BASAL TISSUE FACTOR EXPRESSION IN ENDOTHELIAL-CELL CULTURES IS CAUSEDBY CONTAMINATING SMOOTH-MUSCLE CELLS - REDUCTION BY USING CHYMOTRYPSIN INSTEAD OF COLLAGENASE

A discrepancy exists between basal tissue factor (TF) expression found in endothelial cell cultures and the failure to detect TF in unpertub ated endothelial cells in vivo. We demonstrated that basal TF expressi on in endothelial cell cultures originated from contaminating cells. T hese cells were ultrastructurally and flowcytometrically identified as smooth muscle cells. The cell cultures had been obtained from collage nase-treated human umbilical cord vessels. Histologic studies revealed that after collagenase treatment the basement membrane was digested a nd underlying structures were disrupted at some areas of the vein. We selected chymotrypsin as an alternative for the isolation of endotheli al cells. Using chymotrypsin, the endothelial lining was selectively l ost leaving the basement membrane undisturbed. Furthermore, use of chy motrypsin instead of collagenase minimized the level of basal TF activ ity. Taken together, we demonstrated that basal TF expression in endot helial cell cultures is caused by contaminating smooth muscle cells. T his contamination can strongly be reduced using chymotrypsin instead o f collagenase for isolation of endothelial cells.