Submitted December 13, 2007
Accepted August 28, 2008
The CD34-like protein PODXL and 
6-integrin (CD49f) identify early progenitor MSCs with increased clonogenicity and migration to infarcted heart in mice
Ryang Hwa Lee, Min Jeong Seo, Andrey A. Pulin, Carl A. Gregory, Joni Ylostalo, and Darwin J. Prockop*
Center for Gene Therapy, Tulane University Health Sciences Center, New Orleans, LA, United States
* Corresponding author; email: dprocko{at}tulane.edu.
We screened for surface proteins expressed only by the early progenitor cells present in low passage, low density cultures of the adult stem/progenitor cells from bone marrow referred to as mesenchymal stem cells or multipotent stromal cells (MSCs). Six proteins were identified that were selectively expressed in the early progenitors: podocalyxin-like protein (PODXL), 
6-integrin (CD49f), 4-integrin (CD49d), c-Met, CXCR4, and CX3CR1. All were previously shown to be involved in cell trafficking or tumor progression. Antibodies to CD49f and PODXL, a sialomucin in the CD34 family, were the most robust for FACScan assays. PODXLhi/CD49fhi MSCs were more clonogenic and differentiated more efficiently than PODXLlo/CD49flo cells. Inhibition of expression of PODXL with RNAi caused aggregation of the cells. Furthermore, PODXLhi/CD49fhi MSCs were less prone to produce lethal pulmonary emboli, and larger numbers were recovered in heart and kidney after intravenous infusion into mice with myocardial infarcts.
