ABSTRACT
BACKGROUND & AIMS: The enteric nervous system (ENS) is the largest branch of the peripheral nervous system, comprising complex networks of neurons and glia, which are present throughout the gastrointestinal tract. Although development of a fully functional ENS is required for gastrointestinal motility, little is known about the ontogeny of ENS function in humans. We studied the development of neuronal subtypes and the emergence of evoked electrical activity in the developing human ENS. METHODS: Human fetal gut samples (obtained via the MRC-Wellcome Trust Human Developmental Biology Resource-UK) were characterized by immunohistochemistry, calcium imaging, RNA sequencing, and quantitative real-time polymerase chain reaction analyses. RESULTS: Human fetal colon samples have dense neuronal networks at the level of the myenteric plexus by embryonic week (EW) 12, with expression of excitatory neurotransmitter and synaptic markers. By contrast, markers of inhibitory neurotransmitters were not observed until EW14. Electrical train stimulation of internodal strands did not evoke activity in the ENS of EW12 or EW14 tissues. However, compound calcium activation was observed at EW16, which was blocked by the addition of 1 µmol/L tetrodotoxin. Expression analyses showed that this activity was coincident with increases in expression of genes encoding proteins involved in neurotransmission and action potential generation. CONCLUSIONS: In analyses of human fetal intestinal samples, we followed development of neuronal diversity, electrical excitability, and network formation in the ENS. These processes are required to establish the functional enteric circuitry. Further studies could increase our understanding of the pathogenesis of a range of congenital enteric neuropathies.
Subject(s)
Colon/innervation , Enteric Nervous System/physiology , Evoked Potentials , Nerve Net/physiology , Neurogenesis , Neurons/physiology , Calcium Signaling , Colon/embryology , Electric Stimulation , Enteric Nervous System/drug effects , Enteric Nervous System/embryology , Evoked Potentials/drug effects , Female , Gene Expression Regulation, Developmental , Gestational Age , Humans , Nerve Net/drug effects , Nerve Net/embryology , Neurogenesis/drug effects , Neurogenesis/genetics , Neurons/drug effects , Neurotransmitter Agents/pharmacology , Phenotype , Pregnancy , Pregnancy Trimester, Second , Synaptic TransmissionABSTRACT
Cardiovascular disease, the leading cause of death worldwide, is predominantly associated with atherosclerosis. Atherosclerosis is a chronic inflammatory disease characterised by the narrowing of large to medium-sized arteries due to a build-up of plaque. Atherosclerotic plaque is comprised of lipids, extracellular matrix, and several cell types, including endothelial, immune, and vascular smooth muscle cells. Such narrowing of the blood vessels can itself restrict blood flow to vital organs but most severe clinical complications, including heart attacks and strokes, occur when lesions rupture, triggering the blood to clot and obstructing blood flow further down the vascular tree. To circumvent such obstructions, percutaneous coronary intervention or bypass grafts are often required; however, re-occlusion of the treated artery frequently occurs. Neuropilins (NRPs), a multifunctional family of cell surface co-receptors, are expressed by endothelial, immune, and vascular smooth muscle cells and are regulators of numerous signalling pathways within the vasculature. Here, we review recent studies implicating NRP2 in the development of occlusive vascular diseases and discuss how NRP2 could be targeted for therapeutic intervention.