Cell death, proliferation, and differentiation of BM cells with periostin-deficient OP9-309 cells. (A) Flow cytometric analysis of cells arising from cocultures of total BM and OP9 or OP9-309 cells after 2, 4, and 7 days. The lymphocyte gates are indicated in percentages; cell death was determined at day 7 (LIVE/DEAD staining). (B) After 7 days in cultures, apoptosis in the lymphocyte populations from OP9 and OP9-309 cultures was assayed by staining cells with 7-AAD and Annexin V and analyzing the cells by flow cytometry. (C) Flow cytometric analysis of CFSE distribution in BM cells after 4 and 7 days in culture (solid gray and black lines indicate cells from OP9 cultures; and dotted black and gray lines, cells from OP9-309 cultures). (D) Flow cytometry of LSK cultured 7 days on either OP9 or OP9-309 cells. The data are representative of 2 experiments.