Biochemical changes of the pericellular matrix and spatial chondrocyte organization—Two highly interconnected hallmarks of osteoarthritis

Abstract

During osteoarthritis, chondrocytes change their spatial arrangement from single to double strings, then to small and big clusters. This change in pattern has recently been established as an image‐based biomarker for osteoarthritis. The pericellular matrix (PCM) appears to degrade together alongside cellular reorganization. The aim of this study was to characterize this PCM‐degradation based on different cellular patterns. We additionally wanted to identify the earliest time point of PCM‐breakdown in this physiopathological model. To this end, cartilage samples were selected according to their predominant cellular pattern. Qualitative analysis of PCM degradation was performed immunohistochemically by analysing five main PCM components: collagen type VI, perlecan, collagen type III, biglycan, and fibrillin‐1 (n = 6 patients). Their protein content was quantified by enzyme‐linked immunosorbent assay (127 patients). Accompanying spatial cellular rearrangement, the PCM is progressively destroyed, with a pericellular signal loss in fluorescence microscopy for collagen type VI, perlecan, and biglycan. This loss in protein signal is accompanied by a reduction in total protein content from single strings to big clusters (P < .001 for collagen type VI, P = .003 for perlecan, and P < .001 for biglycan). As a result of an increase in the number of cells from single strings to big clusters, the amount of protein available per cell also decreases for collagen type III and fibrillin‐1, where total protein levels remain constant. Biochemical changes of the PCM and cellular rearrangement are thus highly interconnected hallmarks of osteoarthritis. Interestingly, the earliest point in time for a relevant PCM impairment appears to be at the transition to small clusters.

Biomaterial Integration in the Joint: Pathological Considerations, Immunomodulation, and the Extracellular Matrix

“…During the onset of OA, the spatial organization of the chondrocyte changes, followed by rearrangement of the pericellular matrix. [27] The pericellular matrix is especially dynamic as it is highly accessible to the chondrocyte and readily modified. The [16] Copyright 2020, John Wiley and Sons.…”

“…During the onset of OA, the spatial organization of the chondrocyte changes, followed by rearrangement of the pericellular matrix. [ 27 ] The pericellular matrix is especially dynamic as it is highly accessible to the chondrocyte and readily modified. The matrix molecules are either bound directly to the plasma membrane or to transmembrane receptors that can activate intracellular signaling and subsequent gene activation.…”