Mechanical interactions of mesenchymal stem cells (MSC) with the environment play a significant role in controlling the diverse biological functions of these cells. Mechanical forces are transduced by integrins to the actin cytoskeleton that functions as a scaffold to switch mechanical signals into biochemical pathways. To explore the significance of cytoskeletal mechanisms in human MSC we modulated the actin cytoskeleton using the depolymerising drugs cytochalasin D (CytD) and latrunculin A (LatA), as well as the stabilizing drug jasplakinolide (Jasp) and examined the activation of the signalling molecules ERK and AKT during mechanical loading. All three drugs provoked significant changes in cell morphology and organisation of the cytoskeleton. Application of mechanical forces to β1-integrin receptors using magnetic beads without deformation of the cell shape induced a phosphorylation of ERK and AKT. Of the two drugs that inhibited the cytoskeletal polymerization, LatA completely blocked the activation of ERK and AKT due to mechanical forces, whereas CytD inhibited the activation of AKT but not of ERK. Activation of both signalling molecules by integrin loading was not affected due to cell treatment with the cytoskeleton stabilizing drug Jasp. To correlate the effects of the drugs on mechanically induced activation of AKT and ERK with parameters of MSC differentiation, we studied ALP activity as a marker for osteogenic differentiation and examined the uptake of fat droplets as marker for adipogenic differentiation in the presence of the drugs. All three drugs inhibited ALP activity of MSC in osteogenic differentiation medium. Adipogenic differentiation was enhanced by CytD and Jasp, but not by LatA. The results indicate that modulation of the cytoskeleton using perturbing drugs can differentially modify both mechanically induced signal transduction and MSC differentiation. In addition to activation of the signalling molecules ERK and AKT, other cytoskeletal mechanisms are involved in MSC differentiation.

Aims: Stem cell-based regenerative therapies for the treatment of ischemic myocardium are currently a subject of intensive investigation. A variety of cell populations have been demonstrated to be safe and to exert some positive effects in human Phase I and II clinical trials, however conclusive evidence of efficacy is still lacking. While the relevance of animal models for appropriate pre-clinical safety and efficacy testing with regard to application in Phase III studies continues to increase, concerns have been expressed regarding the validity of the mouse model to predict clinical results. Against the background that hundreds of preclinical studies have assessed the efficacy of numerous kinds of cell preparations - including pluripotent stem cells - for cardiac repair, we undertook a systematic re-evaluation of data from the mouse model, which initially paved the way for the first clinical trials in this field. Methods and Results: A systematic literature screen was performed to identify publications reporting results of cardiac stem cell therapies for the treatment of myocardial ischemia in the mouse model. Only peer-reviewed and placebo-controlled studies using magnet resonance imaging (MRI) for left ventricular ejection fraction (LVEF) assessment were included. Experimental data from 21 studies involving 583 animals demonstrate a significant improvement in LVEF of 8.59%+/- 2.36; p=.012 (95% CI, 3.7–13.8) compared with control animals. Conclusion: The mouse is a valid model to evaluate the efficacy of cell-based advanced therapies for the treatment of ischemic myocardial damage. Further studies are required to understand the mechanisms underlying stem cell based improvement of cardiac function after ischemia.

The objective of the present study was to analyse critically the quality of the reporting in 102 randomized trials from four leading urological journals from 1984 to 1989 on the basis of an evaluation system we have developed. This comprises 21 principal parameters selected in terms of their significance for the validity of the studies. These parameters were evaluated by two readers independently of each other as to whether they were specified, not specified, could not be evaluated or were not applicable. The study score of each paper resulted from the sum of all specified criteria. In the 102 studies, out of 21 criteria 69.1% and 69.8% (investigators A and B, respectively) were reported; 29.8% and 29.4%, respectively were not reported, 0.4% and 0.1%, respectively, could not be evaluated and 0.7% did not apply. Such important principal parameters as the sample size (6.9% and 7.8%, respectively), statistical power (11.8%), method of randomization (22.5% and 23.5%, respectively), patient blinding (30.4%), investigator blinding (33.3%), loss to follow-up (34.8% and 35.3%, respectively) and rate of discontinuation (36.0% and 37.7%, respectively) were mentioned least often. The study score of all investigations ranged from 20.5 (97.6%) to 9.0 (42.9%) points. Most (60/59% and 62/61%, respectively) attained values between 16 (76.2%) and 13 (61.9%). Accordingly, randomized trials in urological journals show similar deficits to those in internal medicine, surgery and intensive care medicine. A particular problem is that they concern the most important techniques for systematic reduction of inadvertent errors (bias), and thus doubt is cast upon the hardcore of controlled studies. If it is possible for many authors to mention individual criteria completely, this should also apply (and in particular) to the most critical parameters. In our opinion, the 21 criteria selected for an evaluation system constitute a practical compromise between the 3 and 38 criteria alternatively suggested by other authors. Moreover, use of a comprehensive check list should be the precondition for acceptance of papers for publication.