Differential distribution of oligodeoxynucleotides in developing organs with epithelial-mesenchymal interactions

The use of antisense oligodeoxynucleotides (ODNs) to inhibit gene expression is a usefull method for determining protein function and has potential therapeutic applications. However, there is still great variability in the successfull application of antisense technology to individual systems. In order to assess the ability of different cell types to take up ODNs, developing embryonic tissues were cultured in vitro in the presence of fluoresceine labelled, phosphorothioate substituted ODNs. The distribution of ODNs in individual cell populations was assayed by fluorescent microscopy and the tissue sections were counterstained for epithelial basement membrane formation. High intracellular levels of ODNs were observed in all mesenchymal cells of the lung, salivary gland, kidney, ovary and testis. However, a significant decrease in ODN levels was observed with the formation of new epithelium in kidney and gonads, whereas mature epithelial cells in all tissues had no detecable levels of ODNs. The ability to inhibit gene expression in mesenchymal cells, but not in epithelial cells, was consistent with the distribution pattern of labeled ODNs. These results may indicate a general resistance of epithelial cells to take up ODNs in culture and bear directly on the ability of ODNs to affect gene expression in complex organs with epithelial components.