Effects of biglycan deficiency on myocardial infarct structure and mechanics

Biglycan, a small leucine-rich proteoglycan, has been shown to interact with extracellular matrix (ECM) collagen and may influence fibrillogenesis. We hypothesized that biglycan contributes to post-myocardial infarction (MI) scar development and that the absence of biglycan would result in altered scar structure and mechanics. Anterior MI was induced in biglycan hemizygous null and wild-type mice by permanent ligation of the left coronary artery. The initial extent of ischemic injury was similar in the two groups, as was the infarct size after 30 days, although there was some tendency toward reduced expansion in the biglycan-null. Electron microscopy revealed that collagen fibrils had a smaller average diameter and a narrower range in the biglycan-null scar, as well as appearing more densely packed. In vivo strain analysis showed that biglycan-null scars were stiffer than the wild-type. Remote LV collagen concentration tended to be reduced in biglycan-null hearts, but the difference was not statistically significant. Null-expression of biglycan may alter collagen fibril ultrastructure, and thereby influence scar mechanics and remodeling.