Effect of plasminogen on wound healing in mice

Wound healing is a dynamic, interactive process critically involved in maintaining normal physiology and host defence of the body. Nevertheless, a healed wound (scar) is only about 70% as strong as normal skin. Moreover, reduced healing capability in the elderly, costs the American government more than $90 billion yearly due to hospitalisation. Apart from that, surgical scars can be a cause of psychological problem. Therefore, a new treatment that can speed up healing and decreases scarring is in great need. Plasminogen has shown significant healing acceleration effect in earlier studies on punctured tympanic membrane. Therefore, in the current study, we aim at investigating the healing quality in mice treated with plasminogen by functionality analysis. In the first part of the study, the correlation of skin tensile strength with gender, skin color and plasminogen genotypes of mice were analyzed. In the second part of the study, the effects of plasminogen injection on the tensile strength of different types of wounds in wild-type mice and mice lacking plasminogen gene were analyzed. The studies on excision and incision wounds did not supply any data that significantly confirmed that plasminogen has a positive effect on the tensile strength of the wounds. When plasminogen was only administered for a limited period during the whole experimental process, the data did not give any overt conclusive effects. However, when the plasminogen was injected locally and daily for the entire duration of a burn study, the data showed clearly that plasminogen significantly improve the tensile strength of burn wounds. There are at least a couple of factors affecting the tensile strength of a mouse skin; gender, male skin is stronger, and skin color, fair skin i stronger, both had significant effect, whereas the genotype have no effect at all. Administering plasminogen has a positive effect on the tensile strength of the healed burn wounds when the mice were treated during the entire 28-day experimental period. In the other studies, too few animals were included to give any final conclusion