Stem cell technologies in regenerative medicine

The IIR Life Sciences conference on stem cell technologies in regenerative medicine was held in London, UK on 11 – 12 July 2002. The conference covered not only technologies but also ethical/regulatory and financial aspects of embryonic stem (ES) cell therapy. An excellent introduction to embryonic stem cells was given by Prof. William Kridel (Ferghana Partners, London, UK). Details of basic technologies are not described as they are covered in a detailed report on cell therapy [1]. Due to limitation of space only a selected few of the seventeen presentations are reported here.     

Stem cell bioengineering for regenerative medicine

Stem cells can be used to treat a variety of diseases and several recent studies in animal models demonstrate the potential of bioengineering strategies targeting adult and embryonic stem cells. In order to obtain the desired cells for transplantation, stem cell bioengineering approaches entail the manipulation of environmental signals influencing cell survival, proliferation, self-renewal and differentiation. In that regard, multivariate analytical approaches have been used with success to optimise different stem cell culture processes. The genetic or molecular enhancement of stem cells is also a powerful means to control their proliferation or differentiation or to correct genetic defects in recipients. In the future, systems-level approaches have the potential to revolutionise the field of stem cell bioengineering by improving our understanding of regulatory networks controlling cellular behaviour. This advance in basic biology will be instrumental for the implementation of many stem cell-based regenerative therapies at the clinical level, as treatment accessibility will depend on the development of robust technologies to produce sufficient cell numbers.     

Stem cell senescence and regenerative paradigms

The term "cellular senescence" denotes a cellular response to several stressors that results in irreversible growth arrest, alterations of the gene expression profile, epigenetic modifications, and an altered secretome, all of which eventually impair the reparative properties of primitive cells, adding a layer of complexity to the field of regenerative medicine. The purpose of this review is to illustrate how cellular senescence could affect tissue repair and to propose interventions that aim at interfering with it.     

Nanotechnologies in regenerative medicine

Abstract

Nanotechnology offers promising perspectives in biomedical research as well as in clinical practice. To cover some of the latest nanotechnology trends in regenerative medicine, this review will focus on the use of nanomaterials for tissue engineering and cell therapy. Nanofibrous materials that mimic the native extracellular matrix and promote the adhesion of various cells are being developed as tissue-engineered scaffolds for the skin, bone, vasculature, heart, cornea, nervous system, and other tissues. A range of novel materials has been developed to enhance the bioactive or therapeutic properties of these nanofibrous scaffolds via surface modifications, including the immobilization of functional cell-adhesive ligands and bioactive molecules such as drugs, enzymes and cytokines. As a new approach, nanofibers prepared by using industrial scale needleless technology have been recently introduced, and their use as scaffolds to treat spinal cord injury or as cell carriers for the regeneration of the injured cornea is the subject of much current study. Cell therapy is a modern approach of regenerative medicine for the treatment of various diseases or injuries. To follow the migration and fate of transplanted cells, superparamagnetic iron oxide nanoparticles have been developed for cell labeling and non-invasive MRI monitoring of cells in the living organism, with successful applications in, e.g, the central nervous system, heart, liver and kidney and also in pancreatic islet and stem cell transplantation.     

Stem cell labeling for noninvasive delivery and tracking in cardiovascular regenerative therapy

Clinical and basic scientific studies of stem cell-based therapies have shown promising results for cardiovascular diseases. Despite a rapid transition from animal studies to clinical trials, the mechanisms by which stem cells improve heart function are yet to be fully elucidated. To optimize cell therapies in patients will require a noninvasive means to evaluate cell survival, biodistribution and fate in the same subject over time. Cell labeling offers the ability to image distinct cell lineages in vivo and investigate the efficacy of these therapies using standard noninvasive imaging techniques. In this article, we will discuss the most promising cell labeling techniques for translation to clinical cardiovascular applications.     

