Human embryonic or adult stem cells: an overview on ethics and perspectives for tissue engineering

Engineered organoids in oral and maxillofacial regeneration

Oral and maxillofacial organoids, as three-dimensional study models of organs, have attracted increasing attention in tissue regeneration and disease modeling. However, traditional strategies for organoid construction still fail to precisely recapitulate the key characteristics of real organs, due to the difficulty in controlling the self-organization of cells in vitro. This review aims to summarize the recent progress of novel approaches to engineering oral and maxillofacial organoids. First, we introduced the necessary components and their roles in forming oral and maxillofacial organoids. Besides, we discussed cutting-edge technology in advancing the architecture and function of organoids, especially focusing on oral and maxillofacial tissue regeneration via novel strategy with designed cell-signal scaffold compounds. Finally, current limitations and future prospects of oral and maxillofacial organoids were represented to provide guidance for further disciplinary progression and clinical application to achieve organ regeneration.

Systemic Administration of Allogeneic Cord Blood Mononuclear Cells in Adults with Severe Acute Contusion Spinal Cord Injury: Phase I/IIa Pilot Clinical Study - Safety and Primary Efficacy Evaluation

OBJECTIVES

Current Phase I part of SUBSCI I/IIa study was focused on safety and primary efficacy of multiple systemic infusions of allogeneic unrelated human umbilical cord blood mononuclear cells in patients with severe acute spinal cord contusion having severe neurological deficit. The primary endpoint was safety. The secondary endpoint was the fact of restoration of motor and sensory function in lower limbs within 1-year period.

METHODS

Ten subjects with acute contusion SCI and ASIA A/B deficit were enrolled into Phase I part. Subjects were treated with 4 infusions of group- and rhesus-matched cord blood samples following primary surgery within 3 days post-SCI. All patients were followed-up for 12 months post-SCI. Safety was assessed using adverse events classification depending on severity and relation to cell therapy. Primary efficacy was assessed using dynamics of deficit (ASIA scale).

RESULTS

The overall number of AEs reached 419 in 10 subjects. Only 2 of them were estimated as possibly related to cell therapy, other 417 were definitely unrelated. Both AEs were mild and clinically insignificant. No signs of immunization were found in participants. Analysis of clinical outcomes also demonstrated that cell therapy promotes significant functional restoration of motor function.

CONCLUSIONS

Obtained data suggest that systemic administration of allogenic, non-HLA matched HUCB cells is safe and demonstrates primary efficacy in adults with severe acute contusion SCI and ASIA A/B deficit.

Cells and stimuli in small-caliber blood vessel tissue engineering

The absence of successful solutions in treatments of small-caliber vessel diseases led to the Vascular Tissue Engineering approach to develop functional nonimmunogenic tissue engineered blood vessels. In this context, the choice of cells to be seeded and the microenvironment conditioning are pivotal. Biochemical and biomechanical stimuli seem to activate physiological regulatory pathways that induce the production of molecules and proteins stimulating stem cell differentiation toward vascular lineage and reproducing natural cross-talks among vascular cells to improve the maturation of tissue engineered blood vessels. Thus, this review focuses on (1) available cell sources, and (2) biochemical and biomechanical stimuli, with the final aim to obtain the long-term stability of the endothelium and mechanical properties suitable for withstanding physiological load.

Systematic Review of Induced Pluripotent Stem Cell Technology as a Potential Clinical Therapy for Spinal Cord Injury

