Objective: This study examines whether silencing specific β-nerve growth factor small interfering RNA (β-NGF siRNA) can affect the growth of ectopic endometriotic implants, generalized hyperalgesia, and nerve fiber density in endometriosis.
Methods: Four specific β-NGF siRNAs were detected by Western blot analysis, and the most efficient specific siRNA was transferred into rats with surgically induced endometriosis through gene transfer. The length × width × height of each ectopic transplant that survived from 2 groups were measured at pre-and postbombardment after 2 weeks. The transplants were collected 2 weeks after bombardment. Warm-water tail flick test was performed before the rats were sacrificed. The specimens were sectioned and stained immunohistochemically with antibodies against the types of nerve fibers to compare the presence of different nerve fibers in the treatment and control groups. The serums and supernatants of the peritoneal washings in the treatment and control groups were collected for enzyme-linked immunosorbent assay (ELISA) analysis. The extra rats were successfully induced with endometriosis and through gene transfer as described above. The spherical volumes of the transplants and tail flick latency post-bombardment after 4, 6, 8, and 10 weeks were measured.
Results: The spherical volumes in the treatment group were much smaller than those in the control group, and tail flick latency significantly increased in the treatment group postbombardment after 2 weeks. The ELISA analysis showed that the concentrations of β-NGF in the serums and supernatants of the peritoneal fluid decreased in the treatment group unlike in the control group. Less sympathetic and sensory innervation was observed in the treatment group postbombardment after 2 weeks. The outcomes of the spherical volumes of the transplants and tail flick latency postbombardment after 4, 6, 8, and 10 weeks showed that the sizes of the transplants did not return to their previous size and that the treatment had some effects on generalized hyperalgesia.
Conclusion: Specific siRNA-mediated silencing of the β-NGF gene expression after gene transfer suppressed the growth of ectopic endometriotic implants resulted in a significant improvement in generalized hyperalgesia as well as reduced sympathetic and sensory nerve fiber density in the treatment group.
Keywords: endometriosis; immunohistochemistry; nerve fibers; nerve growth factor; siRNA.