As noted at EureAlert!, scientists are making progress in the quality of their technology demonstrations: "Although [domamine or DA] cell-replacement therapy by transplantation of human fetal mesencephalic tissue has shown promise in clinical trials, limited tissue availability means that other sources of these cells are needed. ... [researchers] have identified a new source for DA cells that provided marked benefit when transplanted into mice with a [Parkinson's or PD]-like disease. ... DA cells were derived from ventral midbrain (VM) neural stem cells/progenitors by culturing them in the presence of a number of factors - FGF2, sonic hedgehog, and FGF8 - and engineering them to express Wnt5a. This protocol generated 10-fold more DA cells than did conventional FGF2 treatment. Further analysis revealed that these cells initiated substantial cellular and functional recovery when transplanted into mice with PD-like disease. Importantly, the mice did not develop tumors, a potential risk that has precluded the clinical development of embryonic stem cells as a source of DA cells." Tissue engineering is a fearsomely complex business, but great improvement in quality and cost is inevitable.