Abstract:

Seeded chondrocytes play a crucial role in current cartilage tissue engineering, yet both the quality and quantity of these cells could be impaired owing to cell dedifferentiation during in vitro proliferation. Here, we used micro-Raman spectroscopy to investigate changes in cellular components upon monolayer culturing of primary rat chondrocytes through multiple passages. Based on the average spectral profiles, we detected a series of Raman peaks and recognized related radicals such as nucleobases, pyranose rings, sulfate, tyrosine, proline, and amides at the single-chondrocyte level. Quantitative analysis of the Raman peak intensities showed that nucleic acids (at 789, 1094, 1576 cm^-1) decreased significantly from passage 1 (P1) to passage 4 (P4), whereas lipids (at 1304 cm^-1) and phosphate (at 957 cm^-1) increased significantly. Moreover, the syntheses of two major hyaline cartilage-associated proteins, aggrecan and type-2 collagen, were impeded, as indicated by the marked decline in the levels of their specific components (glycosaminoglycan at 1042, 1063, 1126, 1160 cm^-1, and hydroxyproline at 1207 cm^-1). Taken together, these features reveal the diminished propagation and secretion abilities of passaged chondrocytes needed for matrix-induced implantation, and shed light on the molecular mechanism of chondrocyte dedifferentiation.

Key words: Chondrocyte, Dedifferentiation, Single-cell analysis, Micro-Raman spectroscopy, Molecular mechanism