Effects of Innervation on Angiogenesis and Osteogenesis in Bone and Dental Tissue Engineering.

The repair and regeneration of critical-sized bone defects remain an urgent challenge. Bone tissue engineering represents an exciting solution for regeneration of large bone defects. Recently, the importance of innervation in tissue-engineered bone regeneration has been increasingly recognized. The cross talk between nerve and bone provides important clues for bone repair and regeneration. Furthermore, the promotion of angiogenesis by innervation can accelerate new bone formation. However, the mechanisms involved in the promotion of vascular and bone regeneration by the nervous system have not yet been established. In addition, simultaneous neurogenesis and vascularization in bone tissue engineering have not been fully investigated. This article represents the first review on the effects of innervation in enhancing angiogenesis and osteogenesis in bone and dental tissue engineering. Cutting-edge research on the effects of innervation through biomaterials on bone and dental tissue repairs is reviewed. The effects of various nerve-related factors and cells on bone regeneration are discussed. Finally, novel clinical applications of innervation for bone, dental, and craniofacial tissue regeneration are also examined.

Smart Dental Materials Intelligently Responding to Oral pH to Combat Caries: A Literature Review.

Smart dental materials are designed to intelligently respond to physiological changes and local environmental stimuli to protect the teeth and promote oral health. Dental plaque, or biofilms, can substantially reduce the local pH, causing demineralization that can then progress to tooth caries. Progress has been made recently in developing smart dental materials that possess antibacterial and remineralizing capabilities in response to local oral pH in order to suppress caries, promote mineralization, and protect tooth structures. This article reviews cutting-edge research on smart dental materials, their novel microstructural and chemical designs, physical and biological properties, antibiofilm and remineralizing capabilities, and mechanisms of being smart to respond to pH. In addition, this article discusses exciting and new developments, methods to further improve the smart materials, and potential clinical applications.

Osteogenic Differentiation Effect of Human Periodontal Ligament Stem-Cell Initial Cell Density on Autologous Cells and Human Bone Marrow Stromal Cells.

Stem cells have differentiation and regulation functions. Here, we discussed the impact of cell culture density on stem cell proliferation, osteoblastogenesis, and regulation. To discuss the effect of the initial culture density of human periodontal ligament stem cells (hPDLSCs) on the osteogenic differentiation of autologous cells, we found that the hPDLSC proliferation rate decreased with an increase in the initial plating density (0.5-8 × 104 cells/cm2) for the 48 h culture cycle. After hPDLSCs induced osteogenic differentiation for 14 days with different initial cell culture densities, the expression of osteoprotegerin (OPG) and runt-related transcription factor 2(RUNX2) and the OPG/ Receptor Activator of Nuclear Factor-κ B Ligand (RANKL) ratio were the highest in the hPDLSCs initially plated at a density of 2 × 104 cells/cm2, and the average cell calcium concentration was also the highest. To study hPDLSCs regulating the osteoblastic differentiation of other cells, we used 50 µg/mL of secreted exosomes derived from hPDLSCs cultured using different initial cell densities to induce human bone marrow stromal cell (hBMSC) osteogenesis. After 14 days, the results indicated that the gene expression of OPG, Osteocalcin(OCN,)RUNX2, and osterix and the OPG/RANKL ratio were the highest in the 2 × 104 cells/cm2 initial cell density group, and the average calcium concentration was also the highest. This provides a new idea for the clinical application of stem cell osteogenesis.

Effects of Metformin Delivery via Biomaterials on Bone and Dental Tissue Engineering.

Bone tissue engineering is a promising approach that uses seed-cell-scaffold drug delivery systems to reconstruct bone defects caused by trauma, tumors, or other diseases (e.g., periodontitis). Metformin, a widely used medication for type II diabetes, has the ability to enhance osteogenesis and angiogenesis by promoting cell migration and differentiation. Metformin promotes osteogenic differentiation, mineralization, and bone defect regeneration via activation of the AMP-activated kinase (AMPK) signaling pathway. Bone tissue engineering depends highly on vascular networks for adequate oxygen and nutrition supply. Metformin also enhances vascular differentiation via the AMPK/mechanistic target of the rapamycin kinase (mTOR)/NLR family pyrin domain containing the 3 (NLRP3) inflammasome signaling axis. This is the first review article on the effects of metformin on stem cells and bone tissue engineering. In this paper, we review the cutting-edge research on the effects of metformin on bone tissue engineering. This includes metformin delivery via tissue engineering scaffolds, metformin-induced enhancement of various types of stem cells, and metformin-induced promotion of osteogenesis, angiogenesis, and its regulatory pathways. In addition, the dental, craniofacial, and orthopedic applications of metformin in bone repair and regeneration are also discussed.

