Comparison of differential biomarkers of osteoarthritis with and without posttraumatic injury in the Hartley guinea pig model

The objective was to compare biomarkers of articular cartilage metabolism in synovial fluid from Hartley guinea pig knees, with and without anterior cruciate ligament transection (ACLT), to establish whether detectable differences in biomarker levels exist between primary and secondary osteoarthritis (OA). Synovial fluid lavages and knees were obtained from 3‐month (control group) and 12‐month (primary OA group) animals. Another group of animals (posttraumatic OA group) underwent unilateral ACLT at 3 months, and samples were obtained 9 months postsurgery. Synovial fluid concentrations of stromal cell‐derived‐factor (SDF‐1), collagen fragments (C2C), proteoglycan (GAG), lubricin, matrix metalloproteinase‐13 (MMP‐13), and Interleukin‐1 (IL‐1β) were evaluated. Cartilage damage was assessed via histology. The highest concentrations of C2C and SDF‐1 in synovial fluid were found in the posttraumatic OA group, moderate concentrations were found in the primary OA group, and low concentrations in the control group. GAG release in synovial fluid was similar to C2C and SDF‐1. The lubricin concentrations were significantly lower in ACLT joints than either the control or 12‐month primary OA groups, but not between the control and primary OA groups. Higher levels of MMP‐13 and IL‐1β were detected in the joints of the posttraumatic OA group as compared to the control or primary OA groups. Histology revealed greatest OA damage in the posttraumatic OA group, followed by moderate and minimal damage in primary OA and control groups, respectively. This study indicates that the biomarkers and progression of OA may differ in the Hartley guinea pig models with and without posttraumatic OA.