A Study of the Roles of Perlecan in Tissue Development and Turnover: A Focus on the Liver

Liver diseases are catastrophic illnesses that cause thousands of deaths per year. The liver has natural unequalled regenerative capacity that involves matrix remodelling. Understanding the role of perlecan in liver is essential for advances in liver treatment and regeneration.Perlecan and HS were immunolocalised in hepatocyte bundles, hepatoblasts and surrounding the hepatic arteries and bile ducts of the foetal liver. Perlecan was detected in purified protein extracts from human foetal liver and was found to be decorated with HS side chains.Perlecan was detected pericellularly in HepG2 cells (hepatocytes) and intracellularly and extracellularly in LX-2 cells (stellate cells). Perlecan and laminin were found to co-localise in HepG2 cells under normal growth conditions. Under crowded conditions, laminin and perlecan were found to co-localise in both HepG2 and LX-2 cells. Additionally, co-localisation was observed between HS and laminin, and HS and perlecan, under crowded conditions in LX-2 cells. Perlecan was detected in purified PG enriched fractions from both HepG2 and LX-2 cells; however no HS side chains were detected on perlecan. In purified PG enriched fractions from co-cultured HepG2 and LX-2 cells, both HS and CS were found to decorate perlecan.Perlecan HS deficient mice (HSPG2Δ3/Δ3) were compared to wildtype (C57BL/6) mice to determine the effect a lack of HS on perlecan would have on matrix stability. ECM components were examined in both mice from birth to 20 weeks of age. HSPG2Δ3/Δ3 mice livers were found to contain 6 times more fissure structures than C57BL/6 mice as animals aged. Perlecan was detected in sinusoidal regions between hepatocytes, intracellularly in HSPG2Δ3/Δ3 mice and extracellularly in C57BL/6 mice. Perlecan in C57BL/6 livers was found to be decorated with HS while perlecan in HSPG2Δ3/Δ3 mice livers was not decorated with HS or CS.Understanding liver perlecan interactions provides an insight into the role of perlecan during liver regeneration. Mice lacking exon 3 of perlecan were found to show impaired matrix formation in later ages which could indicate an impaired regenerative response. Integration of this knowledge in tissue engineering strategies can improve therapeutic solutions for fibrotic livers or assist in the creation of bio-artificial livers