Novel nanostructured resin infiltrant containing calcium phosphate nanoparticles to prevent enamel white spot lesions.

OBJECTIVES: The objective of this study was to develop a novel nanostructured resin infiltrant containing nanoparticles of amorphous calcium phosphate (NACP) to treat enamel white spot lesions (WSLs). Physical properties and the therapeutic effect of the new resin infiltrant were investigated for the first time. METHODS: NACP was incorporated into ICON (Icon caries infiltrant, DMG, Germany) with different mass fractions. Cytotoxicity, degree of conversion, surface hardness, calcium (Ca) and phosphorus (P) ions release concentrations were tested. After application to the demineralized enamel samples, the color changes were determined. Surface and cross-sectional hardness were measured, scanning electron microscopy (SEM) images were taken on the cross-section of samples to observe microstructure changes after 14-day pH cycling. RESULTS: Incorporating 10%-30% of NACP did not compromise the biocompatibility and physical properties of the resin infiltrant. ICON + 30% NACP group had long-lasting and high level of Ca and P ion release. After 14-day pH cycling, enamel surface hardness of ICON + 30% NACP group was 1.83 ± 0.21 GPa, significantly higher than the control group (1.32 ± 0.18 GPa) (p < 0.05). ICON + 30NACP group had the highest cross-sectional enamel hardness among all groups (p < 0.05), especially at 50 µm and 100 µm depth. SEM images showed that apparent enamel prism and inter-prism gaps in negative control were masked by mineral deposition in ICON + 30% NACP group. SIGNIFICANCE: The novel ICON+30% NACP infiltrant is promising to inhibit enamel WSLs, protect the enamel and increase its hardness.

The effect of somatosensory alpha transcranial alternating current stimulation on pain empathy is trait empathy and gender dependent.

BACKGROUND: Pain empathy enables a person to experience and understand other's pain state by observing others in pain condition. Such prosocial ability is deficient in many psychopathological disorders. Somatosensory alpha suppression is considered as neural correlates of pain empathy and is hypothesized as a target for enhancement of pain empathy. Researches demonstrated that alpha suppression could be enhanced by transcranial alternating current stimulation (tACS) at alpha frequency non-invasively. AIMS: We applied alpha tACS over the primary somatosensory cortex of healthy subjects to investigate whether alpha tACS is able to enhance the pain empathy performance. RESULTS: The results showed that there was no difference of pain empathy performance between alpha tACS and sham tACS either when tACS was applied during the task or before task. While in the alpha tACS group, the pain empathy performance was positively correlated with empathic concern of male subjects, the sub-component of personal trait empathy. CONCLUSIONS: Alpha tACS cannot alter the empathy performance overall, but the modulation effect of alpha tACS on pain empathy is dependent on the gender and trait empathy of subjects.

Flow analysis of aortic dissection: comparison of inflow boundary conditions for computational models based on 4D PCMRI and Doppler ultrasound.

Computational hemodynamics quantifying the flow environment is an important tool in understanding aortic dissection. In this study, various inflow boundaries were applied on a patient-specific model and compared to the individualized velocimetry. The results indicated that the computations generally overestimated the flow volume and underestimated the wall shear stress. By quantifying the accuracy of the simulation results, two inflow settings were suggested. One was individualized, the PCMRI-extracted 4D flow information, and the other was averaged by healthy data, the ultrasound-extracted averaged flow waveform with parabolic velocity profile. This study might contribute to improving the precise computation of aortic dissection hemodynamics.

[Effects of Aging on Endothelium-dependent Vasodilation of Human Artery].

