Differential gene expression in pubococcygeus muscle from patients with pelvic organ prolapse

This study was undertaken to compare differential gene expression in the pubococcygeus muscle in patients with pelvic organ prolapse and controls.

We performed microarray analysis on individual pubococcygeus muscle biopsy specimens from five patients with stage III or IV pelvic organ prolapse and five control subjects without prolapse. This study received full Institutional Review Board approval. Total RNA was extracted, purified, and probed on the Human Genome U95A Array for each individual sample. RNA from patients and controls was not pooled. For microarray analysis, 7 microg of total RNA was used to synthesize complementary DNA that was then biotinylated. Arrays were hybridized for 16 hours in the GeneChip Fluidics Station 400 and were washed and scanned with the Hewlett-Packard GeneArray Scanner. Affymetrix GeneChip 5.0 software was used for scanning and data analysis.

Of the 12626 total genes compared, 257 genes were more than 2-fold underexpressed, 20 genes were more than 5-fold underexpressed, and 3 genes were more than 10-fold underexpressed in patients with pelvic organ prolapse compared with control subjects. Myosin-binding protein H was 24.7 times underexpressed in patients with prolapse (normalized signal intensity [NSI]: 0.46 [0.2-0.6]) compared with controls (NSI: 11.4 [0.2-31.3]). Skeletal muscle myosin heavy polypeptide 3 was 17.4 times underexpressed in patients with prolapse (NSI: 0.85 [0.7-0.9]) compared with controls (NSI: 14.8 [1.5-38.3]). Of the 12,626 genes compared, 479 genes were more than 2-fold overexpressed, 18 genes were more than 5-fold overexpressed, and 2 genes were more than 10-fold overexpressed in patients with pelvic organ prolapse compared with controls. Many of these overexpressed genes were related to actin and myosin proteins. Smooth muscle myosin heavy chain was 11.8 times overexpressed in patients (NSI: 5.21 [0.25-22.71]) compared with controls (NSI 0.44 [0.11-0.71]). Myosin light-chain kinase was 5.8 times overexpressed in patients (NSI: 7.9 [0.5-36.1]) compared with controls (NSI: 1.37 [0.38-1.8]). Extracellular matrix proteins were also differentially regulated. Cartilage oligomeric matrix protein precursor was found to be 6.0 times underexpressed, whereas tenascin-C (hexabrachion) was 5.1 times overexpressed in prolapse patients.

These data suggest that the differences between patients with advanced pelvic organ prolapse and controls may be related to differential gene expression of structural proteins that are related to actin and myosin as well as extracellular matrix proteins in the pubococcygeus muscle. Studies are ongoing to confirm these findings and to further characterize the role of these genes in prolapse.