Concise review: adipose-derived stromal cells for skeletal regenerative medicine

As the average age of the population grows, the incidence of osteoporosis and skeletal diseases continues to rise. Current treatment options for skeletal repair include immobilization, rigid fixation, alloplastic materials, and bone grafts, all which have significant limitations, especially in the elderly. Adipose-derived stromal cells (ASCs) represent a readily available abundant supply of mesenchymal stem cells, which demonstrate the ability to undergo osteogenesis in vitro and in vivo, making ASCs a promising source of skeletal progenitor cells. Current protocols allow for the harvest of over one million cells from only 15 ml of lipoaspirate. Despite the clinical use of ASCs to treat systemic inflammatory diseases, no large human clinical trials exist using ASCs for skeletal tissue engineering. The aim of this review is to define ASCs, to describe the isolation procedure of ASCs, to review the basic biology of their osteogenic differentiation, discuss cell types and scaffolds available for bone tissue engineering, and finally, to explore imaging of ASCs and their potential future role in human skeletal tissue engineering efforts.     

Concise review: Adipose-derived stromal vascular fraction cells and stem cells: let's not get lost in translation

Subcutaneous fat has emerged as an alternative tissue source for stromal/stem cells in regenerative medicine. Over the past decade, international research efforts have established a wealth of basic science and preclinical evidence regarding the differentiation potential and regenerative properties of both freshly processed, heterogeneous stromal vascular fraction cells and culture expanded, relatively homogeneous adipose-derived stromal/stem cells. The stage has been set for clinicians to translate adipose-derived cells from the bench to the bedside; however, this process will involve "development" steps that fall outside of traditional "hypothesis-driven, mechanism-based" paradigm. This concise review examines the next stages of the development process for therapeutic applications of adipose-derived cells and highlights the current state of the art regarding clinical trials. It is recommended that the experiments addressing these issues be reported comprehensively in the peer-review literature. This transparency will accelerate the standardization and reproducibility of adipose-derived cell therapies with respect to their efficacy and safety.     

DNA methylation analysis as novel tool for quality control in regenerative medicine

Cell-based regenerative medicine, including tissue engineering, is a novel approach to reconstituting tissues that do not spontaneously heal, such as damaged cartilage, and to curing diseases caused by malfunctioning cells. Typically, manufacturing processes to generate cartilage for replacement therapies involve isolation and expansion of cells from cartilage biopsies. A challenge in the field is potential contamination by other cell types (e.g., fibroblast-like cells), which can overgrow the desired cells during culturing and may ultimately compromise clinical efficacy. No standard analytical system has been absolutely effective in ensuring the identity of these cell-based products. Therefore, we tested deoxyribonucleic acid methylation analysis as a quality assessment tool, applying it to Genzyme's Carticel product, a chondrocyte implant that the Food and Drug Administration has approved. We identified 7 potent discriminators by assaying candidate genomic regions derived from methylation discovery approaches and literature searches regarding a functional role of genes in chondrocyte biology. Using a support vector machine, we trained an optimal cell type classifier that was absolutely effective in discriminating chondrocytes from synovial membrane derived cells, the major potential contaminant of chondrocyte cultures. The abundant marker availability and high quality of this assay format also suggest it as a potential quality control test for other cell types grown or manipulated in vitro.     

Concise review: embryonic stem cells: a new tool to study osteoblast and osteoclast differentiation

