NGF release from thermo-responsive collagen-polyNIPAam polymer networks supports neuronal cell growth and differentiation

The role of meteorological factors in suicide mortality in Wuhu, a humid city along the Yangtze River in Eastern China

As the climate continues to change, suicide is becoming more frequent. In this study, absolute humidity (AH) was included for the first time and Wuhu, a typical subtropical city along the Yangtze River, was taken as the research object to explore the impact of suicide death risk on meteorological factors. The daily meteorological factors and suicide mortality data of Wuhu city from 2014 to 2020 were collected. Guided by structural equation model (SEM), a time series analysis method combining distributed lag nonlinear model (DLNM) and generalized additive model (GAM) was adopted. To investigate the correlation among different populations, we stratified age and gender at different meteorological levels. A total of 1259 suicide deaths were collected in Wuhu. The results indicated that exceedingly low and low levels of AH short-term exposure increased suicide mortality, with the maximum effect occurring at lag 14 for both levels of exposure, when the relative risk (RR) was 1.131 (95% CI: 1.030, 1.242) and 1.065 (95% CI: 1.006, 1.127), respectively. Exposure to exceedingly high and exceedingly low levels of temperature mean (T mean) also increased suicide mortality, with maximum RR values of 1.132 (lag 14, 95% CI: 1.015, 1.263) and 1.203 (lag 0, 95% CI: 1.079, 1.340), sequentially. As for diurnal temperature range (DTR), low-level exposure decreased the risk of suicide, while high-level exposure increased this risk, with RR values of 0.955 (lag 0, 95% CI: 0.920, 0.991, minimum) and 1.060 (lag 0, 95% CI: 1.018, 1.104, maximum), sequentially. Stratified analysis showed that AH and DTR increased the suicide death risk in male and elderly people, while the risk effect of T mean have no effect on young people only. In summary, male and elderly people appear to be more vulnerable to adverse weather effects.

Ambient temperature, sunlight duration, and suicide: A systematic review and meta-analysis

BACKGROUND

The relationship between sunlight hours, temperature, and suicide has been investigated in many previous studies, but with inconsistent findings. We conducted this meta-analysis aiming at providing clear evidence about whether sunlight hours and temperature can affect the risk of suicide.

METHODS

Relevant literature published before 7 Jul 2018 was searched in three electronic database of PubMed, Web of science and Cochrane. Between-study heterogeneity in the effect estimates were examined by study design (i.e., exposure time resolution, temperature measure and suicide classification) and population vulnerability (i.e., sex, national income level, climate zone and study location).

RESULTS

Regarding temperature-suicide association, we identified 14 studies that provided 23 effect estimates for meta-analysis. Our random-effects model showed that each 1 °C increase in temperature was significantly associated with a 1% increase in the incidence of suicide (Incidence Rate Radio (IRR) = 1.01; 95%CI = 1.00-1.02; p < 0.05). As for sunlight duration and suicide, 11 effect estimates from 4 studies were pooled using a fixed-effects model. Significant association between sunlight duration (per 1 h increase) and the risk of suicide was not observed, and the pooled IRR was 1.00 (95%CI = 0.99-1.01; p > 0.05). There was significant heterogeneity between previous studies' effect estimates, and significantly lower heterogeneity was noted for the female group, for studies that did analyses at daily scale, and for studies using mean temperature as the exposure indicator.

CONCLUSION

Our findings suggest a significant and positive association between temperature rises and incidence of suicide, and a non-significant association between sunlight duration and incidence of suicide. Populations living in tropical and temperate zones or at middle-income level may be particularly vulnerable to temperature increase.

Socio-environmental drivers and suicide in Australia: Bayesian spatial analysis

BACKGROUND

The impact of socio-environmental factors on suicide has been examined in many studies. Few of them, however, have explored these associations from a spatial perspective, especially in assessing the association between meteorological factors and suicide. This study examined the association of meteorological and socio-demographic factors with suicide across small areas over different time periods.

