Epigenetic control of myeloid cells behavior by Histone Deacetylase activity (HDAC) during tissue and organ regeneration in Xenopus laevis.

In the present work we have focused on the Histone Deacetylase (HDAC) control of myeloid cells behavior during Xenopus tail regeneration. Here we show that myeloid differentiation is crucial to modulate the regenerative ability of Xenopus tadpoles in a HDAC activity-dependent fashion. HDAC activity inhibition during the first wave of myeloid differentiation disrupted myeloid cells dynamics in the regenerative bud as well the mRNA expression pattern of myeloid markers, such as LURP, MPOX, Spib and mmp7. We also functionally bridge the spatial and temporal dynamics of lipid droplets, the main platform of lipid mediators synthesis in myeloid cells during the inflammatory response, and the regenerative ability of Xenopus tadpoles. In addition, we showed that 15-LOX activity is necessary during tail regeneration. Taken together our results support a role for the epigenetic control of myeloid behavior during tissue and organ regeneration, which may positively impact translational approaches for regenerative medicine.

Inosine Accelerates the Regeneration and Anticipates the Functional Recovery after Sciatic Nerve Crush Injury in Mice.

Trauma to the peripheral nervous system (PNS) results in loss of motor and sensory functions. After an injury, a complex series of events begins, allowing axonal regeneration and target reinnervation. However, this regenerative potential is limited by several factors such as age, distance from the lesion site to the target and severity of lesion. Many studies look for ways to overcome these limitations. Inosine, a purine nucleoside derived from adenosine, emerges as a potential treatment, due to its capacity to regulate axonal growth, neuroprotection and immunomodulation, contributing to motor recovery. However, no studies demonstrated their effects on PNS. C57/Black6 mice were submitted to sciatic nerve crush and received intraperitoneal injections of saline or inosine (70 mg/kg), one hour after injury and daily for one week. To evaluate axonal regeneration and functional recovery, electroneuromyography, Sciatic Function Index (SFI), rotarod and pinprick tests were performed. Our results showed that the inosine group presented a higher number of myelinated fibers and a large amount of fibers within the ideal G-ratio. In addition, the results of electroneuromyography showed greater amplitude of the compound muscle action potentials in the first and second weeks, suggesting anticipation of regeneration in the inosine group. We also observed in the inosine group, motor and sensory neurons survival, reduction in the number of macrophages and myelin ovoids in the sciatic nerves, and an early recovery of motor and sensory functions. Thus, we conclude that the use of inosine accelerates axonal regeneration promoting an early recovery of motor and sensory functions.

Effects of Different Doses of Mesenchymal Stem Cells on Functional Recovery After Compressive Spinal-Cord Injury in Mice.

Despite advances in technology and rehabilitation, no effective therapies are available for patients with SCI, which remains a major medical challenge. This study compared the efficacy of 3 different doses of mesenchymal stem cells (MSCs) administered by intraperitoneal injection as a therapeutic strategy for compressive SCI. We used adult female C57BL/6 mice that underwent laminectomy at the T9 level, followed by spinal-cord compression for 1 min with a 30-g vascular clip. The animals received an intraperitoneal (i.p.) injection of MSCs (8 × 104, 8 × 105 or 8 × 106 in 500 µl) or DMEM (500 µl), one week after SCI. The cells of the three MSC doses administered i.p. were able to migrate to the injury site, increase local expression of trophic factors, and enhance fiber sparing and/or regeneration, accompanied by substantial improvement in locomotor performance. Cell transplantation at 8 × 105 density showed the best therapeutic potential, leading to significant tissue and functional improvements compared to the other two doses. These findings indicate that i.p. application of MSCs at the density of 8 × 105 yielded the best results, suggesting that this dose is a good choice for SCI treatment.

NH36 and F3 Antigen-Primed Dendritic Cells Show Preserved Migrating Capabilities and CCR7 Expression and F3 Is Effective in Immunotherapy of Visceral Leishmaniasis.

Physical contact between dendritic cells (DCs) and T cell lymphocytes is necessary to trigger the immune cell response. CCL19 and CCL21 chemokines bind to the CCR7 receptor of mature DCs, and of T cells and regulate DCs migration to the white pulp (wp) of the spleen, where they encounter lymphocytes. In visceral leishmaniasis (VL), cellular immunosuppression is mediated by impaired DC migration due to the decreased chemokine secretion by endothelium and to the reduced DCs CCR7 expression. The Leishmania (L.) donovani nucleoside hydrolase NH36 and its C-terminal domain, the F3 peptide are prominent antigens in the generation of preventive immunity to VL. We assessed whether these vaccines could prevent the migrating defect of DCs by restoring the expression of CCR7 receptors. C57Bl6 mice were vaccinated with NH36 and F3 and challenged with L. (L.) infantum chagasi. The F3 vaccine induced a 100% of survival and a long-lasting immune protection with an earlier CD4+Th1 response, with secretion of higher IFN-γ and TNF-α/IL-10 ratios, and higher frequencies of CD4+ T cells secreting IL-2+, TNF-α+, or IFN-γ+, or a combination of two or the three cytokines (IL-2+TNF-α+IFN-γ+). The CD8+ T cell response was promoted earlier by the NH36-vaccine, and later by the F3-vaccine. Maximal number of F3-primed DCs migrated in vitro in response to CCL19 and showed a high expression of CCR7 receptors (26.06%). Anti-CCR7 antibody treatment inhibited DCs migration in vitro (90%) and increased parasite load in vivo. When transferred into 28-day-infected mice, only 8% of DCs from infected, 59% of DCs from NH36-vaccinated, and 84% of DCs from F3-vaccinated mice migrated to the wp. Consequently, immunotherapy of infected mice with F3-primed DCs only, promoted increases in corporal weight and reductions of spleen and liver parasite loads and relative weights. Our findings indicate that vaccination with F3-vaccine preserves the maturation, migration properties and CCR7 expression of DCs, which are essential processes for the generation of cell-mediated immunity. The F3 vaccine is more potent in reversing the migration defect that occurs in VL and, therefore, more efficient in immunotherapy of VL.