In vitrohaemopoiesis induced in a rainbow trout pronephric stromal cell line (TPS)

To rapidly and efficiently establish haemopoietic cultures from rainbow trout,O. mykiss, a method to elicit haemopoiesis on a trout pronephric stromal cell line (TPS) was developed. The system used cocultures of pronephric cell suspensions with subconfluent cultures of TPS cells. The initiation of haemopoiesis in these cocultures occurred rapidly, and the duration of sustained haemopoiesis, after a single inoculum of fresh exogenous pronephric cells, exceeded 1 year. Analysis of cells removed from the supernatants of these cocultures revealed production of granulocytes, lymphocytes and erythrocytes. Ultrastructural analysis of haemopoietic cocultures revealed close associations between the developing blood cells and the microenvironment created by the stromal cells. The capacity of the TPS cell line to support haemopoiesis was superior to that of the RTG-2, suggesting that TPS has retained specific characteristics of the pronephric stroma. The availability of this culture system should facilitate studies onin vitrohaemopoiesis in fish.