Up-regulation of MMP-9 gene expression in CD14⁺ cells by conditioned media from HS-5 stromal cells. Total RNA was isolated from CD14⁺ cells from 10 healthy donors prior to cultures (No culture) or after culturing for 5 days in control medium or in conditioned medium from HS-5 (HS5CM). MMP-9 gene expression was determined by the real-time PCR assay and normalized with G3PDH gene expression. P values were calculated by paired Student t test. Data are shown as mean ± STD.