Osteogenic Embryoid Body-Derived Material Induces Bone Formation In Vivo

The progressive loss of endogenous regenerative capacity that accompanies mammalian aging has been attributed at least in part to alterations in the extracellular matrix (ECM) composition of adult tissues. Thus, creation of a more regenerative microenvironment, analogous to embryonic morphogenesis, may be achieved via pluripotent embryonic stem cell (ESC) differentiation and derivation of devitalized materials as an alternative to decellularized adult tissues, such as demineralized bone matrix (DBM). Transplantation of devitalized ESC materials represents a novel approach to promote functional tissue regeneration and reduce the inherent batch-to-batch variability of allograft-derived materials. In this study, the osteoinductivity of embryoid body-derived material (EBM) was compared to DBM in a standard in vivo ectopic osteoinduction assay in nude mice. EBM derived from EBs differentiated for 10 days with osteogenic media (+β-glycerophosphate) exhibited similar osteoinductivity to active DBM (osteoinduction score = 2.50 ± 0.27 vs. 2.75 ± 0.16) based on histological scoring, and exceeded inactive DBM (1.13 ± 0.13, p \u3c 0.005). Moreover, EBM stimulated formation of new bone, ossicles, and marrow spaces, similar to active DBM. The potent osteoinductivity of EBM demonstrates that morphogenic factors expressed by ESCs undergoing osteogenic differentiation yield a novel devitalized material capable of stimulating de novo bone formation in vivo

Retracing the history and planning the future of the red squirrel (Sciurus vulgaris) in Ireland using non-invasive genetics

The Eurasian red squirrel’s (Sciurus vulgaris) history in Ireland is largely unknown, but the original population is thought to have been driven to extinction by humans in the 17th Century, and multiple records exist for its subsequent reintroduction in the 19th 4 Century. However, it is currently unknown how these reintroductions affect the red squirrel population today, or may do so in the future. In this study, we report on the development of a DNA toolkit for the non-invasive genetic study of the red squirrel. Non-invasively collected red squirrel samples were combined with other samples collected throughout Ireland and previously published mitochondrial DNA (mtDNA) data from Ireland, Great Britain and continental Europe to give an insight into population genetics and historical introductions of the red squirrel in Ireland. Our findings demonstrate that the Irish red squirrel population is on a national scale quite genetically diverse, but at a local level contains relatively low levels of genetic diversity and evidence of genetic structure. This is likely an artefact of the introduction of a small number of genetically similar animals to specific sites. A lack of continuous woodland cover in Ireland has prevented further mixing with animals of different origins that may have been introduced even to neighbouring sites. Consequently, some of these genetically isolated populations are or may in the future be at risk of extinction. The Irish red squirrel population contains mtDNA haplotypes of both a British and Continental European origin, the former of which are now extinct or simply not recorded in contemporary Great Britain. The Irish population is therefore important in terms of red squirrel conservation not only in Ireland, but also for Great Britain, and should be appropriately managed

Histone H1 Depletion Impairs Embryonic Stem Cell Differentiation

Pluripotent embryonic stem cells (ESCs) are known to possess a relatively open chromatin structure; yet, despite efforts to characterize the chromatin signatures of ESCs, the role of chromatin compaction in stem cell fate and function remains elusive. Linker histone H1 is important for higher-order chromatin folding and is essential for mammalian embryogenesis. To investigate the role of H1 and chromatin compaction in stem cell pluripotency and differentiation, we examine the differentiation of embryonic stem cells that are depleted of multiple H1 subtypes. H1c/H1d/H1e triple null ESCs are more resistant to spontaneous differentiation in adherent monolayer culture upon removal of leukemia inhibitory factor. Similarly, the majority of the triple-H1 null embryoid bodies (EBs) lack morphological structures representing the three germ layers and retain gene expression signatures characteristic of undifferentiated ESCs. Furthermore, upon neural differentiation of EBs, triple-H1 null cell cultures are deficient in neurite outgrowth and lack efficient activation of neural markers. Finally, we discover that triple-H1 null embryos and EBs fail to fully repress the expression of the pluripotency genes in comparison with wild-type controls and that H1 depletion impairs DNA methylation and changes of histone marks at promoter regions necessary for efficiently silencing pluripotency gene Oct4 during stem cell differentiation and embryogenesis. In summary, we demonstrate that H1 plays a critical role in pluripotent stem cell differentiation, and our results suggest that H1 and chromatin compaction may mediate pluripotent stem cell differentiation through epigenetic repression of the pluripotency genes

Genomic Relationships, Novel Loci, and Pleiotropic Mechanisms across Eight Psychiatric Disorders

