Age related changes in the dermal mast cells and the associated changes in the dermal collagen and cells: A histological and electron microscopy study Publication date: Available online 22 May 2019 Source: Acta Histochemica Author(s): Sara Mohamed Naguib Abdel Hafez Abstract Mast cells are widely distributed bone marrow cells. They have a crucial role in the dermal aging process. The aim of the present study was to describe the biochemical and the histological changes that occur in the aged dermal mast cells and to demonstrate the associated changes in the dermal cells and fibers as well. Sixteen male albino rats were used and divided into two groups; the control group (8–10 weeks) and the aged group (20–22 weeks). The rats were decapitated then processed for further biochemical and histological studies. The mean area fraction for collagen fibers was measured. In the aged group, there was a significant increase in the skin histamine and heparin levels if compared with the control one. Furthermore, there was an apparent increase in intact and degranulated dermal mast cells if compared with the control one. The dermal collagen bundles were apparently decreased and appeared distorted with wide spacing. Additionally, there were apparently large sized eosinophils with more cytoplasmic granules. Direct contact between mast, fibroblast, and macrophage cells was noticed. The average area fraction of collagen fibers was significantly increased in the aged group if compared with the control one. It could be concluded that the secretory activity of dermal mast cells was significantly increased in the aged skin group. Also, this study demonstrated the implicated role of mast cell in aged skin changes. Further long-term studies are needed to validate the prophylactic or therapeutic potential by intentional hindering of mast cell degranulation in aged skin.