Evaluating the porcine dermis graft InteXen® in three-compartment transvaginal pelvic organ prolapse repair

Two-Year Preclinical Evaluation of Long-Term Absorbable Poly-4-hydroxybutyrate Scaffold for Surgical Correction of Pelvic Organ Prolapse

INTRODUCTION AND HYPOTHESIS

Fully absorbable implants may be an alternative to permanent meshes in the correction pf pelvic organ prolapse (POP) as they may reduce adverse events by promoting tissue regeneration and collagen metabolism. This study was aimed at evaluating the long-term host and biomechanical response to a fully absorbable poly-4-hydroxybutyrate (P4HB) scaffold in comparison with polypropylene (PP) mesh.

METHODS

Poly-4-hydroxybutyrate scaffold (n = 16) and PP mesh (n = 16) were surgically implanted in the posterior vaginal wall of parous female Dohne Merino sheep. Vaginal explants were evaluated in terms of gross necropsy, host response (immune response, collagen deposition, tissue regeneration), biomechanics, and degradation of P4HB at 12 and 24 months post-implantation.

RESULTS

Gross necropsy revealed no infection or fluid collection using P4HB or PP. At 12 months, exposures were observed with both P4HB (3 out of 8) and PP (4 out of 8), whereas at 24 months, exposures were observed only with PP (4 out of 8). The tensile stiffness of the P4HB explants was maintained over time despite complete absorption of P4HB. The collagen amount of the vaginal tissue after P4HB implantation increased over time and was significantly higher than PP at 24 months. P4HB scaffolds exhibited significantly lower myofibroblast differentiation than PP meshes at 24 months.

CONCLUSIONS

The P4HB scaffold allowed for gradual load transfer to the vaginal wall and resulted in mechanically self-sufficient tissue. P4HB scaffold had a more favorable host response than PP mesh, with higher collagen content, lower myofibroblastic differentiation, and no exposures at 24 months. P4HB scaffolds have potential as an alternative to permanent implants in treating POP.

Role of Fibroblasts and Myofibroblasts on the Pathogenesis and Treatment of Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is a multifactorial connective tissue disorder caused by damage to the supportive structures of the pelvic floor, leading to the descent of pelvic organs in the vagina. In women with POP, fibroblast function is disturbed or altered, which causes impaired collagen metabolism that affects the mechanical properties of the tissue. Ideal surgical repair, either native tissue repair or POP surgery using an implant, aims to create a functional pelvic floor that is load-bearing, activating fibroblasts to regulate collagen metabolism without creating fibrotic tissue. Fibroblast function plays a crucial role in the pathophysiology of POP by directly affecting the connective tissue quality. On the other hand, fibroblasts determine the success of the POP treatment, as the fibroblast-to-(myo)fibroblast transition is the key event during wound healing and tissue repair. In this review, we aim to resolve the question of “cause and result” for the fibroblasts in the development and treatment of POP. This review may contribute to preventing the development and progress of anatomical abnormalities involved in POP and to optimizing surgical outcomes.

Evaluation of the short-term host response and biomechanics of an absorbable poly-4-hydroxybutyrate scaffold in a sheep model following vaginal implantation

Objective

To evaluate the host‐ and biomechanical response to a fully absorbable poly‐4‐hydroxybutyrate (P4HB) scaffold in comparison with the response to polypropylene (PP) mesh.

Design

In vivo animal experiment.

Setting

KU Leuven Center for Surgical Technologies.

Population

Fourteen parous female Mule sheep.

Methods

P4HB scaffolds were surgically implanted in the posterior vaginal wall of sheep. The comparative PP mesh data were obtained from an identical study protocol performed previously.

Main outcome measures

Gross necropsy, host response and biomechanical evaluation of explants, and the in vivo P4HB scaffold degradation were evaluated at 60‐ and 180‐days post‐implantation. Data are reported as mean ± standard deviation (SD) or standard error of the mean (SEM).

