Abstract:
Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast
activity results in abnormal collagen deposition. Excessive inflammation is a characteristic
feature of keloids but little is known about the underlying ultrastructural features of keloids
related to collagen processing, fibril and fibre formation, the interaction between fibroblasts and
associated collagen fibres and mast cells. In this study, the ultrastructure of the dermis of keloid
patients was evaluated using light and transmission electron microscopy techniques. Abnormal
intracellular premature collagen fibril formation was observed. Phagocytosis of collagen fibrils by
mast cells was a common ultrastructural feature of keloid tissue as was a close or direct association between fibroblasts and mast cells. Based on these findings and recent advances in
knowledge related to collagen synthesis, fibril formation and processing we hypothesise that
keloid formation is primary due to abnormal collagen synthesis where the consequent
accumulation of collagen fibres causes increased mast cell recruitment and collagen
phagocytosis. Subsequent release of mast cell derived mediators then promotes further
collagen synthesis. The observation of early formation in keloid tissue of premature insoluble
collagen fibrils supports previous studies that enzymes such as procollagen C-proteinase are
important early therapeutic targets.
