Use of Lectins to Enrich Mouse ES-Derived Retinal Progenitor Cells for the Purpose of Transplantation Therapy

Lectin Profile Variation in Mesenchymal Stem Cells Derived from Different Sources

Human mesenchymal stem cells (MSCs), a promising source of stem cells for regenerative medicine, have different morphological and functional characteristics. Carbohydrate moieties on the cell surface play an important role, including cell-cell interaction and cell recognition. The objective of this study was to determine possible differences in glycoconjugate distribution patterns of MSCs derived from various sources. MSCs were isolated from adipose tissue, bone marrow, Wharton's jelly, and cord blood. Then, they were stained with FITC-conjugated wheat germ agglutinin (WGA), peanut agglutinin (PNA), concanavalin A (ConA), Ulex europaeus (UEA), Dolichos biflorus (DBA), and Atto-488 conjugated Phytolacca americana (PWM) lectins. The intensity of the reactions was scored using ImageJ software. Flow cytometry was performed to detect the expression of the endothelial marker CD144. The obtained data were analyzed by ANOVA and LSD. Cord blood-derived MSCs showed the most significant staining intensities with all lectins. All MSCs were also moderately stained with PNA. Bone marrow-derived MSCs failed to react with UEA, DBA, and ConA. Wharton's jelly-derived MSCs could also not be stained with ConA. Cord blood-derived MSCs contained 2 subpopulations: osteoclast- and fibroblast-like cells. Both lectin staining intensity and distribution pattern were different in these 2 cell types; therefore, the central part of osteoclast-like cells stained more intensive with PNA and PWM, while that part in fibroblast-like cells stained more intensive with ConA. None of them expressed CD144. The glycoconjugate content of MSCs derived from various sources is different.

Stemming retinal regeneration with pluripotent stem cells

Cell replacement therapy is a promising treatment for irreversible retinal cell death in diverse diseases, such as age-related macular degeneration (AMD), Stargardt's disease, retinitis pigmentosa (RP) and glaucoma. These diseases are all characterized by the degeneration of one or two retinal cell types that cannot regenerate spontaneously in humans. Aberrant retinal pigment epithelial (RPE) cells can be observed through optical coherence tomography (OCT) in AMD patients. In RP patients, the morphological and functional abnormalities of RPE and photoreceptor layers are caused by a genetic abnormality. Stargardt's disease or juvenile macular degeneration, which is characterized by the loss of the RPE and photoreceptors in the macular area, causes central vision loss at an early age. Loss of retinal ganglion cells (RGCs) can be observed in patients with glaucoma. Once the retinal cell degeneration is triggered, no treatments can reverse it. Transplantation-based approaches have been proposed as a universal therapy to target patients with various concomitant diseases. Both the replacement of dead cells and neuroprotection are strategies used to rescue visual function in animal models of retinal degeneration. Diverse retinal cell types derived from pluripotent stem cells, including RPE cells, photoreceptors, RGCs and even retinal organoids with a layered structure, provide unlimited cell sources for transplantation. In addition, mesenchymal stem cells (MSCs) are multifunctional and protect degenerating retinal cells. The aim of this review is to summarize current findings from preclinical and clinical studies. We begin with a brief introduction to retinal degenerative diseases and cell death in diverse diseases, followed by methods for retinal cell generation. Preclinical and clinical studies are discussed, and future concerns about efficacy, safety and immunorejection are also addressed.

Derivation of male germ cells from induced pluripotent stem cells by inducers: A review

Induced pluripotent stem cells (iPSCs) refer to stem cells that are artificially produced using a new technology known as cellular reprogramming, which can use gene transduction in somatic cells. There are numerous potential applications for iPSCs in the field of stem cell biology becauase they are able to give rise to several different cell features of lineages such as three-germ layers. Primordial germ cells, generated via in vitro differentiation of iPSCs, have been demonstrated to produce functional gametes. Therefore, in this review we discussed past and recent advances in the in vitro differentiation of germ cells using pluripotent stem cells with an emphasis on iPSCs. Although this domain of research is still in its infancy, exploring development mechanisms of germ cells is promising, especially in humans, to promote future reproductive and developmental engineering technologies. While few studies have evaluated the ability and efficiency of iPSCs to differentiate toward male germ cells in vitro by different inducers, the given effect was investigated in this review.

