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1.
Exp Eye Res ; 209: 108678, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34153289

RESUMO

Geographic atrophy (GA) is an advanced form of age-related macular degeneration (AMD) characterized by atrophy of the retinal pigment epithelium (RPE), loss of photoreceptors, and disruption of choriocapillaris. Excessive light exposure is toxic to the retina and is a known risk factor for AMD. We first investigated the effects of blue light-induced phototoxicity on RPE and photoreceptors in nonhuman primates (NHPs, a model of progressive retinal degeneration) and then evaluated the potential cyto- and neuroprotective effects of the brimonidine drug delivery system (Brimo DDS). In the first set of experiments related to model development, parafoveal lesions of varying severity were induced using blue light irradiation of the retina of cynomolgus monkeys to evaluate the level of phototoxicity in the RPE and photoreceptors. RPE damage was assessed using fundus autofluorescence imaging to quantify areas of hypofluorescence, while thinning of the outer nuclear layer (ONL, photoreceptor nuclei) was quantified using optical coherence tomography (OCT). Photoreceptor function was assessed using multifocal electroretinography (mfERG). RPE damage progressively increased across all lesion severities from 2 to 12 weeks, as did the extent of ONL thinning. Lesions of high severity continued to show reduction in mfERG amplitude, reaching a statistically significant maximum reduction at 12 weeks. Collectively, the first set of experiments showed that blue light irradiation of the NHP eye resulted in progressive retinal degeneration identified by damage to RPE, ONL thinning, and disrupted photoreceptor function - hallmarks of GA in humans. We then used the model to evaluate the cyto- and neuroprotective effects of Brimo DDS, administered as a therapeutic after allowing the lesions to develop for 5 weeks. Placebo DDS or Brimo DDS were administered intravitreally and a set of untreated animals were used as an additional control. In the placebo DDS group, hypofluorescence area continued to increase from baseline, indicating progressive RPE damage, while progression was significantly slowed in eyes receiving Brimo DDS. Likewise, ONL thinning continued to progress over time in eyes that received the placebo DDS, but was reduced in Brimo DDS-treated eyes. Pharmacologically relevant brimonidine concentrations were sustained in the retina for up to 26 weeks following Brimo DDS administration. In summary, Brimo DDS demonstrated cyto- and neuroprotective effects in a novel NHP GA model of progressive retinal degeneration.


Assuntos
Tartarato de Brimonidina/administração & dosagem , Corioide/diagnóstico por imagem , Citoproteção/efeitos dos fármacos , Sistemas de Liberação de Medicamentos , Atrofia Geográfica/tratamento farmacológico , Neuroproteção/efeitos dos fármacos , Segmento Externo das Células Fotorreceptoras da Retina/patologia , Agonistas de Receptores Adrenérgicos alfa 2/administração & dosagem , Animais , Corioide/efeitos dos fármacos , Corioide/efeitos da radiação , Modelos Animais de Doenças , Eletrorretinografia , Angiofluoresceinografia/métodos , Fundo de Olho , Atrofia Geográfica/diagnóstico , Macaca fascicularis , Soluções Oftálmicas/administração & dosagem , Segmento Externo das Células Fotorreceptoras da Retina/efeitos dos fármacos , Segmento Externo das Células Fotorreceptoras da Retina/efeitos da radiação , Epitélio Pigmentado da Retina/efeitos dos fármacos , Epitélio Pigmentado da Retina/patologia , Epitélio Pigmentado da Retina/efeitos da radiação , Tomografia de Coerência Óptica/métodos , Acuidade Visual
2.
Exp Eye Res ; 195: 108031, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32275921

RESUMO

The purpose of this study was to characterize and develop a primate model of chronic retinal neovascularization and vascular leakage that can be employed to assess efficacy of experimental therapeutics targeting retinal ischemic and neovascular diseases. African green monkeys received bilateral intravitreal (IVT) injection of DL-alpha-aminoadipic acid (DLAAA; 5 mg) following ophthalmic examination, color fundus photography, fluorescein angiography (FA) and optical coherence tomography (OCT). Imaging was repeated to evaluate progression and subsequent stabilization of retinal vascular pathology elicited by DLAAA. Aflibercept (Eylea) was administered IVT (1.4 mg) to assess effects on vascular leakage. Ocular tissue was collected for histopathology and glial fibrillary acidic protein (GFAP), von Willebrand Factor (vWF), CD105/endoglin, VEGF and CD68 immunohistochemistry to study retinal degeneration and vascular remodeling. IVT DLAAA administration resulted in telangiectatic vessel formation as early as two-weeks post-injection, followed by retinal vascular leakage and inner retinal edema. Neovascular lesion progression was evident up to 8-10 weeks post-injection before stabilizing into a vascular leakage state that persisted beyond 90 weeks. Histopathology and immunostaining revealed retinal degeneration and neovascularization, increased expression of vWF, CD105/endoglin, VEGF and CD68 immunoreactivities in addition to Müller cell loss. Aflibercept significantly attenuated vascular leakage for 2-4 weeks before progressive return of leakage from weeks 4-8. Lesions remained responsive to anti-VEGF administration at 90 weeks after DLAAA injection. Findings support application of the primate DLAAA-induced retinal vascular leakage model for efficacy evaluations of candidate therapeutics and sustained release strategies targeting exudative AMD, diabetic retinopathy, macular telangiectasia and other retinal ischemic and neovascular diseases. Findings confirm relevance of the DLAAA primate phenotype to understanding shared retinal vascular disease mechanisms and macular susceptibility to vascular and metabolic insults.


