Quantitative Histopathology for Evaluation of In Vivo Biocompatibility Associated with Biomedical Implants

In the current chapter, digital morphometric analysis (DMA) was used to quantify two markers of biocompatibility around commonly used biomaterials. In the field of biomaterial evaluation for biocompatibility, more sophisticated methods are now being used to precisely characterize the elicited response from the surrounding tissue towards the implanted material. One reason for this is due to the fact that many newer biomaterial innovations are incorporating pharmaceutical agents (e.g., drug eluting stents and drug eluting balloons). Therefore, as described in many of the other chapters in this book, components of toxicology and pharmacology are being evaluated along with biocompatibility. In this chapter, expanded polytetrafluoroethylene (ePTFE) was compared to polypropylene (PP) for inflammatory and foreign body response. Each material was implanted into dorsal subcutaneous spaces and evaluated after 2, 4, and 12 weeks. Each sample was reacted with an antibody to cluster of differentiation-68 (CD-68). The resulting slides were scanned and evaluated using DMA in order to obtain accurate, reproducible, and consistent results. Expanded PTFE demonstrated a lower overall weighted inflammatory score when compared to PP across all timepoints. This chapter describes the use of DMA as a novel approach to measure the inflammatory score that is associated with a specific biomaterial. Current and future medical devices will need to use various analytical tools to comprehensively assess device, biomaterial, or a combination therapy’s biocompatibility. The next chapter further describes how quantitative data from histology and immunohistochemistry assessments can be coupled with quantitative polymerase chain reactions (PCR) as assessment tools for product development.