Anatomy & Organs

Fibrocyte – structure, function & diseases

Fibrozyt

Fibrocytes are part of connective tissue . They are normally quiescent and have irregular processes that connect with the processes of other fibrocytes, giving the connective tissue a three-dimensional rigidity. If necessary, for example after a mechanical injury, fibrocytes can “wake up” from their rest and transform themselves back into fibroblasts by dividing in order to synthesize components of the extracellular matrix in the intercellular space.

What is a fibrocyt?

Fibrocytes are non-motile connective tissue cells and are therefore part of the extracellular matrix . The main feature is the irregular extensions that can connect to the extensions of other fibrocytes in the form of so-called tight and gap junctions, giving the connective tissue a three-dimensional structure of strength.

Tight junctions are characterized by narrow bands of membrane proteins that enclose the cells mutually, so that there is a very tight contact between the membranes of neighboring cells, which at the same time represents a diffusion barrier. In contrast, there is no direct membrane contact between two cells at gap junctions. The membranes are kept at a distance of about 2 to 4 nanometers, but are connected to each other by connexons made of proteins , which also allow a certain exchange of substances, including with messenger substances .

Unlike the fibroblasts from which they are derived, fibrocytes are biologically almost inactive. This means that they cannot synthesize elastic fibers or other components of connective tissue. In the case of injuries that require the body’s own repair mechanisms, fibrocytes can “come to life” again, divide and produce two fibroblasts at a time. The fibroblasts are able to produce necessary components of scar tissue .

Anatomy & Structure

Fibrocytes are immobile, i.e. stationary cells of the connective tissue with an elongated oval cell nucleus and irregular protuberances of the cytoplasm . They reach a size of about 50 µm. The cells arise from fibroblasts, which are the main component of connective tissue and, in contrast to fibrocytes, show biological activities. They constantly produce and synthesize components of the extracellular matrix, especially elastic fibers.The cell nucleus of the fibrocytes contains densely packed chromatin, i.e. densely packed chromosomes. A large number of mitochondria , the power plants of the cell, are integrated in the cytoplasm. In addition, the cytoplasm contains an above-average proportion of rough endoplasmic reticulum and many Golgi structures. The rough endoplasmic reticulum consists of a dynamically changing network of membranes, tubules, and cavities that are important for many metabolic processes, including those related to protein synthesis. The Golgi apparatus of a cell is an organelle surrounded by a membrane that plays a role in secretion production.

Function & Tasks

One of the most important tasks of the fibrocytes is to ensure a certain structural strength of the connective tissue through mutual cross-linking in a three-dimensional network. In addition, their task is to synthesize precursors of collagen as well as glycosaminoglycans and proteoglycans. Glycosaminoglycans are an important part of the extracellular matrix. They consist of linearly structured repeats of polysaccharide units and serve to store water in the tissue and as a biological lubricant.

Proteoglycans are large molecules made up of 40 to 60 glycosaminoglycans and a few proteins attached via an oxygen-glycosidic bond. Proteoglycans have a high water-binding capacity and also form the basic substance of tendons , cartilage and sliding surfaces in joints. They also form the main substance of the lubricants in joints and are also an important component of the extracellular matrix. In addition, they assume a kind of reserve function. In the event of an injury that requires activation of the body’s repair system, fibrocytes can be reactivated by dividing and giving birth to two fibroblasts each, which can perform the full range of activities of a fibroblast.

During wound healing, the fibroblasts that have been converted into fibroblasts and the “normal” fibroblasts appear primarily in the granulation and differentiation phase. The task of the fibroblasts is to provide the wound with temporary replacement tissue during the granulation phase and to supply it with building blocks from the extracellular matrix. In the subsequent differentiation phase, it is up to the fibrocytes and fibroblasts to contract the wound using collagen fibers and to synthesize the appropriate scar tissue. The process is assisted by macrophages , which break down necrotic tissue and blood clots and make the amino acids and other basic substances released as a result available for the formation of new tissue.

Diseases

Diseases and disorders related to fibrocytes can be caused by a lack of certain micronutrients, by underlying diseases or by one or more genetic defects. For example, scurvy , beriberi and pellagra are typical diseases caused by a lack of certain essential vitamins .Fibrocytes and fibroblasts are disturbed by the lack in their synthesis work to produce connective tissue components such as collagens and others, so that connective tissue loses its strength and bleeding, tooth loss and other damage can occur. However, the breakdown of collagen can also be caused by weightlessness, immobilization and as an undesirable side effect of prolonged treatment with cortisone. The opposite clinical picture exists in fibrosis or sclerosis . Fibrosis typically manifests itself as an abnormally increased production of interstitial connective tissue by fibrocytes and fibroblasts, which leads to a gradual loss of function in the affected organs.

Fibrosis can be caused by constantly recurring mechanical loads or by endogenous factors such as circulatory disorders or chronic inflammation. Well-known examples of loss of organ function due to fibrosis are pulmonary fibrosis and cirrhosis of the liver . Sclerosis is also caused symptomatically by increased collagen production, which leads to hardening in the affected tissue, such as in arteriosclerosis. Benign tumors of the connective tissue, fibromas and lipomas as well as malignant tumors such asFibrosarcoma or Liposarcoma .

Website | + posts

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.