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IntroductionThe vascular system is a bipolar complex network of arteries that transport oxygen-rich blood to all tissues and veins that bring oxygendeprived blood back to the heart. 1 Because of this bipolar set-up, arteries and veins feature anatomic and physiological differences. Unlike venous endothelium, arterial endothelium is surrounded by several layers of smooth muscle cells (SMCs), separated by elastic laminae, and embedded in a thick layer of fibrillar collagen. 2 Moreover, both vessel types have a differential susceptibility to atherosclerotic disease, possibly due to exposure to different levels of shear stress. Arterial and venous endothelial cells (ECs) also have a distinct molecular signature, and such molecular specification occurs before the onset of blood flow. 3 Indeed, arteriovenous (AV) specification of ECs is accomplished early in development and is associated with the expression of a specific complement of factors: venous endothelium is characterized by the expression of EphB4, 4 Lefty-1, 5 Lefty-2, 5 COUP-TFII, 6 and MYO1-␤, 5 and arterial ECs express high levels of Notch 1 and 4, 7 Dll-4, 8 EphrinB1 and EphrinB2, 4 Jagged-1 and -2, 7 connexin-40, and Hey-2 (gridlock zebrafish ortholog). 9,10 Studies in Xenopus, zebrafish, and mice have revealed that, besides blood flow, 11 vessel-intrinsic cues and-later in development-signals from outside the vasculature 12,13 are implicated in defining arterial or venous fate such as members of the TGF-␤ pathway, 14,15 VEGF isoforms,13,[16][17][18]17 angiopoietins, 19 the Notch pathway, 7,9,20-22 the patched pathway, 20 and COUP-TFII, a member of the orphan nuclear receptor superfamily. 6 Although it has been shown that some of these pathways are well conserved from zebrafish to mouse, less information is available on whether they have a similar role in humans. Because these molecular differences between arterial and venous ECs exist independently of blood flow and some of these factors work in an EC-intrinsic way, 2 it should be possible to manipulate some or all of these to endow ECs with an arterial or venous fate. Consistent with this notion, recent studies have suggested that arterial markers can be induced in primary mature ECs. 5,13,21,23,24 Many different stem cell populations, including bone marrow (BM) mononuclear cells, AC133 ϩ endothelial progenitor cells, and embryonic stem cells have the potential to differentiate in vitro and in vivo into mature and functional ECs. 4,[25][26][27][28] We have recently described another stem cell population, multipotent adult progenitor cells (MAPCs), that differentiates into most somatic cell types, including functional ECs, in vitro and in vivo. [29][30][31][32][33] The question of whether and how these stem cells can be coaxed into arterial or venous ECs has thus far not been addressed. In this study, we analyzed the in vitro and in vivo arterial and venous endothelial differentiation of human MAPCs (hMAPCs) and hAC133 ϩ cells. Materials and methodsAdditional and extended descriptions of methods are inc...

The aim of the study was to determine the long-term effect of transplantation of adipose-derived stromal cells (ADSCs) in a preclinical model of ischemia/reperfusion (I/R). I/R was induced in 28 Goettingen minipigs by 120 min of coronary artery occlusion followed by reperfusion. Nine days later, surviving animals were allocated to receive transendocardial injection of a mean of 213.6 ± 41.78 million green fluorescent protein (GFP)-expressing ADSCs (n = 7) or culture medium as control (n = 9). Heart function, cell engraftment, and histological analysis were performed 3 months after transplantation. Transplantation of ADSCs induced a statistically significant long-lasting (3 months) improvement in cardiac function and geometry in comparison with control animals. Functional improvement was associated with an increase in angiogenesis and vasculogenesis and a positive effect on heart remodeling with a decrease in fibrosis and cardiac hypertrophy in animals treated with ADSCs. Despite the lack of cell engraftment after 3 months, ADSC transplantation induced changes in the ratio between MMP/TIMP. Our results indicate that transplantation of ADSCs, despite the lack of long-term significant cell engraftment, increases vessel density and prevents adverse remodeling in a clinically relevant model of myocardial infarction, strongly suggesting a paracrine-mediated effect. ADSCs thus constitute an attractive candidate for the treatment of myocardial infarction.

The development of biomaterials for myocardial tissue engineering requires a careful assessment of their performance with regards to functionality and biocompatibility, including the immune response. Poly (3-hydroxybutyrate) (PHB), poly(e-caprolactone) (PCL), silk, poly-lactic acid (PLA), and polyamide (PA) scaffolds were generated by electrospinning, and cell compatibility in vitro, and immune response and cardiac function in vitro and in vivo were compared with a noncrosslinked collagen membrane (Col) control material. Results showed that cell adhesion and growth of mesenchymal stem cells, cardiomyocytes, and cardiac fibroblasts in vitro was dependent on the polymer substrate, with PHB and PCL polymers permitting the greatest adhesion/growth of cells. Additionally, polymer substrates triggered unique expression profiles of anti-and pro-inflammatory cytokines in human peripheral blood mononuclear cells. Implantation of PCL, silk, PLA, and PA patches on the epicardial surface of healthy rats induced a classical foreign body reaction pattern, with encapsulation of polymer fibers and induction of the nonspecific immune response, whereas Col and PHB patches were progressively degraded. When implanted on infarcted rat heart, Col, PCL, and PHB reduced negative remodeling, but only PHB induced significant angiogenesis. Importantly, Col and PHB modified the inflammatory response to an M2 macrophage phenotype in cardiac tissue, indicating a more beneficial reparative process and remodeling. Collectively, these results identify PHB as a superior substrate for cardiac repair.

Over the last decade, cell therapy has emerged as a potentially new approach for the treatment of cardiovascular diseases. Among the wide range of cell types and sources, adipose-derived mesenchymal stem cells have shown promise, mainly due to its plasticity and remarkable paracrine-secretion capacity, largely demonstrated at the in vitro and in vivo levels. Furthermore, its accessibility and abundance, the low morbidity of the surgical procedure, its easy isolation, culture, and long-term passaging capacity added to its immunomodulatory properties that could allow its allogeneic transplantation, making it one of the most attractive candidates for clinical application. In this chapter, we will focus on the methodology for the isolation, expansion, phenotypical characterization, differentiation, and storage of the adipose-derived stem cells.