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Concept: Stem cells


Nonviral conversion of skin or blood cells into clinically useful human induced pluripotent stem cells (hiPSC) occurs in only rare fractions (∼0.001%-0.5%) of donor cells transfected with non-integrating reprogramming factors. Pluripotency induction of developmentally immature stem-progenitors is generally more efficient than differentiated somatic cell targets. However, the nature of augmented progenitor reprogramming remains obscure, and its potential has not been fully explored for improving the extremely slow pace of non-integrated reprogramming. Here, we report highly optimized four-factor reprogramming of lineage-committed cord blood (CB) myeloid progenitors with bulk efficiencies of ∼50% in purified episome-expressing cells. Lineage-committed CD33(+)CD45(+)CD34(-) myeloid cells and not primitive hematopoietic stem-progenitors were the main targets of a rapid and nearly complete non-integrated reprogramming. The efficient conversion of mature myeloid populations into NANOG(+)TRA-1-81(+) hiPSC was mediated by synergies between hematopoietic growth factor (GF), stromal activation signals, and episomal Yamanaka factor expression. Using a modular bioinformatics approach, we demonstrated that efficient myeloid reprogramming correlated not to increased proliferation or endogenous Core factor expressions, but to poised expression of GF-activated transcriptional circuits that commonly regulate plasticity in both hematopoietic progenitors and embryonic stem cells (ESC). Factor-driven conversion of myeloid progenitors to a high-fidelity pluripotent state was further accelerated by soluble and contact-dependent stromal signals that included an implied and unexpected role for Toll receptor-NFκB signaling. These data provide a paradigm for understanding the augmented reprogramming capacity of somatic progenitors, and reveal that efficient induced pluripotency in other cell types may also require extrinsic activation of a molecular framework that commonly regulates self-renewal and differentiation in both hematopoietic progenitors and ESC.

Concepts: Developmental biology, Stem cell, Stem cells, Cell biology, Cellular differentiation, Embryonic stem cell, Induced pluripotent stem cell, Pluripotency


The integumentary organ system is a complex system that plays important roles in waterproofing, cushioning, protecting deeper tissues, excreting waste, and thermoregulation. We developed a novel in vivo transplantation model designated as a clustering-dependent embryoid body transplantation method and generated a bioengineered three-dimensional (3D) integumentary organ system, including appendage organs such as hair follicles and sebaceous glands, from induced pluripotent stem cells. This bioengineered 3D integumentary organ system was fully functional following transplantation into nude mice and could be properly connected to surrounding host tissues, such as the epidermis, arrector pili muscles, and nerve fibers, without tumorigenesis. The bioengineered hair follicles in the 3D integumentary organ system also showed proper hair eruption and hair cycles, including the rearrangement of follicular stem cells and their niches. Potential applications of the 3D integumentary organ system include an in vitro assay system, an animal model alternative, and a bioengineered organ replacement therapy.

Concepts: Developmental biology, Stem cell, Stem cells, Organ, Skin, In vitro, Induced pluripotent stem cell, Sebaceous gland


Glial proliferation and activation are associated with disease progression in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia. In this study, we describe a unique platform to address the question of cell autonomy in transactive response DNA-binding protein (TDP-43) proteinopathies. We generated functional astroglia from human induced pluripotent stem cells carrying an ALS-causing TDP-43 mutation and show that mutant astrocytes exhibit increased levels of TDP-43, subcellular mislocalization of TDP-43, and decreased cell survival. We then performed coculture experiments to evaluate the effects of M337V astrocytes on the survival of wild-type and M337V TDP-43 motor neurons, showing that mutant TDP-43 astrocytes do not adversely affect survival of cocultured neurons. These observations reveal a significant and previously unrecognized glial cell-autonomous pathological phenotype associated with a pathogenic mutation in TDP-43 and show that TDP-43 proteinopathies do not display an astrocyte non-cell-autonomous component in cell culture, as previously described for SOD1 ALS. This study highlights the utility of induced pluripotent stem cell-based in vitro disease models to investigate mechanisms of disease in ALS and other TDP-43 proteinopathies.

Concepts: DNA, Developmental biology, Stem cell, Stem cells, Cell biology, Amyotrophic lateral sclerosis, Induced pluripotent stem cell, Pluripotency


