fibrocytes

Fibrocytes are circulating mesenchymal progenitor cells derived from the hematopoietic lineage that participate in tissue repair and fibrotic processes. They are found in peripheral blood and can migrate into injured tissues where they contribute to the formation of connective tissue. Unlike resident fibroblasts, fibrocytes originate in the bone marrow and are characterized by the co-expression of hematopoietic and extracellular matrix–producing markers.

Common surface markers include CD34 and CD45, indicating their hematopoietic origin, along with the ability to produce extracellular matrix components such as type I collagen and fibronectin. In response to tissue injury, fibrocytes are mobilized and recruited to sites of damage via chemokine signaling, where they can differentiate into fibroblast-like cells. During this differentiation they may express alpha-smooth muscle actin and contribute to the myofibroblast pool involved in wound contraction and matrix remodeling.

Functions and significance: fibrocytes participate in normal wound healing by supplying collagen and other matrix proteins and by secreting cytokines and growth factors that influence inflammation and tissue remodeling. However, excessive recruitment or activation of fibrocytes can contribute to pathological fibrosis in organs such as the lungs, skin, liver, and kidneys.

Clinical relevance: increased numbers of circulating or tissue-resident fibrocytes have been observed in various fibrotic diseases and may serve as biomarkers or therapeutic targets. Ongoing research seeks to clarify their precise roles, regulatory mechanisms, and potential for antifibrotic interventions.