SFRP2 inhibits aggregate formation and mesodermal specification in P19Cl6 cells treated with DM for 6 days (n = 6). (A–C): Bright-field images (×200) showing morphology of P19Cl6 cells grown as a monolayer at baseline (A), following treatment with DM (B), or following treatment with DM and SFRP2 (3 nM) (C). (D): Number of aggregates per high power field in P19Cl6 cells following treatment with DM in the presence or absence of SFRP2. (*, p < .01 between DM-treated and DM + Sfrp2-treated groups.) (E): Reverse transcription-polymerase chain reaction (PCR) demonstrating expression of genes associated with mesodermal specification in P19Cl6 cells treated with DM for 6 days in the absence or presence of SFRP2 (3 nM). (F): Nanog expression by quantitative PCR in P19Cl6 cells treated with DM for 6 days with or without SFRP2 (3 nM) (*, p < .05; n = 3; bars represent SD). Abbreviations: CTRL, control; DM, differentiation medium; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.