Bone remodeling involves synthesis of organic matrix by osteoblasts and bone resorption by osteoclasts. A tight collaboration between these two cell types is essential to maintain a physiological bone homeostasis. Thus, osteoblasts control bone-resorbing activities and are also involved in osteoclast differentiation. Any disturbance between these effectors leads to the development of skeletal abnormalities and/or bone diseases. In this context, the determination of key genes involved in bone cell differentiation is a new challenge to treat any skeletal disorders. Different models are used to study the differentiation process of these cells, but all of them use pre-engaged progenitor cells, allowing us to study only the latest stages of the differentiation. Embryonic stem (ES) cells come from the inner mass of the blastocyst prior its implantation to the uterine wall. Because of their capacity to differentiate into all germ layers, and so into all tissues of the body, ES cells represent the best model by which to study earliest stages of bone cell differentiation. Osteoblasts are generated by two methods, one including the generation of embryoid body, the other not. Mineralizing cells are obtained after 2 weeks of culture and express all the specific osteoblastic markers (alkaline phosphatase, type I collagen, osteocalcin, and others). Osteoclasts are generated from a single-cell suspension of ES cells seeded on a feeder monolayer, and bone-resorbing cells expressing osteoclastic markers such as tartrate-resistant alkaline phosphatase or receptor activator of nuclear factor kappaB are obtained within 11 days. The aim of this review is to present recent discoveries and advances in the differentiation of both osteoblasts and osteoclasts from ES cells.     

Large-scale production of human adipose tissue from stem cells: a new tool for regenerative medicine and tissue banking

Adipose tissue is an easy, accessible, and abundant source of mesenchymal stem cells (MSCs) for the reconstruction and addition of soft tissue and for restoration of soft-tissue defects associated with trauma, tumor resections, and congenital deformities. A stable source of adipose cells or tissue is needed for autologous grafting. Therefore, the aim of this study was to obtain enough autologous adipose tissue for possible clinical applications. For this purpose, we isolated MSCs (CD34+/CD90+) from human lipoaspirated or resected fat, which differentiated into adipocytes when placed in culture. Human adipose tissue is a paramount source of autologous MSCs were capable of generating a complete adipose tissue in vitro. Differentiated adipocytes expressed a strong positivity for several specific antibodies, including adiponectin and peroxisome proliferator-activated receptor gamma. In addition, fibroblasts (approximately 10% of the whole sorted-cell population) started to secrete an extracellular matrix after 60 days that was strongly positive for type I collagen and fibronectin. After long-term culture (4 months), an adipose tissue with collagenic fibers and vessels was obtained. This tissue was comparable with adult human adipose tissue and therefore may be a criterion standard for future tissue repair and regeneration and for therapeutic and transplantation purposes.     

Concise review: Circulating endothelial progenitor cells for vascular medicine

Endothelial progenitor cells (EPCs) have been isolated and shown to be effective in animal models of ischemia, and many groups involved in clinical trials have demonstrated that EPC therapy is safe and feasible for the treatment of critical limb ischemia and cardiovascular diseases. However, many issues in the field of EPC biology, especially in regards to the proper and unambiguous molecular characterization of these cells still remain unresolved, hampering not only basic research but also the effective therapeutic use and widespread application of these cells. In this review, we introduce the recent concept of EPC identification in terms of hematopoietic and nonhematopoietic EPCs along with the development of EPC biology research. Furthermore, we define the role of circulating EPCs in postnatal neovascularization to illustrate the future direction of EPC therapeutic applications. Next, we review on-going medical applications of EPC for cardiovascular and peripheral vascular diseases, introduce the practical example of therapeutic application of EPCs to patients with ischemic disease, and discuss about the feedback of clinical researches.     

Concise review: stem cells as an emerging platform for antibody therapy of cancer

Monoclonal antibodies are important tools for cancer therapy, however, three factors limit their effectiveness: toxicity, poor tumor penetration, and inability to cross the blood-brain barrier. This review discusses the emerging field of stem cell-mediated antibody delivery and how this approach may improve antibody therapy of cancer by overcoming these obstacles.     

