Effects of calcitonin on epidermal regeneration and collagen synthesis in rabbits with experimental wounds

The cellular and metabolic effects induced by calcitonin on regenerative epidermal cells, fibroblasts and collagen fibers during wound healing were studied in rabbits. Electron microscopy revealed marked changes at 2 and 5 days post-wounding in epidermal cells and fibroblasts in calcitonin-treated rabbits such as: an increase in keratohyaline granules, tonofilaments, polysomes and a hypertrophy of nuclei in the epidermal cells. Fibroblasts are hypertrophied and surrounded by large areas of mature collagen fibers, namely at 5 and 14 days. Electron microscopic autoradiography revealed an increase in the incorporation of 3H-thymidine mostly in the nuclear chromatin, 3H-uridine in the nucleoli, 3H-leucine in the endoplasmic reticulum, polysomes and newly formed keratin layers, and 3H-proline over fibroblasts and collagen fibers. Most of the cellular and metabolic effects are evident at 2.5 hours and gradually decline by 5 and 24 hours of hormone administration. Scanning electron microscopy showed changes in the keratin pattern and collagen fibers. At 5 days after wounding and calcitonin treatment, a typical scaly pattern of keratin can be noted while in controls it is smooth and homogeneous. At 14 days post-wounding the collagen fibers are hypertrophied, with an extensive network of fibrils in calcitonin-treated rabbits. These findings demonstrate that synthetic salmon calcitonin stimulates protein synthesis, keratinogenesis and collagen formation in epidermal cells and fibroblasts during wound healing.