Abstract
Mechanical load and postmenopausal hypoestrogen are risk factors for pelvic organ prolapse (POP). In this study, we applied a 0.1-Hz uniaxial cyclic mechanical stretching (CS) with 10% elongation and 10−8 M 17-β-estradiol to vaginal fibroblasts isolated from postmenopausal women with or without POP to investigate the effects of CS and estrogen on cell morphology and cytoskeletons of normal and POP fibroblasts. Under static culture condition, POP fibroblasts exhibited lower cell circularity and higher relative fluorescence intensities (RFIs) of F-actin, α-tubulin and vimentin. When cultured with CS, all fibroblasts grew perpendicular to the force and exhibited a decreased cell projection area, cell circularity and increased cell length/width ratio; normal fibroblasts exhibited increased RFIs of all three types of cytoskeleton, and POP fibroblasts exhibited a decreased RFI of F-actin and no significant differences of α-tubulin and vimentin. After being cultured with 17-β-estradiol and CS, normal fibroblasts no longer exhibited significant changes in the cell projection area and the RFIs of F-actin and α-tubulin; POP fibroblasts exhibited no significant changes in cell circularity, length/width ratio and F-actin even with the increased RFIs of α-tubulin and vimentin. These findings suggest that POP fibroblasts have greater sensitivity to and lower tolerance for mechanical stretching, and estrogen can improve the prognosis.
Highlights
Pelvic organ prolapse (POP) is a common disorder predominately diagnosed in postmenopausal women [1], with more than 40% of women aged 50–79 years exhibiting a certain degree of POP [2]and approximately 30% of surgical treatment cases requiring reoperation [3], adversely affecting the sufferer’s quality of life
Mechanical loading on fibroblasts in vitro is often introduced using a substrate stretching method to mimic the environment in vivo, and uniaxial stretching studies have provided much information about the effects of mechanical loads on fibroblasts cultured on a two-dimensional substrate; 10% mechanical stretching of fibroblasts is well within the physiologically relevant levels of force normally experienced by tendon fibroblasts in vivo [13], and a 0.1-Hz stretching frequency seems likely to mimic the change of intra-abdominal pressure while a woman holds her breath to exert pressure under conditions of labor, constipation, or heavy lifting
We selected a 12-h stretching duration every day to mimic a woman’s daily activities in the stretching experiment. This approach was designed to investigate the changes in the cell morphology and the relative fluorescence intensities (RFIs) of the cytoskeletal proteins F-actin, α-tubulin and vimentin using confocal laser scanning microscopy to determine the effects of mechanical stretching on POP fibroblasts and to evaluate the efficacy of estrogen therapy (ET)
Summary
Pelvic organ prolapse (POP) is a common disorder predominately diagnosed in postmenopausal women [1], with more than 40% of women aged 50–79 years exhibiting a certain degree of POP [2]. The female pelvic floor is a special structure that maintains pelvic organs within the body while allowing the passages of the urinary tract, genital tract and rectal hiatus; at the same time, the female pelvic floor is subjected to a constantly changing mechanical load from intra-abdominal pressure and gravity due to woman’s upright activities. The superimposition of these two effects forms the physiological basis of POP. This approach was designed to investigate the changes in the cell morphology and the relative fluorescence intensities (RFIs) of the cytoskeletal proteins F-actin, α-tubulin and vimentin using confocal laser scanning microscopy to determine the effects of mechanical stretching on POP fibroblasts and to evaluate the efficacy of estrogen therapy (ET)
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