Brief Report: Mechanism of Extravasation of Infused Stem Cells§



This article is corrected by:

  1. Errata: Erratum Volume 31, Issue 2, 415, Article first published online: 12 February 2013

  • Author contributions: K.C. and D.S.: conception and design, collection and/or assembly of data, data analysis and interpretation, and manuscript writing; Y.X., E.C., and K.M.: collection and/or assembly of data and data analysis and interpretation; E.M.: conception and design, financial support, manuscript writing, and final approval of manuscript. K.C. and D.S. contributed equally to this article.

  • Disclosure of potential conflicts of interest is found at the end of this article.

  • §

    First published online in STEM CELLS EXPRESS November 7, 2012.


In order for bloodborne stem cells to be effective in tissue regeneration, cells must cross vessel walls and enter the parenchyma. Although such transmigration does occur, the mechanism remains elusive. Leukocytes invade tissue by diapedesis; stem cells are commonly assumed to do likewise, but evidence is lacking. Cardiac-derived regenerative cells and multicellular cardiospheres (CSPs) were infused into the coronary vessels of rat hearts. Serial histology revealed a novel mechanism of cell transmigration, “active vascular expulsion,” which underlies the extravasation of infused cells and cell aggregates. In this mechanism, the vascular barrier undergoes extensive remodeling, while the cells themselves are relatively passive. The mechanism was confirmed in vivo by serial intravital microscopy of CSP extravasation in a dorsal skin flap model. Integrins and matrix metalloproteinases play critical roles in active vascular expulsion. In vitro models revealed that active vascular expulsion is generalizable to other stem cell types and to breast cancer cells. Recognition of active vascular expulsion as a mechanism for transvascular cell migration opens new opportunities to enhance the efficacy of vascularly delivered cell therapy. STEM CELLS 2012;30:2835–2842