Plasminogen activation in healing human wounds

Area of Science:

• Biochemistry
• Cell Biology
• Dermatology

Background:

• Tissue injury initiates a provisional matrix rich in fibrin.
• This matrix is subsequently replaced by granulation tissue.
• Extracellular proteolysis by fibrinolytic enzymes drives this replacement process.

Purpose of the Study:

• To investigate the cells and molecular components involved in plasminogen activation during human skin wound healing.
• To elucidate the roles of specific enzymes and receptors in the wound healing cascade.

Main Methods:

• Combined immunohistological and zymographic analysis of iatrogenically created human skin wounds.
• Utilized fibrin(ogen)-specific staining to track matrix degradation.
• Examined the localization and activity of plasminogen, urokinase-type plasminogen activator (uPA), and its receptor (uPA-R).

Main Results:

• Fibrin-containing provisional matrix was progressively removed.
• Plasmin(ogen) was consistently present and associated with granulation tissue cells, particularly monocytes/macrophages and fibroblasts.
• uPA and its receptor (uPA-R) were localized to monocytes/macrophages and fibroblasts, with active uPA detected.
• No tissue-type plasminogen activator (tPA) staining was observed.

Conclusions:

• Monocytes/macrophages and fibroblasts are crucial for wound healing.
• These cells mediate urokinase-type plasminogen activator (uPA)-dependent plasminogen activation in healing human skin wounds.
• The findings highlight a specific enzymatic pathway critical for tissue repair.