Transplantation therapies aimed at repairing neurodegenerative and neuropathological conditions of the central nervous system (CNS) have utilized and tested a variety of cell candidates, each with its own unique set of advantages and disadvantages. The use and popularity of each cell type is guided by a number of factors including the nature of the experimental model, neuroprotection capacity, the ability to promote plasticity and guided axonal growth, and the cells' myelination capability. The promise of stem cells, with their reported ability to give rise to neuronal lineages to replace lost endogenous cells and myelin, integrate into host tissue, restore functional connectivity, and provide trophic support to enhance and direct intrinsic regenerative ability, has been seen as a most encouraging step forward. The advent of the induced pluripotent stem cell (iPSC), which represents the ability to “reprogram” somatic cells into a pluripotent state, hails the arrival of a new cell transplantation candidate for potential clinical application in therapies designed to promote repair and/or regeneration of the CNS. Since the initial development of iPSC technology, these cells have been extensively characterized in vitro and in a number of pathological conditions and were originally reported to be equivalent to embryonic stem cells (ESCs). This review highlights emerging evidence that suggests iPSCs are not necessarily indistinguishable from ESCs and may occupy a different “state” of pluripotency with differences in gene expression, methylation patterns, and genomic aberrations, which may reflect incomplete reprogramming and may therefore impact on the regenerative potential of these donor cells in therapies. It also highlights the limitations of current technologies used to generate these cells. Moreover, we provide a systematic review of the state of play with regard to the use of iPSCs in the treatment of neurodegenerative and neuropathological conditions. The importance of balancing the promise of this transplantation candidate in the light of these emerging properties is crucial as the potential application in the clinical setting approaches. The first of three sections in this review discusses (A) the pathophysiology of spinal cord injury (SCI) and how stem cell therapies can positively alter the pathology in experimental SCI. Part B summarizes (i) the available technologies to deliver transgenes to generate iPSCs and (ii) recent data comparing iPSCs to ESCs in terms of characteristics and molecular composition. Lastly, in (C) we evaluate iPSC-based therapies as a candidate to treat SCI on the basis of their neurite induction capability compared to embryonic stem cells and provide a summary of available in vivo data of iPSCs used in SCI and other disease models.

Adult stem cells derived from skeletal muscle — biology and potential

Skeletal muscle contains at least two distinct populations of adult stem cells — satellite cells and multipotent muscle-derived stem cells. Monopotential satellite cells are located under the basal lamina of muscle fibers. They are capable of giving rise only to cells of myogenic lineage, which play an important role in the processes of muscle regeneration. Multipotent muscle-derived stem cells are considered to be predecessors of the satellite cells. Under proper conditions, both in vitro and in vivo, they undergo myogenic, cardiogenic, chondrogenic, osteogenic and adipogenic differentiation. The main purpose of the present article is to summarize current information about adult stem cells derived from skeletal muscle, and to discuss their isolation and in vitro expansion techniques, biological properties, as well as their potential for regenerative medicine.

Improvement of Contused Spinal Cord in Rats by Cholinergic-like Neuron Therapy

Background

Disability in spinal cord injury is an important medical problem, and cell transplantation is considered as an option for the treatment.

Objectives

The purpose of this study is to use bone marrow stromal cells (BMSCs) derived cholinergic neuron-like cells (CNL) in order to ameliorate the contusion model of spinal cord injury in rats.

Materials and Methods

The CNLs were produced by pre inducing BMSCs with β-mercaptoethanol (BME) followed by inducing with nerve growth factor (NGF). The cells were immunoreactive to neurofilament 200, NeuN, synaptophysin, synapsin, microtubule associated protein-2 and choline acetyl transferase (ChAT). The CNL were transplanted in contused rats (CR), which were sacrificed after 12 weeks.

Results

The results showed that BBB test showed an improvement in the CR, while the quantitative analysis showed that the improvement rate was higher in the rats treated with CNL than those treated with BMSCs only or the untreated animals, similar results were noticed in the improvement index. Immunohistochemical analysis of the tissue section prepared from the CR showed that the transplanted cells were engrafted and integrated in the traumatized spinal cord. The morphometric analysis showed that the volume density of the cavity in the CNL treated rats was significantly lower than that of the untreated ones, while the spinal tissue regeneration index was significantly higher.

Conclusions

The conclusion of the study is that CNL can improve the injured spinal cord.

