Time-dependent inhibition of TPO mRNA expression by platelet factor 4 (PF4) and thrombospondin (TSP) in BM stromal cells.

TPO mRNA expression levels were determined by using a QISH assay at various time points after the addition of PF4 (A) and TSP (B). GAPDH mRNA levels in cells exposed to PF4 are also shown (C). The results shown are the mean ± SD values from 4 separate experiments performed in triplicate. *P < .05 compared with controls (time 0).