Long-lasting anxiolytic effect of neural precursor cells freshly prepared but not neurosphere-derived cell transplantation in newborn rats

GABAergic interneurons in epilepsy: More than a simple change in inhibition

The pathophysiology of epilepsy has been historically grounded on hyperexcitability attributed to the oversimplified imbalance between excitation (E) and inhibition (I) in the brain. The decreased inhibition is mostly attributed to deficits in gamma-aminobutyric acid-containing (GABAergic) interneurons, the main source of inhibition in the central nervous system. However, the cell diversity, the wide range of spatiotemporal connectivity, and the distinct effects of the neurotransmitter GABA especially during development, must be considered to critically revisit the concept of hyperexcitability caused by decreased inhibition as a key characteristic in the development of epilepsy. Here, we will discuss that behind this known mechanism, there is a heterogeneity of GABAergic interneurons with distinct functions and sources, which have specific roles in controlling the neural network activity within the recruited microcircuit and altered network during the epileptogenic process. This article is part of the Special Issue "NEWroscience 2018.

Transplantation of inhibitory precursor cells from medial ganglionic eminence produces distinct responses in two different models of acute seizure induction

Medial ganglionic eminence (MGE) is one of the sources of inhibitory interneurons during development. Following transplantation in postnatal developing brain, MGE cells can increase local inhibition suggesting a possible protection to GABAergic dysfunction in brain disorders, such as epilepsy. Since it has been shown that MGE-derived cells harvested as neurospheres are able to suppress seizures, it might be important to investigate whether these protective effects would change in different seizure models. Here, we used pentylenetetrazole-(PTZ) and maximal electroshock (MES)-induced seizure models to test whether the transplantation of MGE cells would increase the threshold to trigger acute seizures. When transplanted into the neocortex (layers 3-4) of neonatal mice (postnatal days 3-4), MGE cells were able to survive and were mainly found in piriform cortex, fimbria, and ventricular wall regions. Additionally, the number of GFP+ cells found in the brains of mice induced with PTZ and MES differed significantly and suggests proliferation and larger survival rate of MGE-transplanted cells after PTZ, but not MES-induced seizures. Following transplantation, there was a reduction in the number of animals presenting mild and severe seizures induced by PTZ. Furthermore, MGE-cell transplantation was able to increase threshold to seizures induced by PTZ, but was not able to prevent seizure spread induced by MES.

Xiao Yao San Improves the Anxiety-Like Behaviors of Rats Induced by Chronic Immobilization Stress: The Involvement of the JNK Signaling Pathway in the Hippocampus

The current study evaluated the effects of Xiao Yao San (XYS) on anxiety-like behaviors and sought to determine whether the c-Jun N-terminal kinase (JNK) signaling pathway is involved. A total of 40 rats were divided into 5 groups (n=8): the control group (deionized water, per os (p.o.)), the model group (deionized water, p.o.), the SP600125 group (surgery), the per se group (surgery), and the XYS group (3.9 g/kg/d, p.o.). A 1% dimethyl sulfoxide (DMSO) citrate buffer solution (2 µL/ventricle/d) and SP600125 (10 µg/ventricle, 2 µL/ventricle/d) were separately and bilaterally injected into the rats of the two surgery groups via the ventricular system of the brain. All but the control group underwent 14 d of chronic immobilization stress (CIS; 3 h/d). On day 15, the body weights of all of the rats were measured; additionally, the rats were subjected to the elevated plus maze (EPM) and novelty suppressed feeding (NSF) tests. Finally, JNK signaling pathway indices, including phosphorylated JNK (P-JNK), JNK, phosphorylated c-Jun (P-c-Jun) and cytochrome C (Cyt-C), were examined. After modeling, the body weight and behavioral analyses of the model rats indicated that this modeling method induced anxiety-like behaviors. P-JNK, JNK, and P-c-Jun were altered in the hippocampus of the model rats. After 14 d of treatment with XYS and SP600125, rat body weight and behaviors as well as P-JNK, JNK, and P-c-Jun had changed. However, no significant difference in Cyt-C was found. XYS improves the anxiety-like behaviors induced by CIS, which might be related to the JNK signaling pathway in the hippocampus.

Medial Ganglionic Eminence Cells Freshly Obtained or Expanded as Neurospheres Show Distinct Cellular and Molecular Properties in Reducing Epileptic Seizures

AIMS

Medial ganglionic eminence (MGE) progenitors give rise to inhibitory interneurons and may serve as an alternative cell source for large-scale cell transplantation for epilepsy after in vitro expansion. We investigated whether modifications in the culture medium of MGE neurospheres affect neuronal differentiation and expression of MGE-specific genes. In vivo, we compared anticonvulsant effects and cell differentiation pattern among neurospheres grown in different culture media and compared them with freshly harvested MGE cells.

METHODS

We used four variations of cell culture: standard, containing growth factors (EGF/FGF-2) (GF); addition of retinoic acid (GF-RA); withdrawal of EGF/FGF-2 (WD); and addition of retinoic acid and withdrawal of EGF/FGF-2 (WD-RA). Based on in vitro results neurosphere-grown (WD-RA or GF conditions) or fresh MGE cells were transplanted into the hippocampus.

RESULTS

In vitro WD-RA showed increased neuronal population and higher expression of Dlx1, Nkx2.1, and Lhx6 genes in comparison with GF culture condition. After transplantation, fresh MGE cells and neurospheres (GF) showed anticonvulsant effects. However, fresh MGE cells differentiated preferentially into inhibitory neurons, while GF gave rise to glial cells.

CONCLUSION

We conclude that freshly isolated and neurosphere-grown MGE cells reduced seizures by different mechanisms (inhibitory interneurons vs. astrocytes). Fresh MGE cells appear more appropriate for cell therapies targeting inhibitory interneurons for conferring anticonvulsant outcomes.