Sonic hedgehog signaling is required for sympathetic nervous system development

A systematic review and embryological perspective of pluripotent stem cell-derived autonomic postganglionic neuron differentiation for human disease modeling

Human autonomic neuronal cell models are emerging as tools for modeling diseases such as cardiac arrhythmias. In this systematic review, we compared 33 articles applying 14 different protocols to generate sympathetic neurons and 3 different procedures to produce parasympathetic neurons. All methods involved the differentiation of human pluripotent stem cells, and none employed permanent or reversible cell immortalization. Almost all protocols were reproduced in multiple pluripotent stem cell lines, and over half showed evidence of neural firing capacity. Common limitations in the field are a lack of three-dimensional models and models that include multiple cell types. Sympathetic neuron differentiation protocols largely mirrored embryonic development, with the notable absence of migration, axon extension, and target-specificity cues. Parasympathetic neuron differentiation protocols may be improved by including several embryonic cues promoting cell survival, cell maturation, or ion channel expression. Moreover, additional markers to define parasympathetic neurons in vitro may support the validity of these protocols. Nonetheless, four sympathetic neuron differentiation protocols and one parasympathetic neuron differentiation protocol reported more than two-thirds of cells expressing autonomic neuron markers. Altogether, these protocols promise to open new research avenues of human autonomic neuron development and disease modeling.

Inhibition of MicroRNA-195 Alleviates Neuropathic Pain by Targeting Patched1 and Inhibiting SHH Signaling Pathway Activation

Trigeminal neuralgia (TN) is a type of chronic neuropathic pain that is caused by peripheral nerve lesions that result from various conditions, including the compression of vessels, tumors and viral infections. MicroRNAs (miRs) are increasingly recognized as potential regulators of neuropathic pain. Previous evidence has demonstrated that miR-195 is involved in neuropathic pain, but the mechanism remains unclear. To investigate the pathophysiological role of miR-195 and Shh signaling in TN, persistent facial pain was induced by infraorbital nerve chronic constriction injury (CCI-IoN), and facial pain responses were evaluated by Von Frey hairs. qPCR and Western blotting were used to determine the relative expression of miR-195 and Patched1, the major receptor of the Sonic Hedgehog (Shh) signaling pathway, in the caudal brain stem at distinct time points after CCI-IoN. Here, we found that the expression of miR-195 was increased in a rat model of CCI-IoN. In contrast, the expression of Patched1 decreased significantly. Luciferase assays confirmed the binding of miR-195 to Patched1. In addition, the overexpression of miR-195 by an intracerebroventricular (i.c.v) administration of LV-miR-195 aggravated facial pain development, and this was reversed by upregulating the expression of Patched1. These results suggest that miR-195 is involved in the development of TN by targeting Patched1 in the Shh signaling pathway, thus regulating extracellular glutamate.

Human axial progenitors generate trunk neural crest cells in vitro

The neural crest (NC) is a multipotent embryonic cell population that generates distinct cell types in an axial position-dependent manner. The production of NC cells from human pluripotent stem cells (hPSCs) is a valuable approach to study human NC biology. However, the origin of human trunk NC remains undefined and current in vitro differentiation strategies induce only a modest yield of trunk NC cells. Here we show that hPSC-derived axial progenitors, the posteriorly-located drivers of embryonic axis elongation, give rise to trunk NC cells and their derivatives. Moreover, we define the molecular signatures associated with the emergence of human NC cells of distinct axial identities in vitro. Collectively, our findings indicate that there are two routes toward a human post-cranial NC state: the birth of cardiac and vagal NC is facilitated by retinoic acid-induced posteriorisation of an anterior precursor whereas trunk NC arises within a pool of posterior axial progenitors.

Functional Coupling with Cardiac Muscle Promotes Maturation of hPSC-Derived Sympathetic Neurons

Neurons derived from human pluripotent stem cells (hPSCs) are powerful tools for studying human neural development and diseases. Robust functional coupling of hPSC-derived neurons with target tissues in vitro is essential for modeling intercellular physiology in a dish and to further translational studies, but it has proven difficult to achieve. Here, we derive sympathetic neurons from hPSCs and show that they can form physical and functional connections with cardiac muscle cells. Using multiple hPSC reporter lines, we recapitulated human autonomic neuron development in vitro and successfully isolated PHOX2B::eGFP+ neurons that exhibit sympathetic marker expression and electrophysiological properties and norepinephrine secretion. Upon pharmacologic and optogenetic manipulation, PHOX2B::eGFP+ neurons controlled beating rates of cardiomyocytes, and the physical interactions between these cells increased neuronal maturation. This study provides a foundation for human sympathetic neuron specification and for hPSC-based neuronal control of organs in a dish.

Sonic hedgehog elevates N-myc gene expression in neural stem cells

Proliferation of neural stem cells is regulated by the secreted signaling molecule sonic hedgehog. In this study, neural stem cells were infected with recombinant adeno-associated virus expressing sonic hedgehog-N-enhanced green fluorescent protein. The results showed that overexpression of sonic hedgehog in neural stem cells induced the increased expression of Gli1 and N-myc, a target gene of sonic hedgehog. These findings suggest that N-myc is a direct downstream target of the sonic hedgehog signal pathway in neural stem cells. Sonic hedgehog and N-myc are important mediators of sonic hedgehog-induced proliferation of neural stem cells.