The fibrogenic potential of pericytes is in part dependent upon their ability to transdifferentiate into other functional mesenchymal cell types. Over the past few years several studies have highlighted the pluripotent nature of pericytes. They have been shown both in vitro and in vivo to differentiate into osteoblasts, adipocytes, chondrocytes, and smooth muscle cells. Interestingly, pericytes also share a strong phenotypic similarity to a population of mesenchymal stem cells found in the adult bone marrow. The bone marrow is composed of two distinct cell lineages, the hematopoietic component and the supporting stroma, each with their own distinct population of stem cells. Bone marrow-derived mesenchymal stem cells can be identified by their expression of STRO-1, a cell surface protein whose function is as yet unknown. Interestingly, the STRO-1 antigen has also been shown to be expressed by both endothelial cells and microvascular pericytes in a number of different tissues. Furthermore, bone marrow stem cells also commonly express a-smooth muscle actin (a-SMA) in culture and have a phenotype more like that of pericytes than smooth muscle cells. Although a strong phenotypic similarity between pericytes and bone marrow-derived stem cells exists, further studies are needed before pericytes can classified as in situ stem cells.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.