Maddalena Ravasi

NGF protects Dorsal Root Ganglion neurons from oxaliplatin by modulating JNK/Sapk and ERK1/2

The involvement of the Mitogen-Activated Protein Kinases (MAPKs) family in platinum derivative-induced peripheral neuropathy has already been demonstrated. In particular, it has been evidenced that in Dorsal Root Ganglion (DRG) neurons prolonged exposure to oxaliplatin (OHP) induces early activation of p38 and ERK1/2, which mediate neuronal apoptosis, while the neuroprotective action of JNK/Sapk is downregulated by the drug treatment. In this study, the exposure of OHP-treated neurons to a neuroprotective stimulus, represented by a high dose of NGF, counteracts OHP-induced neuronal mortality. This effect was achieved by restoring the MAPK activation existing in untreated control cells. Increased viability occurred also after the administration of retinoic acid (RA), a pro-differentiative agent able to activate both JNK/Sapk and ERK1/2. The use of specific chemical inhibitors of MAPKs confirms the importance of this class of proteins for the neuroprotective pathway, since they reverse the protective effect. In summary, our findings assess the validity of MAPKs as the target of neuroprotective therapies during chemotherapeutic treatment. Moreover they also describe a double role for ERK1/2, depending on cellular stimulation, since it mediates neuronal apoptosis after OHP exposure. However, it is also important, as is JNK/Sapk, in preserving the correct cellular differentiation that is pivotal for neuronal survival.

Adult mesenchymal stem cells support cisplatin-treated dorsal root ganglion survival

Mesenchymal stem cells (MSCs) have been found to be useful in the management of different models of neurological diseases. In the present study, we tested the possible protective effect of MSCs on sensory dorsal root ganglia (DRG) explants exposed to the toxic effect of CDDP, a widely used anticancer drug. DRG explants cultured on a collagen layer and exposed to NGF for 2h (differentiating neurons) or for 5 days (fully differentiated neurons) were treated with CDDP and subsequently co-cultured with MSCs. MSCs were able to support the survival of both differentiating and fully differentiated DRG neurons up to 2 months after the drug treatment, reducing the CDDP-induced death of DRG neurons. MSCs were, however, unable to restore the correct length of DRG neurites compromised by CDDP treatment. The positive effect on neuronal survival was exerted through the contact between DRG and MSCs, and not mediated by neurotrophic factors released by the MSCs. Our observations could represent a starting point for designing a neuroprotective strategy to limit CDDP induced neuropathy without interfering with its anticancer properties.

Neurobasal medium toxicity on mature cortical neurons.

Neurobasal medium (NBM) is a widely used medium for neuronal cultures, originally formulated to support survival of rat hippocampal neurons, but then optimized for several other neuronal subtypes. In the present study, the toxic effect of NBM on long-term cortical neuron cultures has been reported and investigated. A significant neuronal cell loss was observed 24 h after the total medium change performed at days in vitro 10. The neurotoxic effect was specifically because of NBM-A, a commercially derived modification of classic NBM, as neurons exposed to minimum essential medium for 24 h did not show the same mortality rate. We showed that the toxic effect was mediated by the N-methyl-D-aspartate receptor (NMDAr) as its inactivation partly prevented NBM-induced neuronal loss, and the addition of NMDAr activators, such as L-cysteine or glycine to minimum essential medium, reproduced the same toxicity rate observed in NBM. Besides the toxicity associated with NMDAr activation, the decreased antioxidative defenses also worsen (because of glutathione depletion) neuronal death, thus amplifying the effect of excitotoxic amino acids. Indeed, glutathione supplementation by the addition of its precursor N-acetyl-cysteine resulted in an increase in neuronal survival that partially prevented NBM-A toxicity. These results evidenced, on the one hand, the unsuitability of NBM-A for long-term neuronal culture, and on the other, they highlight the importance of selection of more suitable culture conditions.

