Enzymatic harvesting of adult human saphenous vein endothelial cells: use of a chemically defined combination of two purified enzymes to attain viable cell yields equal to those attained by crude bacterial collagenase preparations.

Seeding vascular prostheses with enzymatically harvested endothelial cells can create endothelial linings that improve small-caliber prosthetic patency. But crude bacterial collagenases used for endothelial harvest contain cytotoxic nonspecific proteases and clostridial cell wall debris which might limit their clinical usefulness. We therefore compared the endothelial cell harvest efficiency of crude bacterial collagenase with that of purified bacterial collagenase alone, purified trypsin alone, and combinations of purified bacterial collagenase and trypsin using concentrations of pure collagenase equal in collagenolytic activity to the crude bacterial collagenase material. The efficiency of harvest from human saphenous vein segments was measured by a microtiter well-growth curve assay of the number of living endothelial cells capable of attachment to fibronectin and subsequent growth obtained per unit area of saphenous vein lumen. Whereas pure collagenase and purified trypsin alone both harvested less than 5% of the baseline endothelial cell density on the veins, a combination of purified collagenase and 0.01% w/v purified trypsin was found to harvest 22% +/- 10% (SD) (n = 8 veins) of the approximately 1.3 x 10(5) endothelial cells/cm2 available on normal saphenous veins. This figure was not statistically different from the harvest efficiency of 19% +/- 10% (N = 4 veins) (p greater than 0.05) obtained by use of 0.1% w/v crude collagenase alone. This result suggests that endothelial harvesting can be done with a defined mixture of pure enzymes which would be clinically preferable to presently used crude extracts of clostridial cultures as a standardized preparation for graft seeding.