Objective: This study aimed to investigate specific inflammatory pathomechanisms, i.e. the expression of the stem cell factor receptor KIT (CD117) in tissue specimens from patients with aseptic hip prosthesis loosening (AHPL) with special emphasis on colocalization with the mast cell specific marker tryptase.
Methods: Immunohistochemical analysis of CD117 was performed in tissue specimens from 10 patients with aseptically loosened acetabular components of failed non-cement total hip replacements and compared to control samples obtained at primary hip surgery (n=4). The CD117 expressing cells were characterized further with mast cell tryptase (MCT) by serial section analysis and a double staining method. CD117 and MCT expression was examined by semi-quantitative analysis. Additionally, double labeling of the CD117 or MCT expression by immunohistochemistry and of polyethylene (PE) particles by Oil Red reaction was performed.
Results: In AHPL, CD117 was almost exclusively detected in MCT positive cells. Co-expression tended to be highly correlated (r=0.86, p<0.01). CD117 was found mainly in two regions: first, in perivascular lymphocyte-rich areas and; secondly, near macrophages and multinucleated giant cells (MGC). PE particles were not detected in CD117 and MCT positive cells. In control samples, CD117/MCT positive cells were less frequent.
Conclusion: This is the first report on CD117 expression in AHPL. CD117 is almost exclusively expressed in a distinct mast cell subgroup. As an important growth factor receptor, CD117 could play a major role in recruitment and activation of mast cells in AHPL. Furthermore, mast cells do not contain significant amounts of PE particles. However, it remains to be investigated whether this cell population could influence phagocytosis of PE particles. (Journal of Applied Biomaterials and Biome-chanics 2005; 3: 11-7).