BMP-4 induces a Smad-dependent apoptotic cell death of mouse embryonic stem cell-derived neural precursors

Bone morphogenetic protein (BMP) signaling determines neuroblastoma cell fate and sensitivity to retinoic acid

Retinoic acid (RA) is a standard-of-care neuroblastoma drug thought to be effective by inducing differentiation. Curiously, RA has little effect on primary human tumors during upfront treatment but can eliminate neuroblastoma cells from the bone marrow during post-chemo consolidation therapy-a discrepancy that has never been explained. To investigate this, we treated a large cohort of neuroblastoma cell lines with RA and observed that the most RA-sensitive cells predominantly undergo apoptosis or senescence, rather than differentiation. We conducted genome-wide CRISPR knockout screens under RA treatment, which identified BMP signaling as controlling the apoptosis/senescence vs differentiation cell fate decision and determining RA's overall potency. We then discovered that BMP signaling activity is markedly higher in neuroblastoma patient samples at bone marrow metastatic sites, providing a plausible explanation for RA's ability to clear neuroblastoma cells specifically from the bone marrow, seemingly mimicking interactions between BMP and RA during normal development.

iPSC-based approach for human hair follicle regeneration

Hair follicles (HFs) are a multifunctional structure involved in physical protection, thermoregulation, sensational detection, and wound healing. Formation and cycling of HFs require dynamic interaction between different cell types of the follicles. Although the processes have been well studied, the generation of human functional HFs with a normal cycling pattern for clinical utilization has yet to be achieved. Recently, human pluripotent stem cells (hPSCs) serve as an unlimited cell source for generating various types of cells including cells of the HFs. In this review, HF morphogenesis and cycling, different cell sources used for HF regeneration, and potential strategies for HF bioengineering using induced pluripotent stem cells (iPSCs) are depicted. Challenges and perspectives toward the therapeutic use of bioengineered HFs for hair loss disorder are also discussed.

Differentiation of pluripotent stem cells for modeling human skin development and potential applications

The skin of mammals is a multilayered and multicellular tissue that forms an environmental barrier with key functions in protection, regulation, and sensation. While animal models have long served to study the basic functions of the skin in vivo, new insights are expected from in vitro models of human skin development. Human pluripotent stem cells (PSCs) have proven to be invaluable tools for studying human development in vitro. To understand the mechanisms regulating human skin homeostasis and injury repair at the molecular level, recent efforts aim to differentiate PSCs towards skin epidermal keratinocytes, dermal fibroblasts, and skin appendages such as hair follicles and sebaceous glands. Here, we present an overview of the literature describing strategies for human PSC differentiation towards the components of skin, with a particular focus on keratinocytes. We highlight fundamental advances in the field employing patient-derived human induced PSCs (iPSCs) and skin organoid generation. Importantly, PSCs allow researchers to model inherited skin diseases in the search for potential treatments. Skin differentiation from human PSCs holds the potential to clarify human skin biology.

Directed differentiation of human pluripotent stem cells into epidermal keratinocyte-like cells

The human pluripotent stem cell (hPSC) differentiation has allowed for the generation of in vitro models to study human diseases in a dish. This protocol describes the generation of keratinocyte-like cells from hPSCs in chemically defined media. Treating hPSCs with retinoic acid and BMP4 induced the generation of keratinocyte progenitors, which further differentiated into mature keratinocytes in the presence of calcium. The keratinocytes generated with this protocol could be used to study keratinocyte biology, drug screening, and skin-related diseases.

For complete details on the use and execution of this protocol, please refer to Ali et al. (2020).

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Protocol for differentiation of pluripotent stem cells into epidermal keratinocytes

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Step-by-step guide for evaluating the keratinocyte differentiation efficiency

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Retinoic acid (RA) and BMP4 induce keratinocyte progenitor differentiation

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Addition of calcium enhances the maturation of epidermal keratinocyte

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

The effects of Bone Morphogenetic Protein 4 on adult neural stem cell proliferation, differentiation and survival in an in vitro model of ischemic stroke

The subventricular zone (SVZ) of the lateral ventricles represents a main region where neural stem cells (NSCs) of the mature central nervous system (CNS) reside. Bone Morphogenetic Proteins (BMPs) are the largest subclass of the transforming growth factor-β (TGF-β) superfamily of ligands. BMP4 is one such member and plays important roles in adult NSC differentiation. However, the exact effects of BMP4 on SVZ adult NSCs in CNS ischemia are still unknown. Using oxygen and glucose deprivation (OGD) as an in vitro model of ischemia, we examined the behavior of adult NSCs. We observed that anoxia resulted in reduced viability of adult NSCs, and that BMP4 treatment clearly rescued apoptotic cell death following anoxia. Furthermore, BMP4 treatment exhibited a strong inhibitory effect on cellular proliferation of the adult NSCs in normoxic conditions. Moreover, such inhibitory effects of BMP4 treatment were also found in OGD conditions, despite the enhanced cellular proliferation of the adult NSCs that was observed under such ischemic conditions. Increased neuronal and astroglial commitment of adult NSCs were found in the OGD conditions, whereas a reduction in differentiated neurons and an increase in differentiated astrocytes were observed following BMP4 treatment. The present data indicate that BMP4 modulates proliferation and differentiation of SVZ-derived adult NSCs and promotes cell survival in the in vitro model of ischemic stroke.

A farewell to phlebotomy-use of placenta-derived drugs Laennec and Porcine for improving hereditary hemochromatosis without phlebotomy: a case report

BACKGROUND

Human hepcidin, produced by hepatocytes, regulates intestinal iron absorption, iron recycling by macrophages, and iron release from hepatic storage. Recent studies indicate that hepcidin deficiency is the underlying cause of the most known form of hereditary hemochromatosis.

CASE PRESENTATION

A 44-year-old Asian man who developed type 2 diabetes mellitus had elevated serum ferritin levels (10,191 ng/mL). Liver biopsy revealed remarkable iron deposition in the hepatocytes and relatively advanced fibrosis (F3). Chromosomal analysis confirmed the presence of transferrin receptor type 2 mutations (c.1100T>G, c.2008_9delAC, hereditary hemochromatosis type 3 analyzed by Kawabata). The patient received intravenous infusions of Laennec (672 mg/day, three times/week) or oral administration with Porcine (3.87 g/day) for 84 months as an alternative to repeated phlebotomy. At the end of the treatment period, serum ferritin level decreased to 428.4 ng/mL (below the baseline level of 536.8 ng/mL). Hemoglobin A1c levels also improved after treatment with the same or lower dose of insulin (8.8% before versus 6.8% after). Plural liver biopsies revealed remarkable improvements in the grade of iron deposition and fibrosis (F3 before versus F1 after) of the liver tissue.

CONCLUSION

The discovery of hepcidin and its role in iron metabolism could lead to novel therapies for hereditary hemochromatosis. Laennec (parenteral) and Porcine (oral), which act as hepcidin inducers, actually improved iron overload in this hereditary hemochromatosis patient, without utilizing sequential phlebotomy. This suggests the possibility of not only improving the prognosis of hereditary hemochromatosis (types 1, 2, and 3) but also ameliorating complications, such as type 2 diabetes, liver fibrosis, and hypogonadism. Laennec and Porcine can completely replace continuous venesection in patients with venesection and may improve other iron-overloading disorders caused by hepcidin deficiency.

