A fibroblast is a type of biological cell typically with a spindle shape[1] that synthesizes the extracellular matrix and collagen,[2] produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing.

Although disjointed and scattered when covering large spaces, fibroblasts often locally align in parallel clusters when crowded together.

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).

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

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.

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 fibers.

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

[12] However, many researchers are trying to phase out MEFs in favor of culture media with precisely defined ingredients in order to facilitate the development of clinical-grade products.

[13] In view of the potential clinical applications of stem cell-derived tissues or primary epithelial cells, the use of human fibroblasts as an alternative to MEF feeders has been studied.

[15] Fibroblasts from different anatomical sites in the body express many genes that code for immune mediators and proteins.