Christopher DiMatteo

Endothelial Differentiation of Adipose-Derived Stem Cells from Elderly Patients with Cardiovascular Disease

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 anti-thrombogenic phenotype as demonstrated by production of tissue-plasminogen activator and nitric oxide, and inhibition of plasminogen activator inhibitor-1. Shear stress augmented integrin α(5)β(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.

Development of a tissue-engineered bypass graft seeded with stem cells.

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).

Availability of adipose-derived stem cells in patients undergoing vascular surgical procedures

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. METHODS AND METHODS Adipose tissue obtained by liposuction from patients undergoing vascular procedures (n = 50) was digested with collagenase and centrifuged to remove mature adipocytes. The resultant number of cells, defined as the stromal-vascular (SV) pellet, was quantified. Following a 7-d culture period and negative selection for CD31 and CD45, the resultant number of ASC was quantified. After culture in differentiating media (EMG-2), ASCs were tested for the acquisition of endothelial-specific traits (expression of CD31, realignment in shear, cord formation on Matrigel). RESULTS The SV pellet contained 2.87 ± 0.34 × 10(5) cells/g fat, and the resultant number of ASCs obtained was 1.41 ± 0.18 × 10(5) cells/g fat. Flow cytometry revealed a homogeneous ASC population (>98% positive for CD13, 29, 90). Advanced age or co-morbidity (obesity, diabetes, renal or peripheral vascular disease) did not significantly alter yield of ASC. After culture in differentiating media (EMG-2), ASCs acquired each of the endothelial-specific traits. CONCLUSION ASC isolation appears independent of age and co-morbidities, and ASCs harvested from patients with vascular disease retain their ability to differentiate into endothelial-like cells. Adipose tissue, therefore, is a practical source of autologous, adult stem cells for vascular tissue engineering.