In 1998, University of Wisconsin's Dr. James Thomson published (see Technologies section) in Science his groundbreaking study on the ability to propagate human embryonic stem cells. Leukemia inhibitory factor (LIF) was one of the key reagents in the culture media that allowed the Wisconsin group to grow human embryonic stem cells over a mouse feeder layer. More recently, scientists at California Technology Institute, S. have found another application of LIF in which it is used to expand the stem cell niche in the body. Bauer and P. H. Patterson, published in the November 15th issue of Journal of Neuroscience their results on utilizing LIF in vivo to promotethe self-renewal of mouse adult neural stem cells. The investigators were able to expand the neural stem cell pool in the subventricular zone (SVZ) by injecting LIF into the brains of the adult mice. After LIF injection, the researchers found over a six-fold increase in the number of adult neural stem cells residing in the SVZ. When LIF is overexpressed in transgenic mice, the data suggest that LIF appears to reduce neurogenesis in the olfactory bulb and SVZ---two areas of the brain in which there is an active pool of neural stem cells. LIF appears to promote neural stem cell self-renewal by inhibiting neurogenesis and differentiation while ultimately expanding the stem cell pool. The authors conclude that LIF may have therapeutic value for brain repair and tissue regeneration when used in a combination with other growth factors.