Cell-coating affects tissue integration of synthetic and biologic meshes: comparative analysis of the onlay and underlay mesh positioning in rats

Background: While mesh reinforcement is recognized as the optimal strategy for many hernia repairs, there remains debate on the optimal position for deployment and characteristics that lead to improved biocompatibility. Coatings are an avenue by which integration may be improved. Our aim was to evaluate tissue integration between uncoated, fibroblast- and mesenchymal stem cell-coated meshes placed as subcutaneous onlay (ON) or intraperitoneal underlay (UN). Methods: Three commonly used biologic and synthetic hernia meshes were tested including Parietex, TIGR and Strattice. Each mesh was coated with rat kidney fibroblasts (NRKs) or rat mesenchymal stem cells (MSCs) along with an uncoated group. In the ON group, mesh was fixated on top of the external oblique fascia. In the UN group, mesh was placed against the intact peritoneum. Animals were survived for 30 days and killed for biomechanical and histologic analysis. A “T”-peel test was performed on a mesh–tissue explant from each sample to analyze the strength of integration at the mesh–tissue interface. Tissue integration was evaluated histologically using an established scoring system. Results: All uncoated meshes demonstrated significantly higher tissue ingrowth in the UN compared to ON position. Cell-coating of synthetic meshes decreased tissue ingrowth as UN, but increased it as ON, with a net effect of minimizing biomechanical difference between the two positions. In the biologic group however, NRK-coating decreased tissue ingrowth regardless of position, while MSC-coating increased it in both ON and UN positions. Conclusions: Both cell-coating and positioning affect mesh–tissue integration. Integration is superior in the underlay position compared to onlay when uncoated. Cell-coating of selected synthetic meshes can improve integration, particularly in the onlay position. Furthermore, MSCs appear to be a viable choice for biologic mesh coating, especially when implanted as an onlay. Overall, cell-coating of surgical meshes appears to a have a potential to improve mesh–tissue integration.