MORPHOLOGICAL CHARACTERIZATION OF STROMAL CELL-TYPES IN HEMATOPOIETICALLY ACTIVE LONG-TERM MURINE BONE-MARROW CULTURES

Accurate histological evaluation of stromal morphology is very difficu lt in cultures incubated in plastic flasks. Employing glass flasketts, we were able to characterize the morphology and immunocytochemistry o f four marrow stromal cell types in a functionally intact microenviron nent of murine long-term bone marrow cultures (LTBMCs). Fibroblastoid cells stained positively for collagen Type I and III, negatively for v on Willebrand factor (vWf), the mouse macrophage F4/80 antigen, and th e Bandeiraea simplicifolia lectin I isolectin B4 (BSL I-B4). Endotheli al cells stained positively for vWf antigen and lectin BSL I-B4 but ne gatively for collagen Types I and III and for F4/80 antigen. Fat-conta ining cells had a dense, ovaloid, indented nucleus and fat-containing vacuoles. Macrophages were strongly positive for the F4/80 antigen and stained weakly with BSL I-B4. Between the fourth and ninth weeks afte r culture initiation, fibroblastoid and endothelial cells remained con stant, between 21 +/- 2% and 24 +/- 2% and between 3 +/- 0.3% and 4 +/ - 0.4%, respectively, of the total stromal cell population. By contras t, the percentage of fat-containing cells decreased significantly from 26 +/- 3% at Week 4 to 17 +/- 2% at Week 9, and macrophages increased significantly from 49 +/- 1% at Week 4 to 57 + 1% at Week 9. This cha racterization of the stromal cell types in functionally intact LTBMCs should assist in the study of the complex interactions among the marro w stroma, cytokine production, and hematopoiesis.