Viewing Decellularized Amniotic Membrane Through the Lens of Coupled Scaffolding and Drug Delivery Systems in Regenerative Medicine

What's in a Name?

Stem Cell Biotech: Seeking a Piece of the Action

Human stromal (mesenchymal) stem cells (hMSC) represent a group of non-hematopoietic stem cells present in the bone marrow stroma and the stroma of other organs including subcutaneous adipose tissue, placenta, and muscles. They exhibit the characteristics of somatic stem cells of self-renewal and multi-lineage differentiation into mesoderm-type of cells, e.g., to osteoblasts, adipocytes, chondrocytes and possibly other cell types including hepatocytes and astrocytes. Due to their ease of culture and multipotentiality, hMSC are increasingly employed as a source for cells suitable for a number of clinical applications, e.g., non-healing bone fractures and defects and also non-skeletal degenerative diseases like heart failure. Currently, the numbers of clinical trials that employ MSC are increasing. However, several biological and biotechnological challenges need to be overcome to benefit from the full potential of hMSC. In this current review, we present some of the most important and recent advances in understanding of the biology of hMSC and their current and potential use in therapy.

Recent studies indicate that cardiac transfer of adult stem cells can have a favorable impact on tissue perfusion and contractile performance of the infarcted heart. Several cell sources are being explored in an effort to regenerate infarcted myocardium, including hematopoietic stem cells, endothelial progenitor cells, cardiac resident stem cells, bone marrow–derived multipotent stem cells, and mesenchymal stem cells (MSCs). Each of these cell types may have its own profile of advantages, limitations, and practicability issues in specific settings. Studies comparing the regenerative capacity of distinct cell populations are scarce. Most clinical investigators have therefore chosen a pragmatic approach by using unselected bone marrow cells that contain different stem cell populations. Basic scientists, by contrast, are focusing more on specific cell populations in a quest to understand the biological foundations of cell therapy and to identify the most promising stem cells for cardiac regeneration.1 See p 214 MSCs are a rare population of self-renewing, multipotent cells present in adult bone marrow. Although MSCs represent <0.01% of all nucleated bone marrow cells, they can be readily expanded in vitro. In defined culture media, MSCs differentiate into several mesenchymal cell lineages, including cardiomyocytes.2,3 When injected into normal adult myocardium, MSCs differentiate into cardiomyocyte-like cells with sarcomeric organization.4 In an earlier study in pigs with myocardial infarction (MI), MSCs grafted into the infarcted area were shown to express muscle-specific markers and to improve regional wall motion.5 Ease of isolation, high expansion capability, and cardiomyogenic potential have led to the proposition that MSCs may be a good choice for cell-based therapies of MI.6 In a report published in this issue of Circulation , Dai et al7 have …

Received February 28, 2005; revision received April 25, 2005; accepted April 29, 2005. It has now been more than a decade since the first experiments were performed using cell transplantation for the prevention and treatment of heart failure.1–3 Although the biomedical community was initially somewhat skeptical of this approach, a large body of experimental evidence was amassed showing that injected cells could create new tissue and improve function of the failing heart. This evidence, coupled with the recognized limitations of heart failure treatments and the intuitively appealing concept of “regenerative medicine,” has contributed to a crescendo of activity in cell-based cardiac repair. Given the flurry of clinical trials that are currently under way, we think it is timely to review progress over the past 10 years and provide a critical assessment of where the field stands and where it appears to be headed. Cell-based cardiac repair began with studies of skeletal myoblasts derived from skeletal muscle satellite cells.1–3 Myoblasts were the initial choice because of their availability from autologous or syngeneic sources, their ability to proliferate, and their ability to withstand ischemia better than many cell types. Although it was originally hoped that these cells would transdifferentiate into cardiomyocytes, it is now clear that myoblasts remain stubbornly committed to form mature skeletal muscle in the heart3–5 (with the exception of rare cell fusion events at the graft–host interface6). Skeletal muscle is one of the few cell types in the body that does not normally express gap junction proteins, and hence, structural and physiological studies indicate that skeletal muscle cells do not form electromechanical junctions with cardiomyocytes when engrafted into the heart.7,8 Despite this, numerous studies have shown beneficial effects of skeletal myoblast grafting into the infarcted heart in rodents and large animals.8–13 Cardiomyocytes would …

Heart disease remains a leading cause of mortality and a major worldwide healthcare burden. Recent advances in stem cell biology have made it feasible to derive large quantities of cardiomyocytes for disease modeling, drug development, and regenerative medicine. The discoveries of reprogramming and transdifferentiation as novel biological processes have significantly contributed to this paradigm. This review surveys the means by which reprogramming and transdifferentiation can be employed to generate induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and induced cardiomyocytes (iCMs). The application of these patient-specific cardiomyocytes for both in vitro disease modeling and in vivo therapies for various cardiovascular diseases will also be discussed. We propose that, with additional refinement, human disease-specific cardiomyocytes will allow us to significantly advance the understanding of cardiovascular disease mechanisms and accelerate the development of novel therapeutic options.

