Impact of Extracellular Vesicles Coating on Mesh in a Rat Model: Pilot Study

Objectives: Within Urogynecology, the use of polypropylene mesh for surgical repair has enhanced the durability of patient outcomes. Complications involving mesh have a profound impact. Mesh removed secondary to complications have been shown to exhibit significant levels of MMP-2, MMP-9 (markers of tissue degradation) and IL-10 (anti-inflammatory cytokine). The present study aimed to evaluate the immunohistochemical response to mesh coated with stem cell derived extracellular vesicles (EVs) in a rat model. To achieve this, the expression of MMP-2, MMP-9 and IL-10 was quantified to understand their role in the immune response.

Methods: Rat adipose derived stem cells were cultured followed by EVs isolation using ultracentrifugation. A nanoparticle tracking analysis was performed to derive the particle size and quantify the EVs, which were then mixed with an alginate hydrogel and coated onto mesh prior to implantation. Twenty-eight female Sprague-Dawley rats were assigned to 3 groups: sham (n=4), control (mesh coated with alginate hydrogel, n=12) and study group (mesh coated with alginate hydrogel and EVs, n=12). Each group was divided further into sacrifice at 2- and 6 weeks post-op. Two mesh samples (20 x 11mm) of the same condition were implanted in the subcutaneous space on the dorsum. After sacrifice, MMP-2, MMP-9 and IL-10 staining was performed for immunohistochemical analysis. Using ImageJ, the percent relative expression of uptake was measured. Statistical analysis was performed using ANOVA, which was confirmed with a post hoc analysis of multiple comparisons with a Bonferroni adjustment.

Results: In 28 rats, there were 48 mesh samples implanted and 8 sham surgeries performed. In assessing the averaged MMP-2 relative percent expression at 6 weeks, the investigational group was significantly reduced compared to control and sham groups (p=0.0061), which was confirmed with a post hoc analysis (Bon. Adj p< 0.001) (Figure 1). There were trends revealing a reduction in MMP-2 and MMP-9 levels compared to control and sham groups at both time points, although not significant. The EV coated meshes had elevated IL-10 levels compared to the others. At 2 weeks, there was no significant difference in MMP-2, MMP-9 or IL-10 in either of the groups respectively (p=0.7551, p=0.4391, p=0.7998). For MMP-9 and IL-10 at 6 weeks, there was no significant difference between any group (p=0.1165, p=0.7685).

Conclusions: In this pilot study, implantation of mesh coated with EVs demonstrated a positive impact on the immune response within rats. Specifically, a reduction in MMP-2 expression at 6 weeks post-op supports our hypothesis that EVs have the potential to reduce the immune response and subsequently protect against mesh complications. Future studies should further investigate the potential clinical applications of EV-coated meshes in a larger animal model and increased sample sizes.