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The goal of this work was to design a polymer-based platform capable of localized, long-term delivery of biologically active neurotropic factors using an affinity-based approach. Here, we synthesized hyaluronic acid-methylfuran (HA-mF) hydrogels that provide sustained, affinity-based release of neurotrophin-3 (NT-3), a growth factor that promotes axon growth for 28 days. A Diels-Alder crosslinking reaction between HA-mF and polyethylene glycol (PEG)-dimaleimide occurs within 15 min under physiological conditions, resulting in hydrogels that can be polymerized in the presence of cells and growth factors. We also tuned the hydrogel's storage modulus to match that of native rat spinal cord tissue, providing a platform not only for localized drug delivery but also a suitable vehicle for cellular transplantation. The NT-3 released from the HAmF hydrogels remains bioactive for at least 14 days, promoting axonal growth from primary sensory neurons as well as stem cell-derived V2a interneurons and motoneurons in vitro. The hydrogels also supported cell growth allowing for 3-dimensional axonal extensions within the scaffold matrix. Here we confirm the protective role of HA-mF on matrix-bound NT-3 activity and show that these hydrogels are an excellent platform for growth factor delivery for neural applications., (© 2023 Wiley Periodicals LLC.)

Brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) are known to regulate neuronal morphology and the formation of neural circuits, yet the neuronal targets of each neurotrophin are still to be defined. To address how these neurotrophins regulate the morphological and synaptic differentiation of developing olfactory bulb (OB) GABAergic interneurons, we analyzed the effect of BDNF and NT-3 on GABA + -neurons and on different subtypes of these neurons: tyrosine hydroxylase (TH + ); calretinin (Calr + ); calbindin (Calb + ); and parvalbumin (PVA + ). These cells were generated from cultured embryonic mouse olfactory bulb neural stem cells (eOBNSCs) and after 14 days in vitro (DIV), when the neurons expressed TrkB and/or TrkC receptors, BDNF and NT-3 did not significantly change the number of neurons. However, long-term BDNF treatment did produce a longer total dendrite length and/or more dendritic branches in all the interneuron populations studied, except for PVA + -neurons. Similarly, BDNF caused an increase in the cell body perimeter in all the interneuron populations analyzed, except for PVA + -neurons. GABA + - and TH + -neurons were also studied at 21 DIV, when BDNF produced significantly longer neurites with no clear change in their number. Notably, these neurons developed synaptophysin + boutons at 21 DIV, the size of which augmented significantly following exposure to either BDNF or NT-3. Our results show that in conditions that maintain neuronal survival, BDNF but not NT-3 promotes the morphological differentiation of developing OB interneurons in a cell-type-specific manner. In addition, our findings suggest that BDNF and NT-3 may promote synapse maturation by enhancing the size of synaptic boutons., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.)

Neurotrophin-3 enhances the effectiveness of human olfactory ensheathing cells in improving hind limb mobility in rats with post-traumatic cysts of the spinal cord. Transplantation of olfactory ensheathing cells into spinal cord cysts reduced their size; neurotrophin-3 did not modulate this effect. Combined preparation of human olfactory ensheathing cells and neurotrophin- 3 can be used in neurosurgery for the treatment of patients with spinal cord injuries., (© 2022. Springer Science+Business Media, LLC, part of Springer Nature.)

Background and Purpose: Stroke therapy still lacks successful measures to improve post stroke recovery. Neurotrophin-3 (NT-3) is one promising candidate which has proven therapeutic benefit in motor recovery in acute experimental stroke. Post stroke, the immune system has opposing pathophysiological roles: pro-inflammatory cascades and immune cell infiltration into the brain exacerbate cell death while the peripheral immune response has only limited capabilities to fight infections during the acute and subacute phase. With time, anti-inflammatory mechanisms are supposed to support recovery of the ischemic damage within the brain parenchyma. However, interestingly, NT-3 can improve recovery in chronic neurological injury when combined with the pro-inflammatory stimulus lipopolysaccharide (LPS)., Aim: We elucidated the impact of NT-3 on human monocyte and T cell activation as well as cytokine production ex vivo after stroke. In addition, we investigated the age-dependent availability of the high affinity NT-3 receptor TrkC upon LPS stimulation., Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from acute stroke patients and controls and incubated with different dosages of NT-3 (10 and 100 ng/mL) and with or without LPS or anti-CD3/CD28 for 48 h. Total TrkC expression and cell activation (CD25, CD69 and HLA-DR) were assessed by FACS staining. IFN-γ, TNF-α, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17F, IL-21 and IL-22 were quantified by cytometric bead array., Results: Most monocytes and only a small proportion of T cells expressed TrkC in blood from humans without stroke. Activation of cells from young humans (without strokes) using anti-CD3/CD28 or LPS partially reduced the proportion of monocytes expressing TrkC whilst they increased the proportion of T cells expressing TrkC. In contrast, activation of cells from elderly humans (without strokes) did not affect the proportion of monocytes expressing TrkC and only anti-CD3/CD28 led to an increase in the proportion of CD4+ T cells expressing TrkC. In blood from stroke patients or controls, NT-3 treatment reduced the percentage of monocytes and CD4+ and CD8+ T cells that were activated and reduced all cytokines investigated besides IL-21., Conclusions: NT-3 attenuated immune responses in cells from stroke patients and controls. The mechanism whereby human immune cells respond to NT-3 may be via TrkC receptors whose levels are regulated by stimulation. Further work is required to determine whether the induction of sensorimotor recovery in rodents by NT-3 after CNS injury is caused by this attenuation of the immune response., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

This study prepared a novel three-dimensional nanocomposite scaffold by the surface modification of PCL/chitosan nanofiber/net with alginate hydrogel microlayer, hoping to have the privilege of both nanofibers and hydrogels simultaneously. Bead free randomly oriented nanofiber/net (NFN) structure composed of chitosan and polycaprolactone (PCL) was fabricated by electrospinning method. The low surface roughness, good hydrophilicity, and high porosity were obtained from the NFN structure. Then, the PCL/chitosan nanofiber/net was coated with a microlayer of alginate containing neurotrophin-3 (NT-3) and conjunctiva mesenchymal stem cells (CJMSCs) as a new stem cell source. According to the cross-sectional FESEM, the scaffold shows a two-layer structure with interconnected pores in the range of 20 μm diameter. The finding revealed that the surface modification of nanofiber/net by alginate hydrogel microlayer caused lower inflammatory response and higher proliferation of CJMSCs than the unmodified scaffold. The initial burst release of NT-3 was 69% in 3 days which followed by a sustained release up to 21 days. The RT-PCR analysis showed that the expression of Nestin, MAP-2, and β-tubulin III genes were increased 6, 5.4, and 8.8-fold, respectively. The results revealed that the surface-modified biomimetic scaffold possesses enhanced biocompatibility and could successfully differentiate CJMSCs to the neuron-like cells., (© 2021 Wiley Periodicals LLC.)