Functional role of the long noncoding RNA X-inactive specific transcript in leiomyoma pathogenesis

Objective: To determine the expression and functional roles of a long noncoding RNA (lncRNA) X-inactive specific transcript (XIST) in leiomyoma. Design: Experimental study. Setting: Academic research laboratory. Patient(s): Women undergoing hysterectomy for leiomyoma. Intervention(s): Overexpression and underexpression of XIST; blockade of specific protein 1 (SP1). Main Outcome Measure(s): Expression of XIST in leiomyoma and its effects on microRNA 29c (miR-29c), miR-200c, and their targets. Result(s): Leiomyoma expressed statistically significantly more XIST as compared with matched myometrium, independent of race/ ethnicity and menstrual cycle phase. By use of a three-dimensional spheroid culture system, we found reduced XIST levels in leiomyoma smooth muscle cells (LSMC) after treatment with 178-est radiol, progesterone, and their combination. The expression of XIST was downregulated by treatment with the SP1-inhibitor mithramycin A and SP1 small interfering RNA. Knockdown of XIST resulted in inhibition of cell proliferation, up-regulation of miR-29c and miR-200c, and a concomitant inhibition of the target genes of these miRNAs, namely collagen type 1 (COL1A1), collagen type III (COL3A1), and fibronectin (FN1). By contrast, overexpression of XIST in myometrium smooth muscle cells repressed miR-29c and miR-200c, and induced COL1A1, COL3A1, and FN1 levels. By use of RNA immunoprecipitation analysis we confirmed XIST has sponge activity over miR-29c and miR-200c, which is more pronounced in leiomyoma as compared with myometrium. Conclusion(s): Our data demonstrate that increased expression of XIST in leiomyoma results in reduced expression of miR-29c and miR-200c with a consequent up-regulation of the genes targeted by these microRNAs including COL1A1, COL3A1, and FN1, which play key roles in extracellular matrix accumulation associated with fibroids. (C)2020 by American Society for Reproductive Medicine.

Automated summary

This study reveals that increased expression of XIST in leiomyoma leads to decreased expression of miR-29c and miR-200c, resulting in the up-regulation of genes targeted by these miRNAs, including COL1A1, COL3A1, and FN1, which are associated with extracellular matrix accumulation in fibroids.