Fibroblast is a type of cell that synthesizes extracellular matrix and collagen, which form the basic framework structure of biological connective tissue in animals and play an important role in tissue repair. As well as being present as fibroblasts, these cells exist in an alternative state, as fibrocytes. Fibroblast is the term used to describe these cells when they are in an activated state. Fibrocyte refers to a state in which cells are less active. The morphology of fibroblasts depends on their function and site of action. Fibroblasts extracted from a particular location can "remember" their original location and function when transplanted to another location in the body.

Fibroblast in Cutaneous Wound Repair

Under normal conditions, fibroblasts function to maintain tissue homeostasis by regulating the turnover of extracellular matrix (ECM). When tissues are injured, these cells are attracted to wound sites by the localized release of growth factors/cytokines such as platelet-derived growth factor (PDGF), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α), and then differentiate into myofibroblasts, a type of highly specialized, but ephemeral contractile cells. A major function of myofibroblasts is to synthesize ECM proteins, notably collagen types I-VI and XVIII, glycoproteins, and proteoglycans for normal growth, differentiation, and wound repair. Moreover, myofibroblasts also secrete many other matrix molecules including laminin and thrombospondin, glycosaminoglycans (GAGs), hyaluronic acid (HA), and heparan sulfuate (HS), as well as matrix-modifying proteins such as matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs). In addition to producing matrix components, myofibroblasts also generate contractile forces which bring together the edges of an open wound and therefore facilitate wound closure. However, excessive myofibroblast activities, including excessive contraction and over-production of ECM, are also the major cause of tissue fibrosis and scar formation.

Fibroblast in Cancer

Carcinoma associated fibroblasts (CAFs) are believed to influence tumor behavior and prognosis, and thus knowledge of their biology is of importance to a comprehensive understanding of cancer. The ability of CAFs to affect tumor growth partly depends on their ability to induce angiogenesis by autocrine and/or paracrine cytokines that promote the biological characteristics of tumor. In addition to classical growth factors including epidermal growth factor (EGF) and hepatocyte growth factor (HGF), novel CAF-secreted proteins (secreted frizzled related protein 1, IGF-like family member 1 and 2) and membrane molecules (integrin α11 and syndecan-1) have also been confirmed to possess cancer cell-supporting roles. These factors directly or indirectly stimulate tumor growth and survival, or enhance their migration and invasion.