Role of growth factors in inflammation and repair

Abstract

Mononuclear cells generate a variety of hormone‐like proteins termed growth factors that are instrumental in the evolution and resolution of inflammatory reactions. Many of these growth regulatory molecules have multifunctional properties. For example, the mononuclear cell‐derived growth factors, platelet‐derived growth factor (PDGF), and transforming growth factor beta (TGF‐β), are potent leukocyte chemoattractants. In addition, TGF‐β, a product of platelets, T lymphocytes, and monocytes, appears to induce the transcription of other monocyte‐derived growth hormone genes. In this regard, picomolar concentrations of TGF‐β stimulate peripheral blood monocytes to transcribe the genes for PDGF (c‐sis), basic fibroblast growth factor (FGF), interleukin 1 (IL‐1), and tumor necrosis factor (TNF). Furthermore, levels of mRNA for TGF‐β, which is constitutively expressed in resting monocytes, are also increased by exogenous TGF‐β. Each of these monocyte products exhibits a plethora of biological activities on other cell types. T lymphocytes, in response to antigen, contribute to this network by secreting growth factors and lymphokines that regulate monocyte growth factor production.