Osteocytes autophagy mediated by mTORC2 activation controls osteoblasts differentiation and osteoclasts activities under mechanical loading.

Autophagy is an important mechanosensitive response for cellular homeostasis and survival in osteocytes. However, the mechanism and its effect on bone metabolism have not yet clarified. The objective of this study was to evaluate how compressive cyclic force (CCF) induced autophagic response in osteocytes and to determine the effect of mechanically induced-autophagy on bone cells including osteocytes, osteoblasts, and osteoclasts. Autophagic puncta observed in MLO-Y4 cells increased after exposure to CCF. The upregulated levels of the LC3-II isoform and the degradation of p62 further confirmed the increased autophagic flux. Additionally, ATP synthesis and release, osteocalcin (OCN) expression, and cell survival increased in osteocytes as well. The Murine osteoblasts MC3T3-E1 cells and RAW 264.7 macrophage cells were cultured in conditioned medium collected from MLO-Y4 cells subjected to CCF. The concentration of FGF23 increased and the concentrations of SOST and M-CSF and RANKL/OPG ratio decreased significantly in the conditioned medium. Moreover, the promotion of osteogenic differentiation in MC3T3-E1 cells and inhibition of osteoclastogenesis and function in RAW 264.7 cells were significantly attenuated when osteocytes autophagy was inhibited by siAtg7. Our findings suggested that CCF induced protective autophagy in osteocytes and subsequently enhanced osteocytes survival and osteoblasts differentiation and downregulated osteoclasts activities. Further study revealed that CCF induced autophagic response in osteocytes through mechanistic target of rapamycin complex 2 (mTORC2) activation. In conclusion, CCF-induced osteocytes autophagy upon mTORC2 activation promoted osteocytes survival and osteogenic response and decreased osteoclastic function. Thus, osteocytes autophagy will provide a promising target for better understanding of bone physiology and treatment of bone diseases.

An engineered lamellar bone mimicking full-scale hierarchical architecture for bone regeneration.

Lamellar bone, compactly and ingeniously organized in the hierarchical pattern with 6 ordered scales, is the structural motif of mature bone. Each hierarchical scale exerts an essential role in determining physiological behavior and osteogenic bioactivity of bone. Engineering lamellar bone with full-scale hierarchy remains a longstanding challenge. Herein, using bioskiving and mineralization, we attempt to engineer compact constructs resembling full-scale hierarchy of lamellar bone. Through systematically investigating the effect of mineralization on physicochemical properties and bioactivities of multi-sheeted collagen matrix fabricated by bioskiving, the hierarchical mimicry and hierarchy-property relationship are elucidated. With prolongation of mineralization, hierarchical mimicry and osteogenic bioactivity of constructs are performed in a bidirectional manner, i.e. first rising and then descending, which is supposed to be related with transformation of mineralization mechanism from nonclassical to classical crystallization. Construct mineralized 9 days can accurately mimic each hierarchical scale and efficiently promote osteogenesis. Bioinformatic analysis further reveals that this construct potently activates integrin α5-PI3K/AKT signaling pathway through mechanical and biophysical cues, and thereby repairing critical-sized bone defect. The present study provides a bioinspired strategy for completely resembling complex hierarchy of compact mineralized tissue, and offers a critical research model for in-depth studying the structure-function relationship of bone.

A Self-Healing Multifunctional Hydrogel System Accelerates Diabetic Wound Healing through Orchestrating Immunoinflammatory Microenvironment.

Developing an effective treatment strategy of drug delivery to improve diabetic wound healing remains a major challenge in clinical practice nowadays, due to multidrug-resistant bacterial infections, angiopathy, and oxidative damage in the wound microenvironment. Herein, an effective and convenient strategy was designed through a self-healing multiple-dynamic-bond cross-linked hydrogel with interpenetrating networks, which was formed by multiple-dynamic-bond cross-linking of reversible catechol-Fe3+ coordinate bonds, hydrogen bonding, and Schiff base bonds. The excellent autonomous healing of the hydrogel was initiated and accelerated by Schiff bonds with reversible breakage between 3,4-dihydroxybenzaldehyde containing catechol and aldehyde groups and chitosan chains, and further consolidated by the co-optation of other noncovalent interactions contributed of hydrogen bonding and Fe3+ coordinate bonds. Intriguingly, cathelicidin LL-37 was introduced and uniformly dispersed in the dynamic interpenetrating networks of the hydrogel as a bioactive molecular to orchestrate the diabetic wound healing microenvironment. This multifunctional wound dressing can significantly promote diabetic wound healing by antibacterial activity, immunomodulation, anti-inflammation, neovascularization, and antioxidant activity. Therefore, this study provided an effective and safe strategy for guiding the diabetic wound treatment in clinical applications.

Periodontitis and stroke: A Mendelian randomization study.

BACKGROUND AND PURPOSE: Periodontitis has been implicated in the incidence of ischemic stroke. However, the generalizability of results to individuals with different subtypes of periodontitis is unknown. We aimed to investigate the causal relationship of chronic periodontitis (CP) and aggressive periodontitis (AgP) with ischemic stroke and its subtypes in the Mendelian randomization framework. METHODS: The genetic proxies of CP were derived from large-scale summary statistics from the UK Biobank datasets (950 cases and 455,398 controls). The genetic associations of AgP were selected from another large genome-wide association study of European ancestry (851 cases and 6836 controls). The instruments of ischemic stroke (34,217 cases and 406,111 controls) and its subtypes were selected from the MEGASTROKE consortium of European ancestry. The inverse variant weighted method was performed to determine the causal inference and a comprehensive set of sensitivity analyses to test the robustness of the results. RESULTS: In population-wide genetic analysis, there was no association of genetically predicted AgP (odds ratio [OR], 0.982; 95% confidence interval [CI], 0.956-1.009; p = .197) with ischemic stroke or its subtypes. For patients with CP, there was also no significant causal inference on ischemic stroke (OR, 1.017; 95% CI, 0.992-1.043; p = .184). However, regarding the stroke subtypes, the genetic analysis provided evidence of a causal relationship of CP with cardioembolic stroke (OR, 1.052; 95% CI, 1.002-1.104; p = .042), but not with large artery atherosclerosis (OR, 1.005; 95% CI, 0.944-1.069; p = .875) or small vessel occlusion (OR, 1.039; 95% CI, 0.981-1.101; p = .193). CONCLUSION: This study suggested that there was a potential causal effect of CP on cardioembolic stroke.

