Enhanced Superficial Zone Chondrocyte Expansion and Redifferentiation by Culture on Chondrocyte-Derived Decellularized Matrices

Background: Cell-based therapies to regenerate native-like cartilage are limited by the inability to re-express zone-specific molecules. While monolayer-expanded (passaged) chondrocytes are a clinically approved cell source, the resulting tissues have reduced Proteoglycan-4 (PRG4) expression. This may be due to poor attachment, slow proliferation, and dedifferentiation of superficial zone chondrocytes (SZC) on polystyrene. Optimizing expansion conditions is therefore critical. Chondrocyte-derived decellularized extracellular matrix (CD-ECM) has been shown to enhance proliferation and reduce dedifferentiation of full-thickness chondrocytes, but its effect on SZC remains unknown. We tested the hypothesis that culturing SZC on CD-ECM would improve attachment, proliferation, and reduced dedifferentiation, enabling formation of PRG4-expressing tissue. Methods: Primary bovine SZC were seeded on polystyrene or CD-ECM. Attachment, expansion rate, and gene expression were evaluated during passaging. Cells from each condition were assessed for their capacity to form PRG4-expressing bioengineered tissue. Results: Primary bovine SZC had increased attachment and reached confluency faster on CD-ECM. SZC on CD-ECM were smaller, with fewer actin stress fibers, and exhibited reduced expression of dedifferentiation markers. Furthermore, SZC expanded on CD-ECM were stimulated to form tissues rich in Collagen II and Aggrecan with higher Proteoglycan-4 expression. Conclusions: The use of CD-ECM for passaging SZC may aid in achieving an adequate number of SZC for bioengineering purposes.