Graphene nanofiber composites for enhanced neuronal differentiation of human mesenchymal stem cells

Aim: To differentiate mesenchymal stem cells into functional dopaminergic neurons using an electrospun polycaprolactone (PCL) and graphene (G) nanocomposite. Methods: A one-step approach was used to electrospin the PCL nanocomposite, with varying G concentrations, followed by evaluating their biocompatibility and neuronal differentiation. Results: PCL with exiguous graphene demonstrated an ideal nanotopography with an unprecedented combination of guidance stimuli and substrate cues, aiding the enhanced differentiation of mesenchymal stem cells into dopaminergic neurons. These newly differentiated neurons were seen to exhibit unique neuronal arborization, enhanced intracellular Ca2+ influx and dopamine secretion. Conclusion: Having cost-effective fabrication and room-temperature storage, the PCL-G nanocomposites could pave the way for enhanced neuronal differentiation, thereby opening a new horizon for an array of applications in neural regenerative medicine.

Structural Brain Changes during the Neonatal Period in a Rabbit Model of Intrauterine Growth Restriction

Background: Intrauterine growth restriction (IUGR) is associated with abnormal neurodevelopment, but the associated structural brain changes are poorly documented. The aim of this study was to describe in an animal model the brain changes at the cellular level in the gray and white matter induced by IUGR during the neonatal period. Methods: The IUGR model was surgically induced in pregnant rabbits by ligating 40–50% of the uteroplacental vessels in 1 horn, whereas the uteroplacental vessels of the contralateral horn were not ligated. After 5 days, IUGR animals from the ligated horn and controls from the nonligated were delivered. On the day of delivery, perinatal data and placentas were collected. On postnatal day 1, functional changes were first evaluated, and thereafter, neuronal arborization in the frontal cortex and density of pre-oligodendrocytes, astrocytes, and microglia in the corpus callosum were evaluated. Results: Higher stillbirth in IUGR fetuses together with a reduced birth weight as compared to controls was evidenced. IUGR animals showed poorer functional results, an altered neuronal arborization pattern, and a decrease in the pre-oligodendrocytes, with no differences in microglia and astrocyte densities. Conclusions: Overall, in the rabbit model used, IUGR is related to functional and brain changes evidenced already at birth, including changes in the neuronal arborization and abnormal oligodendrocyte maturation.

Extrinsic repair of injured dendrites as a paradigm for regeneration by fusion

Injury triggers regeneration of axons and dendrites. Research identified factors required for axonal regeneration outside the CNS, but little is known about regeneration triggered by dendrotomy. Here we study neuronal plasticity triggered by dendrotomy and determine the fate of complex PVD arbors following laser surgery of dendrites. We find that severed primary dendrites grow towards each other and reconnect via branch fusion. Simultaneously, terminal branches lose self-avoidance and grow towards each other, meeting and fusing at the tips via an AFF-1-mediated process. Ectopic branch growth is identified as a step in the regeneration process required for bypassing the lesion site. Failure of reconnection to the severed dendrites results in degeneration of the distal end of the neuron. We discover pruning of excess branches via EFF-1 that acts to recover the original wild-type arborization pattern in a cell-autonomous process. In contrast, AFF-1 activity during dendritic auto-fusion is derived from the lateral seam cells and not autonomously from the PVD neuron. We propose a model in which AFF-1-vesicles derived from the epidermal seam cells fuse neuronal dendrites from without. Thus, EFF-1 and AFF-1 fusion proteins emerge as new players in neuronal arborization and maintenance of arbor connectivity following injury inC. elegans. Our results demonstrate that there is a genetically determined multi-step pathway to repair broken dendrites in which EFF-1 and AFF-1 act on different steps of the pathway. Intrinsic EFF-1 is essential for dendritic pruning after injury and extrinsic AFF-1 mediates dendrite fusion to bypass injuries.Author summaryNeurons in the central nervous system have very limited regenerative ability, they fail to remodel following amputation and only in some invertebrates, axons can repair themselves by fusion. Some genetic pathways have been identified for axonal regeneration but few studies exist on dendrite regeneration following injury. To determine how neurons regenerate dendrites following injury we study theC. elegansPVD polymodal neurons that display an arborized pattern of repetitive menorah-like structures. We injure dendrites by laser microsurgery, follow their fate and show that broken primary dendrites often regenerate via fusion. We describe how PVD dendrites regenerate and present roles for EFF-1 and AFF-1 proteins in fusion and remodeling of menorahs. Menorahs lose self-avoidance and AFF-1 fuses them, bypassing the injury site. Branch sprouting, EFF-1-mediated pruning, and arbor simplification completes regeneration. When auto-fusion fails the distal arbor degenerates. Surprisingly, AFF-1 acts non-cell autonomously to mediate dendrite fusion. We propose that extracellular vesicles derived from the lateral epidermis fuse severed dendrites in a process reminiscent of enveloped virus-mediated cell fusion without infection.