Stem cells: a revolution in therapeutics-recent advances in stem cell biology and their therapeutic applications in regenerative medicine and cancer therapies

Basic and clinical research accomplished during the last few years on embryonic, fetal, amniotic, umbilical cord blood, and adult stem cells has constituted a revolution in regenerative medicine and cancer therapies by providing the possibility of generating multiple therapeutically useful cell types. These new cells could be used for treating numerous genetic and degenerative disorders. Among them, age-related functional defects, hematopoietic and immune system disorders, heart failures, chronic liver injuries, diabetes, Parkinson's and Alzheimer's diseases, arthritis, and muscular, skin, lung, eye, and digestive disorders as well as aggressive and recurrent cancers could be successfully treated by stem cell-based therapies. This review focuses on the recent advancements in adult stem cell biology in normal and pathological conditions. We describe how these results have improved our understanding on critical and unique functions of these rare sub-populations of multipotent and undifferentiated cells with an unlimited self-renewal capacity and high plasticity. Finally, we discuss some major advances to translate the experimental models on ex vivo and in vivo expanded and/or differentiated stem cells into clinical applications for the development of novel cellular therapies aimed at repairing genetically altered or damaged tissues/organs in humans. A particular emphasis is made on the therapeutic potential of different tissue-resident adult stem cell types and their in vivo modulation for treating and curing specific pathological disorders.     

Research in retinal regenerative medicine

Although adult neurogenesis is limited in regions, accumulating evidence indicates the existence of neural regeneration even in non-neurogenic regions. In the adult retina, Müller glias generate new neurons in response to injury. Although the naively regenerated neurons were a very few in number, it could be increased by Wnt treatment. Retinal cell transplantation is another strategy for retinal regeneration. The cell source for transplantation will be prepared, for example from ES cells. There are some ways to enhance the integration of grafted cells into the host retina. We need to understand the mechanisms for integration of newly generated cells or grafted cells into existing neural networks, and to determine functional recovery in animal models of the retinal diseases.     

Social effects in regenerative medicine

Tissue engineering is a key for advanced medical technologies to cure incurable diseases. The technology gives not only medical progress but also economical impact. In the lecture, I should like to overview the approach to industrial application.     

Challenges towards regenerative medicine

Regenerative medicine is a promising approach to treat patients with severe cardiac failure. Since embryonic stem cells (ES cells) easily differentiate into cardiomyocytes, ES cells are thought to be a good candidate resource for cardiac cell transplantation therapy. However, molecular mechanism of cardiac differentiation is still largely unknown. Here we discuss our present approach to understand the mechanism of cardiogenesis at the molecular level as well as novel genes and cascades that are important for cardiac differentiation. Further observation will help to establish the new strategy of regenerative medicine for patients with cardiac failure.     

Cell delivery in regenerative medicine: the cell sheet engineering approach.

Recently, cell-based therapies have developed as a foundation for regenerative medicine. General approaches for cell delivery have thus far involved the use of direct injection of single cell suspensions into the target tissues. Additionally, tissue engineering with the general paradigm of seeding cells into biodegradable scaffolds has also evolved as a method for the reconstruction of various tissues and organs. With success in clinical trials, regenerative therapies using these approaches have therefore garnered significant interest and attention. As a novel alternative, we have developed cell sheet engineering using temperature-responsive culture dishes, which allows for the non-invasive harvest of cultured cells as intact sheets along with their deposited extracellular matrix. Using this approach, cell sheets can be directly transplanted to host tissues without the use of scaffolding or carrier materials, or used to create in vitro tissue constructs via the layering of individual cell sheets. In addition to simple transplantation, cell sheet engineered constructs have also been applied for alternative therapies such as endoscopic transplantation, combinatorial tissue reconstruction, and polysurgery to overcome limitations of regenerative therapies and cell delivery using conventional approaches.     

Hyaluronic acid-based clinical biomaterials derived for cell and molecule delivery in regenerative medicine

The development of injectable and biocompatible vehicles for delivery, retention, growth, and differentiation of stem cells is of paramount importance for regenerative medicine. For cell therapy and the development of clinical combination products, we created a hyaluronan (HA)-based synthetic extracellular matrix (sECM) that provides highly reproducible, manufacturable, approvable, and affordable biomaterials. The composition of the sECM can be customized for use with progenitor and mature cell populations obtained from skin, fat, liver, heart, muscle, bone, cartilage, nerves, and other tissues. This overview describes the design criteria for “living” HA derivatives, and the many uses of this in situ crosslinkable HA-based sECM hydrogel for three-dimensional (3-D) culture of cells in vitro and translational use in vivo. Recent advances allow rapid expansion and recovery of cells in 3-D, and the bioprinting of engineered tissue constructs. The uses of HA-derived sECMs for cell and molecule delivery in vivo will be reviewed, including applications in cancer biology and tumor imaging.     

