Vivian Capilla-Gonzalez

Age-Related Changes in Astrocytic and Ependymal Cells of the Subventricular Zone

Neurogenesis persists in the adult subventricular zone (SVZ) of the mammalian brain. During aging, the SVZ neurogenic capacity undergoes a progressive decline, which is attributed to a decrease in the population of neural stem cells (NSCs). However, the behavior of the NSCs that remain in the aged brain is not fully understood. Here we performed a comparative ultrastructural study of the SVZ niche of 2‐month‐old and 24‐month‐old male C57BL/6 mice, focusing on the NSC population. Using thymidine‐labeling, we showed that residual NSCs in the aged SVZ divide less frequently than those in young mice. We also provided evidence that ependymal cells are not newly generated during senescence, as others studies suggest. Remarkably, both astrocytes and ependymal cells accumulated a high number of intermediate filaments and dense bodies during aging, resembling reactive cells. A better understanding of the changes occurring in the neurogenic niche during aging will allow us to develop new strategies for fighting neurological disorders linked to senescence. GLIA 2014;62:790–803

A leak pathway for luminal protons in endosomes drives oncogenic signalling in glioblastoma

Epidermal growth factor receptor (EGFR) signaling is a potent driver of glioblastoma, a malignant and lethal form of brain cancer. Disappointingly, inhibitors targeting receptor tyrosine kinase activity are not clinically effective, and EGFR persists on the plasma membrane to maintain tumor growth and invasiveness. Here we show that endolysosomal pH is critical for receptor sorting and turnover. By functioning as a leak pathway for protons, the Na+/H+ exchanger NHE9 limits luminal acidification to circumvent EGFR turnover and prolong downstream signaling pathways that drive tumor growth and migration. In glioblastoma, NHE9 expression is associated with stem/progenitor characteristics, radiochemoresistance, poor prognosis and invasive growth in vitro and in vivo. Silencing or inhibition of NHE9 in brain tumor initiating cells attenuates tumorsphere formation and improves efficacy of EGFR inhibitor. Thus, NHE9 mediates inside-out control of oncogenic signaling and is a highly druggable target for pan-specific receptor clearance in cancer therapy.

The generation of oligodendroglial cells is preserved in the rostral migratory stream during aging

The subventricular zone (SVZ) is the largest source of newly generated cells in the adult mammalian brain. SVZ-derived neuroblasts migrate via the rostral migratory stream (RMS) to the olfactory bulb (OB), where they differentiate into mature neurons. Additionally, a small proportion of SVZ-derived cells contribute to the generation of myelinating oligodendrocytes. The production of new cells in the SVZ decreases during aging, affecting the incorporation of new neurons into the OB. However, the age-related changes that occur across the RMS are not fully understood. In this study we evaluate how aging affects the cellular organization of migrating neuroblast chains, the proliferation, and the fate of the newly generated cells in the SVZ-OB system. By using electron microscopy and immunostaining, we found that the RMS path becomes discontinuous and its cytoarchitecture is disorganized in aged mice (24-month-old mice). Subsequently, OB neurogenesis was impaired in the aged brain while the production of oligodendrocytes was not compromised. These findings provide new insight into oligodendrocyte preservation throughout life. Further exploration of this matter could help the development of new strategies to prevent neurological disorders associated with senescence.

Subventricular Zone Localized Irradiation Affects the Generation of Proliferating Neural Precursor Cells and the Migration of Neuroblasts

Radiation therapy is a part of the standard treatment for brain tumor patients, often resulting in irreversible neuropsychological deficits. These deficits may be due to permanent damage to the neural stem cell (NSC) niche, damage to local neural progenitors, or neurotoxicity. Using a computed tomography‐guided localized radiation technique, we studied the effects of radiation on NSC proliferation and neuroblast migration in the mouse brain. Localized irradiation of the subventricular zone (SVZ) eliminated the proliferating neural precursor cells and migrating neuroblasts. After irradiation, type B cells in the SVZ lacked the ability to generate migrating neuroblasts. Neuroblasts from the unirradiated posterior SVZ did not follow their normal migratory path through the irradiated anterior SVZ. Our results indicate that the migrating neuroblasts were not replenished, despite the presence of type B cells in the SVZ post‐irradiation. This study provides novel insights into the effects of localized SVZ radiation on neurogenesis and cell migration that may potentially lead to the development of new radiotherapy strategies to minimize damage to NSCs and neuroblast migration. STEM CELLS2012;30:2548–2560

Bottlenecks in the Efficient Use of Advanced Therapy Medicinal Products Based on Mesenchymal Stromal Cells.

