Hermetic Imagination: The Effect of The Golden Dawn on Fantasy Literature

The Hermetic Order of the Golden Dawn was an English expression of the Nineteenth-Century occult revival in Europe. Dedicated to such practices as ceremonial magic and divination, it valued these more as gateways to true understanding of reality than for their intrinsic merit. The Golden Dawn’s essentially Neoplatonic world-view is reflected in the writings of such some-time members as W.B. Yeats, Arthur Machen and Charles Williams

Enhanced Electrical Integration of Engineered Human Myocardium via Intramyocardial versus Epicardial Delivery in Infarcted Rat Hearts.

Cardiac tissue engineering is a promising approach to provide large-scale tissues for transplantation to regenerate the heart after ischemic injury, however, integration with the host myocardium will be required to achieve electromechanical benefits. To test the ability of engineered heart tissues to electrically integrate with the host, 10 million human embryonic stem cell (hESC)-derived cardiomyocytes were used to form either scaffold-free tissue patches implanted on the epicardium or micro-tissue particles (~1000 cells/particle) delivered by intramyocardial injection into the left ventricular wall of the ischemia/reperfusion injured athymic rat heart. Results were compared to intramyocardial injection of 10 million dispersed hESC-cardiomyocytes. Graft size was not significantly different between treatment groups and correlated inversely with infarct size. After implantation on the epicardial surface, hESC-cardiac tissue patches were electromechanically active, but they beat slowly and were not electrically coupled to the host at 4 weeks based on ex vivo fluorescent imaging of their graft-autonomous GCaMP3 calcium reporter. Histologically, scar tissue physically separated the patch graft and host myocardium. In contrast, following intramyocardial injection of micro-tissue particles and suspended cardiomyocytes, 100% of the grafts detected by fluorescent GCaMP3 imaging were electrically coupled to the host heart at spontaneous rate and could follow host pacing up to a maximum of 300-390 beats per minute (5-6.5 Hz). Gap junctions between intramyocardial graft and host tissue were identified histologically. The extensive coupling and rapid response rate of the human myocardial grafts after intramyocardial delivery suggest electrophysiological adaptation of hESC-derived cardiomyocytes to the rat heart's pacemaking activity. These data support the use of the rat model for studying electromechanical integration of human cardiomyocytes, and they identify lack of electrical integration as a challenge to overcome in tissue engineered patches

Stromal cells in dense collagen promote cardiomyocyte and microvascular patterning in engineered human heart tissue

Cardiac tissue engineering is a strategy to replace damaged contractile tissue and model cardiac diseases to discover therapies. Current cardiac and vascular engineering approaches independently create aligned contractile tissue or perfusable vasculature, but a combined vascularized cardiac tissue remains to be achieved. Here, we sought to incorporate a patterned microvasculature into engineered heart tissue, which balances the competing demands from cardiomyocytes to contract the matrix versus the vascular lumens that need structural support. Low-density collagen hydrogels (1.25 mg/mL) permit human embryonic stem cell-derived cardiomyocytes (hESC-CMs) to form a dense contractile tissue but cannot support a patterned microvasculature. Conversely, high collagen concentrations (density ≥6 mg/mL) support a patterned microvasculature, but the hESC-CMs lack cell-cell contact, limiting their electrical communication, structural maturation, and tissue-level contractile function. When cocultured with matrix remodeling stromal cells, however, hESC-CMs structurally mature and form anisotropic constructs in high-density collagen. Remodeling requires the stromal cells to be in proximity with hESC-CMs. In addition, cocultured cardiac constructs in dense collagen generate measurable active contractions (on the order of 0.1 mN/mm) and can be paced up to 2 Hz. Patterned microvascular networks in these high-density cocultured cardiac constructs remain patent through 2 weeks of culture, and hESC-CMs show electrical synchronization. The ability to maintain microstructural control within engineered heart tissue enables generation of more complex features, such as cellular alignment and a vasculature. Successful incorporation of these features paves the way for the use of large scale engineered tissues for myocardial regeneration and cardiac disease modeling

Formation of hESC-derived cardiac engineered tissues.

<p>(A) hESCs are differentiated into cardiomyocytes with high efficiency as characterized by flow cytometry analysis. An example cell population (85.5% single cell population, left) shows 81% expression of cardiac troponin T (cTnT, PE fluorescence, right) relative to isotype control (not shown). (B) Micro-tissue particles (MTPs) are formed by seeding approximately 1000 cells per microwell (left) and are easily removed from molds by a gentle media wash (right). (C) <i>In vitro</i> characterization of MTPs indicates highly defined particle diameter based on cell input number. (D) Cardiac engineered tissues have high cardiac purity as indicated by β-myosin heavy chain (β-MHC; brown, DAB) in MTPs (top) and cardiac patches (bottom). (E) Cardiac purity by β-MHC staining shows increasing purity with culture time. * P < 0.05 versus Day 1.</p

Intramyocardial implants have connexin 43-positive junctions with host cardiomyocytes.

<p>Evidence of connexin 43-positive gap junction formation between host cardiomyocytes and hESC-cardiomyocyte grafts was found for cell grafts (A) and micro-tissue particle grafts (B). Boxed region in left column is shown at 4-fold magnification in the right column, highlighting the junctions between graft and host (white arrow heads). Patch implants showed connexin 43-positive regions within the patch (boxed region and right column) and no evidence of gap junction formation with the host, as hESC-cardiomyocytes were physically separated from the host myocardium by scar tissue (C). g, graft; s, scar, h, host. Scale bar = 50 μm.</p

Summary of hESC-cardiomyocyte engraftment at 4 weeks by histology and <i>ex vivo</i> fluorescent imaging.

<p>No significant differences exist between treatment groups. MCR, maximum capture rate; NA, not applicable.</p

Excitation response of stimulated hESC-cardiomyocytes in 2D culture <i>in vitro</i>.

<p>Spontaneous contraction rate was higher at 2 weeks with pacing at 1 and 6 Hz (*P < 0.05). Similarly, excitation threshold (ET) was significantly lower after 2 weeks of 1 and 6 Hz electrical pacing compared to unstimulated control. However, maximum capture rate (MCR) was not different among groups at any time point and all significant differences are lost after 4 weeks in culture.</p