Manipulation of Hedgehog signaling in early human embryos
We propose deriving a new generation of embryonic stem cell lines with greater potential than current conventional lines. Until recently, all human embryonic stem cell (hESC) lines have been derived from one of two clearly discernible cell types, the inner cell mass (ICM), of the blastocyst stage embryo. ICM-derived hESC are able to differentiate to a number of tissue types. Nevertheless, such conventional lines range widely in how easily they give rise to adult cell types. Investigations with ‘twin’ hESC lines, i.e. lines made from splitting a single ICM, show that cells at this stage of development give rise to lines with distinct differentiation preferences. Thus a given protocol to generate a therapeutically desired cell type has a variable chance of success when applied to any particular ICM-derived hESC line.
Recently, a novel technical advance has allowed hESC to be derived from cells of significantly younger embryos (i.e. from blastomeres of 8-10 cell cleavage stage embryos). These cleavage stage hESCs are superior to conventional lines in the ease/efficiency with which they could be induced to differentiate a variety of cell types. As yet, however, only 2 such lines have been established.
Through our work in mice, we have developed a protocol to keep cleavage stage embryos from advancing through the usual program leading to blastocyst formation. We hypothesize that culturing human blastomeres under such conditions will allow more efficient derivation of cleavage stage hESC. Compared to the hESC lines in circulation today, blastomere-derived hESC lines are potentially far superior in their differentiative capacities. Such properties could greatly unify and advance the field in efforts to generate cells types of therapeutic interest.
The central hope of Proposition 71 is that human embryonic stem cell (hESC) research will alleviate devastating medical conditions such as diabetes, Parkinson's, Alzheimer's and cancer. Realization of this goal requires solving the problem of being able to reliably generate, in culture, a given cell type from any hESC line. Currently it is still not possible to differentiate (or generate) any given cell type from any given hESC line. Our proposal to create a new generation of hESC line from cells of younger embryos may move the field closer to this goal.
Recent technical advances made by the private sector on the East Coast have allowed derivation of the first two hESC lines from blastomeres (cells) of 8-10 cell embryos, i.e. cells that are only about 3 days post fertilization as opposed to 6 days in conventional hESC derivations. These two novel lines have shown a greater efficiency and capacity for differentiation than conventional lines in a number of assays. We have developed a protocol in mice that suggests a modification of this new method may improve on such blastomere-derived hESC derivations. We are therefore poised to take a lead in research creating a new generation of hESC lines that may supercede those currently in circulation, including a major source of lines made by private foundations on the East Coast. Given such a leading edge, and with one of the highest concentrations of college graduates in the nation, the state of California could transform the fields of embryonic stem cell research and medical discovery.