Fibroblast

Fibroblasts are spindle-shaped cells of connective tissue that synthesize and remodel the extracellular matrix (ECM). They originate from mesenchymal cells and are widely distributed in connective tissues, where they maintain tissue architecture and provide structural support.

In normal tissue, fibroblasts produce collagen, especially type I and III, along with elastin, fibronectin, proteoglycans, and glycosaminoglycans. They secrete matrix metalloproteinases and their inhibitors to balance ECM synthesis and degradation. Through signals such as transforming growth factor beta (TGF-β) and mechanical cues, fibroblasts can become contractile myofibroblasts that express alpha-smooth muscle actin (α-SMA) and drive wound contraction during repair.

During development and repair, fibroblasts respond to injury by migrating into damaged areas, depositing provisional ECM, and organizing mature ECM as repair progresses. The population is heterogeneous, with tissue-specific subtypes and different activation states. Fibroblast activity can contribute to fibrosis when regulatory mechanisms fail, leading to excessive ECM deposition and scar formation.

In histology, fibroblasts appear as elongated, spindle-shaped cells with oval nuclei within a collagen-rich matrix. They are commonly identified by markers such as vimentin; they are generally negative for epithelial markers. Their function is central to tissue homeostasis, wound healing, and pathological remodeling.