Transplantation of umbilical cord blood stem cells for treating spinal cord injury

Spinal cord injury (SCI) develops primary and secondary damage to neural tissue and this often results in permanent disability of the motor and sensory functions. However, there is currently no effective treatment except methylprednisolone, and the use of methylprednisolone has also been questioned due to its moderate efficacy and the drug's downside. Regenerative medicine has remarkably developed since the discovery of stem cells, and many studies have suggested the potential of cell-based therapies for neural injury. Especially, the therapeutic potential of human umbilical cord blood cells (hUCB cells) for intractable neurological disorders has been demonstrated using in vitro and vivo models. The hUCB cells are immune naïve and they are able to differentiate into other phenotypes, including the neural lineage. Their ability to produce several neurotropic factors and to modulate immune and inflammatory reactions has also been noted. Recent evidence has emerged suggesting alternative pathways of graft-mediated neural repair that involve neurotrophic effects. These effects are caused by the release of various growth factors that promote cell survival, angiogenesis and anti-inflammation, and this is all aside from a cell replacement mechanism. In this review, we present the recent findings on the stemness properties and the therapeutic potential of hUCB as a safe, feasible and effective cellular source for transplantation in SCI. These multifaceted protective and restorative effects from hUCB grafts may be interdependent and they act in harmony to promote therapeutic benefits for SCI. Nevertheless, clinical studies with hUCB are still rare because of the concerns about safety and efficiency. Among these concerns, the major histocompatibility in allogeneic transplantation is an important issue to be addressed in future clinical trials for treating SCI.

Ethical aspects of tissue engineering: a review

Tissue engineering (TE) is a promising new field of medical technology. However, like other new technologies, it is not free of ethical challenges. Identifying these ethical questions at an early stage is not only part of science's responsibility toward society, but also in the interest of the field itself. In this review, we map which ethical issues related to TE have already been documented in the scientific literature. The issues that turn out to dominate the debate are the use of human embryonic stem cells and therapeutic cloning. Nevertheless, a variety of other ethical aspects are mentioned, which relate to different phases in the development of the field. In addition, we discuss a number of ethical issues that have not yet been raised in the literature.

Human Umbilical Cord Blood Cell Grafts for Brain Ischemia

Irreversible and permanent damage develop immediately adjacent to the region of reduced cerebral blood perfusion in stroke patients. Currently, the proven thrombolytic treatment for stroke, tissue plasminogen activator, is only effective when administered within 3 h after stroke. These disease characteristics should be taken under consideration in developing any therapeutic intervention designed to widen the narrow therapeutic range, especially cell-based therapy. Over the past several years, our group and others have characterized the therapeutic potential of human umbilical cord blood cells for stroke and other neurological disorders using in vitro and vivo models focusing on the cells' ability to differentiate into nonhematopoietic cells including neural lineage, as well as their ability to produce several neurotrophic factors and modulate immune and inflammatory reaction. Rather than the conventional cell replacement mechanism, we advance alternative pathways of graft-mediated brain repair involving neurotrophic effects resulting from release of various growth factors that afford cell survival, angiogenesis, and anti-inflammation. Eventually, these multiple protective and restorative effects from umbilical cord blood cell grafts may be interdependent and act in harmony in promoting therapeutic benefits for stroke.

Morphology of in vitro expanded human muscle-derived stem cells

BACKGROUND

Skeletal muscle contains populations of multipotent adult stem cells also referred to as muscle-derived stem cells.

AIM

The main goal of this study was to isolate and culture human adult stem cells from skeletal muscle and characterize them.

METHODS

Muscle-derived stem cells were isolated from biopsy specimens of femoral muscle. The cells were cultured in Dulbecco's modified Eagle's minimal essential medium supplemented with 10% fetal calf serum and gentamycin. When they reached confluence, they were sub-passaged up to the third passage. Cells from the last passage were prepared for TEM analysis. Production of alpha-actin and desmin was confirmed by histochemistry. Moreover, the phenotypic characterization was performed.