In the 1960s it was shown that a rare type of tumour called a teratocarcinoma contains cells that are both pluripotent and self‐renewing (Kleinsmith & Pierce, 1964). Pluripotent means the capacity of an individual cell to give rise to all other cell types of the body and the germline. This property is normally restricted to a brief window in early development. Self‐renewal is the production of identical daughter cells while retaining the ability for differentiation. It is the defining feature of a stem cell. The study of teratocarcinoma stem cells led to particular culture conditions that allowed them to be propagated ex vivo without differentiation. In 1981 Martin Evans, Matt Kaufman and Gail Martin found that cells from early mouse embryos exposed to the same culture environment can suspend developmental progression and continue to multiply while remaining pluripotent (Evans & Kaufman, 1981; Martin, 1981). These are embryonic stem (ES) cells. I was completing my undergraduate studies in Oxford at that time and was fortunate to learn about this rather esoteric research from a wonderful teacher, Chris Graham. Chris also talked about parallel discoveries of growth factors and the provocative idea that they might regulate cell fate. I was captivated by the idea of understanding and controlling the pluripotent state » I was captivated by the idea of understanding and controlling the pluripotent state. « and that has been my obsession ever since. I went to Edinburgh to do a PhD on teratocarcinoma stem cells with Martin Hooper. There I was struck by an observation by a previous PhD student that the requirement of the stem cells for co‐culture with a feeder layer could be replaced for a short time by conditioned medium. To me this meant only one thing; a growth factor that could block differentiation. This was not …

Global Challenges in Stem Cell Research and the Many Roads Ahead

<h3>Introduction and history</h3> While regenerative medicine may seem like a novel intervention in the chronic pain armamentarium, its evolution and in a sense its definition has been intricately related to...

Conducting tissue healing and regeneration through biomaterials and morphogens is still an unrealized goal. Understand the multiple roles of the extracellular matrix (ECM) is indeed essential for the design of successful regenerative medicine strategies. During tissue repair and healing, cells receive numerous signals from their immediate ECM microenvironment and adhere by receptor-mediated interactions with ECM components by specialized adhesion receptors, such as integrins. As such, design and modulation of ECM analogs to ligate specific integrins is a promising approach to control cellular processes. Through production of variants of the 9th to 10th type III repeat of fibronectin (FN, FN III9-10) with variable stabilities, we engineered ligands that present different specificities for the integrin α5β1. Furthermore, the FN fragments have been engineered in order to be covalently incorporated into fibrin, a clinical relevant matrix for regenerative medicine. We demonstrated the capacity of α5β1 integrin-specific engagement to influence human mesenchymal stem cell behavior, showing that α5β1 integrin has an important role in the control of their osteogenic differentiation. Specifically, compared to FN, FN fragments with increased specificity for α5β1 versus αvβ3 integrins (FN III9*-10) results in significantly enhanced osteogenic differentiation in 2D and in a clinically relevant fibrin matrix system, while cell attachment/spreading and proliferation were comparable. On the other hand, growth factors (GFs) are key molecules for tissue morphogenesis and healing. However, while they are really promising molecules for a use in regenerative medicine applications, they often fail to prove cost-effective or even clinically efficacious during clinical trials. One of the reasons for this poor translation may lie in the rapid clearance of GFs from tissue sites in vivo, leading to the development of strategies controlling their release. Since FN has been shown to bind GFs from very different families, we first explored the possibility of FN to bind GFs much more broadly, and secondly the possibility of using FN fragments as an anchor for GF retention into fibrin matrix. We found that the 12th to 14th type III repeats of FN (FN III12-14) promiscuously bind GFs from the platelet-derived GF, fibroblast GF, transforming GF-β and neurotrophin families. Overall, 25 new binding interactions were demonstrated, supporting that GF binding may be one of FN's main physiological functions. However, the reasons for such promiscuous binding capacity were still unclear, while evidences from the literature suggested that the close proximity of the major integrin-binding domain, FN III9-10, allows joint integrin/GF-receptor signaling triggered by a complex FN/GFs. Accordingly, we found that FN fragments containing both the integrin- and GF-binding domains (FN III9(*)-10/12-14) could drastically enhance GF activities in vitro. In addition, testing which integrins were involved within these synergistic effects, we found that α5β1 integrin was mainly involved. By the use of FN III9(*)-10/12-14 and fibrin, we could engineer a specific microenvironment allowing sequestration of multiple wild-type GFs, while triggering synergistic signaling between GF-receptors and integrins. In a delayed wound healing model in mouse and in a calvarial bone defect model in rat, GFs delivered with the FN fragment microenvironment were drastically improved in their ability to induce tissue healing, even though a single low dose of GFs was used. Specifically, we established integrin/GF-receptor synergistic activities as a key parameter for GF translation into regenerative medicine treatments and demonstrate a method to exploit this phenomenon. This thesis highlights the absolutely critical role of the microenvironment in modulating signaling of GFs and in driving these molecules forward toward more widespread clinical use.

