RNA delivery by extracellular vesicles in mammalian cells and its applications.

The term 'extracellular vesicles' refers to a heterogeneous population of vesicular bodies of cellular origin that derive either from the endosomal compartment (exosomes) or as a result of shedding from the plasma membrane (microvesicles, oncosomes and apoptotic bodies). Extracellular vesicles carry a variety of cargo, including RNAs, proteins, lipids and DNA, which can be taken up by other cells, both in the direct vicinity of the source cell and at distant sites in the body via biofluids, and elicit a variety of phenotypic responses. Owing to their unique biology and roles in cell-cell communication, extracellular vesicles have attracted strong interest, which is further enhanced by their potential clinical utility. Because extracellular vesicles derive their cargo from the contents of the cells that produce them, they are attractive sources of biomarkers for a variety of diseases. Furthermore, studies demonstrating phenotypic effects of specific extracellular vesicle-associated cargo on target cells have stoked interest in extracellular vesicles as therapeutic vehicles. There is particularly strong evidence that the RNA cargo of extracellular vesicles can alter recipient cell gene expression and function. During the past decade, extracellular vesicles and their RNA cargo have become better defined, but many aspects of extracellular vesicle biology remain to be elucidated. These include selective cargo loading resulting in substantial differences between the composition of extracellular vesicles and source cells; heterogeneity in extracellular vesicle size and composition; and undefined mechanisms for the uptake of extracellular vesicles into recipient cells and the fates of their cargo. Further progress in unravelling the basic mechanisms of extracellular vesicle biogenesis, transport, and cargo delivery and function is needed for successful clinical implementation. This Review focuses on the current state of knowledge pertaining to packaging, transport and function of RNAs in extracellular vesicles and outlines the progress made thus far towards their clinical applications

Modelling the impact of afforestation on average annual streamflow in the Loess Plateau, China

To prevent severe soil erosion and to ensure sustainable development, the Chinese Central Government mandated in 1999 that forest cover would be significantly increased in the Loess Plateau, China. It is important to assess the subsequent impact on streamflow and its spatial distribution in the region. The water balance model of Zhang et at. (2001) was used in this study, and the results showed that the model was able to accurately Simulate average annual evapotranspiration (ET), but not average annual streamflow when compared with streamflow measurements from 38 hydrologic stations in the coarse sandy hilly catchments (CSHC) in the Loess Plateau. The model was then calibrated using the measured streamflow, and the index of agreement increased from 0.21 to 0.63, the relative error and root mean square error decreased from 42.7 and 17.2 to 18.0% and 7.9 mm, respectively. Hierarchical cluster analysis and stepwise regression were employed to regionalize the optimized model parameter and relate it to the dryness index and forest cover. Once calibrated, the water balance model was used to assess the impacts of two plantation scenarios on streamflow. The two plantation scenarios assume nearly 5.8 and 10.1% of the study area can be planted with trees. It was predicted that streamflow from the region will decrease by 5.5 and 9.2% under the two plantation scenarios. The rate of streamflow reduction decreased from southeast to northwest mainly due to decreasing precipitation. Copyright (c) 2007 John Wiley & Sons, Ltd