Nogo-A does not inhibit retinal axon regeneration in the lizardGallotia galloti

The Potential of Aloe Vera in Solution and in Blended Nanofibers Containing Poly (3-Hydroxybutyrate-Co-3-Hydroxyvalerate) as Substrates for Neurite Outgrowth

This pilot study investigated the potential of aloe vera (AV) to promote neurite outgrowth in organotypic dorsal root ganglia (DRG) explants (n = 230) from neonatal rats (n = 15). Using this in vitro model of acute axotomy, we assessed neurite outgrowth exceeding 1.5 times the explant diameter (viable explants) and measured the longest neurite length. These parameters were evaluated under control conditions and in cultures supplemented with commercial AV and four aligned scaffolds: poly-L-lactate (PLLA), polydioxanone (PDS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and blended PHBV/AV. After 6 days of culture, explants were immunostained using neuron-specific marker Tuj1 and Schwann cell marker S100. Measurements were obtained with Image J software and analyzed using Jamovi 2.3. In control and AV dilution media, the study revealed radial tissue growth from the explant body with randomly oriented neurites, whereas in all scaffolds, bidirectional tissue growth occurred parallel to nanofibers. Binomial logistic regression analyses indicated that viable explants were more likely in the control group compared to PDS (p = 0.0042) and PHBV (p < 0.0001), with non-significant differences when compared to AV dilution, PLLA, and PHBV/AV. AV dilution showed a greater association with viable explants than PLLA (p = 0.0459), while non-significant difference was found between AV dilution and PHBV/AV. Additionally, the PHBV/AV scaffold predicted higher odds of viable explants than PLLA (p = 0.0479), PDS (p = 0.0001), and PHBV (p < 0.0001). Groups with similar probabilities of obtaining viable explants (control, AV dilution, and PHBV/AV) exhibited non-significant differences in their longest neurite lengths. In conclusion, control, AV dilution, and PHBV/AV yielded the highest probability of developing viable explants and the longest neurite lengths. This is the first study demonstrating the direct permissiveness of AV for axonal outgrowth. Furthermore, the blended PHBV/AV scaffold showed significant potential as a suitable scaffold for axonal regrowth and Schwann cell migration, ensuring controlled tissue formation for tissue engineering applications.

NOGO-A immunolabeling is present in glial cells and some neurons of the recovering lumbar spinal cord in lizards

The transected lumbar spinal cord of lizards was studied for its ability to recover after paralysis. At 34 days post-lesion about 50% of lizards were capable of walking with a limited coordination, likely due to the regeneration of few connecting axons crossing the transection site of the spinal cord. This region, indicated as "bridge", contains glial cells among which oligodendrocytes and their elongation that are immunolabeled for NOGO-A. A main reactive protein band occurs at 100-110 kDa but a weaker band is also observed around 240 kDa, suggesting fragmentation of the native protein due to extraction or to physiological processing of the original protein. Most of the cytoplasmic immunolabeling observed in oligodendrocytes is associated with vesicles of the endoplasmic reticulum. Also, the nucleus is labeled in some oligodendrocytes that are myelinating sparse axons observed within the bridge at 22-34 days post-transection. This suggests that axonal regeneration is present within the bridge region. Immunolabeling for NOGO-A shows that the protein is also present in numerous reactive neurons, in particular motor-neurons localized in the proximal stump of the transected spinal cord. Ultrastructural immunolocalization suggests that NOGO is synthesized in the ribosomes of these neurons and becomes associated with the cisternae of the endoplasmic reticulum, probably following a secretory pathway addressed toward the axon. The present observations suggest that, like for the regenerating spinal cord of fish and amphibians, also in lizard NOGO-A is present in reactive neurons and appears associated to axonal regeneration and myelination.

Fast direct neuronal signaling via the IL-4 receptor as therapeutic target in neuroinflammation

Ongoing axonal degeneration is thought to underlie disability in chronic neuroinflammation, such as multiple sclerosis (MS), especially during its progressive phase. Upon inflammatory attack, axons undergo pathological swelling, which can be reversible. Because we had evidence for beneficial effects of T helper 2 lymphocytes in experimental neurotrauma and discovered interleukin-4 receptor (IL-4R) expressed on axons in MS lesions, we aimed at unraveling the effects of IL-4 on neuroinflammatory axon injury. We demonstrate that intrathecal IL-4 treatment during the chronic phase of several experimental autoimmune encephalomyelitis models reversed disease progression without affecting inflammation. Amelioration of disability was abrogated upon neuronal deletion of IL-4R. We discovered direct neuronal signaling via the IRS1-PI3K-PKC pathway underlying cytoskeletal remodeling and axonal repair. Nasal IL-4 application, suitable for clinical translation, was equally effective in improving clinical outcome. Targeting neuronal IL-4 signaling may offer new therapeutic strategies to halt disability progression in MS and possibly also neurodegenerative conditions.

