Differentiation of human pluripotent stem cells to small brain-like structures known as brain organoids offers an unprecedented opportunity to model human brain development and disease. To provide a vascularized and functional in vivo model of brain organoids, we established a method for transplanting human brain organoids into the adult mouse brain. Organoid grafts showed progressive neuronal differentiation and maturation, gliogenesis, integration of microglia, and growth of axons to multiple regions of the host brain. In vivo two-photon imaging demonstrated functional neuronal networks and blood vessels in the grafts. Finally, in vivo extracellular recording combined with optogenetics revealed intragraft neuronal activity and suggested graft-to-host functional synaptic connectivity. This combination of human neural organoids and an in vivo physiological environment in the animal brain may facilitate disease modeling under physiological conditions.

Transplantation studies in mice and rats have shown that human embryonic stem cell-derived cardiomyocytes (hESC-CMs) can improve the function of infarcted hearts1–3, but two critical issues related to their electrophysiological behavior in vivo remain unresolved. First, the risk of arrhythmias following hESC-CM transplantation in injured hearts has not been determined. Second, the electromechanical integration of hESC-CMs in injured hearts has not been demonstrated, so it is unclear if these cells improve contractile function directly through addition of new force-generating units. Here we use a guinea pig model to show hESC-CM grafts in injured hearts protect against arrhythmias and can contract synchronously with host muscle. Injured hearts with hESC-CM grafts show improved mechanical function and a significantly reduced incidence of both spontaneous and induced ventricular tachycardia (VT). To assess the activity of hESC-CM grafts in vivo, we transplanted hESC-CMs expressing the genetically-encoded calcium sensor, GCaMP34, 5. By correlating the GCaMP3 fluorescent signal with the host ECG, we found that grafts in uninjured hearts have consistent 1:1 host-graft coupling. Grafts in injured hearts are more heterogeneous and typically include both coupled and uncoupled regions. Thus, human myocardial grafts meet physiological criteria for true heart regeneration, providing support for the continued development of hESC-based cardiac therapies for both mechanical and electrical repair.

Background-Previous studies indicated that, in an acute myocardial infarction model, human embryonic stem cell-derived cardiomyocytes (hESC-CM) injected with a pro-survival cocktail (PSC) can preserve contractile function. Because patients with established heart failure may also benefit from cell transplantation, we evaluated the physiological effects of hESC-CM transplanted into a chronic model of myocardial infarction.

Plasmacytoid dendritic cells (pDCs) are the professional type I interferon (IFN)-producing cells, and upon activation they traffic to lymph organs, where they bridge innate and adaptive immunity. Using multianalyte profiling (MAP), we have mapped the key chemokines and cytokines produced in response to pDC activation, taking into consideration the role of autocrine IFN, as well as paracrine effects on other innate cells (e.g., monocytes and conventional DCs). Interestingly, we identify four distinct cytokine/chemokine loops initiated by Toll-like receptor engagement. Finally, we applied this analytic approach to the study of pDC activity in chronic hepatitis C patients. Based on the activation state of pDCs in fresh blood, the lack of agonistic activity of infectious virions, the production of a broad array of cytokines/chemokines once stimulated, and the direct effects of pDCs on other PBMCs, we conclude that the pDCs from hepatitis C virus (HCV)-infected individuals are fully functional and are, indeed, a viable drug target. In sum, this study provides insight into the use of MAP technology for characterizing cytokine networks, and highlights how a rare cell type integrates the activation of other inflammatory cells. Furthermore, this work will help evaluate the therapeutic application of pDC agonists in diseases such as chronic HCV infection.

In an infarcted rat model, myoblast transplantation but not bone marrow mononuclear cells or myocardial injection per se induces electrical ventricular instability. Because ventricular arrhythmias are life-threatening disorders, we suggest that such preclinical evaluation should be conducted for any new source of cells to be injected into the myocardium.

