Pathology of Scars and KeloidsScar formation is a natural process and part of the process of wound healing. This results in production of a tissue that is, to some extent, structurally and functionally different from the normal skin. Under a microscope, scar tissue is composed of fibrous tissue and collagen deposits. The scar structure is thicker and denser than the surrounding normal skin tissue. Below is the image of scar tissue under a microscope.
When we look at keloids under microscope, we notice that the top levels of skin, the epidermis, is relatively normal and deep parts of the skin, where the keloid tissue resides, is mostly made of excessive amounts of tightly packed collagen fibers randomly oriented in irregular sheets.
Collagen is produced by specialized cells, known as fibroblasts. Collagen is a group of naturally occurring proteins that are abundant in the human body and other animals and mammals. Collagen makes up about 25% to 35% of the whole-body protein content. It is made of three separate long chains of amino acids and forms a helix, which put side by side, form very thin fibers, known as collagen fibrils.
Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea, cartilage, bone, blood vessels, the gut, and intervertebral disc. Collagen is found in many parts of the human body. So far, 28 types of collagen have been identified and described. The five most common types are: Collagen I, which is mostly found in skin, tendon, vascular ligature, organs and bone (main component of the organic part of bone). Over 90% of the collagen in the body is of type one. Collagen II is mostly found in cartilage. It is the main component of cartilage tissue. Collagen III is known as reticulate collagen and is commonly found alongside type I collagen. Collagen IV is elemental to the structure of basement membranes, which are found in most tissues in the body. Collagen V is mostly found in cell surfaces, hair and placenta. The Collagen in keloid tissue is mostly Collagen I and III.