Bone marrow culture in vitro. A technique for analysis and permanent recording of cellular composition.

: The in vitro cloning of haematopoietic progenitor cells derived from blood or bone marrow is now an established technique for the study of normal and abnormal blood formation. In semi-solid agar the results are conventionally recorded as the number of clusters or colonies that grow on the plate under controlled culture conditions. However, the demonstration of detailed morphology within these cellular aggregates remains unsatisfactory. Aspiration techniques are cumbersome and invariably disturb cellular relationships within the supporting matrix while supravital staining is limited by variable uptake of dye by the agar. We describe a method in which the entire cell-containing layer is removed from the Petri dish, fixed, and after mounting on a glass-slide, is air-dried. This preparation stains well with a wide variety of biological dyes, is minimally influenced by background colouration of the culture medium and excellent demonstration of morphologic detail is possible. A permanent record of the cellular composition of the culture is easily obtained by mounting the stained agar disc.