Microarray analysis of fractionated endosteal cells. (A) Hierarchical clustering analysis of gene expression in ALCAM+Sca-1−, ALCAM−Sca-1−, and ALCAM−Sca-1+ populations. (B) Heat map of genes implicated in the control of HSCs in BM niches. The ALCAM+Sca-1− population tended to express genes involved in cell-to-cell and cell-to-ECM (extracellular matrix) interactions between HSCs and niche cells. In contrast, the ALCAM−Sca-1+ population highly expressed growth factors, cytokines and chemokines known to be involved in the regulation of quiescence and proliferation of HSCs.