gms | German Medical Science

Objectives: Osteoarthritis is a degenerative disease mainly caused by aging, although in younger patients (aged 25 - 50) it can be a consequence of sports-related injuries or trauma. This results in early osteoarthritis with subsequent changes in cartilage extracellular matrix. Cell-based tissue engineering approaches using mesenchymal stem cells (MSCs) are an ideal cell type for the treatment of early osteoarthritc defects. Our group has demonstrated in a clinical study, that interleukin-1beta (IL-1 β ) was expressed in cartilage plugs from patients with early osteoarthritis. In vitro studies have shown that IL-1 β inhibits cartilage formation in chondrocytes or MSCs undergoing chondrogenesis. However, these studies show complete inhibition of tissue formation, whereas in the context of early osteoarthritis, cartilage extracellular matrix remains around the defect site. Thus, the present study sought to develop a model mimicking early osteoarthritis using MSCs.

Methods: Human MSCs (Male donors; aged 18-60 years, n = 6) were isolated from bone marrow and expanded in culture for one passage. 2 x 10⁵ MSCs were aliquoted into wells of a 96-well cell culture plate in the presence of 10ng/ml TGF- β ₁ or in combination with IL-1 β administered at a range of concentrations (0.1, 0.5, 1 and 10ng/ml) and centrifuged to form pellets. Pellets were removed from culture on days 7, 14 and 21. Pellets were evaluated for wet weight, pellet area, histological (DMMB staining, collagen type I, II, MMP-13 and TGF- β receptor II) and collagen type II ELISA analysis.

Results and Conclusion: Chondrogenic pellets in the presence of IL-1 β demonstrated a dose-dependant inhibition in chondrogenesis. Concentrations equal or greater than 0.5ng/ml IL-1 β showed significant reduction (p < 0.05) in pellet area and wet weight, with no positive staining for collagen type I, II (including ELISA analysis) and DMMB. However, at 0.1ng/ml IL-1 β , despite a slight reduction in pellet area, positive staining for collagen type I, II and DMMB was observed. Furthermore, MMP-13 matrix staining was increased and TGF- β receptor II staining was decreased in pellets at IL-1 β concentrations above 0.5ng/ml.

Thus, a dose dependant catabolic response in cartilage extracellular matrix formation was demonstrated for IL-1 β treated MSCs undergoing chondrogenesis. At concentrations equal or greater than 0.5ng/ml IL-1 β , MMP13 expression was observed in the matrix, indicative of osteoarthritis. Furthermore, there was reduced expression of TGF- β receptor II under these conditions that is required for TGF- β induced chondrogenesis. However, at 0.1ng/ml IL-1 β , a reduced catabolic response in extracellular matrix components was observed, whilst showing a moderate expression in MMP-13 and the presence of cellular TGF- β receptor II expression. Therefore, this latter model may be used to develop pro-chondrogenic strategies for the treatment of early osteoarthritic defects.