rate was 0.6-0.7 mm/month for molar intrusion and 0.16-1.17 and 0.05-0.16 mm/month for mesial-distal movement of premolars and molars, respectively. Bone formation and remolding of the sinus floor occurred in 7 cases. Root resorption within 6 to 30 months was observed in 3 cases, while no cases of perforation of the sinus floor, loss of pulp vitality, periodontal health impairment or relapse were reported.

CONCLUSIONS

At the present stage, no evidence-based protocol could be recommended to guide MTTMS. The empirical application of constant and light to moderate forces (by TAD, segment and multibrackets) to slowly move teeth through or into the maxillary sinus in adults appears to be practical and secure. Bodily movement was accomplished, but teeth appear to be easily tipped initially, potentially resulting in root resorption. However, this conclusion should be interpreted with caution as the currently available evidence is based on only a few case reports or case series and longitudinal or controlled studies are lacking in this area.

Fast-degradable microbeads encapsulating human umbilical cord stem cells in alginate for muscle tissue engineering

Human umbilical cord mesenchymal stem cells (hUCMSCs) are inexhaustible and can be obtained without an invasive surgery. To date, there has been no report on seeding hUCMSCs in three-dimensional scaffolds for muscle tissue engineering. The objectives of this study were to (1) investigate hUCMSC seeding in a scaffold for muscle engineering and (2) develop a novel construct consisting of hUCMSC-encapsulating and fast-degradable microbeads inside a hydrogel matrix. The rationale was that the hydrogel matrix would maintain the defect volume, while the microbeads would degrade to release the cells and concomitantly create macropores in the matrix. hUCMSCs were encapsulated in alginate-fibrin microbeads, which were packed in an Arg-Gly-Asp (RGD)-modified alginate matrix (AM). This construct is referred to as hUCMSC-microbead-AM. The control consisted of the usual cell encapsulation in AM without microbeads (referred to as hUCMSC-AM). In the hUCMSC-AM construct, the hUCMSCs showed as round dots with no spreading at 1-14 days. In contrast, cells in the hUCMSC-microbead-AM construct had a healthy spreading and elongated morphology. The microbeads successfully degraded and released the cells at 8 days. Myogenic expressions for hUCMSC-microbead-AM were more than threefold those of hUCMSC-AM (p<0.05). Immunofluorescence for myogenic markers was much stronger for hUCMSC-microbead-AM than hUCMSC-AM. Muscle creatine kinase of hUCMSC-microbead-AM at 14 days was twofold that of hUCMSC-AM (p<0.05). In conclusion, hUCMSC encapsulation in novel fast-degradable microbeads inside a hydrogel matrix was investigated for muscle engineering. Compared to the usual method of seeding cells in a hydrogel matrix, hUCMSC-microbead-AM construct had greatly improved cell viability and myogenic differentiation, and hence, is promising to enhance muscle regeneration.

Effect of NELL1 gene overexpression in iPSC-MSCs seeded on calcium phosphate cement

Human induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) are a promising source of patient-specific stem cells with great regenerative potential. There has been no report on NEL-like protein 1 (NELL1) gene modification of iPSC-MSCs. The objectives of this study were to genetically modify iPSC-MSCs with NELL1 overexpression for bone tissue engineering, and investigate the osteogenic differentiation of NELL1 gene-modified iPSC-MSCs seeded on Arg-Gly-Asp (RGD)-grafted calcium phosphate cement (CPC) scaffold. Cells were transduced with red fluorescence protein (RFP-iPSC-MSCs) or NELL1 (NELL1-iPSC-MSCs) by a lentiviral vector. Cell proliferation on RGD-grafted CPC scaffold, osteogenic differentiation and bone mineral synthesis were evaluated. RFP-iPSC-MSCs stably expressed high levels of RFP. Both the NELL1 gene and NELL1 protein levels were confirmed higher in NELL1-iPSC-MSCs than in RFP-iPSC-MSCs using RT-PCR and Western blot (P<0.05). Alkaline phosphatase activity was increased by 130% by NELL1 overexpression at 14days (P<0.05), indicating that NELL1 promoted iPSC-MSC osteogenic differentiation. When seeded on RGD-grafted CPC, NELL1-iPSC-MSCs attached and expanded similarly well to RFP-iPSC-MSCs. At 14days, the runt-related transcription factor 2 (RUNX2) gene level of NELL1-iPSC-MSCs was 2.0-fold that of RFP-iPSC-MSCs. The osteocalcin (OC) level of NELL1-iPSC-MSCs was 3.1-fold that of RFP-iPSC-MSCs (P<0.05). The collagen type I alpha 1 (COL1A1) gene level of NELL1-iPSC-MSCs was 1.7-fold that of RFP-iPSC-MSCs at 7days (P<0.05). Mineral synthesis was increased by 81% in NELL1-iPSC-MSCs at 21days. In conclusion, NELL1 overexpression greatly enhanced the osteogenic differentiation and mineral synthesis of iPSC-MSCs on RGD-grafted CPC scaffold for the first time. The novel NELL1-iPSC-MSC seeded RGD-CPC construct is promising for enhancing bone engineering.

