Human milk protein production in xenografts of genetically engineered bovine mammary epithelial stem cells.
BACKGROUND
In the bovine species milk production is well known to correlate with mammary tissue mass. However, most advances in optimizing milk production relied on improvements of breeding and husbandry practices. A better understanding of the cells that generate bovine mammary tissue could facilitate important advances in milk production and have global economic impact. With this possibility in mind, we show that a mammary stem cell population can be functionally identified and isolated from the bovine mammary gland. We also demonstrate that this stem cell population may be a promising target for manipulating the composition of cow's milk using gene transfer.


RESULTS
We show that the in vitro colony-forming cell assay for detecting normal primitive bipotent and lineage-restricted human mammary clonogenic progenitors are applicable to bovine mammary cells. Similarly, the ability of normal human mammary stem cells to regenerate functional bilayered structures in collagen gels placed under the kidney capsule of immunodeficient mice is shared by a subset of bovine mammary cells that lack aldehyde dehydrogenase activity. We also find that this activity is a distinguishing feature of luminal-restricted bovine progenitors. The regenerated structures recapitulate the organization of bovine mammary tissue, and milk could be readily detected in these structures when they were assessed by immunohistochemical analysis. Transplantation of the bovine cells transduced with a lentivirus encoding human β-CASEIN led to expression of the transgene and secretion of the product by their progeny regenerated in vivo.


CONCLUSIONS
These findings point to a common developmental hierarchy shared by human and bovine mammary glands, providing strong evidence of common mechanisms regulating the maintenance and differentiation of mammary stem cells from both species. These results highlight the potential of novel engineering and transplant strategies for a variety of commercial applications including the production of modified milk components for human consumption.
Department of Veterinary Morphophysiology, University of Turin, Grugliasco, Italy.
Eugenio
E
Martignani
Peter
P
Eirew
Paolo
P
Accornero
Connie J
CJ
Eaves
Mario
M
Baratta
D000818:Animals; D002417:Cattle; D002469:Cell Separation; D017690:Cell Transplantation; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005818:Genetic Engineering; D006801:Humans; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008894:Milk Proteins / Q000096:biosynthesis*; D008895:Milk, Human; D011994:Recombinant Proteins / Q000096:biosynthesis; D013234:Stem Cells / Q000378:metabolism*
D008894:Milk Proteins; D011994:Recombinant Proteins