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Hepatocytes make up the liver and have subtypes based on their specific functions. There are two main types of hepatocytes, classified based on where they are located within the liver lobule: periportal hepatocytes and pericentral (centrilobular) hepatocytes. Between these two regions is Zone 2, which contains hepatocytes with features that fall somewhere in between.

Periportal hepatocytes: The cells are located closer to the portal vein and receive the highest supply of oxygen and nutrients. These cells are mainly responsible for energy-producing processes such as glucose production, fatty acid breakdown, cholesterol synthesis, and ammonia detoxification through the urea cycle.

Pericentral hepatocytes: The cells are located near the central vein. Here, the oxygen supply is low. These cells are highly specialized for detoxification. They contain abundant cytochrome P450 enzymes that help break down drugs, alcohol, and other potentially harmful substances. They also contribute to lipid metabolism and bile acid production.

The hepatocytes in Zone 2 bridge the gap between these two regions and carry out a mix of metabolic functions. Recent studies also suggest that some Zone 2 hepatocytes have a particularly strong ability to regenerate, helping the liver repair itself after injury.

Despite these functional differences, both hepatocyte subtypes work in collaboration for adequate liver function. These cells make up 70–80% of the liver’s total cell mass. These cells are responsible for protein synthesis, nutrient regulation, bile production, toxin removal, and liver regeneration. Understanding the different types of hepatocytes is crucial in understanding their dysfunction that leads to specific disease. In biomedical and regenerative research, hepatocytes are widely used in liver disease modeling, drug development, toxicology testing, and regenerative medicine research.

An immortalized cell line is called “immortal” because it can keep dividing in the lab for a very long time. The cells skip normal cell senescence. In contrast, most primary cells have a built-in limit to how many times they can divide. This happens because of something called telomeres, which are protective caps at the ends of chromosomes. Every time a cell divides, these telomeres get a little shorter, and eventually, the cell stops dividing altogether.

Immortalized cells get around this limit. One key reason is the activation of an enzyme called telomerase, which helps maintain the length of telomeres. By preventing them from shortening, the cells can continue dividing without hitting that usual “stop” signal. Another important factor is changes in the cell’s internal control system. Normally, cells have strict checks—controlled by proteins like p53 and Rb—that regulate growth and trigger cell death if something goes wrong. In immortalized cell lines, these control mechanisms are often weakened or switched off, allowing the cells to keep multiplying.

Some cells become immortal naturally, especially cancer cells. Others are made immortal in the lab using specific techniques like genetic modification or viral methods. It’s important to understand that “immortal” doesn’t mean the cells can’t die. It simply means they don’t have the usual limit on how many times they can divide, which makes them extremely useful for long-term research.

The human liver is formed by distinct cell types. The cells that are broadly categorized as hepatocytes and non-hepatocyte liver cells. These cells are highly organized and responsible for performing adequate liver function.

Hepatocytes make up more than 70% of the liver cells. They are responsible for bile production that aids in digestion, absorption of nutrients, conversion of nutrients into energy, storage of vitamins and glycogen, and production of essential proteins like albumin. The core mechanism involves the breakdown of medicines, alcohol, and other substances that enter the body. They are also unique because they can divide and replace damaged cells, giving the liver its well-known ability to regenerate after injury.

Non-hepatocyte liver cells create a supportive environment. It protects and regulates the liver’s environment. Kupffer cells act as the liver’s immune defenders, removing bacteria and worn-out cells from the bloodstream. Hepatic stellate cells normally store vitamin A, but when the liver is injured, they help repair damaged tissue and can also contribute to scarring if the damage persists. Liver sinusoidal endothelial cells control oxygen exchange, nutrients, and waste between the blood and liver tissue. Cholangiocytes line the bile ducts that aid in bile movement to the intestine.

In simple words, hepatocytes are the cells that can undertake the liver’s heavy lifting. In contrast, non-hepatocyte cells ensure the smooth running of the overall function. Both cell types coordinate for adequate nutrient processing, blood filtration, combat infections, or repair themselves after injury.

In a multicellular organism, every tissue is made up of specialized cell types that aid in carrying out a specific function. When a tissue is paired with its primary cell type, it means those cells are the key contributors to the structure and activity of that tissue.

For instance, epithelial cells make up epithelial tissue. The tissues are responsible for protective coverings and lining the body and major organ systems. Similarly, endothelial cells make up the endothelium that lines blood vessels, lymphatic vessels, and smooth muscle of the heart. It forms the largest system in the body.

Muscle tissue contains muscle cells (myocytes) that contract to move, and keratinocytes form the outermost skin. Nervous tissues are made up of neurons, which are specialized for sending signals from the brain to the other body parts.  

Connective tissues have their own specialized cell types as well. Fibroblasts are the main cells in forming connective tissue. Fibroblast aids in producing fibers and matrices that support surrounding structures. In cartilage, the primary cells are chondrocytes, whereas osteocytes are the mature cells found in bone. Blood is composed of distinct cell types, including red blood cells (RBCs), which play a major role in transportation of the oxygen throughout the body, and white blood cells (WBCs), which are responsible for the defense mechanism. Understanding the specialized cells and tissues is crucial for researchers to understand how organs function appropriately, what dysfunction causes the diseased state, how injuries heal, development of targeted therapy, regenerative medicine, etc.