Do binucleate cardiomyocytes have a role in myocardial repair? Insights using isolated rodent myocytes and cell culture.

Neonatal and adult cardiomyocytes were isolated from rat hearts. Some of the adult myocytes were cultured to allow for cell dedifferentiation, a phenomenon thought to mimic cell changes that occur in stressed myocardium, with myocytes regressing to a fetal pattern of metabolism and stellate neonatal shape.Using fluorescence deconvolution microscopy, cells were probed with fluorescent markers and scanned for a number of proteins associated with ion control, calcium movements and cardiac function. Image analysis of deconvoluted image stacks and sequential real-time image recordings of calcium transients of cells were made.All three myocyte groups were predominantly comprised of binucleate cells. Clustering of proteins to a single nucleus was a common observation, suggesting that one nucleus is active in protein synthesis pathways, while the other nucleus assumes a 'dormant' or different role and that cardiomyocytes might be mitotically active even in late development, or specific protein syntheses could be targeted and regulated for reintroduction into the cell cycle.Such possibilities would extend cardiac disease associated stem cell research and therapy options, while producing valuable insights into developmental and death pathways of binucleate cardiomyocytes (word count 183).

Progenitor cell therapies for traumatic brain injury: barriers and opportunities in translation.

Traumatic brain injury (TBI) directly affects nearly 1.5 million new patients per year in the USA, adding to the almost 6 million cases in patients who are permanently affected by the irreversible physical, cognitive and psychosocial deficits from a prior injury. Adult stem cell therapy has shown preliminary promise as an option for treatment, much of which is limited currently to supportive care. Preclinical research focused on cell therapy has grown significantly over the last decade. One of the challenges in the translation of this burgeoning field is interpretation of the promising experimental results obtained from a variety of cell types, injury models and techniques. Although these variables can become barriers to a collective understanding and to evidence-based translation, they provide crucial information that, when correctly placed, offers the opportunity for discovery. Here, we review the preclinical evidence that is currently guiding the translation of adult stem cell therapy for TBI.

STUDY OF REST AS A NEGATIVE REGULATOR OF P16INK4A

STUDY OF REST AS A NEGATIVE REGULATOR OF P16INK4A Monica Gireud, B.S. Thesis Advisor: Vidya Gopalakrishnan, Ph.D. The RE1 Silencing Transcription Factor (REST) is a negative regulator of neuronal differentiation. It is expressed ubiquitously in early embryos, but downregulated in neural progenitors concomitant with onset of neuronal differentiation in these cells. REST has been widely studied as a negative regulator of neuronal differentiation genes. Our recent work identified a novel role for REST in control of cell proliferation. However, the underlying molecular mechanism(s) are not known and is a focus of the current thesis project. Here, we provide evidence that REST signaling controls the expression of the cyclin-dependent kinase inhibitor, p16Ink4a, a negative regulator of the cell cycle and passage through G1. We determined that REST expression in the proliferating granule progenitors of the cerebellum and its lack of expression in the differentiated neurons is reciprocally correlated with that of p16Ink4a. Decline in REST levels in differentiating primary and neural stem cells immortalized with v-myc (NSC-M) granule progenitors in vitro was also associated with upregulation of p16Ink4a expression. Conversely, constitutive human REST transgene expression in NSC-M cells (NSC-MRs) blocked p16Ink4 upregulation, even under neuronal differentiation conditions. However, the lack of a consensus REST DNA binding RE1 element in the regulatory regions of p16Ink4a locus suggested an indirect regulation of p16Ink4a by REST. Based on work from other groups that showed repression of p16Ink4a transcription by the polycomb protein Bmi-1, and its negative regulation by microRNA-203 (miR-203) and our identification of a RE1 element in the downstream regulatory region of miR-203, we asked if the p16Ink4a expression was controlled by REST through a series of negative regulatory events involving miR-203 and Bmi-1. We observed that Bmi1 -expression mirrored that of REST and inversely correlated with that of miR-203 in the postnatal cerebellum and in vitro differentiated granule and NSC-M progenitors. In contrast, forced REST transgene expression in NSC-MR cells abrogated the decrease in Bmi-1 levels and elevation in miR-203 expression. Significant REST binding to the miR-203 RE1 element was also observed in NSC-M cells, indicating that REST had the potential to directly regulate miR-203 expression. In conclusion, our studies suggest a role for REST in control of cell cycle transit in neural progenitors through negative regulation of p16Ink4a. Further validation of these results in REST knockout mice is needed, and is ongoing.

