The focus of this research was to investigate the use of an immortalized bovine
mammary epithelial cell line as a starting material for xenogeneic transplantation into the
mammary glands of immunocompetent recipients. PSG-5 cells (a clonal derivative of the
MAC-T cell line engineered to express ovine IGF-I ) were transplanted into the cleared
mammary fat pads of recipient mice. Following transplantation, spheroidal cell structures
were observed in the cleared mammary fat pads of immunocompetent control mice and in
mice exposed to PSG-5 cells during fetal development. Spheroidal cell structures were not
observed in glands that had not received cell transplants. The success of this xenogeneic
transplantation prompted the development of a MAC-T cell clone expressing a bacterial β-galactosidase
(βMAC-T's) for use as a histological marker protein. Studies were then
performed to determine the most appropriate age and location for cell transplantation into
ovine recipients. Between three and 12 weeks of age, parenchymal volume in the mammary
glands collected from e\ves in this study (n=4/age group: 3,6,9, and 12 weeks) increased
nearly lO-fold (3.8cm3 to 34.5cm3
). Total gland volume increased approximately 5-fold (67.3cm3 to 316.2cm3
). Based on these determinations of parenchymal and glandular
volumes, we determined that transplantation should begin with lambs at about three weeks
of age. This data provides a starting point to begin trials using βMAC-T cells, which have
been engineered to express a histological marker protein, for transplantation into intact ovine
and murine mammary glands.
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