Macrophage Interactions with Decellularized Heart Valve Materials: Influence of Crosslinking Treatment

Abstract

While macrophages have been implicated in the failure of bioprosthetic heart valves, there is no current literature on the macrophage response to crosslinked, native collagen. Using decellularized bovine pericardium (DBP) as a model, this study investigates the response of macrophage-like cells (U937s) to untreated DBP and DBP under two chemical crosslinking techniques: glutaraldehyde (GLUT) and an alternative zero-length crosslinker 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). U937 cells were seeded and differentiated directly on the material surfaces. At 72 h after differentiation, the samples were fixed for SEM as well as analyzed for acid phosphatase activity, cytokine and matrix metalloproteinase release, all normalized to the number of live, adherent cells via DNA analysis. The U937 cells on the GLUT surface showed an abnormal morphology not seen on the other surfaces. These cells released more pro-inflammatory cytokines, and less MMP-2 and MMP-9 than occurred under EDC treatment or in untreated DBP. The results suggest that host inflammatory cells react to the crosslinking state of the DBP, perhaps as a non-specific response.