J Thorac Cardiovasc Surg 2001;121:820-821
© 2001 The American Association for Thoracic Surgery
Reply
Makiko Ueda, MD
Department of Pathology, Osaka City University Medical School, Osaka, Japan
Reply to the Editor:
Beranek raises an interesting, albeit rather controversial point. Because of the presence of small turquoise dots in macrophages in our Fig 4, A and B, which show immunologic double staining for smooth muscle cells and macrophages, Beranek suggests that small fascicles of muscle fibrils are present within these macrophages. From this observation, and obviously being a proponent of the hypothesis that the vascular endothelial cell is the stem cell for neointimal formation after vessel wall injury, Beranek opines that the cells alluded to in Fig 4, A and B, stem from vascular endothelial cells. However, the mere presence of small turquoise dots does not justify such a far-reaching conclusion. The turquoise staining is much too diffuse, so that small dots occur not only within cells but also outside cells in the extracellular matrix, as one can see easily in the neointima in Fig 4, A. The idea of an endothelial stem cell origin of smooth muscle cells, moreover, is based mostly on in vitro studies of embryonic cells and, for the time being, remains largely hypothetical. Our study was not designed for this particular purpose and, therefore, does not provide scientific evidence to either support or deny the concept of transdifferentiation. However, our own previous studies,
1-3 as well as those of others, 4,5 have shown that proliferative activity resulting in neointimal formation follows a process of de-differentiation of smooth muscle cells, which makes it most unlikely that the response is due to proliferating endothelial stem cells.
12/8/113930doi:10.1067/mtc.2001.113930
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