Saturday, February 25, 2012

Epitheialization and Acne Scar

Wikipedia: The arrow points to cells that have fused to form syncytia, and the arrowheads point to cells that are oriented to face the wound. Epithelialization occurs within 24 hours after the injury and is characterized by the detachment, migration, proliferation, and differentiation of cells at the base of the epidermis along the wound.

Another way to put it is that after an injury mitosis increases, therefore cell production increases and those newly formed cells migrate to any exposed dermis and provide a temporary protection.

Keratinocytes migrate without first proliferating. Migration can begin as early as a few hours after wounding. However, epithelial cells require viable tissue to migrate across, so if the wound is deep it must first be filled with granulation tissue.

Epithelialization is the second step in wound healing, the first step is inflammation, such as redness and heat, followed by epithelialization, then collagen synthesis, contraction, and remodeling.

The formation of granulation tissue in an open wound allows the reepithelialization phase to take place, as epithelial cells migrate across the new tissue to form a barrier between the wound and the environment.

Basal keratinocytes (skin stem cells) from the wound edges and dermal appendages such as hair follicles, sweat glands and sebacious (oil) glands are the main cells responsible for the epithelialization phase of wound healing. They advance in a sheet across the wound site and proliferate at its edges, ceasing movement when they meet in the middle.

Epithelial cells climb over one another in order to migrate. This growing sheet of epithelial cells is often called the epithelial tongue. The first cells to attach to the basement membrane. These basal cells continue to migrate across the wound bed, and epithelial cells above them slide along as well. The more quickly this migration occurs, the less of a scar there will be.

As keratinocytes migrate, they move over granulation tissue but underneath the scab (if one was formed), separating it from the underlying tissue. Epithelial cells have the ability to phagocytize debris such as dead tissue and bacterial matter that would otherwise obstruct their path.

Because they must dissolve any scab that forms, keratinocyte migration is best enhanced by a moist environment, since a dry one leads to formation of a bigger, tougher scab. As keratinocytes continue migrating, new epithelial cells must be formed at the wound edges to replace them and to provide more cells for the advancing sheet.

Proliferation behind migrating keratinocytes normally begins a few days after wounding and occurs at a rate that is 17 times higher in this stage of epithelialization than in normal tissues. Keratinocytes continue migrating across the wound bed until cells from either side meet in the middle, at which point contact inhibition causes them to stop migrating. When they have finished migrating, the keratinocytes secrete the proteins that form the new basement membrane.

Cells reverse the morphological changes they underwent in order to begin migrating; they reestablish desmosomes and hemidesmosomes and become anchored once again to the basement membrane. Basal cells begin to divide and differentiate in the same manner as they do in normal skin to reestablish the strata found in reepithelialized skin.

As we can see, scar formation is a problematic situation and the best choice is to prevent its formation. Early treatment of acne is the best choice to prevent scar formation.Once formed, a scar needs all the conditions that promote faster epithelilzation which proceeds 17 times faster than in normal tissue. Formation of new cells requires accelerated fat metabolism to produce all cell membrane lipids.

Boosting Coenzyme A formation cures acne and prevent scar formation. Moreover. it accelerates epithelialization even if scar has been formed.

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