Fibroblasts are the cells that make up the structural framework or stroma composed of the extracellular matrix and collagen in animal tissues. These cells are the most common type of connective tissue in animals, and are important for wound healing. Fibroblast transfection is a commonly used method in molecular and cell biology research, fibroblast transfection reagents are commercially available for both fibroblast cell lines and primary cells. As depicted below, fibroblast cells are large and flat, with elongated processes protruding from the body of each cell, creating the spindle-like appearance of the cell, the nucleus in the body of the cell, is oval.
Connective tissue is one of four main types of tissue in the body. The others are epithelial, muscle, and nervous tissue. Connective tissue is a fibrous tissue made largely of collagen, the most abundant protein in mammals. There are many kinds of connective tissue. These include, loose, dense, elastic, reticular, and adipose connective tissue. In addition, there are embryonic connective tissues, as well as specialized connective tissues, which include bone, cartilage, and blood.
Fibroblasts and the Extracellular Matrix:
Dense connective tissues, in particular, is used to form ligaments and tendons. Ligaments are rope-like tissue bundles that attach bones to each other and are found at the joints. Tendons attach bones to the surrounding skeletal muscle tissue. Dense connective tissue also makes up the dermis. The tissue matrix is made almost entirely of collagen, which is the most abundant protein in mammals. Interspersed between the collagen fibers of dense connective tissue, are fibroblasts, which produce a collagen subunit, tropocollagen, which is used to construct larger collagenous aggregates. Fibroblasts also produce glycoproteins and polysaccharides for the ground substances, a gel-like material that surrounds collagen fibers of dense connective tissue, forming an “extracellular matrix”, which contributes to the structural integrity of ligaments and tendons, determines the physical properties of connective tissue. In addition, fibroblasts have a tissue repair function, and wounds stimulate fibroblast production. Collagen’s ubiquity makes fibroblasts the most common cells of connective tissue in mammals.
Fibroblasts and Fibrocytes:
Fibroblasts come in various shapes and sizes, as well as in an activated and unactivated form. Fibroblasts refer to the activated form (the suffix “blast” refers to a metabolically active cell), while fibrocytes are considered less active. However, often times, both fibroblasts and fibrocytes are referred to as fibroblasts. Fibroblasts can be distinguished from fibrocytes by their abundance of rough endoplasmic reticulum and relatively larger size
Fibroblasts are derived from primitive mesenchyme, like all connective tissue cells. Their ability to express filament protein vimentin alludes to their mesodermal origin.