In addition to its effect on water permeability, vasopressin, through its V2 receptors (AVPR2), stimulates Na reabsorption in the collecting duct by increasing the activity of the amiloride-sensitive sodium channel ENaC. This study evaluated whether dDAVP (a potent AVPR2 agonist) reduces sodium excretion in healthy humans (n ‫؍‬ 6) and in patients with central (C; n ‫؍‬ 2) or nephrogenic (N) diabetes insipidus (DI) as a result of mutations of either the aquaporin 2 gene (AQP2; n ‫؍‬ 3) or AVPR2 (n ‫؍‬ 10). dDAVP was infused intravenously (0.3 g/kg body wt in 20 min), and urine was collected for 60 min before (basal) and 150 min after the infusion. dDAVP markedly reduced both urine flow rate and sodium excretion in healthy individuals. A reduction in sodium excretion was also observed in CDI and NDI-AQP2 patients but not in NDI-AVPR2 patients. The magnitude of the fall in sodium excretion correlated with the rise in urine osmolality and the fall in urine output but not with the simultaneously observed fall in mean BP. These results suggest that the dDAVP-induced antinatriuresis is due to a direct V2 receptor-dependent stimulation of sodium reabsorption in the collecting duct and is not secondary to a hemodynamic effect. In conclusion, this study reveals a potent V2-dependent antinatriuretic effect of vasopressin in humans. The possibility that an inappropriate stimulation of ENaC by vasopressin might lead to significant sodium retention in chronic situations remains to be determined. 16: 192016: -192816: , 200516: . doi: 10.1681 I nappropriate retention of sodium and water by the kidney is thought to be a key factor in several forms of hypertension. Thus, it is important to identify factors that may favor excessive sodium reabsorption by the kidney. Vasopressin is known to promote water conservation by increasing the permeability to water of the collecting ducts (CD), thus allowing osmotically driven water reabsorption along these ducts when dilute distal tubular fluid enters them in the cortex and later when they traverse the hyperosmotic medulla. However, the effect of vasopressin on sodium excretion is less clear. A large number of studies have shown that vasopressin infusion increases sodium excretion in vivo in rats, dogs, and sheep (e.g., references 1-4). This natriuretic effect is difficult to reconcile with the fact that, in vitro, vasopressin stimulates sodium reabsorption in the isolated perfused CD (5,6), in the amphibian bladder (a tissue that shares a number of similarities with the mammalian CD) (7), and in several cell lines issued from these two tissues (8 -10). This effect on sodium reabsorption is inhibitable by amiloride and has been shown to result from activation of the endothelial sodium channel ENaC (11). Moreover, chronic elevation of vasopressin or infusion of its V2 agonist dDAVP (12) has been shown to increase the abundance of mRNA (13) and protein (14) of the ␤ and ␥ subunits of ENaC and to enhance markedly the subsequent functional response (water and sodium reabsorption) to exoge...

Background Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) were recently shown to be capable of electromechanical integration following their direct injection into intact or recently injured guinea pig hearts, and hESC-CM transplantation in recently injured hearts correlated with improvements in contractile function and a reduction in the incidence of arrhythmias. The present study was aimed at determining the ability of hESC-CMs to integrate and modulate electrical stability following transplantation in a chronic model of cardiac injury. Methods & Results At 28 days following cardiac cryoinjury, guinea pigs underwent intra-cardiac injection of hESC-CMs, non-cardiac hESC-derivatives (non-CMs) or vehicle. Histology confirmed partial remuscularization of the infarct zone in hESC-CM recipients, while non-CM recipients showed heterogeneous xenografts. The three experimental groups showed no significant difference in the left ventricular dimensions or fractional shortening by echocardiography or in the incidence of spontaneous arrhythmias by telemetric monitoring. While recipients of hESC-CMs and vehicle showed a similar incidence of arrhythmias induced by programmed electrical stimulation at 4-weeks post-transplantation, non-CM recipients proved to be highly inducible, with a ~3-fold greater incidence of induced arrhythmias. In parallel studies, we investigated the ability of hESC-CMs to couple with host myocardium in chronically injured hearts by the intravital imaging of hESC-CM grafts that stably expressed a fluorescent reporter of graft activation, the genetically-encoded calcium sensor GCaMP3. In this work, we found that only ~38% (5 of 13) of recipients of GCaMP3+ hESC-CMs showed fluorescent transients that were coupled to the host electrocardiogram. Conclusions hESC-CMs engraft in chronically injured hearts without increasing the incidence of arrhythmias, but their electromechanical integration is more limited than was previously reported following their transplantation in a subacute injury model. Moreover, non-CM grafts may promote arrhythmias under certain conditions, a finding that underscores the need for input preparations of high cardiac purity.

SummaryCardiomyocytes derived from human embryonic stem cells (hESC-CMs) can improve the contractility of injured hearts. We hypothesized that mesodermal cardiovascular progenitors (hESC-CVPs), capable of generating vascular cells in addition to cardiomyocytes, would provide superior repair by contributing to multiple components of myocardium. We performed a head-to-head comparison of hESC-CMs and hESC-CVPs and compared these with the most commonly used clinical cell type, human bone marrow mononuclear cells (hBM-MNCs). In a nude rat model of myocardial infarction, hESC-CMs and hESC-CVPs generated comparable grafts. Both similarly improved systolic function and ventricular dilation. Furthermore, only rare human vessels formed from hESC-CVPs. hBM-MNCs attenuated ventricular dilation and enhanced host vascularization without engrafting long-term or improving contractility. Thus, hESC-CMs and CVPs show similar efficacy for cardiac repair, and both are more efficient than hBM-MNCs. However, hESC-CVPs do not form larger grafts or more significant numbers of human vessels in the infarcted heart.