Poster P1 - Whole Transcriptome Analysis of the Tissue-Mesh Interface in Ventral Hernia Recurrence

Introduction: The abdominal wall comprises various layers including the skin, fat tissue, abdominal muscles, fascia, and peritoneum1. Abnormalities in this structure can lead to hernias, which are often repaired using surgical meshes. Ventral hernia repair (VHR) is a common procedure, with over 600,000 procedures perform every year in the US2. However, high recurrence rates and mesh-related complications persist. Understanding long-term interactions at the mesh-tissue interface is crucial for improving mesh design and patient outcomes. High-throughput transcriptomics, such as RNA-sequencing (RNA-seq) can identify gene expression changes, aiding in the development of safer and more effective mesh implants.

Materials and

Methods: Abdominal wall tissue samples of 1.0 cm2 were collected from patients undergoing a secondary VHR. Samples from locations proximal or distal to the tissue-mesh interface were separately processed for RNA extraction using TRIzol. RNA samples were treated with DNAse I and quantified using a Bioanalyzer 2100. Samples with RNA integrity numbers (RINs) ≥ 5 were selected for library preparation and RNA-seq. Ribosomal RNA was depleted using NEBNext rRNA depletion kit, and stranded RNA libraries were prepared. Sequencing was performed on an Illumina Novaseq 6000 SP using 150 paired ends. Raw reads were trimmed for quality and adapters removed. HISAT (V.2.2.1) was used for the alignment, and gene expression counts were obtained using featureCounts (v.2.0.3). Differential expression analysis was performed using Limma-Voom with an adjusted p-value threshold of ≤ 0.1, and a log2-fold-change cutoff of ≥ 0.58. To explore the biological significance of the differentially expressed genes (DEGs), functional enrichment analysis was performed using gene ontology (GO) available in the R package ClusterProfiler.

Results, Conclusions, and Discussions: We detected the expression of 18,165 genes, with 6.6% of these genes being differentially expressed. Tissue samples proximal to the mesh-tissue interface showed down-regulation of 684 genes and the up-regulation of 532 compared to tissue samples distal from the mesh (Figure 1A). For the set of up-regulated genes in the proximal samples, we found the enrichment of different GO categories related to immune response, including lymphocyte differentiation, proliferation, and mediated immunity; T cell differentiation and activation; mononuclear cell differentiation and proliferation; B cell activation; and cytokine production, among others. On the other hand, we observed that the down-regulated genes were associated with muscle contraction, development, assembly, and metabolic processes related to ATP and oxidation for energy generation, among others (Figure 1B).

Conclusions
The goal of this hypothesis-generating study was to identify unique gene expression patterns at the hernia mesh-tissue interface in patients with prior VHR. Our results indicate that there is an immunological response involving inflammation and downregulation of normal cellular processes at this interface, possibly explaining the underlying reason for the VHR reoccurrence. Addressing this knowledge gap will help inform researchers, clinicians, and industry stakeholders on the creation of safer, more durable mesh implants for VHR.

References
1. Seeras, K., Qasawa, R.N., Ju, R. & Prakash, S. in StatPearls (StatPearls Publishing
Copyright © 2023, StatPearls Publishing LLC., Treasure Island (FL); 2023).
2. Schlosser, K.A., Renshaw, S.M., Tamer, R.M., Strassels, S.A. & Poulose, B.K. Ventral hernia repair: an increasing burden affecting abdominal core health. Hernia 27, 415-421 (2023).

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