Results

Gross necropsy revealed no implant‐related adverse events using P4HB scaffolds. The tensile stiffness of the P4HB explants increased at 180‐days (12.498 ± 2.66 N/mm SEM [p =0.019]) as compared to 60‐days (4.585 ± 1.57 N/mm) post‐implantation, while P4HB degraded gradually. P4HB scaffolds exhibited excellent tissue integration with dense connective tissue and a moderate initial host response. P4HB scaffolds induced a significantly higher M2/M1 ratio (1.70 ± 0.67 SD, score 0–4), as compared to PP mesh(0.99 ± 0.78 SD, score 0–4) at 180‐days.

Conclusions

P4HB scaffold facilitated a gradual load transfer to vaginal tissue over time. The fully absorbable P4HB scaffold, in comparison to PP mesh, has a favorable host response with comparable load‐bearing capacity. If these results are also observed at longer follow‐up in‐vivo, a clinical study using P4HB for vaginal POP surgery may be warranted to demonstrate efficacy.

Tweetable Abstract

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Fully absorbable poly-4-hydroxybutyrate implants exhibit more favorable cell-matrix interactions than polypropylene

Pelvic organ prolapse (POP) is a multifactorial condition characterized by the descent of the pelvic organs due to the loss of supportive tissue strength. This is presumably caused by the decreased fibroblast function and the subsequent change in the quality of the extracellular matrix. The correction of POP using an implant intends to provide mechanical support to the pelvic organs and to stimulate a moderate host response. Synthetic polypropylene (PP) implants were commonly used for the correction of prolapse. Although they were successful in providing support, these implants have been associated with clinical complications in the long term due to substantial foreign body response and inappropriate tissue integration. The complications can be avoided or minimized by engineering a biocompatible and fully absorbable implant with optimized mechanical and structural characteristics that favor more appropriate cellular interactions with the implant. Therefore, in this study, we evaluated implants comprised of poly-4-hydroxybutyrate (P4HB), a fully absorbable material with high mechanical strength, as an alternative to PP. The P4HB implants were knitted in four unique designs with different pore shapes ranging from a more rectangular geometry- as it is in PP implant- to a rounded geometry, to determine the effect of the implant structure on the textural and mechanical properties and subsequent cell-matrix interaction. The cellular response was investigated by seeding primary vaginal fibroblasts isolated from patients with POP. P4HB favored cellular functions more than PP, as indicated by greater cell attachment and proliferation (P < 0.01), and significantly more collagen deposition (P4HB vs PP, 11.19 μg vs 6.67 μg) at 28 days culture (P < 0.05). All P4HB implants had higher strength and lower stiffness than the PP scaffold. The material and the design of the implant also influenced the behavior of vaginal fibroblasts. The aspect ratio of the vaginal POP fibroblasts cultured on the PP implant (1.61 ± 0.75) was significantly (P < 0.005) smaller than those cultured on P4HB implants (average 2.31 ± 0.09). The P4HB structure with rounded pores showed the lowest stiffness and highest fibroblast attachment and proliferation (P < 0.01). Overall, P4HB induces more matrix deposition compared to PP and knit design can further optimize cell behavior.

Surgery for Apical Vaginal Prolapse after Hysterectomy: Transvaginal Mesh-Based Repair

Several transvaginal mesh products have been marketed to address vaginal vault prolapse. Although data are limited, prolapse recurrence rates and subjective outcome measures seem to be equivalent for vaginal mesh compared with native tissue apical prolapse repair, and the different vaginal meshes have not proven superior to one another. Given the known unique complications specific to vaginal mesh with equivalent outcomes for the apical vaginal prolapse, it is reasonable to reserve mesh use for specific high-risk cases, such as patients with large apical prolapse recurrence after native tissue repair who are not candidates for sacrocolpopexy.