The secretome of induced pluripotent stem cells reduces lung fibrosis in part by hepatocyte growth factor.

INTRODUCTION Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible fibrotic lung disease, resulting in respiratory insufficiency and reduced survival. Pulmonary fibrosis is a result of repeated alveolar epithelial microinjuries, followed by abnormal regeneration and repair processes in the lung. Recently, stem cells and their secretome have been investigated as a novel therapeutic approach in pulmonary fibrosis. We evaluated the potential of induced pluripotent stem cells (iPSC) conditioned media (iPSC-cm) to regenerate and repair the alveolar epithelium in vitro and improve bleomycin induced lung injury in vivo. METHODS IPSC-cm was collected from cultured iPSC derived from human foreskin fibroblasts and its biological effects on alveolar epithelial wound repair was studied in an alveolar wound healing assay in vitro. Furthermore, iPSC-cm was intratracheally instilled 7 days after bleomycin induced injury in the rat lungs and histologically and biochemically assessed 7 days after instillation. RESULTS iPSC-cm increased alveolar epithelial wound repair in vitro compared with medium control. Intratracheal instillation of iPSC-cm in bleomycin-injured lungs reduced the collagen content and improved lung fibrosis in the rat lung in vivo. Profibrotic TGFbeta1 and alpha-smooth muscle actin (alpha-sma) expression were markedly reduced in the iPSC-cm treated group compared with control. Antifibrotic hepatocyte growth factor (HGF) was detected in iPSC-cm in biologically relevant levels, and specific inhibition of HGF in iPSC-cm attenuated the antifibrotic effect of iPSC-cm, indicating a central role of HGF in iPSC-cm. CONCLUSION iPSC-cm increased alveolar epithelial wound repair in vitro and attenuated bleomycin induced fibrosis in vivo, partially due to the presence of HGF and may represent a promising novel, cell free therapeutic option against lung injury and fibrosis.

Mechanical Loading Promoted Discogenic Differentiation of Human Mesenchymal Stem Cells Incorporated in 3D-PEG Scaffolds with RhGDF5 and RGD

Hydrogels have been described as ideal scaffolds for cells of 3D tissue constructs and hold strong promises with respect to in vitro 3D-cell-culture, where cells are isolated from native extracellular matrix (ECM). Synthesized polyethyleneglycol (PEG) hydrogels are appealing with regard to potential for cell therapy or as vehicles for drug delivery or even to regenerate tissue with similar hydrogel-like properties such as the nucleus pulposus of the intervertebral disc (IVD). Here, we tested whether incorporation of RGD motive would hinder discogenic differentiation of primary bone marrow-derived human mesenchymal stem cells (hMSCs) but favor proliferation of undifferentiated hMSCs. HMSCs were embedded in +RGD containing or without RGD PEG hydrogel and pre-conditioned with or without growth and differentiation factor-5 (rhGDF-5) for 13 days. Afterwards, all hMSCs-PEG gels were subsequently cyclically loaded (15% strain, 1Hz) for 5 consecutive days in a bioreactor to generate an IVD-like phenotype. Higher metabolic activity (resazurin assay) was found in groups with rhGDF5 in both gel types with and without RGD. Cell viability and morphology measured by confocal laser microscopy and DNA content showed decreased values (~60%) after 18 days of culture. Real-time RT-PCR of an array of 15 key genes suspected to be distinctive for IVD cells revealed moderate response to rhGDF5 and mechanical loading as also shown by histology staining. Preconditioning and mechanical loading showed relatively moderate responses revealed from both RT-PCR and histology although hMSCs were demonstrated to be potent to differentiate into chondrocyte-progenitor cells in micro- mass and 3D alginate bead culture.

Cell-to-cell communication--periodontal regeneration.

