Postganglionic sympathetic neurons and satellite glial cells are the two major cell types of the peripheral sympathetic ganglia. Sympathetic neurons project to and provide neural control of peripheral organs and have been implicated in human disorders ranging from cardiovascular disease to peripheral neuropathies. Here we show that satellite glia regulate synaptic activity of cultured postnatal sympathetic neurons, providing evidence for local ganglionic control of sympathetic drive. In addition to modulating neuron-to-neuron cholinergic neurotransmission, satellite glia promote synapse formation and contribute to neuronal survival. Examination of the cellular architecture of the rat sympathetic ganglia in vivo shows this regulation of neuronal properties takes place during a developmental period in which neuronal morphology and density are actively changing and satellite glia enwrap sympathetic neuronal somata. Cultured satellite glia make and release factors that promote neuronal activity and that can partially rescue the neurons from cell death following nerve growth factor deprivation. Thus, satellite glia play an early and ongoing role within the postnatal sympathetic ganglia, expanding our understanding of the contributions of local and targetderived factors in the regulation of sympathetic neuron function.

Satellite glial regulation of sympathetic activity" 15 16 17 18 40 Introduction 41 Glial cells, once thought of as neuron support cells, are now recognized as 42 active players in the formation and function of normal brain circuitry [1, 2]. 43 Astrocytes, the most abundant glial cell type in the brain, regulate many properties 44 of neuronal circuits such as neuronal excitability, synaptic transmission and 45 plasticity [3-5]. Their role at central nervous system (CNS) synapses has been the 46 focus of a number of studies in the past two decades, showing that astrocytes control 47 4 61 under pathological conditions such as hypertension and chronic heart disease [20, 62 21]. Sympathetic tone is initially set by neurons present in the brain and spinal cord 63 [22], with the sympathetic ganglionic neurons acting as the final regulatory element 64 determining the output of the sympathetic circuit. 65 A striking anatomical feature of the sympathetic ganglion is the presence of 66 satellite glia that form an envelope around individual ganglionic neuronal somata 67 and cover synapses [23]. This is in contrast to the CNS where individual astrocytes 68 are in contact with multiple neurons [24]. While the function of the satellite glia 69 remains to be fully defined, both sympathetic and sensory satellite glia share several 70 cellular and molecular features with astrocytes, including expression of 71 neurotransmitter receptors and the formation of a glia network via gap junctions 72 [25]. Satellite glia injury responses are characterized by changes in expression 73 profiles, including an up-regulation of the activation marker glial fibrillary acidic 74 protein (GFAP) [26]. These findings point to a possible effect in disease progression 75 and suggest that satellite glia play roles in both normal function and disease in the 76 peripheral nervous system. 77 Recent studies using genetic manipulations of sympathetic satellite glia have 78 implicated these cells in the regulation of target organ function by demonstrating 79 that selective activation of Gq-GPCR (G protein-coupled receptor) signaling in 80 peripheral glia leads to the modulation of cardiac properties in adult mice [27, 28]. 81 These effects are mediated through postganglionic sympathetic innervation of the 82 heart raising the possibility that activated glia influence the active properties of 157 in 4% paraformaldehyde (PFA) and then cryo-protected by incubating them in 30%

The Spontaneously Hypertensive Rat (SHR) has increased sympathetic drive to the periphery that precedes and contributes to the development of high blood pressure, making it a useful model for the study of neurogenic hypertension. Comparisons to the normotensive Wistar Kyoto (WKY) rat have demonstrated altered active and intrinsic properties of SHR sympathetic neurons shortly before the onset of hypertension. Here we examine the structural and functional plasticity of postnatal SHR and WKY sympathetic neurons cultured alone or co-cultured with cardiomyocytes under conditions of limited extrinsic signaling. SHR neurons have an increased number of structural synaptic sites compared to age-matched WKY neurons, measured by the co-localization of presynaptic vesicular acetylcholine transporter and postsynaptic shank proteins. Whole cell recordings show that SHR neurons have a higher synaptic charge than WKY neurons, demonstrating that the increase in synaptic sites is associated with increased synaptic transmission. Differences in synaptic properties are not associated with altered firing rates between postnatal WKY and SHR neurons and are not influenced by interactions with target cardiomyocytes from either strain. Both SHR and WKY neurons show tonic firing patterns in our cultures, which are depleted of non-neuronal ganglionic cells and provide limited neurotrophic signaling. This suggests that the normal mature, phasic firing of sympathetic neurons requires extrinsic signaling, with potentially differential responses in the prehypertensive SHR, which have been reported to maintain tonic firing at later developmental stages. While cardiomyocytes do not drive neuronal differences in our cultures, SHR cardiomyocytes display decreased hypertrophy compared to WKY cells and altered responses to co-cultured sympathetic neurons. These experiments suggest that altered signaling in SHR neurons and cardiomyocytes contributes to changes in the cardiac-sympathetic circuit in prehypertensive rats as early as the postnatal period.

Tissue engineering offers a promising treatment strategy for ureteral strictures, but its success requires an in-depth understanding of the architecture, cellular heterogeneity, and signaling pathways underlying tissue regeneration. Here we define and spatially map cell populations within the human ureter using single-cell RNA sequencing, spatial gene expression, and immunofluorescence approaches. We focused on the stromal and urothelial cell populations to enumerate distinct cell types composing the human ureter and inferred potential cell-cell communication networks underpinning the bi-directional crosstalk between these compartments. Furthermore, we analyzed and experimentally validated the importance of Sonic Hedgehog (SHH) signaling pathway in adult stem cell maintenance. The SHH-expressing basal cells supported organoid generation in vitro and accurately predicted the differentiation trajectory from basal stem cells to terminally differentiated umbrella cells. Our results highlight essential processes involved in adult ureter tissue homeostasis and provide a blueprint for guiding ureter tissue engineering.