Use of lectins in immunohematology

Lectins are carbohydrate binding proteins present in seeds of many plants, especially corals and beans, in fungi and bacteria, and in animals. Apart from their hemagglutinating property, a wide range of functions have been attributed to them. Their importance in the area of immunohematology is immense. They are used to detect specific red cell antigens, to activate different types of lymphocytes, in order to resolve problems related to polyagglutination and so on. The introduction of advanced biotechnological tools generates new opportunities to exploit the properties of lectins, which were not used earlier. Stem cell research is a very important area in transplant medicine. Certain lectins detect surface markers of stem cell. Hence, they are used to understand the developmental biology of stem cells. The role of various lectins in the areas of transfusion and transplant medicine is discussed in detail in this review.

Mouse-induced pluripotent stem cells generated under hypoxic conditions in the absence of viral infection and oncogenic factors and used for ischemic stroke therapy

Induced pluripotent stem (iPS) cells are considered as having the greatest potential for use in cell-based therapies. However, at least two hurdles remain: integrating viral transgenes and introducing the c-Myc and Klf4 oncogenes. In a previous study, fibroblasts were incapable of generating iPS cells in the absence of both oncogenes and viral infection. For the present study, we tested our hypothesis that iPS cells can be generated without oncogenes and viral infection under hypoxic conditions and used for cell therapies. By avoiding oncogenic factors and virus integration, this strategy would decrease the potential for cancer formation. According to our observations, the repeated transfection of two expression plasmids (Oct4 and Sox2) into mouse embryonic fibroblasts (MEFs) and combined hypoxic condition resulted in the generation of a novel iPS cell. At 6 h post-transfection, MEFs were subjected to hypoxic conditions (3% O2) for 24 h; this procedure was repeated four times. The resulting MEFs were seeded on feeder cells on day 9; iPS cell clones were observed 12 days post-seeding and designated as iPS-OSH. Data for cell morphology, stem cell marker staining, gene expression profiles, and embryonic body, teratoma, and chimeric mouse formation indicated iPS-OSH pluripotent capability. Neural precursor cells differentiated from iPS-OSH cells were used to treat an ischemic stroke mouse model; results from a behavior analysis indicate that the therapeutic group surpassed the control group. Further, iPS-OSH-derived neural precursor cells differentiated into neurons and astrocytes in mouse stroke brains. In conclusion, we generated a novel iPS-OSH in the absence of viral infection and oncogenic factors and could use it for ischemic stroke therapy.

Using human induced pluripotent stem cells to treat retinal disease

The eye is an ideal target for exploiting the potential of human induced pluripotent stem cell (hiPSC) technology in order to understand disease pathways and explore novel therapeutic strategies for inherited retinal disease. The aim of this article is to map the pathway from state-of-the art laboratory-based discoveries to realising the translational potential of this emerging technique. We describe the relevance and routes to establishing hiPSCs in selected models of human retinal disease. Additionally, we define pathways for applying hiPSC technology in treating currently incurable, progressive and blinding retinal disease.

Embryonic stem cell markers

Embryonic stem cell (ESC) markers are molecules specifically expressed in ES cells. Understanding of the functions of these markers is critical for characterization and elucidation for the mechanism of ESC pluripotent maintenance and self-renewal, therefore helping to accelerate the clinical application of ES cells. Unfortunately, different cell types can share single or sometimes multiple markers; thus the main obstacle in the clinical application of ESC is to purify ES cells from other types of cells, especially tumor cells. Currently, the marker-based flow cytometry (FCM) technique and magnetic cell sorting (MACS) are the most effective cell isolating methods, and a detailed maker list will help to initially identify, as well as isolate ESCs using these methods. In the current review, we discuss a wide range of cell surface and generic molecular markers that are indicative of the undifferentiated ESCs. Other types of molecules, such as lectins and peptides, which bind to ESC via affinity and specificity, are also summarized. In addition, we review several markers that overlap with tumor stem cells (TSCs), which suggest that uncertainty still exists regarding the benefits of using these markers alone or in various combinations when identifying and isolating cells.

Adequate Time Window and Environmental Factors Supporting Retinal Graft Cell Survival in rd Mice