Mesenchymal stromal cells (MSCs) have been established as promising candidate sources of universal donor cells for cell therapy due to their contributions to tissue and organ homeostasis, repair, and support by self-renewal and multidifferentiation, as well as by their anti-inflammatory, antiproliferative, immunomodulatory, trophic, and proangiogenic properties. Various diseases have been treated by MSCs in animal models. Additionally, hundreds of clinical trials related to the potential benefits of MSCs are in progress. However, although all MSCs are considered suitable to exert these functions, dissimilarities have been found among MSCs derived from different tissues. The same levels of efficacy and desired outcomes have not always been achieved in the diverse studies that have been performed thus far. Moreover, autologous MSCs can be affected by the disease status of patients, compromising their use. Therefore, collecting information regarding the characteristics of MSCs obtained from different sources and the influence of the host (patient) medical conditions on MSCs is important for assuring the safety and efficacy of cell-based therapies. This review provides relevant information regarding factors to consider for the clinical application of MSCs.

Ethical Implications in the Use of Embryonic and Adult Neural Stem Cells

The advent and growth of technological advances have led to new routes of knowledge. Thereby, we currently face new challenges. We have just started to get a glimpse of the structural and functional role of neural stem cells in differentiation and migration processes, the origin of synaptic networks, and subsequent readjustments in specific circuits. A whole range of treatment possibilities originates from this knowledge that potentially can be used for different neurological diseases in humans. Although this is an encouraging scenario, it implies that the human brain is the object of such study, as well as its potential manipulation and transplantation. It is, therefore, pertinent that ethical principles should be followed in such research to have proper balance between what can be done and what should be done, according to every specific context. Hence, it is wise to consider ethical implications in every research project, along with potential clinical applications, under the principle of causing no harm, following risk and benefit rules in decision making and with respect of the human condition as a priority.

Implications of irradiating the subventricular zone stem cell niche.

Radiation therapy is a standard treatment for brain tumor patients. However, it comes with side effects, such as neurological deficits. While likely multi-factorial, the effect may in part be associated with the impact of radiation on the neurogenic niches. In the adult mammalian brain, the neurogenic niches are localized in the subventricular zone (SVZ) of the lateral ventricles and the dentate gyrus of the hippocampus, where the neural stem cells (NSCs) reside. Several reports showed that radiation produces a drastic decrease in the proliferative capacity of these regions, which is related to functional decline. In particular, radiation to the SVZ led to a reduced long-term olfactory memory and a reduced capacity to respond to brain damage in animal models, as well as compromised tumor outcomes in patients. By contrast, other studies in humans suggested that increased radiation dose to the SVZ may be associated with longer progression-free survival in patients with high-grade glioma. In this review, we summarize the cellular and functional effects of irradiating the SVZ niche. In particular, we review the pros and cons of using radiation during brain tumor treatment, discussing the complex relationship between radiation dose to the SVZ and both tumor control and toxicity.

Abstract 444: Slit2 stimulation induces a chemorepellent effect on the migration of human GBM brain tumor initiating cells

