Fig. 4.

R1 cells form teratomas in immunocompromised mice. R1 cells directly isolated from reduction mammoplasty (A) or a single-cell–derived R1 clone expanded in culture (B) were grafted under the renal capsule of 7- to 8-wk-old female SCID/beige mice. Teratomas, harvested 16 wk after injection, were paraffin embedded, serial sectioned, and stained for the panhuman-specific marker lamin A/C to document the human origin of these structures and for lineage-specific markers. Neuroepithelial (ectodermal) marker, GFAP; pancreatic (endodermal) marker, PDX1; or cartilage (mesodermal) marker, HAPLN1 validated human-specific tissue formation in teratomas. Insets: magnified GFAP⁺ cells. Representative views show bone stained with Alizarin Red and a gastrointestinal structure with goblet cells expressing TFF3 (A, Lower). Additional views of structures expressing the endodermal marker AFP and corresponding staining for human lamin A/C are shown (B, Lower). (Scale bars, 150 µm.) Directly sorted R1 cells generated teratomas in two of five analyses, failed to generate any mass or structures in two of five analyses and gave rise to a mesoderm derivative (cartilage) in one of five analyses. In one of one attempt, a single-cell–derived R1 subclone formed a teratoma and gave rise to representative three germ layers.