Concise review: stem cells for the treatment of cerebellar-related disorders

Embryonic neural transplants have become clinically relevant over the past 25 years for their possible application in the treatment of cerebellum-related neurodegenerative diseases. While highlighting the important role that fetal neural progenitors have in meeting these challenges, we define rationales for all types of cell therapy involving adult stem cells as well as human embryonic stem cells (hESC) and human induced pluripotent stem (iPS) cells. The recent advances in the field of hESC and iPS cells, including their capacity for differentiation toward regional specific neural lineages, could open a new era of transplantation in cell-based therapy for cerebellar ataxias.     

Concise review: Vascular stem cells and tumor angiogenesis

Solid tumors are complex "organs" of cancer cells and a heterogeneous population of hematopoietic cells, mesenchymal cells, and endothelial cells. The cancer stem cell model proposes that tumor growth and progression is driven by rare populations of cancer stem cells; however, nontumor-forming stem and progenitor cells are also present within the tumor microenvironment. These adult stem cells do not form tumors when injected into experimental animals, but they may augment tumor growth through juxtacrine and paracrine regulation of tumor cells and by contributing to neovascularization. Thus, cancer cells may actively co-opt nontumor-forming stem cells distally from the bone marrow or proximally from nearby tissue and subvert their abilities to differentiate and maintain tissue growth, repair, and angiogenesis. This review will cover the roles of nontumor-forming vascular stem cells in tumor growth and angiogenesis.     

Concise review: Epidermal grafting: the case for pluripotent stem cells

Although cell therapy has been clinically implemented for several decades, its use is hampered by the difficulty in supplying the amount of epidermal substitute needed to extend the application to all patients who may benefit from it. How human pluripotent stem cells may help meet this challenge is the topic of this review. After reporting on the main current applications and needs of skin grafting, we explore the potential of pluripotent stem cells--either of embryonic origin or produced by genetic reprogramming--to provide the needed clinical-grade keratinocytes, fulfilling industrial scale production, and quality standards. Immunogenicity is clearly an issue, although one may expect cells displaying characteristics of fetal or embryonic skin to have a much better tolerance than adult keratinocytes. The open possibility of a bank of pluripotent stem cell lines selected on the basis of interesting haplotypes may eventually provide a definitive answer. Actually, making the case for pluripotent stem cells in skin grafting goes well beyond that specific cell type. Most cell phenotypes that normally participate to the formation of dermis and epidermis can either already be obtained through in vitro differentiation from pluripotent stem cells or would likely migrate from the host into a graft. However, differentiation protocols for specialized glands and hair follicles remain to be designed. A future can be foreseen when reconstructive medicine will make use of composite grafts integrating several different cell types and biomaterials.     

Concise review: Cancer stem cells and minimal residual disease

Evidence gathered over the past two decades confirms earlier reports that suggested that hematologic malignancies exhibit a hierarchical differentiation structure similar to normal hematopoiesis. There is growing evidence that some solid tumors may also exhibit a differentiation program similar to the normal tissue of origin. Many excellent reviews on the topic of cancer stem cells (CSCs) document the recent explosion of information in the field, particularly highlighting the phenotypic and functional characteristics of these putative cells in vitro. Accordingly, here we only briefly discuss these concepts, and instead primarily examine the potential clinical relevance of CSCs, arguably the major unresolved issue in the field. Although it is generally accepted that CSCs are resistant to chemotherapy in vitro, only recently have data surfaced that suggest a role for these cells in disease relapse. Importantly, cancer cells with a stem cell phenotype have been found to be enriched in minimal residual disease of several malignancies. If the role of CSCs in relapse is confirmed, targeting these cells would hold substantial potential for improving the outcome of cancer patients.     

Concise review: Immune recognition of induced pluripotent stem cells

Autologous-induced pluripotent stem cells (iPSCs) may eventually be used in cell replacement therapies to treat a wide range of diseases and have been touted as a solution to the vexing problem of immune rejection in this context. Emerging evidence suggests, however, that ostensibly histocompatible iPSCs may be rejected following transplantation. Here, we review the mechanisms that contribute to immunogenicity in iPSCs and forward approaches to permit their acceptance in potential cell replacement therapies.     