BACKGROUND Although regenerative treatment options are available, periodontal regeneration is still regarded as insufficient and unpredictable. AIM This review article provides scientific background information on the animated 3D film Cell-to-Cell Communication - Periodontal Regeneration. RESULTS Periodontal regeneration is understood as a recapitulation of embryonic mechanisms. Therefore, a thorough understanding of cellular and molecular mechanisms regulating normal tooth root development is imperative to improve existing and develop new periodontal regenerative therapies. However, compared to tooth crown and earlier stages of tooth development, much less is known about the development of the tooth root. The formation of root cementum is considered the critical element in periodontal regeneration. Therefore, much research in recent years has focused on the origin and differentiation of cementoblasts. Evidence is accumulating that the Hertwig's epithelial root sheath (HERS) has a pivotal role in root formation and cementogenesis. Traditionally, ectomesenchymal cells in the dental follicle were thought to differentiate into cementoblasts. According to an alternative theory, however, cementoblasts originate from the HERS. What happens when the periodontal attachment system is traumatically compromised? Minor mechanical insults to the periodontium may spontaneously heal, and the tissues can structurally and functionally be restored. But what happens to the periodontium in case of periodontitis, an infectious disease, after periodontal treatment? A non-regenerative treatment of periodontitis normally results in periodontal repair (i.e., the formation of a long junctional epithelium) rather than regeneration. Thus, a regenerative treatment is indicated to restore the original architecture and function of the periodontium. Guided tissue regeneration or enamel matrix proteins are such regenerative therapies, but further improvement is required. As remnants of HERS persist as epithelial cell rests of Malassez in the periodontal ligament, these epithelial cells are regarded as a stem cell niche that can give rise to new cementoblasts. Enamel matrix proteins and members of the transforming growth factor beta (TGF-ß) superfamily have been implicated in cementoblast differentiation. CONCLUSION A better knowledge of cell-to-cell communication leading to cementoblast differentiation may be used to develop improved regenerative therapies to reconstitute periodontal tissues that were lost due to periodontitis.

Mesenchymal Stem Cells from Wharton's Jelly and Amniotic Fluid

The discovery of mesenchymal stem cells (MSCs) in perinatal sources, such as the amniotic fluid (AF) and the umbilical connective tissue, the so-called Wharton's jelly (WJ), has transformed them into promising stem cell grafts for the application in regenerative medicine. The advantages of AF-MSCs and WJ-MSCs over adult MSCs, such as bone marrow-derived mesenchymal stem cells (BMMSCs), include their minimally invasive isolation procedure, their more primitive cell character without being tumourigenic, their low immunogenicity and their potential autologous application in congenital disorders and when cryopreserved in adulthood. This chapter gives an overview of the biology of AF-MSCs and WJMSCs, and their regenerative potential based on the results of recent preclinical and clinical studies. In the end, open questions concerning the use of WJ-MSCs and AF-MSCs in regenerative medicine will be emphasized.

Assessment of bovine adipose-derived stem cells osteogenic and adipogenic differentiation in Normoxic and hypoxic conditions

Background: The differentiation of ADSC is regulated by many factors, including oxygen tensions. Evidences have suggested that low oxygen tension or hypoxia is involved in the osteogenic, adipogenic differentiations of MSCs. Expansion and induction of ADSCs under hypoxia generally result in enhanced osteogenic, differentiation. Therefore, we analyzed bovine ADSC differentiations in Normoxia and hypoxia conditions Methodology: Recently (<8h) cow tail from a slaughterhouse, take out some fat from the tail and fat cells was isolated by using for isolation of ADSC protocol, the expansion cells were put into osteogenic and adipogenic medium for 3 weeks in hypoxia and normoxia conditions separately and characterized by Von kossa, Alizarin red and Oil red O staining and further by using real-time PCR by using primers of osteocalcin, Collagen type1, cbfa1/runx2, ALP, ostepontin, osteonectin, BMP2, BMP24, BMP27, noggin, gremlin, Nestin and HIF1A,VEGFA,PPARG,Leptin. Results: Our experiment results show hypoxia promotes osteogenesis but suppresses adipogenesis.

Cell cycle reactivation of cochlear progenitor cells in neonatal FUCCI mice by a GSK3 small molecule inhibitor.

Due to the lack of regenerative capacity of the mammalian auditory epithelium, sensory hair cell loss results in permanent hearing deficit. Nevertheless, a population of tissue resident stem/progenitor cells has been recently described. Identification of methods to trigger their activity could lead to exploitation of their potential therapeutically. Here we validate the use of transgenic mice reporting cell cycle progression (FUCCI), and stemness (Lgr5-GFP), as a valuable tool to identify regulators of cell cycle re-entry of supporting cells within the auditory epithelium. The small molecule compound CHIR99021 was used to inhibit GSK3 activity. This led to a significant increase in the fraction of proliferating sphere-forming cells, labeled by the FUCCI markers and in the percentage of Lgr5-GFP + cells, as well as a selective increase in the fraction of S-G2-M cells in the Lgr5 + population. Using whole mount cultures of the organ of Corti we detected a statistically significant increment in the fraction of proliferating Sox2 supporting cells after CHIR99021 treatment, but only rarely appearance of novel MyoVIIa+/Edu + hair cells. In conclusion, these tools provide a robust mean to identify novel regulators of auditory organ regeneration and to clarify the contribution of stem cell activity.

