Boosted Second Harmonic Generation and Cascaded Sum Frequency Generation from a Surface Crystallized Glass Ceramic Microcavity.

The development of novel materials and structures for efficient second-order nonlinear micro/nano devices remains a significant challenge. In this study, the remarkable enhancement of second-harmonic generation (SHG) and cascaded sum frequency generation in whispering gallery mode microspheres made of surface-crystallized glass with a 6-µm Ba2TiSi2O8 crystal layer are demonstrated. Attributed to the core-shell design, the Ba2TiSi2O8 located on the surface can be efficiently coupled with whispering gallery modes, resulting in a highly efficient micron-scale cavity-enhanced second-order optical nonlinearity. Greatly enhanced SHG of the microcavity is observed, which is up to 80 times stronger than that of a non-resonant sample. Furthermore, owing to the wavelength non-selectivity of random quasi-phase matching, ultra-wideband SHG with a strong response ranging from 860 to 1600 nm and high-contrast polarization characteristics is demonstrated. The glass-ceramic-based microsphere cavity also boosts the cascading optical nonlinearity, manifested by a two-magnitude enhancement of cascaded sum frequency generation. This work delineates an efficient strategy for boosting nonlinear optical response in glass ceramics, which will open up new opportunities for applications in photonics and optical communications.

3D printed PLGA/MgO/PDA composite scaffold by low-temperature deposition manufacturing for bone tissue engineering applications.

Introduction: Bones are easily damaged. Biomimetic scaffolds are involved in tissue engineering. This study explored polydopamine (PDA)-coated poly lactic-co-glycolic acid (PLGA)-magnesium oxide (MgO) scaffold properties and its effects on bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation. Methods: PLGA/MgO scaffolds were prepared by low-temperature 3D printing technology and PDA coatings were prepared by immersion method. Scaffold structure was observed by scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), fourier transform infrared spectrometer (FTIR). Scaffold hydrophilicity, compressive/elastic modulus, and degradation rates were analyzed by water contact angle measurement, mechanical tests, and simulated-body fluid immersion. Rat BMSCs were cultured in scaffold extract. Cell activity on days 1, 3, and 7 was detected by MTT. Cells were induced by osteogenic differentiation, followed by evaluation of alkaline phosphatase (ALP) activity on days 3, 7, and 14 of induction and Osteocalcin, Osteocalcin, and Collagen I expressions. Results: The prepared PLGA/MgO scaffolds had dense microparticles. With the increase of MgO contents, the hydrophilicity was enhanced, scaffold degradation rate was accelerated, magnesium ion release rate and scaffold extract pH value were increased, and cytotoxicity was less when magnesium mass ratio was less than 10%. Compared with other scaffolds, compressive and elastic modulus of PLGA/MgO (10%) scaffolds were increased; BMSCs incubated with PLGA/MgO (10%) scaffold extract had higher ALP activity and Osteocalcin, Osteopontin, and Collagen I expressions. PDA coating was prepared in PLGA/MgO (10%) scaffolds and the mechanical properties were not affected. PLGA/MgO (10%)/PDA scaffolds had better hydrophilicity and biocompatibility and promoted BMSC osteogenic differentiation. Conclusion: Low-temperature 3D printing PLGA/MgO (10%)/PDA scaffolds had good hydrophilicity and biocompatibility, and were conducive to BMSC osteogenic differentiation.

Bone marrow mesenchymal stem cell-derived exosomes attenuate the maturation of dendritic cells and reduce the rejection of allogeneic transplantation.

BACKGROUND: Bone mesenchymal stem cell (BMSC)-derived exosomes (B-exos) are attractive for applications in enabling alloantigen tolerance. An in-depth mechanistic understanding of the interaction between B-exos and dendritic cells (DCs) could lead to novel cell-based therapies for allogeneic transplantation. OBJECTIVES: To examine whether B-exos exert immunomodulatory effects on DC function and maturation. MATERIAL AND METHODS: After mixed culture of BMSCs and DCs for 48 h, DCs from the upper layer were collected to analyze the expression levels of surface markers and mRNAs of inflammation-related cytokines. Then, before being collected to detect the mRNA and protein expression levels of indoleamine 2,3-dioxygenase (IDO), the DCs were co-cultured with B-exos. Then, the treated DCs from different groups were co-cultured with naïve CD4+ T cells from the mouse spleen. The proliferation of CD4+ T cells and the proportion of CD4+CD25+Foxp3+ T cells were analyzed. Finally, the skins of BALB/c mice were transplanted to the back of C57 mice in order to establish a mouse allogeneic skin transplantation model. RESULTS: The co-culture of DCs with BMSCs downregulated the expression of the major histocompatibility complex class II (MHC-II) and CD80/86 costimulatory molecules on DCs. Moreover, B-exos increased the expression of IDO in DCs treated with lipopolysaccharide (LPS). The proliferation of CD4+CD25+Foxp3+ T cells increased when cultured with B-exos-exposed DCs. Finally, mice recipients injected with B-exos-treated DCs had significantly prolonged survival after receiving the skin allograft. CONCLUSIONS: Taken together, these data suggest that the B-exos suppress the maturation of DCs and increase the expression of IDO, which might shed light on the role of B-exos in inducing alloantigen tolerance.