Graft and Mesh Use in Transvaginal Prolapse Repair: A Systematic Review

OBJECTIVE

To update clinical practice guidelines on graft and mesh use in transvaginal pelvic organ prolapse repair based on systematic review.

DATA SOURCES

Eligible studies, published through April 2015, were retrieved through ClinicalTrials.gov, MEDLINE, and Cochrane databases and bibliography searches.

METHODS OF STUDY SELECTION

We included studies of transvaginal prolapse repair that compared graft or mesh use with either native tissue repair or use of a different graft or mesh with anatomic and symptomatic outcomes with a minimum of 12 months of follow-up.

TABULATION, INTEGRATION, AND RESULTS

Study data were extracted by one reviewer and confirmed by a second reviewer. Studies were classified by vaginal compartment (anterior, posterior, apical, or multiple), graft type (biologic, synthetic absorbable, synthetic nonabsorbable), and outcome (anatomic, symptomatic, sexual function, mesh complications, and return to the operating room). We found 66 comparative studies reported in 70 articles, including 38 randomized trials; quality of the literature has improved over time, but some outcomes still show heterogeneity and limited power. In the anterior vaginal compartment, synthetic nonabsorbable mesh consistently showed improved anatomic and bulge symptom outcomes compared with native tissue repairs based on meta-analyses. Other subjective outcomes, including urinary incontinence or dyspareunia, generally did not differ. Biologic graft or synthetic absorbable mesh use did not provide an advantage in any compartment. Synthetic mesh use in the posterior or apical compartments did not improve success. Mesh erosion rates ranged from 1.4-19% at the anterior vaginal wall, but 3-36% when mesh was placed in multiple compartments. Operative mesh revision rates ranged from 3-8%.

CONCLUSION

Synthetic mesh augmentation of anterior wall prolapse repair improves anatomic outcomes and bulge symptoms compared with native tissue repair. Biologic grafts do not improve prolapse repair outcomes in any compartment. Mesh erosion occurred in up to 36% of patients, but reoperation rates were low.

Anterior colporrhaphy compared with collagen-coated transvaginal mesh for anterior vaginal wall prolapse: a randomised controlled trial

OBJECTIVE

To investigate the anatomical cure rate and complications related to collagen-coated mesh for cystocele, compared with a conventional anterior colporrhaphy.

DESIGN

A randomised controlled study.

SETTING

Six departments of obstetrics and gynaecology in Norway, Sweden, Finland, and Denmark.

POPULATION

Women aged 55 years or older, referred for surgery with a prolapse of the anterior vaginal wall of stage 2 or higher.

METHODS

Women scheduled for primary cystocoele surgery were randomised to either anterior colporrhaphy or a collagen-coated Prolene mesh. Power analysis indicated that 130 patients had to be randomised. All patients were evaluated using the Pelvic Organ Prolapse-Quantification (POP-Q) measurement. Quality of life, symptoms, and sexual function were evaluated using the Pelvic Floor Impact Questionnaire, the Pelvic Floor Distress Inventory, and the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire.

MAIN OUTCOME MEASURES

The primary outcome was objective cure, defined as prolapse below POP-Q stage 2 at the 12-months follow-up. Secondary outcomes were quality of life, symptoms, and presence (or not) of complications.

RESULTS

In total, 161 women were randomised to either anterior colporrhaphy or mesh (participant ages 64.9 ± 6.4 years versus 64.7 ± 6.6 years, respectively; mean ± SD). The objective cure rate was 39.8% (95% CI 28.6-50.9%) in the anterior colporrhaphy group, compared with 88.1% (95% CI 80.7-95.6%) in the mesh group (P < 0.001). Vaginal mesh exposure occurred in ten women (13.3%) and dyspareunia occurred in two women (2.7%, not significant) in the mesh group at the 12-months follow-up. Questionnaires revealed no difference between the groups.

CONCLUSIONS

Our study demonstrates a significantly improved objective cure rate associated with a high exposure rate among women with mesh surgery as opposed to conventional surgery.