Med Electron Microsc (2002) 35:68–80 © The Clinical Electron Microscopy Society of Japan 2002 SPECIAL REVIEW SERIES: Advance in renal disease research

out to clarify the molecular mechanisms of fibrosis, and one molecule that has received most attention is collagen. This molecule belongs to an ECM protein family, present in almost all normal tissues in humans and multicellular ani-mals. Collagens form the architectural framework of the vertebrate body and are an essential component for mainte-nance of the structural integrity of cells and tissues. Wound healing Wound healing is a complex process that comprises an or-dered sequence of events. Neutrophils infiltrate the wound site and basal epithelial cells proliferate; with time, neutro-phils are replaced by macrophages, granulation tissue ap-pears, neovascularization occurs, fibroblasts proliferate, and collagens continue to accumulate. In granulation tissue, the appearance of myofibroblasts contributes to woun