Determining predictive metabolomic biomarkers of meniscal injury in dogs with cranial cruciate ligament disease

Objectives The objective of this study was to use for the first time proton nuclear magnetic resonance spectroscopy (1H NMR) to examine the metabolomic profile of stifle joint synovial fluid from dogs with cranial cruciate ligament rupture with and without meniscal injuries. We hypothesised this would identify biomarkers of meniscal injury. Methods Stifle joint synovial fluid was collected from dogs undergoing stifle joint surgery or arthrocentesis for lameness investigations at three veterinary hospitals in the North-West of England. Samples underwent 1H NMR spectroscopy and metabolite identification. We used multivariate and univariate statistical analysis to identify differences in the metabolomic profile between dogs with cranial cruciate ligament rupture and meniscal injury, cranial cruciate ligament rupture without meniscal injury, and neither cranial cruciate ligament rupture nor meniscal injury, taking into consideration specific clinical variables. Results 154 samples of canine synovial fluid were included in the study. 64 metabolites were annotated to the 1H NMR spectra. Six spectral regions were found to be significantly altered between groups with cranial cruciate ligament rupture with and without meniscal injury, including three attributed to NMR mobile lipids (mobile lipid -CH3 [p=0.016], mobile lipid -n(CH3)3 [p=0.017], mobile unsaturated lipid [p=0.031]). Clinical Significance We identified an increase in NMR mobile lipids in the synovial fluid of dogs with meniscal injury which are of interest as potential biomarkers of meniscal injury, as well as understanding the metabolic processes that occur with meniscal injury. ### Competing Interest Statement Christine Pye received funding from BSAVA PetSavers to undertake this study as part of an MPhil programme.