Assuntos
Angiofluoresceinografia/métodos , Neovascularização Retiniana/diagnóstico , Vasos Retinianos/patologia , Tomografia de Coerência Óptica/métodos , Animais , Chlorocebus aethiops , Doença Crônica , Modelos Animais de Doenças , Feminino , Fundo de Olho , Masculino
3.
Pharm Res ; 36(4): 58, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30805711

RESUMO

Preclinical models of human diseases are critical to our understanding of disease etiology, pathology, and progression and enable the development of effective treatments. An ideal model of human disease should capture anatomical features and pathophysiological mechanisms, mimic the progression pattern, and should be amenable to evaluating translational endpoints and treatment approaches. Preclinical animal models have been developed for a variety of human ophthalmological diseases to mirror disease mechanisms, location of the affected region in the eye and severity. These models offer clues to aid in our fundamental understanding of disease pathogenesis and enable progression of new therapies to clinical development by providing an opportunity to gain proof of concept (POC). Here, we review preclinical animal models associated with development of new therapies for diseases of the ocular surface, glaucoma, presbyopia, and retinal diseases, including diabetic retinopathy and age-related macular degeneration (AMD). We have focused on summarizing the models critical to new drug development and described the translational features of the models that contributed to our understanding of disease pathogenesis and establishment of preclinical POC.


Assuntos
Modelos Animais de Doenças , Descoberta de Drogas/métodos , Oftalmopatias/tratamento farmacológico , Animais , Pesquisa Translacional Biomédica
4.
Proc Natl Acad Sci U S A ; 106(45): 19150-5, 2009 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-19901336

RESUMO

Cranial irradiation remains a frontline treatment for the control of tumor growth, and individuals surviving such treatments often manifest various degrees of cognitive dysfunction. Radiation-induced depletion of stem/precursor cell pools in the brain, particularly those residing in the neurogenic region of the hippocampus, is believed, in part, to be responsible for these often-unavoidable cognitive deficits. To explore the possibility of ameliorating radiation-induced cognitive impairment, athymic nude rats subjected to head only irradiation (10 Gy) were transplanted 2 days afterward with human embryonic stem cells (hESC) into the hippocampal formation and analyzed for stem cell survival, differentiation, and cognitive function. Animals receiving hESC transplantation exhibited superior performance on a hippocampal-dependent cognitive task 4 months postirradiation, compared to their irradiated surgical counterparts that did not receive hESCs. Significant stem cell survival was found at 1 and 4 months postirradiation, and transplanted cells showed robust migration to the subgranular zone throughout the dentate gyrus, exhibiting signs of neuron morphology within this neurogenic niche. These results demonstrate the capability to ameliorate radiation-induced normal tissue injury using hESCs, and suggest that such strategies may provide useful interventions for reducing the adverse effects of irradiation on cognition.


Assuntos
Transtornos Cognitivos/terapia , Irradiação Craniana/efeitos adversos , Células-Tronco Embrionárias/fisiologia , Transplante de Células-Tronco/métodos , Animais , Bromodesoxiuridina , Diferenciação Celular/fisiologia , Sobrevivência Celular , Transtornos Cognitivos/etiologia , Hipocampo/efeitos da radiação , Humanos , Imuno-Histoquímica , Ratos , Ratos Nus , Resultado do Tratamento
5.
J Neurosci ; 28(12): 3051-9, 2008 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-18354008

RESUMO

Alzheimer's disease (AD) is characterized by the accumulation of plaques containing beta-amyloid (Abeta) and neurofibrillary tangles (NFTs) consisting of modified tau. Although Abeta deposition is thought to precede the formation of NFTs in AD, the molecular steps connecting these two pathologies is not known. Previous studies have suggested that caspase activation plays an important role in promoting the pathology associated with AD. To further understand the contribution of caspases in disease progression, a triple transgenic Alzheimer's mouse model overexpressing the anti-apoptotic protein Bcl-2 was generated. Here we show that overexpression of Bcl-2 limited caspase-9 activation and reduced the caspase cleavage of tau. Moreover, overexpression of Bcl-2 attenuated the processing of APP (amyloid precursor protein) and tau and reduced the number of NFTs and extracellular deposits of Abeta associated with these animals. In addition, overexpression of Bcl-2 in 3xTg-AD mice improved place recognition memory. These findings suggest that the activation of apoptotic pathways may be an early event in AD and contributes to the pathological processes that promote the disease mechanisms underlying AD.


