Immunophenotypic characterization of human bone marrow endosteal cells

In order to determine the relationship between bone marrow (bm) endosteal c ells (EDC) and hemopoietic progenitors, we have analyzed the immunophenotyp e of EDC using various antibodies (Ab) against mesenchymal antigens. The Ab were applied on paraffin sections of normal bm (iliac crest, n=17; talus, n=1; phalanx, n=1), myeloregenerative bm (after chemotherapy), and hematolo gic disorders (acute myeloid leukemia (AML), n=8; chronic myeloid leukemia (CML), n=6; myelodysplastic syndromes (MDS), n=14; severe aplastic anemia ( SAA), n=4; essential thrombocythemia (ET), n=2; idiopathic (primary) osteom yelo-fibrosis (IMF), n=1; polycythemia vera (PV), n=1). In normal bm, EDC w ere found to react with Ab against vimentin, tenascin, alpha-smooth muscle actin, osteocalcin, CD51, and CD56, but did not react with Ab against CD3, CD15, CD20, CD34, CD45, CD68, or CD117. An identical phenotype of EDC was f ound in AML, MDS, SAA, ET, IMF PV, myeloregenerative bm, and peripheral bon es lacking active hemopoiesis (talus, phalanx). In patients with CML, EDC r eacted with Ab to CD51, but did not react with Ab to CD56. Based on their u nique antigen profile, EDC were enriched from normal bm by enzyme digestion and cell sorting. However, these enriched cells (CD56(+), CD45(-), CD34(-) ) did not give rise to hemopoietic cells under the culture conditions used, i.e. in the presence of the growth factors IGF-1, bFGF, SCF, IL-3, and GM- CSF. Together, our data do not support the hypothesis that EDC are totipote nt mesenchymal progenitors giving rise to hemopoietic cells.