IR-induced p16^INK4a/p19^ARF expression is dependent on BM stromal cell populations. (A) Scheme representing the strategy used for the isolation of BM-SCs and OB-SCs. (B) Representative flow cytometry profiles of BM-SCs and OB-SCs identified as Ter119⁻ (erythroid lineage), CD45⁻ (hematopoietic lineage), and CD31⁻ (endothelial lineage) isolated from a nonirradiated mouse are shown. (C) Representative flow cytometry profiles of CD44, CD90, and CD105 revealing distinct expression levels in BM-SC and OB-SC populations. (D) Osteogenic and adipocytic differentiation potential of BM-SC and OB-SC populations. (E) Differential mRNA expression levels in BM-SCs (□) and OB-SCs (■) of 5 osteoblast-associated genes normalized to 18S (runx2, sp7, opn, bglap, and ibsp). Each sample is a pool of 2 mice. (F) Quantitative PCR performed on mRNA extracted from purified/sorted BM-SCs and OB-SCs of 8-week-irradiated (+) or not (−) mice expressed as the fold increase in p16^INK4a and p19^ARF normalized to 18S. Up to 6 independent stromal cell purifications were performed using a minimum of 2-3 mice per group. *P < .05 by Student t test.