UC San Diego

Hyaluronan (HA) is a high molecular weight (MW) macromolecule that contributes to the viscoelastic and lubricating properties of synovial fluid (SF), lowering the wear and tear of articular cartilage. HA is secreted and concentrated by the synovium, which acts as a semi- permeable membrane involved in size-selective filtering and retention of SF macromolecules. Joint injury and arthropathies result in changes to SF composition, specifically HA MW and concentration. However, the effect of these changes in SF and HA on the transport of HA across the synovium are unclear. Thus, the objective of this study was to further the understanding of how injury affects HA transport across a semi-permeable membrane using a novel diffusion device. A custom diffusion apparatus was developed and validated to assess the diffusion properties, in terms of time constants and membrane permeabilities, of HA in SF from normal (NL-hSF) and acutely injured (AI-hSF) joints across a 400 nm pore size membrane. The measured permeabilities of polydisperse HA (0.05-7 MDa) in NL-hSF and AI-hSF did not differ for 400 nm pore size membranes. The NL-hSF and AI-hSF solutions had different HA MW distributions. Time constants also did not depend on initial HA concentration. Together, these results suggest that HA MW relative to synovium pore size may have a predominant role in the transport of HA across the synovium, independent of disease state