fibroblasts

Fibroblasts are a type of mesenchymal cell found throughout connective tissues. They play a central role in producing, organizing, and remodeling the extracellular matrix (ECM), which provides structural support to tissues and influences cell behavior.

Morphology and distribution: fibroblasts are typically spindle-shaped with elongated processes. They are abundant in loose and dense connective tissues, including the dermis, tendons, ligaments, and organ stroma, where they maintain tissue integrity and respond to injury.

Functions: primary products of fibroblasts include ECM components such as collagen (mainly types I and III), elastin, fibronectin, and proteoglycans. They also secrete enzymes like matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) to remodel the ECM. In addition, fibroblasts release growth factors and cytokines that influence tissue repair, inflammation, and angiogenesis. They respond to mechanical cues and signaling molecules, adjusting ECM production accordingly.

Role in wound healing: following injury, fibroblasts proliferate and migrate to the wound site, depositing ECM to form granulation tissue. Some differentiate into myofibroblasts, which express alpha-smooth muscle actin and contribute to wound contraction. After repair, myofibroblasts typically diminish, though persistent activation can lead to scar formation and fibrosis.

Clinical relevance: dysregulated fibroblast activity is implicated in fibrotic diseases of the lung, liver, skin, and other organs. In cancer, cancer-associated fibroblasts within the tumor microenvironment remodel ECM and secrete signaling molecules that can support tumor growth and invasion.

Origin and diversity: fibroblasts arise from mesenchymal progenitors and can originate from various sources, including pericytes and circulating fibrocytes, with tissue-specific subtypes reflecting their local environment.