ASB2 is a novel E3 ligase of SMAD9 required for cardiogenesis

Cardiogenesis requires the orchestrated spatiotemporal tuning of BMP signalling upon the balance between induction and counter-acting suppression of the differentiation of the cardiac tissue. SMADs are key intracellular transducers and the selective degradation of SMADs by the ubiquitin-proteasome system is pivotal in the spatiotemporal tuning of BMP signalling. However, among three SMADs for BMP signalling, SMAD1/5/9, only the specific E3 ligase of SMAD9 remains poorly investigated. Here, we report for the first time that SMAD9, but not the other SMADs, is ubiquitylated by the E3 ligase ASB2 and targeted for proteasomal degradation. ASB2, as well as Smad9, is conserved among vertebrates. ASB2 expression was specific to the cardiac region from the very early stage of cardiac differentiation in embryogenesis of mouse. Knockdown of Asb2 in zebrafish resulted in a thinned ventricular wall and dilated ventricle, which were rescued by simultaneous knockdown of Smad9. Abundant Smad9 protein leads to dysregulated cardiac differentiation through a mechanism involving Tbx2, and the BMP signal conducted by Smad9 was downregulated under quantitative suppression of Smad9 by Asb2. Our findings demonstrate that ASB2 is the E3 ligase of SMAD9 and plays a pivotal role in cardiogenesis through regulating BMP signalling.

Human pluripotent stem cells: An alternative for 3D in vitro modelling of skin disease

To effectively study the skin and its pathology, various platforms have been used to date, with in vitro 3D skin models being considered the future gold standard. These models have generally been engineered from primary cell lines. However, their short life span leading to the use of various donors, imposes issues with genetic variation. Human pluripotent stem cell (hPSC)-technology holds great prospects as an alternative to the use of primary cell lines to study the pathophysiology of human skin diseases. This is due to their potential to generate an unlimited number of genetically identical skin models that closely mimic the complexity of in vivo human skin. During the past decade, researchers have therefore started to use human embryonic and induced pluripotent stem cells (hESC/iPSC) to derive skin resident-like cells and components. These have subsequently been used to engineer hPSC-derived 3D skin models. In this review, we focus on the advantages, recent developments, and future perspectives in using hPSCs as an alternative cell source for modelling human skin diseases in vitro.

Reprogramming of Keratinocytes as Donor or Target Cells Holds Great Promise for Cell Therapy and Regenerative Medicine

One of the most crucial branches of regenerative medicine is cell therapy, in which cellular material is injected into the patient to initiate the regenerative process. Cells obtained by reprogramming of the patient's own cells offer ethical and clinical advantages could provide a new source of material for therapeutic applications. Studies to date have shown that only a subset of differentiated cell types can be reprogrammed. Among these, keratinocytes, which are the most abundant proliferating cell type in the epidermis, have gained increasing attention as both donor and target cells for reprogramming and have become a new focus of regenerative medicine. As target cells for the treatment of skin defects, keratinocytes can be differentiated or reprogrammed from embryonic stem cells, induced pluripotent stem cells, fibroblasts, adipose tissue stem cells, and mesenchymal cells. As donor cells, keratinocytes can be reprogrammed or direct reprogrammed into a number of cell types, including induced pluripotent stem cells, neural cells, and Schwann cells. In this review, we discuss recent advances in keratinocyte reprogramming, focusing on the induction methods, potential molecular mechanisms, conversion efficiency, and safety for clinical applications. Graphical Abstract KCs as target cells can be reprogrammed or differentiated from fibroblasts, iPSCs, ATSCs, and mesenchymal cells. And as donor cells, KCs can be reprogrammed or directly reprogrammded into iPSCs, neural cells, Schwann cells, and epidermal stem cells.

Multi-platform NMR Study of Pluripotent Stem Cells Unveils Complementary Metabolic Signatures towards Differentiation

Stem cells, poised to revolutionize current medicine, stand as major workhorses for monitoring changes in cell fate. Characterizing metabolic phenotypes is key to monitor in differentiating cells transcriptional and epigenetic shifts at a functional level and provides a non-genetic means to control cell specification. Expanding the arsenal of analytical tools for metabolic profiling of cell differentiation is therefore of importance. Here, we describe the metabolome of whole pluripotent stem cells (PSCs) using high‐resolution magic angle spinning (HR-MAS), a non-destructive approach for Nuclear Magnetic Resonance (NMR) analysis. The integrated ¹H NMR analysis results in detection of metabolites of various groups, including energy metabolites, amino acids, choline derivatives and short chain fatty acids. It unveils new metabolites that discriminate PSCs from differentiated counterparts and directly measures substrates and co-factors of histone modifying enzymes, suggesting that NMR stands as a strategic technique for deciphering metabolic regulations of histone post-translational modifications. HR-MAS NMR analysis of whole PSCs complements the much used solution NMR of cell extracts. Altogether, our multi-platform NMR investigation provides a consolidated picture of PSC metabolic signatures and of metabolic pathways involved in differentiation.

Bioactive Molecules for Skin Repair and Regeneration: Progress and Perspectives

Skin regeneration is a vexing problem in the field of regenerative medicine. A bioactive molecule-based strategy has been frequently used in skin wound healing in recent years. Bioactive molecules are practical tools for regulating cellular processes and have been applied to control cellular differentiation, dedifferentiation, and reprogramming. In this review, we focus on recent progress in the use of bioactive molecules in skin regenerative medicine, by which desired cell types can be generated in vitro for cell therapy and conventional therapeutics can be developed to repair and regenerate skin in vivo through activation of the endogenous repairing potential. We further prospect that the bioactive molecule-base method might be one of the promising strategies to achieve in situ skin regeneration in the future.

Layered double hydroxide eliminate embryotoxicity of chemotherapeutic drug through BMP-SMAD signaling pathway

Recent studies indicate that exogenous chemotherapy agents can cross the placenta barrier and cause fetal toxicity, while there exists barely alternative therapy for pregnant cancer patients. Here, we show a robust protective effect of layered double hydroxide (LDH) against etoposide (VP16) induced in vitro mouse embryonic stem cells (mESCs) toxicity and in vivo embryo developmental disorders. The nano-composite system (L-V) abrogated the original VP16 generated mitochondrial mediated mESCs toxicity totally, surprisingly maintained the pluripotency without leukemia inhibitory factor (LIF) and prevented the down-regulation of ectoderm marker expression during spontaneous embryoid bodies differentiation. Fetal growth retardation, the related placenta and skeletal structural abnormalities and long-term toxicity in the offspring were generated when pregnant mice exposed to VP16, while these detrimental effects were abolished when substituted with L-V. The different uterine drug accumulation of VP16 and L-V contributed to partly cause for the functional variation. And further transcriptome analysis confirmed developmental related BMP4-SMAD6 signaling pathway is of crucial importance. Our study revealed the devastating effects of VP16 on embryonic development and the toxicity-relieve method using nano-carrier system, which will provide important guidance for clinical application of LDH as alternative therapeutic system with minimal side effects for pregnant women diagnosed with cancer.

Death-Associated Protein Kinase 1 Phosphorylation in Neuronal Cell Death and Neurodegenerative Disease

Regulated neuronal cell death plays an essential role in biological processes in normal physiology, including the development of the nervous system. However, the deregulation of neuronal apoptosis by various factors leads to neurodegenerative diseases such as ischemic stroke and Alzheimer’s disease (AD). Death-associated protein kinase 1 (DAPK1) is a calcium/calmodulin (Ca²⁺/CaM)-dependent serine/threonine (Ser/Thr) protein kinase that activates death signaling and regulates apoptotic neuronal cell death. Although DAPK1 is tightly regulated under physiological conditions, DAPK1 deregulation in the brain contributes to the development of neurological disorders. In this review, we describe the molecular mechanisms of DAPK1 regulation in neurons under various stresses. We also discuss the role of DAPK1 signaling in the phosphorylation-dependent and phosphorylation-independent regulation of its downstream targets in neuronal cell death. Moreover, we focus on the major impact of DAPK1 deregulation on the progression of neurodegenerative diseases and the development of drugs targeting DAPK1 for the treatment of diseases. Therefore, this review summarizes the DAPK1 phosphorylation signaling pathways in various neurodegenerative diseases.

