In the controversial field of

In the controversial field of pluripotent stem cell research, it is vital to argue on the basis of reliable and solid data that best reflect the actual research situation and are carefully validated. However, available data on recent research activities in this field are often based on abstract searches and automatized algorithms, and not on manually verified data bank searches. For example, Pera and Trounson (2013) estimated the number of publications on hESC research to be nearly 2,000 per year for 2010 through 2012, since review articles were included in their data pool (Pera and Trounson, 2013). More strikingly, the recent European Union-funded Stem Cell Report, published in collaboration with Elsevier and Kyoto University (Barfoot et al., 2013), claimed that more than 500 papers on hESCs were published in 2008, and stated that in 2012, researchers from Germany published substantially more papers in the hESC field than groups from Japan, Korea, or Israel. However, a closer inspection of the data set used for this extensive and highly appreciated study revealed that, for example, the German hESC paper pool contained many publications in which hESCs were not used. Abstract statements such as “Despite their potential benefits, ethical and practical considerations limit the application of NSCs derived from hESCs or adult p38 inhibitor tissue. Thus, alternative sources are required” resulted in consideration of the respective paper as a contribution to hESC research. Altogether, nearly 50% of the alleged hESC papers from Germany used for this database did not report any research involving hESCs. Moreover, while our study was under review, Alberta et al. (2015) published an analysis assessing the impact of stem cell research funding programs in selected U.S. states. These authors searched the Web of Science for articles that contained the phrase “human embryonic stem cell” in the title, abstract, or key words, and were (co-)produced by authors with an affiliation in the United States. However, our analysis of this data pool (1,544 hESC-related papers from U.S. authors) revealed that more than 15% of the studies identified by Alberta et al. are not relevant because they did not report research involving hESCs. On the other hand, more than 550 relevant papers from the United States that involved hESCs and are present in our database were missed (including the one by Thomson et al. [1998]). The vast reduction of the initially high number of papers obtained through our selection process confirms that it may be essential for the assessment of research activities to initially generate broader publication-based data pools, and to manually validate each included paper. An analysis of papers only on the basis of meta-data provided by a search engine may result in a massive over- or underestimation of research output and may lead to misleading conclusions, which could potentially influence and misdirect political decision-making. When compared with our previous studies (Guhr et al., 2006; Löser et al., 2008, 2010, 2012), the current analysis revealed some relevant changes in the number and ranking of countries involved in hESC research. In addition, we substantiated that a country’s quantitative output of papers in hPSC research does not necessarily correlate with the impact of this research. For example, our previous surprising finding that Japan is somewhat underperforming in the hiPSC field was confirmed for recent years with respect to impact per study. Moreover, although the number of hPSC research papers from China increased markedly over the past years, research from China clearly underperformed with respect to impact per study in both the hESC and hiPSC fields. However, it may be expected that this situation will change in the near future as Chinese research groups increasingly publish papers in highly influential, ranking international journals.
Experimental Procedures