Background information. Although MSCs (mesenchymal stem cells) and fibroblasts have been well studied, differences between these two cell types are not fully understood. We therefore comparatively analysed antigen and gene profiles, colony-forming ability and differentiation potential of four human cell types in vitro: commercially available skin-derived fibroblasts [hSDFs (human skin-derived fibroblasts)], adipose tissue-derived stem cells [hASCs (human adipose tissue-derived stem cells)], embryonic lung fibroblasts (WI38) and dermal microvascular endothelial cells [hECs (human dermal microvascular endothelial cells)].Results. hSDFs, hASCs and WI38 exhibited a similar spindle-like morphology and expressed same antigen profiles: positive for MSC markers (CD44, CD73 and CD105) and fibroblastic markers [collagen I, HSP47 (heat shock protein 47), vimentin, FSP (fibroblast surface protein) and αSMA (α smooth muscle actin)], and negative for endothelial cell marker CD31 and haemopoietic lineage markers (CD14 and CD45). We further analysed 90 stem cell-associated gene expressions by performing real-time PCR and found a more similar gene expression pattern between hASCs and hSDFs than between hSDFs and WI38. The expression of embryonic stem cell markers [OCT4, KLF4, NANOG, LIN28, FGF4 (fibroblast growth factor 4) and REST] in hASCs and hSDFs was observed to differ more than 2.5-fold as compared with WI38. In addition, hSDFs and hASCs were able to form colonies and differentiate into adipocytes, osteoblasts and chondrocytes in vitro, but not WI38. Moreover, single cell-derived hSDFs and hASCs obtained by clonal expansion were able to differentiate into adipocytes and osteoblasts. However, CD31 positive hECs did not show differentiation potential.Conclusions. These findings suggest that (i) so-called commercially available fibroblast preparations from skin (hSDFs) consist of a significant number of cells with differentiation potential apart from terminally differentiated fibroblasts; (ii) colony-forming capacity and differentiation potential are specific important properties that discriminate MSCs from fibroblasts (WI38), while conventional stem cell properties such as plastic adherence and the expression of CD44, CD90 and CD105 are unspecific for stem cells.

This is the first study to systematically compare the effects of fhADCs and hASCs on myocardial regeneration. Both cell types engraft into infarcted myocardium, survive, and improve myocardial function, suggesting that fhADCs, like hASCs, are a promising alternative cell source for myocardial repair after MI.

Droplet-based programmable processors promise to offer solutions to a wide range of applications in which chemical and biological analysis and/or small-scale synthesis are required, suggesting they will become the microfluidic equivalents of microprocessors by offering off-the-shelf solutions for almost any fluid based analysis or small scale synthesis problem. A general purpose droplet processor should be able to manipulate droplets of different compositions (including those that are electrically conductive or insulating and those of polar or non-polar nature), to control reagent titrations accurately, and to remain free of contamination and carry over on its reaction surfaces. In this article we discuss the application of dielectrophoresis to droplet based processors and demonstrate that it can provide the means for accurately titrating, moving and mixing polar or non-polar droplets whether they are electrically conductive or not. DEP does not require contact with control surfaces and several strategies for minimizing surface contact are presented. As an example of a DEP actuated general purpose droplet processor, we show an embodiment based on a scaleable CMOS architecture that uses DEP manipulation on a 32 x 32 electrode array having built-in control and switching circuitry. Lastly, we demonstrate the concept of a general-purpose programming environment that facilitates droplet software development for any type of droplet processor.

We have applied the microfluidic cell separation method of dielectrophoretic field-flow fractionation (DEP-FFF) to the enrichment of a putative stem cell population from an enzyme-digested adipose tissue derived cell suspension. A DEP-FFF separator device was constructed using a novel microfluidic-microelectronic hybrid flex-circuit fabrication approach that is scaleable and anticipates future low-cost volume manufacturing. We report the separation of a nucleated cell fraction from cell debris and the bulk of the erythrocyte population, with the relatively rare (<2% starting concentration) NG2-positive cell population (pericytes and/or putative progenitor cells) being enriched up to 14-fold. This work demonstrates a potential clinical application for DEP-FFF and further establishes the utility of the method for achieving label-free fractionation of cell subpopulations.

The metabolic syndrome is a constellation of clinical risk factors comprising atherogenic dyslipidemia (low high-density lipoprotein and high triglycerides levels), elevated blood pressure, elevated plasma glucose, a prothrombotic state, and a proinflammatory state accompanied by an increased risk for cardiovascular disease and type 2 diabetes mellitus. The adipose tissue of obese humans contains increased numbers of macrophages, and once activated, these macrophages are responsible for the expression of most of the tissue's tumor necrosis factor (TNF)-α and interleukin (IL)-6. Chronic inflammation associated with visceral obesity induces altered lipoprotein metabolism and insulin resistance in the liver. Adipocytes secrete a variety of hormones, cytokines, growth factors, and other bioactive substances, conceptualized as adipocytokines, including plasminogen activator inhibitor 1 (PAI-1), TNF-α, leptin, and adiponectin. The dysregulation of these adipokines contributes to the pathogenesis of obesity. Adipose tissue-resident macrophages and adipocytes in the adipose tissue combined with the consequences of hyperglycemia, altered lipoproteins, and hyperinsulinemia in the vasculature and within organ microcirculation lead to dysfunctional endothelia and a proinflammatory state. Metabolic syndrome thus represents a combination of synergistic vascular pathologies that lead to an accelerated atherogenic state that compromises the ability of the patient to satisfactorily respond to humoral, cellular, and mechanical stresses.