The Stem Cell Research Environment: A Patchwork of Patchworks

Few areas of recent research have received as much focus or generated as much excitement and debate as stem cell research. Hope for the therapeutic promise of this field has been matched by social concern associated largely with the sources of stem cells and their uses. This interplay between promise and controversy has contributed to the enormous variation that exists among the environments in which stem cell research is conducted throughout the world. This variation is layered upon intra-jurisdictional policies that are also often complex and in flux, resulting in what we term a ‘patchwork of patchworks’. This patchwork of patchworks and its implications will become increasingly important as we enter this new era of stem cell research. The current progression towards translational and clinical research among international collaborators serves as a catalyst for identifying potential policy conflict and makes it imperative to address jurisdictional variability in stem cell research environments. The existing patchworks seen in contemporary stem cell research environments provide a valuable opportunity to consider how variations in regulations and policies across and within jurisdictions influence research efficiencies and directions. In one sense, the stem cell research context can be viewed as a living experiment occurring across the globe. The lessons to be gleaned from examining this field have great potential for broad-ranging general science policy application.

Product Regulation and the Clinical Translation of Stem Cell Research

The recent approval by the United States Food and Drug Administration of a clinical trial involving a product derived from human embryonic stem cells, along with recent concerns about unproven stem cell therapies being offered to patients, highlight the importance of regulation at the critical stage of beginning human trials of novel therapies. The regulations governing therapeutic products (drugs and related products) are one part of the broader legal framework, but will play an increasingly prominent role as we move into clinical translation. The classification of products as drugs or biologics, on one hand, or minimally manipulated cell and tissue products for homologous use, on the other, will determine the requirements that will apply, including whether use in clinical trials requires approval. Product regulation works alongside other parts of the legal and policy framework, notably research ethics review and legal responsibilities of medical professionals, that play important though limited roles. Three key developments and challenges currently facing product regulation and related areas will affect stem cell research in this phase: regulatory reform, fragmentation, and capacity.     

脂肪来源干细胞的研究及临床应用前景

目的：总结脂肪干细胞的研究进展及在临床上的应用。方法：查阅国内外相关文献,对脂肪干细胞的分化能力及临床应用前景进行汇总分析。结果：脂肪干细胞具有多向分化潜能,在动物模型中进行组织修复、细胞移植等方面有成功报道。结论：作为种子细胞的脂肪干细胞有着广阔的临床应用前景,其研究有待进一步深入。     

干细胞研究的意义和存在的问题

本文以干细胞的定义、造血和神经干细胞的研究和应用为基础，就干细胞研究的意义和存在的问题进行评述。重点就干细胞的扩增和鉴定、干细胞的可塑性和多能干细胞、干细胞在组织修复和个体发育中的意义进行讨论。介绍当前研究动向，从分子生物学水平充分认识干细胞的本质，认识主导干细胞繁殖、定向和跨系分化的内在机制，以更有效地发挥干细胞的潜能，更好地为临床实践服务。     

Genetic Control of Intestinal Stem Cell Specification and Development: A Comparative View

Stem cells of the adult vertebrate intestine (ISCs) are responsible for the continuous replacement of intestinal cells, but also serve as site of origin of intestinal neoplasms. The interaction between multiple signaling pathways, including Wnt/Wg, Shh/Hh, BMP, and Notch, orchestrate mitosis, motility, and differentiation of ISCs. Many fundamental questions of how these pathways carry out their function remain unanswered. One approach to gain more insight is to look at the development of stem cells, to analyze the "programming" process which these cells undergo as they emerge from the large populations of embryonic progenitors. This review intends to summarize pertinent data on vertebrate intestinal stem cell biology, to then take a closer look at recent studies of intestinal stem cell development in Drosophila. Here, stem cell pools and their niche environment consist of relatively small numbers of cells, and questions concerning the pattern of cell division, niche-stem cell contacts, or differentiation can be addressed at the single cell level. Likewise, it is possible to analyze the emergence of stem cells during development more easily than in vertebrate systems: where in the embryo do stem cells arise, what structures in their environment do they interact with, and what signaling pathways are active sequentially as a result of these interactions. Given the high degree of conservation among genetic mechanisms controlling stem cell behavior in all animals, findings in Drosophila will provide answers that inform research in the vertebrate stem cell field.     

