A novel growth-factor-dependent myeloid cell line derived from mouse bone marrow cells contains progenitors endowed with high proliferative potential.
Constitutive expression of human colony-stimulating factor-1 receptor (CSF-1R) confers long-lasting CSF-1-dependent proliferation to mouse myeloid cell lines. We developed mice transgenic for human CSF-1R because mouse CSF-1 cannot activate human CSF-1R. Then bone marrow cells from transgenic mice were plated onto MS-5 stromal cells expressing the membrane form of human CSF-1 (2M-1 cells) in order to combine the hematopoietic supporting properties of stromal cells and the proliferative effects of CSF-1. Thus, we were able to derive a hematopoietic cell line, called 47.10, that grew indefinitely under these conditions, whereas no cell line could be developed from nontransgenic mice. Proliferation of 47.10 cells is severely affected by neutralizing anti-CSF-1R monoclonal antibodies. Morphologic and cytofluorometry analysis established that most 47.10 cells are immature myelomonocytic cells. Consistent with this phenotype, the myeloid transcription factor PU.1, but not the erythroid transcription factor GATA-1, is expressed in 47.10 cells. A few 47.10 cells (3-5%) do not express lineage specific markers; they differentiate spontaneously to lineage-positive cells after replating on 2M-1 cells. In agar cultures, 47.10 cells form 7- and 14-day colonies in response to a cocktail of granulocyte/macrophage colony-stimulating factor (2.5 ng/mL), interleukin-3 (1 ng/mL), and mouse CSF-1 (10 ng/mL). Under these conditions, about 0.5% of 47.10 cells formed large 14-day colonies (>1 mm) composed of mature monocytes and granulocytes, reflecting the presence of progenitors endowed with high proliferative potential (HPP-47.10 cells). In conclusion, we have characterized a novel continuous myeloid cell line presenting a hierarchical structure similar to that of the bone marrow progenitor cell compartment.