| At present, there are many physical factors such as electromagnetic fields, ultrasound, centrifugal force and microgravity uesed in tissues or cells culturing in vitro, in which a direct mechanical stimulus is more appropriate to build functional cartilage. Currently, the engineered cartilages which are built by a variety of mechanical stimulation bioreactor can not meet the clinical needs in their function and other aspects of physical and chemical. According to the actual movement of the articular cartilage, we developed a low-pollution bioreactor with rolling-compression load. The bioreactor can achieve rolling-compression loading with adjustable compression and control the load’s speed and frequency, and moreover culturing sample being in a plastic bag under loading will greatly reduce the pollution probability.Using finite method a multi-layer composite cartilage model was established by referencing the physiological structure of human knee cartilage and the movments during human normal walking. The models having bag (with membrane) or not having bag(without membrane) under rolling-compression load were simulated. The displacements and stress distributions of cartilage were analyzed from the three aspects:with membrane or without membrane, cartilage compression, rolling speed under a rolling and compressing load. The simulations are shown:First, there should be an appropriate value for the elastic modulus of the membrane of bags in cartilage tissue engineering; Second, when the rolling load speed is high enough, the impact of the membrane on cartilage can be ignored, as the Mises stress and displacement values in the two models are basically the same size. By simulation, we can estimate the displacement amount of compression of cartilage in the model with membrane, which achieves a relatively accurate control of the amount of compression load applied to the cartilage during the biological experiments. Third, in the same rolling speed under different compression loads, layers of cartilage in the two models suffered very little difference Mises stress with or without membrane. Fourth, when loads go through the fixed inspection points belong to diffrent layers of the membrane cartilage model, these points suffered alternating positive and negative values of Mises stress, principal stress and shear stress. Through the finite element simulation of articular cartilage culturing experiments in vitro, results provide a theoretical basis for the choice of material parameters.The knee cartilage of a minor rabbits was obtained as a research sample, using bioreactor rolling-compression load with bagged samples, we preliminary study the mechanical impacts of the rolling-compression load on cartilage in vitro. Experiment showed dynamic rolling compressing sample’s growth is better than the static culture group. The result suggested that the rolling compressing load could promote the growth of cartilage in vitro.We developed a rolling-compression bioreactor with membrane bags, and obtained experimental conditions and the mechanical state of culture by finite element simulation, and preliminarily studied the impacts of rolling compression load on the cartilage in vitro through biological experiments, and explore the mechanical environment of cartilage tissue engmeering. |
