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

MR fluoroscopy in vascular and cardiac interventions (review)

Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image–guided surgeries that offer improved patient management and cost effectiveness

Temperature and calcium ions affect aggregation of mesenchymal stem cells in phosphate buffered saline

Bone marrow-derived mesenchymal stem cells (MSC) are being extensively studied as potential therapeutic agents for various diseases and have demonstrated tremendous promise to date. To reduce immunological and inflammatory reaction upon delivery of MSC in situ, the cells are often suspended in protein-free and nutrient-poor buffered saline solution at high titers and kept on ice (0 °C) until completion of the transplantation procedure. This study investigated the effects of suspending MSC (5 × 106 cells/mL) in phosphate buffered saline (PBS) with and without calcium, over a time course of 90 and 180 min, at temperatures of 0 and 37 °C. The results at 0 °C showed a small but significant decrease in cell viability within calcium-free PBS after 180 min, whereas no significant changes in cell viability were observed with PBS containing calcium. Additionally, it was observed that significant aggregation of MSC into cellular clumps occurred when incubated in PBS at 0 °C, with a higher degree of aggregation occurring under calcium-free conditions. By contrast at 37 °C, there was a more pronounced decrease in cell viability after 90 and 180 min, but lesser aggregation of MSC both in the presence and absence of calcium. The aggregation of MSC into cellular clumps could pose an embolic hazard if delivered into the arterial vasculature in cardiac applications, can clog-up injection or infusion catheters utilized for cell delivery during surgery, and can also possibly reduce the overall efficacy of transplantation therapy