BACKGROUND: Stem cell injection therapies have been proposed to overcome the limited efficacy and adverse reactions of bulking agents. However, most have significant limitations, including painful procurement, requirement for anesthesia, donor site infection and a frequently low cell yield. Recently, human amniotic fluid stem cells (hAFSCs) have been proposed as an ideal cell therapy source. In this study, we investigated whether periurethral injection of hAFSCs can restore urethral sphincter competency in a mouse model. METHODS: Amniotic fluids were collected and harvested cells were analyzed for stem cell characteristics and in vitro myogenic differentiation potency. Mice underwent bilateral pudendal nerve transection to generate a stress urinary incontinence (SUI) model and received either periurethral injection of hAFSCs, periurethral injection of Plasma-Lyte (control group), or underwent a sham (normal control group). For in vivo cell tracking, cells were labeled with silica-coated magnetic nanoparticles containing rhodamine B isothiocyanate (MNPs@SiO2 (RITC)) and were injected into the urethral sphincter region (n = 9). Signals were detected by optical imaging. Leak point pressure and closing pressure were recorded serially after injection. Tumorigenicity of hAFSCs was evaluated by implanting hAFSCs into the subcapsular space of the kidney, followed two weeks later by retrieval and histologic analysis. RESULTS: Flow activated cell sorting showed that hAFSCs expressed mesenchymal stem cell (MSC) markers, but no hematopoietic stem cell markers. Induction of myogenic differentiation in the hAFSCs resulted in expression of PAX7 and MYOD at Day 3, and DYSTROPHIN at Day 7. The nanoparticle-labeled hAFSCs could be tracked in vivo with optical imaging for up to 10 days after injection. Four weeks after injection, the mean LPP and CP were significantly increased in the hAFSC-injected group compared with the control group. Nerve regeneration and neuromuscular junction formation of injected hAFSCs in vivo was confirmed with expression of neuronal markers and acetylcholine receptor. Injection of hAFSCs caused no in vivo host CD8 lymphocyte aggregation or tumor formation. CONCLUSIONS: hAFSCs displayed MSC characteristics and could differentiate into cells of myogenic lineage. Periurethral injection of hAFSCs into an SUI animal model restored the urethral sphincter to apparently normal histology and function, in absence of immunogenicity and tumorigenicity.

Concepts: Gene expression, Developmental biology, Stem cell, Mesenchymal stem cell, Bone marrow, Stem cells, Cell biology, Cellular differentiation


In a recent study published in this journal it was claimed that the rate of publications from US-based authors in the human embryonic stem cell (hESC) research field was slowing or even declining from 2008 to 2010. It was assumed that this is the result of long-term effects of the Bush administration’s funding policy for hESC research and the uncertain policy environment of recent years. In the present study, we analyzed a pool of more than 1,700 original hESC research papers published world-wide from 2007 to 2011. In contrast to the previous study, our results do not support the hypothesis of a decline in the productivity of US-based research but rather confirm a nearly unchanged leading position of US research in the hESC field with respect to both publication numbers and impact of research. Moreover, we analyzed about 500 papers reporting original research involving human induced pluripotent stem cells (hiPSCs) published through 2011 and found a dominant position of US research in this research field as well.

Concepts: Stem cell, Stem cells, Cell biology, Academic publishing, Embryonic stem cell, Induced pluripotent stem cell, Pluripotency, Martin Evans


Human multipotent skin derived precursor cells (SKPs) are traditionally sourced from dissociated dermal tissues; therefore, donor availability may become limiting. Here we demonstrate that both normal and diseased adult human dermal fibroblasts (DF) pre-cultured in conventional monolayers are capable of forming SKPs (termed m-SKPs). Moreover, we show that these m-SKPs can be passaged and that cryopreservation of original fibroblast monolayer cultures does not reduce m-SKP yield; however, extensive monolayer passaging does. Like SKPs generated from dissociated dermis, these m-SKPs expressed nestin, fibronectin and versican at the protein level. At the transcriptional level, m-SKPs derived from normal adult human DF, expressed neural crest stem cell markers such as p75NTR, embryonic stem cell markers such as Nanog and the mesenchymal stem cell marker Dermo-1. Furthermore, appropriate stimuli induced m-SKPs to differentiate down either mesenchymal or neural lineages resulting in lipid accumulation, calcification and S100β or β-III tubulin expression (with multiple processes). m-SKP yield was greater from neonatal foreskin cultures compared to those from adult DF cultures; however, the former showed a greater decrease in m-SKP forming capacity after extensive monolayer passaging. m-SKP yield was greater from adult DF cultures expressing more alpha-smooth muscle actin (αSMA). In turn, elevated αSMA expression correlated with cells originating from specimens isolated from biopsies containing more terminal hair follicles; however, αSMA expression was lost upon m-SKP formation. Others have shown that dissociated human hair follicle dermal papilla (DP) are a highly enriched source of SKPs. However, conversely and unexpectedly, monolayer cultured human hair follicle DP cells failed to form m-SKPs whereas those from the murine vibrissae follicles did. Collectively, these findings reveal the potential for using expanded DF cultures to produce SKPs, the heterogeneity of SKP forming potential of skin from distinct anatomical locations and ages, and question the progenitor status of human hair follicle DP cells.

