Objective: To investigate the effects of topical application of small dose of insulin on the wound healing of the scalded rats, so as to explore its mechanism.
Methods: The rats employed in the study were subjected to deep partial thickness burn and were divided into group A (with subcutaneous injection of isotonic saline into the rat wounds as control), B and C (with subcutaneous injection of 0.1 U and 1 U insulin in the rat wounds respectively) and D (with subcutaneous injection of 0.1 U insulin in the rat abdomen as control). The wound healing time and wound healing rate were assessed every other day after 3 postburn days (PBDs). The histological changes of the wounds after injection were examined, the changes in the cell cycle of epidermal cells in the wound were analyzed by flow-cytometry, and blood glucose concentration of each group was determined.
Results: The wound healing time in group B (18.36 +/- 4.12 d) was significantly shorter than that in other groups (A: 24.57 +/- 5.19 d, C: 21.46 +/- 2.97 d, D: 24.50 +/- 1.05 d, P < 0.01). The wound healing rate of the rats in group B in 5, 9, 11, 13, 15, 17 and 19 PBD was obviously higher than that in group A, and was markedly higher than that in group C on 17 PBD (P < 0.05 - 0.01). The epithelial layer was thinner with less epidermal nails but much more fibroblasts in epidermal layer in group A, while the epithelial layer was thicker with abundant epidermal nails in group B and C with many fibroblasts in the dermis. The amount of cells in S phase at 4 PBD in group B was dramatically higher than that in group A, and cells in G2M phase at 4 - 5 PBD in group B was also higher than that in group A and C (P < 0.05 - 0.01). The blood level of glucose in group A and B fluctuated between 3.42 to 4.62 mmol/L at 24 PBH, while that in group C and D decreased obviously 1 hour after injection (P < 0.01), but gradually returned to normal 4 hours after injection.
Conclusion: Local injection of small dose of insulin may accelerate burn wound healing due to its role in promoting the proliferation and division of the repairing cells.