Myofibroblastic stromal cells isolated from human bone marrow induce the proliferation of both early myeloid and B-lymphoid cells

Normal human bone marrow stromal cells (BMSC) were isolated from Dexter-type long-term cultures according to their capacity to adhere to plastic and to their lack of hema-topoietic antigens. The BMSC displayed a homogeneous appearance and a myofibroblastic phenotype in culture. The stromal cells (SC) were shown to support the prolifera-tion of purified CD34+ hematopoietic progenitors and per-mitted us to maintain myeloid cells for several weeks in culture. In addition, the BMSC induced the proliferation of purified CDlO+sp- fetal BM B-cell precursors (BCP). The capacity of the BMSC to induce the proliferation of early myeloid cells was shared by several other human fibroblas-tic-like cell types. In contrast, the BMSC were far superior to other adherent cells for induction of BCP proliferation. This capacity was largely mediated by endogenously pro