What Is a Fibroblast?

The fibroblast cell body is spindle-shaped or irregularly triangular, with an oval nucleus in the center, and cytoplasmic protrusions, which are radial when growing. Except for true fibroblasts, all mesoderm-derived tissues, such as myocardium, smooth muscle, osteoblasts, and vascular endothelium, are often in this state. In addition, when the morphology of cells in culture is similar to fibroblasts, they can be called fibroblasts. Fibroblasts cultured in vitro are mostly spindle-shaped, polygonal, and flat-star-shaped, etc., and their morphology can be changed according to the changes of the cell's function and the physical properties of the cells. Under the electron microscope, the cytoplasm showed abundant rough endoplasmic reticulum, free ribosomes, and developed Golgi complex. Fibroblasts in the mature or resting state have smaller cell bodies and long spindle shapes, and both the rough endoplasmic reticulum and Golgi complex are underdeveloped. It has a strong ability to divide and proliferate, has strong adaptability, and is one of the most easily cultured animal cell types.

Fibroblasts are the main cellular component of loose connective tissue. The cells are spindle-shaped or flat-stellate, with protrusions. According to different functional activities, cells are divided into fibroblasts and fibroblasts.

Fibroblasts are cells with strong functional activities, with large cells and nuclei, clear outlines, large and obvious nucleoli, weak basophilic cytoplasm, and obvious protein synthesis and secretion activities. Fibroblasts at maturity or resting state Cells, cell bodies become smaller, long spindle-shaped, rough endoplasmic reticulum and Golgi complex are underdeveloped, known as fibroblasts. Fibrocytes are not active, cell outlines are not obvious, small nuclei are stained, nucleoli are not obvious, and cytoplasm is small. Stimulated by factors such as trauma, some fibroblasts can be transformed into naive fibroblasts, their functional activities can be restored, and they can participate in the repair of tissue damage. ^[1]

Fibroblasts take up the required amino acids, such as proline and lysine, and synthesize pre- polypeptide chains on the ribosomes of the rough endoplasmic reticulum. After the polypeptide chains are transported to the Golgi complex, they form procollagen molecules. The procollagen molecules are carried to the cell surface by secretory vesicles and then released outside the cell by exocytosis. Under the catalysis of procollagen peptidase, the tail of each pre-alpha polypeptide chain is removed to become a procollagen molecule. Many procollagen molecules are arranged in rows in parallel, and are combined into collagen fibrils with periodic horizontal stripes. Collagen fibrils are combined with each other to form collagen fibers.

Fibroblasts are the most common cells in connective tissue and are differentiated from embryonic mesenchymal cells. In connective tissue, fibroblasts also exist in the form of their mature state, fibrocytes, and the two can transform each other under certain conditions. Different types of connective tissue contain different numbers of fibroblasts. Generally, the number of fibroblasts in loose connective tissue is less than the number of fibroblasts in dense connective tissue of the same volume. Therefore, dense connective tissue such as dermis is used as the site for isolation and culture of fibroblasts. ^[2]

Fibroblasts have a variety of morphologies, such as fusiform, mostly angular, and flat star. The morphology of fibroblasts can be changed according to the changes in the function of the cells and the physical properties of the cells. Fibroblasts have larger cell bodies, weaker basophilic cytoplasm, larger elliptical nuclei, loose chromatin, lighter coloration, and prominent nucleoli. Under the electron microscope, the cytoplasm showed abundant rough endoplasmic reticulum, free ribosomes, and a developed Golgi complex, indicating that it has the function of synthesizing and secreting proteins.

The performance of fibroblasts in general wound repair. Various wounds will cause different degrees of cell degeneration, necrosis and tissue defect. Tissue repair must be performed through cell proliferation and formation of intercellular matrix. Fibroblasts play a very important role in this repair process. Taking the wound healing process as an example, fibroblasts proliferate in large numbers through mitosis, and begin to synthesize and secrete a large amount of collagen fibers and matrix components from 4 to 5 or 6 days. Together with new capillaries, granulation tissue is formed to fill wound tissue defects. To create conditions for epidermal cell coverage. In wound healing, fibroblasts are mainly derived from local fibroblasts and undifferentiated mesenchymal cells of the dermal papilla layer, as well as fibroblasts and pericytes around blood vessels. When visceral injury occurs, the fibroblasts involved in the repair process mostly come from the interstitial and envelope, as well as the connective tissue under the submucosa or serosa. Some people think that the large number of fibroblasts gathered in the wound during the wound healing process is, on the one hand, derived from fibroblasts through proliferation and division, and on the other hand, it is more composed of adjacent mesenchymal cells, fibroblasts and pericytes. Wait for the evolution or swim to the wound. In the later stage of wound repair, fibroblasts participate in tissue reconstruction after repair by secreting collagenase. Under certain pathological conditions, granulation tissue or proliferative tissue mass with fibroblasts as the main cell component can also calcify in non-bone tissue, causing ectopic ossification. However, it is not very clear about the participating cells of ectopic ossification and its mechanism. Undifferentiated mesenchymal cells, fibroblasts, endothelial cells and pericyte cells can be classified as induced bone progenitor cells. Participate in this process. ^[3]