Artificial Cell Therapy: New Strategies for the Therapeutic Delivery of Live Bacteria

There has been rapid growth in research regarding theuse of live bacterial cells for therapeutic purposes.The recognition that these cells can be geneticallyengineered to synthesize products that havetherapeutic potential has generated considerableinterest and excitement among clinicians and healthprofessionals. It is expected that a wide range ofdisease modifying substrates such as enzymes,hormones, antibodies, vaccines, and other geneticproducts will be used successfully and will impactupon health care substantially. However, a majorlimitation in the use of these bacterial cells is thecomplexity of delivering them to the correct targettissues. Oral delivery of live cells, lyophilizedcells, and immobilized cells has been attempted butwith limited success. Primarily, this is becausebacterial cells are incapable of surviving passagethrough the gastrointestinal tract. In manyoccasions, when given orally, these cells have beenfound to provoke immunogenic responses that areundesirable. Recent studies show that these problemscan be overcome by delivering live bacterial cells,such as genetically engineered cells, usingartificial cell microcapsules. This review summarizesrecent advances in the therapeutic use of livebacterial cells for therapy, discusses the principlesof using artificial cells for the oral delivery ofbacterial cells, outlines methods for preparingsuitable artificial cells for this purpose, addressespotentials and limitations for their application intherapy, and provides insight for the futuredirection of this emergent and highly prospectivetechnology.     

布氏显微镜活血分析: 细胞流变学研究的新方法

布氏显微镜活血分析：细胞流变学研究的新方法骆秉铨＊黄荣国＊陈兴新＊细胞流变学是研究血细胞流动变形的科学，在方法学上发展了一些比较成熟的方法，但多不能直接动态观察细胞水平的真实改变，有待完善和创新。我们采用布氏多功能显微镜的活血分析法［１］，在高放大倍...     

Clinical Endpoints in Allogeneic Hematopoietic Stem Cell Transplantation Studies: The Cost of Freedom

When designing a study for allogeneic hematopoietic stem cell transplantation (HSCT), many choices must be made, including conditioning regimen, stem cell source, and graft-versus-host disease (GVHD) prevention method. For each of these, there are a growing number of options, which can be combined into a bewildering number of possible HSCT protocols. To properly interpret the results of a given strategy and compare them with others, it is essential that there be agreement on the definitions and estimation methods of HSCT endpoints. We report a survey of the recent HSCT literature that confirms the heterogeneity of endpoint definitions and estimation methods used. Unfortunately, this heterogeneity may lead to significant biases in the estimates of key endpoints, including nonrelapse mortality, relapse, GVHD, or engraftment. This can preclude adequate comparisons among studies, even though such comparisons are the major tool with which to improve HSCT outcome. In the context of our survey, we discuss some of the statistical issues that arise when dealing with HSCT endpoints and the ramifications of the choice of endpoint definition, when the endpoint occurs in the context of competing risks. Our hope is to generate discussion and motivate a search for consensus among those who perform transplantations and statisticians.     

The Evolution of Policy Issues in Stem Cell Research: An International Survey

Stem cell research remains a tremendously promising yet controversial field of study. It continues to attract considerable public interest and generate discussion and debate. However, while the high profile of this field has endured, the tone and nature of the discourse that drives this profile appears to be changing. In order to get a better sense of how these potential shifts are perceived by individuals directly embedded in the field, we conducted an international internet survey of members of the stem cell research community. Our participants included individuals publishing on both scientific and ethical, legal and social issues topics. We explored the degree to which participants perceived that key policy issues were becoming more or less contentious over time. We queried views regarding the effect of regulatory frameworks on emerging stem cell research technologies and the extent to which participants experience pressure related to clinical translation. We also explored participants?? relationships with industry, experience with patents and perceptions regarding the emphasis placed on the potential economic benefits of stem cell research. Our results suggest that while traditional debates such as those surrounding the moral status of the embryo remain, other issues more closely associated with clinical translation and commercialization are perceived as becoming increasingly contentious. This survey provides useful insight into the perspectives of a sample of active researchers working in countries around the world as well as an opportunity to reflect on the likely direction of future stem cell policy debates.     

The International Society for Stem Cell Research (ISSCR): history and perspectives

The International Society for Stem Cell Research (ISSCR) is an independent, nonprofit organization founded in 2002 to foster professional and public communication and education regarding stem cell research. Under the leadership of prominent stem cell scientists from around the world, the ISSCR membership has grown exponentially, creating a diverse, international community of researchers who have expertise in many facets of stem cell biology. The ISSCR is dedicated to promoting the exchange of ideas and has developed two major forums for dissemination of stem cell research and related issues, an annual meeting and an information-rich website. With the field of stem cell research and technologies rapidly advancing, discourse is more critical than ever to maintain high standards across the full spectrum of research.     

