THE ORIGIN OF THE HEMATOPOIETIC MICRO-ENVIRONMENT IN CONTINUOUS BONE-MARROW CULTURE

Abstract

Marrow-derived adherent cells (MDAC) provide a microenvironment which supports the proliferation of hematopoietic stem cells [HSC] in continuous bone marrow culture. The origin of MDAC was investigated. Normal CBA mice were transplanted with marrow cells from CBA donors bearing two T6 chromosomes. Five wk after transplantation, the mice were sacrificed, their marrow cells explanted in liquid culture, and the numbers of T6-positive and T6-negative mitoses were monitored during cultivation of MDAC. After 6 wk, established MDAC monolayers were recharged with 2nd explants of marrow cells and their capacity to support HSC proliferation in continuous marrow culture was assessed. The number of T6-positive mitoses declined steadily during the period of MDAC cultivation and none were detected after 4 wk. The MDAC monolayers were able to support in vitro proliferation of CFUs [spleen colony-forming units] for periods of a least 5 wk. The in vitro hematopoietic microenvironment was apparently of recipient origin and therefore stromal.