Presence of pannus-like tissue on osteoarthritic cartilage and its histological character

Abstract

Objective To investigate and characterize pannus-like tissue which is often present on osteoarthritic articular cartilage. Design Cartilage specimens from 15 knee and five hip joints of patients with osteoarthritis (OA) undergoing arthroplasty were stained for HE and Safranin-O. They were also immunostained by antitype I collagen, type II collagen, CD68, IL-1β and MMP3 antibodies. Results Ninety percent of joints have pannus-like tissue on the articular surface, preferentially in a marginal area. The articular cartilage was divided into three regions according to the location: the marginal zone, the intermediate zone and the paraeburnated zone. Pannuslike tissue in OA knee joint occurred 45.9%, 27.5% and 11.1% of the surface of each region respectively. Histologically, pannus-like tissue could be classified into the vascular type and the fibrous type. Extracellular matrix of both types of tissues were negative for Safranin-O and type II collagen, but positive for type I collagen. IL-1β and MMP3 expressing cells are predominant in pannus-like tissue, whereas CD68 positive cells were infiltrated in only a few samples. Vascular type tissue kept continuity with bone marrow suggesting mesenchymal origin. ConclusionPannus-like tissue exists in advanced OA cartilage, preferentially in the marginal zone. It expressed IL-1β and MMP3, which strongly suggests that it contributes to cartilage degradation. Copyright 2003 Published by Elsevier Science Ltd on behalf of OsteoArthritis Research Society International.