Feasibility of repairing full-thickness skin defects by iPSC-derived epithelial stem cells seeded on a human acellular amniotic membrane

Background

Induced pluripotent stem cells (iPSCs) can generate epithelial stem cells (EpSCs) as seed cells for skin substitutes to repair skin defects. Here, we investigated the effects of a human acellular amniotic membrane (hAAM) combined with iPSC-derived CD200⁺/ITGA6⁺ EpSCs as a skin substitute on repairing skin defects in nude mice.

Methods

Human urinary cells isolated from a healthy donor were reprogrammed into iPSCs and then induced into CD200⁺/ITGA6⁺ epithelial stem cells. Immunocytochemistry and RT-PCR were used to examine the characteristics of the induced epithelial stem cells. iPSC-derived EpSCs were cultured on a hAAM, and cytocompatibility of the composite was analyzed by CCK8 assays and scanning electron microscopy. Then, hAAMs combined with iPSC-derived EpSCs were transplanted onto skin defects of mice. The effects of this composite on skin repair were evaluated by immunohistochemistry.

Results

The results showed that CD200⁺/ITGA6⁺ epithelial stem cells induced from iPSCs displayed the phenotypes of hair follicle stem cells. After seeding on the hAAM, iPSC-derived epithelial stem cells had the ability to proliferate. After transplantation, CD200⁺/ITGA6⁺ epithelial stem cells on the hAAM promoted the construction of hair follicles and interfollicular epidermis.

Conclusions

These results indicated that transplantation of a hAAM combined with iPS-derived EpSCs is feasible to reconstruct skin and skin appendages, and may be a substantial reference for iPSC-based therapy for skin defects.

DNA Damage Response After Ionizing Radiation Exposure in Skin Keratinocytes Derived from Human-Induced Pluripotent Stem Cells

PURPOSE

Epidermal cells are positioned on the body surface and thus risk being exposed to genotoxic stress, including ionizing radiation (IR), ultraviolet rays, and chemical compounds. The biological effect of IR on the skin tissue is a significant problem for medical applications such as radiation therapy. Keratinocyte stem cells and progenitors are at risk for IR-dependent tumorigenesis during radiation therapy for cancer treatment. To elucidate the molecular mechanism of genome stability in epidermal cells, we derived skin keratinocytes from human-induced pluripotent stem cells (iPSCs) and analyzed their DNA damage response (DDR).

METHODS AND MATERIALS

Skin keratinocytes were derived from iPSCs and designated as first- (P1), second- (P2), and third- (P3) passage cells to compare the differentiation states of DDR. After 2 Gy gamma-ray exposure, cells were immunostained with DNA double-strand break markers γ-H2AX/53BP1 and cell senescence markers p16/p21 for DDR analysis. DDR protein expression level, cell survival, and apoptosis were analyzed by western blotting, WST-8 assay and TUNEL assay, respectively. DDR of constructed 3D organoid modeling was also analyzed.

RESULTS

P1, P2, and P3 keratinocytes were characterized with keratinocyte markers keratin 14 and p63 using immunofluorescence, and all cells were positive to both markers. Derived keratinocytes showed high expression of integrin α6 and CD71 (real-time (qRT)-PCR ratio: iPSCs: integrin α6: 1.12, CD71: 1.25, P1: integrin α6: 7.80, CD71: 0.43, P2: integrin α6: 5.53, CD71: 0.48), suggesting that P1 and P2 keratinocytes have potential as keratinocyte progenitors. Meanwhile, P3 keratinocytes showed low expression of integrin α6 and CD71 (qRT-PCR ratio: P3: integrin α6: 0.55, CD71: 0.10), suggesting differentiated keratinocytes. After IR exposure, the P1 and P2 keratinocytes showed an increase in DNA repair activity by a γ-H2AX/53BP1 focus assay (P1: γ-H2AX: 28.0%, 53BP1: 17.0%, P2: γ-H2AX: 37.7%, 53BP1: 28.3%) but not in P3 keratinocytes (P3: γ-H2AX: 74.7%, 53BP1: 63.7%) compared with iPSCs (γ-H2AX: 57.0%, 53BP1: 55.0%). Furthermore, in derived keratinocytes, expression of the cellular senescence markers p16 and p21 were increased compared with iPSCs (P16: non irradiated, iPSCs: 0%, P1: 12.5%, P2: 14.5%, P3: 29.7%, IR, iPSCs: 0%, P1: 19.5%, P2: 34.8%, P3: 64.5%). DDR protein expression, cellular sensitivity, and apoptosis activity decreased in derived keratinocytes compared with iPSCs.

CONCLUSIONS

We have demonstrated the derivation of keratinocytes from iPSCs and their characterization of differentiated states and DDR. Derived keratinocytes showed progenitors like character as a result of DDR. These results suggest that derived keratinocytes are useful tools for analyzing the effects of IR, such as DDR on the skin tissue from radiation therapy for cancer.

Inhibition of neogenin promotes neuronal survival and improved behavior recovery after spinal cord injury

Following spinal cord trauma, axonal regeneration in the mammalian spinal cord does not occur and functional recovery may be further impeded by retrograde neuronal death. By contrast, lampreys recover after spinal cord injury (SCI) and axons re-connected to their targets in spinal cord. However, the identified reticulospinal (RS) neurons located in the lamprey brain differ in their regenerative capacities - some are good regenerators, and others are bad regenerators - despite the fact that they have analogous projection pathways. Previously, we reported that axonal guidance receptor Neogenin involved in regulation of axonal regeneration after SCI and downregulation of Neogenin synthesis by morpholino oligonucleotides (MO) enhanced the regeneration of RS neurons. Incidentally, the bad regenerating RS neurons often undergo a late retrograde apoptosis after SCI. Here we report that, after SCI, expression of RGMa mRNA was upregulated around the transection site, while its receptor Neogenin continued to be synthesized almost inclusively in the "bad-regenerating" RS neurons. Inhibition of Neogenin by MO prohibited activation of caspases and improved the survival of RS neurons at 10 weeks after SCI. These data provide new evidence in vivo that Neogenin is involved in retrograde neuronal death and failure of axonal regeneration after SCI.

A novel method to reconstruct epithelial tissue using high-purity keratinocyte lineage cells induced from human embryonic stem cells

The treatment of oral mucosa defect such as autologous oral mucosa caused by resection of oral mucosa carcinoma is still not ideal in clinical practice. However, Tissue engineering gives us the possibility to solve this problem. As we all know, Human embryonic stem cells (hESCs) have the ability to give rise to various cell types. We can take advantage of the totipotency of human embryonic stem cells to acquire keratinocytes. Directing the epithelial differentiation of hESCs can provide seed cells for the construction of epithelium tissue by tissue engineering. But, how to get high purity keratinocytes by induced stem cells then Applied to tissue engineering mucosa is an important challenge. We described a novel method to directly induce hESCs to differentiate into keratinocytes. Retinoic acid, ascorbic acid, and bone morphogenetic protein induced hESCs to differentiate into cells that highly expressed cytokeratin (CK)14. Our findings suggest that the retinoic acid, ascorbic acid and bone morphogenetic proteins induced hESCs to form high purity keratinocyte cell populations. In addition, we found that the highly pure keratinocyte populations reconstructed artificial tissue resembling epithelial tissue when inoculated in vitro on a biological scaffold.