Assuntos
Doença de Alzheimer , Modelos Animais de Doenças , Regulação da Expressão Gênica/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Comportamento Animal , Caspases/metabolismo , Ensaio de Imunoadsorção Enzimática/métodos , Fluoresceínas , Humanos , Infarto da Artéria Cerebral Média/metabolismo , Infarto da Artéria Cerebral Média/fisiopatologia , Memória/fisiologia , Camundongos , Camundongos Transgênicos , Compostos Orgânicos , Presenilina-1/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas tau/genética
6.
J Neurosci ; 28(14): 3555-66, 2008 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-18385314

RESUMO

Aged canines (dogs) accumulate human-type beta-amyloid (Abeta) in diffuse plaques in the brain with parallel declines in cognitive function. We hypothesized that reducing Abeta in a therapeutic treatment study of aged dogs with preexisting Abeta pathology and cognitive deficits would lead to cognitive improvements. To test this hypothesis, we immunized aged beagles (8.4-12.4 years) with fibrillar Abeta(1-42) formulated with aluminum salt (Alum) for 2.4 years (25 vaccinations). Cognitive testing during this time revealed no improvement in measures of learning, spatial attention, or spatial memory. After extended treatment (22 vaccinations), we observed maintenance of prefrontal-dependent reversal learning ability. In the brain, levels of soluble and insoluble Abeta(1-40) and Abeta(1-42) and the extent of diffuse plaque accumulation was significantly decreased in several cortical regions, with preferential reductions in the prefrontal cortex, which is associated with a maintenance of cognition. However, the amount of soluble oligomers remained unchanged. The extent of prefrontal Abeta was correlated with frontal function and serum anti-Abeta antibody titers. Thus, reducing total Abeta may be of limited therapeutic benefit to recovery of cognitive decline in a higher mammalian model of human brain aging and disease. Immunizing animals before extensive Abeta deposition and cognitive decline to prevent oligomeric or fibrillar Abeta formation may have a greater impact on cognition and also more directly evaluate the role of Abeta on cognition in canines. Alternatively, clearing preexisting Abeta from the brain in a treatment study may be more efficacious for cognition if combined with a second intervention that restores neuron health.


Assuntos
Envelhecimento , Peptídeos beta-Amiloides/imunologia , Peptídeos beta-Amiloides/metabolismo , Encéfalo/efeitos dos fármacos , Cognição/fisiologia , Imunização , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/metabolismo , Análise de Variância , Animais , Comportamento Animal/fisiologia , Encéfalo/imunologia , Encéfalo/metabolismo , Comportamento de Escolha/fisiologia , Aprendizagem por Discriminação/fisiologia , Cães , Ensaio de Imunoadsorção Enzimática/métodos , Feminino , Esquemas de Imunização , Estudos Longitudinais , Masculino , Memória/fisiologia , Emaranhados Neurofibrilares/patologia , Testes Neuropsicológicos
7.
Trends Neurosci ; 30(9): 464-72, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17765329

RESUMO

Human and other animal studies demonstrate that exercise targets many aspects of brain function and has broad effects on overall brain health. The benefits of exercise have been best defined for learning and memory, protection from neurodegeneration and alleviation of depression, particularly in elderly populations. Exercise increases synaptic plasticity by directly affecting synaptic structure and potentiating synaptic strength, and by strengthening the underlying systems that support plasticity including neurogenesis, metabolism and vascular function. Such exercise-induced structural and functional change has been documented in various brain regions but has been best-studied in the hippocampus - the focus of this review. A key mechanism mediating these broad benefits of exercise on the brain is induction of central and peripheral growth factors and growth factor cascades, which instruct downstream structural and functional change. In addition, exercise reduces peripheral risk factors such as diabetes, hypertension and cardiovascular disease, which converge to cause brain dysfunction and neurodegeneration. A common mechanism underlying the central and peripheral effects of exercise might be related to inflammation, which can impair growth factor signaling both systemically and in the brain. Thus, through regulation of growth factors and reduction of peripheral and central risk factors, exercise ensures successful brain function.


