U Michigan - Sirius Red staining v1

Summary: Picrosirius red staining (also called Sirius red staining) highlights fibrosis by staining collagen (collagen 1 and III fibers) fibers in paraffin-embedded kidney tissue sections. Sirius red stained collagen appears red by light microscopy. When polarized, the birefringence is highly specific for collagen. The larger collagen fibers are bright yellow or orange, and the thinner ones, including reticular fibers, are green.