Supplementary MaterialsSupplementary Information srep27398-s1. collagen content and decrease in elastic fibers resulted in rearrangement and increased stiffness of damaged liver ECM. Interestingly, the alterations in ECM components were nonhomogenous and differed between periportal and pericentral areas and thus our experiments exhibited the differential ability of selected ECM components to regulate the proliferation of hepatocytes and biliary cells. We define for the first time the alterations in the ECM composition of livers recovering from damage and present functional evidence for a coordinated ECM remodelling that ensures an efficient restoration of liver tissue. Liver is an organ with a remarkable regenerative capacity. Liver regeneration in response to an injury involves restoration of functional liver tissue through proliferation of both mature as well as stem/progenitor cells and remodelling of the extracellular matrix (ECM)1. Furthermore, such life-threatening pathological conditions as liver cirrhosis and liver cancer are accompanied by aberrant changes in ECM structure and composition2. The ECM has been traditionally considered an inert cell growth substrate; however, during the last decade the knowledge about the biological role of the ECM has greatly developed. At present day, the ECM is recognized as a dynamic structure, which is composed of a variety of proteins and other macromolecules and provides a supportive scaffold that actively regulates the biological functions of the cells, at least partly by conversation with specific cell surface molecules3. For example, integrins play a major part in transmitting the information from ECM to MK-8776 inhibitor cells and by synergizing with other cell surface molecules like growth factor receptors regulate migration, proliferation, angiogenesis, inflammation or apoptosis4,5. Therefore, changes in the ECM composition alter cell signalling in liver and facilitate either MK-8776 inhibitor normal regeneration or pave the way for liver diseases1. It should be noted that as liver ECM is produced by the cellular components of liver, the ECM remodelling taking place during regeneration and pathological processes results from changes in protein synthesis pattern and pericellular proteolytic activity of liver parenchymal and stromal cells but also invading inflammatory cells6. Collagens and fibronectin are the main structural constituents of ECM. Type I and III collagens (col1 and col3) are highly expressed in liver capsule, portal stroma, Disses space and fibroid tissue7,8. Type IV collagen (col4) and laminins make up the basal lamina MK-8776 inhibitor of the blood vessels and bile ducts8. Type V collagen (col5) forms thin fibers located in the centre of thick col1 and col3 fibrils. It is notable that more than five-fold increase in collagen deposition has been found in fibrotic livers compared to a healthy organ9. Fibronectin is usually Rabbit Polyclonal to Clock a glycoprotein that can be found in the liver capsule, portal stroma and Disses space. In normal adult tissues its levels are modest but increase rapidly during tissue regeneration10. Recent studies showed that the absence of fibronectin in liver leads to more extensive liver cirrhosis induced by liver damage and was accompanied by increased liver stiffness and disorganized collagen network11. The aim of the current work was to identify the changes in the liver ECM composition during liver regeneration and to study the potential mechanisms by which these regulate the proliferative properties of liver cells. To achieve this we utilized two well-established mouse models of toxic liver injury coupled with tissue decellularization and mass spectrometry. We identified prominent changes in the content of main structural components of the liver ECM as well as identified multiple alterations in the amounts of minor ECM constituents known to regulate tissue regeneration and development. Similar alterations in ECM were found to be present in injured human livers. Scanning electron microscopy (SEM) analysis revealed the loss of elastic fibers and microfibrils in damaged livers and the resulting increase in liver ECM stiffness was identified with atomic pressure microscopy (AFM). Interestingly, we found that the expression of a number of ECM proteins differed in pericentral and periportal areas. Since the analysis of the growth promoting properties of these proteins showed selective enhancement of the proliferative potential of either hepatocytes and or non-hepatocyte cells encompassing the biliary cell compartment we layed out a model where the identified changes in ECM composition ensure coordinated.