POSTN and myocardial infarction: Moreover, collagen content measured by Sircol Collagen Assay showed a significant increease in fibrosis upon periostin administration at 1 week post-MI (52.2%±1.2% periostin-treated vs 32.0%±0.9% controls; p<0.01), and 3 months post-MI 46.5%±2.2% periostin-treated vs 28.0%±0.6% controls; p<0.05).