Conditional deletion of platelet derived growth factor receptor alpha (Pdgfra) in urorectal mesenchyme causes mesenchyme apoptosis and urorectal developmental anomalies in mice

In mammals, urorectal development starts at early embryonic stage, defective urorectal development results in anorectal malformations, which are common congenital developmental defects of the anus and the urethra in newborns. The etiology and embryology of the defects are still largely unknown. Platelet-derived growth factor receptor alpha (Pdgfra) is a cell surface receptor tyrosine kinase, upon binding to its ligands (Pdgfa-d), mediates intracellular signaling and regulates embryonic development. The expression of Pdgfra is tightly regulated in the developing urorectal mesenchyme, and its dysregulation is associated with urorectal defects in animals with urorectal defects. Knockout of Pdgfra induces early embryo lethality which precludes investigation of Pdgfra in urorectal development. To address the temporal requirement of Pdgfra in urorectal development, we conditionally deleted Pdgfra in Pdgfra-expressing tissues using a tamoxifen inducible Cre-loxP approach in mice, examined the urorectal development in Pdgfra conditional knockout (Pdgfra-cKO) embryos. We showed that conditional deletion of Pdgfra in Pdgfra-expressing tissues at E10-E11 caused cloaca septation defect, anteriorly displaced anus, defective urogenital folds development and abnormal urethra tubularization in both male and female mice. Furthermore, we showed that Pdgfra was required for the survival of urorectal mesenchyme, deletion of Pdgfra caused apoptosis in the peri-cloacal, the peri-urethra and the urorectal septum mesenchyme of Pdgfra-cKO mutants, associated with an induction of p53, Ndrg1 and activation of caspase-3 in Pdgfra-cKO embryos. In conclusion, Pdgfra is required for the development and survival of the urorectal mesenchyme in embryo, dysregulated Pdgfra signaling induced urorectal defects in mice resembling human congenital diseases of anorectal malformations and hypospadias. Perturbation of PDGFRA signaling may contribute to anorectal malformations and hypospadias in human.

Mitochondria structural reorganization during mouse embryonic stem cell derivation

Mouse embryonic stem (ES) cells are widely used in developmental biology and transgenic research. Despite numerous studies, ultrastructural reorganization of inner cell mass (ICM) cells during in vitro culture has not yet been described in detail. Here, we for the first time performed comparative morphological and morphometric analyses of three ES cell lines during their derivation in vitro. We compared morphological characteristics of blastocyst ICM cells at 3.5 and 4.5 days post coitum on feeder cells (day 6, passage 0) with those of ES cells at different passages (day 19, passage 2; day 25, passage 4; and passage 15). At passage 0, there were 23-36% of ES-like cells with various values of the medium cross-sectional area and nucleocytoplasmic parameters, 55% of fibroblast-like (probably trophoblast derivatives), and ~ 19% of dying cells. ES-like cells at passage 0 contained autolysosomes and enlarged mitochondria with reduced numerical density per cell. There were three types of mitochondria that differed in matrix density and cristae width. For the first time, we revealed cells that had two and sometimes three morphologically distinct mitochondria types in the cytoplasm. At passage 2, there were mostly ES cells with a high nucleocytoplasmic ratio and a cytoplasm depleted of organelles. At passage 4, ES cell morphology and morphometric parameters were mostly stable with little heterogeneity. According to our data, cellular structures of ICM cells undergo destabilization during derivation of an ES cell line with subsequent reorganization into the structures typical for ES cells. On the basis of ultrastructural analysis of mitochondria, we believe that the functional activity of these organelles changes during early stages of ES cell formation from the ICM.

An adjustment in BMP4 function represents a treatment for diabetic nephropathy and podocyte injury

Podocyte injury has been proposed to play an important role in diabetic nephropathy; however, its pathological mechanism remains unclear. We have shown that bone morphogenetic protein 4 (BMP4) signaling leads to the glomerular changes characteristic of this disorder. To analyze the molecular mechanism of podocyte injury, the effect of BMP4 was investigated using streptozotocin (STZ)-induced, Bmp4 heterozygous knockout (Bmp4+/−) and podocyte-specific Bmp4 knockout mice. Mice with STZ-induced diabetes exhibited glomerular matrix hyperplasia and decreased numbers of podocyte nucleus-specific WT1-positive cells. The number of podocytes and proteinuria were improved in both diabetic Bmp4 knockout mouse models compared to the effects observed in the control mice. The effect of BMP4 overexpression on Bmp4-induced or podocyte-specific transgenic mice was examined. Tamoxifen-induced Bmp4-overexpressing mice exhibited mesangial matrix expansion and decreased numbers of WT1-positive cells. Podocyte-specific Bmp4-overexpressing mice displayed increased kidney BMP4 expression and mesangial matrix expansion but decreased nephrin expression and numbers of WT1-positive cells. Both lines of Bmp4-overexpressing mice exhibited increased albuminuria. In cultured podocytes, BMP4 increased phospho-p38 levels. BMP4 decreased nephrin expression but increased cleaved caspase-3 levels. p38 suppression inhibited caspase-3 activation. Apoptosis was confirmed in STZ-diabetic glomeruli and Bmp4-overexpressing mice. Bmp4 +/− mice with diabetes displayed reduced apoptosis. Based on these data, the BMP4 signaling pathway plays important roles in the development of both podocyte injury and mesangial matrix expansion in diabetic nephropathy.

Intracellular amyloid beta expression leads to dysregulation of the mitogen-activated protein kinase and bone morphogenetic protein-2 signaling axis

Alzheimer's disease (AD) is a neurodegenerative syndrome classically depicted by the parenchymal accumulation of extracellular amyloid beta plaques. However, recent findings suggest intraneuronal amyloid beta (iAβ1-42) accumulation precedes extracellular deposition. Furthermore, the pathologic increase in iAβ1-42 has been implicated in dysregulation of cellular mechanisms critically important in axonal transport. Owing to neuronal cell polarity, retrograde and anterograde axonal transport are essential trafficking mechanism necessary to convey membrane bound neurotransmitters, neurotrophins, and endosomes between soma and synaptic interfaces. Although iAβ1-42 disruption of axonal transport has been implicated in dysregulation of neuronal synaptic transmission, the role of iAβ1-42 and its influence on signal transduction involving the mitogen-activated protein kinase (MAPK) and morphogenetic signaling axis are unknown. Our biochemical characterization of intracellular amyloid beta accumulation on MAPK and morphogenetic signaling have revealed increased iAβ1-42 expression leads to significant reduction in ERK 1/2 phosphorylation and increased bone morphogenetic protein 2 dependent Smad 1/5/8 phosphorylation. Furthermore, rescue of iAβ1-42 mediated attenuation of MAPK signaling can be accomplished with the small molecule PLX4032 as a downstream enhancer of the MAPK pathway. Consequently, our observations regarding the dysregulation of these gatekeepers of neuronal viability may have important implications in understanding the iAβ1-42 mediated effects observed in AD.

