Construction of temperature and Zn-dependent human stromal cell lines that amplify hematopoietic precursors from cord blood CD34+ cells

Forty-five human stromal cell lines were established from long-term bone marrow cultures transformed with a new vector, pNu MTSVts, which contains the Zn-inducible metallothionein promoter and the temperature-dependent SV40 T antigen from SV40 A58 mutant. Six of these cell Lines were studied because of their growth capacity. All cell lines differed with respect to growth potential, expression of cell surface markers, and cytokine transcripts. Major histocompatibility complex (MHC) class I, CD29, CD49d, and CD51 were present on all stromal cell lines, MHC class II and CD34 were consistently absent, and CD11a (LFA-1), CD18 (ICAM-1R), CD54 (ICAM-1), CD58 (LFA-3) CD56 (N-CAM), CD106 (V-CAM), laminin, and collagen IV were diversely expressed. All cell lines contained interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-5, and macrophage colony-stimulating factor (M-CSF) transcripts, whereas granulocyte M-CSF, TNF alpha, IL-3, IL-4, and IL-7 were diversely expressed. The most characteristic feature of these cells was their varying capacity to expand cord blood CD34(+) cells. One of these stromal cell lines ensured more than twofold expansion of the initial CD34(+)CD10(-)CD19(-) population in the first 2 weeks. Differentiation toward the B cell lineage was limited, producing only very small numbers of CD19(+) cells after 6 weeks of culture.