RESULTS

Primary isolated muscle-derived stem cells had a fibroblast-like shape. During subsequent passages they maintained this morphology. TEM analysis showed typical ultrastructural morphology of mesenchymal stem cells. They had large pale nuclei with a large amount of euchromatine. Nuclei were irregular with noticeable nucleoli. Dilated cisterns of rough endoplasmic reticulum were present in cytoplasm. In certain parts of the cytoplasm there were aggregates of granules of glycogen. The products of cells were actively secreted into the extracellular matrix. They expressed alpha-actin and desmin. The results of phenotypic characterization showed that almost all analyzed cells were CD13, CD34, CD56 positive and CD45 negative. Moreover, they did not express anti-human fibroblast surface protein.

CONCLUSIONS

Muscle-derived stem cells exhibited typical characteristics typical for mesenchymal stem cells. After analysis of their differentiation potential they could be used in tissue engineering and regenerative medicine.

Naïve human umbilical cord matrix derived stem cells significantly attenuate growth of human breast cancer cells in vitro and in vivo

The effect of un-engineered (naïve) human umbilical cord matrix stem cells (hUCMSC) on the metastatic growth of MDA 231 xenografts in SCID mouse lung was examined. Three weekly IV injections of 5x10(5) hUCMSC significantly attenuated MDA 231 tumor growth as compared to the saline-injected control. IV injected hUCMSC were detected only within tumors or in close proximity to the tumors. This in vivo result was corroborated by multiple in vitro studies such as colony assay in soft agar and [(3)H]-thymidine uptake. These results suggest that naïve hUCMSC may be a useful tool for cancer cytotherapy.

Human adipose stem cells: a potential cell source for cardiovascular tissue engineering

BACKGROUND/AIMS

A crucial step in providing clinically relevant applications of cardiovascular tissue engineering involves the identification of a suitable cell source. The objective of this study was to identify the exogenous and endogenous parameters that are critical for the differentiation of human adipose stem cells (hASCs) into cardiovascular cells.

METHODS

hASCs were isolated from human lipoaspirate samples, analyzed, and subjected to two differentiation protocols.

RESULTS

As shown by fluorescence-activated cell sorter (FACS) analysis, a population of hASCs expressed stem cell markers including CXCR4, CD34, c-kit, and ABCG2. Further, FACS and immunofluorescence analysis of hASCs, cultured for 2 weeks in DMEM-20%-FBS, showed the expression of smooth muscle cell (SMC)-specific markers including SM alpha-actin, basic calponin, h-caldesmon and SM myosin. hASCs, cultured for 2 weeks in endothelial cell growth medium-2 (EGM-2), formed a network of branched tube-like structures positive for CD31, CD144, and von Willebrand factor. The frequency of endothelial cell (EC) marker-expressing cells was passage number-dependent. Moreover, hASCs attached and formed a confluent layer on top of electrospun collagen-elastin scaffolds. Scanning electron microscopy and DAPI staining confirmed the integration of hASCs with the fibers and formation of a cell-matrix network.

CONCLUSION

Our results indicate that hASCs are a potential cell source for cardiovascular tissue engineering; however, the differentiation capacity of hASCs into SMCs and ECs is passage number- and culture condition-dependent.

Can we build synthetic, multicellular systems by controlling developmental signaling in space and time?

Using biological machinery to make new, functional molecules is an exciting area in chemical biology. Complex molecules containing both 'natural' and 'unnatural' components are made by processes ranging from enzymatic catalysis to the combination of molecular biology with chemical tools. Here, we discuss applying this approach to the next level of biological complexity -- building synthetic, functional biotic systems by manipulating biological machinery responsible for development of multicellular organisms. We describe recent advances enabling this approach, including first, recent developmental biology progress unraveling the pathways and molecules involved in development and pattern formation; second, emergence of microfluidic tools for delivering stimuli to a developing organism with exceptional control in space and time; third, the development of molecular and synthetic biology toolsets for redesigning or de novo engineering of signaling networks; and fourth, biological systems that are especially amendable to this approach.

Isolation of Human Corneal Endothelial Cell Precursors and Construction of Cell Sheets by Precursors

PURPOSE

To review recently published experimental data on human corneal endothelium (CE) precursors.