Differences in the Activity of Endogenous Bone Morphogenetic Protein Signaling Impact on the Ability of Induced Pluripotent Stem Cells to Differentiate to Corneal Epithelial-Like Cells

Cornea is a clear outermost layer of the eye which enables transmission of light onto the retina. The transparent corneal epithelium is regenerated by limbal stem cells (LSCs), whose loss/dysfunction results in LSCs deficiency (LSCD). Ex vivo expansion of autologous LSCs obtained from patient's healthy eye followed by transplantation onto the LSCs damaged/deficient eye, has provided a successful treatment for unilateral LSCD. However, this is not applicable to patient with total bilateral LSCD, where LSCs are lost/damaged from both eyes. We investigated the potential of human induced pluripotent stem cell (hiPSC) to differentiate into corneal epithelial‐like cells as a source of autologous stem cell treatment for patients with total bilateral LSCD. Our study showed that combined addition of bone morphogenetic protein 4 (BMP4), all trans‐retinoic acid and epidermal growth factor for the first 9 days of differentiation followed by cell‐replating on collagen‐IV‐coated surfaces with a corneal‐specific‐epithelial cell media for an additional 11 days, resulted in step wise differentiation of human embryonic stem cells (hESC) to corneal epithelial progenitors and mature corneal epithelial‐like cells. We observed differences in the ability of hiPSC lines to undergo differentiation to corneal epithelial‐like cells which were dependent on the level of endogenous BMP signaling and could be restored via the activation of this signaling pathway by a specific transforming growth factor β inhibitor (SB431542). Together our data reveal a differential ability of hiPSC lines to generate corneal epithelial cells which is underlined by the activity of endogenous BMP signaling pathway. Stem Cells2018;36:337–348

Decrease of FSTL1-BMP4-Smad signaling predicts poor prognosis in lung adenocarcinoma but not in squamous cell carcinoma

Follistatin-related protein 1 (FSTL1) plays a critical role in lung development through regulating BMP4-p-Smad1/5/8-Smad4 pathway. Regarding that many developmental pathways in embryogenesis are dysregulated in cancer, we aim to unravel the role of FSTL1-BMP4-Smad pathway in lung cancer. Our results showed low FSTL1 immunoexpression was significantly correlated with poor prognosis while patients with low BMP4 or low Smad4 immunoexpression showed a trend toward poor prognosis. When stratified by different histological types, low FSTL1, BMP4, and Smad4 expression retained their trends in predicting poor prognosis in lung adenocarcinoma (LUAD) but not in lung squamous cell carcinoma (SCC). Low FSTL1, BMP4, and Smad4 expression were more frequently observed in LUAD patients with smoking history. To determine smoking effect on FSTL1, normal cell BEAS2B and lung cancer cell lines was treated with nicotine and the results showed nicotine increased the proliferation of these cells. Interestingly, FSTL1 attenuated nicotine-induced BEAS2B and lung cancer cell line proliferation. Altogether, low FSTL1, BMP4, and Smad4 expression significantly correlated with poor prognosis in LUAD but not in SCC. Frequent decrease of FSTL1 expression in smokers LUAD further indicates its importance and therapeutic potential for lung cancer patients with specific subtypes. FSTL1 may prevent nicotine-induced lung cancer cell proliferation.

Direct conversion of mouse embryonic fibroblasts into functional keratinocytes through transient expression of pluripotency-related genes

The insufficient ability of specialized cells such as neurons, cardiac myocytes, and epidermal cells to regenerate after tissue damage poses a great challenge to treat devastating injuries and ailments. Recent studies demonstrated that a diverse array of cell types can be directly derived from embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), or somatic cells by combinations of specific factors. The use of iPSCs and direct somatic cell fate conversion, or transdifferentiation, holds great promise for regenerative medicine as these techniques may circumvent obstacles related to immunological rejection and ethical considerations. However, producing iPSC-derived keratinocytes requires a lengthy two-step process of initially generating iPSCs and subsequently differentiating into skin cells, thereby elevating the risk of cellular damage accumulation and tumor formation. In this study, we describe the reprogramming of mouse embryonic fibroblasts into functional keratinocytes via the transient expression of pluripotency factors coupled with directed differentiation. The isolation of an iPSC intermediate is dispensable when using this method. Cells derived with this approach, termed induced keratinocytes (iKCs), morphologically resemble primary keratinocytes. Furthermore they express keratinocyte-specific markers, downregulate mesenchymal markers as well as the pluripotency factors Oct4, Sox2, and Klf4, and they show important functional characteristics of primary keratinocytes. iKCs can be further differentiated by high calcium administration in vitro and are capable of regenerating a fully stratified epidermis in vivo. Efficient conversion of somatic cells into keratinocytes could have important implications for studying genetic skin diseases and designing regenerative therapies to ameliorate devastating skin conditions.

Amniotic fluid stem cells provide considerable advantages in epidermal regeneration: B7H4 creates a moderate inflammation microenvironment to promote wound repair

The current treatments for severe skin injury all involve skin grafting. However, there is a worldwide shortage of donor skin tissue. In this study, we examined the advantages of using human amniotic fluid stem (hAFS) cells in skin wound healing. In vitro, hAFS cells differentiate into keratinocytes (termed hAFS-K). Like keratinocytes, hAFS-K cells express the markers K5, K14, K10 and involucrin; display typical cellular structure, including a tonofibril-rich cytoplasm; and construct a completely pluristratified epithelium in 3D culture. In vivo, in a mouse excisional wound model, GFP-positive hAFS cells participate in wound repair. Co-localization of GFP/K14 and GFP/K10 in the repaired epidermis demonstrated that hAFS cells can differentiate into keratinocytes. Real-time PCR results confirmed that hAFS cells can initiate and promote early-stage repair of skin damage. During wound repair, hAFS cells did not directly secrete repair-related factors, such as bFGF, VEGF, CXCL12, TGF-β1 and KGF, and provided a moderate inflammation reaction with lower expression of IL-1β, IL-6, TNF-α, Cox2 and Mac3. In hAFS cells, the negative co-stimulatory molecule B7H4 regulates low immunogenicity, which can provide a modest inflammatory reaction microenvironment for wound repair. Furthermore, with their uniquely high proliferation rate, hAFS cells offer a promising alternative for epidermal regeneration.

Differentiation of equine induced pluripotent stem cells into a keratinocyte lineage

REASONS FOR PERFORMING STUDY

Skin trauma in horses often leads to the development of chronic nonhealing wounds that lack a keratinocyte cover, vital for healing. Reports in mouse and man confirm the possibility of generating functional keratinocytes from induced pluripotent stem cells (iPSC), thus presenting myriad potential applications for wound management or treatment of skin disease. Similarly, differentiation of equine iPSC (eiPSC) into a keratinocyte lineage should provide opportunities for the advancement of veterinary regenerative medicine.

OBJECTIVES

The purpose of this study was to develop an efficient method for the differentiation of eiPSC into a keratinocyte lineage. It was hypothesised that eiPSC can form differentiated keratinocytes (eiPSC-KC) comparable with primary equine keratinocytes (PEK) in their morphological and functional characteristics.

STUDY DESIGN

Experimental in vitro study.

METHODS

Equine iPSC established using a nonviral system were treated for 30 days with retinoic acid and bone morphogenetic protein-4 to induce directed differentiation into iPSC-KC. Temporospatial gene and protein expression by eiPSC-KC was measured at weekly intervals of differentiation and in response to calcium switch. Proliferative and migratory capacities of eiPSC-KC were compared with those of PEK.

RESULTS

Equine iPSC, upon directed differentiation, showed loss of pluripotency genes and progressive increase in pancytokeratin expression indicating ectodermal specification into keratinocytes. High differentiation efficiency was achieved, with 82.5% of eiPSC expressing keratin 14, a marker of epidermal-specific basal stem cells, after 30 days of directed differentiation. Moreover, the proliferative capacity of eiPSC-KC was superior, while the migratory capacity (measured as the ability to epithelise in vitro wounds) was comparable with that of PEK.

CONCLUSIONS

This proof of concept study suggests that eiPSC can successfully be differentiated into equine keratinocytes (eiPSC-KC) with features that are promising to the development of a stem cell-based skin construct, with the potential to regenerate lost or damaged skin.

