Extracellular Matrix Aggregates from Differentiating Embryoid Bodies as a Scaffold to Support ESC Proliferation and Differentiation

Embryonic stem cells (ESCs) have emerged as potential cell sources for tissue engineering and regeneration owing to its virtually unlimited replicative capacity and the potential to differentiate into a variety of cell types. Current differentiation strategies primarily involve various growth factor/inducer/repressor concoctions with less emphasis on the substrate. Developing biomaterials to promote stem cell proliferation and differentiation could aid in the realization of this goal. Extracellular matrix (ECM) components are important physiological regulators, and can provide cues to direct ESC expansion and differentiation. ECM undergoes constant remodeling with surrounding cells to accommodate specific developmental event. In this study, using ESC derived aggregates called embryoid bodies (EB) as a model, we characterized the biological nature of ECM in EB after exposure to different treatments: spontaneously differentiated and retinoic acid treated (denoted as SPT and RA, respectively). Next, we extracted this treatment-specific ECM by detergent decellularization methods (Triton X-100, DOC and SDS are compared). The resulting EB ECM scaffolds were seeded with undifferentiated ESCs using a novel cell seeding strategy, and the behavior of ESCs was studied. Our results showed that the optimized protocol efficiently removes cells while retaining crucial ECM and biochemical components. Decellularized ECM from SPT EB gave rise to a more favorable microenvironment for promoting ESC attachment, proliferation, and early differentiation, compared to native EB and decellularized ECM from RA EB. These findings suggest that various treatment conditions allow the formulation of unique ESC-ECM derived scaffolds to enhance ESC bioactivities, including proliferation and differentiation for tissue regeneration applications. © 2013 Goh et al

The cycling of pollutants in nonurban forested environments

Forests are complex ecosystems which respond to external inputs of pollutants in a variety of ways. Quantifying changes in the storage of pollutants within ecosystem pools and the biogeochemical fluxes between them provides a means of calculating the overall pollutant balance of a forest ecosystem as an indicator of its sustainability and health. This chapter focuses on pollutant cycling in nonurban forest ecosystems with specific attention on quantification of external inputs, pollutant fluxes and pools within forests and exports to adjacent systems (Fig. 34.1). Selected case studies are used to exemplify the approach and illustrate the importance of location, forest type, management practices such as harvesting and soil conditions. Direct pollutant impacts on forest ecosystem functioning, the effects of intensified biomass utilization, and interactions between climate and pollutant cycling are also discusse