In findings that offer the potential for new approaches to stem cell therapy, endothelial cells, the building blocks of the vascular system, have been found to keep blood stem cells dividing healthily in a lab dish much longer and more effectively than previous methods of growing the cells.
Stem cells
grown in the new system could be used for bone marrow transplants that
might allow lifetime repopulation of needed blood cells. The newly
developed research platform might also be useful for generating and
studying other types of adult stem cells since
previous research has shown that other organ-specific stem cells
typically reside near endothelial cells.
There are few naturally occurring stem cells in adult organs, so using them for organ regeneration is impractical. Adult stem cells can be grown in the laboratory, but until now, strategies to expand these cultures, which invariably used animal-based growth factors, serum, and genetically manipulated feeder cells, have not sustained the stem cells’ ability to self-renew for more than a few days.
In a new study, a team led by Shahin Rafii -- a Howard Hughes Medical Institute investigator at Weill Cornell Medical College in New York City -- employed endothelial cells to propagate stem cells in the laboratory without added growth factors or serum. In the body, these endothelial cells establish a “vascular niche” that is essential for regenerating blood stem cells in the adult bone marrow.
Rafii predicts that as researchers identify other factors with which endothelial cells influence stem cell behavior, this will establish a new arena in stem cell biology: “We will be able to selectively activate endothelial cells not only to induce organ regeneration, but also to inhibit the production of specific endothelial cell-derived factors in order to block tumor growth,” he says. “Our findings highlight the potential of vascular cells for generating sufficient stem cells for therapeutic organ regeneration, tumor targeting, and gene therapy applications.”