Expression of alpha and beta subunits of the integrin superfamily in articular cartilage from macroscopically normal and osteoarthritic human femoral heads

Abstract

OBJECTIVE The objective of this study was to detail the topographical and zonal distribution of α and β subunits of the integrin superfamily in normal and osteoarthritic cartilage. METHODS Immunohistochemistry utilising antibodies towards α and β subunits was performed on cryostat sections of human articular cartilage from macroscopically normal (n = 6) and osteoarthritic (n = 6) femoral heads. Samples of articular cartilage were obtained from 12 topographically distinct sites from each femoral head. Each section was divided into zones (superficial, middle, deep) and staining scores were recorded. RESULTS Normal cartilage stained for integrin subunits α1, α5, αV, β1, β4, and β5, but not for α2, α3, α4, α6, β2, β3, and β6. Intact and non-intact residual cartilage from osteoarthritic femoral heads stained for α1, α2, α5, αV, β1, β4, and β5. Staining was occasionally seen for α4 and β2, but not for α3, α6, β3, and β6. There was no topographical variation in the staining for any of the subunits in either normal or osteoarthritic cartilage. The only subunit that displayed a zonal variation was αV; staining for this subunit was most pronounced in the superficial zone compared with the middle and deep zones. CONCLUSION Chondrocytes in normal and osteoarthritic cartilage express the integrin subunits α1, α5, αV, β1, β4, and β5. Chondrocytes in osteoarthritic cartilage, in addition, express the α2, α4, and β2 subunits. The αv subunit is expressed by more chondrocytes in the superficial zone in comparison with cells in the deeper zones. None of the subunits display topographical variation in expression.