Neural differentiation from embryonic stem cells in vitro: An overview of the signaling pathways

Neurons derived from embryonic stem cells (ESCs) have gained great merit in both basic research and regenerative medicine. Here we review and summarize the signaling pathways that have been reported to be involved in the neuronal differentiation of ESCs, particularly those associated with in vitro differentiation. The inducers and pathways explored include retinoic acid, Wnt/β-catenin, transforming growth factor/bone morphogenetic protein, Notch, fibroblast growth factor, cytokine, Hedgehog, c-Jun N-terminal kinase/mitogen-activated protein kinase and others. Some other miscellaneous molecular factors that have been reported in the literature are also summarized and discussed. These include calcium, calcium receptor, calcineurin, estrogen receptor, Hox protein, ceramide, glycosaminioglycan, ginsenoside Rg1, opioids, two pore channel 2, nitric oxide, chemically defined medium, cell-cell interactions, and physical stimuli. The interaction or crosstalk between these signaling pathways and factors will be explored. Elucidating these signals in detail should make a significant contribution to future progress in stem cell biology and allow, for example, better comparisons to be made between differentiation in vivo and in vitro. Of equal importance, a comprehensive understanding of the pathways that are involved in the development of neurons from ESCs in vitro will also accelerate their application as part of translational medicine.

Cell death in development: Signaling pathways and core mechanisms

Programmed cell death eliminates unneeded and dangerous cells in a timely and effective manner during development. In this review, we examine the role cell death plays during development in worms, flies and mammals. We discuss signaling pathways that regulate developmental cell death, and describe how they communicate with the core cell death pathways. In most organisms, the majority of developmental cell death is seen in the nervous system. Therefore we focus on what is known about the regulation of developmental cell death in this tissue. Understanding how the cell death is regulated during development may provide insight into how this process can be manipulated in the treatment of disease.

Derivation of keratinocytes from chicken embryonic stem cells: establishment and characterization of differentiated proliferative cell populations

A common challenge in avian cell biology is the generation of differentiated cell-lines, especially in the keratinocyte lineage. Only a few avian cell-lines are available and very few of them show an interesting differentiation profile. During the last decade, mammalian embryonic stem cell-lines were shown to differentiate into almost all lineages, including keratinocytes. Although chicken embryonic stem cells had been obtained in the 1990s, few differentiation studies toward the ectodermal lineage were reported. Consequently, we explored the differentiation of chicken embryonic stem cells toward the keratinocyte lineage by using a combination of stromal induction, ascorbic acid, BMP4 and chicken serum. During the induction period, we observed a downregulation of pluripotency markers and an upregulation of epidermal markers. Three homogenous cell populations were derived, which were morphologically similar to chicken primary keratinocytes, displaying intracellular lipid droplets in almost every pavimentous cell. These cells could be serially passaged without alteration of their morphology and showed gene and protein expression profiles of epidermal markers similar to chicken primary keratinocytes. These cells represent an alternative to the isolation of chicken primary keratinocytes, being less cumbersome to handle and reducing the number of experimental animals used for the preparation of primary cells.

miR-23a, miR-24 and miR-27a protect differentiating ESCs from BMP4-induced apoptosis

Numerous studies have indicated that BMP4 signaling is involved in the regulation of the early steps of development. In mouse embryonic stem cells (ESCs), BMP4 is crucial to sustain pluripotency and blocks differentiation towards neural fate. Here, through a systematic analysis of miRNAs in ESCs, we establish that BMP4 signaling regulates miR-23a, 27a and 24-2, through the recruitment of phospho-Smads at the promoter of the gene encoding this miRNA cluster. Suppression of miR-23a/b, 27a/b and 24 does not affect self-renewal or pluripotency, but induces an evident change of ESC differentiation, with a significant increase of the cells undergoing apoptosis after the transition from ESCs to epiblast stem cells (EpiSCs). BMP4 has been previously reported to cause apoptosis during ESC differentiation. By blocking BMP4 signaling, we completely prevent the apoptosis induced by suppression of the miRs. This suggests that the effects of miR suppression are the result of enhanced BMP4 signaling. This hypothesis is further supported by the observation that Smad5, the transcription factor downstream of the BMP4 receptor, is targeted by the miRNAs of the 23a and 23b clusters. Altogether, our results highlight the existence of a regulatory loop, involving Smad5 and the miR-23a clusters, that modulates the apoptotic response of ESCs to BMP4.

Epidermal development in mammals: key regulators, signals from beneath, and stem cells

Epidermis is one of the best-studied tissues in mammals that contain types of stem cells. Outstanding works in recent years have shed great light on behaviors of different epidermal stem cell populations in the homeostasis and regeneration of the epidermis as well as hair follicles. Also, the molecular mechanisms governing these stem cells are being elucidated, from genetic to epigenetic levels. Compared with the explicit knowledge about adult skin, embryonic development of the epidermis, especially the early period, still needs exploration. Furthermore, stem cells in the embryonic epidermis are largely unstudied or ambiguously depicted. In this review, we will summarize and discuss the process of embryonic epidermal development, with focuses on some key molecular regulators and the role of the sub-epidermal mesenchyme. We will also try to trace adult epidermal stem cell populations back to embryonic development. In addition, we will comment on in vitro derivation of epidermal lineages from ES cells and iPS cells.

The multifaceted effects of agmatine on functional recovery after spinal cord injury through Modulations of BMP-2/4/7 expressions in neurons and glial cells

Presently, few treatments for spinal cord injury (SCI) are available and none have facilitated neural regeneration and/or significant functional improvement. Agmatine (Agm), a guanidinium compound formed from decarboxylation of L-arginine by arginine decarboxylase, is a neurotransmitter/neuromodulator and been reported to exert neuroprotective effects in central nervous system injury models including SCI. The purpose of this study was to demonstrate the multifaceted effects of Agm on functional recovery and remyelinating events following SCI. Compression SCI in mice was produced by placing a 15 g/mm² weight for 1 min at thoracic vertebra (Th) 9 segment. Mice that received an intraperitoneal (i.p.) injection of Agm (100 mg/kg/day) within 1 hour after SCI until 35 days showed improvement in locomotor recovery and bladder function. Emphasis was made on the analysis of remyelination events, neuronal cell preservation and ablation of glial scar area following SCI. Agm treatment significantly inhibited the demyelination events, neuronal loss and glial scar around the lesion site. In light of recent findings that expressions of bone morphogenetic proteins (BMPs) are modulated in the neuronal and glial cell population after SCI, we hypothesized whether Agm could modulate BMP- 2/4/7 expressions in neurons, astrocytes, oligodendrocytes and play key role in promoting the neuronal and glial cell survival in the injured spinal cord. The results from computer assisted stereological toolbox analysis (CAST) demonstrate that Agm treatment dramatically increased BMP- 2/7 expressions in neurons and oligodendrocytes. On the other hand, BMP- 4 expressions were significantly decreased in astrocytes and oligodendrocytes around the lesion site. Together, our results reveal that Agm treatment improved neurological and histological outcomes, induced oligodendrogenesis, protected neurons, and decreased glial scar formation through modulating the BMP- 2/4/7 expressions following SCI.

