Expression of extracellular matrix molecules in human mesangial cells in response to prolonged hyperglycaemia

Abstract

Post-mitotic cultures of human mesangial cells were maintained in media containing 4–30 mM D-glucose for up to 28 days. Changes in mRNA and protein levels for specific macromolecules occurred between 7 and 14 days after initiating hyperglycaemic conditions. Slot blot analysis showed 2–3-fold increases in mRNAs for collagen type I, fibronectin, versican and perlecan, whereas mRNA for decorin was increased by up to 20-fold. Levels of mRNAs for biglycan and syndecan were unaffected by hyperglycaemic culture. Reverse transcriptase PCR (RT–PCR) confirmed that decorin mRNA levels are greatly elevated and also showed increased transcription of the TGF-β1 gene in hyperglycaemic cultures. Western analysis and ELISA indicated accumulations of collagen types I and III, laminin and fibronectin in the cell layers and media of hyperglycaemic cultures with increasing time. Type IV collagen did not accumulate in either compartment of hyperglycaemic mesangial cell cultures. Collagen types I, III, and fibronectin did not accumulate in the cell layers of hyperglycaemic human dermal fibroblasts, indicating a cell-specific response in mesangial cultures. Decorin and versican, but not biglycan, were increased in the hyperglycaemic mesangial cell culture media. There were no apparent changes in core proteins for decorin and biglycan in fibroblast media. Transforming growth factor β1 (TGF-β1) in hyperglycaemic mesangial cell cultures increased 5-fold after 7 days, but decreased thereafter to only approx. 2-fold after 28 days. The changes in TGF-β1 mRNA, as detected by RT–PCR, and protein followed one another closely.