Assessing osteolysis with use of high-throughput protein chips

Background: Previous studies of bone resorption around failed joint replacements have focused on a limited number of cytokines, primarily tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1, and IL-6, with use of enzyme-linked immunosorbent assay and immunohistochemistry techniques. In this study, we utilized high-throughput protein chips to profile twenty-nine inflammatory cytokines around failed total joint replacements. Methods: Peri-implant granulomatous tissues were harvested from around the failed total hip prostheses of thirteen patients. Synovial lining capsular tissues from thirteen patients with end-stage degenerative joint disease were used as controls. After homogenization, twenty-nine cytokines were quantified with use of high-throughput protein chips. Results: IL-6 and IL-8 were found consistently in failed joint replacement tissues, reaffirming their prominent role in osteoclastogenesis and end-stage bone resorption. High levels of interferon-gamma-inducible protein of 10 kDa (IP-10) and monokine induced by interferon-gamma (MIG), both chemoattractants of activated Th1 lymphocytes, were also detected. Soluble intercellular adhesion molecule (sICAM) and transforming growth factor-beta 1 (TGF-beta(1)) were not detected universally, nor were TNF-alpha or IL-1. After a twenty-four-hour organ culture, IL-1 beta levels increased substantially along with those of other mediators. We measured but did not detect any activators of cytotoxic T-cells, antibody-producing B-cells, or eosinophils involved in delayed-type hypersensitivity. Variations from patient to patient were seen across all cytokines and highlight the unique response of individual patients to their joint replacements. Conclusions: In failed total joint replacements in patients with end-stage osteolysis, IL-6 and IL-8 may be the primary drivers of osteoclastogenesis. The presence of IP-10 and MIG imply a role for T-cells, while TGF-beta(1), and sICAM may represent a systemic attempt to modulate the inflammation. TNF-alpha and IL-1 do not appear to play a major role in the end stages of the disease. Clinical Relevance: These results demonstrate that proteomic tools can provide a foundation for understanding the cytokine-driven osteolysis cascade and a base from which to identify and evaluate potential targets for blockage or augmentation.