Meniscal transection rather than excision increases pain behavior and structural damage in experimental osteoarthritis in mice

SummaryObjectiveTo evaluate pain behavior and structural damage in mice subjected to either meniscal transection or removal.MethodsMice (10/group) were subjected to transection of the medial collateral and anterior cruciate ligaments (ACLT/MCLT) followed by either transection (meniscotomy) or removal (meniscectomy) of the medial meniscus. A control group was subjected only to transection of the ligaments. Pain was assessed using the electronic pressure-meter paw test. Cell influx, measured in joint exudates, and joint histopathology were assessed after 49 days. Four other groups subjected to meniscotomy received indomethacin, the inducible nitric oxide synthase (iNOS) inhibitor 1400W, morphine or the vehicles.ResultsBoth meniscotomy and meniscectomy groups displayed persistent and significant increase in pain behavior as compared to controls, being significantly more severe in the former. Cell influx was more intense in the meniscotomy as compared to the meniscectomy group. Structural damage at the tibia, but not at the femur, was also more severe in the meniscotomy group. Indomethacin and 1400W partially but significantly reduced pain whereas morphine abrogated pain behavior in meniscotomized mice.ConclusionMeniscal transection rather than resection promotes more severe pain and structural damage in mice. Administration of opioids, cyclooxygenase and nitric oxide (NO) synthase inhibitors provide analgesia in this model. Careful description of the structures damaged is crucial when reporting experimental osteoarthritis (OA).