BMSC-derived exosomal miR-27a-3p and miR-196b-5p regulate bone remodeling in ovariectomized rats.

Background: In the bone marrow microenvironment of postmenopausal osteoporosis (PMOP), bone marrow mesenchymal stem cell (BMSC)-derived exosomal miRNAs play an important role in bone formation and bone resorption, although the pathogenesis has yet to be clarified. Methods: BMSC-derived exosomes from ovariectomized rats (OVX-Exo) and sham-operated rats (Sham-Exo) were co-cultured with bone marrow-derived macrophages to study their effects on osteoclast differentiation. Next-generation sequencing was utilized to identify the differentially expressed miRNAs (DE-miRNAs) between OVX-Exo and Sham-Exo, while target genes were analyzed using bioinformatics. The regulatory effects of miR-27a-3p and miR-196b-5p on osteogenic differentiation of BMSCs and osteoclast differentiation were verified by gain-of-function and loss-of-function analyses. Results: Osteoclast differentiation was significantly enhanced in the OVX-Exo treatment group compared to the Sham-Exo group. Twenty DE-miRNAs were identified between OVX-Exo and Sham-Exo, among which miR-27a-3p and miR-196b-5p promoted the expressions of osteogenic differentiation markers in BMSCs. In contrast, knockdown of miR-27a-3p and miR-196b-5p increased the expressions of osteoclastic markers in osteoclast. These 20 DE-miRNAs were found to target 11435 mRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these target genes were involved in several biological processes and osteoporosis-related signaling pathways. Conclusion: BMSC-derived exosomal miR-27a-3p and miR-196b-5p may play a positive regulatory role in bone remodeling.

A 3D-printed bioactive polycaprolactone scaffold assembled with core/shell microspheres as a sustained BMP2-releasing system for bone repair.

Integration of biological factors and hierarchical rigid scaffolds is of great interest in bone tissue engineering for fabrication of biomimetic constructs with high physical and biological performance for enhanced bone repair. Core/shell microspheres (CSMs) delivering bone morphogenetic protein-2 (BMP-2) and a strategy to integrate CSMs with 3D-printed scaffolds were developed herein to form a hybrid 3D system for bone repair. The scaffold was printed with polycaprolactone (PCL) and then coated with polydopamine. Shells of CSMs were electrosprayed with alginate. Cores were heparin-coated polylactic acid (PLA) microparticles fabricated via simple emulsion and heparin coating strategy. Assembly of microspheres and scaffolds was realized via a self-locking method with the assistance of controlled expansion of CSMs. The hybrid system was evaluated in the rat critical-sized bone defect model. CSMs released BMP-2 in a tunable manner and boosted osteogenic performance in vitro. CSMs were then successfully integrated inside the scaffolds. The assembled system effectively promoted osteogenesis in vitro and in vivo. These observations show the importance of how BMP-2 is delivered, and the core/shell microspheres represent effective BMP-2 carriers that could be integrated into scaffolds, together forming a hybrid system as a promising candidate for enhanced bone regeneration.

Analysis of differential expression of long non­coding RNAs in exosomes derived from mature and immature dendritic cells.

