Characterisation of monocyte migration potential in response to stimuli from human arthroplasty revision xenograft transplanted in a NOD-SCID mouse model

Abstract

Monocyte migration into periprosthetic tissue in response to wear debris-induced inflammation factors (WDIF) has been identified as one of the primary contributors to the progression of osteolysis in aseptic loosening (AL) of arthroplasty implants. However, the dynamics of monocyte migration in response to WDIF-derived mediators remains to be fully characterised. This study characterise the migration potential of human monocytes from three cohorts: healthy controls, stable arthroplasty patients, and those undergoing revision surgery for aseptic loosening (AL), in response to stimuli derived from periprosthetic osteolysis (PPOL) tissue. Blood donors: normal (n = 6), stable arthroplasty (n = 6), and revision arthroplasty surgery due to AL (n = 6) were recruited. Peripheral blood samples were collected, and PBMNC-monocytes were isolated. PBMNC-monocyte migration assays in response to revision tissue-conditioned media (RTCM) were conducted, using serum-free media (SFM) and monocyte chemoattractant protein-1 (MCP-1) as negative and positive controls, respectively. Migrated PBMNC-monocytes were assessed using light microscopy and flow cytometry analysis for subtype classification. Subsequently, PPOL tissues were transplanted in NOD-SCID mice (n = 6), with normal synovium tissue (NST) from trauma patients incorporated as a baseline control. Following the intravenous injection of PKH26-labelled cells into transplanted mice, fluorescence signals were tracked non-invasively to monitor their preferential accumulation. The mice were subsequently euthanised at 72 h post-injection and transplanted tissues and mouse organs (liver, kidney, lung, spleen, heart) were harvested and analysed. Data analysis was conducted with SPSS analysis, where p < 0.05 indicates statistical significance. The migrated cell count, specifically classical monocytes CD14 ++ CD16 - percentage count from stable (1.6-fold) and revision arthroplasty (1.5-fold) patients was significantly higher ( p < 0.05) in response to RTCM, as compared with SFM. In vivo results demonstrated the accumulation of injected PKH26-labelled cells, with the highest fluorescence signals detected at 72-h post-injection. Ex vivo imaging revealed significantly higher signals within PPOL ( p < 0.05) compared to other harvested tissues. The findings suggest that WDIF influence migration potential of CD14 + monocytes, suggesting their involvement in AL progression. This outcome suggests the potential application of monocytes as a biomarker candidate to monitor the progression of AL of the arthroplasty implant. Given the significant role of monocytes in AL, further research is warranted to explore the pharmaceutical interventions aiming to halting or mitigating AL progression.