OBJECTIVE: To determine the effects of aging on endothelium-dependent vasodilation of human artery. METHODS: Vessel tension changes induced by acetylcholine (ACh) and endothelial-derived hyperpolarizing factor (EDHF) on gastroepiploic artery rings were recorded in 15 patients with stomach cancer aged between 51 and 83 years. The mRNA expressions of endothelial nitric oxide synthase (eNOS), cyclooxygenase (COX), cystathionineγ lyase (CSE) and the C-type natriuretic peptide (CNP) in the artery vessels were detected by qRT-PCR. RESULTS: Both endothelium-dependent and EDHF induced vasodilation decreased with age (P<0.05). The mRNA expressions of eNOS, CSE and CNP also decreased with age (P<0.05), except COX. CONCLUSION: Aging could impair the function of endothelium-dependent vasodilation and EDHF-induced vasodialtion of human artery, possibly due to decreased NO, H2S and CNP in artery.

G-Protein-gated Inwardly-Rectifying K+ Channels and Large-conductance Calcium-Activated K+ Channels Are Involved in C-Type Natriuretic Peptide-Mediated Vasodilation in Human Arteries.

C-type natriuretic peptide (CNP) hyperpolarizes and relaxes the smooth muscle of blood vessels. We investigated whether G-protein-gated inwardly-rectifying K+ channels (GIRK) and large-conductance calcium-activated K+ channels (BKCa channels) were involved in CNP-evoked vasodilatation in human arteries. Isometric tension in human gastroepiploic arteries was measured using a wire myograph. Ion channel currents were recorded by the whole-cell patch-clamp technique. The concentration-dependent vasodilation induced by CNP was reduced significantly after inhibition of GIRK channels (by tertiapin-Q) or of BKCa channel (by paxilline). Immunochemical experiments showed that GIRK3 and GIRK4 subunits were expressed in human arteries. CNP also strongly increased the current density of GIRK and BKCa channels in human arterial smooth muscles. This suggested that the GIRK channel was functionally expressed in smooth muscle and vasodilation action was produced by CNP partly by opening the GIRK and BKCa channels in the human artery.

Vascular Remodelling Relates to an Elevated Oscillatory Shear Index and Relative Residence Time in Spontaneously Hypertensive Rats.

Haemodynamic disorders are common clinical findings in hypertension and lead to adverse cardiovascular events. However, the haemodynamic conditions in hypertension models are poorly understood. This study aimed to observe the characteristics of haemodynamics in spontaneously hypertensive rats (SHRs) and antihypertensive-treated SHRs. Twenty-four adult male SHRs and Wistar-Kyoto rats (WKYs) were randomly divided into four groups and treated for 7 days as follows: WKY-CON (WKYs + saline), WKY-NIF (WKYs + nifedipine, 50 mg/kg/day), SHR-CON (SHRs + saline), and SHR-NIF (SHRs + nifedipine). Aortic computational fluid dynamics (CFD) models were simulated to obtain the haemodynamic parameters. We found that in the hypertensive (SHR-CON) and blood pressure-controlled (SHR-NIF) groups, the oscillatory shear index (OSI) and relative residence time (RRT), which are key haemodynamics indices, were markedly elevated. Furthermore, there was a correlation between both the elevated OSI and RRT with the vascular wall thickening in regions near the inner wall of the aortic arch. Our research demonstrates that haemodynamics remains disturbed even if the blood pressure is normalized. In addition, vascular remodelling may play an important role in maintaining elevated OSI and RRT values.

The risk of stanford type-A aortic dissection with different tear size and location: a numerical study.

BACKGROUND: This study is to investigate the influence of hemodynamics on Stanford type-A aortic dissection with different tear size and location, to provide some support for the relationships between the risks (rupture, reverse tearing and further tearing) and tear size and location for clinical treatment. METHODS: Four numerical models of Stanford type-A aortic dissection were established, with different size and location of the tears. The ratio of the area between the entry and re-entry tears(RA) is various within the model; while, the size and the location of the re-entry in the distal descending aorta are fixed. In model A11 and A21, the entry tears are located near the ascending aorta. The RA in these models are 1 and 2, respectively; In the model B11 and B21, the entry tears are located near the proximal descending aorta and the RA in these models are again assigned to 1 and 2, respectively. Then hemodynamics in these models was solved with numerically and the flow patterns and loading distributions were investigated. RESULTS: The flow velocity of the true lumen in model A21, B21 is lower than that in A11, B11, respectively; the time-averaged wall shear stress (TAWSS) of the false lumen in model A21 and B21 is higher, and for ascending aorta false lumen, A11, A21 are higher than B11, B21, respectively. False lumen intimal wall pressure of A11, A21 are always higher than the true lumen ones. CONCLUSION: The variation of the RA can significantly affect the dynamics of blood within the aortic dissection. When the entry tear size is larger than the re-entry tear ones, the false lumen, proximal descending aorta and the wall near re-entry tear are prone to cracking. Entry tear location can significantly alter the hemodynamics of aortic dissection as well. When entry tear location is closer to proximal ascending aorta, false lumen continues to expand and compress the true lumen resulting in the true lumen reduction. For proximal ascending aorta, high pressure in false lumen predicts a higher risk of reverse tear.

