Characterization of rheumatoid arthritis induced pluripotent stem cells. (A) High-resolution, G-banded karyotype indicated a normal diploid female chromosomal content 46XX in rheumatoid arthritis (RA) induced pluripotent stem cells (iPSCs). (B) Teratoma formation occurred after injection of RA iPSCs into immunocompromised mice. Tumors were detected from the sites of injection and harvested after 3 months, and were examined for the presence of cells of three embryonic germ layers. Teratomas contained tissue from all three germ layers, including the gland (endoderm), blood vessel (mesoderm), adipose tissue (mesoderm), and skin-like structure (ectoderm).