Objective
To determine the expression of miR-29c and its target genes in leiomyoma and the role of NF-κB, specific protein 1 (SP1), and DNA methylation in its regulation. Design: Experimental study. Setting: Academic research laboratory. Patient(s): Women undergoing hysterectomy for leiomyoma. Intervention(s): Over- and underexpression of miR-29c; blockade of transcription factors. Main outcome measure(s): MiR-29c and its target gene levels in leiomyoma and the effects of blockade of transcription factors on miR-29c expression. Result(s): Leiomyoma as compared with myometrium expressed significantly lower levels of miR-29c, with an inverse relationship with expression of its targets, COL3A1 and DNMT3A. Gain of function of miR-29c inhibited the expression of COL3A1 and DNMT3A at protein and mRNA levels, secreted COL3A1, and rate of cell proliferation. Loss of function of miR-29c had the opposite effect. E2, P, and their combination inhibited miR-29c in leiomyoma smooth muscle cells (LSMC). Phosphorylated NF-κB (p65) and SP1 protein expression were significantly increased in leiomyoma. SiRNA knockdown of SP1 and DNMT3A or their specific inhibitors significantly increased the expression of miR-29c, accompanied by the inhibition of cellular and secreted COL3A1 in siRNA-treated cells. Knockdown of p65 also induced miR-29c expression but had no effect on COL3A1 expression.