Extracellular Matrix Synthesis in the Mammalian Liver

The role of the extracellular matrix in the liver is complex, and this thesis will study both the structure and role of normal hepatic extracellular matrix, and how these are affected in liver disease. In order to do this, it was necessary to develop new techniques as well as using methods already available. In Chapter 1, the basic structure of the liver is described. It also identifies the different types of liver cells which are present, and their known functions. Liver injury is examined in Chapter 2 and this covers both the possible responses of the hepatic cells to injury, and the patterns of injury found in different disease entities. Chapter 3 identifies the different component groups of the extracellular matrix, and their general structure and function. The largest of these groups is the collagen family, and this is studied in greater detail in Chapter 4. The remaining components of the extracellular matrix are individually described in Chapter 5. The previous three chapters looked at the components found in all extracellular matrices, and in Chapter 6 the hepatic extracellular matrix is described in greater detail. This chapter covers both the composition of the extracellular matrix and the cells which are believed to be responsible for their synthesis. It summarises the knowledge of the hepatic extracellular matrix that was available at the beginning of the study. In Chapter 7, the different techniques available for the ultrastructural examination of liver tissue are described and compared. This chapter also includes the development of novel techniques for the ultrastructural study of the hepatic extracellular matrix. The materials and methods are detailed in Chapter 8, including the types of liver tissue used. The techniques described in Chapters 7 and 8 were used to map the distribution of the extracellular matrix in normal human liver in Chapter 9. It was necessary to identify the normal distribution of the extracellular matrix in a number of biopsies in order to identify any changes in the distribution which may occur during disease processes. A range of components were examined, including collagen types I, III, IV, V, and VI, laminin, vitronectin and fibronectin. At this stage, it was decided which antibodies used in the study of normal liver were suitable for continuing studies in diseased liver. It was decided to examine the effects of liver disease on the distribution of collagen types I, III, IV, and VI, as well as on fibronectin. These are illustrated in Chapter 10. In the last chapter, a number of points arising from this study are discussed. These include the validity of the techniques used, technical problems with the immunolabelling techniques used, the altered distribution of the extracellular matrix in diseased liver, the novel description of type VI collagen distribution and the possible cellular origin of the extracellular matrix proteins. Finally, the overall, and extremely complex role of the extracellular matrix is examined, both in normal and diseased liver. The most important aspects of this work fall into two categories. The first is the development of the ultracryomicrotomy techniques which were necessary in order to carry out the immunocytochemical studies. Once this part of the work had been completed, it was possible to study new aspects of the hepatic extracellular matrix in great detail, including the distribution of type VI collagen, and the development of basement membranes in the space of Disse