Genetic influences on psychiatric disorders transcend diagnostic boundaries, suggesting substantial pleiotropy of contributing loci. However, the nature and mechanisms of these pleiotropic effects remain unclear. We performed analyses of 232,964 cases and 494,162 controls from genome-wide studies of anorexia nervosa, attention-deficit/hyper-activity disorder, autism spectrum disorder, bipolar disorder, major depression, obsessive-compulsive disorder, schizophrenia, and Tourette syndrome. Genetic correlation analyses revealed a meaningful structure within the eight disorders, identifying three groups of inter-related disorders. Meta-analysis across these eight disorders detected 109 loci associated with at least two psychiatric disorders, including 23 loci with pleiotropic effects on four or more disorders and 11 loci with antagonistic effects on multiple disorders. The pleiotropic loci are located within genes that show heightened expression in the brain throughout the lifespan, beginning prenatally in the second trimester, and play prominent roles in neurodevelopmental processes. These findings have important implications for psychiatric nosology, drug development, and risk prediction.Peer reviewe

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

McDevitt Laboratory - Engineering Stem Cell Technologies

Todd C. McDevitt is an Assistant Professor, Petit Fellow at the Wallace H. Coulter Dept. of Biomedical Engineering, Georgia Institute of Technology. He is the director of the Stem Cell Engineering Center

Engineering Stem Cell Technologies

Presented on April 21, 2009 from 8:30-9:30 am in IBB Building room 1128 on the Georgia Tech campus.Runtime: 58:06 minutesThe McDevitt laboratory is focused on the engineering of innovative technologies to translate the regenerative potential of stem cells into effective cellular and molecular therapies for the treatment of degenerative diseases and traumatic injuries. By developing controlled systems approaches to engineer the microenvironment of stem cells, we aspire to improve the efficiency and yield of directed stem cell differentiation strategies. We also seek to develop novel regenerative molecular therapies based on the morphogens produced by stem cells. Efficient scalable bioprocesses will require the development of enabling tools and technologies to facilitate the production of stem cell technologies. The combination of directed stem cell differentiation and derivation of stem cell biotherapeutics will yield fresh insights into stem cell biology and facilitate new regenerative therapies

Spatially controlled engineering of myocardial tissue

Thesis (Ph. D.)--University of Washington, 2001Developmental biology and tissue regeneration processes utilize specific spatial adhesive cues to direct the assembly of cells into complex, organized tissues. Microfabrication methods provide analogous technologies to accurately control the displacement of proteins and cells in vitro to mimic their natural spatial organization. Thus, we have investigated how spatially controlled engineering of protein interfaces can be used to direct cellular response and the organized assembly of tissues. Adhesive extracellular matrix proteins were micropatterned directly by microcontact printing onto a number of different substrates and shown to spatially control the attachment of various anchorage dependent mammalian cell types. Specifically, micropatterned lanes of laminin were used to guide the adhesion and organization of cardiomyocytes on polymeric surfaces such that they exhibited a more mature and fully differentiated phenotype. Morphological features of native myocardium, such as the dimensions of individual cardiomyocytes, myofibril assembly and organization, intercalated disk localization and synchronous contractile behavior, were reproduced by micropatterned cultures of cardiomyocytes on polystyrene substrates. The true myocardium, however, is an organized, heterogeneous tissue composed of various cell types, thus a spatially defined co-culture system was developed, utilizing an engineered streptavidin mutant, to facilitate secondary cell adhesion between patterned rows of cardiomyocytes. Comparable cardiomyocyte patterns were also achieved on thin films of resorbable polymers (i.e. PLGA and biodegradable polyurethane), in order to engineer organized sheets of cardiomyocytes. Dense, highly aligned layers of cardiomyocytes could contract thin elastomeric polyurethane films and were successfully grafted onto the surface of the heart in nude mice. This method represents a novel therapeutic approach to potentially repair infarcted myocardium by transplanting spatially organized layers of cardiac tissue. In addition to tissue engineering applications, patterned cardiomyocyte cultures are also applicable to in vitro cell biology and physiological studies or diagnostic applications, such as pharmacological screening, that require more accurate reproduction of native myocardial architecture

Design Principles for Engineering of Tissues from Human Pluripotent Stem Cells.

Recent advances in human pluripotent stem cell (hPSC) technologies have enabled the engineering of human tissue constructs for developmental studies, disease modeling, and drug screening platforms. In vitro tissue formation can be generally described at three levels of cellular organization. Multicellular hPSC constructs are initially formed either with polymeric scaffold materials or simply via self-assembly, adhesive mechanisms. Heterotypic interactions within hPSC tissue constructs can be achieved by physically mixing independently differentiated cell populations or coaxed to simultaneously co-emerge from a common population of undifferentiated cells. Higher order tissue architecture can be engineered by imposing external spatial constraints, such as molds and scaffolds, or depend upon cell-driven organization that exploits endogenous innate developmental mechanisms. The multicellular, heterogeneous, and highly organized structure of hPSC constructs ultimately dictates the resulting form and function of in vitro engineered human tissue models