METHODS

A sphere-forming assay was used for the isolation of human CE precursors from human donor corneas and cultured human CE. CE morphology derived from precursors was compared with that from cultured human CE.

RESULTS

Human CE from donor corneas formed primary and secondary sphere colonies and expressed neural and mesenchymal proteins. The progeny of these colonies had a human-CE-like hexagonal shape and showed transport activity, suggesting that the isolated spheres were indeed precursors of human CE. Similar precursors were isolated from cultured human CE, which provided further evidence that the sphere-forming assay facilitates the mass production of human CE precursors. Cultured human CE obtained in this manner had a regular hexagonal morphology in contrast to passaged, cultured human CE.

CONCLUSION

The sphere-forming assay may become a powerful tool for the regeneration of human CE by precursor injection and the construction of cultured CE sheets.

Novel cell therapy approaches for brain repair

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

Human umbilical cord matrix stem cells: preliminary characterization and effect of transplantation in a rodent model of Parkinson's disease

The umbilical cord contains an inexhaustible, noncontroversial source of stem cells for therapy. In the U.S., stem cells found in the umbilical cord are routinely placed into bio-hazardous waste after birth. Here, stem cells derived from human umbilical cord Wharton's Jelly, called umbilical cord matrix stem (UCMS) cells, are characterized. UCMS cells have several properties that make them of interest as a source of cells for therapeutic use. For example, they 1) can be isolated in large numbers, 2) are negative for CD34 and CD45, 3) grow robustly and can be frozen/thawed, 4) can be clonally expanded, and 5) can easily be engineered to express exogenous proteins. UCMS cells have genetic and surface markers of mesenchymal stem cells (positive for CD10, CD13, CD29, CD44, and CD90 and negative for CD14, CD33, CD56, CD31, CD34, CD45, and HLA-DR) and appear to be stable in terms of their surface marker expression in early passage (passages 4-8). Unlike traditional mesenchymal stem cells derived from adult bone marrow stromal cells, small populations of UCMS cells express endoglin (SH2, CD105) and CD49e at passage 8. UCMS cells express growth factors and angiogenic factors, suggesting that they may be used to treat neurodegenerative disease. To test the therapeutic value of UCMS cells, undifferentiated human UCMS cells were transplanted into the brains of hemiparkinsonian rats that were not immune-suppressed. UCMS cells ameliorated apomorphine-induced rotations in the pilot test. UCMS cells transplanted into normal rats did not produce brain tumors, rotational behavior, or a frank host immune rejection response. In summary, the umbilical cord matrix appears to be a rich, noncontroversial, and inexhaustible source of primitive mesenchymal stem cells.

Human umbilical cord blood-derived f-macrophages retain pluripotentiality after thrombopoietin expansion

We have previously characterized a new type of stem cell from human peripheral blood, termed fibroblast-like macrophage (f-Mphi). Here, using umbilical cord blood as a source, we identified cells with similar characteristics including expression of surface markers (CD14, CD34, CD45, CD117, and CD163), phagocytosis, and proliferative capacity. Further, thrombopoietin (TPO) significantly stimulated the proliferation of cord blood-derived f-Mphi (CB f-Mphi) at low dosage without inducing a megakaryocytic phenotype. Additional experiments demonstrated that TPO-expanded cord blood-derived f-Mphi (TCB f-Mphi) retained their surface markers and differentiation ability. Treatment with vascular endothelial cell growth factor (VEGF) gave rise to endothelial-like cells, expressing Flt-1, Flk-1, von Willebrand Factor (vWF), CD31, acetylated low density lipoprotein internalization, and the ability to form endothelial-like cell chains. In the presence of lipopolysaccharide (LPS) and 25 mM glucose, the TCB f-Mphi differentiated to express insulin mRNA, C-peptide, and insulin. In vitro functional analysis demonstrated that these insulin-positive cells could release insulin in response to glucose and other secretagogues. These findings demonstrate a potential use of CB f-Mphi and may lead to develop new therapeutic strategy for treating dominant disease.