Dendritic cells release bioactive exosomes involved in immune regulation. Long non­coding RNAs (lncRNAs) are implicated in a number of immunoregulatory mechanisms. However, the roles of lncRNAs in dendritic cell­derived exosomes remain to be elucidated. The present study aimed to investigate the roles of lncRNAs in exosomes derived from mature and immature dendritic cells and to find specific lncRNAs with immunoregulatory function. The expression profiles of lncRNAs in exosomes derived from bone marrow dendritic cells of C57 mice were illustrated. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses and Gene Set Enrichment Analysis were performed to identify potential targets correlated with immune regulation. In addition, lncRNA­miRNA­mRNA networks were predicted using bioinformatics methods. Representative lncRNAs were further validated via reverse transcription­quantitative PCR. A total of 437 lncRNAs were analyzed using RNA­seq. Among these, the expression of ~87 lncRNAs was upregulated and 21 lncRNAs was downregulated in mature dendritic cell­derived exosomes (Dex) compared with immature Dex. GO analyses indicated the involvement of upregulated lncRNAs in multiple biological functions, such as the immune system process, while downregulated lncRNAs were involved in poly(A) RNA binding. Analysis of the KEGG pathway identified the relationship of TNF signaling and ribosome pathway with upregulated lncRNAs and downregulated lncRNAs, respectively. The results of gene set enrichment analysis identified that three lncRNA­associated transcripts (Procr­203, Clec4e­202 and Traf1­203) were highly associated with immunoregulatory functions including T helper cell differentiation and Janus kinase­STAT signaling pathway. The results indicated the involvement of candidate lncRNAs in immunoregulation and suggested a new perspective on the modulation of lncRNAs in Dex.

Biomechanical Comparison of Stand-Alone and Bilateral Pedicle Screw Fixation for Oblique Lumbar Interbody Fusion Surgery-A Finite Element Analysis.

BACKGROUND: The most common complication of oblique lumbar interbody fusion (OLIF) is endplate fracture/subsidence. The mechanics of endplate fracture in OLIF surgery are still unclear. The aim of the present study was to evaluate the biomechanical stability in patients undergoing OLIF surgery with stand-alone (SA) and bilateral pedicle screw fixation (BPSF) methods. METHODS: A finite element model of the L1-L5 spinal unit was established and validated. Using the validated model technique, L4-L5 functional surgical models corresponding to the SA and BPSF methods were created. Simulations using the models were performed to investigate OLIF surgery. A 500-N compression force was applied to the superior surface of the model to represent the upper body weight, and a 7.5-Nm moment was applied to simulate the 6 movement directions of the lumbar spinal model: flexion and extension, right and left lateral bending, and right and left axial rotation. Finite element models were developed to compare the biomechanics of the SA and BPSF groups. RESULTS: Compared with the range of motion of the intact lumbar model, that of the SA model was decreased by 79.6% in flexion, 54.5% in extension, 57.2% in lateral bending, and 50.0% in axial rotation. The BPSF model was decreased by 86.7% in flexion, 77.3% in extension, 76.2% in lateral bending, and 75.0% in axial rotation. Compared with the BPSF model, the maximum stresses of the L4 inferior endplate and L5 superior endplate were greatly increased in the SA model. The L4 inferior endplate stress was increased to 49.7 MPa in extension, and the L5 superior endplate stress was increased to 47.7 MPa in flexion, close to the yield stress of the lamellar bone (60 MPa). CONCLUSIONS: OLIF surgery with BPSF could reduce the maximum stresses on the endplate, which might reduce the incidence of cage subsidence. OLIF surgery with the SA method produced more stress compared with BPSF, especially in extension and flexion, which might be a potential risk factor for cage subsidence.

Clinical Investigation of the Association of Opening Size with Sagittal Canal Diameter Based on Single-Door Cervical Laminoplasty.

BACKGROUND Many clinical studies have assessed the association of laminoplasty opening size (LOS) with sagittal canal diameter (SCD) based on single-door cervical laminoplasty (SDCL). Nevertheless, the "worn-off" lamina extracted in SDCL was neglected in these reports. We aimed to develop a simple mathematical model to analyze the relationship between the effective LOS and SCD, taking into consideration the worn-off lamina. MATERIAL AND METHODS A total of 106 patients treated by SDCL at our hospital were included in this study. Pre-operative and post-operative SCDs were assessed using a picture archiving and communication system (PACS) based on computed tomography scans. Mini-plate sizes as well as drill bit diameters were recorded in detail in order to determine the effective LOS for each vertebral lamina involved. RESULTS SCD in all patients was increased significantly after SDCL (P<0.01). A linear correlation was found between effective LOS and the post-operative SCD increment from C3 to C7 (R²>0.933, P<0.001). The 12 mm mini-plate was most often used in SDCL, accounting for 64.45% of all cases, whereas 10 mm and 16 mm mini-plates were the least used, accounting for 3.85% and 3.00%, respectively. CONCLUSIONS There is a strong linear correlation between effective LOS and the post-operative SCD increment. The SCD was increased by about 0.5 mm per mm increase in effective LOS. Thus, post-operative SCD could be precisely calculated and predicted, enabling the selection of optimal mini-plate prior to SDCL.

