NITEGE-Expression in Meniscal Matrix. A New, Immunohistochemical Marker of Meniscal-Tissue Degeneration

Background: No marker reflecting the pathobiology of meniscal degeneration (MD) is established so far. NITEGE is a hexapeptide fragments produced when aggrecan is cleaved. Methods: In vitro IL-1 exposition of bovine menisci (n = 4) caused extracellular NITEGE deposits detected by immunofluorescence. A retrospective immunohistochemical analysis of (n = 60) patients after meniscectomy for NITEGE deposits was performed. MD was graded as follows: no/little (grade 0/1), medium (grade 2) or severe (grade 3). Results: NITEGE deposits in areas of degeneration were demonstrated in 55% of the patients with grade 2 or 3 MD (PPV & specificity 100%), while no extracellular NITEGE deposits in the menisci with grade 0 or 1 MD could be detected. Age correlated with NITEGE deposits (r = 0.46) and grade of MD (r = 0.48). NITEGEpositive cell density and size were significantly higher close to a tear (p < 0, 001). Interpretation: Extracellular NITEGE deposits may be regarded as markers of medium and severe MD and might be used in diagnostic histopathology.