Analysis of transferred keratinocyte-like cells derived from mouse embryonic stem cells on experimental surgical skin wounds of mouse

Autologous/allogenic skin grafts constituted from differentiated adult or embryonic stem cells can be used in treatment of skin disorders. In our study we aimed to differentiate keratinocytes from mouse embryonic stem cells and the transfer of viable keratinocyte-like cells to a model of surgical skin wound of mouse. Embryoid bodies, derived from mouse embryonic stem cells, were cultured on basement membrane matrix with added BMP-4 for 10 days. The identification of differentiated keratinocyte-like cells was done by detection of cytokeratin-8 and cytokeratin-14 localization using an indirect immunoperoxidase technique and transmission electron microscopy evaluation. Distribution of BrdU, cytokeratin-8 and cytokeratin-14 were evaluated using an indirect immunoperoxidase technique from the experimental (dressing including BrdU labelled cells applied after the surgical wound was created on mouse), control (only the surgical wound was created on mouse) and sham (only the dressing applied after the surgical wound was created on mouse) in groups after 3, 5 and 7 days. Immunohistochemically and ultrastructurally, cells derived from mouse embryonic stem cells were similar to differentiated keratinocyte-like cells. Differentiated keratinocyte-like cells were demonstrated by positive BrdU, cytokeratin-8 and cytokeratin-14 staining after transfer to the wound area. In the experimental group wound healing was better after transferring differentiated keratinocytes when compared to the sham and control groups. In vivo continuity and usability of derived cells are very important issues. In wound repair mechanisms, keratinocyte-like cells could provide positive effects during the wound healing and could be used in clinical treatments of wound repair process.

Differentiation of human induced pluripotent stem cells into a keratinocyte lineage

Direct reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) provides an opportunity to develop novel personalized treatment options for numerous diseases and to advance current approaches for cell-based drug discoveries and disease modeling. The ability to differentiate iPSCs into relevant cell types is an important prerequisite for the successful development of iPSC-based treatment and modeling strategies. Here, we describe a protocol for the efficient differentiation of human iPSCs into functional keratinocytes. The protocol employs treating iPSCs with retinoic acid and bone-morphogenetic protein-4 to induce differentiation toward a keratinocyte lineage, which is then followed by the growth of differentiated iPSCs on collagen type I- and collagen type IV-coated dishes to enrich for iPSC-derived keratinocytes.

Generation of functional multipotent keratinocytes from mouse induced pluripotent stem cells

Recent advances in reprogramming somatic cells into induced pluripotent stem cells (iPSCs) offer the possibility of developing new therapeutic approaches for the treatment of a variety of diseases, including inherited skin disorders. While the ultimate goal is the use of iPSCs in the treatment of human diseases, extensive research is still required with preclinical mouse models before iPSC technology can be introduced into the clinic. Therefore, the methodology for the derivation of multipotent keratinocytes from mouse iPSCs is of particular importance since it may allow for the assessment of the feasibility of using iPSCs in the treatment of inherited skin disorders using mouse models which mimic these diseases. Here, we describe two alternative protocols for the efficient differentiation of mouse iPSCs into functional keratinocytes capable of reconstituting a normal stratified epidermis, hair follicles, and sebaceous glands when grafted onto mice. Each protocol results in a different yield and efficiency of keratinocyte derivation depending on the mouse genetic background used in the study. Both protocols employ applications of retinoic acid and bone-morphogenetic protein-4 and growth on collagen type IV-coated dishes to induce iPSC differentiation toward a keratinocyte lineage.

Pluripotent stem cell model reveals essential roles for miR-450b-5p and miR-184 in embryonic corneal lineage specification

Approximately 6 million people worldwide are suffering from severe visual impairments or blindness due to corneal diseases. Corneal allogeneic transplantation is often required to restore vision; however, shortage in corneal grafts and immunorejections remain major challenges. The molecular basis of corneal diseases is poorly understood largely due to lack of appropriate cellular models. Here, we described a robust differentiation of human-induced pluripotent stem cells (hiPSCs) derived from hair follicles or skin fibroblasts into corneal epithelial-like cells. We found that BMP4, coupled with corneal fibroblast-derived conditioned medium and collagen IV allowed efficient corneal epithelial commitment of hiPSCs in a manner that recapitulated corneal epithelial lineage development with high purity. Organotypic reconstitution assays suggested the ability of these cells to stratify into a corneal-like epithelium. This model allowed us identifying miR-450b-5p as a molecular switch of Pax6, a major regulator of eye development. miR-450b-5p and Pax6 were reciprocally distributed at the presumptive epidermis and ocular surface, respectively. miR-450b-5p inhibited Pax6 expression and corneal epithelial fate in vitro, altogether, suggesting that by repressing Pax6, miR-450b-5p triggers epidermal specification of the ectoderm, while its absence allows ocular epithelial development. Additionally, miR-184 was detectable in early eye development and corneal epithelial differentiation of hiPSCs. The knockdown of miR-184 resulted in a decrease in Pax6 and K3, in line with recent findings showing that a point mutation in miR-184 leads to corneal dystrophy. Altogether, these data indicate that hiPSCs are valuable for modeling corneal development and may pave the way for future cell-based therapy.

[The two faces of p63, Janus of the p53 gene family]

The TP53 family member TP63 encodes two main isoforms TAp63 and ΔNp63 with distinct, often opposite functions during development and in the adult. ΔNp63 is crucial for the formation of the ectodermal derivatives and epidermis, while TAp63 is essential for heart development. In the adult, ΔNp63 behaves as a cell survival factor, controlling cell proliferation, adhesion and cell differentiation. In contrast, TAp63 is a proapoptotic factor that protects oocytes from genotoxic insults and prevents premature aging of dermal stem cells. In agreement with these activities, TAp63 is often lost and ΔNp63 overexpressed in cancer cells. Because of their opposite and competitive effects, p63 isoforms could be viewed as Janus two faces. The review focuses on the accumulating data on the p63 functions and regulation in the last decade.

Using stem cells in skin regeneration: possibilities and reality

Tissue-engineered skin has a long history of clinical applications, yet current treatments are not capable of completely regenerating normal, uninjured skin. Nonetheless, the field has experienced a tremendous development in the past 10 years, encountering the summit of tissue engineering (TE) and the arising of stem cell research. Since then, unique features of these cells such as self-renewal capacity, multi-lineage differentiation potential, and wound healing properties have been highlighted. However, a realistic perspective of their outcome in skin regenerative medicine applications is still absent. This review intends to discuss the directions that adult and embryonic stem cells (ESCs) can take, strengthening the skin regeneration field. Distinctively, a critical overview of stem cells' differentiation potential onto skin main lineages, along with a highlight of their participation in wound healing mechanisms, is herein provided. We aim to compile and review significant work to allow a better understanding of the best skin TE approaches, enabling the embodiment of the materialization of a new era in skin regeneration to come, with a conscious overview of the current limitations.

microRNA-34a regulates neurite outgrowth, spinal morphology, and function

The p53 family member TAp73 is a transcription factor that plays a key role in many biological processes, including neuronal development. In particular, we have shown that p73 drives the expression of miR-34a, but not miR-34b and c, in mouse cortical neurons. miR-34a in turn modulates the expression of synaptic targets including synaptotagmin-1 and syntaxin-1A. Here we show that this axis is retained in mouse ES cells committed to differentiate toward a neurological phenotype. Moreover, overexpression of miR-34a alters hippocampal spinal morphology, and results in electrophysiological changes consistent with a reduction in spinal function. Therefore, the TAp73/miR-34a axis has functional relevance in primary neurons. These data reinforce a role for miR-34a in neuronal development.