MicroRNAs-containing extracellular vesicles in bone remodeling: An emerging frontier

Bone remodeling is a complex and constant process, which is maintained by well-regulated communication among various cells. Extracellular vesicles (EVs) are small vesicles, which could provide a protective environment for the transportation of various functional molecules. It has been shown that EVs could dock with distant and/or neighboring target cells, deliver cargoes to these specific cells and alter their fates. MicroRNAs (miRNAs), single-stranded non-coding RNAs with 22-26 nucleotides, could bind to mRNAs and repress the translation or stimulate the degradation of mRNAs. It is reported that EVs could serve as the mail carriers, which could cargo miRNAs to exchange information between different cells and act through a novel way to regulate signaling pathways during bone remodeling. In this review, we summarize the function of EV-miRNAs in the communication among mesenchymal stem cells (MSCs), osteoblasts, osteoclasts, osteocytes, and myoblasts during bone remodeling, as well as the key signaling molecules which are involved in this process. The roles of EV-miRNAs in sending intercellular messages in the microenvironment of bone remodeling could shed new light on the development of tissue engineering, and provide novel diagnostic markers and therapeutic targets of bone-related diseases.

circ_0003204 regulates the osteogenic differentiation of human adipose-derived stem cells via miR-370-3p/HDAC4 axis

Human adipose-derived stem cells (hASCs) are a promising cell type for bone tissue regeneration. Circular RNAs (circRNAs) have been shown to play a critical role in regulating various cell differentiation and involve in mesenchymal stem cell osteogenesis. However, how circRNAs regulate hASCs in osteogenesis is still unclear. Herein, we found circ_0003204 was significantly downregulated during osteogenic differentiation of hASCs. Knockdown of circ_0003204 by siRNA or overexpression by lentivirus confirmed circ_0003204 could negatively regulate the osteogenic differentiation of hASCs. We performed dual-luciferase reporting assay and rescue experiments to verify circ_0003204 regulated osteogenic differentiation via sponging miR-370-3p. We predicted and confirmed that miR-370-3p had targets in the 3'-UTR of HDAC4 mRNA. The following rescue experiments indicated that circ_0003204 regulated the osteogenic differentiation of hASCs via miR-370-3p/HDAC4 axis. Subsequent in vivo experiments showed the silencing of circ_0003204 increased the bone formation and promoted the expression of osteogenic-related proteins in a mouse bone defect model, while overexpression of circ_0003204 inhibited bone defect repair. Our findings indicated that circ_0003204 might be a promising target to promote the efficacy of hASCs in repairing bone defects.

Functional analysis of lncRNAs based on competitive endogenous RNA in tongue squamous cell carcinoma

BACKROUND

Tongue squamous cell carcinoma (TSCC) is the most common malignant tumor in the oral cavity. An increasing number of studies have suggested that long noncoding RNA (lncRNA) plays an important role in the biological process of disease and is closely related to the occurrence and development of disease, including TSCC. Although many lncRNAs have been discovered, there remains a lack of research on the function and mechanism of lncRNAs. To better understand the clinical role and biological function of lncRNAs in TSCC, we conducted this study.

METHODS

In this study, 162 tongue samples, including 147 TSCC samples and 15 normal control samples, were investigated and downloaded from The Cancer Genome Atlas (TCGA). We constructed a competitive endogenous RNA (ceRNA) regulatory network. Then, we investigated two lncRNAs as key lncRNAs using Kaplan-Meier curve analysis and constructed a key lncRNA-miRNA-mRNA subnetwork. Furthermore, gene set enrichment analysis (GSEA) was carried out on mRNAs in the subnetwork after multivariate survival analysis of the Cox proportional hazards regression model.

RESULTS

The ceRNA regulatory network consists of six differentially expressed miRNAs (DEmiRNAs), 29 differentially expressed lncRNAs (DElncRNAs) and six differentially expressed mRNAs (DEmRNAs). Kaplan-Meier curve analysis of lncRNAs in the TSCC ceRNA regulatory network showed that only two lncRNAs, including LINC00261 and PART1, are correlated with the total survival time of TSCC patients. After we constructed the key lncRNA-miRNA -RNA sub network, the GSEA results showed that key lncRNA are mainly related to cytokines and the immune system. High expression levels of LINC00261 indicate a poor prognosis, while a high expression level of PART1 indicates a better prognosis.

