Introduction:
Necrosis is defined as irreversible cell damage and eventual cell death caused by pathogenic processes. It is an uncontrolled cell death that causes enlargement of the cell organelles, plasma membrane rupture and ultimately cell lysis, and leakage of intracellular contents into surrounding tissue, resulting in tissue injury.
It is the death of cells or tissue that occurs when the cells in a certain area of the body die, usually as a result of infection, injury, or lack of blood flow.
Necrosis is different from apoptosis, which is a natural, programmed process of cell death that occurs during development or in response to cellular damage
Necrosis can occur in any part of the body, but it is most common in tissues that are particularly vulnerable to injury or infection, such as skin, muscle, and organs.
Causes:
Hypoxia: Necrosis can occur when there is a lack of oxygen in the body, which can be caused by respiratory failure or other conditions that affect the delivery of oxygen to the tissues.
Ischemia: Necrosis can occur when there is a lack of blood flow to a particular area of the body. This can be caused by a blocked artery or vein, or by a drop in blood pressure.
Toxins: Certain toxins, such as alcohol, can cause necrosis by damaging cells and tissues.
Infection: Bacteria, viruses, and other pathogens can cause necrosis by attacking and killing cells in the body.
Physical injury: Necrosis can occur as a result of physical injury to the body, such as a puncture wound, a burn, or a crush injury.
Immunological reactions: Necrosis can also be caused by an immune system reaction to certain substances, such as a drug allergy or an autoimmune disorder.
Types:
Coagulative necrosis
This type of necrosis occurs when the cells in a tissue die, but the tissue itself maintains its structure. Coagulative necrosis is typically seen in organs that have a good blood supply, such as the liver and kidney. The cells seem anucleate, eosinophilic, and with preserved structure under the microscope. Phagocytosis and leukocytes eventually remove the dead cells.
Caseous necrosis
The name caseous means “cheesy,” referring to the whitish look of the necrotic area. This type of necrosis occurs when the cells in a tissue die and the tissue becomes cheese-like in consistency. Caseous necrosis is typically seen in tissues that have been infected with tuberculosis.
Gangrenous necrosis
This type of necrosis occurs when the cells in a tissue die and the tissue becomes black and foul-smelling. Gangrenous necrosis is typically seen in tissues that have a poor blood supply, such as the toes and fingers.
Fat necrosis
This type of necrosis occurs when fat cells in the body die, typically as a result of injury or inflammation. The release of pancreatic enzymes causes the fat cells in the peritoneal cavity to liquefy. These liquified fat cells subsequently interact with calcium to form chalky white regions. This is apparent under a microscope as basophilic calcium deposits on the boundaries of necrotic fat cells. Fat necrosis develops in breast tissue as a result of fat saponification.
Liquefactive necrosis
This type of necrosis occurs when the cells in a tissue die and the tissue becomes soft and liquid. Liquefactive necrosis is typically seen in tissues that have a poor blood supply, such as the brain.
Fibrinoid necrosis
This type of necrosis occurs when the cells in a tissue die and the tissue becomes hardened and stiff. Fibrinoid necrosis is typically seen in tissues that have been damaged by an immune system reaction, such as in autoimmune diseases.
Features:
It is important to note that the specific features of necrosis may vary depending on the cause and location of the tissue damage.
Cell death: Necrosis is characterized by the death of cells in a particular area of the body.
Tissue damage: Necrosis can cause damage to the tissues in the affected area, leading to swelling, pain, and other symptoms.
Inflammation: Necrosis can cause inflammation in the affected area, which may lead to swelling, redness, and pain.
Discoloration: Necrosis can cause a change in the color of the skin or other tissues, such as turning pale or blue in the case of ischemic necrosis or becoming black and foul-smelling in the case of gangrenous necrosis.
Release of fluids: Necrosis can cause the release of fluids, such as blood or pus, from the affected area.
Spread of infection: Necrosis can also lead to the spread of infection if the dead tissue is not properly removed or if bacteria or other pathogens are present in the affected area.