Tyrosine kinase inhibitor-induced CD70 expression mediates drug resistance in leukemia stem cells by activating Wnt signaling.

In chronic myelogenous leukemia (CML), oncogenic BCR-ABL1 activates the Wnt pathway, which is fundamental for leukemia stem cell (LSC) maintenance. Tyrosine kinase inhibitor (TKI) treatment reduces Wnt signaling in LSCs and often results in molecular remission of CML; however, LSCs persist long term despite BCR-ABL1 inhibition, ultimately causing disease relapse. We demonstrate that TKIs induce the expression of the tumor necrosis factor (TNF) family ligand CD70 in LSCs by down-regulating microRNA-29, resulting in reduced CD70 promoter DNA methylation and up-regulation of the transcription factor specificity protein 1. The resulting increase in CD70 triggered CD27 signaling and compensatory Wnt pathway activation. Combining TKIs with CD70 blockade effectively eliminated human CD34(+) CML stem/progenitor cells in xenografts and LSCs in a murine CML model. Therefore, targeting TKI-induced expression of CD70 and compensatory Wnt signaling resulting from the CD70/CD27 interaction is a promising approach to overcoming treatment resistance in CML LSCs.

Cell Competition During Growth and Regeneration

Tissue growth and regeneration are autonomous, stem-cell-mediated processes in which stem cells within the organ self-renew and differentiate to create new cells, leading to new tissue. The processes of growth and regeneration require communication and interplay between neighboring cells. In particular, cell competition, which is a process in which viable cells are actively eliminated by more competitive cells, has been increasingly implicated to play an important role. Here, we discuss the existing literature regarding the current landscape of cell competition, including classical pathways and models, fitness fingerprint mechanisms, and immune system mechanisms of cell competition. We further discuss the clinical relevance of cell competition in the physiological processes of tissue growth and regeneration, highlighting studies in clinically important disease models, including oncological, neurological, and cardiovascular diseases.

The Role of EphA4 in Glial Scar Formation Following Injury

Although many areas of the brain lose their regenerative capacity with age, stem cell niches have been identified in both the subventricular zone (SVZ) along the lateral walls of the lateral ventricles and the subgranular zone (SGZ) of the dentate gyrus (Gage, 2000; Alvarez-Buylla et al., 2001; Alvarez-Buylla and Lim, 2004). The SVZ niche utilizes many mechanisms to determine the migration patterns of neuroblasts along the RMS into the olfactory bulb, one being Eph/ephrin signaling (Conover et al., 2000; Holmberg et al., 2005). EphA4-mediated signaling is necessary for axon guidance during development, and its continued expression in the SVZ niche suggests a regulatory role throughout adulthood. Previous studies have suggested that EphA4 plays a role in the regulation of astrocytic gliosis and glial scar formation, which inhibits axonal regeneration in these areas following spinal cord injury (Goldshmit et al., 2004). Blood vessels may also play an important role in SVZ cell proliferation and neuroblast migration following injury (Tavazoie et al., 2008; Yamashita et al., 2006). The goal of this project is to examine glial scar formation as well as the relationship between SVZ vasculature, neuroblasts, and neural stem cells in EphA4 +/+, EphA4 +/-, and EphA4 -/- mice following a needle stick injury in the cortex or striatum. The outcome of these experiments will determine whether invasive procedures such as injections will affect neuroblast migration and/or the organization of the SVZ.

