Myofibroblasts

Myofibroblast
Histological section through testicular parenchyma of a boar. 1 Lumen of Tubulus seminiferus contortus, 2 spermatids, 3 , 4 spermatogonia, 5 Sertoli cell, 6 Myofibroblasts, 7 Leydig cells, 8 capillaries
Details
Identifiers
Latin	myofibroblastus
Code	TH H2.00.03.0.01013
Anatomical terminology []

A myofibroblast is a cell that is in between a fibroblast and a smooth muscle cell in phenotype.

There are many possible ways of myofibroblast development:

Myofibroblasts usually stain for the intermediate filament vimentin which is a general mesenchymal marker and "alpha smooth muscle actin" (human gene = ACTA2) and for palladin, which is a cytoskeletal actin scaffold protein. They are positive for other smooth markers like intermediate filament type desmin in some tissues, but may be negative for desmin in some others. Similar heterogeneous positivity may exist for almost every smooth muscle marker except probably a few which are positive only in contractile smooth muscles like metavinculin and smoothelin.

Some myofibroblasts (especially if they have a stellate form) may also be positive for GFAP.

Myofibroblasts are found subepithelially in many mucosal surfaces - for example, throughout almost the whole of the gastrointestinal and genitourinary tracts. Here they not only act as a regulator of the shape of the crypts and villi but also act as stem-niche cells in the intestinal crypts and as parts of atypical antigen-presenting cells. They have both support as well as paracrine function in most places.

In many organs like liver, lung, and kidney they are primarily involved in fibrosis. In the wound tissue they are implicated in wound strengthening by extracellular collagen fiber deposition and then wound contraction by intracellular contraction and concomitant alignment of the collagen fibers by integrin-mediated pulling on to the collagen bundles. Pericytes and renal mesangial cells are some examples of modified myofibroblast-like cells.

Myofibroblasts may interfere with the propagation of electrical signals controlling heart rhythm, leading to arrhythmia in both patients who have suffered a heart attack and in foetuses. Ursodiol is a promising drug for this condition.