Abstract
The potential applications of human embryonic and induced pluripotent stem cells has led to immense interest in developing new protocols to differentiate specific cell types or modifying existing protocols. To investigate to what extent and why new protocols for the same cell types are developed and adopted, we systematically evaluated 158 publications (2004-2017) that differentiated human stem cells into dopaminergic neurons. We categorized each article by degree of novelty and recorded motivations for protocol development. 74 novel or modified protocols were developed. Most (65%) were not used again in subsequent studies. Diverse motivations were recorded and performance of new methods was assessed with substantially different approaches across studies. There was improvement over time in yield of neuron production, but not in yield of dopaminergic neurons or time required for getting neurons. Standardized reporting of performance metrics may help rational choice of the best methods. Stem Cells Translational Medicine 2019;8:366-374.