In the adult hippocampus, neurogenesis proceeds in the subgranular zone (SGZ) of the dentate gyrus (DG), but not in the cornu Ammonis (CA). Recently, we demonstrated in monkeys that transient brain ischemia induces an increase of the neuronal progenitor cells in the SGZ, but not in CA1, in the second week after the insult. To identify the origin of primary neuronal progenitors in vivo, we compared the postischemic monkey DG and CA1, using light and electron microscopy, focusing on specific phenotype markers, as well as the expression of neurotrophic factors. Laser confocal microscopy showed that 1-3% of 5-bromo-2'-deoxyuridine (BrdU)-positive cells in the SGZ after 2-96 h labeling were also positive for neuronal markers such as TUC4, betaIII tubulin, and NeuN on days 9 and 15. In contrast, despite the presence of numerous BrdU-positive cells, CA1 showed no neurogenesis at any time points, and all the progenitors were positive for glial markers: Iba1 or S-100beta on days 4, 9, and 15. Highly polysialylated neural cell adhesion molecule (PSA-NCAM)-positive cells were abundant in the SGZ, but were absent in CA1. On day 9, most of the immature neurons positive for betaIII-tubulin in SGZ showed an increase in PSA-NCAM immunoreactivity. The immunoreactivity of brain-derived neurotrophic factor (BDNF) was abundant at the vascular adventitia of the SGZ, but was absent at the adventitia of CA1. BrdU-positive progenitor cells were frequently seen in the vicinity of proliferating blood vessels. Ultrastructural analysis indicated that most of the neuronal progenitor cells and microglia originated from the pericytes of capillaries and/or adventitial cells of arterioles (called vascular adventitia). The detaching adventitial cells showed mitotic figures in the perivascular space, and the resultant neuronal progenitor cells made contact with dendritic spines associated with synaptic vesicles or boutons. These data implicate the vascular adventitia as a novel potential source of neuronal progenitor cells in the postischemic primate SGZ.

No abstract

No abstract

The main stem cell niche for neurogenesis in the adult mammalian brain is the subventricular zone (SVZ) that extends along the cerebral lateral ventricles. We aimed at characterizing the initial molecular responses of the macaque monkey SVZ to transient, global cerebral ischemia. We microdissected tissue lining the anterior horn of the lateral ventricle (SVZa) from 7 day post-ischemic and sham-operated monkeys. Transcriptomics shows that in ischemic SVZa, 541 genes were upregulated and 488 genes were down-regulated. The transcription data encompassing the upregulated genes revealed a profile typical for quiescent stem cells and astrocytes. In the primate brain the SVZ is morphologically subdivided in distinct and separate ependymal and subependymal regions. The subependymal contains predominantly neural stem cells (NSC) and differentiated progenitors. To determine in which SVZa region ischemia had evoked transcriptional upregulation, sections through control and ischemic SVZa were analyzed by high-throughput in situ hybridization for a total of 150 upregulated genes shown in the www.monkey-niche.org image database. The majority of the differentially expressed genes mapped to the subependymal layers on the striatal or callosal aspect of the SVZa. Moreover, a substantial number of upregulated genes was expressed in the ependymal layer, implicating a contribution of the ependyma to stem cell biology. The transcriptome analysis yielded several novel gene markers for primate SVZa including the apelin receptor that is strongly expressed in the primate SVZa niche upon ischemic insult.

That tumors lack innervation is dogma in the field of pathology, but the molecular determinants of this phenomenon remain elusive. We studied the effects of conditioned media from Colon 26 and B16 mouse tumor cell lines on the axonal outgrowth and cellular differentiation of embryonic Institute of Cancer Research (ICR) mouse dorsal root ganglion cells. Tumor-conditioned media suppressed dorsal root ganglion axonal extension but had no effect on neuronal or glial differentiation. We found that the tumor cells expressed most of the class 3 semaphorins -axon guidance molecules. T he lack of innervation in tumors is a generally accepted fact,(1) but the molecular determinants of this phenomenon are poorly understood. Furthermore, certain tumors such as esophageal cancer were shown to be innervated by peptidergic nerve fibers and to promote process extension in DRG neurons. (2) Notably, sarcomas can secrete NGF, which promotes proliferation and axonal outgrowth of DRG neurons, the observation of which led to the initial discovery of NGF.(3) Thus, the effects of tumors on axonal growth are unclear and need further analysis.Peripheral nerves are known to associate with blood vessels,reflecting their need for oxygen and nutrients and their control of vasoconstriction and vasodilation. (5) In mutant embryos containing disorganized nerves, blood vessel branching is altered to follow the nerve, (6) suggesting that local signals supplied by nerve fibers may provide a template that determines blood vessel patterning. These data indicate a functional relationship between axonal outgrowth and angiogenesis under physiological conditions, and make the question of tumor innervation even more intriguing.DRG neurons innervate most of the internal organs, thus their processes have the highest potential for interacting with the cells of a tumor growing in the body. We therefore investigated whether molecular cues secreted from tumor cells affect axonal outgrowth and additionally alter the differentiation capacity of immature neural cells in the DRG. Here, we report that supernatant isolated from two tumor cell line cultures inhibited process extension of DRG neurons, and present evidence implicating secreted class 3 semaphorins as mediators of this tumor-induced axonal inhibition. Materials and MethodsDRG culture. Embryos at embryonic day 12.5 were dissected from pregnant Institute of Cancer Research (ICR) mice (SCL, Shizuoka, Japan). DRG were extracted free of surrounding tissues and placed one per well in 24-well, poly-l-lysine-coated culture plates (Iwaki, Tokyo, Japan). Colon 26 (C26; mouse colon cancer) and B16 (mouse melanoma) tumor cell lines were cultured in DMEM (Sigma-Aldrich, St Louis, MO, USA) supplemented with 10% FBS (Sigma-Aldrich). Culture supernatants were collected when cells reached approximately 80% confluence. Four culture media were prepared: (i) control medium, DMEM + 10% FBS + 50 ng/mL human recombinant NGF (PeproTech, Rocky Hill, NJ, USA); (ii) tumor-conditioned medium, equal amounts of control medium with 10...