<p>Many studies on neurogenesis in adult dentate gyrus (DG) have been performed on rodents and other mammalian species, but only a few on adult human DG.  This study is focusing on neurogenesis in adult human DG. To characterize the birth of cells in DG, the expression of the cell proliferation marker Ki67 was examined using immunohistochemistry. Ki67-positive labelling was indeed observed in the granular cell layer and the molecular layer of dentate gyrus and in the hilus of hippocampus, as well as in the subgranular zone (SGZ). The Ki67 positive nuclei could be divided into three groups, based on their morphology and position, suggesting that one of the groups represents neuronal precursors. Fewer Ki67 positive cells were seen in aged subjects and in subjects with an alcohol abuse. When comparing the Ki67 positive cells and the amount of blood vessels as determined by anti factor VIII, no systematic pattern could be discerned. To identify possible stem/progenitor cells in DG a co-labelling with nestin and glial fibrillary acid protein was carried out. Co-labelling was found in the SGZ, but most of the filaments were positive for just one of the two antibodies. Antibodies to detect immature/mature neurons were also used to investigate adult human neurogenesis in DG. The immature marker βIII-tubulin showed a weak expression. The other two immature markers (PSA-NCAM and DCX) used did not work, probably since they were not cross-reacting against human tissue. In summary, this study shows that new cells are continuously formed in the adult human hippocampus, but at a slower pace compared to the rat, and that some of these new cells may represent neuronal precursors.</p>

Many studies on neurogenesis in adult dentate gyrus (DG) have been performed on rodents and other mammalian species, but only a few on adult human DG.  This study is focusing on neurogenesis in adult human DG. To characterize the birth of cells in DG, the expression of the cell proliferation marker Ki67 was examined using immunohistochemistry. Ki67-positive labelling was indeed observed in the granular cell layer and the molecular layer of dentate gyrus and in the hilus of hippocampus, as well as in the subgranular zone (SGZ). The Ki67 positive nuclei could be divided into three groups, based on their morphology and position, suggesting that one of the groups represents neuronal precursors. Fewer Ki67 positive cells were seen in aged subjects and in subjects with an alcohol abuse. When comparing the Ki67 positive cells and the amount of blood vessels as determined by anti factor VIII, no systematic pattern could be discerned. To identify possible stem/progenitor cells in DG a co-labelling with nestin and glial fibrillary acid protein was carried out. Co-labelling was found in the SGZ, but most of the filaments were positive for just one of the two antibodies. Antibodies to detect immature/mature neurons were also used to investigate adult human neurogenesis in DG. The immature marker βIII-tubulin showed a weak expression. The other two immature markers (PSA-NCAM and DCX) used did not work, probably since they were not cross-reacting against human tissue. In summary, this study shows that new cells are continuously formed in the adult human hippocampus, but at a slower pace compared to the rat, and that some of these new cells may represent neuronal precursors.

Dissertation (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2008. / Vita. Bibliography: p.149-164

Parkinson’s disease (PD) has been reported to negatively affect adult neurogenesis. Mitochondrial dysfunction associated with PD may be involved, given that recent studies have identified mitochondria to be central regulators of neural stem cell (NSC) fate decisions. For this thesis, we sought to characterize adult neurogenesis in PINK1 and parkin knockout (KO) mouse models of PD. Immunohistochemical staining of subventricular zone (SVZ) and subgranular zone (SGZ) tissue sections from 6 month old mice was performed in order to identify and quantify changes in specific cell populations involved with adult neurogenesis. The loss of PINK1 or parkin was found to cause aberrant changes in adult neurogenesis, particularly in the SGZ. Going forward, it would be interesting to determine if the observed changes in adult neurogenesis were the result of mitochondrial dysfunction.

