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1.  GDF-15 Secreted from Human Umbilical Cord Blood Mesenchymal Stem Cells Delivered Through the Cerebrospinal Fluid Promotes Hippocampal Neurogenesis and Synaptic Activity in an Alzheimer's Disease Model 
Stem Cells and Development  2015;24(20):2378-2390.
Our previous studies demonstrated that transplantation of human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) into the hippocampus of a transgenic mouse model of Alzheimer's disease (AD) reduced amyloid-β (Aβ) plaques and enhanced cognitive function through paracrine action. Due to the limited life span of hUCB-MSCs after their transplantation, the extension of hUCB-MSC efficacy was essential for AD treatment. In this study, we show that repeated cisterna magna injections of hUCB-MSCs activated endogenous hippocampal neurogenesis and significantly reduced Aβ42 levels. To identify the paracrine factors released from the hUCB-MSCs that stimulated endogenous hippocampal neurogenesis in the dentate gyrus, we cocultured adult mouse neural stem cells (NSCs) with hUCB-MSCs and analyzed the cocultured media with cytokine arrays. Growth differentiation factor-15 (GDF-15) levels were significantly increased in the media. GDF-15 suppression in hUCB-MSCs with GDF-15 small interfering RNA reduced the proliferation of NSCs in cocultures. Conversely, recombinant GDF-15 treatment in both in vitro and in vivo enhanced hippocampal NSC proliferation and neuronal differentiation. Repeated administration of hUBC-MSCs markedly promoted the expression of synaptic vesicle markers, including synaptophysin, which are downregulated in patients with AD. In addition, in vitro synaptic activity through GDF-15 was promoted. Taken together, these results indicated that repeated cisterna magna administration of hUCB-MSCs enhanced endogenous adult hippocampal neurogenesis and synaptic activity through a paracrine factor of GDF-15, suggesting a possible role of hUCB-MSCs in future treatment strategies for AD.
PMCID: PMC4598918  PMID: 26154268
2.  Intra-Arterially Delivered Mesenchymal Stem Cells Are Not Detected in the Brain Parenchyma in an Alzheimer’s Disease Mouse Model 
PLoS ONE  2016;11(5):e0155912.
Mesenchymal stem cells (MSCs) have a promising role as a therapeutic agent for neurodegenerative diseases such as Alzheimer’s disease (AD). Prior studies suggested that intra-arterially administered MSCs are engrafted into the brain in stroke or traumatic brain injury (TBI) animal models. However, a controversial standpoint exists in terms of the integrity of the blood brain barrier (BBB) in transgenic AD mice. The primary goal of this study was to explore the feasibility of delivering human umbilical cord-blood derived mesenchymal stem cells (hUCB-MSCs) into the brains of non-transgenic WT (C3H/C57) and transgenic AD (APP/PS1) mice through the intra-arterial (IA) route. Through two experiments, mice were infused with hUCB-MSCs via the right internal carotid artery and were sacrificed at two different time points: 6 hours (experiment 1) or 5 minutes (experiment 2) after infusion. In both experiments, no cells were detected in the brain parenchyma while MSCs were detected in the cerebrovasculature in experiment 2. The results from this study highlight that intra-arterial delivery of MSCs is not the most favorable route to be implemented as a potential therapeutic approach for AD.
PMCID: PMC4874686  PMID: 27203695
3.  Traumatic Brain Injury Activation of the Adult Subventricular Zone Neurogenic Niche 
Traumatic brain injury (TBI) is common in both civilian and military life, placing a large burden on survivors and society. However, with the recognition of neural stem cells in adult mammals, including humans, came the possibility to harness these cells for repair of damaged brain, whereas previously this was thought to be impossible. In this review, we focus on the rodent adult subventricular zone (SVZ), an important neurogenic niche within the mature brain in which neural stem cells continue to reside. We review how the SVZ is perturbed following various animal TBI models with regards to cell proliferation, emigration, survival, and differentiation, and we review specific molecules involved in these processes. Together, this information suggests next steps in attempting to translate knowledge from TBI animal models into human therapies for TBI.
PMCID: PMC4969304  PMID: 27531972
adult neurogenesis; stem cells; traumatic brain injury (TBI); regeneration; proliferation
4.  A combined post-mortem magnetic resonance imaging and quantitative histological study of multiple sclerosis pathology 
Brain  2012;135(10):2938-2951.
