Altered BM niche composition and MSC function in patients with CML. (A) Strategy for isolation and characterization of the BM cellular niche components. (B) Representative FACS profiles showing gating strategy for sorting of ECs (CD45^–CD235A^–CD31⁺), MSCs (CD45^–CD235A^–CD31^–CD44^–), CD45^–CD235A^–CD31^–CD44^–CD146⁺CD271⁺ MSC subsets, and mature stromal cells (CD45^–CD235A^–CD31^–CD44⁺) within total stromal cells (CD45^–CD235A^–) from BM samples of patients with newly diagnosed CML and age-matched healthy donors (NBM). (C-E) Abnormal hematopoiesis supportive function of MSCs derived from patients with CML, examined by LTC-IC assay. (C) Experimental design of coculture system for assessing LTC-ICs. Normal BM (NBM) or CML BM CD34⁺ cells were sorted and cocultured with either NBM MSCs or CML MSCs for 6 weeks. Subsequently, the cells were collected for CFU-C assay. (D) LTC-ICs derived from NBM CD34⁺ cells cocultured with NBM or CML MSCs. (E) LTC-ICs derived from CML CD34⁺ cells cocultured with NBM or CML MSCs. (F) Quantitative polymerase chain reaction analysis of HSC niche factor expression in the NBM and CML MSCs. Horizontal lines represent median values, and each dot represents the mean of triplicate or duplicate measurements on samples from an individual donor. The data were collected from 4 to 5 independent experiments. The statistical differences were determined by paired t test (D-E) or unpaired Mann-Whitney test (F). See also supplemental Figure 1.