Objective. To perform a comprehensive analysis of the integrin forms expressed by normal human articular chondrocytes.

Methods. Cartilage sections and collagenase-released chondrocytes were probed with a comprehensive panel of integrin isoform–specific monoclonal antibodies (MAb), using in situ immunohistochemistry techniques, indirect immunofluorescence and flow cytometry, and immunoprecipitation/sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE).

Results. Chondrocytes in cartilage sections reacted with MAb specific for the α5, αv, and β1 integrin subunits and the αvβ3 and αvβ5 heterodimers. They also reacted with a polyclonal antibody specific for the intracytoplasmic portion of the α1 subunit. MAb specific for the αv subunit reacted more strongly with chondrocytes near the articular surface than with those in deeper layers of cartilage, and the αvβ3-specific MAb reacted exclusively with chondrocytes within the most superficial 30 μm of cartilage. Flow cytometric analysis and SDS-PAGE analysis of immunoprecipitates prepared from extracts of cell-surface radioiodinated chondrocytes confirmed the above observations, and additionally revealed the presence of the α3β1 integrin.

Conclusion. Normal human articular chondrocytes prominently display substantial quantities of the α1β1, α5β1, and αvβ5 integrin heterodimers, as well as lesser quantities of the α3β1 and αvβ3 heterodimers, The αv subunit–containing integrins are detected more readily on the more superficial chondrocytes than on chondrocytes deep within cartilage. These observations provide the basis for analysis of the role of chondrocyte integrins in cartilage homeostasis and in the pathogenesis of joint diseases.