Human Adipose Derived Stem Cells (hASC's) and Soft Tissue Reconstruction: Evaluation of Methods for Increasing the Vascularity of Tissue Engineered Soft Tissue Construct

Abstract

Generation of large volumes to cover an existing soft tissue defect is often complicated by the lack of available tissue. The current options for soft tissue reconstruction include local and free flaps, collagen fillers, traditional fat grafting and other synthetic soft tissue fillers. But they all have limitations. Recently, a lot of interest has been generated regarding the use of human adipose derived stem cells for engineering a biocompatible soft tissue construct. Give their ready availability, viability and plasticity they appear to be the ideal building blocks for a cell based soft tissue construct. We find that these cells are easy to isolate in large numbers, easy to maintain in culture and capable of multi-lineage differentiation. hASC's are readily adherent to collagen based scaffolds and these function as the ideal cell delivery matrix. Since most wound beds are ischemic and hypoxic, changes in gene expression of hASC's was studied in conditions of hypoxia and serum deprivation. Microarray PCR results demonstrate the up regulation of 23 angiogenic genes including VEGFC, ANPEP, CXCL6, ANGPLT4 and CXCL5 in conditions of hypoxia. However, this angiogenic response was blunted with the presence of serum starvation in addition to hypoxia. Hence we chose to investigate methods to increase the primary neovascularization of a tissue engineered construct. Our hypothesis was that Europium Nano rods (belonging to the lanthanide series of heavy metals) would increase the angiogenic potential of hASC's. Results of a chick embryo chorioallantoic membrane assay demonstrate that Europium Nano rods potentiate the angiogenic effects of Vascular Endothelial Growth Factor (VEGF) when incorporated in hASC's. These rods are readily incorporated in hASC's by endocytosis and do not affect viability. Hence, we conclude that Europium Nano rods can function as a reliable, nontoxic extrinsic angiogenic stimulus. Further studies are needed to evaluate the 1) effects of ENR's on stem cell plasticity 2) effects on gene expression and 3) further investigate the fate of ENR's with repeated cell division.