Assuntos
Encéfalo/fisiologia , Exercício Físico/fisiologia , Inflamação/fisiopatologia , Fatores de Crescimento Neural/fisiologia , Animais , Encéfalo/crescimento & desenvolvimento , Depressão/fisiopatologia , Depressão/terapia , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Fatores de Risco
8.
Invest Ophthalmol Vis Sci ; 59(15): 5836-5846, 2018 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-30535424

RESUMO

Purpose: DARPin molecules are a novel class of small proteins that contain engineered ankyrin repeat domain(s) and bind to target proteins with high specificity and affinity. Abicipar-pegol (abicipar), a DARPin molecule targeting vascular endothelial growth factor-A (VEGF-A), is currently under evaluation in patients with age-related macular degeneration. The pharmacodynamic properties of abicipar were characterized using in vivo and in vitro assays. Methods: The binding affinity of abicipar was assessed using a kinetic exclusion assay (KinExA). In vitro assays evaluated abicipar effects on VEGF-A165-induced calcium mobilization and tube formation in human umbilical vein endothelial cells. Abicipar was tested in vivo in a mouse model of corneal neovascularization and a rabbit model of chronic retinal neovascularization. The efficacies of abicipar and ranibizumab were compared in a rabbit model of VEGF-A165-induced retinal vasculopathy. Results: Abicipar has a high affinity for the soluble isoforms of VEGF-A; binding affinities for human VEGF-A165 are approximately 100-fold greater than those of ranibizumab and bevacizumab and are similar for rat VEGF-A164 but approximately 20-fold lower for rabbit VEGF-A165. Abicipar was effective in cell-based and in vivo models of angiogenesis and vascular leak, blocking neovascularization in a mouse model of corneal neovascularization and vascular permeability in a rabbit model of chronic neovascularization. In a rabbit model of VEGF-A165-induced vasculopathy, the duration of effect of abicipar was longer than ranibizumab when the two compounds were administered at molar-equivalent doses. Conclusions: These data support the testing of abicipar as a treatment for retinal diseases characterized by neovascularization and vascular leak.


Assuntos
Inibidores da Angiogênese/uso terapêutico , Permeabilidade Capilar/efeitos dos fármacos , Neovascularização da Córnea/tratamento farmacológico , Proteínas Nucleares/antagonistas & inibidores , Proteínas Recombinantes de Fusão/uso terapêutico , Neovascularização Retiniana/tratamento farmacológico , Fator A de Crescimento do Endotélio Vascular/antagonistas & inibidores , Animais , Bevacizumab/uso terapêutico , Vasos Sanguíneos/fisiopatologia , Cálcio/metabolismo , Neovascularização da Córnea/fisiopatologia , Modelos Animais de Doenças , Células Endoteliais da Veia Umbilical Humana , Humanos , Camundongos , Coelhos , Ranibizumab/uso terapêutico , Neovascularização Retiniana/fisiopatologia
9.
Artigo em Inglês | MEDLINE | ID: mdl-15795052

RESUMO

We compared performance of younger and older human participants to that of younger and older dogs on tasks that evaluate object discrimination, egocentric spatial ability, object recognition, spatial memory, and cognitive flexibility. Our goal was to determine whether (i) tasks sensitive to advanced age in dogs are also age-sensitive in humans; (ii) the pattern of task difficulty observed in dogs mirrors that observed in humans; (iii) dogs and humans use similar strategies to solve equivalent tasks. Dogs performed more poorly than humans on reversal tasks that evaluate cognitive flexibility. We suggest that dogs, most notably older dogs, use different strategies than healthy humans when solving these tasks. Humans appear to test a priori hypotheses to solve the task at hand. As a consequence, expectations about the complexity of the task being tested can impair human performance. By contrast, dogs appear to rely more heavily on either simpler hypotheses, or associative trial and error learning, which probably accounts for their difficulty in learning non-matching tasks. Dogs also show perseverative responding, which hinders the acquisition of reversal tasks.


Assuntos
Envelhecimento/fisiologia , Transtornos Cognitivos/fisiopatologia , Aprendizagem por Discriminação/fisiologia , Testes Neuropsicológicos , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Cães , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Especificidade da Espécie
10.
Artigo em Inglês | MEDLINE | ID: mdl-15795044

RESUMO

Spatial discriminations can be performed using either egocentric information based on body position or allocentric information based on the position of landmarks in the environment. Beagle dogs ranging from 2 to 16 years of age were tested for their ability to learn a novel egocentric spatial discrimination task that used two identical blocks paired in three possible spatial positions (i.e. left, center and right). Dogs were rewarded for responding to an object furthest to either their left or right side. Therefore, when the center location was used, it was correct on half of the trials and incorrect on the other half. Upon successful acquisition of the task, the reward contingencies were reversed, and the dogs were rewarded for responding to the opposite side. A subset of dogs was also tested on an allocentric spatial discrimination task, landmark discrimination. Egocentric spatial reversal learning and allocentric discrimination learning both showed a significant age-dependent decline, while initial egocentric learning appeared to be age-insensitive. Intra-subject correlation analyses revealed a significant relationship between egocentric reversal learning and allocentric learning. However, the correlation only accounted for a small proportion of the variance, suggesting that although there might be some common mechanism underlying acquisition of the two tasks, additional unique neural substrates were involved depending on whether allocentric or egocentric spatial information processing was required.


