Ability of adult human stem / progenitor cells from bone marrow to traffick to damaged tissue: A unique multistep paradigm
Description
We investigated integrin expression of marrow stromal cells (MSCs) and found subconfluent MSCs expressed integrin subunits beta1-3, 5, alpha1-9, 11, V, X, and D. We tested the hypothesis that MSCs use specific integrins to adhere to endothelial cells (ECs) from the pulmonary artery (HPAEC), cardiac-derived microvasculature (HMVEC-C), and umbilical venular (HUVEC) and found in experiments with blocking antibodies to beta integrins, anti-beta5 reduced MSC adhesion to all ECs, anti-beta1 to both HUVEC and HPAEC, anti-beta3 to HUVEC, and anti-beta2 to HMVEC-C. With blocking antibodies to alpha integrins, anti-alphaX reduced adhesion to HPAEC and HMVEC-C, anti-alphaV to HPAEC, and both anti-alpha7 and anti-alphaD to HMVEC-C indicating MSCs use distinct integrins to adhere to EC from different blood vessels We tested the hypothesis that MSCs use distinct adhesion molecules for adhesion and diapedesis under hemodynamic shear conditions. Using the chorioallantoic membrane of chick embryos, MSCs were shown to adhere to ECs from arterial vessels through PSGL and VLA-4 interactions. Using a transwell-based flow assay, MSCs that were tightly adhered to ECs were unable to crawl to endothelial junctions or extravasate through the endothelial layer. MSCs expressed 3 of the 12 molecules responsible for crawling and diapedesis. MSCs expressed VLA-4, Jam-A, and Lamp-3, but not JAM-B, JAM-C, PECAM, E-Cadherin, LFA-1, Mac1, alphaIIbeta7, or LPAM. These findings provide evidence that MSCs have a poor ability to undergo diapedesis under shear flow, which may be the reason for reported low engraftment levels achieved by infused MSCs in cell-based therapies. We tested the hypothesis that MSCs use a proteolytic mechanism to invade through extracellular matrix (ECM). MSCs were shown to be able to invade through ECM in a transwell system to VEGF, GM-CSF, TNF-alpha, IL-1beta, IL-6, IL-8, IL-10, IL-13, and SDF-1, but invasion was most robust towards Complete Culture Medium. Robust invasion was not measurable in either a three-dimensional gel or a chick embryo. MSCs invasion was reduced by inhibitors to aspartyl, serine, and MMP but not cysteine proteases suggesting MSC invasion is mediated by multiple protease The characterization of MSC homing and engraftment will contribute to the therapeutic use of MSCs