Anti-Acid Biomimetic Dentine Remineralization Using Inorganic Silica Stabilized Nanoparticles Distributed Electronspun Nanofibrous Mats.

BACKGROUND: To manage the sharp pain of dentine hypersensitivity, various materials are utilized to conduct dentine remineralization. However, many prior materials are limited with their single function and complicated operations. In this study, silica and calcium (strontium) carbonates mineralized nano cellulose fibrous (Si/Ca(Sr)-NCF) mat with the ability to release acid resistant and biomimetic mineralizational silica/calcium (strontium) carbonate co-precipitation nanoparticles (Si/Ca(Sr) NPs) were fabricated. The dentine occluding effects, antibacterial activity and cytocompatibility of the Si/Ca(Sr)-NCF mats were evaluated. METHODS: The Si/Ca(Sr)-NCF mats were fabricated by dipping the electrospun nano cellulose fiber (NCF) into silica and calcium (strontium) carbonate liquid. Physicochemical characterizations and ion release were confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ion release assays and transmission electron microscopy (TEM). Sixty dentine discs were randomly divided into five groups: 1, blank NCF; 2, Si/Ca(Sr 0)-NCF; 3, Si/Ca(Sr 0.01)-NCF; 4, Si/Ca(Sr 0.05)-NCF; 5, Si/Ca(Sr 0.1)-NCF. Dentine discs were mineralized by the mats and observed with SEM immediately, after acid challenge and remineralized in artificial saliva. The releasing liquid was investigated by TEM and type I collagen model. Then, antibacterial property and cytocompatibility were evaluated. RESULTS: SEM and TEM results confirmed that the experiment mats continuously released amorphous Si/Ca(Sr) NPs and consequently realized anti-acid dentine biomimetic remineralization. Homogeneous surface coverage and collagen intrafibrillar mineralization in strontium adding groups illustrated the mineralization effect was not only by in site precipitation, but also collagen heterogeneous nucleation. Additionally, acceptable antibacterial and cytocompatibility properties were illustrated in low and middle Sr2+ containing mats. CONCLUSION: In vitro studies on human dentine discs and type I collagen demonstrated that Si/Ca(Sr)-NCF system was a multifunction system inducing anti-acid, biomimetic, antibacterial and cytocompatible dentine remineralization. This multifunction mat would be a promising DH treatment candidate for complicated exposed dentine surfaces.

The Construction of Biomimetic Cementum Through a Combination of Bioskiving and Fluorine-Containing Biomineralization.

Despite tremendous attention is given to the construction of biomimetic cementum for regeneration of tooth cementum, the lack of recapitulating the composition and hierarchical structure of cementum often leads to the poor performance of constructed materials. How to highly mimic the sophisticated composition and hierarchy of cementum remains a longstanding challenge in constructing the biomimetic cementum. Inspired by cementum formation process, a novel construction approach via a combination of bioskiving and fluorine-containing biomineralization is developed in this study. The alternative collagen lamellae (ACL) that can highly mimic the rotated plywood structure of cementum collagen matrix is fabricated via bioskiving. Followed by biomineralization in the amorphous calcium phosphate (ACP) solution with different concentration of fluorine, a series of biomimetic cementum is constructed. Screened by physicochemical characterization, the biomimetic cementum with the composition and hierarchical structure highly similar to human cementum is selected. Through in vitro biological assay, this biomimetic cementum is proven to significantly promote the adhesion, proliferation, and cementogenic differentiation of periodontal ligament cells (PDLCs). Furthermore, in vivo study demonstrates that biomimetic cementum could induce cementogenesis. This biomimetic cementum constructed via combinatory application of bioskiving and fluorine-containing biomineralization stands as a promising candidate for achieving cementum regeneration.

Two-year observation of the occlusal vertical dimension after bite raising via cone-beam computerized tomography: A preliminary study.

Variation of the occlusal vertical dimension (OVD) has been discussed empirically for decades, but it has not been thoroughly explored with experimental data. In the present study, cone-beam computerized tomography (CBCT) of six selected patients was conducted to evaluate the bones of the lower facial structures. The anterior lower facial heights (ALFHs), alveolar process heights (APHs), vertical facial pattern (VFP), occluding dentition height (ODH) and condyle space (CS), which were evaluated by three-dimensional (3D) and two-dimensional (2D) lateral cephalometry derived from CBCT, were compared before and two years after the OVD increased full mouth rehabilitation. Consistent significant increases in ALFHs and the VFP indicated the OVD increase, while a significant decrease in the ΔODH indicated compressed dentition. In addition, 55 of the 56 sites (98.21%) of APH measurement illustrated no significant difference before and after treatment. The findings indicated that the increased OVD did not relapse to baseline and was sufficiently tolerated, with mostly constant APHs and an altered ODH after two years of observation in the six patients.