Concise review: mesenchymal tumors: when stem cells go mad

Sarcomas are nonepithelial, nonhematopoietic malignant tumors that arise from the embryonic mesoderm. Despite their rarity, less than 10% of all cancers, sarcomas are accountable for relatively high morbidity and mortality especially in children and adolescents. Although there are some hereditary conditions predisposing sarcoma, such as the Li-Fraumeni and Retinoblastoma syndrome, the vast majority of these tumors are sporadic. Based on their histological morphology, sarcomas have been divided into a broad spectrum of subtypes recognized in the 2002 WHO classification of tumors. This wide lineage range suggests that sarcomas originate from either many committed different cell types or from a multipotent cell, subsequently driven into a certain lineage. Mesenchymal stem cells (MSCs) are able to differentiate into many cell types needed to create mature structures like vessels, muscle, and bone. These multipotent cells can be isolated from several adult human tissues and massively expanded in culture, making them both of use for research as well as potential beneficial therapeutical agents. For this reason MSCs are being extensively studied, however, concerns have raised about whether they are the putative originating cells of sarcoma and their questionable role in cancer progression. Recent accomplishments in the field have broadened our knowledge of MSCs in relation to sarcoma origin, sarcoma treatment and the safety of MSCs usage in therapeutic settings.     

Concise review: hematopoietic stem cells and tissue stem cells: current concepts and unanswered questions

The term hematopoietic stem cells has at times been used to include a miscellany of precursor cells ranging from multipotential self-generating cells to lineage-restricted progenitors with little capacity for self-generation. It is probable that the stem cells of other tissues also vary widely in their multipotentiality and proliferative capacity. This review questions several dogmas regarding the self-generative capacity of various hematopoietic cells, the single episodic origin of hematopoietic cells, and the irreversible nature of progressive mature cell formation in individual hematopoietic lineages. Disclosure of potential conflicts of interest is found at the end of this article.     

Concise review: Embryonic stem cells versus induced pluripotent stem cells: the game is on

Extraordinary advances in pluripotent stem cell research have initiated an era of hope for regenerative strategies to treat human disease. Besides embryonic stem cells, the discovery of induced pluripotent stem cells widened the possibility of patient-specific cell therapy, drug discovery, and disease modeling. Although similar, it has become clear that these two pluripotent cell types display significant differences. In this review, we explore current knowledge of the molecular and functional similarities and differences between these two cell types to emphasize the necessity for thorough characterization of their properties as well as their differentiation capabilities in the pluripotent state. Such comparative studies will be crucial for determining the more suitable cell type for future stem cell-based therapies for human degenerative diseases.     

牙髓干细胞在再生医学中的应用研究与进展

BACKGROUND:Dental pulp stem cells are characterized by multi-lineage differentiation and proliferation abilities and are easy to obtain, so they are becoming an issue of concern in regenerative medicine. OBJECTIVE:To provide clues and direction for further study by analyzing progress of domestic and overseas research on dental pulp stem cells, and summarizing their application in regenerative medicine. METHODS:The “dental pulp stem cell, regenerative medicine, tissue engineering” in Chinese and English served as the search terms to search articles related to dental pulp stem cells and regenerative medicine, published from 2000 to 2015 in Medline, PubMed, CNKI, Wanfang and Cqvip databases. Totally 46 articles were selected for overview.  RESULTS AND CONCLUSION:Dental pulp stem cells, which hold the capacity of self-renewal and multi-lineage differentiation, are relatively easy to obtain, and exhibit a great potential in regenerative medicine. The research of dental pulp stem cells in repairing bone defects has entered the clinical trial phase, but the research of cell differentiation into other tissues is still in basic trial phase and needs further development.     

