NIH/3T3 Fibroblasts in cell culture

A fibroblast is a type of cell that synthesizes and maintains the extracellular matrix of many animal tissues. Cell culture is the process by which prokaryotic, or eukaryotic cells are grown under controlled conditions The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In Biology, the extracellular matrix ( ECM) is the Extracellular part of animal tissue that usually provides structural support to the cells Fibroblasts provide a structural framework (stroma) for many tissues, and play a critical role in wound healing. In animal tissue stroma (from Greek στρώμα meaning “bed” refers to the connective non-functional supportive framework of a biological cell, tissue Wound healing, or wound repair, is the body's natural process of regenerating dermal and epidermal tissue. They are the most common cells of connective tissue in animals. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) Fibroblasts were first discovered by Dr. Matthias De Oliveira in 1968.

The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the extracellular matrix. Fibroblasts secrete the precursors of all the components of the extracellular matrix, primarily the ground substance and a variety of fibres. Ground substance is a term for the non-collagenous components of Extracellular matrix. Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. The composition of the extracellular matrix determines the physical properties of connective tissues.

Fibroblasts are morphologically heterogeneous with diverse appearances depending on their location and activity. Though morphologically inconspicuous, ectopically transplanted fibroblasts can often retain positional memory of the location and tissue context where they had previously resided, at least over a few generations. In Medicine an ectopia is a displacement or malposition of an organ of the body

Unlike the epithelial cells lining the body structures, fibroblasts do not form flat monolayers and are not restricted by a polarizing attachment to a basal lamina on one side, although they may contribute to basal lamina components in some situations (eg subepithelial myofibroblasts in intestine may secrete the α-2 chain carrying component of the laminin which is absent only in regions of follicle associated epithelia which lack the myofibroblast lining). In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The basal lamina is a layer of extracellular matrix on which Epithelium sits and which is secreted by the epithelial cells A Myofibroblast is a cell that is in between a Fibroblast and a Smooth muscle cell in differentiation In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists Laminin is the major non-collagenous component of the Basal lamina, such as those on which cells of an Epithelium sit Fibroblasts can also migrate slowly over substratum as individual cells, again in contrast to epithelial cells. While epithelial cells form the lining of body structures, it is fibroblasts and related connective tissues which sculpt the "bulk" of an organism.

Embryologic origin

Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme. Mesenchyme refers to loosely organized connective tissue present in the embryo regardless of origin Thus they express the intermediate filament protein vimentin, a feature used as a marker to distinguish their mesodermal origin. Vimentin is a member of the Intermediate filament family of proteins However, this test is not specific as epithelial cells cultured in vitro on adherent substratum may also express vimentin after some time.

In certain situations epithelial cells can give rise to fibroblasts, a process called epithelial-mesenchymal transition (EMT). Epithelial-mesenchymal transition (EMT is a program of development of biological cells characterized by loss of cell adhesion repression of E-cadherin expression

Conversely, fibroblasts in some situations may give rise to epithelia by undergoing a mesenchymal to epithelial transition (MET) and organizing into a condensed, polarized, laterally connected true epithelial sheet. This process is seen in many developmental situations (eg. nephron and notocord development). A nephron (from Greek νεφρός (nephros meaning "kidney" is the basic structural and functional unit of the Kidney. The notochord is a flexible rod-shaped body found in Embryos of all Chordates It is composed of cells derived from the Mesoderm and defines the

Structure and function

Fibroblasts have a branched cytoplasm surrounding an elliptical, speckled nucleus having one or two nucleoli. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The nucleolus (also called nucleole) is a structure found within the nucleus in which Ribosomal RNA is transcribed. Active fibroblasts can be recognized by their abundant rough endoplasmic reticulum. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle Inactive fibroblasts, which are also called fibrocytes, are smaller and spindle shaped. They have a reduced rough endoplasmic reticulum. Although disjointed and scattered when they have to cover a large space, fibroblasts when crowded often locally align in parallel clusters.

Fibroblasts make collagens, glycosaminoglycans, reticular and elastic fibers, and glycoproteins found in the extracellular matrix. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Glycosaminoglycans (GAGs or mucopolysaccharides are long unbranched Polysaccharides consisting of a repeating Disaccharide unit Reticular fibers or reticulin is a histological term used to describe a type of Structural fiber composed of Type III collagen. Elastic fibers (or yellow fibers) are bundles of Proteins ( Elastin) found in Connective tissue and produced by Fibroblasts and Not to be confused with Peptidoglycan. Glycoproteins are proteins that contain Oligosaccharide chains ( Glycans) covalently attached In Biology, the extracellular matrix ( ECM) is the Extracellular part of animal tissue that usually provides structural support to the cells Growing individuals' fibroblasts are dividing and synthesizing ground substance. Tissue damage stimulates fibrocytes and induces the mitosis of fibroblasts. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei

Secondary actions

Mouse embryonic fibroblasts (MEFs) are often used as "feeder cells" in human embryonic stem cell research. Stem cells are cells found in most if not all multi-cellular Organisms. However, many researchers are gradually phasing out MEF's in favor of culture media with precisely defined ingredients of exclusively human derivation. Further, the difficulty of exclusively using human derivation for media supplements is most often solved by the use of "defined media" where the supplements are synthetic and achieve the primary goal of eliminating the chance of contamination from derivative sources.

See also

• fibrocartilage callus
• Fibrous connective tissue
• 3T3 cells

External links

• fibroblast at eMedicine Dictionary
• UIUC Histology Subject 240
• MedEd at Loyola Histo/practical/ctproper/hp3-15.html