Editing Fibroblast (section)

===Development===

The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the [[extracellular matrix]] (ECM), providing all such components, primarily the [[ground substance]] and a variety of [[fiber]]s. The composition of the ECM determines the physical properties of connective tissues.

Like other cells of connective tissue, fibroblasts are derived from primitive [[mesenchyme]]. Hence, they express the intermediate filament protein [[vimentin]], a feature used as a marker to distinguish their [[mesodermal]] origin.<ref>{{cite journal | vauthors = Dave JM, Bayless KJ | title = Vimentin as an integral regulator of cell adhesion and endothelial sprouting | journal = Microcirculation | volume = 21 | issue = 4 | pages = 333–344 | date = May 2014 | pmid = 24387004 | doi = 10.1111/micc.12111 | s2cid = 26292524 }}</ref> 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]].

Conversely, fibroblasts in some situations may give rise to epithelia by undergoing a mesenchymal to epithelial transition 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), as well as in wound healing and tumorigenesis.{{citation needed|date=June 2021}}