Synovial fluid cell isolation protocol affects immune cell recovery and composition across inflammatory states
Authors' conclusion
SFMC isolation excluded low-grade inflammatory samples, introducing bias and reducing statistical power. WSFC-based approaches with hyaluronidase or repeated centrifugation improved recovery and are therefore recommended for synovial fluid immunoprofiling studies.
Study context
- Population
- Synovial fluid samples with volumes>2 mL across inflammatory statessynovial fluid samples, nineteen paired samples underwent deep immunophenotyping, rheology assessed in an additional 23 samples · deep immunophenotyping nineteen · rheology (additional samples) 23
- Participants
- 48 samples
- Comparison
- Whole synovial fluid cells (WSFCs), with and without hyaluronidase vs synovial fluid mononuclear cells (SFMCs) by density-gradient centrifugation
- Outcome
- Cell recovery and sample loss
Methodological detailspaired cell isolation, 31-marker spectral flow cytometry panel with dimensionality reduction and unsupervised clustering
- Paired cell isolation
- 31-marker spectral flow cytometry panel with dimensionality reduction and unsupervised clustering
Main finding
As reported in the abstract
- WSFC isolation yielded higher cell recovery and lower sample loss than SFMC isolation, with differences varying with inflammation level
Further findings
Sample inclusion rate reduction with SFMC isolation
- Low-grade inflammatory samples
- 50%
- High-grade inflammatory samples
- 10%
Cell recovery and synovial fluid viscosity
- Cell recovery correlated with synovial fluid viscosity
Repeated centrifugation vs hyaluronidase
- Repeated centrifugation alone matched the cell recovery seen with hyaluronidase treatment
Immune-cell composition
- WSFCs were enriched for CD8+, CD4+ and γδ T cells, while SFMCs contained higher proportions of dendritic cells and classical monocytes
- Both methods stratified samples by inflammation, but WSFCs provided superior cellular resolution
Original publication
Synovial fluid cell isolation protocol affects immune cell recovery and composition across inflammatory states. RMD Open. Published 23 October 2026. doi:10.
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