Characterisation of decellularised oesophagus in tissue engineering.
Chia, Evelyn Sheng Nan.
Date of Issue2009
School of Mechanical and Aerospace Engineering
Cancer of the oesophagus is a deadly disease that is common among people all round the world, but few usually survive this disease as it is usually discovered at a late stage. Decellularisation, a special technique of removing cells from diseased tissues and organs to create “natural” scaffolds used in tissue engineering could be used to create bio prostheses to treat currently incurable diseases including oesophageal cancer. Although it is relatively new concept, its rapid advancement and the many successful reports of creating “revived” tissues and organs from decellularised extracellular matrix shows great promise. Decellularised tissues and organs are created by means of decellularisation protocols, which are made up of unique combinations of physical and chemical treatments. Many of these protocols have been developed by experts and researchers in the tissue engineering field. However, decellularisation was found to be a very specific process; protocols that work well for a specific tissue do not work as well for another tissue or organ. The success of the decellularisation process is determined by two factors; the cell removal efficiency and the preservation of the extracellular matrix in the decellularised scaffold. The cells must be totally removed so that there will be minimal complications resulting from the immune system recognition of allogeneic or xenogenic cells. The extracellular matrix must also be preserved, as its structure will directly affect the behaviour of cells. The goal of this project is to evaluate methods of decellularisation on the mechanical properties of oesophageal tissues, with the goal of developing an effective decellularisation protocol to prepare scaffolds from oesophageal tissues. The mechanical properties were characterized by the tensile test and cyclic loading test. The results of the two protocols were then compared against the fresh (undecellularised) samples and analysed by ANOVA at a confidence level of 95%. Results from the tensile tests showed the decellularised samples were significantly different in the mechanical properties (maximum force and extension) of the fresh samples. However, as the thickness of the sample, which affects the ultimate tensile strength, was not considered in the project, it could be possible that if the samples were compared based on ultimate tensile strength, the difference would not be significant. Nevertheless, the difference in loading and extension ability of the fresh and decellularised samples could most probably be a result of different hydration level. The possibility of the extracellular matrix being damaged and changed after decellularisation should also not be dismissed as the chemicals used are known to have damaging effects on the structure of the matrix. Results from the cyclic loading test mostly showed that the decellularised samples did not vary from the fresh samples insignificantly, which indicated that the composition of the extracellular matrix of the decellularised samples were likely to be preserved. The slight variation between the samples was the also found to be most likely caused by the difference in hydration level. Contrary to the tensile test results, the decellularised samples were found to be less hydrated then the fresh samples. A possible explanation would be that although the decellularised samples were initially more hydrated, after repeated loadings, they were unable to retain this hydration as well as the fresh tissues. This could have been caused by a loss of glycosaminoglycan (GAGs), a water binding component in the extracellular matrix that was destroyed by the chemicals used in the process of decellularisation.
Final Year Project (FYP)
Nanyang Technological University