Article
Capacity of TGF-β1-stimulated local chondrocytes to regenerate a cartilage defect filled with nanocellulose matrix
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Published: | October 16, 2008 |
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Introduction: Local cartilage defects do not show spontaneous regeneration or filling of the defect without additional measures. There are well-established treatment methods like cartilage drilling/microfracturing or autologous chondrocyte transplantation (ACT). Due to the problems of the conventional treatment strategies (cell expansion, additional damage of non-affected regions, and quality of the regenerative tissue), an alternative approach was developed using the capacity of resident cartilage chondrocytes in combination with chondroinductive TGF-β1 and a bacterially synthesized nanocellulose (BC) as a biocompatible and non-resorbable matrix.
Objective: In the present study, the capacity of TGF-β1-stimulated local chondrocytes to regenerate a cartilage defect filled with the nanocellulose matrix was assessed.
Methods: In a newly developed in vitro model a localized cartilage defect (2 mm diameter) was created in bovine cartilage discs (7 mm diameter ) using a biopsy punch. Subsequently, the defect was filled with the never dried matrix consisting of non-resorbable nanocellulose, which acts as a scaffold for the ingrowth of cells. The construct was cultured in vitro for 2 and 4 weeks respectively, with the addition of TGF-β1 (0, 10, 50, 100 ng/ml). Subsequently, frozen sections (8 µm) were histologically processed. For general morphology, the samples were subjected to staining with Hematoxylin/Eosin (HE). Detection of proteoglycans was performed using Safranin O/Fast green (SO) staining and the aggrecan content was analysed by immunohistological staining with specific antibodies for intact aggrecan.
Results: After 2 and 4 weeks, the cartilage matrix surrounding the defect remained fully intact with strong SO positivity and vital chondrocytes. However empty chondrocyte lacunas were observed at the edges of the cartilage explant. There was good bonding between the contact zone of the cartilage defect and the BC matrix due to its strong swelling capacity. Vital chondrocytes migrated from the cartilage matrix onto the edges of the BC-matrix and showed signs of adherence. The main finding was that after 4 weeks of culture TGF-β1-stimulated samples (all concentrations) showed positive staining with SO within the BC-matrix, indicating proteoglycan deposition. This was confirmed by immunohistological staining, showing a comparably strong positive reaction for aggrecan in the NC-matrix and the surrounding cartilage.
Conclusion: In the present cartilage regeneration model, an elevated proteoglycan (aggrecan)-content within the BC insert was observed after 4 weeks of stimulation with the chondrogenic factor TGF-β1. This suggests that endogenous chondrocytes may have the capacity to regenerate an initially cell-free defect filled with BC.