Hic-5 controls BMP4 responses in prostate cancer cells through interacting with Smads 1, 5 and 8

Hydrogen peroxide-inducible clone-5 (Hic-5, or androgen receptor-associated protein 55) is a transforming growth factor-β (TGF-β)-inducible LIM protein whose deregulation is implicated in the progression of prostate cancer. Here we report that Hic-5 binds to Smads 1, 5 and 8, and represses bone morphogenetic protein (BMP) signaling responses. Myc-Hic-5 but not Myc-paxillin was specifically immunoprecipitated with anti-FLAG IgG1 from lysates of HEK293 co-transfected with either Myc-Hic-5 or Myc-paxillin and FLAG-tagged Smads 1, 5 or 8. We showed that such interactions require the LIM3 domain of Hic-5 and the MH2 domain of those Smads. Anti-Hic-5 antibody specifically pulled down endogenous Smad1 in both the PC3 human prostate cell line and primary cultures of rat prostate fibroblasts, supporting that Hic-5 binds to Smad1 at the endogenous level. Bacterially expressed GST-Smads 1, 5 or 8, but not GST alone, pulled down in vitro transcribed and translated Hic-5, implicating that Hic-5 binds directly to Smads 1, 5 and 8. Significantly, using Hic-5 shRNA silencing and overexpression systems, we show that Hic-5 (at both the endogenous and exogenous levels) represses the ability of BMP4 to induce expression of the inhibitor of differentiation-1 (Id1) (a downstream target gene of BMP), activate the Id1 gene promoter and induce apoptosis in human and rat prostate epithelial cells. Moreover, silencing of Hic-5 in PC3 cells as well as in the WPMY-1 human prostate stroma cell line greatly enhances the levels of endogenous phospho-Smad1/5/8. Finally, we provide fluorescent microscopic imaging to support that Smad1 and Hic-5 mutually interact also at the level of their nuclear export mechanisms. Collectively, these results provide the first evidence for a physical and mutual functional interaction between Hic-5 and the BMP signaling pathway.

Functional melanocytes derived from human pluripotent stem cells engraft into pluristratified epidermis

Melanocytes are essential for skin homeostasis and protection, and their defects in humans lead to a wide array of diseases that are potentially extremely severe. To date, the analysis of molecular mechanisms and the function of human melanocytes have been limited because of the difficulties in accessing large numbers of cells with the specific phenotypes. This issue can now be addressed via a differentiation protocol that allows melanocytes to be obtained from pluripotent stem cell lines, either induced or of embryonic origin, based on the use of moderate concentrations of a single cytokine, bone morphogenic protein 4. Human melanocytes derived from pluripotent stem cells exhibit all the characteristic features of their adult counterparts. This includes the enzymatic machinery required for the production and functional delivery of melanin to keratinocytes. Melanocytes also integrate appropriately into organotypic epidermis reconstructed in vitro. The availability of human cells committed to the melanocytic lineage in vitro will enable the investigation of those mechanisms that guide the developmental processes and will facilitate analysis of the molecular mechanisms responsible for genetic diseases. Access to an unlimited resource may also prove a vital tool for the treatment of hypopigmentation disorders when donors with matching haplotypes become available in clinically relevant banks of pluripotent stem cell lines.

Neuronal loss and abnormal BMP/Smad signaling in the myenteric plexus of diabetic rats

Bone morphogenetic proteins (BMPs) are critical molecules during gut morphogenesis. However, little is known about their participation in the homeostasis of adult gut and their possible role in diseases. Gastrointestinal complications occur during diabetes with loss of enteric neurons. In this study, we investigated the possible involvement of BMPs signaling pathway in diabetic enteric neuropathy in an experimental model of diabetes in rats. The expression of BMPs, BMPs receptors and intracellular Smad effectors were assessed in control and diabetic smooth muscle layer of jejunum by immunofluorescence, Western blot and RT-PCR methods. Myenteric neurons and glial cells were measured by immunofluorescence using specific markers. In addition, cell apoptosis was evaluated by means of direct and indirect techniques. We demonstrated that diabetic ganglia displayed a significant decrease in ganglion size due to enhanced apoptosis and loss of peripherin. A decrease in glial fibrillary acidic protein (GFAP protein) was also observed in enteric glial cells. BMP-2 was down-regulated in the myenteric plexus of diabetic rats at 3 and 9weeks. A loss of enteric neurons by apoptosis was correlated with an ectopic BMP-4, increased BMPR-Ia and nuclear p-Smad1 expression in the myenteric plexus. Insulin-treatment prevented the intestinal alterations observed. These findings suggest that diabetes is associated with an abnormal BMP/Smad signaling expression in the myenteric ganglia that affects the homeostasis of the enteric plexus.

TGF-β/BMPs: crucial crossroad in neural autoimmune disorders

Transforming growth factor beta (TGF-β) has a crucial role in the differentiation of ectodermal cells to neural or epidermal precursors. TGF-β and bone morphogenetic protein molecules (BMPs) are involved in many developmental processes, including cell proliferation and differentiation, apoptosis, mitotic arrest and intercellular interactions during morphogenesis. Additionally, the failure of central thymic tolerance mechanisms, leading to T cells with a skewed autoreactive response, is being described as a contributor in inflammatory processes in autoimmune diseases such as multiple sclerosis. Since TGF-β and BMP proteins are crucial for the development of the neural system and the thymus, as well as for the differentiation of T cells, it is essential to further investigate their role in the pathophysiology of this disorder by using references from embryonic experimental research. Available literature in the TGF/BMP signalling cascade, mostly during embryonic development of the nervous system is being reviewed. An attempt is made to further elucidate a potential role of TGF/BMP signalling in the pathophysiology of MS. During demyelination, BMP signaling, through various molecular mechanisms, directs the development of the adult neural stem cell in the astrocyte rather than the oligodendrocyte direction, therefore inhibiting the repair process. Further understanding of the above relationships could lead to the development of potentially efficient therapies for MS in the future.

Senataxin modulates neurite growth through fibroblast growth factor 8 signalling

Senataxin is encoded by the SETX gene and is mainly involved in two different neurodegenerative diseases, the dominant juvenile form of amyotrophic lateral sclerosis type 4 and a recessive form of ataxia with oculomotor apraxia type 2. Based on protein homology, senataxin is predicted to be a putative DNA/RNA helicase, while senataxin interactors from patients' lymphoblast cell lines suggest a possible involvement of the protein in different aspects of RNA metabolism. Except for an increased sensitivity to oxidative DNA damaging agents shown by some ataxia with neuropathy patients' cell lines, no data are available about possible functional consequences of dominant SETX mutations and no studies address the function of senataxin in neurons. To start elucidating the physiological role of senataxin in neurons and how disease-causing mutations in this protein lead to neurodegeneration, we analysed the effect of senataxin on neuronal differentiation in primary hippocampal neurons and retinoic acid-treated P19 cells by modulating the expression levels of wild-type senataxin and three different dominant mutant forms of the protein. Wild-type senataxin overexpression was required and sufficient to trigger neuritogenesis and protect cells from apoptosis during differentiation. These actions were reversed by silencing of senataxin. In contrast, overexpression of the dominant mutant forms did not affect the regular differentiation process in primary hippocampal neurons. Analysis of the cellular pathways leading to neuritogenesis and cytoprotection revealed a role of senataxin in modulating the expression levels and signalling activity of fibroblast growth factor 8. Silencing of senataxin reduced, while overexpression enhanced, fibroblast growth factor 8 expression levels and the phosphorylation of related target kinases and effector proteins. The effects of senataxin overexpression were prevented when fibroblast growth factor 8 signalling was inhibited, while exogenous fibroblast growth factor 8 reversed the effects of senataxin silencing. Overall, these results reveal a key role of senataxin in neuronal differentiation through the fibroblast growth factor 8 signalling and provide initial molecular bases to explain the neurodegeneration associated with loss-of-function mutations in senataxin found in recessive ataxia. The lack of effect on neuritogenesis observed with the overexpression of the dominant mutant forms of senataxin apparently excludes a dominant negative effect of these mutants while favouring haploinsufficiency as the pathogenic mechanism implicated in the amyotrophic lateral sclerosis 4-related degenerative condition. Alternatively, a different protein function, other than the one involved in neuritogenesis, may be implicated in these dominant degenerative processes.