Assuntos
Envelhecimento/fisiologia , Aprendizagem por Discriminação/fisiologia , Rememoração Mental/fisiologia , Orientação/fisiologia , Comportamento Espacial/fisiologia , Análise de Variância , Animais , Comportamento Animal , Cães , Tempo de Reação/fisiologia , Análise de Regressão
11.
Cancer Res ; 75(4): 676-86, 2015 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-25687405

RESUMO

The frequent use of chemotherapy to combat a range of malignancies can elicit severe cognitive dysfunction often referred to as "chemobrain," a condition that can persist long after the cessation of treatment in as many as 75% of survivors. Although cognitive health is a critical determinant of therapeutic outcome, chemobrain remains an unmet medical need that adversely affects quality of life in pediatric and adult cancer survivors. Using a rodent model of chemobrain, we showed that chronic cyclophosphamide treatment induced significant performance-based decrements on behavioral tasks designed to interrogate hippocampal and cortical function. Intrahippocampal transplantation of human neural stem cells resolved all cognitive impairments when animals were tested 1 month after the cessation of chemotherapy. In transplanted animals, grafted cells survived (8%) and differentiated along neuronal and astroglial lineages, where improved cognition was associated with reduced neuroinflammation and enhanced host dendritic arborization. Stem cell transplantation significantly reduced the number of activated microglia after cyclophosphamide treatment in the brain. Granule and pyramidal cell neurons within the dentate gyrus and CA1 subfields of the hippocampus exhibited significant reductions in dendritic complexity, spine density, and immature and mature spine types following chemotherapy, adverse effects that were eradicated by stem cell transplantation. Our findings provide the first evidence that cranial transplantation of stem cells can reverse the deleterious effects of chemobrain, through a trophic support mechanism involving the attenuation of neuroinflammation and the preservation host neuronal architecture.


Assuntos
Transtornos Cognitivos/terapia , Ciclofosfamida/efeitos adversos , Neoplasias/tratamento farmacológico , Células-Tronco Neurais/transplante , Transplante de Células-Tronco , Animais , Comportamento Animal/efeitos dos fármacos , Transtornos Cognitivos/induzido quimicamente , Ciclofosfamida/administração & dosagem , Modelos Animais de Doenças , Hipocampo/patologia , Hipocampo/transplante , Humanos , Camundongos , Neoplasias/patologia , Neurônios/efeitos dos fármacos , Neurônios/patologia , Qualidade de Vida
12.
Stem Cells Transl Med ; 4(1): 74-83, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25391646

RESUMO

Past preclinical studies have demonstrated the capability of using human stem cell transplantation in the irradiated brain to ameliorate radiation-induced cognitive dysfunction. Intrahippocampal transplantation of human embryonic stem cells and human neural stem cells (hNSCs) was found to functionally restore cognition in rats 1 and 4 months after cranial irradiation. To optimize the potential therapeutic benefits of human stem cell transplantation, we have further defined optimal transplantation windows for maximizing cognitive benefits after irradiation and used induced pluripotent stem cell-derived hNSCs (iPSC-hNSCs) that may eventually help minimize graft rejection in the host brain. For these studies, animals given an acute head-only dose of 10 Gy were grafted with iPSC-hNSCs at 2 days, 2 weeks, or 4 weeks following irradiation. Animals receiving stem cell grafts showed improved hippocampal spatial memory and contextual fear-conditioning performance compared with irradiated sham-surgery controls when analyzed 1 month after transplantation surgery. Importantly, superior performance was evident when stem cell grafting was delayed by 4 weeks following irradiation compared with animals grafted at earlier times. Analysis of the 4-week cohort showed that the surviving grafted cells migrated throughout the CA1 and CA3 subfields of the host hippocampus and differentiated into neuronal (∼39%) and astroglial (∼14%) subtypes. Furthermore, radiation-induced inflammation was significantly attenuated across multiple hippocampal subfields in animals receiving iPSC-hNSCs at 4 weeks after irradiation. These studies expand our prior findings to demonstrate that protracted stem cell grafting provides improved cognitive benefits following irradiation that are associated with reduced neuroinflammation.


