Wound Repair - An Outline

Introduction

Wound healing is vital for the body's cellular and molecular events. In addition, wound healing helps in tissue regeneration. As a result of regeneration, the disfigured tissue can return to its original condition, thus attaining full tissue restoration.

What Is the Physiology of Wound Repair?

A wound is defined as a disturbance in the anatomic structure of tissue along with its functional loss. Wound healing in the skin is a dynamic process that begins right after the injury and might last up to a few years. It involves cellular, humoral (antibodies), and molecular processes. Skin wound closure occurs through tissue regeneration and repair. Regeneration is replacing or substituting the damaged tissue by the proliferation of the cells that have survived the injury or maturation and proliferation of the stem cells. The process of replacement of tissues by regeneration is seen mainly in the superficial epidermis, skin of the fetus, and mucosa. However, the adult skin mainly heals by the connective tissue deposition resulting in fibrosis and scar formation. The process of wound healing can be segregated into the below-mentioned phases:

• Hemostasis Phase - It takes place immediately after tissue injury and can last for 48 hours. The blood and lymphatic fluid exudate outside the tissue as soon as an injury occurs. In response to the injury, the blood vessels around the wound constrict and decrease blood flow. As a result, the clotting factors and platelets are activated to form the blood clot.

• Inflammatory Phase - The blood vessels dilate, releasing many white blood cells and platelets. They release more cytokines and chemical mediators that play a role in the inflammatory process. In this stage, degradation of collagen, fibroblastic transformation into new collagen, angiogenesis or growth of new blood vessels, and growth of new epithelial cells occur simultaneously. Chemical mediators like serotonin and histamine make the cell more permeable, resulting in the efflux of neutrophils. The neutrophils cause phagocytosis of the cells and bacteria and thus decontaminate the wound.

• Proliferative Phase - It does not have a specific type but is an ongoing process after wound injury. New blood vessels are formed, laying down new collagen fibers. New cells migrate toward the periphery of the wound and start the process of re-epithelialization.

• Maturation Phase - It begins around three weeks after wound injury and may last for many months depending upon the location. Extra collagen degrades, resulting in wound contraction. The new tissue attains maximum strength and elasticity. If collagen deposition occurs in granulation tissue, it results in scar formation, which has less strength and elasticity than the tissue which is not injured.

How Does an Infected Wound Heal?

Healing an infected wound differs from acute and non-infected wound healing. The wound healing process seizes in one of the four stages of wound healing, majorly in the inflammation phase resulting in more inflammation and causing more damage to the new tissue. In order to avoid complications like cellulitis, osteomyelitis, and septicemia, the infected wound is first treated with oral antibiotics, draining and removing the dead tissue, and covering the wound with an antimicrobial dressing rather than a normal surgical dressing. Then, granulation tissue is formed, and total removal of an infected portion is necessary for wound healing.

What Are the Factors That Affect Wound Healing?

Several other factors, like the individual's age, existing comorbidities, lifestyle, nutritional status, and status of the wounded area, govern the wound healing process.

• Diabetes - Diabetic patients often have peripheral neuropathy that results in ulceration. Ischemia is often seen in diabetic people. Peripheral neuropathy and ischemia complicate and delays the process of wound healing.

• Obesity - Obesity increases the chances of ischemia and thus reduces blood flow and oxygen to the tissue resulting in necrosis. Thus the healing process is delayed.

• Necrosis - It hinders wound healing and requires dead tissue to be removed before normal healing can start at the affected area.

• Nutritional Status - The nutritional status of old age people is low and hence there is delayed wound healing. Also, if there is inadequate protein in the diet, it decreases collagen and fibroblast formation, which affects wound healing.

• Alcohol - It reduces the formation of new blood vessels and collagen production and slows the healing process. Scarring can also be seen.

• Smoking - Smoking causes constriction of the blood vessels and decreases immunity resulting in wound infection.

• Chemotherapy - It decreases collagen production and inflammatory processes and delays wound healing.

• Steroids - Steroids have immunosuppressive and anti-inflammatory effects that delay the wound-healing process.

What Are the Clinical Considerations in Wound Management?

A few important things in wound management include preventing and controlling infection, maintaining adequate moisture in the tissues, treating edema, and preventing the wound from contamination and injury. Before seeking medical intervention for wound closure, the wound should be cleaned using normal tap water or 0.9 percent saline solution. The purpose of surgical dressing of the wound is to provide a moist environment to stop the wound from becoming dry, and also, the dressing should absorb the extra fluid or exudate released from the wound. In addition, the surgical dressing should have proper ventilation or airflow, prevent contamination, and be impervious to bacteria. Surgical reconstruction is possible with primary wound closure. Other techniques employed for wound closure are healing through secondary intention, negative pressure wound treatment, and tissue grafting.

What Is the Future of Wound Healing and Regeneration?

• Scarring is absent in fetal tissue healing. Therefore, research is conducted to explore its clinical importance in adult tissue healing.

• Cytokines and transforming growth factors like platelet-derived growth factors play a vital role in healing. Studies are ongoing to know the stage at which cytokines need to be supplied to the body and their adequate amount.

• It has been proven that hyperbaric oxygen can accelerate healing; however, the success ratio of this technique still needs to be determined.

• The use of stem cells is the most recent advancement in wound healing. However, ethical issues arising from stem cell use have hindered its exploration.

• Research is ongoing to explore the drugs that promote wound healing. For example, drugs like vitamins, iron, insulin, and thyroid hormones facilitate wound healing; hence, they are being explored.

Conclusion

Wounds are created both due to traumatic injuries and surgery. Maximum tissue restoration, healing, and reducing the aesthetic concerns of an individual are the primary areas of concern for doctors. Small and minor injuries in healthy and fit individuals heal well. Wound healing, in the case of larger injuries, is influenced by various factors like age, the presence of a disease, and an individual's physical state. Also, diabetes, heart diseases, infection, and cancer suppress the body's immune system, thus affecting the healing process.