Dual Contribution of Mesenchymal Stem Cells Employed for Tissue Engineering of Peripheral Nerves: Trophic Activity and Differentiation into Connective-Tissue Cells.

Adult peripheral nerves in vertebrates can regrow their axons and re-establish function after crush lesion. However, when there is extensive loss of a nerve segment, due to an accident or compressive damage caused by tumors, regeneration is strongly impaired. In order to overcome this problem, bioengineering strategies have been employed, using biomaterials formed by key cell types combined with biodegradable polymers. Many of these strategies are successful, and regenerated nerve tissue can be observed 12 weeks after the implantation. Mesenchymal stem cells (MSCs) are one of the key cell types and the main stem-cell population experimentally employed for cell therapy and tissue engineering of peripheral nerves. The ability of these cells to release a range of different small molecules, such as neurotrophins, growth factors and interleukins, has been widely described and is a feasible explanation for the improvement of nerve regeneration. Moreover, the multipotent capacity of MSCs has been very often challenged with demonstrations of pluripotency, which includes differentiation into any neural cell type. In this study, we generated a biomaterial formed by EGFP-MSCs, constitutively covering microstructured filaments made of poly-ε-caprolactone. This biomaterial was implanted in the sciatic nerve of adult rats, replacing a 12-mm segment, inside a silicon tube. Our results showed that six weeks after implantation, the MSCs had differentiated into connective-tissue cells, but not into neural crest-derived cells such as Schwann cells. Together, present findings demonstrated that MSCs can contribute to nerve-tissue regeneration, producing trophic factors and differentiating into fibroblasts, endothelial and smooth-muscle cells, which compose the connective tissue.

Células-tronco e sua utilização na regeneração de nervo periférico - revisão / Stem cells and their use in the regeneration of peripheral nerve- review

Stem cells are undifferentiated cells with properties of self renewal, differentiation and proliferation. These properties are the subject of studies for the treatment of different diseases and the regeneration of damaged tissues and organs, among them, the peripheral nerves. Despite existing evidences that cell therapy helps peripheral nerve regeneration when associated with surgical techniques, the mechanisms by which this differentiation into nerve cells occurs remain unknown. Therefore, this paper presents an overview of the types pf stem cells and their peculiarities as well as the current research involving cell therapy on regeneration of severed nerve stumps.

As células-tronco são células indiferenciadas com propriedades de auto-renovação, diferenciação e proliferação.Estas propriedades as tornaram alvo de estudos para o tratamento de diferentes doenças e naregeneração de órgãos e tecidos lesionados, dentre eles, os nervos periféricos. Porém, apesar de existiremfortes indícios de que a terapia celular auxilia a regeneração nervosa periférica, quando associada a técnicascirúrgicas consagradas, ainda permanecem desconhecidos os mecanismos pelos quais a remodelaçãodo tecido nervoso ocorre. Assim, este trabalho apresenta uma revisão sobre os tipos de células-troncoe suas particularidades, bem como as atuais pesquisas envolvendo a terapia celular na regeneração decotos nervosos seccionados.

Células-tronco e sua utilização na regeneração de nervo periférico - revisão / Stem cells and their use in the regeneration of peripheral nerve- review

Stem cells are undifferentiated cells with properties of self renewal, differentiation and proliferation. These properties are the subject of studies for the treatment of different diseases and the regeneration of damaged tissues and organs, among them, the peripheral nerves. Despite existing evidences that cell therapy helps peripheral nerve regeneration when associated with surgical techniques, the mechanisms by which this differentiation into nerve cells occurs remain unknown. Therefore, this paper presents an overview of the types pf stem cells and their peculiarities as well as the current research involving cell therapy on regeneration of severed nerve stumps.(AU)

As células-tronco são células indiferenciadas com propriedades de auto-renovação, diferenciação e proliferação.Estas propriedades as tornaram alvo de estudos para o tratamento de diferentes doenças e naregeneração de órgãos e tecidos lesionados, dentre eles, os nervos periféricos. Porém, apesar de existiremfortes indícios de que a terapia celular auxilia a regeneração nervosa periférica, quando associada a técnicascirúrgicas consagradas, ainda permanecem desconhecidos os mecanismos pelos quais a remodelaçãodo tecido nervoso ocorre. Assim, este trabalho apresenta uma revisão sobre os tipos de células-troncoe suas particularidades, bem como as atuais pesquisas envolvendo a terapia celular na regeneração decotos nervosos seccionados.(AU)

DMT1 as a candidate for non-transferrin-bound iron uptake in the peripheral nervous system.

Iron, either in its chelated form or as holotransferrin (hTf), prevents the dedifferentiation of Schwann cells (SC), cells responsible for the myelination of the peripheral nervous system (PNS). This dedifferentiation is promoted by serum deprivation through cAMP release, PKA activation, and CREB phosphorylation. Since iron elicits its effect in a transferrin (Tf)-free environment, in this work we postulate that non-transferrin-bound iron (NTBI) uptake must be involved. Divalent metal transporter 1(DMT1) has been widely described in literature as a key player in iron metabolism, but never before in the PNS context. The presence of DMT1 was demonstrated in nerve homogenate, isolated adult-rat myelin, and cultured SC by Western Blot (WB) analysis and confirmed through its colocalization with S-100ß (SC marker) by immunocytochemical and immunohistochemical analyses. Furthermore, the existence of its mRNA was verified in sciatic nerve homogenate by RT-PCR and throughout SC maturational stages. Finally, we describe DMT1's subcellular location in the plasma membrane by confocal microscopy of SC and WB of different subcellular fractions. These data allow us to suggest the participation of DMT1 as part of a Tf independent iron uptake mechanism in SC and lead us to postulate a crucial role for iron in SC maturation and, as a consequence, in PNS myelination.

Peripheral antinociception induced by δ-opioid receptors activation, but not µ- or κ-, is mediated by Ca²âº-activated Cl⁻ channels.

Studies have demonstrated that the L-arginine/NO/cGMP pathway and the potassium and calcium channels are involved in the mechanisms underlying opioid receptor activation. As additional pathways may participate in the observed antinociceptive effects following opioid exposure, the aim of our study was to determine whether Ca(2+)-activated Cl(-) channels (CaCCs) are involved in peripheral antinociception induced by µ-, δ- and κ-opioid receptor activation. Hyperalgesia was induced by intraplantar injection of prostaglandin E(2) (PGE(2), 2 µg). Nociceptive thresholds to pressure (grams) were measured using an algesimetric apparatus 3h following injection. The µ-opioid receptor agonist morphine (200 µg), δ-opioid receptor agonist (+)-4-[(alphaR)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80, 80 µg), κ-opioid receptor agonist bremazocine (50 µg), CaCCs blocker niflumic acid (8-64 µg), CaCCs blocker 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB, 32-128 µg), nitric oxide donor sodium nitroprusside (SNP, 500 µg) and cGMP exogenous analogs dibutyryl cGMP (db-cGMP, 100 µg) were also administered into the paw. The CaCCs blocker niflumic acid and NPPB partially reversed the peripheral antinociception induced by exposure to the SNC80 in a dose-dependent manner. In contrast, niflumic acid did not modify the antinociceptive effect observed following exposure to morphine or bremazocine. Additionally, the peripheral antinociception induced by the NO donor SNP or by db-cGMP was not inhibited by niflumic acid. These results provide evidence for the involvement of CaCCs in the peripheral antinociception induced by SNC80. CaCCs activation does not appear to be involved when µ- and κ-opioid receptors are activated. In addition, we did not observe a link between CaCCs and the L-arginine/NO/GMPc pathway.