Concepts: Protein, Stem cell, Stem cells, Embryonic stem cell, Skin, Hair, Hair follicle, Stem cell marker


Stem cell-based treatment for Huntington’s disease (HD) is an expanding field of research. Although various stem cells have been shown to be beneficial in vivo, no long standing clinical effect has been demonstrated. To address this issue, we are developing a stem cell-based therapy designed to improve the microenvironment of the diseased tissue via delivery of neurotrophic factors (NTFs). Previously, we established that bone marrow derived human mesenchymal stem cells (MSCs) can be differentiated using medium based cues into NTF-secreting cells (NTF+ cells) that express astrocytic markers. NTF+ cells were shown to alleviate neurodegeneration symptoms in several disease models in vitro and in vivo, including the model for excitotoxicity. In the present study, we explored if the timing of intrastriatal transplantation of hNTF+ cells into the R6/2 transgenic mouse model for HD influences motor function and survival. One hundred thousand cells were transplanted bilaterally into the striatum of immune-suppressed mice at 4.5, 5.5 and 6.5 weeks of age. Contrary to our expectations, early transplantation of NTF+ cells did not improve motor function or overall survival. However, late (6.5 weeks) transplantation resulted in a temporary improvement in motor function and an extension of life span relative to that observed for PBS treated mice. We conclude that late transplantation of NTF+ cells induces a beneficial effect in this transgenic model for HD. Since no transplanted NTF+ cells could be detected in vivo, we suspect that the temporary nature of the beneficial effect is due to poor survival of transplanted cells. In general, we submit that NTF+ cells should be further evaluated for the therapy of HD.

Concepts: Stem cell, Mesenchymal stem cell, Bone marrow, Stem cells, Cellular differentiation, In vivo, Huntington's disease, Brain-derived neurotrophic factor


The use of induced pluripotent stem cells (iPSCs) has been postulated to be the most effective strategy for developing patient-specific respiratory epithelial cells, which may be valuable for lung-related cell therapy and lung tissue engineering. We generated a relatively homogeneous population of alveolar epithelial type II (AETII) and type I (AETI) cells from human iPSCs that had phenotypic properties similar to those of mature human AETII and AETI cells. We used these cells to explore whether lung tissue can be regenerated in vitro. Consistent with an AETII phenotype, we found that up to 97% of cells were positive for surfactant protein C, 95% for mucin-1, 93% for surfactant protein B, and 89% for the epithelial marker CD54. Additionally, exposing induced AETII to a Wnt/β-catenin inhibitor (IWR-1) changed the iPSC-AETII-like phenotype to a predominantly AETI-like phenotype. We found that of induced AET1 cells, more than 90% were positive for type I markers, T1α, and caveolin-1. Acellular lung matrices were prepared from whole rat or human adult lungs treated with decellularization reagents, followed by seeding these matrices with alveolar cells derived from human iPSCs. Under appropriate culture conditions, these progenitor cells adhered to and proliferated within the 3D lung tissue scaffold and displayed markers of differentiated pulmonary epithelium.

Concepts: Gene, Lung, Extracellular matrix, Stem cell, Stem cells, Cell biology, Epithelium, Progenitor cell


BACKGROUND: Adult stem cells have been widely investigated in bioengineering approaches for tissue repair therapy. We evaluated the clinical value and safety of the application of cultured bone marrow-derived allogenic mesenchymal stem cells (MSCs) for treating skin wounds in a canine model. HYPOTHESIS: Topical allogenic MSC transplantation can accelerate the closure of experimental full-thickness cutaneous wounds and attenuate local inflammation. ANIMALS: Adult healthy beagle dogs (n = 10; 3-6 years old; 7.2-13.1 kg) were studied. METHODS: Full-thickness skin wounds were created on the dorsum of healthy beagles, and allogenic MSCs were injected intradermally. The rate of wound closure and the degree of collagen production were analysed histologically using haematoxylin and eosin staining and trichrome staining. The degree of cellular proliferation and angiogenesis was evaluated by immunocytochemistry using proliferating cell nuclear antigen-, vimentin- and α-smooth muscle actin-specific antibodies. Local mRNA expression levels of interleukin-2, interferon-γ, basic fibroblast growth factor and matrix metalloproteinase-2 were evaluated by RT-PCR. RESULTS: Compared with the vehicle-treated wounds, MSC-treated wounds showed more rapid wound closure and increased collagen synthesis, cellular proliferation and angiogenesis. Moreover, MSC-treated wounds showed decreased expression of pro-inflammatory cytokines (interleukin-2 and interferon-γ) and wound healing-related factors (basic fibroblast growth factor and matrix metalloproteinase-2). CONCLUSION AND CLINICAL IMPORTANCE: Topical transplantation of MSCs results in paracrine effects on cellular proliferation and angiogenesis, as well as modulation of local mRNA expression of several factors related to cutaneous wound healing.

Concepts: Wound healing, Collagen, Stem cell, Mesenchymal stem cell, Bone marrow, Stem cells, Cellular differentiation, Fibroblast growth factor


The generation of functional endodermal lineages, such as hepatocytes and pancreatic endocrine cells, from pluripotent stem cells (PSCs) remains a challenge. One strategy to enhance the purity, yield and maturity of endodermal derivatives is to expand endoderm committed stem or progenitor cell populations derived from PSCs before final differentiation. Recent studies have shown that this is in fact a viable option both for expanding pure populations of endodermal cells as well as for generating more mature derivative tissues, as highlighted in the case of pancreatic beta cells.

Concepts: Developmental biology, Stem cell, Stem cells, Cell biology, Pancreas, Progenitor cell, Multipotency, Pluripotency