EMBO Reports (2019) e48172 Stem cell‐based regenerative medicine has experienced turbulent times in recent years that have involved several scandals implicating prominent institutions and numerous retractions of papers from leading journals. But it has also seen real progress being made on the way to the clinic. It reflects the tension between human ambition and hope on one side and the need for hard evidence and solid data on the other side in a field where early expectations ran far ahead of reality. This tension may help explain the recent scandal involving stem cell surgeon Paolo Macchiarini, who was found guilty of scientific misconduct regarding an article in The Lancet , which has since been retracted. It is an ongoing saga as Macchiarini is still publishing in leading journals, even though his reputation as a surgeon and stem cell researcher has been compromised. > … the whole field of regenerative medicine had been tainted by a number of cases where […] researchers had taken short cuts and neglected basic science. The story dates back to 2004, when Macchiarini's team extracted some pig intestine and removed the cells to leave a collagen matrix that was then repopulated with muscle and fibroblasts to generate connective epidermal tissue. The patch was implanted in the airway of a 58‐year‐old patient suffering from respiratory problems after surgery for lung cancer [1]. Macchiarini then expanded this technique to whole tracheas using plastic scaffolds in addition to natural tissue from human donors. In another clinical case, the bare plastic scaffold was populated with stem cells taken from the patient's own bone marrow and implanted in a young female patient in 2008. This propelled Macchiarini almost to rock star status and an appointment by the Karolinska Institute, where he refined his technique by replacing donor windpipes with plastic …

