Rapid phenotypic changes in passaged articular chondrocyte subpopulations

TLDR

Articular chondrocytes are frequently expanded in vitro for cartilage repair, and effective tissue engineering depends on maintaining their chondrocytic phenotype. The study aimed to quantify dedifferentiation of zonal articular chondrocytes during monolayer passage using real‑time PCR. Gene expression of collagen I/II, aggrecan, and superficial zone protein was measured across passages P0–P4 to assess changes in extracellular matrix protein expression. Significant dedifferentiation occurs already at first passage and persists in 3D alginate beads, indicating major challenges for cartilage regeneration.

Abstract

Articular chondrocytes are often expanded in vitro and then used to assist in healing articular cartilage defects. We investigated the extent of dedifferentiation in monolayer-passaged, zonal articular chondrocytes by using quantitative, real-time PCR. The relative gene expressions for collagen type I and II, aggrecan, and superficial zone protein were analyzed for relevant passage numbers (P0-P4) to determine how the expansion of chondrocytes affects the expression of cartilage extracellular matrix proteins. Results reveal that dramatic changes occur as early as first passage. Furthermore, these changes are shown to persist even when the expanded cells are encapsulated in 3D, alginate beads. Successful tissue engineering and autologous cell transplantation procedures rely heavily on having a cell source that expresses the chondrocytic phenotype. The results of this study suggest that major problems exist at the front-end of cartilage regeneration efforts.