Viral vector-mediated transgenic cell therapy in regenerative medicine: safety of the process

Introduction: There are safety concerns regarding viral vectors in regenerative medicine research because of adverse experiences in conventional gene therapy with systemic delivery of recombinant virus. Transgenic cell therapy emerges as an attractive strategy, in which the genes of interest are delivered in vitro into isolated cells first; instead of transgene vectors, these transgenic cells are then implanted back to the host. This ex vivo strategy enables the examination of cell viability and phenotype before subsequent transplantation and prevents to the most extent the potential delivery-related hazards caused by exposure of viral components to the host. The transgenic implants are often localized, thus traceable for safety monitoring except those cases involving systemic distribution of transgenic cells.

Areas covered: The safety of ex vivo process used in viral vector-mediated transgenic cell therapy for regenerative medicine purpose.

Expert opinion: Safety concerns related to viral vector delivery can be dispelled in the majority of regenerative medicine applications by transgenic cell therapy. The ex vivo process executes in vitro transfection before subsequent transplantation of transgenic cells so that it avoids the exposure of viral components (particularly capsids or envelops) to the host, while this exposure is inevitable in conventional in vivo gene therapy. Besides, the practice of localized cell implantation and in vitro manipulation also reinforce the safety of transgenic cell therapy. Given the significantly reduced delivery-related hazard, viral vector-mediated transgenic cell therapy can be generally considered as a safe approach for most regenerative medicine applications.     

Cell source for regenerative medicine

Mesenchymal stem cells (MSCs) are a potential cellular source for stem cell-based therapy, since they have the ability to proliferate and differentiate into mesodermal tissues. Human MSCs have been used clinically to treat patients with graft versus host disease and osteogenesis imperfecta. We previously showed that murine and human marrow-derived MSCs can differentiate into cardiomyocytes, skeletal myocytes, osteoblasts, chondroblasts, adipocytes, and neuron. We here show that sources of MSCs with multipotency includes placenta, endometrium, menstrual blood, umbilical cord, cartilage and so on. Differentiation potentials of MSCs depend on cell source, implying that MSCs obtained from each source have differential default state ex vivo.     

Biomaterials essential to regenerative medicine

Biomaterial is one of the most important factors to be developed in regenerative medicine. In this paper, the biomaterials essential to regenerative medicine were described. Biomaterials in regenerative medicine are classified into 5 categories; 1) Biomaterials for cell culture, 2) Biomaterials for cell inducement, 3) Biomaterials for scaffold, 4) Biomaterials for immuno-isolation, 5) Biomaterials assist to regenerative medicine. As for 1), temperature responsible gel that can take out the cultured cell sheet without use protein breakdown enzyme, is mainly introduced. Micro-photolithography to make a micro patterning for cell inducement, kinds of materials for scaffold, isolated membrane and micro capsules, carrier for cell growth factors are mentioned in 2) to 5).     

The regenerative medicine laboratory: facilitating stem cell therapy for equine disease

This article focuses on the emerging field of equine regenerative medicine with an emphasis on the use of mesenchymal stem cells (MSCs) for orthopedic diseases. We detail laboratory procedures and protocols for tissue handling and MSC isolation, characterization, expansion, and cryopreservation from bone marrow, fat, and placental tissues. We provide an overview of current clinical uses for equine MSCs and how MSCs function to heal tissues. Current laboratory practices in equine regenerative medicine mirror those in the human field. However, the translational use of autologous and allogeneic MSCs for patient therapy far exceeds what is currently permitted in human medicine.     

Review of basic studies about the cardiac stem cell and regenerative medicine

The availability of enough cardiomyocytes to transplant as a cardiac tissue is able to read the achievement of regenerative cardiac medicine. Tissue derived stem cells, embryonic stem (ES) cells and induced pluripotent stem (iPS) cells are all potential cell sources. Several types of cardiac tissue stem cells have already been reported, and we describe about the characteristics and multipotency of these tissue stem cells with an accurate comparison. ES cells and iPS cells are highly proliferative and suitable for mass production, and efficient protocols for selective cardiomyocyte induction using ES cells and iPS cells are also significant. On the other hand, these cells still have several issues about purification and safety as well as ethical problems.