Adipose-derived stem cells (ASCs) possess significant therapeutic potential for tissue engineering and regeneration. This study investigates the endothelial differentiation and functional capacity of ASCs isolated from elderly patients. Isolation of ASCs from 53 patients (50-89 years) revealed that advanced age or comorbidity did not negatively impact stem cell harvest; rather, higher numbers were observed in older donors (>70 years) than in younger. ASCs cultured in endothelial growth medium-2 for up to 3 weeks formed cords upon Matrigel and demonstrated acetylated-low-density lipoprotein and lectin uptake. Further stimulation with vascular endothelial growth factor and shear stress upregulated endothelial cell-specific markers (CD31, von Willebrand factor, endothelial nitric oxide synthase, and VE-cadherin). Inhibition of the PI 3 K but not mitogen-activated protein kinase pathway blocked the observed endothelial differentiation. Shear stress promoted an antithrombogenic phenotype as demonstrated by production of tissue-plasminogen activator and nitric oxide, and inhibition of plasminogen activator inhibitor-1. Shear stress augmented integrin a 5 b 1 expression and subsequently increased attachment of differentiated ASCs to basement membrane components. Finally, ASCs seeded onto a decellularized vein graft resisted detachment despite application of shear force up to 9 dynes. These results suggest that (1) advanced age and comorbidity do not negatively impact isolation of ASCs, and (2) these stem cells retain significant capacity to acquire key endothelial cell traits throughout life. As such, adipose tissue is a practical source of autologous stem cells for vascular tissue engineering. IntroductionU se of adult stem cells for vascular tissue engineering and regeneration continues to gain momentum as research reveals their improved potency and function. The majority of work involves mesenchymal stem cells (MSCs) derived from bone marrow aspiration and endothelial progenitor cells (EPCs) obtained from blood. Each of these cell types have been used to line vascular scaffolds in the creation of a tissue engineered bypass graft [1][2][3], as well as in various strategies to promote therapeutic angiogenesis in the coronary and peripheral circulations [4][5][6][7]. Although these cells are appropriate for vascular tissue engineering, their availability in patients most likely to benefit from this technology raises practical concerns. The number of stem and progenitor cells derived from bone marrow and blood decrease significantly with age and patient comorbidity [8][9][10]. Further, it has also been suggested that differentiation potential of bone-marrow-derived MSCs decreases with age [11]. Recent data also indicate that EPC function is diminished in patients with severe vascular disease and multiple coronary risk factors [12,13].An alternative source for autologous adult stem cells is adipose tissue. Adipose-derived stem cells (ASCs) are multipotent, with the capacity to differentiate into adipocytes, chondrocytes,...

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Background-Most research evaluating adipose-derived stem cells (ASC) uses tissue obtained from young, healthy patients undergoing plastic surgical procedures. Given the propensity of other adult stem cell lines to diminish with increasing patient age and co-morbidities, we assess the availability of ASC in elderly patients undergoing vascular surgical procedures, and evaluate their acquisition of endothelial cell (EC) traits to define their potential use in vascular tissue engineering.

Use of adult adipose-derived stem cells (ASCs) as endothelial cell substitutes in vascular tissue engineering is attractive because of their availability. However, when seeded onto decellularized vascular scaffolding and exposed to physiological fluid shear force, ASCs are physically separated from the graft lumen. Herein we have investigated methods of increasing initial ASC attachment using luminal precoats and a novel protocol for the gradual introduction of shear stress to optimize ASC retention. Fibronectin coating of the graft lumen increased ASC attachment by nearly sixfold compared with negative controls. Gradual introduction of near physiological fluid shear stress using a novel bioreactor whereby flow rate was increased every second at a rate of 1.5 dynes/cm(2) per day resulted in complete luminal coverage compared with near complete cell loss following conventional daily abrupt increases. An upregulation of the alpha(5)beta(1) integrin was evinced following exposure to shear stress, which accounts for the observed increase in ASC retention on the graft lumen. These results indicated a novel method for seeding, conditioning, and retaining of adult stem cells on a decellularized vein scaffold within a high-shear stress microenvironment.

The gold standard conduit for bypass of diseased small-diameter arteries remains autologous vascular tissue. In the absence of such tissue, patients are offered bypass with prosthetic material, with far less durable results. Vascular tissue engineering, the creation of a vascular conduit by seeding a tubular scaffold with various cells, may offer an alternative approach to this difficult situation. Herein we review some of the significant challenges that remain in designing an ideal vascular conduit and outline potential solutions offered by a graft created by seeding natural vascular tissue (decellularized vein allograft) with readily available autologous cells (adipose-derived stem cells).