BEST BASIC SCIENCE PAPER: Proteomic Analysis of Mesh Complications Compared to Control Biopsies

Objectives: To determine differences in vaginal proteomic profiles between women with mesh exposure and mesh-related pain compared to controls.

Methods: Study samples were from an active Mesh Biorepository of patients undergoing vaginal polypropylene mesh excision. To minimize variability, samples were eligible for random selection if they were 30-80 years old, BMI < 40 kg/m2 and parous. 10 well-integrated mesh samples (removed incidentally or well away from the site of complication), 10 mesh exposure samples, 10 mesh-pain samples and 10 control vaginal biopsies of patients without mesh underwent proteomic analysis. Samples were lysed, digested, and normalized to 50µg total protein. Nano-scale liquid chromatographic tandem mass spectrometry yielded 30,588 peptide sequence from 2,803 protein groups. One well-integrated sample and one exposure sample were excluded due to predominance of hemoglobin. Differentially expressed proteins were determined (p < 0.05 adjusted for false discovery rate) and gene ontology enrichment analysis was performed to determine differences between mesh groups (adjusted p< 0.05). Then a hypothesis-driven assessment of 100 a priori specified proteins was performed (R, Vienna, Austria).

Results: Mean age was 51.9±6.9 years for patients with exposure, 49.1±13.6 pain group, 62.1±12.5 well-integrated mesh group, and 41.5±6.2 control biopsies (p < 0.05 well-integrated and control biopsies only). Mean BMI was 28.0±5.5 kg/m2 and median duration of implantation was 4.5±5.7 years (p >0.05). All patients were white and one patient in the exposure group was of Hispanic/Latinx ethnicity. 7852 peptides were differentially expressed in exposure compared to control; 5330 pain vs control, 5320 well-integrated vs control (Figure 1A). Only 13 peptides were differentially expressed between pain and exposure, primarily keratins and cell adhesion/scaffolding proteins, all of which had increased expression in exposure patients. Of the 100 proteins specified a priori, 25 were identified in the dataset and 18 were statistically different between groups. Extracellular remodeling proteins MMP9, TIMP3, and SPARC and neutrophil activation proteins, s100A12 and neutrophil defensin 3, showed the greatest deviation from controls (Figure 1B). Gene Ontology enrichment analysis between exposure and well-integrated mesh groups revealed enrichment in terms related to immunity, response to stress, cell proliferation and mobility, apoptosis, and inflammatory and fibrosis mediators (Figure 2A). Pain vs integrated mesh ontology groups were primarily related to collagen fibril organization and cartilage development (Figure 2B) while only morphogenesis of an epithelium and cornification were different between pain and exposure (Figure 2C). Heat maps revealed individual differences in genes within an ontology group, with exposure demonstrating a proinflammatory environment (Figure 2D).

Conclusions: Polypropylene mesh alters the local environment , particularly proteins related to extracellular remodeling and inflammation. Patients with exposure have high levels of epithelial remodeling compared to patients with pain alone, perhaps in an attempt to heal a chronic wound. Impact of age and neutrophil recruitment are planned for future studies.