As stated in the previous section about differentiation, many teams of scientists have experimented on the effects of certain factors on particular aspects of neurogenesis. We depend on all these little experiments to attempt to generate a clear picture of all the influences on neural development as well as possible ways to manipulate cell proliferation and differentiation. You've read in the differentiation section about the different "factors" that are used to make stem cells differentiate in vitro. Currently, there is not a lot of published research about the topic, because it's all so new. You have read the little summary of Vescovi and company's work in the differentiation page, and I can't really supply you with a whole lot more on the research that's being done specifically, but I just wanted you to know that right now, somewhere, someone IS doing work on figuring out how to culture the neuron that's just right for you! Here's some pictures that I thought you might enjoy. The one on the left is a picture of UNdifferentiated embryonic stem cells. The small, flat, elongated cells are fibroblasts that the stem cells grow on. The picture on the right shows differentiated neural precursors that were derived from stem cells. They are courtesy of Su-Chun Zhang of the Waisman Center in Madison, Wisconsin.

A study performed at the Harvard Medical School by Macklis, et al suggests that transplantation of exogenous cells may not even be required in cell replacement therapies. This potential medical miracle would be served best by an understanding of the mechanisms that contribute to cell growth and proliferation. Macklis and his team showed that "endogenous neural precursors can be induced in situ to differentiate into mature neurons, in regions of adult mammalian neocortex that do not normally undergo any neurogenesis." Brand spankin' new neurons were found to re-establish connections that were damaged by the research team in a region-specific manner. These results demonstrate that neural precursors already in our brains can be induced to differentiate into cortical neurons and form appropriate connections. Ongoing studies are investigating the molecular mechanisms underlying induced neurogenesis. Researchers are particularly interested in how this method can be modulated for different levels of damage, whether the new neurons differentiate precisely into the mature neuronal phenotype they are replacing, and whether newborn neurons join or form functional circuitry in the adult brain.

Now that we understand how neurons are grown in culture, we can start to think about transplanting them into brains!