METHODS

Suicide, population and socio-demographic data (e.g., population of Aboriginal and Torres Strait Islanders (ATSI), and unemployment rate (UNE) at the Local Government Area (LGA) level were obtained from the Australian Bureau of Statistics for the period of 1986 to 2005. Information on meteorological factors (rainfall, temperature and humidity) was supplied by Australian Bureau of Meteorology. A Bayesian Conditional Autoregressive (CAR) Model was applied to explore the association of socio-demographic and meteorological factors with suicide across LGAs.

RESULTS

In Model I (socio-demographic factors), proportion of ATSI and UNE were positively associated with suicide from 1996 to 2000 (Relative Risk (RR)ATSI = 1.0107, 95% Credible Interval (CI): 1.0062-1.0151; RRUNE = 1.0187, 95% CI: 1.0060-1.0315), and from 2001 to 2005 (RRATSI = 1.0126, 95% CI: 1.0076-1.0176; RRUNE = 1.0198, 95% CI: 1.0041-1.0354). Socio-Economic Index for Area (SEIFA) and IND, however, had negative associations with suicide between 1986 and 1990 (RRSEIFA = 0.9983, 95% CI: 0.9971-0.9995; RRATSI = 0.9914, 95% CI: 0.9848-0.9980). Model II (meteorological factors): a 1°C higher yearly mean temperature across LGAs increased the suicide rate by an average by 2.27% (95% CI: 0.73%, 3.82%) in 1996-2000, and 3.24% (95% CI: 1.26%, 5.21%) in 2001-2005. The associations between socio-demographic factors and suicide in Model III (socio-demographic and meteorological factors) were similar to those in Model I; but, there is no substantive association between climate and suicide in Model III.

CONCLUSIONS

Proportion of Aboriginal and Torres Strait Islanders, unemployment and temperature appeared to be statistically associated with of suicide incidence across LGAs among all selected variables, especially in recent years. The results indicated that socio-demographic factors played more important roles than meteorological factors in the spatial pattern of suicide incidence.

Assembly of protein-based hollow spheres encapsulating a therapeutic factor

Neurotrophins, as important regulators of neural development, function, and survival, have a therapeutic potential to repair damaged neurons. However, a controlled delivery of therapeutic molecules to injured tissue remains one of the greatest challenges facing the translation of novel drug therapeutics field. This study presents the development of an innovative protein-protein delivery technology of nerve growth factor (NGF) by an electrostatically assembled protein-based (collagen) reservoir system that can be directly injected into the injury site and provide long-term release of the therapeutic. A protein-based biomimetic hollow reservoir system was fabricated using a template method. The capability of neurotrophins to localize in these reservoir systems was confirmed by confocal images of fluorescently labeled collagen and NGF. In addition, high loading efficiency of the reservoir system was proven using ELISA. By comparing release profile from microspheres with varying cross-linking, highly cross-linked collagen spheres were chosen as they have the slowest release rate. Finally, biological activity of released NGF was assessed using rat pheochromocytoma (PC12) cell line and primary rat dorsal root ganglion (DRG) cell bioassay where cell treatment with NGF-loaded reservoirs induced significant neuronal outgrowth, similar to that seen in NGF treated controls. Data presented here highlights the potential of a high capacity reservoir-growth factor technology as a promising therapeutic treatment for neuroregenerative applications and other neurodegenerative diseases.

Remote and local control of stimuli responsive materials for therapeutic applications

Materials offering the ability to change their characteristics in response to presented stimuli have demonstrated application in the biomedical arena, allowing control over drug delivery, protein adsorption and cell attachment to materials. Many of these smart systems are reversible, giving rise to finer control over material properties and biological interaction, useful for various therapeutic treatment strategies. Many smart materials intended for biological interaction are based around pH or thermo-responsive materials, although the use of magnetic materials, particularly in neural regeneration, has increased over the past decade. This review draws together a background of literature describing the design principles and mechanisms of smart materials. Discussion centres on recent literature regarding pH-, thermo-, magnetic and dual responsive materials, and their current applications for the treatment of neural tissue.

