Growth of foreign cells after conditional and selective destruction of fetal host cells

Abstract

Foreign cells can be grown in fetal non-mammalian hosts for the production of transplant organs and tissues, the development of new therapeutic agents, and the production of biological factors and drugs. Tissue-specific injury to fetal host target cells is carried without substantial injury to the maternal host or foreign cells, providing an environment in which the injured tissue can be regenerated with the foreign cells.

1 . A method of obtaining an expanded population of foreign replacement cells, comprising steps of:
 (a) selectively destroying native cells in a tissue of a fetal non-human mammal host, wherein the number of maternal cells of the same tissue is not substantially reduced;   (b) implanting foreign replacement cells in the tissue of the fetal non-human mammal host, whereby the foreign replacement cells replace destroyed native tissue cells, thereby forming a chimeric tissue comprising an expanded population of foreign replacement cells; and   (c) separating the expanded population of foreign replacement cells from the chimeric tissue.   
     
     
         2 . The method of  claim 1  wherein the step of separating comprises one or more of fluorescence activated cell sorting, magnetic separation, antibody-mediated separation, ligand-receptor mediated separation, and administering a prodrug for a suicide gene product. 
     
     
         3 . The method of  claim 1  wherein the native cells comprise a transgene which encodes a protein selected from the group consisting of a suicide gene product, a fluorescent protein, an antigen, a receptor ligand, and an iron-chelating protein. 
     
     
         4 . The method of  claim 3  wherein the transgene encodes the suicide gene product. 
     
     
         5 . The method of  claim 4  wherein a first population of native cells is selectively destroyed by a first administration of a prodrug for the suicide gene product. 
     
     
         6 . The method of  claim 5  further comprising at least one additional administration of the prodrug. 
     
     
         7 . The method of  claim 4  wherein the suicide gene product is selected from the group consisting of thymidine kinase, mutated thymidine kinase, cytosine deaminase, carboxylesterase, carboxypeptidase, deoxycytidine kinase, guanosine-xanthine phosphoribosyl transferase, nitroreductase, purine nucleoside phosphorylase, and thymidine phosphorylase. 
     
     
         8 . The method of  claim 1  wherein the tissue comprises liver, hematopoietic, endothelial, neural epithelial, retinal, pigment epithelial, myocardial, skeletal muscle, smooth muscle, thymus, pancreas, lung, intestine, kidney, endocrine, cartilage, or bone cells. 
     
     
         9 . The method of  claim 1  wherein the fetal non-human mammal host is selected from the group consisting of a primate, an artiodactyl, a rodent, a carnivore, and a lagomorph. 
     
     
         10 . The method of  claim 1  wherein the native cells are destroyed using an immunoliposome. 
     
     
         11 . The method of  claim 1  wherein the native cells are destroyed using a liposome comprising a toxin. 
     
     
         12 . The method of  claim 11  wherein the liposome comprises a tissue-specific targeting ligand. 
     
     
         13 . The method of  claim 12  wherein the tissue-specific targeting ligand is an antibody. 
     
     
         14 . The method of  claim 9  wherein the fetal non-human mammal is an artiodactyl. 
     
     
         15 . The method of  claim 14  wherein the artiodactyl is a pig. 
     
     
         16 . The method of  claim 14  wherein the artiodactyl is a transgenic artiodactyl. 
     
     
         17 . The method of  claim 1  wherein the maternal cells are not transgenic. 
     
     
         18 . The method of  claim 3  wherein the transgene comprises a universal promoter or a cell-specific promoter. 
     
     
         19 . The method of  claim 18  wherein the promoter is the universal promoter and the universal promoter is selected from the group consisting of a MoMLV promoter, an RSV LTR promoter, a Friend MuLv LTR promoter, an adenovirus promoter, a neomycin phosphotransferase promoter, a late parvovirus promoter, a Herpes virus thymidine kinase (TK) promoter, an SV40 promoter, a metallothionein promoter, a cytomegalovirus (CMV) immediate early promoter, and a CMV immediate late promoter. 
     
     
         20 . The method of  claim 18  wherein the promoter is the cell-specific promoter and the cell-specific promoter is selected from the group consisting of an albumin promoter, an α-fetoprotein promoter, a whey acidic protein promoter, a tyrosine-related promoter (TRP), a DF3 enhancer promoter, a tyrosine hydroxylase promoter, an adipocyte P2 promoter, a phosphoenolpyruvate carboxykinase (PEPCK) promoter, a carcinoembryonic antigen (CEA) promoter, and a casein promoter. 
     
     
         21 . The method of  claim 1  wherein the tissue is liver. 
     
     
         22 . The method of  claim 1  wherein the foreign replacement cells are hepatocytes. 
     
     
         23 . The method of  claim 6  wherein at least one of the at least one additional administrations is post-natal.