Figure 1A: Chart for illustrating the course used to acquire samples. Bone marrow mononuclear cells (MNCs) dispersed in culture dishes, part of them changed to early phase adhesion cells (E-ad cells) within 1 week. For the next 3-7 weeks, the adhesion cell fraction was grown into BMSCs that had been characterized as a mesenchymal cell population with various cell lineages including SMCs. The dashed-line quadrangle indicates that SMCs coexist with many other cell types among bulk-BMSCs. E-ad cells were transfected with the SM22α promoter/GFP construct. In the transfected E-ad cells, GFP-positive cells (Ad (G) cells) appeared 5 days after the transfection and expressed neither mature (calponin) nor immature (SMemb) SMC-specific marker proteins at that time (see section B). After G418 selection, they were grown into individual clones (I-CL) that exhibited phenotypes consistent with smooth muscle lineage cells (see section C). Thus, Ad (G) cells eventually differentiated into SMCs that were presumed to be bulk-BMSCs. To clarify longitudinal transition of the expression of SMC-specific proteins, the total course is conveniently divided from phase 1 to phase 4. As shown in lower panel, Ad(G) cells came to be detectable (lower panel a) at phase 2, and grew into colonies at phase 3 (lower panel b). In phase 4, the colonies were picked up and investigated as individual clones (I-CL, lower panel c) with stable GFP expression (lower panel d).