Assuntos
Transtornos Cognitivos/etiologia , Irradiação Craniana/efeitos adversos , Células-Tronco Pluripotentes Induzidas/transplante , Lesões Experimentais por Radiação/cirurgia , Transplante de Células-Tronco/métodos , Animais , Transtornos Cognitivos/cirurgia , Xenoenxertos , Hipocampo/cirurgia , Humanos , Imuno-Histoquímica , Microscopia Confocal , Ratos , Ratos Nus
13.
Int J Radiat Biol ; 90(9): 816-20, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24882389

RESUMO

PURPOSE: Radiotherapy remains a primary treatment modality for the majority of central nervous system tumors, but frequently leads to debilitating cognitive dysfunction. Given the absence of satisfactory solutions to this serious problem, we have used human stem cell therapies to ameliorate radiation-induced cognitive impairment. Here, past studies have been extended to determine whether engrafted cells provide even longer-term benefits to cognition. MATERIALS AND METHODS: Athymic nude rats were cranially irradiated (10 Gy) and subjected to intrahippocampal transplantation surgery 2 days later. Human embryonic stem cells (hESC) or human neural stem cells (hNSC) were transplanted, and animals were subjected to cognitive testing on a novel place recognition task 8 months later. RESULTS: Grafting of hNSC was found to provide long lasting cognitive benefits over an 8-month post-irradiation interval. At this protracted time, hNSC grafting improved behavioral performance on a novel place recognition task compared to irradiated animals not receiving stem cells. Engrafted hESC previously shown to be beneficial following a similar task, 1 and 4 months after irradiation, were not found to provide cognitive benefits at 8 months. CONCLUSIONS: Our findings suggest that hNSC transplantation promotes the long-term recovery of the irradiated brain, where intrahippocampal stem cell grafting helps to preserve cognitive function.


Assuntos
Encéfalo/efeitos da radiação , Radioterapia/efeitos adversos , Transplante de Células-Tronco , Animais , Cognição/efeitos da radiação , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/prevenção & controle , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/transplante , Hipocampo/fisiologia , Humanos , Células-Tronco Neurais/citologia , Células-Tronco Neurais/transplante , Neurônios/metabolismo , Lesões Experimentais por Radiação/terapia , Ratos , Ratos Nus
14.
Cell Transplant ; 23(10): 1255-66, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-23866792

RESUMO

Treatment of central nervous system (CNS) malignancies typically involves radiotherapy to forestall tumor growth and recurrence following surgical resection. Despite the many benefits of cranial radiotherapy, survivors often suffer from a wide range of debilitating and progressive cognitive deficits. Thus, while patients afflicted with primary and secondary malignancies of the CNS now experience longer local regional control and progression-free survival, there remains no clinical recourse for the unintended neurocognitive sequelae associated with their cancer treatments. Multiple mechanisms contribute to disrupted cognition following irradiation, including the depletion of radiosensitive populations of stem and progenitor cells in the hippocampus. We have explored the potential of using intrahippocampal transplantation of human stem cells to ameliorate radiation-induced cognitive dysfunction. Past studies demonstrated the capability of cranially transplanted human embryonic (hESCs) and neural (hNSCs) stem cells to functionally restore cognition in rats 1 and 4 months after cranial irradiation. The present study employed an FDA-approved fetal-derived hNSC line capable of large scale-up under good manufacturing practice (GMP). Animals receiving cranial transplantation of these cells 1 month following irradiation showed improved hippocampal spatial memory and contextual fear conditioning performance compared to irradiated, sham surgery controls. Significant newly born (doublecortin positive) neurons and a smaller fraction of glial subtypes were observed within and nearby the transplantation core. Engrafted cells migrated and differentiated into neuronal and glial subtypes throughout the CA1 and CA3 subfields of the host hippocampus. These studies expand our prior findings to demonstrate that transplantation of fetal-derived hNSCs improves cognitive deficits in irradiated animals, as assessed by two separate cognitive tasks.


