Use of nonionic surfactants for effective supply of phosphatidic acid in serum-free culture of Chinese hamster ovary cells

We have previously shown [Sakai et al., J. Biosci. Bioeng., 88, 306-309 (19 99)] that exogenously supplied phosphatidic acid (PA) and lysophosphatidic acid (LPA) promoted the growth of Chinese hamster ovary (CHO) cells in seru m-free culture. However, the direct addition of high concentrations of thes e phospholipids alone to the culture medium resulted in the formation of pr ecipitates. We therefore examined the use of two nonionic surfactants, Twee n 80 and Pluronic F-68, as a means of supplying PA more effectively to CHO cells in a serum-free culture. A clear dispersion of PA from egg yolk lecit hin that could be successfully sterile-filtered was obtained by using Tween 80 or Pluronic F-68. When PA prepared with either of the surfactants was a dded to serum-free media, precipitation was noticeably reduced. Furthermore , the growth-promoting activity of PA was considerably enhanced by the pres ence of the surfactants. Since Tween 80 and Pluronic F-68 themselves posses sed no growth-stimulating property, it was suggested that the enhanced grow th-promoting activity results from the improved availability of PA to the c ells. The use of Tween 80 with PA analogues having saturated acyl chains al so accelerated cell growth, whereas these PAs showed little growth-promotin g activity, due to their poor water-solubility, when added alone.