Tail regeneration and other phenomena of wound healing and tissue restoration in lizards

Wound healing is a fundamental evolutionary adaptation with two possible outcomes: scar formation or reparative regeneration. Scars participate in re-forming the barrier with the external environment and restoring homeostasis to injured tissues, but are well understood to represent dysfunctional replacements. In contrast, reparative regeneration is a tissue-specific program that near-perfectly replicates that which was lost or damaged. Although regeneration is best known from salamanders (including newts and axolotls) and zebrafish, it is unexpectedly widespread among vertebrates. For example, mice and humans can replace their digit tips, while many lizards can spontaneously regenerate almost their entire tail. Whereas the phenomenon of lizard tail regeneration has long been recognized, many details of this process remain poorly understood. All of this is beginning to change. This Review provides a comparative perspective on mechanisms of wound healing and regeneration, with a focus on lizards as an emerging model. Not only are lizards able to regrow cartilage and the spinal cord following tail loss, some species can also regenerate tissues after full-thickness skin wounds to the body, transections of the optic nerve and even lesions to parts of the brain. Current investigations are advancing our understanding of the biological requirements for successful tissue and organ repair, with obvious implications for biomedical sciences and regenerative medicine.

Differential metabolic profiles associated to movement behaviour of stream-resident brown trout (Salmo trutta)

The mechanisms that can contribute in the fish movement strategies and the associated behaviour can be complex and related to the physiology, genetic and ecology of each species. In the case of the brown trout (Salmo trutta), in recent research works, individual differences in mobility have been observed in a population living in a high mountain river reach (Pyrenees, NE Spain). The population is mostly sedentary but a small percentage of individuals exhibit a mobile behavior, mainly upstream movements. Metabolomics can reflect changes in the physiological process and can determine different profiles depending on behaviour. Here, a non-targeted metabolomics approach was used to find possible changes in the blood metabolomic profile of S. trutta related to its movement behaviour, using a minimally invasive sampling. Results showed a differentiation in the metabolomic profiles of the trouts and different level concentrations of some metabolites (e.g. cortisol) according to the home range classification (pattern of movements: sedentary or mobile). The change in metabolomic profiles can generally occur during the upstream movement and probably reflects the changes in metabolite profile from the non-mobile season to mobile season. This study reveals the contribution of the metabolomic analyses to better understand the behaviour of organisms.

Substrate properties of zebrafish Rtn4b/Nogo and axon regeneration in the zebrafish optic nerve

This study explored why lesioned retinal ganglion cell (RGC) axons regenerate successfully in the zebrafish optic nerve despite the presence of Rtn4b, the homologue of the rat neurite growth inhibitor RTN4-A/Nogo-A. Rat Nogo-A and zebrafish Rtn4b possess characteristic motifs (M1-4) in the Nogo-A-specific region, which contains delta20, the most inhibitory region of rat Nogo-A. To determine whether zebrafish M1-4 is inhibitory as rat M1-4 and Nogo-A delta20, proteins were recombinantly expressed and used as substrates for zebrafish single cell RGCs, mouse hippocampal neurons and goldfish, zebrafish and chick retinal explants. When offered as homogenous substrates, neurites of hippocampal neurons and of zebrafish single cell RGCs were inhibited by zebrafish M1-4, rat M1-4, and Nogo-A delta20. Neurite length increased when zebrafish single cell RGCs were treated with receptor-type-specific antagonists and, respectively, with morpholinos (MO) against S1PR2 and S1PR5a-which represent candidate zebrafish Nogo-A receptors. In a stripe assay, however, where M1-4 lanes alternate with polylysine-(Plys)-only lanes, RGC axons from goldfish, zebrafish, and chick retinal explants avoided rat M1-4 but freely crossed zebrafish M1-4 lanes-suggesting that zebrafish M1-4 is growth permissive and less inhibitory than rat M1-4. Moreover, immunostainings and dot blots of optic nerve and myelin showed that expression of Rtn4b is very low in tissue and myelin at 3-5 days after lesion when axons regenerate. Thus, Rtn4b seems to represent no major obstacle for axon regeneration in vivo because it is less inhibitory for RGC axons from retina explants, and because of its low abundance.