Question

Describe the steps or features of wound healing that have counterparts in the development of a tumor. How does each feature contribute to tumor formation?

Answer 1

In order to repair the injured tissues body sets into motion an automatic series of events, known as the “cascade of healing,” .

It is divided into these four overlapping phases: Hemostasis, Inflammatory, Proliferative, and Maturation

Phase 1: Hemostasis Phase

• first phase of healing, begins at the onset of injury,
• objective - stop the bleeding.
• In this phase, the body activates its emergency repair system, the blood clotting system, and forms a dam to block the drainage.
• platelets come into contact with collagen, resulting in activation and aggregation.
• An enzyme called thrombin is at the center, and it initiates the formation of a fibrin mesh, which strengthens the platelet clumps into a stable clot.

Phase 2: Defensive/Inflammatory Phase

• focuses on destroying bacteria and removing debris—essentially preparing the wound bed for the growth of new tissue.
• a type of white blood cells called neutrophils enter the wound to destroy bacteria and remove debris.
• These cells often reach their peak population between 24 and 48 hours after injury, reducing greatly in number after three days.
• As the white blood cells leave, specialized cells called macrophages arrive to continue clearing debris.
• These cells also secrete growth factors and proteins that attract immune system cells to the wound to facilitate tissue repair.
• This phase often lasts four to six days and is often associated with edema, erythema (reddening of the skin), heat and pain.

Phase 3: Proliferative Phase

• To fill the wound.( shiny, deep red granulation tissue fills the wound bed with connective tissue, and new blood vessels are formed)
• contraction of the wound margins (the wound margins contract and pull toward the center of the wound).
• covering the wound (epithelialization). - epithelial cells arise from the wound bed or margins and begin to migrate across the wound bed in leapfrog fashion until the wound is covered with epithelium.
• The Proliferative phase often lasts anywhere from four to 24 days.

Phase 4: Maturation Phase

• Here the new tissue slowly gains strength and flexibility.
• Here, collagen fibers reorganize, the tissue remodels and matures and there is an overall increase in tensile strength (though maximum strength is limited to 80% of the pre-injured strength).
• The Maturation phase varies greatly from wound to wound, often lasting anywhere from 21 days to two years.

Changes in the microenvironment caused by tissue injury can permit the development of a tumour. Stem cells contribute to wound healing and tumour formation. Deregulated Hedgehog signalling is linked to the development of basal cell carcinoma; whereas, aberrant WNT signalling can result in a variety of epidermal tumours. Non-dividing, differentiating and dying epithelial cells can either positively or negatively influence tumour formation