Wound Healing
Wound Healing - Chronic Wound
Every injury to the skin immediately triggers the body's own wound healing process. As a result, the natural protective and barrier function of the skin is restored within a short period of time.
The process of wound healing can be divided into different phases that chronologically overlap and build up on each other:
Cleansing- / Inflammatory Phase - Day 1 to 4
- Activation of blood coagulation
- Macrophages and granulocytes invade the tissue and start to clean the wound and fight any bacteria that might have infiltrated
- Characteristic symptoms of the process are redness and swelling of the wound
Granulation Phase - Day 3 to 12
- Fibroblasts invade the wound
- Collagen, elastin and other components of the extracellular matrix are secreted by fibroblasts and form temporary subcutaneous tissue
- Vascularisation occurs in the newly formed tissue
- The swelling disappears, the redness fades
Regenerative Phase - Day 6 to several weeks or months
- Keratinocytes migrate into the skin defect and start to close it, epithelialization and wound closure takes place - this occurs between day 6 and day 22
- The extracellular matrix is reorganized by the cells, this reorganization in the subcutaneous tissue takes place over a longer period of time - the maturation of the scar can take several weeks and up to months and years
Elastase plays a key role in wound healing
A fundamental process in the initial phase of wound healing is the enzymatic cleansing of the wound. Dead tissue is degraded along with elastin and collagen.
A key role is played during this phase by the destructive enzymes elastase and the matrix-metalloproteinases (MMPs). Some MMPs are activated by elastase.
In the normal process of wound healing, the destructive enzymes are deactivated through a complex regulatory mechanism, following completion of the cleansing phase.
The chronic wound gets trapped in the inflammatory phase.
If there is a disturbance in the interplay of the enzymes during the process of wound healing, specifically in the deactivation of MMPs, the wound can become destabilized. As a result, there can be a delay or even failure of the wound to heal - a chronic wound is the outcome.
The reasons of such disturbances can be numerous. Common causes include diseases such as diabetes, venous insufficiency or a zinc deficiency.