Abnormal expression of E2F1 and E2F4 results in hyperproliferation of the ependyma and lethal hydrocephalus

The proliferative role of E2F has been under investigation for several years. However, while it is known that E2F1 and E2F4 play a part in development and differentiation, research has not been centered on determining the exact functions these E2Fs play in brain development, given there high expression levels throughout embryogenesis. A GFAP-E2F1 mouse model directing human E2F1 transgene expression to glial cells, such as ependymal cells, was used in the present study in combination with an E2F4 mutant mouse model. Interestingly, 20% of tgE2F1; E2F4 null mice developed a phenotype consisting of domed head, hunched posture, seizures, tremors, hyperactivity or hypeactivity, dysnea, and low body weight. These mice died during the first three weeks of severe hydrocephalus. Similarly, tgE2F1; E2F4 heterozygous mice also develop severe hydrocephalus, although this occurs at 6 weeks at a 2% frequency. Pathological examination of the brains of those animals uncovered enlarged cerebral ventricles with marked thinning of the cerebral cortices, confirming the diagnosis of three-ventricle hydrocephalus, and the absence of tumors. Careful examination of the aqueduct shows an excess of proliferating cells that may cause a blockage of CSF. Of significance, 44% of ependymal cells in hydrocephalic tgE2F1;E2F4-/- mouse brains were positive for BrdU incorporation. Studies determining the molecular rationale for the hydrocephalic phenotype suggest proliferative ependymal cells may not be exclusively related to dysregulated cell cycle in conjuction with E2F activity. Due in part to the deficiency of E2F4 in this mouse model, we find that differentiation of these ependymal cells is not complete and instead undergoes maturation arrest. This suggestion is confirmed by the expression of genes found in neural stem cells or precursor cell populations, in the ependymal cell region of tgE2F1; E2F4-/-. Therefore, from this study, we conclude that dysregulated E2F1 expression in combination with deficient E2F4 expression results in an undifferentiated ependymal cell population that is hyperproliferative in the ventricular system causing an impediment of CSF circulation. It is further concluded that normal E2F1 and E2F4 expression in brain development is crucial for the proper formation and function of the ventricular system.^

Transcriptional and translational regulators of gene expression in germ cell development

Germ cell development is a highly coordinated process driven, in part, by regulatory mechanisms that control gene expression. Not only transcription, but also translation, is under regulatory control to direct proper germ cell development. In this dissertation, I have focused on two regulators of germ cell development. One is the homeobox protein RHOX10, which has the potential to be both a transcriptional and translational regulator in mouse male germ cell development. The other is the RNA-binding protein, Hermes, which functions as a translational regulator in Xenopus laevis female germ cell development. ^ Rhox10 is a member of reproductive homeobox gene X-(linked (Rhox) gene cluster, of which expression is developmentally regulated in developing mouse testes. To identify the cell types and developmental stages in which Rhox10 might function, I characterized its temporal and spatial expression pattern in mouse embryonic, neonatal, and adult tissues. Among other things, this analysis revealed that both the level and the subcellular localization of RHOX10 are regulated during germ cell development. To understand the role of Rhox10 in germ cell development, I generated transgenic mice expressing an artificial microRNA (miRNA) targeting Rhox10. While this artificial miRNA robustly downregulated RHOX10 protein expression in vitro, it did not significantly reduce RHOX10 expression in vivo. So I next elected to knockdown RHOX10 levels in spermatogonial stem cells (SSCs), which I found highly express both Rhox10 mRNA and RHOX10 protein. Using a recently developed in vitro culture system for SSCs combined with a short-hairpin RNA (shRNA) approach, I strongly depleted RHOX10 expression in SSCs. These RHOX10-depleted cells exhibited a defect in the ability to form stem cell clusters in vitro. Expression profiling analysis revealed many genes regulated by Rhox10, including many meiotic genes, which could be downstream of Rhox10 in a molecular pathway that controls SSC differentiation. ^ RNA recognition motif (RRM) containing protein, Hermes is localized in germ plasm, where dormant mRNAs are also located, of Xenopus oocytes, which implicates its role in translational regulator. To understand the function of Hermes in oocyte meiosis, I used a morpholino oligonucleotide (MO) based knockdown approach. Microinjection of Hermes MO into fully grown oocytes, which are arrested in meiotic prophase, caused acceleration of oocytes reentry into meiosis (i.e., maturation) upon progesterone induction. Using a candidate approach, I identified at least three targets of Hermes: Ringo/Spy, Xcat2, and Mos. Ringo/Spy and Mos are known to have functions in oocyte maturation, while Ringo/Spy, Xcat2 mRNA are localized in the germ plasm of oocytes, which drives germ cell specification after fertilization. This led me to propose that Hermes functions in both oocyte maturation and germ cell development through its ability to regulate 3 crucial target mRNAs. ^