Following traumatic brain injury (TBI), the hippocampus is particularly vulnerable to damage, and BDNF, an endogenous neurotrophin that activates the TrkB receptor, has been shown to play a key role in the brain’s neuroprotective response. Activation of the TrkB signaling pathway by BDNF in the CNS promotes cell survival and aids in cell growth. However, due to its inability to cross the blood brain barrier (BBB), the therapeutic advantages of BDNF treatment following TBI are limited. 7,8-Dihydroxyflavone (7,8-DHF) is a flavonoid that mimics the effects of BDNF, is a potent TrkB receptor agonist, and can successfully cross the BBB. Our lab has previously demonstrated that administration of 7,8-DHF post-TBI results in improved cognitive functional recovery, increased neuronal survival, and reduced lesion volume. The current study examined the effects of 7,8-DHF on neurogenesis and neuronal migration in the dentate gyrus following TBI. In this study, adult male Sprague-Dawley rats were subjected to moderate controlled cortical impact injury (CCI) or sham surgery. Injured animals received 5 daily single doses of 7,8-DHF treatment (i.p) or vehicle starting either 60 mins after injury or 2 days after injury. BrdU was administered in 3 doses at 2 days post-injury for animals sacrificed at day 15, and single daily doses at days 1-7 post-injury for animals sacrificed at day 28 to label cell proliferation. Animals were sacrificed at 15 days or 28 days post-injury to examine cell proliferation, generation of new neurons, and differentiation of newly generated cells using proliferation marker Ki67, immature neuronal marker DCX, and BrdU double-labeling with markers for mature neurons (NeuN), astrocytes (GFAP) and microglia (Iba1). We found that administration of 5 doses (5mg/kg) of 7,8-DHF beginning two days post-injury had the strongest effect on neurogenesis and migration, but did not have a significant prolonged effect on cell proliferation at 15 days post-injury. We also found that 7,8-DHF treatment given early or 2 days post-TBI did not affect the neuronal differentiation in the granule cell layer. However, a higher percentage of BrdU/GFAP+ and BrdU/IBa1+ cells were found in the hilus regions in 7,8-DHF treated animals, suggesting newly generated cells in this region are mostly glial cell types. Our results suggest that 7,8-DHF has neurotrophic-like therapeutic effects following injury, and due to increased neurogenesis (compared to injured animals treated with vehicle), may effectively contribute to greater cell survival long-term. Additionally, potential long-term survival coupled with increased outward migration from the subgranular zone may result in increased integration of newly formed neurons into existing hippocampal circuitry, further contributing to cognitive recovery.

<p> G93A SODI mice (G93A mice) are a transgenic model over-expressing a mutant human Cu/Zn-SOD gene, and are a model for amyotrophic lateral sclerosis (ALS), a predominantly motor neurodegenerative disease. Hippocampal neurogenesis in the subgranular zone (SGZ) of dentate gyms (DG) occurs throughout the life. It is regulated by many pathological and physiological processes. There is controversy with respect to the basal level of hippocampal neurogenesis and its response to exercise in neurodegenerative diseases and their mouse models. Little information regarding hippocampal neurogenesis is available in G93A mice. The present study was designed to study the impact of treadmill exercise and sex differences on hippocampal neurogenesis in this model. In addition, potential molecular mechanisms regulating hippocampal neurogenesis including growth factors (BDNF and IGFl) and oxidative stress (SOD2, catalase, 8-0Hdg, and 3-NT) were also addressed in the study. Bromodeoxyuridine (BrdU) was used to label newly generated cells. G93A and wild type (WT) mice were subjected to treadmill exercise (EX) or a sedentary (SEO) lifestyle. Immunohistochemistry was used to detect BrdU labeled newly proliferating cells, surviving cells, and their phenotype, as well as for determination of oxidative stress. BDNF and IGFl mRNA expression was assessed by in situ hybridization. Results showed that (1) G93A mice had an elevated basal level of hippocampal neurogenesis for both cell survival and neuronal differentiation, a growth factor (BDNF mRNA), and an oxidative stress marker (NT), as compared to wild type sedentary mice. (2) Treadmill running did not show any further effect on hippocampal neurogenesis, growth factors, oxidative stress, and antioxidant enzymes in G93A mice, while treadmill running promoted hippocampal neurogenes1s and expression of the growth factor (BDNF mRNA), and lowered oxidative stress (8-0Hdg) in WT mice. (3) There also were sex differences in hippocampal neurogenesis in G93A mice, whereby male G93A mice had a significant higher level of cell proliferation but a lower level of survival than female G93A mice. (4) The DG BDNF mRNA was associated with cell survival and neuronal differentiation in sedentary G93A mice, suggesting that BDNF is associated with a higher basal level of hippocampal neurogenesis in G93A mice. We conclude that G93A mice are more permissive in the context of hippocampal neurogenesis, which is associated with elevated DG BDNF mRNA expression. Running did not have impact on hippocampal neurogenesis and BDNF mRNA expression in G93A mice, probably due to a 'ceiling effect' of the already heightened basal levels of hippocampal neurogenesis and BDNF mRNA in this model. In addition, sex differences also affect hippocampal neurogenes1s, but the further study is needed to clarify the underlying molecular mechanisms. </p> / Thesis / Doctor of Philosophy (PhD)