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LocationFibroblast_header_cell_0_2_0 Connective tissueFibroblast_cell_0_2_1
FunctionFibroblast_header_cell_0_3_0 Extracellular matrix and collagen creationFibroblast_cell_0_3_1
LatinFibroblast_header_cell_0_5_0 fibroblastusFibroblast_cell_0_5_1
MeSHFibroblast_header_cell_0_6_0 Fibroblast_cell_0_6_1
THFibroblast_header_cell_0_7_0 Fibroblast_cell_0_7_1
FMAFibroblast_header_cell_0_8_0 Fibroblast_cell_0_8_1

A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing. Fibroblast_sentence_0

Fibroblasts are the most common cells of connective tissue in animals. Fibroblast_sentence_1

Structure Fibroblast_section_0

Fibroblasts have a branched cytoplasm surrounding an elliptical, speckled nucleus having two or more nucleoli. Fibroblast_sentence_2

Active fibroblasts can be recognized by their abundant rough endoplasmic reticulum. Fibroblast_sentence_3

Inactive fibroblasts (called fibrocytes) are smaller, spindle-shaped, and have a reduced amount of rough endoplasmic reticulum. Fibroblast_sentence_4

Although disjointed and scattered when they have to cover a large space, fibroblasts, when crowded, often locally align in parallel clusters. Fibroblast_sentence_5

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). Fibroblast_sentence_6

Fibroblasts can also migrate slowly over substratum as individual cells, again in contrast to epithelial cells. Fibroblast_sentence_7

While epithelial cells form the lining of body structures, it is fibroblasts and related connective tissues which sculpt the "bulk" of an organism. Fibroblast_sentence_8

The life span of a fibroblast, as measured in chick embryos, is 57 ± 3 days. Fibroblast_sentence_9

Relationship with fibrocytes Fibroblast_section_1

Fibroblasts and fibrocytes 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. Fibroblast_sentence_10

Currently, there is a tendency to call both forms fibroblasts. Fibroblast_sentence_11

The suffix "-blast" is used in cellular biology to denote a stem cell or a cell in an activated state of metabolism. Fibroblast_sentence_12

Fibroblasts are morphologically heterogeneous with diverse appearances depending on their location and activity. Fibroblast_sentence_13

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. Fibroblast_sentence_14

This remarkable behavior may lead to discomfort in the rare event that they stagnate there excessively. Fibroblast_sentence_15

Development Fibroblast_section_2

The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the extracellular matrix. Fibroblast_sentence_16

Fibroblasts secrete the precursors of all the components of the extracellular matrix, primarily the ground substance and a variety of fibers. Fibroblast_sentence_17

The composition of the extracellular matrix determines the physical properties of connective tissues. Fibroblast_sentence_18

Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme. Fibroblast_sentence_19

Thus they express the intermediate filament protein vimentin, a feature used as a marker to distinguish their mesodermal origin. Fibroblast_sentence_20

However, this test is not specific as epithelial cells cultured in vitro on adherent substratum may also express vimentin after some time. Fibroblast_sentence_21

In certain situations, epithelial cells can give rise to fibroblasts, a process called epithelial-mesenchymal transition (EMT). Fibroblast_sentence_22

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. Fibroblast_sentence_23

This process is seen in many developmental situations (e.g. nephron and notocord development), as well as in wound healing and tumorigenesis. Fibroblast_sentence_24

Function Fibroblast_section_3

Fibroblasts make collagen fibres, glycosaminoglycans, reticular and elastic fibers. Fibroblast_sentence_25

Growing individuals' fibroblasts are dividing and are synthesizing ground substance. Fibroblast_sentence_26

Tissue damage stimulates fibrocytes and induces the production of fibroblasts. Fibroblast_sentence_27

Inflammation Fibroblast_section_4

Besides their commonly known role as structural components, fibroblasts play a critical role in an immune response to a tissue injury. Fibroblast_sentence_28

They are early players in initiating inflammation in the presence of invading microorganisms. Fibroblast_sentence_29

They induce chemokine synthesis through the presentation of receptors on their surface. Fibroblast_sentence_30

Immune cells then respond and initiate a cascade of events to clear the invasive microorganisms. Fibroblast_sentence_31

Receptors on the surface of fibroblasts also allow regulation of hematopoietic cells and provide a pathway for immune cells to regulate fibroblasts. Fibroblast_sentence_32

Tumour mediation Fibroblast_section_5

Fibroblasts, like the tumor-associated host fibroblasts (TAF), play a crucial role in immune regulation through TAF-derived extracellular matrix (ECM) components and modulators. Fibroblast_sentence_33

TAF are known to be significant in the inflammatory response as well as immune suppression in tumors. Fibroblast_sentence_34

TAF-derived ECM components cause alterations in the ECM composition and initiate the ECM remodeling. Fibroblast_sentence_35

The ECM remodeling is described as changes in the ECM as a result of enzyme activity which can lead to degradation of the ECM. Fibroblast_sentence_36

Immune regulation of tumors is largely determined by the ECM remodeling because the ECM is responsible for regulating a variety of functions, such as proliferation, differentiation, and morphogenesis of vital organs. Fibroblast_sentence_37

In many tumor types, especially those related to the epithelial cells, ECM remodeling is common. Fibroblast_sentence_38

Examples of TAF-derived ECM components include Tenascin and Thrombospondin-1 (TSP-1), which can be found in sites of chronic inflammation and carcinomas, respectively. Fibroblast_sentence_39

Immune regulation of tumors can also occur through the TAF-derived modulators. Fibroblast_sentence_40

Although these modulators may sound similar to the TAF-derived ECM components, they differ in the sense that they are responsible for the variation and turnover of the ECM. Fibroblast_sentence_41

Cleaved ECM molecules can play a critical role in immune regulation. Fibroblast_sentence_42

Proteases like matrix metalloproteineases (MMPs) and the uPA system are known to cleave the ECM. Fibroblast_sentence_43

These proteases are derived from fibroblasts. Fibroblast_sentence_44

Secondary actions Fibroblast_section_6

Mouse embryonic fibroblasts (MEFs) are often used as "feeder cells" in human embryonic stem cell research. Fibroblast_sentence_45

However, many researchers are gradually phasing out MEFs in favor of culture media with precisely defined ingredients of exclusively human derivation. Fibroblast_sentence_46

Further, the difficulty of exclusively using human derivation for media supplements is most often solved by use of "defined media" where the supplements are synthetic and achieve the primary goal of eliminating the chance of contamination from derivative sources. Fibroblast_sentence_47

In view of the clinical application of stem cell derived tissues, the use of human fibroblast as feeders has been studied. Fibroblast_sentence_48

Whereas the fibroblasts are usually used to maintain pluripotency of the stem cells, they can also be used to facilitate development of the stem cells into specific type of cells such as cardiomyocytes. Fibroblast_sentence_49

See also Fibroblast_section_7


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