Human chondrocytes differentially express matrix modulators during in-vitro expansion

Abstract

Problem: Cartilage tissue engineering has an important role to play in the generation of graft material for reconstructive surgery. In cultured chondrocytes, the dedifferentiation of cells seems unavoidable for multiplication. Dedifferentiated cells produce a matrix of lower quality. However, the molecular basis is still not well understood. Therefore, the aim of our study was to investigate the expression of matrix modulators in human chondrocytes during expansion. Methods: Human chondrocytes were isolated from septal cartilage (n = 32) and held in primary cell culture. Cells were harvested after 1, 6, and 21 days. The differentiation of the cells was investigated with light microscopy, the expression patterns of various proteins (MMPs, BMPs, TIMPs) using immunohistochemistry, and the expression of distinct genes with the microarray technique. Results: The chondrocytes showed strong in vitro proliferation. After 6 and 21 days, BMP-5 and BMP-8 were upregulated, BMP-2 was downregulated, and BMP-6 was inactivated. Other BMPs were not expressed. The expression of MMP-2, -3 and -13 was upregulated from day 1 to day 21, MMP-12 and MMP-20 were down-regulated. Other MMPs were never expressed. TIMP-1 was upregulated, and TIMP-3 downregulated during expansion. Conclusion: Differential expression of matrix modulators might influence the matrix composition of engineered cartilage grafts. Significance: Improving basic knowledge in this area ultimately may help clinicians identify and proactively intervene in an effort to prevent bioartificial cartilage from losing stability. Support: None reported.