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Human-Induced Pluripotent Stem Cells: Banking and Characterization
Published in Deepak A. Lamba, Patient-Specific Stem Cells, 2017
Uthra Rajamani, Lindsay Lenaeus, Loren Ornelas, Dhruv Sareen
The teratoma assay is an in vivo method for demonstrating pluripotency and differentiation capabilities of iPSCs. Teratomas are rapidly growing benign tumors and often comprised of all three germ layers. Teratoma assay involves the injection of iPSCs into immunodeficient mice (52), and these eventually develop into tumors that can be excised and pathologically examined (52). The ability of iPSCs to form tumors and tissues consisting of all three germ layers in vivo serves as an indicator of pluripotency (Figure 2.8). This assay involves the sacrifice of mice and can be time consuming. Approximately 1–5 × 106 iPSCs are injected into an immunodeficient mouse, and the growth of tumor is monitored. The injection site of iPSCs varies from one research group to another. Some common sites include subcutaneous (53), intramyocardial, and skeletal muscles (54); kidney capsules (45,55); and testes (56). The injected animals have to be monitored for about two to three months as teratomas develop, and this process is laborious. Immunohistochemical and pathological analyses of the teratoma are performed and often provide only a qualitative measure of a few cell types representative from each of the three germ layers. Teratoma formation assays are time consuming and expensive, and with recent technological advances in iPSC characterization, they have become redundant. Given these limitations and the push to reduce the burden of unnecessary animal experimentation, teratoma formation assay is now less frequently used for assessing iPSC pluripotency.
Teleology and Defining Sex
Published in The New Bioethics, 2018
Nathan K. Gamble, Michal Pruski
This does not disparage men and women with DSD any more than it is to disparage someone with MCAD. A male with DSD may indeed possess things that emanate from a female (e.g. an ovary in the case of mosaicism), but as accidents (it is an attribute of that male), not proper accidents (it does not properly emanate from his sex – maleness). An ovary in a male is categorically similar to having a teratoma, a type of tumour containing random anatomical structures (e.g. teeth, hair, etc.); those structures have become an attribute of the human with them but they did not emanate from him as a human (i.e. humans normally do not have teratomas).