Umeå University's logo

Background.The extracellular matrix surrounds all cells within our bodies. The glycosaminoglycan hyaluronan is a major component in the extracellular matrix. Despite its structural simplicity it has been shown to be involved in several important functions. It is a lubricant and shock absorber, as well as an important player in inflammation and tumor invasion. Many of its functions are closely related to its size and concentration in tissues. Therefore methods for measuring these properties are of great importance to properly understand the role that hyaluronan play in different events. Proteins are found both inside and outside cells, and they have a wide variety of functions. The protein structure and function is determined by the properties of their building blocks, the amino acids. Several diseases have been linked to changes in the amino acid sequence of certain proteins by mutations, causing the proteins to form extracellular deposits of structures called amyloid aggregates. The aim of this thesis is to investigate the function of hyaluronan in cell cultures, develop new methods for size determination hyaluronan and to use multivariate methods to provide prediction and better understanding of factors driving protein amyloid aggregation.

Methods.Cardiomyocytes and fibroblast were cultured and stimulated by different growth factors. Hyaluronan was purified and its size and concentration were measured. Crosstalk between cardiomyocytes and fibroblast were investigated and gene expression of hyaluronan synthases was determined. A new method for size measurement of hyaluronan was developed. The amyloid aggregation rate of different mutants of acylphosphatase was predicted by multivariate analysis.

Results. Cardiomyocytes stimulated by PDGF-BB produced hyaluronan. Cardiomyocytes could induce fibroblast to increase its hyaluronan production, through an unknown soluble factor. The cardiomyocyte gene expression changed when stimulated by hyaluronan. GEMMA was presented as a new method for size determination of hyaluronan. Amyloid aggregation of different acylphosphatase mutants could be predicted using a multivariate regression model of the physicochemical and structural properties of the amino acid sequence.

Conclusion. It was shown that cardiomyocytes are not only able to produce hyaluronan, but also induce an increased hyaluronan production in other cells. GEMMA was proven suitable for size determination of hyaluronan at very low concentrations. Multivariate analysis showed that hydrophobic patterns and charge where the most important factors for amyloid aggregation of acylphosphatase.