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作者：Anke Guhra, Andreas Kurtza, Kelley Friedgenb, Peter Lsera ' ~$ h0 G# f G# y, h: w. m) X
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【摘要】1 v) O: H1 V9 U# J
Research in human embryonic stem cells (hESCs) is a rapidly developing scientific field. In this study we collect and evaluate a thorough body of data on the current number of publicly disclosed hESC lines and the extent and impact of scientific work involving the use of these cells. These data contribute to the substantiation of the discussion on the current status of hESC research, provide a basis for the analysis of the status of such research, and uncover further needs in terms of registration, banking, standardization, and tracing.
3 W8 f$ Q7 g( N7 Q1 O 【关键词】 Human embryonic stem cells Registry Published work Embryonic stem cell lines# q* d" c9 I% f5 n% K8 I
INTRODUCTION
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/ {+ M9 a* x& c% r; t6 @Since human embryonic stem cell (hESC) lines were first derived in 1998 . The present paper offers information that can provide needed substance to the debate on hESC research by presenting comprehensive data on the number of currently existing hESC lines and on the actual extent of experimental work undertaken with these cells and published as of December 2005 worldwide, based on the exploration of verifiable public sources.
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Figure 1A provides an overview of the number of hESC lines currently derived and in existence according to published data available from various sources. In total, information on 414 human ES cell lines was available. According to data published as of January 1, 2006, hESC lines have been established in at least 20 countries. Although the number of existing hESC lines is quite impressive, only limited data on characterization of these cell lines are publicly available. Currently it is not clear whether all lines are indeed pluripotent hESC lines. According to our database searches, derivation and at least partial characterization of only 43.2% (179, of which 171 are in English-language journals) of these cell lines have been published in peer-reviewed journals, and the use of an additional 6% (n = 25) has been published without detailed characterization data in peer-reviewed journals. Consequently, 49.2% of all cell lines have been published so far in scientific journals (Fig. 1B). Publication in a peer-reviewed journal provides some information about the hESC-like characteristics, but it does not provide absolute certainty on their quality. Especially in cases where multiple cell lines are described in a single study, characterization data are only shown for selected cell lines. Seventy-one different hESC lines are listed in the NIH Stem Cell Registry. Of these, only 22 are currently available to researchers. Of the remaining 49 hESC lines, only three have been characterized with respect to their stem cell nature and have been published in a peer-reviewed journal; two additional cell lines were published but have been withdrawn by the providers. Although the vast majority of hESC lines were derived using classic cultivation in the presence of feeder cells, 32 were derived under conditions free of animal cells and media containing animal-derived serum. However, it has to be taken into account that this is not equivalent to "animal-free" or "xerofree" conditions, as stated by some authors, since serum replacement used in some of these derivations may also contain animal-derived compounds. Twenty-seven hESC lines harbor defined genetic defects characteristic for distinct inheritable genetic disorders, and eight cell lines have been shown to have an abnormal karyotype. In addition to the 414 cell lines, 14 hESC lines have been clonally derived from existing hESC lines, some of which are listed in the NIH registry. Almost no information is publicly available on 106 of the 144 cell lines provided by the Reproductive Genetics Institute in Chicago and available from Stemride International Ltd. Remarkably, there were four times more new hESC lines published in peer-reviewed journals in 2005 (n = 88) than obtainable (available) from the NIH (n = 22). A detailed list of currently existing and publicly known hESC lines (including their respective references) is provided as supplemental online Data." K5 U1 r# M. a
# n2 M+ V. O" H8 D* r; EFigure 1. Derived hESC lines (as of January 1, 2006). Data were extracted from the NIH registry, from work published in scientific journals listed in the PubMed database, and from information either available online, presented at conferences, or provided in press releases. To date, only a portion of these cell lines have been published in scientific journals. No detailed information on the geographic origin of the 144 cell lines derived at the Reproductive Genetics Institute and distributed by STEMRIDE International Ltd. is publicly available from sources used in this study (marked as unknown). hESC lines derived at ES Cell International were assigned to Australia. Detailed information on the hESC lines is shown in supplemental online table. (A): Total number of cell lines sorted by country of origin. (B): Cell lines described or used in work published in peer-reviewed journals. Abbreviation: hESC, human embryonic stem cell., X9 w6 g6 {/ v
1 U- U- O! P- d! k7 P4 G2 eWe next wished to determine the number of scientific publications reporting on derivation and characterization of hESC lines or their experimental use. To cover all relevant papers on experimental use of hESCs, we performed searches of the PubMed database with no restriction to a publication category (such as "journal article") introduced into the search criteria. Although such restrictions do not reliably exclude papers without relevance for our study, this practice often results in the exclusion of relevant publications. Therefore, the broader search criteria reported in the online supporting material were applied. The searches resulted in more than 2,500 hits over the period spanning from January 1, 1998 to December 31, 2005. These hits were manually evaluated to exclude those articles in which hESCs were not used experimentally (e.g., reviews, tutorials, news, comments, work on mouse ES cells, etc.). Practical work using human embryonic carcinoma or embryonic germ cells but not hESCs was omitted, as was work in which hESC-derived materials (e.g., RNA or cDNA) but not hESCs were used. We found a total of 315 research papers describing derivation and/or experimental use of hESC lines that had been published (including online publication ahead of print) through December 31, 2005. Most of these research papers came from groups in the United States, followed by Israel, the U.K., and South Korea (Fig. 2). Interestingly, the number of scientific reviews and papers on ethical or legal aspects of hESC research by far exceeded the number of original publications describing experimental work conducted with these cells, suggesting that discussion about hESC research has outpaced actual research activities and continues to do so. According to the list of impact factors of 2004 (Institute for Scientific Information, Thomson Scientific, Philadelphia, http://www.thomson.com/scientific/scientific.jsp), the average impact factor for journals that have been publishing experimental work with hESCs was 6.03, indicating that an outstanding interest exists for this kind of research. Approximately 28% of published research focused on differentiation of hESCs into specialized cell or tissue types, with a noticeable emphasis on neural, heart, and blood cells. A comparable number of papers (approximately 27.5%) dealt with the molecular characterization of hESCs, including signal transduction, gene expression patterns, or early differentiation. Another 33% of papers described derivations of hESC lines or the establishment of improved culture conditions. In Table 1, the top 20 publications in the field (cited most frequently since the establishment of the first stem cell line in 1998) are listed. Table 2 gives an overview of the leading journals in the field of experimental hESC research with respect to the number of published research papers. The complete list of publications detected by our method is available as online supporting material. It is worth noting that according to information provided in the papers, at least 29% (n = 92) of all studies and 54% (n = 68) of the U.S. studies were conducted with at least partial financial support from the NIH.
