For short distances, cells can use chemical attractants to navigate, but recently, light has been shed on how they use the attractants in a different way to travel long distances:
The researchers theorized that certain cells navigate by breaking down chemoattractants that are close to them. They then sense the degree to which the chemoattractants are replenished, and most importantly, in which direction. By noting the position of the new chemoattractants, they are able to move toward their desired destination. As an example, a white blood cell working its way to a wound upon finding a fork in the road would choose the path with the most or newest chemoattractants after it breaks them down in both directions.
To test their theory, the researchers first created computer models to test its soundness. Doing so convinced them they were on the right track. Next, they etched a host of tiny mazes onto silicon chips, added chemoattractants and then dropped in soil amoebae that are known to navigate. They then watched as the amoebae broke down the chemoattractants they found in their path and then continued on their way in the direction in which new chemoattractants were filling in for the old. They found that the amoebae were very good at finding their way to destinations on relatively simple mazes, but were less skilled in those that were more complicated and had long dead ends. Still, nearly half of those tested managed to find their way through. The researchers suggest the accuracy declines as more time is taken to parse a maze. Those cells at the tail end of a group find all the chemoattractants have already been broken down by those ahead of them, and thus have nothing to use as a guide.Bob Yirka, “How cells can find their way through the human body” at Phys.org
The time lapse video of pancreatic cancer cells negotiating mazes is scary. Not at YouTube. You must go here to see it.
So much information, so little time.