Mechanism:
The mechanism of necrosis, or the process by which cells or tissues die, can vary depending on the cause of the necrosis. However, there are some general mechanisms that are common to many types of necrosis.
One mechanism of necrosis is cell injury, which can be caused by physical trauma, toxins, or other factors that damage the cell membrane or other cellular structures. When the cell membrane is damaged, it can allow harmful substances to enter the cell, leading to cell death.
Another mechanism of necrosis is ischemia, or a lack of blood flow to the cells. When cells do not receive enough oxygen and nutrients, they can become damaged and die. Ischemia can be caused by a blockage in the blood vessels or a drop in blood pressure.
Fig: Stages of necrosis
Inflammation can also contribute to necrosis by causing the release of chemicals that can damage cells and tissues. This can occur in response to infection, injury, or other stimuli.
Finally, some types of necrosis are caused by the immune system, which can attack and kill cells in the body as part of an immune response. This can occur in autoimmune diseases, drug allergies, and other conditions.
Difference between apoptosis and necrosis:
Apoptosis and necrosis are both processes of cell death, but they differ in several important ways:
Morphology: Apoptosis is characterized by the shrinkage of cells and the fragmentation of their DNA into small, discrete pieces. Necrosis is characterized by the swelling and disintegration of cells, with the release of their contents into the surrounding tissue.
Mechanism: Apoptosis is a programmed process of cell death that occurs as part of normal development or in response to cellular damage. Necrosis is an uncontrolled process of cell death that occurs as a result of injury or disease.
Inflammation: Apoptosis does not typically trigger an immune response or inflammation, while necrosis often does.
Role in the body: Apoptosis plays a vital role in the body by helping to maintain tissue homeostasis and removing damaged or unnecessary cells. Necrosis, on the other hand, is generally a harmful process that can cause tissue damage and lead to serious complications.
Tissue damage: Apoptosis usually does not cause significant tissue damage, as the cells are removed in a controlled manner. Necrosis, on the other hand, can cause significant tissue damage as the cells die and release their contents into the surrounding tissue.
Risk factors:
Infection: Certain infections, such as sepsis, can increase the risk of necrosis.
Chronic diseases: Certain chronic conditions, such as diabetes and cardiovascular disease, can increase the risk of necrosis.
Physical injury: Physical injuries, such as puncture wounds, burns, and crush injuries, can increase the risk of necrosis.
Drug use: Certain medications, such as chemotherapy drugs and nonsteroidal anti-inflammatory drugs (NSAIDs), can increase the risk of necrosis.
Poor circulation: Poor circulation, which can be caused by blocked arteries or veins or low blood pressure, can increase the risk of necrosis.
Aging: The risk of necrosis may increase with age, as the body becomes more vulnerable to injury and disease.
Smoking: Smoking can damage the blood vessels and increase the risk of necrosis.
Alcohol: Heavy alcohol use can increase the risk of necrosis by damaging cells and tissues.
Treatment:
The treatment of necrosis depends on the cause and extent of the tissue damage, as well as the presence of any underlying conditions or complications. It is important to follow your healthcare provider’s treatment recommendations and seek medical attention as soon as possible if you suspect that you have necrosis, as untreated necrosis can lead to serious complications.
Medications: Antibiotics may be used to treat or prevent infection, and medications may be used to control inflammation or improve blood flow to the affected area.
Surgery: In some cases, surgery may be necessary to remove the dead tissue and prevent the spread of infection.
Physical therapy: Physical therapy may be recommended to help improve mobility and function in the affected area.
Lifestyle changes: Making lifestyle changes, such as quitting smoking or reducing alcohol consumption, can help reduce the risk of necrosis and improve overall health.
Wound care: Proper wound care, including cleaning and dressing the wound, is important to prevent infection and promote healing.
References:
- Khalid, N. and Azimpouran, M., 2020. Necrosis.
- Ros U, Pedrera L, Garcia-Saez AJ. Partners in Crime: The Interplay of Proteins and Membranes in Regulated Necrosis. Int J Mol Sci. 2020 Mar 31;21(7):2412