Receptor dependent cellular uptake of synthetic low density lipoprotein by mammalian cells in serum-free tissue culture.

Low density lipoprotein (LDL) is a normal plasma component, which is of interest in a number of research areas such as hypercholesterolaemia, drug targeting in cancer chemotherapy and as a lipid supplement in tissue culture systems. Currently, however, it can only be obtained by extraction from fresh plasma samples, which yields only small quantities. Synthetic LDL (sLDL) has been prepared using readily available lipid components coupled with a synthetic amphiphatic peptide molecule containing the apoprotein B receptor sequence. sLDL was capable of supporting the growth of Chinese Hamster Ovary (CHO) and fibroblast cells in serum-free culture media in a cholesterol-dependent manner that was related to the presence of the receptor peptide molecule. sLDL could be fluorescently labelled with 3,3'-dioctadecyloxalocarbocyanine perchlorate (DiO), and once labelled was assimilated by CHO and fibroblast cells in a time- and temperature-dependent manner that was dependent upon the presence of the receptor peptide. In addition, assimilation was reduced by an excess of unlabelled native LDL. The results indicated that the interaction of sLDL with CHO and fibroblast cells occurred via a receptor dependent system, most likely the LDL cellular receptor. sLDL is therefore a useful, easily obtained substitute for native LDL with potential applications in the areas of drug targeting to cells and serum-free tissue culture systems.