Receptor-mediated transfection of murine and ovine mammary glands in vivo.

Transfection of HC-11 murine epithelial mammary cells as well as murine and sheep mammary glands were carried out using insulin-containing constructs that deliver DNA by receptor-mediated endocytosis to receptor-expressing cells. In vivo transfection of mammary gland tissue with the luciferase gene was carried out by introducing the DNA constructs into the mammary ducts of both mice and sheep. The successful transfection of ewe mammary glands was demonstrated by the detection of luciferase activity in mammary gland biopsy material up to a month after a single administration of the construct. To test whether products of expression of transfected genes could be secreted into the milk in this system, the N-terminal secretory signal sequences of bovine beta-lactoglobulin or the entire coding sequence of human alpha-lactalbumin were fused to the N terminus of the luciferase gene. After transfection with the modified luciferases, both murine and sheep milk could be shown to contain luciferase activity, whereas mice, which had been transfected with the nonmodified luciferase gene, did not secrete any activity in the milk. This approach demonstrates for the first time the possibility of gene transfer in vivo into mammary gland epithelial cells using constructs delivering DNA via receptor-mediated endocytosis.