A conductive dual-network hydrogel composed of oxidized dextran and hyaluronic-hydrazide as BDNF delivery systems for potential spinal cord injury repair.

Spinal cord injury (SCI) often causes neuronal death and axonal degeneration. In this study, we report a new strategy for preparing injectable and conductive polysaccharides-based hydrogels that could sustainably deliver brain-derived neurotrophic factor (BDNF) for SCI repair. We used poly(lactic-co-glycolic acid) (PLGA) as a carrier to encapsulate BDNF. The resulting microspheres were then modified with tannic acid (TA). The polysaccharides-based hydrogel composed of oxidized dextran (Dex) and hyaluronic acid-hydrazide (HA) was mixed with TA-modified microspheres to form the ultimate BDNF@TA-PLGA/Dex-HA hydrogel. Our results showed that the hydrogel had properties similar to natural spinal cords. Specifically, the hydrogel had soft mechanical properties and high electrical conductivity. The cross-sectional morphology of the hydrogel exhibited a continuous and porous structure. The swelling and degradation behaviors of the Dex-HA hydrogel in vitro indicated the incorporation of TA into hydrogel matrix could improve the stability of the hydrogel matrix as well as extend the release time of BDNF from the matrix. Furthermore, results from immunostaining and real-time PCR demonstrated that BDNF@TA-PLGA/Dex-HA hydrogel could promote the differentiation of neural stem cells (NSCs) into neurons and inhibit astrocyte differentiation in vitro. These results show the great potential of this hydrogel as a biomimetic material in SCI regeneration.

Winter warming in Alaska accelerates lignin decomposition contributed by Proteobacteria.

BACKGROUND: In a warmer world, microbial decomposition of previously frozen organic carbon (C) is one of the most likely positive climate feedbacks of permafrost regions to the atmosphere. However, mechanistic understanding of microbial mediation on chemically recalcitrant C instability is limited; thus, it is crucial to identify and evaluate active decomposers of chemically recalcitrant C, which is essential for predicting C-cycle feedbacks and their relative strength of influence on climate change. Using stable isotope probing of the active layer of Arctic tundra soils after depleting soil labile C through a 975-day laboratory incubation, the identity of microbial decomposers of lignin and, their responses to warming were revealed. RESULTS: The ß-Proteobacteria genus Burkholderia accounted for 95.1% of total abundance of potential lignin decomposers. Consistently, Burkholderia isolated from our tundra soils could grow with lignin as the sole C source. A 2.2 °C increase of warming considerably increased total abundance and functional capacities of all potential lignin decomposers. In addition to Burkholderia, α-Proteobacteria capable of lignin decomposition (e.g. Bradyrhizobium and Methylobacterium genera) were stimulated by warming by 82-fold. Those community changes collectively doubled the priming effect, i.e., decomposition of existing C after fresh C input to soil. Consequently, warming aggravates soil C instability, as verified by microbially enabled climate-C modeling. CONCLUSIONS: Our findings are alarming, which demonstrate that accelerated C decomposition under warming conditions will make tundra soils a larger biospheric C source than anticipated. Video Abstract.

Gene-informed decomposition model predicts lower soil carbon loss due to persistent microbial adaptation to warming.

Soil microbial respiration is an important source of uncertainty in projecting future climate and carbon (C) cycle feedbacks. However, its feedbacks to climate warming and underlying microbial mechanisms are still poorly understood. Here we show that the temperature sensitivity of soil microbial respiration (Q10) in a temperate grassland ecosystem persistently decreases by 12.0 ± 3.7% across 7 years of warming. Also, the shifts of microbial communities play critical roles in regulating thermal adaptation of soil respiration. Incorporating microbial functional gene abundance data into a microbially-enabled ecosystem model significantly improves the modeling performance of soil microbial respiration by 5-19%, and reduces model parametric uncertainty by 55-71%. In addition, modeling analyses show that the microbial thermal adaptation can lead to considerably less heterotrophic respiration (11.6 ± 7.5%), and hence less soil C loss. If such microbially mediated dampening effects occur generally across different spatial and temporal scales, the potential positive feedback of soil microbial respiration in response to climate warming may be less than previously predicted.

Sirolimus conversion in liver transplant recipients with calcineurin inhibitor-induced complications: efficacy and safety.

OBJECTIVES: To evaluate the efficacy and safety of conversion from calcineurin inhibitors to sirolimus among liver transplant recipients with calcineurin inhibitor-induced complications. MATERIALS AND METHODS: After receiving liver transplants, 25 patients with calcineurin inhibitor-induced complications (22 renal dysfunction and 3 new-onset diabetes mellitus) were converted from sirolimus to tacrolimus. The serum creatinine, sirolimus trough level, liver function, acute rejection episodes, and drug-related adverse effects were monitored. RESULTS: The patients were followed for 12 to 50 months (median, 25 months). The renal function of the 22 patients with renal dysfunction improved after sirolimus conversion. The serum creatinine levels were significantly lower at 3 months after conversion versus before conversion (113.2 ± 21.8 µmol/L vs 163.2 ± 45.3 µmol/L; P < .05). At the end of the follow-up, the average serum creatinine level was 101.9 ± 23.4 µmol/L among the 20 living recipients. Diabetes also was under control in 3 diabetic recipients after the conversion. Four patients experienced episodes of acute rejection, and intravenous steroid bolus therapy was administered in 2 of them. No graft was lost because of acute rejection. The adverse effects of sirolimus included hyperlipidemia (7/25), anemia (8/25), and mouth ulcers (9/25). All these adverse effects were relieved after a short-term symptomatic therapy, and no patient was withdrawn from the conversion trial. CONCLUSIONS: Sirolimus monotherapy is effective and safe in liver transplant recipients. Conversion to sirolimus was associated with a sustained improvement in renal function and diabetes mellitus without an increased incidence of acute rejection episodes.