231 HISTOCOMPATIBLE PARTHENOGENETIC EMBRYONIC STEM CELLS

Organ or tissue transplantation is the preferred treatment for numerous diseases but is hindered by immunologic barriers. Genetically matched pluripotent embryonic stem cells generated via nuclear transfer (ntES cells) or parthenogenesis (pES cells) are possible sources of histocompatible cells and tissues. We have developed two ways of isolating pES cells that carry the full complement of major histocompatibility complex (MHC) antigens of the oocyte donors. One method entails activation of oocytes after blockade of karyokinesis in meiosis II, followed by selection of predominantly homozygous pES cells that have undergone recombination in their MHC antigen region to restore the heterozygous maternal MHC genotype (parthenote recombinant, or prES cells). The second method involves activation of immature oocytes after blockade of karyokinesis of meiosis I, followed by selection of predominantly heterozygous pES lines that retain the MHC genotype of the oocyte donor (parthenote clone recombinant, or pcrES cells). The cells are pluripotent by several criteria: teratoma formation, in vitro differentiation into hematopoietic elements, and high-level skin chimerism in blastocyst chimeras. Breeding of 8 founder females and examination of over 700 progeny failed to demonstrate germ line transmission of the pES cells. Injection of over 50 tetraploid embryos with these lines and embryo transfer have failed to support full gestational development. However, differentiated tissues from these pluripotent ES cells engraft when transplanted into genetically matched immunocompetent recipients, demonstrating that selected pES cells can serve as a source of histocompatible tissues for transplantation.