New Japanese Initiatives on Stem Cell Therapies

After the biotech medicine era, symbolized by the progress of genetic engineering and the developments of physiologically active substances such as proteins and cytokines as medicine, the regenerative medicine era, when cells and tissues become medicine, is going to start and getting popular in recent years in the world. In particular, regenerative medicine is highly expected as curative-therapeutic treatments that can cure patients with obstinate diseases and physically impaired function, while the conventional symptomatic treatments are unable to do so. For supporting and enhancing the progress of regenerative medicine, remarkable advancements in regenerative medical sciences, and cell and tissue engineering are desired worldwide. Furthermore, to achieve new treatments based on regenerative medicine, multidisciplinary approaches from various fields such as molecular biology, cell biology, science and engineering, and pharmaceutical and medical sciences are essential. Regenerative medicine should be recognized as a completely new interdisciplinary academic discipline, which is unable to be obtained from the extrapolations of vertically connected and conventional academic disciplines. Therefore, for realizing regenerative medicine, not only the reconstruction of conventional medical science but also the establishment of new academic field, which integrates and assimilates scientific and engineering technologies, and biotechnology, become important. For example, technology controlling the expansion and differentiations of embryonic stem (ES) cells and induced pluripotent stem (iPS) cells is essential for obtaining the sufficient numbers of the cells allowing desired medical treatments to be realized. For separating remaining small amounts of undifferentiated ES and iPS cells from the differentiated cells with a high accuracy, an interdisciplinary research project having the horizontally integration of science, engineering, medicine should be considered. Further, the developments of technologies, which can efficiently transplant somatic cells in the body, are more important than those of cell sources, and new cooperative and integrative systems having various academic disciplines including medicine, science, engineering, and pharmacy are extremely important. For example, harvested cells, which are obtained from culture dishes by treating them with enzymes including trypsin or dispase after being cultured and expanded, are damaged in their structures and functions by enzymatically cleaving their cell-membrane proteins. Upon the direct injection of suspension containing damaged cells following the enzyme treatments to the tissue or organ, approximately 95% of the cells fail to stay in the target, and only less than several percent of the cells transplanted in the organ is speculated to be effective (Hofmann et al., 2005). The unwelcome fact that possible therapeutic effects are expected with a small number of transplanted cells should be noticed seriously. Tissue engineering is extremely important in terms of the more efficient engraftment of cell transplantation and is expected to proceed further with the integration of the technology of biomaterials contacting cell directly and bio- and medical-technologies. One of the tissue engineering approaches is biodegradable polymer scaffold-based methods (Langer and Vacanti, 1993). It is important to promote research that investigates how the shape and function of cells cultured in the scaffolds are maintained after transplantation. In this special issue, the recent progress of tissue engineering approaches using biodegradable polymer scaffolds are reviewed by Rui Reis and his colleagues on periodontal tissue, Charles Vacanti and Koji Kojima on trachea, Toshiharu Shinoka and his colleagues on vasculature, Dietmar Hutmacher and his colleagues on osteochondral tissue, and Stephan Badylak and his colleagues on skeletal muscle. For maintaining cell-dense thicker tissue viability, sufficient amounts of oxygen and nutrients should be supplied into the tissue. However, scaffold-based tissue has a heavy burden to have supplies of oxygen and nutrients from the scaffold surface by diffusion, which is hampered with increasing cell density. The developments of new technologies to break through this problem would be desired. Another approach for tissue engineering is cell sheet-based methods (Yang et al., 2007). Dense monolayered cell sheets that are harvested from temperature responsive culture dishes are fully viable and almost all of the cells are engrafted and keep their function after transplantation. In this special issue, the cutting edge research using cell sheet-based tissue engineering methods are reviewed by Teruo Okano and Kazuo Ohashi on liver and islets, Tatsuya Shimizu and Katsuhisa Matsuura on cardiac tissue, Masayuki Yamato and his colleagues on periodontal tissue, and Masato Sato and his colleagues on articular cartilage. In the cornea, myocardium, periodontal ligament, esophagus, and articular cartilage, the clinical studies with this cell-sheet technology have been already initiated, and the clinical efficacies of these cell-sheet transplantations have been confirmed. Remarkable research projects investigating the preparation of three-dimensional (3-D) cell-sheet tissues by layering cell sheets have been started. Especially challenging is to make capillaries in 3-D layered cell-sheet tissue and allow them to connect with living blood vessels (Sekine et al., 2013) or the micro-channels of artificial vascular beds (Sakaguchi et al., 2013). From these successful studies, the preparations of various organs such as liver, kidney, pancreas, and so forth are expected to be accelerated. Various stem cell types are currently under investigation. Among them, the application of tissue stem cells, also called somatic stem cells, is being developed with remarkable progress (Korbling and Estrov, 2003). Some tissue stem cells have proceeded to clinical trials and even further to general medical treatment. Hematopoietic stem cells (HSCs) are representative of such cells (Weissman and Shizuru, 2008). HSCs have been successfully administered to patients with leukemia for over 50 years (Thomas, 1983). In this special issue, Atsushi Iwama and his colleagues, Yaeko Nakajima-Takagi and Mitsujiro Osawa, review HSCs, including the methods used for identifying and expanding HSCs ex vivo, and the niche cells that control the self-renewal, differentiation, and homing of HSCs. One special type of tissue stem cell has attracted great attention. Mesenchymal stem cells have been intensively studied for more than a decade, with new knowledge accumulating from both basic and applied studies (Kuroda et al., 2011). Importantly, more than 450 clinical studies are currently being performed throughout the world, targeting various diseases, and there are several venture capital companies focusing on mesenchymal stem cells. Mesenchymal stem cells are indeed a hot topic and a major field in basic science, clinical medicine, and medical industry. In this special issue, Yasumasa Kuroda and Mari Dezawa provide an overview of mesenchymal stem cell studies, focusing on three representative sources, bone marrow, adipose tissue, and umbilical cord, and describe the similarities and differences among them. They also describe recent advances in clinical studies and discuss perspectives of mesenchymal stem cell use. Finally, they introduce multilineage-differentiating stress enduring (Muse) cells, which are recently discovered pluripotent stem cells that make up a large percentage of mesenchymal stem cells. Muse cells have attracted attention not only because they explain the triploblastic differentiation ability of mesenchymal stem cells, but also because they are pluripotent but non-tumorigenic. Their review discusses the great potential of Muse cells for regenerative medicine. Neural regeneration is another hot topic in regenerative medicine (Gage, 2000). While there are some candidate stem cells that relate to neural regeneration, in this special issue James St. Johns and Jenny Ekberg review olfactory ensheathing cells. Established central nervous system tissue does not possess regenerative capacity; therefore, the only way to restore damaged brain regions and spinal cord is to supply new neural cells and reconstruct neuronal circuits. Neural stem cells have attracted great attention for quite some time, but the number of available cells from fetal or adult brain is limited. Due to their regenerative capacity and feasibility of application, olfactory ensheathing cells are considered one of the strongest candidates for the treatment of spinal cord injury, and in fact, they have been already applied to patients in some countries. For diseases of complex tissues, such as the kidney and eye, the search for tissue stem cells has not been as simple and straightforward. Motoko Yanagida and her colleague, Koji Takaori, are pioneers in the area of kidney regeneration and stem cells. Here in this special issue, they review kidney stem cells. The retina is an organ with highly sophisticated function, such as information processing ability comparable to that of the brain. In mammals, retinal stem/progenitor cells (RPCs) are suggested to be possible retinal stem cells that are quiescent and exhibit very little activity. A number of different cellular sources of RPCs have been identified in the vertebrate retina. These include RPCs at the retinal margin; pigmented cells in the ciliary body, iris, and retinal pigment epithelium; and Müller cells within the retina. Henry Yip describes the isolation and expansion of RPCs from immature and mature eyes, and their potential application to transplantation in degenerated retinal tissue. James Trosko, the pioneer of tissue stem cells and cancer stem cells, poses questions about the reprogramming hypothesis of iPS cells. His review proposes novel insights into the relation between iPS cells and cancer stem cells. A survey of the stem cell world reveals that tissue stem cells are diverse and complex, just as our bodies are composed of complex sophisticated systems. Our bodies are able to maintain tissue homeostasis perhaps because of the evolutionary development of tissue stem cells to acquire a variety of functions. We hope that this special issue will stimulate development of additional tissue engineering and tissue stem cell studies.

