Association of urodynamics and lower urogenital tract nerve growth factor after synthetic vaginal mesh implantation on a rat model

Immunochemical and urodynamic outcomes after polypropylene mesh explant from the pelvic wall of rats

INTRODUCTION AND HYPOTHESIS

To analyze the immunochemical and urodynamic outcomes after partial versus complete excision of transvaginal polypropylene mesh (PPM) from pelvic walls of rats.

METHODS

Forty-eight female Sprague-Dawley (SD) rats were randomly distributed into seven groups: control, mesh total removal 60 days (M-T 60D), mesh total removal 180 days (M-T 180D), mesh partial removal 60 days (M-H 60D), mesh partial removal 180 days (M-H 180D), sham 60 days (Sham 60D), and sham 180 days (Sham 180D). In the mesh groups, PPM was inserted and partially (0.3 × 0.3 cm) or completely removed 30 days later. In the Sham group, the space between the vagina and bladder was dissected without placing or removing the synthetic mesh at day 1 and day 30 later. Urodynamic studies, immunochemical analysis, and Western blot were done at days 60 and 180.

RESULTS

The M-T 60D voiding pressure was significantly decreased compared to the Sham 60D and M-H 60D. The voiding interval of M-T 60D was significantly shorter than that of M-H 60D. In the M-T 60D and M-T 180D groups, the leak point pressure was significantly less than in their corresponding sham groups. IL-1 and TNF-α were significantly more intense in M-T 60D compared to M-H 60D and Sham 60D. NGF was significantly greater in M-T 60D compared to Sham 60D. There were no significant differences in MMP-2 and CD-31s throughout the group.

CONCLUSION

Total mesh excision incites a host inflammatory response and transitory lower urinary tract dysfunction. Despite the good outcomes after total excision, the invasiveness and surgical risk associated with repeated procedures should not be underestimateded.

Immunochemical analysis on polypropylene mesh: does mesh size make a difference?

INTRODUCTION AND HYPOTHESIS

The aim of the study is to demonstrate the impact of the size of implanted mesh in relation to its immunohistochemical reaction implanted into animal models.

METHODS

An experimental study utilizing 54 female Sprague Dawley (SD) rats was divided into five groups: control, sham, and study groups (mesh-small [M-S], mesh-medium [M-M], mesh-large [M-L]). The M-S group used a mesh size of 0.2 × 0.2 cm, the M-M group a mesh size of 0.5 × 0.5 cm, and the M-L a mesh size of 0.7 × 1.0 cm. The sham group underwent vaginal dissection with no mesh implantation. The rats were sacrificed using isoflurane overdose on days 7 and 30. The mesh with the surrounding vaginal and bladder wall tissues were removed and processed for histochemical and western blot analysis.

RESULTS

There is a significant increase in IL-1 and TNF-α immunoreactivity in the M-M and M-L groups on day 7 when compared with the sham group with p values of 0.001 and < 0.001 respectively. M-L showed significantly higher immunoreactivity to TNF-α persisting until day 30. All study groups presented a significantly higher immunoreactivity to MMP-2 and NGF on day 7. However, reactivity to NGF does not persist to day 30 in all groups. Immunoreactivity to CD 31 on days 7 and 30 appears significantly greater in the M-M and M-L groups, with the reaction in the M-L group continuing until day 30.

CONCLUSION

Mesh size is directly proportional to the inflammatory reaction in the host tissue. The prolonged inflammatory process leads to delayed tissue remodeling and angiogenesis, which could delay mesh-tissue integration.

Dissecting of the paravesical space associated with lower urinary tract dysfunction - a rat model

To determine the association of opening the paravesical space in relation to its occurrence of de novo SUI in an animal model. Thirty five female Sprague Dawley rats were divided into 5 groups of 7 rats each: Control group, Sham groups(F, H), and Study groups(MF, MH). Groups labeled with "F" had the paravesical space opened, "H" had tissue dissection with no opening of the space, and "M" had mesh implanted inside the vaginal wall. Urodynamic studies, immunohistochemical analysis, and western blot were done at day 40. The mean weight and age of 35 rats were 302.1 ± 25.1 grams and 12.8 ± 1.2 weeks old. No significant differences were noted among the control, Sham F, Sham H, Study MF, and Study MH on the voiding pressure and voided volume. The Sham F and Study MF (opened paravesical space) groups had significantly lower values on leak point pressures (LPP) (p = 0.026; p < 0.001) and shorter voiding intervals (p = 0.032; p = 0.005) when compared to other groups. Immunohistochemical analysis showed IL-1 and TNF-α to be intensely increased for the Study MF group (p = 0.003; p = <0.001). MMP-2 and CD 31 markers were also significantly higher in the Study MH and MF group. NGF expression was significantly increased in the Study MF and Sham F groups. Thus, opening of the paravesical space causes an increased inflammatory reaction, which leads to tissue destruction and lower urinary tract dysfunction, exemplified in the study with low leak point pressure and shortened voiding intervals.

Managing female pelvic floor disorders: a medical device review and appraisal

Pelvic floor disorders (PFDs) will affect most women during their lifetime. Sequelae such as pelvic organ prolapse, stress urinary incontinence, chronic pain and dyspareunia significantly impact overall quality of life. Interventions to manage or eliminate symptoms from PFDs aim to restore support of the pelvic floor. Pessaries have been used to mechanically counteract PFDs for thousands of years, but do not offer a cure. By contrast, surgically implanted grafts or mesh offer patients a more permanent resolution but have been in wide use within the pelvis for less than 30 years. In this perspective review, we provide an overview of the main theories underpinning PFD pathogenesis and the animal models used to investigate it. We highlight the clinical outcomes of mesh and grafts before exploring studies performed to elucidate tissue level effects and bioengineering considerations. Considering recent turmoil surrounding transvaginal mesh, the role of pessaries, an impermanent method, is examined as a means to address patients with PFDs.