 This new finding is titled Neural Progenitor Cells Regulates Microglia Functions and Activity. It was published in Nature Neuroscience Journal in November 2012 by Tony Wiss-Corey's lab at Sanford University. To understand this finding, let's talk about a few cell types that live in our brains and where they come from. So if I asked you what cells were in our brain, you would probably say neurons, and that's absolutely true. Neurons in our brain come from specialized cells that resemble stem cells that we call neural progenitor cells, or NPC. It was initially thought that neurons could not be replenished in case of injury, such as a stroke or brain trauma. But, thanks to research such as this one, we now know that these NPCs are very important for brain injury patients to regain cognition and fully recover. So remember these NPC cells, because this is what today's finding is focusing on. But our brains are composed of much more than just neurons. Our brains are also composed of a whole array of different cells that provide an environment in which the neurons can behave like neurons and produce a functioning brain. A microglia is one of these cells. Microglia are very important, and in fact crucial, for the proper functioning of the brain. This is in part because they produce molecules, or secreted molecules, that are going to travel to nearby NPCs and tell them what to do, such as divide and make neurons. So from what I've told you so far, you understand that microglia can influence the behavior of NPC cells. To be able to design better treatments for brain injury, it is important that we understand how NPCs work, because NPCs are the ones that replenish the neurons that are lost. What do they need to survive? And what do they provide to the cells around? So in an effort to understand how NPCs work, these scientists were interested in seeing if NPCs could influence the behavior of microglia. First, the scientists noticed that microglia were abundant near pools of NPCs. This provided a first clue that there could be an important interaction between these two cell types. Next, the scientists noticed that NPCs were also producing secreted molecules, and they wanted to see if these secreted molecules could influence microglia in a similar manner than microglia influence NPCs. To do this, the scientists isolated microglia alone and secreted molecules from NPCs and examined microglia function when the microglia were in the presence or absence of NPC secreted molecules. So what happened to the microglia? Well, the microglia that were given NPC secreted molecules started to divide, they moved around more, and they changed the types of secreted molecules they produced. So this was exciting and suggested that NPCs can influence microglia function through NPC secreted molecules. But the authors went even further and wanted to see if NPCs could control microglia function in a brain, with all of the added complexity, all of the other cell types, neurons, etc. So the authors injected NPCs into mouse brains and looked at the microglia. What the scientists saw was that at the site of the injection where there were many NPCs and NPC secreted molecules, there were a lot more microglia, a lot more activated microglia that were dividing and secreting their own secreted molecules. If the scientists injected NPC secreted molecules in mouse brains instead of NPCs themselves, they saw the same effect on microglia function. This means that the NPC secreted molecules are responsible for controlling the behavior of microglia, both in an isolated cell system, as well as in a brain. The scientists of this paper also discovered that one of the important NPC secreted molecules that is responsible for this is called VEGF, which controls the growth of blood vessels. It's not clear exactly how a factor that controls the growth of blood vessels could be responsible for controlling microglia function, but it's definitely a new avenue of research. So what did this study show? This study identified a new complex interaction between neural progenitor cells, or NPCs, and the microglia that surround them, where NPCs secret molecules that control microglia movement, number, and function. The scientists found that a factor that promotes the growth of blood vessels is responsible for this. This is very exciting because it suggests that NPCs are controlling microglia that in turn control NPC function. This type of cycle is found in many systems in nature, and it's very interesting to think about some possible reasons life would have evolved such complex modes of regulation. So what can we take away from this study when it comes to therapy? Of course, like every other study, there are a lot of questions that still remain. For instance, is this important for recovery from brain injury? How does this blood vessel growth factor control microglia function? And of course the ultimate question, can we use this information to influence recovery in patients? Can we somehow find a way to add more NPC secretive molecules, including VEGF, into patient brains to promote microglia function, in turn boosting NPC function, and possibly neuron growth? This idea is very exciting and provides new avenues for future research. So as you hopefully took away, scientists are always asking fundamental questions, offering breakthrough answers that in turn open up even more new exciting questions to expand our knowledge with the ultimate goal of developing efficient therapies.