Cell therapy for neuropathic pain in spinal cord injuries

Cell therapy to treat neuropathic pain after spinal cord injury (SCI) is in its infancy. However, the development of cellular strategies that would replace or be used as an adjunct to existing pharmacological treatments for neuropathic pain have progressed tremendously over the past 20 years. The earliest cell therapy studies for pain relief tested adrenal chromaffin cells from rat or bovine sources, placed in the subarachnoid space, near the spinal cord pain- processing pathways. These grafts functioned as cellular minipumps, secreting a cocktail of antinociceptive agents around the spinal cord for peripheral nerve injury, inflammatory or arthritic pain. These initial animal, and later clinical, studies suggested that the spinal intrathecal space was a safe and accessible location for the placement of cell grafts. However, one major problem was the lack of a homogeneous, expandable cell source to supply the antinociceptive agents. Cell lines that can be reversibly immortalised are the next phase for the development of a practical, homogenous cell source. These technologies have been modelled with a variety of murine cell lines, derived from embryonic adrenal medulla or CNS brainstem, in which cells are transplanted, which downregulate their proliferative, oncogenic phenotype either before or after transplant. An alternative approach for existing human cell lines is the use of neural or adrenal precursors, in which the antinociceptive properties are induced by in vitro treatment with molecules that move the cells to an irreversible neural or chromaffin, and non-oncogenic, phenotype. Although such human cell lines are at an early stage of investigation, their clinical antinociceptive potential is significant given the daunting problem of difficult-to-treat neuropathic SCI pain.

Stem cell-based therapy for Parkinson's disease

Motor dysfunctions in Parkinson's disease are considered to be primarily due to the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Pharmacological therapies based on the principle of dopamine replacement are extremely valuable, but suffer from two main drawbacks: troubling side effects (e.g. dyskinesia) and loss of efficacy with disease progression. Transplantation of embryonic dopaminergic neurons has emerged as a therapeutic alternative. Enthusiasm following the success of the initial open-label trials has been dampened by the negative outcome of double-blind placebo controlled trials. Additionally, the emergence of graft-related dyskinesia indicates that the experimental grafting procedure requires further refinement before it can be developed into a therapy. Shortage of embryonic donor tissue limits large-scale clinical transplantation trials. We review three of the most attractive tissue sources of dopaminergic neurons for cell replacement therapy: human embryonic ventral mesencephalic tissue, embryonic and adult multipotent region-specific stem cells and embryonic stem cells. Recent developments in embryonic stem cell research and on their implications for a future transplantation therapy in Parkinson's disease are described. Finally, we discuss how human embryonic stem cells can be differentiated into dopaminergic neurons, and issues such as the numbers of dopaminergic neurons required for success and the risk for teratoma formation after implantation.

Therapeutic effect of insulin-producing cells induced from embryonic stem cells on diabetic mice

AIM: To study the therapeutic effect on diabetic mice of insulin-producing cells induced from embryonic stem cells.

METHODS: Firstly, ESCs were induced to differentiate in serum-free DMEM supplemented with bFGF for more than 3 weeks, and DTZ staining was used to identify the induced IPCs; Secondly, experimental diabetes was induced in 6- to 8-week-old male Balb/c mice by a single intraperitoneal injection (200 mg/kg) of streptozotocin freshly dissolved in 0.1 moL/L of citrate buffer, pH 4.5; Finally, the induced IPCs were harvested at day 21 after differentiation, and grafted subcutaneously in the shoulder of streptozotocin-diabetic mice to observe their glucose-reducing effect.

RESULTS: ESCs could be induced to differentiate into IPCs in serum-free DMEM supplemented with bFGF. The induced IPCs were stained crimson red by DTZ, and their transplantation could reduce blood glucose of diabetic mouse significantly.

CONCLUSION: ESCs can be induced to differentiate into IPCs in serum-free DMEM supplemented with bFGF, and the induced IPCs transplantation has a certain therapeutic effect on diabetic mice.