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Figure 2. Overview of published work reporting on experimental use of hESCs. Searches of the PubMed database were performed as described in the supplemental online methods, and results were evaluated manually to exclude false-positive hits. (A): Number of papers extracted from the PubMed database by the described search string and the number of research papers reporting on derivation and/or experimental use of hESC lines. Data were sorted by publication year. Advance online publications available as of December 31, 2005, have been included. (B): Number of publications describing derivation and/or experimental use of hESC lines sorted by location of corresponding authors. Abbreviation: hESC, human embryonic stem cell.
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Table 1. Most frequently cited papers reporting on derivation of or experimental work with hESCs and published from 1998 to 2004
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, ^% d3 J7 [- W) I" HTable 2. Top journals with respect to publication of experimental work involving human embryonic stem cell (hESC) lines' C( W( b9 f& E& R& O8 k
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We have also determined the frequency at which specific hESC lines have been used in published research. Information on the hESC line used was available from 91.4% of studies. In total, 681 uses of hESC lines have been reported in these studies. Notably, 210 cell lines (50.7%) have never been described or used in published experimental work so far, and 150 cell lines (36.2%) were only described or used in a single scientific report. Of the remaining 54 hESC lines (13.1%), only 15 (3.6%) have been used in more than 10 studies published in the period investigated (Table 3). Among these, the cell line H9 and its clonally derived derivates were used most frequently in work (16.1% of all uses), followed by cell line H1 and its clonal derivate H1.1 (13.6%). Our data show that NIH-approved cell lines have been used in the majority of studies published through 2005. This might be due to the good knowledge of these cell lines, to the high proportion of research funding by NIH in the field, or to the fact that use of NIH-approved cell lines has been in accordance with regulation in other countries, such as Germany. A considerable portion of work published in 2005 (161 uses/derivations; 43.5% of all published hESC uses in 2005) reported on derivation of novel hESC lines or use of hESC lines not registered at the NIH (supplemental online Fig. 1). However, in most cases, the non-NIH-approved cell lines were used only in a single study (97 of 161 uses/derivations; 60.2% of reports on use/derivation of novel cell lines in 2005). This clearly suggests that an increasing number of researchers are establishing and using their own hESC lines. Although there is a need for new and easily accessible hESC lines derived under animal-free conditions, increased use of a multitude of hESC lines in research might diminish the comparability of results. Availability of few well-characterized and easily accessible hESC lines derived under animal-free conditions and provided by specialized institutions, such as stem cell banks, might be an alternative for research.6 ?/ A! U- q# d* j0 [
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Table 3. Most frequently used human embryonic stem cell (hESC) lines
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While this paper was under review, Owen-Smith and McCormick . Because there is an ongoing globalization of hESC research, we considered the localization of the corresponding author's laboratory as more appropriate for assigning a study on hESCs to a country.
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In summary, we provide data on the current state of experimental research involving human embryonic stem cells. Although the completeness of this review is contingent upon the limitations of the search methodology, incomplete information in some published articles, and the lack of accepted registry and tracing mechanisms for hESC lines, we provide evidence that hESC research is a field that has been developing rapidly, especially within the last 3 years. Although the number of published hESC lines has markedly increased within the last 3 years, most published research has been performed with cell lines derived before the end of 2001. However, the growing number of a variety of well-characterized new hESC lines partially harboring defined genetic defects or more suitable for future clinical applications all but guarantees that an increasing number of hESC research laboratories will begin using these lines in the near future.
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' ^' m% J2 {7 E0 e9 qDISCLOSURES
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The authors indicate no potential conflicts of interest.
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3 l) H# d/ J3 G7 g2 M DACKNOWLEDGMENTS
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: x9 j! W3 S+ t8 F7 {A.G. and A.K. contributed equally to this work.* d5 x% l" _4 z- ?8 }
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发表于 2009-3-5 00:01
发表于 2010-3-30 17:32
