Mesenchymal stem cell-like properties in fibroblasts.

Fibroblasts are biologically dynamic and morphologically heterogeneous and are the most abundant connective tissue cells, with diverse structures depending on their location and activity. The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the extracellular matrix. Recent advances in our knowledge on pathophysiologic features of fibroblasts revealed that in some situations epithelial cells can give rise to fibroblasts by epithelial-mesenchymal transition (EMT) and conversely, in some other situations, fibroblasts may give rise to epithelia by undergoing a mesenchymal to epithelial transition (MET). Given an opportunity to differentiate to other cells, fibroblasts may foster a novel clue for in situ tissue repair and contribute to cellular mechanisms of mesenchymal stem cell-like features under normal or pathological conditions. They have also been shown to suppress immune responses in vitro. Because of these properties, fibroblasts have recently received a very high profile in the literature. This review summarizes our understanding of the origins, mesenchymal stem cell-like characteristics and potency of directed differentiation of fibroblasts. In addition, we also present the evidence that mesenchymal stem cells and fibroblasts share much more in common than previously recognized.