Changes in transcription profile and cytoskeleton morphology in pelvic ligament fibroblasts in response to stretch: the effects of estradiol and levormeloxifene

Abstract

Failure of ligamentous support of the genital tract to resist intra-abdominal pressure is a plausible underlying mechanism for the development of pelvic organ prolapse, but the nature of the molecular response of pelvic tissue support remains unknown. We hypothesized that the expression of genes coding for proteins involved in maintaining the cellular and extracellular integrity would be altered as a result of mechanical stretch. Therefore, cDNA microarrays were used to examine the difference in transcriptional profile in RNA of primary culture fibroblasts subjected to mechanical stretch and those that remained static. Out of 34 mechano-responsive genes identified (P < 0.05), four were coding for regulation of actin cytoskeleton remodelling, and its interaction with the extracellular matrix proteins; these are phosphatidyl inositol-4-phosphate 5-kinase (PIP5K1C), the human signal-induced proliferation associated gene-1 (SIPA-1), TNFRSF1A-associated via death domain (TRADD) and deoxyribonuclease 1-like 1 (DNase 1-L1). The transcriptosomal changes led us to investigate the phenotypic consequences of stretch, levormeloxifene and estradiol (E(2)) on the cytoskeleton of cultured fibroblasts. The percentage of cells with abnormal F-actin configuration was significantly higher in fibroblasts subjected to stretch compared with the static model (P < 0.0001). Levormeloxifene caused similar significant alterations in actin morphology of the static fibroblasts. The use of E(2) did not reverse the process or protect the cells from the effect of stretch, but significantly increased the rate of fibroblast proliferation, suggestive of a role in healing process. Mechanical stretch and/or levormeloxifene disturb the fibroblasts ability to maintain the cytoskeleton architecture and we speculate that they may disrupt ligamentous integrity and result in clinical prolapse.

Changes in connective tissue in patients with pelvic organ prolapse—a review of the current literature

“…Ewies demonstrated recently that mechanical stretch disturbs the fibroblasts' ability to maintain the cytoskeleton architecture. The use of estrogens did not reverse the process or protect the cells from the effect of stretch, but significantly increased the rate of fibroblast proliferation, suggesting their role in the healing process [62].…”

Recent studies of genetic dysfunction in pelvic organ prolapse: The role of collagen defects

“…23 Several studies have also demonstrated modified fibroblast responses in prolapse. [41][42][43][44] Several authors have analysed the expression of collagen regulators (MMP and TIMP) ( Table 2). Expression of MMP-1,-2 and -9 is increased in women with prolapse, demonstrating more collagen breakdown with loss of tissue integrity.…”

Expression of estrogen receptors in the pelvic floor of pre- and post-menopausal women presenting pelvic organ prolapse

“…Alterations in the quantity and quality of collagen, morphology of connective tissue after menopause, and experimental evidence that estrogen modulates the collagen metabolism, strongly indicate the involvement of estrogens in the pathogenesis of pelvic organ prolapse [12]. It is also believed that the appearance of prolapse and mechanical stretch disturb the fibroblast's ability to maintain the cytoskeleton architecture and quality of the extracellular matrix [13]. In addition, estrogen has been shown to decrease tissue-degrading matrix metalloproteinases in fibroblasts derived from pelvic floor connective tissue.…”