A retrospective cross-sectional survey of non-specific lower back pain among a cohort of Chinese army soldiers.

RESEARCH BACKGROUND: Nonspecific lower back pain (LBP) has been a major public health problem in western countries since the second half of the 20 t h century. The trend has expanded to non-western countries, and LBP is currently a significant cause of disability in the working population. OBJECTIVE: To investigate the prevalence of nonspecific lower back pain (LBP) and its risk factors among soldiers in the Chinese army. METHODS: A total of 2876 Chinese army soldiers were requested to complete a self-administered questionnaire on demographic, anthropometric factors, and their non-specific LBP symptoms. The LBP evaluation and risk factor analysis were based on the self-questionnaire survey. RESULTS: The prevalence of non-specific LBP with physical state, one-child family, educational status, resident location and ethnicity were not associated (P > 0.05); while smoking, LBP history, LBP family history, nightmare frequency, sleep quality, and self-perceived fitness had significant effects on LBP (P < 0.05, Table 2). Multivariate logistic regression analysis showed that smoking (OR = 2.153,95% CI = 1.045-4.433), History of LBP (OR = 2.503,95% CI = 1.580-3.966), LBP family history (OR = 1.615,95%CI = 1.015-2.572), nightmare frequency (OR = 3.386, 95% CI = 2.047-5.603), sleep quality (OR = 2.391, 95% CI = 1.085-5.269) and self-perceived fitness (OR = 1.93,95%CI = 1.045-3.765) had significant effects on LBP (P < 0.05)) (Table 3). CONCLUSIONS: Smoking, history of LBP, LBP family history, nightmare frequency, sleep quality, self-perceived fitness were important factors in the occurrence and persistence of LBP.

Allogeneic mRNA-based electrotransfection of autologous dendritic cells and specific antitumor effects against osteosarcoma in rats.

Vaccination with dendritic cells (DCs) transfected with tumor-derived mRNA antigen has emerged as a promising strategy for generating protective immunity in mammals. However, the integration of allogeneic osteosarcoma mRNA and autologous DCs has not been fully examined. This study was designed to investigate the antitumor effects of tumor vaccine produced by autologous DCs transfected of allogeneic osteosarcoma mRNA through electroporation in tumor-bearing rats model. In the present study, extraction of Wistar rat tumor mRNA was performed as a two-step procedure. First, total RNA was extracted by use of Trizol; then, mRNA purification was performed by use of polyT-coated magnetic beads. Then, we transfected the allogeneic-derived tumor mRNA to Sprague-Dawley (SD) rat bone marrow-derived DCs through electroporation. The tumor vaccine was applied to tumor-bearing rats model, and the specific antitumor effects of the tumor vaccine were observed. The immunization using autologous DCs electrotransfected with allogeneic osteosarcoma total RNA induced specific CTL responses, which were statistically significant (P < 0.05), and the cytotoxic activity was confirmed in cold target inhibition assays and using mAbs blocking MHC class I molecules. In in vivo experiments, 70 % of the rats immunized with allogeneic osteosarcoma RNA transfected to DCs were typically able to reject tumor challenge and remained tumor-free. Vaccinated survivors developed long immunological memory and were able to reject a subsequent rechallenge with the same tumor cells but not a syngeneic unrelated tumor line. In the present study, we demonstrated that allogeneic tumor mRNA isolated from rat osteosarcoma cell line could be applied to produce tumor vaccine inducing specific antitumor effects, especially in DC-based immunotherapy strategy. This study also provides the foundations for an effective and broadly applicable treatment to a wide range of cancer indications for which tumor-associated antigens have not been identified.

Specific microRNA expression during chondrogenesis of human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) have the capacity to self-renew and differentiate into multiple cell types, but little is known about the precise mechanism of this procedure. Recent studies show that a group of short noncoding RNAs called microRNAs (miRNAs) play a key role in this procedure. However, little work has been done to determine the miRNAs which specifically regulate the differentiation of MSCs. In this study, we cultured human MSCs and chondrogenic differentiation MSCs of 3 donors, and investigated the miRNA expression profiles of MSCs and chondrogenic differentiated MSCs from 2 donors by using miRNA microarrays. We found 5 miRNAs were significantly overexpressed in chondrogenic differentiated MSCs in each sample, and 4 were further confirmed by real-time RT-PCR assay in the sample from the third independent donor. We also predicted the confirmed miRNAs corresponding to putative target genes by online software. The results indicated that the overexpressed miRNAs in chondrogenic differentiated MSCs may play a role in the procedure of MSC chondrogenesis, which offers us guidance for further studies.