Human but not porcine cell adhesion to human fibronectin is mediated by CD29
Introduction Successful tolerance induction in xenotransplantation as well as tissue engineering with porcine matrices relies on functional interactions of porcine adhesion molecules with human extracellular matrix molecules. VLA integrins play key roles in these processes, and it is known that both chains of these molecules participate in integrin function. We have previously shown that CD29 function is not fully conserved in human-to-porcine cell-to-cell adhesion. Here, we investigated, whether the function of the common b-subunit CD29 is conserved in cell to extracellular matrix adhesion.
Materials and methods All procedures and care of laboratory animals were carried out in accordance with NIH and USDA guidelines for the care and use of laboratory animals. Fresh heparinized porcine blood was obtained from German landrace and Göttinger miniswine. Human blood was obtained from a variety of healthy donors. Human fibronectin was purchased. Using fibronectin coated plates and plates bearing naïve and stimulated human and porcine endothelial cell line monolayers, we performed static adhesion assays with naïve and phorbol ester activated human (h) and porcine (p) peripheral blood mononuclear cells (PBMC), labeled with calcein AM.
Results Using crossreactive mAb against CD29, the adhesion of human but not porcine PBMC to human fibronectin (hFN) was inhibited. Phorbol ester activation increased overall adhesion of cells to hFN but did not abrogate the blocking effect of the mAb. The same antibody was shown to stimulate adhesion of h but not p PBMC on naïve and TNF activated h and p EC layers.
Conclusions These data suggest, that porcine cells use completely different adhesion molecules than human cells to adhere to human fibronectin. Also, the function of the b-1 chain of VLA-integrins is not conserved across the pig-to-human species barrier. These differences may play important roles in both tolerance induction regimens as well as maintenance of the extracellular matrix of transplanted porcine organs or tissue engineering scaffolds.