The Promise of Stem Cell Research in Pigs and Other Ungulate Species

Despite two decades of effort, establishment of pluripotent embryonic stem cells (ESC) from ungulates such as cattle and pigs has remained an elusive goal, with true ESC only successfully isolated from rodents and primates. The many reports describing ESC-like cultures from other “difficult” species has largely depended upon adopting strategies successful for mouse and human and have not yet produced a cell type that both proliferated continuously in culture without differentiation and demonstrated full pluripotent potential. These difficulties may have been exacerbated in ungulates by the lack of specific markers exclusive to inner cell mass (ICM) and its derivative the epiblast and by unique features of their preimplantation development. Especially important may have been the choice of culture condition, including growth factors, for establishing and sustaining the ESC. Recent modifications to culture medium, notably the inclusion of particular protein kinase inhibitors, have permitted ESC derivation from rat and previously “non-permissive” mouse strains. These conditions appear to stabilize the biochemical networks that sustain pluripotency and to render the cells dependent upon LIF signaling. In addition, the recent successful generation of induced pluripotent stem cells (iPSC) from pig by procedures that should be easily adapted to other species, is also likely to advance the area quickly. The pig is a particularly desirable species to create pluripotent cell lines because of its value as a biomedical model in transplantation at a time when there is mounting pressure to rush stem cells to the clinic before their safety has been adequately tested in animals.     

The Use of Discontinuous Density Gradients in Stem Cell Research and Application

Discontinuous density gradients have been shown to be very efficient in sperm enrichment in assisted reproductive technologies (ART). Percoll [polyvinylpyrrolidone (PVP)-coated silica] which is a colloidal agent commonly used in such gradients is now confined to only research purposes in ART because its PVP component was considered toxic for clinical applications. The PVP component was replaced with silane instead and silane-coated colloidal silica marketed as Puresperm is currently being used for clinical sperm enhancement procedures in ART. The efficiency of these two agents has not been tested for human embryonic stem cell (hESC) and cancer cell research and clinical application. Herein we describe discontinuous density gradient protocols using PureSperm and Percoll for the separation and enrichment of hESCs and hepatocarcinoma cells from a mixed cell population. Trypan blue cell viability and CellTracker green cell counts are used to accurately quantify the extent of cell separation. We show that Puresperm provides good cell separation and enrichment with higher viable cell counts and greater number of fractions compared to Percoll. PureSperm being superior and safer compared to Percoll would be a better alternative for cell separation and enrichment in stem and cancer cell research and clinical applications.     

Participation in Clinical Research: Perspectives of Adult Patients and Parents of Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation

Despite major improvements over the past several decades, many patients undergoing hematopoietic stem cell transplantations (HSCT) continue to suffer from significant treatment-related morbidity and mortality. Clinical research studies (trials) have been integral to advancing the standard of care in HSCT. However, 1 of the biggest challenges with clinical trials is the low participation rate. Although barriers to participation in cancer clinical trials have been previously explored, studies specific to HSCT are lacking. The current study was undertaken to examine the knowledge, attitudes, and perceptions of HSCT patients regarding clinical trials. As members of focus groups, participants responded to open-ended questions that assessed factors influencing decision-making about HSCT clinical trials. Suggestions for improvements in the recruitment process were also solicited among participants. Seventeen adult HSCT patients and 6 parents of pediatric HSCT patients participated in the study. The median age was 56 years (range, 18 to 70) and 44 years (range, 28 to 54) for adult patients and parents, respectively. Participants universally indicated that too much information was provided within the informed consents and they were intimidated by the medical and legal language. Despite the large amount of information provided to them at the time of study enrollment, the participants had limited knowledge retention and recall of study details. Nevertheless, participants reported overall positive experiences with clinical trial participation and many would readily choose to participate again. A common concern among participants was the uncertainty of study outcome and general lack of feedback about results at the end of the study. Participants suggested that investigators provide more condensed and easier to understand informed consents and follow-up of study findings. These findings could be used to help guide the development of improved consent documents and enhanced participation in research studies, thereby affecting the future design of HSCT research protocols.     

Cell Mimicking Microparticles Influence the Organization,Growth, and Mechanophenotype of Stem Cell Spheroids

Substrate stiffness is known to alter cell behavior and drive stem cell differentiation, though most research in this area has been restricted to traditional, two-dimensional culture systems rather than more physiologically relevant, three-dimensional (3D) platforms. In this study, we utilized polymer-based, cell mimicking microparticles (CMMPs) to deliver distinct, stable mechanical cues to human adipose derived stem cells in 3D spheroid culture to examine changes in adipogenic differentiation response and mechanophenotype. After 21 days of adipogenic induction, spheroids containing CMMPs (composite spheroids) stiffened in accordance with CMMP elasticity such that spheroids containing the stiffest, ~?10 kPa, CMMPs were over 27% stiffer than those incorporating the most compliant, ~?0.25 kPa CMMPs. Adipogenically induced, cell-only spheroids were over 180% larger and 50% more compliant than matched controls. Interestingly, composite spheroids cultured without chemical induction factors dissociated when presented with CMMPs stiffer than ~?1 kPa, while adipogenic induction factors mitigated this behavior. Gene expression for PPARG and FABP4 were upregulated more than 45-fold in adipogenically induced samples compared to controls but were unaffected by CMMP elasticity, attributed to insufficient cell-CMMP contacts throughout the composite spheroid. In summary, mechanically tuned CMMPs influenced whole-spheroid mechanophenotype and stability but minimally affected differentiation response.