In recent years, the development of innovative biomaterials and surgical techniques has led to a progressive increase in joint replacement arthroplasty procedures.
It is well known that all implant metals, in contact with biological fluids, undergo electrochemical and mechanical corrosion, releasing metallic particles that may induce toxic responses and local or systemic inflammatory reactions.
Several studies have demonstrated a possible relationship between particulate wear debris and symptoms of dermatitis and urticaria, but there is no evidence of a direct correlation between wear severity and immune response.
Published results show that the immune reaction changes with individual immunomodulatory status.
The aim of this study was to analyse the proliferative response in the presence of proper stimuli, and to identify possible modifications in the production of a wide range of cytokines, as potential biological markers for early diagnosis of aseptic loosening.
This study analyses the immune response of potentially allergic patients undergoing joint replacement arthroplasty, patients with painful prosthetic joints or joint instability, and subjects without any implants, serving as controls.
In vivo assessment of metal sensitivity includes a standard patch test for hypersensitivity reactions.
Accordingly, a standard patch test for in vivo assessment of metal hypersensitivity reaction, based on the level of allergic response of the skin, was performed.
Blood samples were collected after obtaining informed consent.
Activated lymphocyte proliferation was assessed by counting [3H]-thymidine uptake (3H-TdR).
Peripheral blood mononuclear cells, isolated from heparinised blood samples using standard density gradient centrifugation, were resuspended in RPMI1640 culture medium supplemented with foetal calf serum, L-glutamine, penicillin/streptomycin, and (cultured) incubated at 37°C in 5% CO2, in the presence and absence of scalar concentrations (from 1 to 0.01mM) of chromium, nickel, titanium, cobalt and molybdenum.
Phytohaemagglutinin, a polyclonal mitogen which activates lymphocytes proliferation, was used as positive control. Cells were pulsed for the last 12 hours of culture with 1 μCi of 3H-TdR.
Lymphocyte proliferation, measured in CPM (counts per minutes), was assessed by scintillation counting of incorporated radioactivity; the results were expressed as stimulation index (SI).
Cytokine production in PBMC supernatants was analysed using Luminex LabMAP assay, which measures the concentrations of multiple analytes in the same sample.
Results and Conclusions:
Results of metal sensitivity testing show that:
chromium and nickel at concentrations of 0.1 mM significantly enhanced proliferation of PBMCsisolated from samples of patients submitted to joint replacements, compared with controls.Patients with allergic reactions showed an increased proliferative response to high concentration of nickel.No proliferative response was found in normal control subjects.None of the patients analysed to date showed reactivity to titanium.
The analysis of lymphocyte culture supernatants showed the constant production of chemotactic cytokines, such as IL-8 and MIP1 α and β.
Chromium and nickel significantly modulated production of cytokines, such as IL-8, MIP1 α and β MCP-1, RANTES and PDGF-BB, in patients with joint implants compared with control group.
Some patients showed the presence of cytokines with regulatory activity on cell differentiation and growth, such as IL-2, and the presence of pro-inflammatory macrophage-derived cytokines, such as IL-1.
These preliminary results suggest that there is different involvement of specific cytokines and chemokines responsible for inflammatory reactions, related to different individual responses.