GRANULATION TISSUE AS A CONTRACTILE ORGAN

TLDR

Granulation tissues contain fibroblasts that develop smooth‑muscle‑like characteristics, including an extensive cytoplasmic fibrillar system. The study demonstrates that fibroblasts in granulation tissue can differentiate into myo‑fibroblasts with smooth‑muscle‑like structure and function—evidenced by actomyosin content, immunolabeling, nuclear morphology, cell attachments, and pharmacological responses—indicating a key role in connective‑tissue contraction.

Abstract

CONTRACTING GRANULATION TISSUES CONTAIN FIBROBLASTS THAT DEVELOP CHARACTERISTICS TYPICAL OF SMOOTH MUSCLE: (a) They contain an extensive cytoplasmic fibrillar system. (b) They show immunofluorescent labeling of their cytoplasm with human anti-smooth muscle serum. (c) The nuclei show complicated folds and indentations, indicative of cellular contraction. (d) There are cell-to-cell and cell-to-stroma attachments. (e) It is possible to extract similar quantities of actomyosin (having the same adenosine triphosphatase activity) from granulation tissue and from pregnant rat uterus. (f) Strips of granulation tissue, when tested pharmacologically in vitro, behave similarly to smooth muscle. All these data support the view that, under certain conditions, fibroblasts can differentiate into a cell type structurally and functionally similar to smooth muscle and that this cell, the "myo-fibroblast," plays an important role in connective tissue contraction.