Assuntos
Transtornos Cognitivos/terapia , Irradiação Craniana/métodos , Células-Tronco Fetais/transplante , Células-Tronco Neurais/transplante , Lesões Experimentais por Radiação/prevenção & controle , Transplante de Células-Tronco/métodos , Animais , Diferenciação Celular/fisiologia , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/prevenção & controle , Proteína Duplacortina , Humanos , Masculino , Lesões Experimentais por Radiação/etiologia , Ratos , Transplante Heterólogo
15.
Transl Cancer Res ; 3(2): 124-137, 2014 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-24904783

RESUMO

Brain tumor patients routinely undergo cranial radiotherapy, and while beneficial, this treatment often results in debilitating cognitive dysfunction. This serious and unresolved problem has at present, no clinical recourse, and has driven our efforts to more clearly define the consequences of different brain irradiation paradigms on specific indices of cognitive performance and on the underlying cellular mechanisms believed to affect these processes. To accomplish this we have developed the capability to deliver highly focused X-ray beams to small and precisely defined volumes of the athymic rat brain, thereby providing more realistic simulations of clinical irradiation scenarios. Using this technique, termed stereotaxic radiosurgery, we evaluated the cognitive consequences of irradiation targeted to the hippocampus in one or both hemispheres of the brain, and compared that to whole brain irradiation. While whole brain irradiation was found to elicit significant deficits in novel place recognition and fear conditioning, standard platforms for quantifying hippocampal and non-hippocampal decrements, irradiation targeted to both hippocampi was only found to elicit deficits in fear conditioning. Cognitive decrements were more difficult to demonstrate in animals subjected to unilateral hippocampal ablation. Immunohistochemical staining for newly born immature (doublecortin positive) and mature (NeuN positive) neurons confirmed our capability to target irradiation to the neurogenic regions of the hippocampus. Stereotaxic radiosurgery (SRS) of the ipsilateral hemisphere reduced significantly the number of doublecortin and NeuN positive neurons by 80% and 27% respectively. Interestingly, neurogenesis on the contralateral side was upregulated in response to stereotaxic radiosurgery, where the number of doublecortin and NeuN positive neurons increased by 22% and 36% respectively. Neuroinflammation measured by immunostaining for activated microglia (ED1 positive cells) was significantly higher on the ipsilateral versus contralateral sides, as assessed throughout the various subfields of the hippocampus. These data suggest that certain cognitive decrements are linked to changes in neurogenesis, and that the unilaterally irradiated brain exhibits distinct neurogenic responses that may be regulated by regional differences in neuroinflammation. Compensatory upregulation of neurogenesis on the contralateral hemisphere may suffice to maintain cognition under certain dose limits. Our results demonstrate unique cognitive and neurogenic consequences as a result of targeted stereotaxic radiosurgery, and suggest that these irradiation paradigms elicit responses distinct from those found after exposing the whole brain to more uniform radiation fields.

16.
Cell Transplant ; 22(1): 55-64, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22546529

RESUMO

Radiotherapy is a frontline treatment for the clinical management of CNS tumors. Although effective in eradicating tumor cells, radiotherapy also depletes neural stem and progenitor cells in the hippocampus that are important for neurogenesis and cognitive function. Consequently, the use of radiation to control primary and metastatic brain tumors often leads to debilitating and progressive cognitive decrements in surviving patients, representing a serious medical condition that, to date, has no satisfactory, long-term solutions. As a result, we have explored the use of stem cells as therapeutic agents to improve cognition after radiotherapy. Our past work has demonstrated the capability of cranially transplanted human embryonic (hESCs) and neural (hNSCs) stem cells to functionally restore cognition in rats 1 and 4 months after head-only irradiation. We have now expanded our cognitive analyses with hESCs and quantified both survival and differentiated fates of engrafted cells at 1 and 4 months after irradiation. Our findings indicate the capability of hESC transplantation to ameliorate radiation-induced cognitive dysfunction 1 month following cranial irradiation, using a hippocampal-dependent novel place recognition task. Irradiated animals not engrafted with stem cells experienced prolonged and significant cognitive dysfunction. Stereological estimates indicated that 35% and 17% of the transplanted hESCs survived at 1 and 4 months postgrafting, respectively. One month after irradiation and grafting, phenotypic analyses revealed that 26% and 31% of the hESCs differentiated into neurons and astrocytes, while at the 4-month time, neuronal and astrocytic differentiation was 7% and 46%, respectively. Comparison between present and past data with hESCs and hNSCs demonstrates equivalent cognitive restoration and a preference of hNSCs to commit to neuronal versus astrocytic lineages over extended engraftment times. Our data demonstrate the functional utility of human stem cell replacement strategies for ameliorating the adverse effects of cranial irradiation on cognition.


