The small proteoglycan biglycan is associated with thick collagen fibrils in the mouse decidua.

In mice, embryo implantation induces profound changes in the endometrium. These changes include redifferentiation of endometrial fibroblasts and extensive remodeling of extracellular matrix components. We have previously shown that, during this process, there is an impressive increase in the thickness of collagen fibrils present in decidualised areas that surround the implantation site, while collagen fibrils in non-decidualised areas and in the interimplantation site remain thin. In vitro and in vivo experiments have identified small leucine rich proteoglycans (SLRPs) as regulators of collagen fibrillogenesis. In a previous study, we demonstrated a difference between the pre-implantation and the post-implantation expression and distribution of four SLRPs types in uterine tissues. The present study, utilising immunocytochemical electron microscopy, shows that biglycan is associated with the presence of thick collagen fibrils in decidualised regions of the endometrium and that decorin is associated exclusively with thin collagen fibrils in non-decidualised endometrial areas. These results strongly indicate that biglycan plays a role in collagen fibrillogenesis and probably participates in the determination of collagen fibril thickness in the mouse decidua.