Postnatal photoreceptor cells can be integrated into the wild-type adult retina in mice, and retinal transplantation is now one therapeutic option for retinal degenerative diseases when photoreceptor degeneration is the primary cause of the disease. The aim of this study was to specify the optimal time window during the course of retinal degeneration and to modulate the host and/or graft environment for a successful transplantation. We first studied the background features of the mice with phosphodiesterase 6b (PDE6b) gene mutation (rd; C3H/Hej) and found that the infiltration of microglia and glial fibrillary acidic protein (GFAP) expression once increased at the peak of rod death (∼2-3 weeks of age) but then reduced for a following period until gliosis began to take place with enhanced GFAP expression (∼8 weeks of age). The postnatal retinal cells (p4-p7) were successfully transplanted during this period with neurite extension into the host retina. In later transplantations (6 or 8 weeks of age), graft cells survived better in the presence of chondroitinase ABC (ChABC), which digests chondroitin sulfate proteoglycan (CSPG), an essential component of gliosis. In contrast, in earlier transplantations (4 weeks of age), graft cells survived better in the presence of valproic acid (VPA), a neural differentiating reagent, or glatiramer acetate, an immune modulator. These suggest that, immediately after the outer nuclear layer (ONL) degeneration, an inflammatory reaction may be easily induced but the host neurons may be more able to accept donor cells in the presence of neural differentiating factor. These results will help optimize transplantation conditions when we consider clinical application.

Differing lectin binding profiles among human embryonic stem cells and derivatives aid in the isolation of neural progenitor cells

Human embryonic stem cells (hESCs) and their differentiated progeny allow for investigation of important changes/events during normal embryonic development. Currently most of the research is focused on proteinacous changes occurring as a result of differentiation of stem cells and little is known about changes in cell surface glycosylation patterns. Identification of cell lineage specific glycans can help in understanding their role in maintenance, proliferation and differentiation. Furthermore, these glycans can serve as markers for isolation of homogenous populations of cells. Using a panel of eight biotinylated lectins, the glycan expression of hESCs, hESCs-derived human neural progenitors (hNP) cells, and hESCs-derived mesenchymal progenitor (hMP) cells was investigated. Our goal was to identify glycans that are unique for hNP cells and use the corresponding lectins for cell isolation. Flow cytometry and immunocytochemistry were used to determine expression and localization of glycans, respectively, in each cell type. These results show that the glycan expression changes upon differentiation of hESCs and is different for neural and mesenchymal lineage. For example, binding of PHA-L lectin is low in hESCs (14±4.4%) but significantly higher in differentiated hNP cells (99±0.4%) and hMP cells (90±3%). Three lectins: VVA, DBA and LTL have low binding in hESCs and hMP cells, but significantly higher binding in hNP cells. Finally, VVA lectin binding was used to isolate hNP cells from a mixed population of hESCs, hNP cells and hMP cells. This is the first report that compares glycan expression across these human stem cell lineages and identifies significant differences. Also, this is the first study that uses VVA lectin for isolation for human neural progenitor cells.

Characterization of Axon Formation in the Embryonic Stem Cell-Derived Motoneuron

The developing neural cell must form a highly organized architecture to properly receive and transmit nerve signals. Neural formation from embryonic stem (ES) cells provides a novel system for studying axonogenesis, which are orchestrated by polarity-regulating molecules. Here the ES-derived motoneurons, identified by HB9 promoter-driven green fluorescent protein (GFP) expression, showed characteristics of motoneuron-specific gene expression. In the majority of motoneurons, one of the bilateral neurites developed into an axon that featured with axonal markers, including Tau 1, vesicle acetylcholine transporter, and synaptophysin. Interestingly, one third of the motoneurons developed bi-axonal processes but no multiple axonal GFP cell was found. The neuronal polarity-regulating proteins, including the phosphorylated AKT and ERK, were compartmentalized into both of the bilateral axonal tips. Importantly, this aberrant axon morphology was still present after the engraftment of GFP+ neurons into the spinal cord, suggesting that even a mature neural environment fails to provide a proper niche to guide normal axon formation. These findings underscore the necessity for evaluating the morphogenesis and functionality of neurons before the clinical trials using ES or somatic stem cells.

Induced pluripotent stem (iPS) cell research overview

Stem cells are capable of self-renewal and differentiation into a wide range of cell types with multiple clinical therapeutic applications. The two most important issues associated with embryonic stem (ES) cells are immune rejection and medical ethics. In 2006, induced pluripotent (iPS) cells were generated from somatic cells via the introduction of four transcriptional factors: OCT4, SOX2, c-MYC, and KLF4. Researchers found that iPS cell morphology, proliferation, surface antigens, gene expression, telomerase activity, and the epigenetic status of pluripotent cell-specific genes were similar to the same characteristics in ES cells. iPS cells are capable of overcoming hurdles associated with ES cells due to their generation from mature somatic cells (e.g., fibroblasts). For this reason, iPS cells are considered an increasingly important cell therapy technology. iPS cell production entails the use of retroviruses, lentiviruses, adenoviruses, plasmid transfections, transposons, or recombinant proteins. In this article we discuss the advantages and limitations of each strategy and address issues associated with clinical trials, including the potential for liver tumor formation and low generation efficiency.