At both 24 and 48 hours post transfection with PTB siRNA, keloid fibroblasts did not show any significant change on the mRNA expression levels for ECM genes COL1A1, COL3A1 and FN1, indicating that PTB may not regulate the expressions of ECM genes in keloid fibroblasts under regular culture conditions (Fig. 4a). This evidence concerns the gene COL3A1 and keloid.