Endothelial progenitor cells give rise to pro-angiogenic smooth muscle-like progeny

Reciprocal plasticity exists between endothelial and mesenchymal lineages. For instance, mature endothelial cells adopt a smooth muscle-like phenotype through transforming growth factor beta-1 (TGF beta 1)-driven endothelial-to-mesenchymal transdifferentiation (EndMT). Peripheral blood contains circulating endothelial progenitor cells of which the endothelial colony-forming cells (ECFCs) harbour stem cell-like properties. Given the plasticity between endothelial and mesenchymal lineages and the stem cell-like properties of ECFCs, we hypothesized that ECFCs can give rise to smooth muscle-like progeny. ECFCs were stimulated with TGF beta 1, after which TGF beta signalling cascades and their downstream effects were investigated. Indeed, EndMT of ECFCs resulted in smooth muscle-like progeniture. TGF beta 1-driven EndMT is mediated by ALK5 kinase activity, increased downstream Smad2 signalling, and reduced protein levels of inhibitor of DNA-binding protein 3. ECFCs lost expression of endothelial markers and endothelial anti-thrombogenic function. Simultaneously, mesenchymal marker expression was gained, cytoskeletal rearrangements occurred, and cells acquired a contractile phenotype. Transdifferentiated ECFCs were phenotypically stable and self-sustaining and, importantly, showed fibroblast growth factor-2 and angiopoietin-1-mediated pro-angiogenic paracrine properties. Our study is the first to demonstrate that ECFCs can give rise to smooth muscle-like progeny, with potential therapeutic benefits. These findings further illustrate that ECFCs are highly plastic, which by itself has implications for therapeutical use

Establishing implantation uncertainties for focal brachytherapy with I-125 seeds for the treatment of localized prostate cancer.

Background. The efficacy of focal continuous low dose-rate brachytherapy (CLDR-BT) for prostate cancer requires that appropriate margins are applied to ensure robust target coverage. In this study we propose a method to establish such margins by emulating a focal treatment in patients treated with CLDR-BT to the entire gland. Material and methods. In 15 patients with localized prostate cancer, prostate volumes and dominant intra-prostatic lesions were delineated on pre-treatment magnetic resonance imaging (MRI). Delineations and MRI were registered to trans-rectal ultrasound images in the operating theater. The patients received CLDR-BT treatment to the total prostate volume. The implantation consisted of two parts: an experimental focal plan covering the dominant intra-prostatic lesion (F-GTV), followed by a plan containing additional seeds to achieve entire prostate coverage. Isodose surfaces were reconstructed using follow-up computed tomography (CT). The focal dose was emulated by reconstructing seeds from the focal plan only. The distance to agreement between planned and delivered isodose surfaces and F-GTV coverage was determined to calculate the margin required for robust treatment. Results. If patients had been treated only focally, the target volume would have been reduced from an average of 40.9 cm(3) for the entire prostate to 5.8 cm(3) for the focal plan. The D-90 for the F-GTV in the focal plan was 195 +/-. 60 Gy, the V-100 was 94% [range 71-100%]. The maximum distance (cd(95)) between the planned and delivered isodose contours was 0.48 cm. Conclusions. This study provides an estimate of 0.5 cm for the margin required for robust coverage of a focal target volume prior to actually implementing a focal treatment protoco

Endothelial-to-mesenchymal transition contributes to fibro-proliferative vascular disease and is modulated by fluid shear stress

Neointimal hyperplasia is a common feature of fibro-proliferative vascular disease and characterizes initial stages of atherosclerosis. Neointimal lesions mainly comprise smooth muscle-like cells. The presence of these lesions is related to local differences in shear stress. Neointimal cells may arise through migration and proliferation of smooth muscle cells from the media. However, a role for the endothelium as a source of smooth muscle-like cells has largely been disregarded. Here, we investigated the role of endothelial-to-mesenchymal transition (EndMT) in neointimal hyperplasia and atherogenesis, and studied its modulation by shear stress. In human atherosclerotic plaques and porcine aortic tissues, myo-endothelial cells were identified, suggestive for EndMT. Flow disturbance by thoracic-aortic constriction in mice similarly showed the presence of myo-endothelial cells specifically in regions exposed to disturbed flow. While uniform laminar shear stress (LSS) was found to inhibit EndMT, endothelial cells exposed to disturbed flow underwent EndMT, in vitro and in vivo, and showed atherogenic differentiation. Gain- and loss-of-function studies using a constitutive active mutant of MEK5 and short hairpins targeting ERK5 established a pivotal role for ERK5 signalling in the inhibition of EndMT. Together, these data suggest that EndMT contributes to neointimal hyperplasia and induces atherogenic differentiation of endothelial cells. Importantly, we uncovered that EndMT is modulated by shear stress in an ERK5-dependent manner. These findings provide new insights in the role of adverse endothelial plasticity in vascular disease and identify a novel atheroprotective mechanism of uniform LSS, namely inhibition of EndMT