Effects of cyclic-strain on matrix degradation in three-dimensional-cultured periodontal-ligament fibroblasts

Objectives: The periodontal ligament (PDL) fibroblasts play critical roles in the remodelling of peridontal tissue in response to the mechanical force during tooth movement. However, very few studies on matrix degradation in periodontal ligament remodelling has been done. To our knowledge, there is no in vitro study performing cyclic mechanical loading on PDL fibroblasts cultured in three-dimensional lattice. This study is the first one to investigate the effects of cyclic stretch on matrix degradation in PDL fibroblasts cultured in collagen gel. Methods: A defined cyclic stretch system was used. The human PDL fibroblasts seeded in type I collagen gel were stretched cyclically for 24 hours. The MMPs expression in culture medium and cells were detected by gelatine zymorgraphy. The cell proliferation were assed by DNA assay. The changes of ALP activities were tested by ALP assay. The gels were stained with histochemical staining (weight-azan) to observe the cellular morphological changes. Results: After stretched cyclically for 24 hours, the cells in collagen gels were orientated in the direction of stretch force. DNA content and MMP-2 expression increased, while the ALP activity reduced. Conclusions: The cells orientation and the extracellular matrix degradation are regulated by the cyclic stretch force. Cyclic mechanical loading can increase the cell proliferation.