Healing Process

Phases

Cell Phase

Tissue Phase

Contraction

Remolding

Components

(Section 2c. Components of Wound Healing continued)

The healing process is directed by a group of macrophage-produced polypeptides (protein fragments).  A polypeptide growth factor has many actions including the stimulation of cell proliferation and cell migration.  These messages cause the cells to react to product structures.  For example, these messages cause epithelial cells to produce epidermis and cause fibroblasts to make collagen.

A large variety of “polypeptide growth factors” have been identified and named.  Although each has a predominant function on a specific cell, it now appears that essentially all growth factors have a multitude of actions.  Epidermal growth factor (EGF) is a key component for re-epithelialization of a partial-thickness wound, and addition of EGF to the wound surface increases re-epithelialization.  Monocytes and macrophages are thought to be the main producers of growth factors; however, all skin cells, including fibroblasts and keratinocytes, play an important role in secreting growth factors.

Once formed, the growth factors can be rapidly deactivated by wound proteases; i.e., those released from white cells, mainly neutrophils.  The wound is activated to produce excess proteases, probably in an attempt to break down surface dead tissue.  Surface exudates is a rich source of such proteases, especially the class of metalloproteases.

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