443. The fibroblast – smooth muscle cell relationship is altered in uterine leiomyoma

Abstract

Uterine leiomyoma (fibroids) are benign neoplasms of the myometrium. Their aetiology is still poorly understood, but they are known to be sex steroid hormone dependant. Although these tumours are thought to consist of smooth muscle cells (SMC), fibroblasts constitute a major cellular component. Genes that are central to fibroblast activation and function, including transforming growth factor-β (TGFβ), as well as many extracellular matrix (ECM) genes have altered expression in leiomyoma. Despite this, the role of fibroblasts in these tumours has not been investigated in leiomyoma before. The aims of the present study were to isolate fibroblasts from myometrium (MAFs) and leiomyoma (LAFs); and to compare gene expression of fibroblasts and SMC from these 2 different sources. Myometrium and leiomyoma were dissociated into single cell suspensions, stained with fluorescently labelled CD31, CD90 and 1B10 antibodies and separated into different cell populations using fluorescence- activated cell sorting. Endothelial cells were removed from the analysis; remaining cells were sorted into 1B10-CD90 +ve (fibroblasts) and 1B10-CD90 –ve (SMC) populations and used for RNA isolation and quantitative real-time PCR. Significantly higher levels of expression of aldehyde dehydrogenase1 (ALDH1), cellular retinoic acid binding protein 2 (CRABP2), oestrogen receptor (ERα) and progesterone receptor (PR) were observed in MAFs compared with MSMC, while no equivalent differences were observed between LAFs and LSMC; and lower levels of TGFβ were observed in fibroblasts compared with SMC in both tissues. Results for ALDH1, ERα and PR were also confirmed using immunohistochemistry. This is the first study to successfully isolate LAFs and MAFs and demonstrate an altered fibroblast-SMC relationship in uterine leiomyoma. This work provides the first evidence that LAFs might play an important role in leiomyoma pathophysiology. Investigation of fibroblast function in this disease may provide important new fundamental knowledge on its aetiology, ultimately leading to the development of new medical treatments.