Isolated ruminant mammary stem cell population and uses thereof for production of transgenic proteins in vivo

Thus object of the present disclosure is to provide a bovine stem cell population able to (re)generate polarized and functional structures in vitro and in vivo when transplanted in an animal model. A further object of the present disclosure is to provide a novel approach for transgene production in milk: given the huge proliferative and morphogenic potential of stem cells, such cells represent a preferential target for in vitro manipulation. The present disclosure concerns the use of a transgenic stem cell population that upon transplantation is able to regenerate mammary structure that secretes the transgene in their lumen. According to the present invention said objects are achieved thanks to the solution having the characteristics referred to specifically in the ensuing claims. Thus the claims form integral part of the technical teaching herein provided in relation to the present invention. To achieve this object, the present inventors have developed an isolated ruminant mammary stem cell population able to generate polarized and functional structures of a mammary gland tissue both in vitro and in vivo. In an embodiment of the present disclosure the isolated ruminant mammary stem cell population is able to proliferate and differentiate into luminal and myoepithelial cells, thus generating mammary alveoli, which are able to secrete milk. In a further embodiment of the instant invention, a transgenic isolated ruminant mammary stem cell population is provided, wherein the mammary stem cells contain within their DNA a construct encoding for at least one heterologous protein, which is secreted, preferably in the lumen of the luminal cells and/or the mammary alveoli. In a still further embodiment the construct is a vector, being this vector selected among a lentiviral vector. Preferably the vector is provided at the N-terminal with a secretion signal and/or with a conditional promoter able to control the expression of the heterologous protein in the luminal cells and thus in milk. In a further embodiment the heterologous protein is selected among human beta-casein, k-casein, beta-lactoglobulin, alpha-lactalbumin, monoclonal antibodies, plasma proteins such as the coagulation factors Factor XII, Factor XIII, Factor IX, albumin, human alpha 1 antitrypsin. Further embodiments of the instant disclosure concern the use of the isolated ruminant mammary stem cell population for the regeneration of a ruminant mammary gland tissue and/or for increasing milk production in a ruminant. In a further embodiment, the present disclosure concerns the use of the transgenic isolated ruminant mammary stem cell population for the production of the heterologous protein(s) in the milk of the ruminant, wherein the transgenic mammary stem cell population is transplanted in the mammary gland tissue of the ruminant.