Wednesday, August 28, 2013

Blood vessels cells go with the flow


Harvard scientists have grown the cells that line blood vessels, called vascular endothelial cells, from embryonic-like reprogrammed stem cells. (These are the stem cells generated from adult tissues like skin, also called induced pluripotent stem cells, or iPSCs).

This wouldn't be a big deal--after all the whole point of these cells is that they can form all the tissues of the body. What’s really interesting in this case is how they did it: part of coaxing the stem cells to turn into cells that line blood vessels relied on generating movement over the surface of the cells that mimicked blood flow. Basically, the cells needed to feel like they were at home.

The iPSCs responded by maturing into different kinds of cells based on the force of the movement. Cells that were exposed to a faster “flow” grew into cells that line arteries and those exposed to a slower “flow” grew into vein cells. It’s like deciding what kind of house you’re going to build based on the speed of traffic on your street.

The discovery has some immediate applications. In a press release, the lead scientist, Guillermo GarcĂ­a-Cardena, said his team is now using this information to grow cells like those in regions affected by diseases like artherosclerosis (plaque build-up in arteries that can eventually lead to heart disease). Those cells are being used to understand how blood vessels are affected by arterial plaques and also what kinds of drugs might address the problem.

This study, published July 25 in the scientific journal, Stem Cell Reports, has a lot in common with other recent stem cell discoveries – namely, that where you put stem cells makes a huge difference in how they mature. Location and the cellular environment matters a great deal. A good example of this was recent work at the University of Pittsburg, which my colleague Don Gibbons wrote about a couple of weeks ago, showing that human iPSCs grafted onto a mouse heart scaffold would mature into a beating heart.

Another facet of the Harvard finding is that the blood vessel cells can perform three important tasks: mount an inflammatory response, keep blood from leaking from vessels and preventing clots. So another likely application is reducing the amount of the blood clot prevention drug, heparin, required for kidney dialysis patients and in patients with lung failure. Garcia-Cardena foresees a future when a dialysis patient’s own cells are used to create iPSCs which are then coated onto a device that they can use to reduce possible blood clots, instead of the routine heparin shots they now receive.

Rina Shaikh-Lekso

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