Stimulatory effects of non-enzymatic glycation on fibronectin matrix assembly

Abstract

Advanced glycation endproducts (AGEs) are a heterogeneous group of compounds that form via the non-enzymatic glycation of proteins and other molecules throughout our lifespan and at a higher rate in diabetic patients. AGEs contribute to the progression of many fibrotic diseases by altering extracellular matrix (ECM) functions and cell signaling activities. However, the question of whether the AGE-modification of ECM proteins leads to excess ECM assembly and fibrosis remains unanswered. In this study, complications due to AGE accretion by kidney mesangial cells were investigated. In order to provide a native-like AGE-rich microenvironment to analyze matrix assembly, decellularized ECM was incubated in a sugar solution. In addition, hybrid natural ECM-synthetic polymer scaffolds were developed for a more stable, dense matrix. Mass spectrometry was used to identify twenty-eight AGE modification sites along fibronectin (FN), a major component of fibrotic lesions. AGE-modified sites resided on functionally relevant sites on FN. One such FN domain with AGE modifications was relevant for binding integrins, which influence FN matrix assembly. Mesangial cells were stimulated to assemble increased amounts of FN matrix when exposed to an AGE-modified ECM. AGE-modified bovine serum albumin also increased FN matrix assembly, suggesting that the stimulation of matrix assembly can occur from AGEs alone and not AGE-ECM specifically. Receptor for AGE (RAGE) function-blocking antibody decreased FN matrix assembly, suggesting that RAGE is responsible to some extent for AGE-induced matrix assembly. These results show a role for AGE-modified FN matrix in the accumulation of ECM that occurs during the progression of fibrosis.