Adult stem cell homing and differentiation in vitro on composite fibrin matrix.

Strategies to generate differentiated cells from haematopoetic progenitor cells will enhance potential use of adult stem cells for therapeutic transplantation or tissue engineering. Transplantation of undifferentiated stem cells into recipient tissue hinges on the hypothesis of a milieu dependent differentiation and it has been suggested that a clot-equivalent scaffold is crucial for these circulating cells to anchor and multiply. Here a natural scaffold, fibrin along with fibronectin, gelatin and growth factors has been used to induce endothelial progenitor cells and smooth muscle progenitor cells to differentiate into endothelial cells and smooth muscle cells, respectively, from peripheral blood mononuclear cells. Characteristics of endothelial cells have been verified by the detection of mRNA for and immunostaining the cells for von Willebrand factor, uptake of acetylated low-density lipoproteins and measurement of released nitric oxide in the culture medium, as nitrite. The specific molecules that characterized smooth muscle cells were alpha smooth muscle actin and calponin, besides deposition of collagen type I and elastin, onto the culture matrix. The adhesive proteins used for the fabrication of endothelial progenitor cells matrix and smooth muscle progenitor cells matrix were the same, but specific differentiation was brought about by modulating the growth factor composition in the matrix and in the culture medium. Both endothelial and smooth muscle cells were consistently developed from 20 ml of human blood.