Fibroblast
Encyclopedia
A fibroblast is a type of cell
that synthesizes the extracellular matrix
and collagen
, the structural framework (stroma
) for animal tissues, and plays a critical role in wound healing
. Fibroblasts are the most common cells of connective tissue
in animals.
s are two states of the same cells, the former being the activated state, the latter the less active state, concerned with maintenance and tissue metabolism. Currently, there is a tendency to call both forms fibroblasts. The suffix "blast" is used in cellular biology to denote a stem cell
or a cell in an activated state of metabolism
.
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. This remarkable behavior may lead to discomfort in the rare event that they stagnate there excessively.
and a variety of fibers. The composition of the extracellular matrix determines the physical properties of connective tissues.
Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme
. Thus they express the intermediate filament protein vimentin
, a feature used as a marker to distinguish their mesodermal origin. 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).
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 (e.g. nephron
and notocord development).
surrounding an elliptical, speckled nucleus
having one or two nucleoli. Active fibroblasts can be recognized by their abundant rough endoplasmic reticulum
. 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 collagen
s, glycosaminoglycan
s, reticular
and elastic fibers
, glycoprotein
s found in the extracellular matrix
and cytokine TSLP
. Growing individuals' fibroblasts are dividing and synthesizing ground substance. Tissue damage stimulates fibrocytes and induces the mitosis
of fibroblasts.
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 (e.g. 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). 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.
The life span of a fibroblast, as measured in chick embryos, is 57 ± 3 days.
research. However, many researchers are gradually phasing out MEFs 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.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
that synthesizes the extracellular matrix
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
and collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, the structural framework (stroma
Stroma (animal tissue)
In animal tissue, stroma refers to the connective, supportive framework of a biological cell, tissue, or organ.The stroma in animal tissue is contrasted with the parenchyma.Examples include:* Stroma of iris...
) for animal tissues, and plays a critical role in wound healing
Wound healing
Wound healing, or cicatrisation, is an intricate process in which the skin repairs itself after injury. In normal skin, the epidermis and dermis exists in a steady-state equilibrium, forming a protective barrier against the external environment...
. Fibroblasts are the most common cells of connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
in animals.
Background information
Fibroblasts and fibrocyteFibrocyte
A fibrocyte is an inactive mesenchymal cell, that is, a cell showing minimal cytoplasm, limited amounts of rough endoplasmic reticulum and lacks biochemical evidence of protein synthesis.The term fibrocyte contrasts with the term fibroblast...
s are two states of the same cells, the former being the activated state, the latter the less active state, concerned with maintenance and tissue metabolism. Currently, there is a tendency to call both forms fibroblasts. The suffix "blast" is used in cellular biology to denote a stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
or a cell in an activated state of metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
.
Fibroblasts are morphologically heterogeneous with diverse appearances depending on their location and activity. Though morphologically inconspicuous, ectopically transplanted fibroblasts can often retain positional memory
Pattern formation
The science of pattern formation deals with the visible, orderly outcomes of self-organisation and the common principles behind similar patterns....
of the location and tissue context where they had previously resided, at least over a few generations. This remarkable behavior may lead to discomfort in the rare event that they stagnate there excessively.
Embryologic origin
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 substanceGround substance
Ground substance is a term for the non-cellular components of extracellular matrix which contain the fibers.It is usually not visible on slides, because it is removed during the preparation process....
and a variety of fibers. The composition of the extracellular matrix determines the physical properties of connective tissues.
Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme
Mesenchyme
Mesenchyme, or mesenchymal connective tissue, is a type of undifferentiated loose connective tissue that is derived mostly from mesoderm, although some are derived from other germ layers; e.g. some mesenchyme is derived from neural crest cells and thus originates from the ectoderm...
. Thus they express the intermediate filament protein vimentin
Vimentin
Vimentin is a type III intermediate filament protein that is expressed in mesenchymal cells. IF proteins are found in all metazoan cells as well as bacteria. IF, along with tubulin-based microtubules and actin-based microfilaments, comprise the cytoskeleton...
, a feature used as a marker to distinguish their mesodermal origin. 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
Epithelial-mesenchymal transition
Epithelial-mesenchymal transition or transformation is a hypothesized program of development of biological cells characterized by loss of cell adhesion, repression of E-cadherin expression, and increased cell mobility...
(EMT).
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 (e.g. nephron
Nephron
The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system, which is not part of the nephron....
and notocord development).
Structure and function
Fibroblasts have a branched cytoplasmCytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
surrounding an elliptical, speckled nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
having one or two nucleoli. Active fibroblasts can be recognized by their abundant rough endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
. 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 collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
s, glycosaminoglycan
Glycosaminoglycan
Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. The repeating unit consists of a hexose or a hexuronic acid, linked to a hexosamine .-Production:Protein cores made in the rough endoplasmic reticulum are posttranslationally...
s, reticular
Reticular fiber
Reticular fibers or reticulin is a histological term used to describe a type of fiber in connective tissue composed of type III collagen. Reticular fibers crosslink to form a fine meshwork...
and elastic fibers
Elastic fibers
Elastic fibres are bundles of proteins found in extracellular matrix of connective tissue and produced by fibroblasts and smooth muscle cells in arteries. These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed...
, glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s found in the extracellular matrix
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
and cytokine TSLP
TSLP
Thymic stromal lymphopoietin is a protein belonging to the cytokine family. It is known to play an important role in the maturation of T cell populations through activation of antigen presenting cells....
. Growing individuals' fibroblasts are dividing and synthesizing ground substance. Tissue damage stimulates fibrocytes and induces the mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
of fibroblasts.
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
Basal lamina
The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below....
on one side, although they may contribute to basal lamina components in some situations (e.g. subepithelial myofibroblasts in intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
may secrete the α-2 chain carrying component of the laminin
Laminin
Laminins are major proteins in the basal lamina , a protein network foundation for most cells and organs...
which is absent only in regions of follicle associated epithelia which lack the myofibroblast lining). 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.
The life span of a fibroblast, as measured in chick embryos, is 57 ± 3 days.
Secondary actions
Mouse embryonic fibroblasts (MEFs) are often used as "feeder cells" in human embryonic stem cellStem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
research. However, many researchers are gradually phasing out MEFs 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.