Gioblastoma (GBM) is the most common and aggressive form of primary brain tumor in adults. Despite the use of radiotherapy, chemotherapy, and surgery, survival still averages 14 months. GBM has a recurrence of almost 100% due to highly invasive brain tumor initiating cells (BTICs) left behind after surgery. As reported by our group and others, survival expectancy of GBM patients is greatly affected by tumor location. Specifically, tumors in close proximity to the lateral ventricles (LV) show a higher incidence of distant recurrence, as well as worse survival expectancy. This location is the site of the subventricular zone (SVZ), the largest neurogenic niche in the adult brain of mammals, which maintains continuous production of neural stem cells (NSCs) throughout adult life. The cause for worse prognosis in patients whose tumors are in close proximity to the SVZ is not known, but one hypothesis is that regulators of the neurogenic niche might be influencing tumor cells to become more invasive and migratory. In rodents, Slit-Robo is one of these signals which functions as a chemorepulsive ligand-receptor system involved in guiding the migration of newly generated NSCs from the SVZ to other regions of the central nervous system. Further, it has been found that Slit2 affects the migration of glioma and medulloblastoma commercial cell lines. We have previously demonstrated that primary cultured human GBM BTICs respond to slit stimulation in a chemorepellant manner. However, the robo receptor implicated in this response as well as the intracellular mechanisms affected by Slit stimulation in BTICs have not been described. Here we propose to study the effects of Slit-2 stimulation on the migration of human GBM BTICs obtained from intraoperative samples. Furthermore we evaluated the activity of Rac1 and CDC42 in GBM BTICs upon slit stimulation. We determined that Robo1 is expressed by multiple primary human GBM samples. BTICs obtained from these samples present a migratory behavior in vitro that presents a chemorepellent response upon slit2 stimulation. This chemorepellant response is not due to a decrease of cell migration as Slit2 stimulation also induced an increase in BTIC migration speed. This migratory response of BTICs to Slit2 is decreased when the Robo1 receptor is knocked down using shRNA transduction. Intracellularly, we observed that Slit2 stimulation induces a decrease in the active (GTP-bound forms) of Rac1 and CDC42. Our findings demonstrate that Slit2 can induce a chemorepellent effect on the migration of human GBM BTICs through the activation of Robo1 receptor and the subsequent modulation of the Small GTPases Rac1 and CDC42. Our results indicate that regulators of SVZ cells migration can also affect GBM cells behavior and could potentially contribute to the more aggressive behavior of SVZ-contacting GBMs. Citation Format: Hugo Guerrero-Cazares, Emily Lavell, Gabrielle Drummond, Sural Ranamukhaarachchi, Vivian Capilla-Gonzalez, Paula Schiapparelli, Alfredo Quinones-Hinojosa. Slit2 stimulation induces a chemorepellent effect on the migration of human GBM brain tumor initiating cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 444. doi:10.1158/1538-7445.AM2015-444

Abstract 3153: Slit-2 directs the migration of primary cultured human GBM tumor initiating cells

Glioblastoma multiforme (GBM), the most aggressive and proliferative primary brain tumor, has an extremely high recurrence incidence. This is mainly due to cancer cell invasion of brain parenchyma beyond surgical boundaries. Brain tumor initiating cells (BTICs) are stem-like cells with properties of self-renewal and multipotency. BTICs are able to migrate to initiate tumor formation away from the original tumor and are highly resistant to chemo and radiotherapy, suggesting that they are responsible for tumor recurrence. Understanding the mechanisms affecting the migration of BTICs may shed light on mechanisms for preventing GBM recurrence. Cell migration and proliferation events present during brain development are recapitulated in the fundamental hallmarks of cancer. In rodents, Slit-Robo signaling functions as a chemorepulsive ligand-receptor system involved in guiding the migration of newly generated cells from the subventricular zone to other regions of the central nervous system. In neural cancers, Slit2 affects the migration of glioma and medulloblastoma cell lines. We hypothesized that Slit proteins have a chemorepellant effect on primary-cultured human GBM-derived BTICs, which promotes tumor dispersal. Primary BTIC cultures were established from GBM intraoperative samples and maintained in neurosphere culture media containing EGF and bFGF, heparin and LIF, which maintains the presence of stem cells. Expression of Slit and Robo was then evaluated at the mRNA and protein level. Our results revealed that Slit2 induces a chemorepulsive effect on Robo-expressing BTICs, as evaluated by transwell migration and chemotaxis assays (p Citation Format: Hugo Guerrero-Cazares, Vivian Capilla-Gonzalez, Emily A. Lavell, Alejandro Ruiz-Valls, Linda Chen, Gabrielle Drummond, Sural Ranamukhaarachchi, Alfredo Quinones-Hinojosa. Slit-2 directs the migration of primary cultured human GBM tumor initiating cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3153. doi:10.1158/1538-7445.AM2014-3153