Effect of protraction facemask on the temporomandibular joint: a systematic review

BACKGROUND

The aim of this study was to assess the influence of protraction facemask (PFM) on temporomandibular joint (TMJ) of skeletal Class III malocclusion patients.

METHOD

Literature searches were carried out electronically in five English and three Chinese databases (Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed, Embase, MEDLINE (via Ovid), Chinese Biomedical Literature Database, China National Knowledge Infrastructure, and VIP Database). The date of the most recent search was 22 March 2017. Randomized controlled trials, controlled clinical trials, cohort studies, and before-after studies comparing the effect of PFM and other treatments on TMJ were included. The data were collected and extracted by three authors. The risk of bias in the RCTs was assessed in accordance with the Cochrane Handbook for Systematic Reviews of Interventions. For the nonrandomized studies, the risk of bias was judged with Newcastle-Ottawa Scale.

RESULTS

For the 261 articles identified, 13 studies with 522 participants were included for the final qualitative analysis. Three studies were graded as high value of evidence, while seven studies and the other three studies were graded as moderate value and low value respectively. According to the available evidence, PFM contributed to the significant increase of CondAx-SBL and the significant decrease of CondAx-ML. Thin-plate spline (TPS) analysis showed a horizontal compression in condyles. Condyles tended to move superiorly and posteriorly. Concerning the occurrence of temporomandibular disorders (TMD), PFM was not involved in aggravating TMJ symptoms and signs.

CONCLUSIONS

Clinical evidence suggests that PFM might contribute to the morphologic adaptation of TMJs and displacement of condyles, and PFM may well be not a risk factor for the development of TMD.

METTL3-Mediated lncRNA m6A Modification in the Osteogenic Differentiation of Human Adipose-Derived Stem Cells Induced by NEL-Like 1 Protein

OBJECTIVES

This study aimed to explore the regulatory mechanism of methyltransferase3 (METTL3) -mediated long non-coding RNA (lncRNA) N6-methyladenosine (m⁶A) modification in the osteogenic differentiation of human adipose-derived stem cells (hASCs) induced by NEL-like 1 protein (NELL-1).

MATERIALS AND METHODS

Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and high- throughput sequencing for RNA (RNA-seq) were performed on hASCs. Osteogenic ability was detected by alkaline phosphatase (ALP) staining, Alizarin Red S(ARS) staining, ALP quantification and Quantitative real-time polymerase chain reaction analysis (qRT-PCR). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis predicted the osteogenesis-related pathways enriched for the lncRNAs and identified the target lncRNAs. After overexpression and knockdown of METTL3, methylated RNA immunoprecipitation-qPCR (MeRIP-qPCR) and qRT-PCR were used to detect the levels of m⁶A modification and the expression of the target lncRNA, and the binding of both was confirmed by RNA binding protein immunoprecipitation (RIP) assay. The effects of lncRNA and METTL3 on phosphorylation of the key proteins of the pathway were detected by western blot analysis.

RESULTS

In vitro experiments showed that METTL3 can promote osteogenic differentiation and that its expression level is upregulated. KEGG pathway analysis predicted that lncRNAs with differentially upregulated methylated peaks were enriched mostly in the mitogen-activated protein kinase (MAPK) signaling pathway, in which Serine/threonine protein kinase 3 (STK3) was the predicted target gene of the lncRNA RP11-44 N12.5. The m⁶A modification and expression of RP11-44 N12.5 were both regulated by METTL3. Subsequently, lncRNA RP11-44 N12.5 and METTL3 were found to regulate the phosphorylation levels of three key proteins in the MAPK signaling pathway, ERK, JNK and p38.

CONCLUSIONS

This study shows, for the first time, that METTL3 can activate the MAPK signaling pathway by regulating the m⁶A modification and expression of a lncRNA, thereby enhancing the osteogenic differentiation of hASCs.

The impact of surgery-first approach on the oral health-related quality of life: a systematic review and meta-analysis

BACKGROUND

The oral health-related quality of life (OHRQoL) is affected by dentofacial deformity. Patients with dentofacial deformity are normally treated with orthognathic surgery, including conventional three-stage method (CTM) and surgery first approach (SFA). The aim of this systematic review and meta-analysis was to compare the impact of SFA with CTM on the OHRQoL of patients with severe dentofacial deformity.

