Remarkably, shRNA-mediated suppression of p21 expression during fibrotic disease development, between days 10 and 21 after intratrachial BLM instillation, almost entirely prevented drug-induced senescent cell accumulation and ECM deposition, reduced the inflammatory response, and restored damaged architecture in lung tissue, thereby nearly completely reversing BLM-induced lung fibrosis. This evidence concerns the gene CDKN1A and pulmonary fibrosis.