ATTACHMENT OF MENISCAL FIBROCHONDROCYTES TO A COLLAGEN TYPE I SCAFFOLD INDUCES MMP AND IL-6 EXPRESSION

Abstract

Introduction: After a meniscus trauma, preservation of the meniscus is the most important surgical goal. The use of scaffolds colonized with meniscus cells (fibrochondrocytes) to reconstruct meniscal defects seem to be a promising way for the treatment of a meniscus trauma. The goal of our investigations was the analysis of expression of different anabolic and catabolic factors in human fibrochondrocytes after seeding these cells onto a collagen I scaffold to investigate the regenerative potential of such a construct for the treatment of meniscus tears.

Material and Methods: Human meniscus tissue was digested in collagenase and dispase and cells were characterized by immunohistochemistry. To test scaffolds, we used a commercially available bovine collagen I matrix approved for surgical purposes. The scaffold was colonized with human fibrochondrocytes in a density of 106 cells per cm2. Cells expanded at the same ínoculation density w/o scaffold served as mock-controls. After 14 and 28 days in culture, the cells were extracted from the scaffold by aid of collagenase (Sigma, Deisenhofen, FGR) and analyzed for the expression of different factors, including IL-1β, IL-6, TGF-β, TIMP-1, TIMP-3, MMP-1, and MMP-3 using a quantitative RT-PCR-technology.

Results: Bovine collagen I matrices could be colonized with human fibrochondrocytes. After 14 and 28 days of incubation on the scaffolds, the cells show the same mRNA expression levels of IL-1β, TIMP-1, TIMP-3, and TGF-β when compared to controls. In contrast, after 14 days IL-6 (12.7-fold ± 4.4, p< 0.001), MMP-1 (11.3-fold ± 2.4, p< 0.001), and MMP-3 (13.7-fold ± 6.8, p< 0.031) were upregulated on transcription levels in the scaffold when compared to controls after the same period of culture. After 28 days of culture in scaffold the expression of MMP-3 was upregulated 78.2-fold (± 7.4, p< 0.0001), MMP-1 (71.3-fold ± 5.9, p< 0.0001) and IL-6 was elevated 98.9-fold (± 9.1, p< 0.0001) compared to controls.

Discussion/Conclusion: We were able to cultivate and characterize human fibrochondrocytes from menisci of the knee joint colonized onto a bovine collagen I matrix. We could show that meniscus cells revealed a significantly increased expression of MMP-1 and MMP-3, and also a significant elevation of IL-6 mRNA after 14 and 28 days of culture. No changes were found in the expression levels of IL-1β, TGF-β, and the TIMPs. This suggests that the meniscus cells colonized onto a bovine collagen I scaffold produce a considerable amount of catabolic or inflammatory factors. This may lead to a destruction of the scaffold-matrix itself and the extracellular matrix of the meniscus. Secondly, IL-6 could induce a global inflammation around the scaffold by activating the IL-6 inflammation cascade.