Myofibroblast

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Histological section through testicular parenchyma of a boar. 1 Lumen of Tubulus seminiferus contortus, 2 spermatids, 3 spermatocytes, 4 spermatogonia, 5 Sertoli cell, 6 Myofibroblasts, 7 Leydig cells, 8 capillaries

A Myofibroblast is a form of fibroblast cell that has differentiated partially towards a smooth muscle phenotype.

It can contract by using some of the cytoskeletal proteins that are normally found in smooth muscle cells, in particular a form of actin called alpha-smooth muscle actin. These cells are then capable of speeding wound repair by contracting the edges of the wound.

Early work on wound healing showed that granulation tissue taken from a wound, could contract in vitro (or in an organ bath) in a similar fashion to smooth muscle, when exposed to substances that cause smooth muscle to contract, such as adrenaline or angiotensin.

More recently it has been shown that fibroblasts can transform into myofibroblasts with photobiomodulation.

After healing is complete, these cells are lost through apoptosis and it has been suggested that in several fibrotic diseases (for example liver cirrhosis, kidney fibrosis) that this mechanism fails to work, leading to persistence of the myofibroblasts, and consequently expansion of the extracellular matrix (fibrosis) and contraction.

Similarly, in wounds that fail to resolve and become keloids or hypertrophic scars, myofibroblasts may persist, rather than disappearing by apoptosis.

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