Radiation pharmacogenomics: a genome-wide association approach to identify radiation response biomarkers using human lymphoblastoid cell lines.

Radiation therapy is used to treat half of all cancer patients. Response to radiation therapy varies widely among patients. Therefore, we performed a genome-wide association study (GWAS) to identify biomarkers to help predict radiation response using 277 ethnically defined human lymphoblastoid cell lines (LCLs). Basal gene expression levels and 1.3 million genome-wide single nucleotide polymorphism (SNP) markers from both Affymetrix and Illumina platforms were assayed for all 277 human LCLs. MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assays for radiation cytotoxicity were also performed to obtain area under the curve (AUC) as a radiation response phenotype for use in the association studies. Functional validation of candidate genes, selected from an integrated analysis that used SNP, expression, and AUC data, was performed with multiple cancer cell lines using specific siRNA knockdown, followed by MTS and colony-forming assays. A total of 27 loci, each containing at least two SNPs within 50 kb with P-values less than 10(-4) were associated with radiation AUC. A total of 270 expression probe sets were associated with radiation AUC with P < 10(-3). The integrated analysis identified 50 SNPs in 14 of the 27 loci that were associated with both AUC and the expression of 39 genes, which were also associated with radiation AUC (P < 10(-3)). Functional validation using siRNA knockdown in multiple tumor cell lines showed that C13orf34, MAD2L1, PLK4, TPD52, and DEPDC1B each significantly altered radiation sensitivity in at least two cancer cell lines. Studies performed with LCLs can help to identify novel biomarkers that might contribute to variation in response to radiation therapy and enhance our understanding of mechanisms underlying that variation.

Laminar shear stress regulates liver X receptor in vascular endothelial cells.

OBJECTIVE: The liver X receptors (LXRs) regulate a set of genes involved in lipid metabolism and reverse cholesterol transport. We investigated the mechanism by which shear stress regulates LXR in vascular endothelial cells (ECs). METHODS AND RESULTS: Western blot showed that the protein level of LXRalpha and its target ABCA1 in the mouse thoracic aorta was higher than that in the aortic arch. As well, the mRNA level of LXR and its target genes ABCA1, ABCG1, ApoE, and LPL in the thoracic aorta was higher. In vitro, bovine aortic ECs were subjected to a steady laminar flow (12 dyne/cm2). The expressions of LXR and the LXR-mediated transcription were increased by laminar shear stress. Laminar flow increased LXR-ligand binding and the gene expression of sterol 27-hydroxylase (CYP27), which suggests an increased level of LXR ligand in ECs. This effect was attenuated by LXRalpha and CYP27 RNAi. The decrease of LXR in the aorta of PPARgamma+/- mice and that of C57 mice fed with PPARgamma antagonist suggest the involvement of PPARgamma in the LXR induction by flow. CONCLUSIONS: Laminar flow increases LXR function via a PPARgamma-CYP27 dependent mechanism, which reveals an atheroprotective role for laminar flow exerting on endothelium.

Statins activate AMP-activated protein kinase in vitro and in vivo.

