Somatic gene transfer into the lactating ovine mammary gland

Background Somatic gene therapy requires safe and efficient techniques for the gene transfer procedure. The ovine mammary gland is described as a model system for the evaluation of somatic gene transfer methods. Methods Different gene delivery formulations were retrogradely injected into the mammary gland of lactating sheep. The efficiency of the gene transfer was subsequently measured by the detection of the secreted transgene products in the milk. To counteract the milk flow in the lactating gland caused by the permanent milk production, a newly developed pretreatment of the mammary gland with hyperosmotic solutions was applied. In addition, in vivo electroporation of DNA into the mammary gland is described. Results Gene transfer using naked DNA or simple complexes of DNA with polycations did not result in traceable amounts of reporter gene products. However, utilizing the complex cationic lipid DOSPER, a peak expression of about 400 ng/ml was observed 6 days after transfection. Maximum expression rates of more than 1 µg/ml were obtained by combining hyperosmotic pretreatment and receptor‐mediated gene transfer. For the in vivo electroporation, the proof of principle for this technique in the mammary gland is reported. Conclusions The ovine mammary gland turned out to be a very well suited as a model system for evaluation and optimization of various gene transfer protocols. Copyright © 2002 John Wiley & Sons, Ltd.