Regeneration that takes place in the human body is limited throughout life. Therefore, when organs are irreparably damaged, they are usually replaced with an artificial device or donor organ. The term "regenerative medicine" covers the restoration or replacement of cells, tissues, and organs. Stem cells play a major role in regenerative medicine by providing the way to repopulate organs damaged by disease. Stem cells have the ability to self renew and to regenerate cells of diverse lineages within the tissue in which they reside. Stem cells could originate from embryos or adult tissues. Growth factors are proteins that may act locally or systemically to affect the growth of cells in several ways. Various cell activities, including division, are influenced by growth factors. Cytokines are a family of low-molecular-weight proteins that are produced by numerous cell types and are responsible for regulating the immune response, inflammation, tissue remodeling and cellular differentiation. Target cells of growth factors and cytokines are mesenchymal, epithelial and endothelial cells. These molecules frequently have overlapping activities and can act in an autocrine or paracrine fashion. A complex network of growth factors and cytokines guides cellular differentiation and regeneration in all organs and tissues. The aim of this paper is to review the role of growth factors and cytokines in different organs or systems and explore their therapeutic application in regenerative medicine. The role of stem cells combined with growth factors and cytokines in the regeneration of vascular and hematopoietic, neural, skeletal, pancreatic, periodontal, and mucosal tissue is reviewed. There is evidence that supports the use of growth factors and cytokines in the treatment of neurological diseases, diabetes, cardiovascular disease, periodontal disease, cancer and its complication, oral mucositis. After solving the ethical issues and establishing clear and reasonable regulations, regenerative medicine through stem cell application combined with specific growth factors and cytokines will have great potential in curing a variety of human diseases.

The objective of the research is to investigate the role of very small embryonic-like stem cells (VSELs™), as well as CD34 + cells, in a study that will compare the efficacy of these two cell types for retinal repair.Licensing agreement: TiGenix & Sobi TiGenix (Belgium; www.tigenix.com)has licensed the marketing and distribution of ChondroCelect ® , the cell-based medicinal product for the repair of cartilage defects of the knee, to the international specialty healthcare company dedicated to rare diseases, Swedish Orphan Biovitrum AB (www.sobi.com).ChondroCelect was the first cellbased product to be approved in Europe.It is currently available for patients and reimbursed in Belgium, The Netherlands and Spain.Sales of ChondroCelect in 2013 were US$5.76 (EU€4.3)million, a growth of 25% on a like-for-like basis over 2012.Sobi will continue to market and distribute the product where it is currently available and has also acquired the exclusive rights to expand the product's availability to patients in multiple additional territories, including the rest of the EU, Norway, Switzerland, Turkey and Russia, plus the countries of the Middle East and North Africa.TiGenix will receive a royalty of 22% of the net sales of ChondroCelect in the first year of the agreement, and 20% of the net sales of ChondroCelect thereafter.There will be no upfront or milestone payments.The agreement took effect on June 1, 2014, and has a duration of 10 years. Launching new projects, products & servicesCatapult