Characterization of rat testicular teratoma and its derived cell lines, with particular reference to possible...

The original tumor, 4 cm in diameter, was found in the left testis of a 2-month old SD rat. The tumor consisted of well-differentiated, mature tissues such as bone, cartilage, adipose tissue, smooth and skeletal muscles, skin, hair, glands (salivary, sebaceous, apocrine and pancreatic exocrine glands) and trachea, as well as nerve tissues. The tumor was diagnosed as a mature type of teratoma, a rare in rat testis. Cloned cell lines (named TSD-B4S and TSD-F9R) were established from the tumor; cellular properties of these cell lines were similar to each other; basically, their cultured cells exhibited vimentin-positive mesenchymal nature with occasional cells reacting to α-smooth muscle actin, glial fibrillary acidic protein and CD163 (a macrophage marker). The cell lines showed tumorigenicity when inoculated into nude mice, being composed of immature mesenchymal cells arranged mainly in a sheet. In TSD-B4S cells treated with differentiation factors, we demonstrated mesenchymal differentiations towards adipogenic, osteogenic and myofibrogenic cells. The cell line (TSD-B4S) would become a useful tool for studies on stem cell differentiation, because the teratoma arises from primordial germ cells like embryonic stem cells.