Undifferentiated MSCs are able to myelinate DRG neuron processes through p75

Over the last few years the therapeutic approach to demyelinating diseases has radically changed, strategies having been developed aimed at partnering the classic symptomatic treatments with the most advanced regenerative medicine tools. At first, the transplantation of myelinogenic cells, Schwann cells or oligodendrocytes was suggested, but the considerable technical difficulties, (poor availability, difficulties in harvesting and culturing, and the problem of rejection in the event of non-autologous sources), shifted attention towards more versatile cellular types, such as Mesenchymal Stem Cells (MSCs). Recent studies have already demonstrate both in vitro and in vivo that glially-primed MSCs (through exposure to chemical cocktails) have myelogenic abilities. In spite of a large number of papers on glially-differentiated MSCs, little is known about the ability of undifferentiated MSCs to myelinate axons and processes. Here we have demonstrated that also undifferentiated MSCs have the ability to myelinate, since they induce the myelination of rat DRG neuron processes after direct co-culturing. In this process a pivotal role is performed by the p75 receptor.

Comparing the different response of PNS and CNS injured neurons to mesenchymal stem cell treatment

Abstract Mesenchymal stem cells (MSCs) are adult bone marrow‐derived stem cells actually proposed indifferently for the therapy of neurological diseases of both the Central (CNS) and the Peripheral Nervous System (PNS), as a panacea able to treat so many different diseases by their immunomodulatory ability and supportive action on neuronal survival. However, the identification of the exact mechanism of MSC action in the different diseases, although mandatory to define their real and concrete utility, is still lacking. Moreover, CNS and PNS neurons present many different biological properties, and it is still unclear if they respond in the same manner not only to MSC treatment, but also to injuries. For these reasons, in this study we compared the susceptibility of cortical and sensory neurons both to toxic drug exposure and to MSC action, in order to verify if these two neuronal populations can respond differently. Our results demonstrated that Cisplatin (CDDP), Glutamate, and Paclitaxel‐treated sensory neurons were protected by the co‐culture with MSCs, in different manners: through direct contact able to block apoptosis for CDDP‐ and Glutamate‐treated neurons, and by the release of trophic factors for Paclitaxel‐treated ones. A possible key soluble factor for MSC protection was Glutathione, spontaneously released by these cells. On the contrary, cortical neurons resulted more sensitive than sensory ones to the toxic action of the drugs, and overall MSCs failed to protect them. All these data identified for the first time a different susceptibility of cortical and sensory neurons, and demonstrated a protective action of MSCs only against drugs in peripheral neurotoxicity. HighlightsCNS neurons and PNS neurons have a different susceptibility to neurotoxic drugs.Direct contact and soluble factor release were involved in MSCs’ protective effect.MSCs protect sensory neurons but fail to protect cortical neurons from drugs toxicity.

Positive effect of Mesenchymal Stem Cells therapeutic administration on chronic Experimental Autoimmune Encephalomyelitis

Multiple Sclerosis (MS) is a crippling chronic disease of the Central Nervous System caused by the presence of self-antibodies which progressively damage axonal myelin sheath, leading to axonal transmission impairment and to the development of neurological symptoms. MS is characterized by a Relapsing-Remitting course, and current therapies rely only on the use of immunosuppressive drugs, which are however unable to reverse disease progression. Encouraging results have been obtained in preclinical studies with the administration of Mesenchymal Stem Cells (MSCs) before disease onset (Zappia et al., 2005). Here, we investigate the therapeutic potential of MSC administration after disease onset into an animal model of MS, represented by Dark Agouti rats affected by chronic Relapsing-Remitting Experimental Autoimmune Encephalomyelitis (EAE) (Cavaletti et al., 2004). 106 MSC were intravenously injected in EAE rats after disease onset. Clinical score was assessed daily, and after 45 days rats were sacrificed and histological analysis of spinal cords performed to evaluate the demyelinating lesions. After the first peak of disease, no further relapses were observed in EAE rats treated with MSCs, differently from what observed in EAE group. Histological analysis demonstrated the presence of demyelinated plaques in spinal cords of EAE rats, (Luxol fast Blue staining and anti-MBP immunohystochemistry). On the contrary the therapeutic schedule with MSCs significantly reduces the number and the extension of demyelinated areas in the spinal cords, confirming clinical score evaluations. These results demonstrated that MSCs ameliorate the clinical course of EAE and hamper the disease relapsing by reducing the areas of demyelinated lesions. Granted by MIUR – FIRB Futuro in Ricerca 2008 Prot. N° RBFR08VSVI_001.