Fig. 1. Isolation and purification of BMSSCs. (A) Flow cytometric analysis of MACS-sorted STRO-1⁺ marrow cells demonstrated varying levels of STRO-1 expression. There were approximately three distinct populations: dull (DULL), intermediate (INT) and bright (BRT). (B) Dual-color flow cytometric analysis of VCAM-1 (PE) expression by STRO-1⁺ (FITC) marrow cells isolated by MACS depicting a discrete population of STRO-1^BRIGHT/VCAM-1⁺ cells (region: R1), approximately 0.02% of the total BMMNC population. (C) The incidence of clonogenic cell colonies (>50 cells) + clusters (>10<50 cells) based on STRO-1^BRIGHT/VCAM-1⁺ expression was determined by limiting dilution analysis of 24 replicates per cell concentration using Poisson distribution analysis (data derived from six independent experiments).