诱导多潜能干细胞在再生医学中的应用

背景：传统的器官或者细胞移植存在严重的供体来源不足和免疫排斥问题以及伦理学障碍。诱导多潜能干细胞有着近乎胚胎干细胞的自我更新能力和分化潜能,而且还拥有与患者一致的遗传物质,避免了免疫排斥反应,其应用前景十分广阔。 目的：综述诱导多潜能干细胞在再生医学领域应用研究的现状。 方法：应用计算机检索PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed)相关文章,检索时间为1997/2010,检索词为“induced pluripotent stem cell,diabetes,Parkinson’s disease,cardiovascular”,并限定文章语言种类为English。初检得到文献322篇,最终入选30篇文章进行综述。 结果与结论：疾病特异的诱导多潜能干细胞来源于患者本身,拥有与患者一致的遗传物质,既降低了移植后的免疫排斥,也避免了伦理学的问题。因此个体特异的诱导多潜能干细胞在再生医学领域有潜在的应用前景。     

间充质干细胞来源外泌体与再生医学：无细胞疗法临床应用的未来

文题释义：外泌体：是一种区别于微泡,具有特异脂质、蛋白、信使RNA和微小非编码RNA的微小膜性囊泡结构,其大小均一,直径为40-100 nm,密度为1.10-1.18 g/mL,可通过细胞内吞泡膜向内凹陷形成多泡内涵体并与细胞膜融合后而释放。外泌体内主要含有核酸、蛋白质和脂质等,并可在清除废弃物质、介导细胞间信息传递、产生免疫耐受、肿瘤治疗疫苗及组织修复再生等方面发挥作用。 再生医学：是指使功能无法自行恢复的病变组织、器官通过临床治疗措施得到结构和功能的重建,其研究的主要内容是干细胞如何发育成组织并应用干细胞潜能进行组织替代疗法,旨在改善受损、功能障碍和缺失的组织及器官的再生。间充质干细胞是目前再生医学研究中广泛使用的细胞类型,而其发挥作用在很大程度上是由其旁分泌主导而实现的。 背景：外泌体是一种微小的膜性囊泡结构,是间充质干细胞旁分泌的重要组成部分,可将信息传递至损伤的细胞或组织从而参与组织再生。 目的：将外泌体及其在再生医学中的研究进展进行综述。 方法：在PubMed、CNKI数据库中进行相关文献检索,以“exosomes,mesenchymal stem cells,tissue regeneration and repair”及“外泌体,间充质干细胞,组织再生修复”为关键词进行检索,通过阅读文题和摘要进行初步筛选,排除与文章主题不相关的文献,最终纳入63篇文献进行结果分析。 结果与结论：外泌体内含多种成分,其提取方法多样,具有清除废弃物质、介导细胞间信息传递、产生免疫耐受及作为肿瘤治疗疫苗等众多功能。间充质干细胞来源外泌体在组织再生与修复中发挥重要作用,具有较好的应用前景,但若要作为无细胞疗法投入临床使用,还需更多深入研究和探索。 ORCID: 0000-0002-9862-334X(杨琨) 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程     

Concise review: Genomic stability of human induced pluripotent stem cells

The usefulness of human induced pluripotent stem cells (hiPSCs) in research and therapeutic applications highly relies on their genomic integrity and stability. Many laboratories including ours have addressed this concern by comparing genomic (at both karyotypic and subkaryotypic levels) and epigenomic abnormalities of hiPSC lines (derived via either DNA- or non-DNA-based methods), as well as human embryonic stem cell lines during long-term culture. A variety of methods have been used for this purpose, such as karyotyping and fluorescent in situ hybridization to detect karyotypic abnormalities, array-based comparative genomic hybridization to detect copy number variations (CNVs), single-nucleotide polymorphism-based microarrays to detect both CNVs and loss of heterozygosity, analysis of integration sites in the genome, and whole genome sequencing for protein-coding exome and DNA methylome profiling. Here, we summarize the progresses in this dynamically evolving field and also discuss how the findings apply to the study and application of hiPSCs.