Multiple sclerosis is a chronic inflammatory neurological condition characterized by focal and diffuse neurodegeneration and demyelination throughout the central nervous system. Factors influencing the progression of pathology are poorly understood. One hypothesis is that anatomical connectivity influences the spread of neurodegeneration. This predicts that measures of neurodegeneration will correlate most strongly between interconnected structures. However, such patterns have been difficult to quantify through post-mortem neuropathology or in vivo scanning alone. In this study, we used the complementary approaches of whole brain post-mortem magnetic resonance imaging and quantitative histology to assess patterns of multiple sclerosis pathology. Two thalamo-cortical projection systems were considered based on their distinct neuroanatomy and their documented involvement in multiple sclerosis: lateral geniculate nucleus to primary visual cortex and mediodorsal nucleus of the thalamus to prefrontal cortex. Within the anatomically distinct thalamo-cortical projection systems, magnetic resonance imaging derived cortical thickness was correlated significantly with both a measure of myelination in the connected tract and a measure of connected thalamic nucleus cell density. Such correlations did not exist between these markers of neurodegeneration across different thalamo-cortical systems. Magnetic resonance imaging lesion analysis depicted clearly demarcated subcortical lesions impinging on the white matter tracts of interest; however, quantitation of the extent of lesion-tract overlap failed to demonstrate any appreciable association with the severity of markers of diffuse pathology within each thalamo-cortical projection system. Diffusion-weighted magnetic resonance imaging metrics in both white matter tracts were correlated significantly with a histologically derived measure of tract myelination. These data demonstrate for the first time the relevance of functional anatomical connectivity to the spread of multiple sclerosis pathology in a ‘tract-specific’ pattern. Furthermore, the persisting relationship between metrics from post-mortem diffusion-weighted magnetic resonance imaging and histological measures from fixed tissue further validates the potential of imaging for future neuropathological studies.
PMCID: PMC3470716  PMID: 23065787
multiple sclerosis; post-mortem imaging; diffusion imaging; white matter tracts; neurodegeneration
5.  Numb links extracellular cues to intracellular polarity machinery to promote chemotaxis 
Developmental cell  2011;20(5):610-622.
Cell polarization is essential throughout development for proliferation, migration and differentiation. However, it is not known how extracellular cues correctly orient cell polarity at distinct stages of development. Here we show that the endocytic adapter protein, Numb, previously characterized for its role in cell proliferation, subsequently plays an important role in cell migration. In neural precursors stimulated with the chemotactic factor BDNF, Numb binds to activated TrkB, the BDNF receptor, and functions both as an endocytic regulator for TrkB and as a scaffold for atypical PKC (aPKC). Thus Numb promotes BDNF-dependent aPKC activation. Interestingly, Numb is also a substrate of aPKC. When phosphorylated, Numb exhibits increased efficacy in binding TrkB and in promoting a chemotactic response to BDNF. Therefore, Numb functions in a feed-forward loop to promote chemotaxis of neural precursors, linking BDNF, an extracellular cue, to aPKC, a critical component of the intrinsic polarity machinery.
PMCID: PMC3103748  PMID: 21571219
6.  Potent Antibody-Mediated Neutralization and Evolution of Antigenic Escape Variants of Simian Immunodeficiency Virus Strain SIVmac239 In Vivo▿  
Journal of Virology  2008;82(19):9739-9752.
Here, we describe the evolution of antigenic escape variants in a rhesus macaque that developed unusually high neutralizing antibody titers to SIVmac239. By 42 weeks postinfection, 50% neutralization of SIVmac239 was achieved with plasma dilutions of 1:1,000. Testing of purified immunoglobulin confirmed that the neutralizing activity was antibody mediated. Despite the potency of the neutralizing antibody response, the animal displayed a typical viral load profile and progressed to terminal AIDS with a normal time course. Viral envelope sequences from week 16 and week 42 plasma contained an excess of nonsynonymous substitutions, predominantly in V1 and V4, including individual sites with ratios of nonsynonymous to synonymous substitution rates (dN/dS) highly suggestive of strong positive selection. Recombinant viruses encoding envelope sequences isolated from these time points remained resistant to neutralization by all longitudinal plasma samples, revealing the failure of the animal to mount secondary responses to the escaped variants. Substitutions at two sites with significant dN/dS values, one in V1 and one in V4, were independently sufficient to confer nearly complete resistance to neutralization. Substitutions at three additional sites, one in V4 and two in gp41, conferred moderate to high levels of resistance when tested individually. All the amino acid changes leading to escape resulted from single nucleotide substitutions. The observation that antigenic escape resulted from individual, single amino acid replacements at sites well separated in current structural models of Env indicates that the virus can utilize multiple independent pathways to rapidly achieve similar levels of resistance.
PMCID: PMC2546989  PMID: 18667507

Results 1-6 (6)