BACKGROUND: Statins exert pleiotropic effects on the cardiovascular system, in part through an increase in nitric oxide (NO) bioavailability. AMP-activated protein kinase (AMPK) plays a central role in controlling energy and metabolism homeostasis in various organs. We therefore studied whether statins can activate AMPK, and if so, whether the activated AMPK regulates nitric oxide (NO) production and angiogenesis mediated by endothelial NO synthase, a substrate of AMPK in vascular endothelial cells. METHODS AND RESULTS: Western blotting of protein extracts from human umbilical vein endothelial cells treated with atorvastatin revealed increased phosphorylation of AMPK at Thr-172 in a time- and dose-dependent manner. The AMPK activity, assessed by SAMS assay, was also increased accordingly. The phosphorylation of acetyl-CoA carboxylase at Ser-79 and of endothelial NO synthase at Ser-1177, 2 putative downstream targets of AMPK, was inhibited by an adenovirus that expressed a dominant-negative mutant of AMPK (Ad-AMPK-DN) and compound C, an AMPK antagonist. The positive effects of atorvastatin, including NO production, cGMP accumulation, and in vitro angiogenesis in Matrigel, were all blocked by Ad-AMPK-DN. Mice given atorvastatin through gastric gavage showed increased AMPK, acetyl-CoA carboxylase, and endothelial NO synthase phosphorylation in mouse aorta and myocardium. CONCLUSIONS: Statins can rapidly activate AMPK via increased Thr-172 phosphorylation in vitro and in vivo. Such phosphorylation results in endothelial NO synthase activation, which provides a novel explanation for the pleiotropic effects of statins that benefit the cardiovascular system.

Sterol-responsive element-binding protein (SREBP) 2 down-regulates ATP-binding cassette transporter A1 in vascular endothelial cells: a novel role of SREBP in regulating cholesterol metabolism.

ATP-binding cassette transporter A1 (ABCA1) is a pivotal regulator of cholesterol efflux from cells to apolipoproteins, whereas sterol-responsive element-binding protein 2 (SREBP2) is the key protein regulating cholesterol synthesis and uptake. We investigated the regulation of ABCA1 by SREBP2 in vascular endothelial cells (ECs). Our results showed that sterol depletion activated SREBP2 and increased its target, low density lipoprotein receptor mRNA, with a concurrent decrease in the ABCA1 mRNA. Transient transfection analysis revealed that sterol depletion decreased the ABCA1 promoter activity by 50%, but low density lipoprotein receptor promoter- and the sterol-responsive element-driven luciferase activities were increased. Overexpression of the N terminus of SREBP2 (SREBP2(N)), an active form of SREBP2, also inhibited the ABCA1 promoter activity. Functionally adenovirus-mediated SREBP2(N) expression increased cholesterol accumulation and decreased apoA-I-mediated cholesterol efflux. The conserved E-box motif was responsible for the SREBP2(N)-mediated inhibition since mutation of the E-box increased the basal activity of the ABCA1 promoter and abolished the inhibitory effect of SREBP2(N). Furthermore sterol depletion and SREBP2(N) overexpression induced the binding of SREBP2(N) to both consensus and ABCA1-specific E-box. Chromatin immunoprecipitation assay demonstrated that serum starvation enhanced the association of SREBP2 and the ABCA1 promoter in ECs. To correlate this mechanism pathophysiologically, we found that oscillatory flow caused the activation of SREBP2 and therefore attenuated ABCA1 promoter activity in ECs. Thus, this SREBP-regulated mechanism may control the efflux of cholesterol, which is a newly defined function of SREBP2 in ECs in addition to its role in cholesterol uptake and biosynthesis.

Impact of nitric oxide on adrenomedullin- and proadrenomedullin N-terminal 20 peptide-induced cardiac responses: action by alone and combined administration.

The cardiac effects of adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) as well as the possible signaling pathways were investigated. In the isolated perfused rat heart, infusion of AM (10(-11) to 10(-8) M) and PAMP(10(-11) to 10(-8) M) for 10 min, alone or in combination, induced concentration-dependent decreases in the left ventricular pressure (LVP), LVP +/- dp/dtmax of the hearts. The effects were attenuated by Nomega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase. ADM and PAMP alone or in combinations increased the coronary fluid (CF), which could be antagonized by L-NAME. Pretreatment of H89, an inhibitor of protein kinase A (PKA), failed to alter the AM- or PAMP-induced decreases in LVP and LVP +/- dp/dtmax, but further promoted the AM or PAMP increased CF. The cAMP content in left cardiac ventricle was increased significantly by ADM infusions but not by PAMP. There was no statistical difference in cAMP contents with ADM administrated alone from those combined with ADM and PAMP. In conclusion, this study reveals that ADM and PAMP infused alone or in combinations inhibited the function of rat hearts in vitro, which may be partly involved with the NOS/NO pathway, rather than cAMP/PKA.