Mouse and rat placental cell lines express abundant amounts of laminin

Placental cell lines derived from midgestation placentae of outbred mice and rats were evaluated for the expression of the extracellular matrix protein laminin. The murine cell line, which has not been previously reported, demonstrates morphological characteristics similar to those of the rat cell line. Placental cell lines grow vigorously both in vitro and when transplanted to the peritoneum of allogeneic hosts. When transplanted, placental cells form cyst-like structures (with acellular cores) suspended in the peritoneal fluid, and invade abdominal structures forming solid masses. Using immunohistology, laminin was identified within in vitro cultured cells, within cyst-like structures and their acellular cores, and as a major component of the extracellular matrix of solid masses. Laminin was also identified in the normal rat chorioallantoic placenta. Evaluation of extracts from in vitro cultured placental cells, transplanted placental cells, and the normal chorioallantoic placenta by electrophoresis and immunoblotting demonstrated that laminins were composed of two species with molecular weights of 400,000 (A-chain) and 200,000 (B-chains). Mouse and rat placental cell lines may be valuable for studying laminin biosynthesis and function in the developing placenta.