Quantitative immunohistochemical examination of the local cellular reactions following implantation of biomaterials.

Examining the biocompatibility of implant materials includes the in vivo investigation of the local tissue response following implantation in experimental animals. By contrast to qualitative and semi-quantitative approaches often used in this field, a quantitative technique would facilitate a more accurate determination and better comparability of different studies. Therefore, this study aimed at evaluating the applicability of the free image analysis software ImageJ for fast, easy and reproducible quantification of the tissue response following implantation of titanium samples in rats with subsequent immunohistochemical examination of peri-implant tissue samples for monocytes and macrophages (ED1) and MHC class II positive antigen presenting cells (OX6). The quantification of positively stained cells in the vicinity of the implant pockets was based on a grid-supported manual count carried out using two ImageJ plugins (CellCounter, Grid) and resulted in a mean coefficient of variation of 13.8% (ED1) and 19.6% (OX6) between different investigators and 10.0% (ED1) and 13.8% (OX6) for repeated counting by the same investigator. In conclusion, ImageJ was found to be suitable for morphometric evaluation of the tissue response following implantation, particularly the analysis of discrete cellular events at the tissue-biomaterial interface. The procedure which was used is described in detail, and its advantages and disadvantages are discussed.