MALDI TOF IMS - A Tool for Diagnosis of Low-Grade Infection?

Introduction: With the rising success of alloplastic material in implantation surgery, implant-associated complications have increased. One of the most severe complications is infection of the implant. Especially diagnosis of low-grade infections is challenging due to absence of clear clinical signs of inflammation. Often, explantation of the implant and histopathological review of the tissue are required. However, many implants are not sectionable or severely hinder the cutting process of the tissue, resulting in poor sample quality with subsequent difficulties to detect polymorphonuclear granulocytes (PMNs). MALDI TOF IMS may provide additional information to diagnose infection of implants combining histopathological review with mass spectrometry. Material and Methods: In this retrospective study, we analyzed tissue from 15 formalin-fixed and paraffin-embedded (FFPE) surgical hernia explants. The tissues were conventionally stained with hematoxylin and eosin (H&E) and by immunohistochemistry using CD15 to detect PMNs as indicator cells for infections. Areas with high number of PMNs were annotated. Subsequently, MALDI TOF IMS was performed, and specific (m/z) ion peptides were searched as biomarkers for infection. Results and Conclusion: We were able to detect PMN peptides in mesh embedded tissue. Histologically annotated areas with high numbers of neutrophils showed high intensity for the neutrophil-associated peptides. As a proof of principle MALDI TOF IMS can detect PMN peptides across different tissue types and provide additional information for diagnosing low-grade infection in implants. Due to the small sample size further studies are necessary to substantiate the potential of MALDI TOF IMS in diagnosis of low-grade infection.