Thick collagen-based 3D matrices including growth factors to induce neurite outgrowth

Designing synthetic microenvironments for cellular investigations is a very active area of research at the crossroads of cell biology and materials science. The present work describes the design and functionalization of a three-dimensional (3D) culture support dedicated to the study of neurite outgrowth from neural cells. It is based on a dense self-assembled collagen matrix stabilized by 100-nm-wide interconnected native fibrils without chemical crosslinking. The matrices were made suitable for cell manipulation and direct observation in confocal microscopy by anchoring them to traditional glass supports with a calibrated thickness of ∼50μm. The matrix composition can be readily adapted to specific neural cell types, notably by incorporating appropriate neurotrophic growth factors. Both PC-12 and SH-SY5Y lines respond to growth factors (nerve growth factor and brain-derived neurotrophic factor, respectively) impregnated and slowly released from the support. Significant neurite outgrowth is reported for a large proportion of cells, up to 66% for PC12 and 49% for SH-SY5Y. It is also shown that both growth factors can be chemically conjugated (EDC/NHS) throughout the matrix and yield similar proportions of cells with longer neurites (61% and 52%, respectively). Finally, neurite outgrowth was observed over several tens of microns within the 3D matrix, with both diffusing and immobilized growth factors.

Rendering Rayon Fibres Antimicrobial and Thermal-Responsive via Layer-by-Layer Self-Assembly of Functional Polymers

A thermal-responsive polymer was prepared by partially acetalyzing poly(vinyl alcohol) (PVA). The completely reversible polymer aggregation and dissolution occur above and below a low critical solution temperature (LCST) for the aqueous solution of the modified PVA. The partially acetalized PVA (APVA) with higher molecular weight and higher degree of acetalysis exhibited a lower LCST transition and was used as an anionic polymer for polymer complexation. Water-soluble polymer, cationic polyhexamethylene guanidine hydrochloride (CPHGH) with antimicrobial property, was also prepared. In conjunction with APVA, CPHGH created the unique antimicrobial polymer multilayers on the surfaces of rayon fibres via layer by layer (LbL) assembly. AFM images revealed that the particles generated by multilayers became larger after the material was treated at 60°C; while the roughness of the surfaces was increased as the layer number increased and then decreased. Moreover, antimicrobial tests also demonstrated that the rayon fiber assembled with (CPHGH/APVA) multilayers exhibited higher antimicrobial activity against E. coli and s. aureus.

Stromal cell-derived factor-1 (SDF-1): homing factor for engineered regenerative medicine

INTRODUCTION

Stromal cell-derived factor-1α (SDF-1) is a chemokine that plays a major role in cell trafficking and homing of CD34(+) stem cells. Studies employing SDF-1/CXCR4 have demonstrated its therapeutic potential in tissue engineering. During injury, cells from the injured organ highly express SDF-1, which causes an elevation of localized SDF-1 levels. This leads to recruitment and retention of circulating CD34(+) progenitor cells at the injury site via chemotactic attraction toward a gradient of SDF-1. The general approaches for SDF-1 introduction in tissue engineering are direct protein incorporation into scaffolds and transplantation of SDF-1-overexpressing cells and both methods are successful in improving the regeneration of the damaged tissue/organ.

AREAS COVERED

The mechanisms of SDF-1-mediated homing via CXCR4 receptor and the success of SDF-1-based medical applications in mesenchymal stem cell (MSC) homing as well as areas such as therapeutic angiogenesis, wound healing and neuronal and liver regeneration.

EXPERT OPINION

Current SDF-1 delivery designs and platforms hold much room for improvement. Regardless of the different techniques of SDF-1 introduction, they have proved to be effective in recruitment of various stem/progenitor cells. The pursuit of SDF-1-related regenerative medicine has already begun. It is thus conceivable that its usage in the clinical setting will be a reality in the near future.

Biomimetic smart interface materials for biological applications

Controlling the surface chemical and physical properties of materials and modulating the interfacial behaviors of biological entities, e.g., cells and biomolecules, are central tasks in the study of biomaterials. In this context, smart polymer interface materials have recently attracted much interest in biorelated applications and have broad prospects due to the excellent controllability of their surface properties by external stimuli. Among such materials, poly(N-isopropylacrylamide) and its copolymer films are especially attractive due to their reversible hydrogen-bonding-mediated reversible phase transition, which mimics natural biological processes. This platform is promising for tuning surface properties or to introduce novel biofunctionalities via copolymerization with various functional units and/or combination with other materials. Important progress in this field in recent years is highlighted.