Effects of isolation methods on proliferation and GD2 expression by porcine umbilical cords stem cells

Abstract

Cell isolation method may have effects on the characteristics of the cells isolated from porcine umbilical cords. As stem cells age or approach senescence, it is hypothesized that their properties change. We expect that isolation method and age of cells will have effects on the phenotype of porcine umbilical cord (PUC) cells during in vitro expansion. We investigated the effects of three isolation methods on PUC population doublings, ability to produce colony forming units (CFU), and amount of ganglioside GD2 (GD2) expression over eleven passages. Isolation methods were explant (Exp) in which the Wharton's Jelly was removed from cords, minced and plated, enzyme digest (Dig), and stomacher assisted enzyme digestion (Stom). Cell isolates were analyzed for GD2 expression, CFU, and population doublings at early (3), middle (7), and late (11) passage. The Exp method produced greater (P<0.05) population doublings and more (P<0.05) CFU at passage 7. Explant isolates also were numerically more likely to survive to passage 11 (9/9 isolates vs 5/9 for Dig and 7/9 for Stom). In contrast, the percent cells expressing GD2 was greater (P<0.05) for Stom isolates than Exp isolates at passage 11. There were no trends for increased passage number to decreased population doubling, CFU formation, or percent GD2 positive cells. In summary, our results indicate that the Exp isolation method produced the greatest number of population doublings over 11 passages and there were minimal effects of isolation method on CFU and GD2 expression. Although Exp may be more difficult to scale up to isolate all of the PUCs in a cord, it provided greater in vitro expansion than the enzyme methods in our experiment and may provide the most cells for biotechnological and biomedical applications.