The effects of freeze/thawing on human synovial fluid observed by 500 MHz H-1 magnetic resonance spectroscopy

Objective. To investigate the effect of freeze/thaw and low temperature sto rage on the biomolecular profile of human synovial fluid (SF) using high re solution (500 MHz H-1) magnetic resonance spectroscopy (MRS). Methods. SF was collected from 12 patients undergoing arthroscopic debridem ent for treatment of moderate osteoarthritis (OA). Six of the larger sample s were divided into 5 parts and treated as follows: the first was analyzed with spin-echo MRS soon after arthroscopy (less than or equal to 24 h); the 2nd, 3rd, and 4th parts were frozen (-75 degrees C) and thawed for a total of one, 5, and In freeze/thaw cycles, respectively, followed by MRS analys is; the 5th part was kept in -75 degrees C storage for greater than or equa l to 1 year before MRS processing. The 6 smaller samples were divided into 2 parts, the first analyzed shortly after extraction (less than or equal to 24 h), while the 2nd was processed after storage at -75 degrees C for grea ter than or equal to 1 year. Changes in measured metabolite levels were tes ted for significance using paired t tests. Results. Freeze-thaw cycling had no statistically significant effect on the relative concentrations of endogenous metabolites measured by MRS, though it did alter individual sample results. Prolonged low temperature storage r esulted in a significant drop (p < 0.05) in the signal intensities of gluco se (45%), N-acetyl glycoproteins (39%), CH2-chain and CH3-terminal and reso nances of lipoproteins (46 and 37%, respectively), valine (43%), leucine (3 5%), and isoleucine (43%). Conclusion. This study raises questions about routine procedures that may i nadvertently affect the outcomes of quantitative SF analyses. Extended low temperature storage should be avoided as it permanently alters the biochemi cal profile of SF, possibly leading to erroneous conclusions about the natu re of OA related changes in metabolite levels with disease progression.