METHODS

Five English databases, three Chinese databases, and six grey literature databases were searched (January 2000 to July 2018). Randomized controlled trials, controlled clinical trials, and cohort studies assessing the OHRQoL of patients who underwent SFA or CTM were included. After selecting studies, extracting data, and assessing risk-of-bias according to the Cochrane Handbook for Systematic Reviews of Interventions and the Newcastle-Ottawa Scale, meta-analysis was performed to elucidate the effects of SFA on the changes of OHRQoL of patients with dentofacial deformity at each stage and made a comparison with CTM.

RESULTS

There were 4 studies with 122 participants were selected for the final analysis. Three among these studies were included in meta-analysis, 2 of which were included in each forest plot. All the included studies were graded as moderate value of evidence according to GRADE quality analysis. Over the period of 2-year follow-up after bonding, the OHRQoL of the patients in SFA group showed an improving trend and was better than those in CTM group generally. After debonding, the summary scores of the 14-item Oral Health Impact Profile (OHIP-14) (- 2.92, P = 0.12) and Orthognathic Quality of Life Questionnaire (OQLQ) (- 5.59, P = 0.01) were smaller in SFA group than CTM group.

CONCLUSIONS

Clinical evidence indicates that SFA can contribute to the better OHRQoL in patients with dentofacial deformity immediately and persistently.

Effect of iRoot Fast Set root repair material on the proliferation, migration and differentiation of human dental pulp stem cells in vitro

The present study investigated the effect of iRoot Fast Set root repair material (iRoot FS) on the proliferation, migration and differentiation of human dental pulp stem cells (hDPSCs). The hDPSCs were treated with eluates of iRoot FS at concentrations of 0.2 and 2 mg/mL, referred to as FS0.2 and FS2, respectively, and Biodentine (BD; Septodont, Saint Maur des Faussés, France) eluates at the corresponding concentrations as positive controls. A CCK8 assay was performed to determine cell proliferation. Wound healing and transwell assays were conducted to examine cell migration. Osteogenic differentiation was evaluated based on alkaline phosphatase activity, Alizarin Red S staining and quantitative real-time reverse-transcriptase polymerase chain reaction (qRT-PCR) to analyze the mRNA expression of differentiation gene markers. Cell proliferation was higher in the FS and BD groups than in the blank controls at 3 and 7 days. Moreover, FS0.2 enhanced cell migration and significantly promoted the osteogenic differentiation of hDPSCs. These findings suggested that iRoot FS is a bioactive material that promotes the proliferation, migration and osteogenic differentiation of hDPSCs.

Cytocompatibility of Biodentine and iRoot FS with human periodontal ligament cells: an in vitro study

AIM

To evaluate the cytocompatibility of Biodentine and iRoot FS with human periodontal ligament cells (hPDLCs).

METHODOLOGY

Human periodontal ligament cells were characterized by flow cytometry and immunocytochemical analysis. Human periodontal ligament cell adhesion was assessed by scanning electron microscopy at day 3; proliferation by live/dead assay at days 1, 3 and 7; and osteogenic differentiation by alkaline phosphatase (ALP) activity staining, ALP quantification analysis and qRT-PCR at days 7 and 14. Data were analysed with anova and independent sample t-tests with SPSS 21.0.

RESULTS

Both iRoot FS and Biodentine increased the adhesion of hPDLCs at day 3. Compared to Biodentine, iRoot FS positively increased hPDLC proliferation on days 3 (P = 0.03) and 7 (P = 0.00). Osteogenic marker ALP was observed consistently in all samples, with iRoot FS having significantly higher ALP activity at day 14 (P = 0.00). Compared with Biodentine, iRoot FS significantly increased the mRNA level of ALP, COL1 and Runx2, and OCN increased only on day 14 (P < 0.05).

CONCLUSIONS

iRoot FS had a positive effect on the adhesion, proliferation and biomineralization of hPDLCs compared with Biodentine.

DNA methylation of noncoding RNAs: new insights into osteogenesis and common bone diseases

Bone diseases such as osteoarthritis, osteoporosis, and bone tumor present a severe public health problem. Osteogenic differentiation is a complex process associated with the differentiation of different cells, which could regulate transcription factors, cytokines, many signaling pathways, noncoding RNAs (ncRNAs), and epigenetic modulation. DNA methylation is a kind of stable epigenetic alterations in CpG islands without DNA sequence changes and is involved in cancer and other diseases, including bone development and homeostasis. ncRNAs can perform their crucial biological functions at the RNA level, and many findings have demonstrated essential functions of ncRNAs in osteogenic differentiation. In this review, we highlight current researches in DNA methylation of two relevant ncRNAs, including microRNAs and long noncoding RNAs, in the initiation and progression of osteogenesis and bone diseases.