Assuntos
Encéfalo/patologia , Encéfalo/efeitos da radiação , Irradiação Craniana/métodos , Lesões Experimentais por Radiação/cirurgia , Transplante de Células-Tronco/métodos , Animais , Encéfalo/metabolismo , Diferenciação Celular/fisiologia , Diferenciação Celular/efeitos da radiação , Modelos Animais de Doenças , Xenoenxertos , Humanos , Masculino , Neurônios/citologia , Neurônios/patologia , Neurônios/efeitos da radiação , Lesões Experimentais por Radiação/etiologia , Lesões Experimentais por Radiação/patologia , Ratos , Ratos Nus
17.
Age (Dordr) ; 34(1): 67-73, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21336566

RESUMO

Aging has been shown to disrupt performance on tasks that require intact visual search and discrimination abilities in human studies. The goal of the present study was to determine if canines show age-related decline in their ability to perform a novel simultaneous visual search task. Three groups of canines were included: a young group (N = 10; 3 to 4.5 years), an old group (N = 10; 8 to 9.5 years), and a senior group (N = 8; 11 to 15.3 years). Subjects were first tested for their ability to learn a simple two-choice discrimination task, followed by the visual search task. Attentional demands in the task were manipulated by varying the number of distracter items; dogs received an equal number of trials with either zero, one, two, or three distracters. Performance on the two-choice discrimination task varied with age, with senior canines making significantly more errors than the young. Performance accuracy on the visual search task also varied with age; senior animals were significantly impaired compared to both the young and old, and old canines were intermediate in performance between young and senior. Accuracy decreased significantly with added distracters in all age groups. These results suggest that aging impairs the ability of canines to discriminate between task-relevant and -irrelevant stimuli. This is likely to be derived from impairments in cognitive domains such as visual memory and learning and selective attention.


Assuntos
Envelhecimento , Atenção , Aprendizagem por Discriminação , Memória , Reconhecimento Visual de Modelos , Visão Ocular , Animais , Percepção de Distância , Cães , Modelos Animais , Fatores de Tempo
18.
Clin Cancer Res ; 18(7): 1954-65, 2012 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-22338017

RESUMO

PURPOSE: A substantial proportion of breast cancer survivors report significant, long-lasting impairments in cognitive function, often referred to as "chemobrain." Advances in detection and treatment mean that many more patients are surviving long-term following diagnosis of invasive breast cancer. Thus, it is important to define the types, extent, and persistence of cognitive impairments following treatment with cytotoxic cancer drugs. EXPERIMENTAL DESIGN: We examined the effects of chronic treatment with two agents commonly used in patients with breast cancer, cyclophosphamide and doxorubicin (Adriamycin). Athymic nude rats were given 50 mg/kg cyclophosphamide, 2 mg/kg doxorubicin, or saline injections once per week for 4 weeks. A novel place recognition task and contextual and cued fear conditioning were used to characterize learning and memory ability. Immunofluorescence staining for immature and mature neurons and activated microglia was used to assess changes in neurogenesis and neuroinflammation. RESULTS: Cyclophosphamide- and doxorubicin-treated rats showed significantly impaired performance on the novel place recognition task and the contextual fear conditioning task compared with untreated controls, suggesting disrupted hippocampal-based memory function. Chemotherapy-treated animals showed a significant decline in neurogenesis [80%-90% drop in bromodeoxyuridine (BrdUrd)-labeled cells expressing NeuN]. Activated microglia (ED1-positive) were found after cyclophosphamide but not doxorubicin treatment. CONCLUSIONS: Our results show that chronic treatment with either of two commonly used chemotherapeutic agents impairs cognitive ability and suggest that strategies to prevent or repair disrupted hippocampal neurogenesis may be effective in ameliorating this serious side effect in cancer survivors.


Assuntos
Antineoplásicos/toxicidade , Transtornos Cognitivos/fisiopatologia , Hipocampo/fisiopatologia , Neurogênese/efeitos dos fármacos , Análise de Variância , Animais , Antineoplásicos/uso terapêutico , Peso Corporal/efeitos dos fármacos , Neoplasias da Mama/tratamento farmacológico , Bromodesoxiuridina/metabolismo , Transtornos Cognitivos/induzido quimicamente , Condicionamento Psicológico/efeitos dos fármacos , Ciclofosfamida/uso terapêutico , Ciclofosfamida/toxicidade , Doxorrubicina/uso terapêutico , Doxorrubicina/toxicidade , Medo/efeitos dos fármacos , Medo/psicologia , Feminino , Imunofluorescência , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Aprendizagem/efeitos dos fármacos , Masculino , Memória/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Ratos , Ratos Nus
19.
J Vis Exp ; (56)2011 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-22042060

RESUMO

With the exception of survival, cognitive impairment stemming from the clinical management of cancer is a major factor dictating therapeutic outcome. For many patients afflicted with CNS and non-CNS malignancies, radiotherapy and chemotherapy offer the best options for disease control. These treatments however come at a cost, and nearly all cancer survivors (~11 million in the US alone as of 2006) incur some risk for developing cognitive dysfunction, with the most severe cases found in patients subjected to cranial radiotherapy (~200,000/yr) for the control of primary and metastatic brain tumors. Particularly problematic are pediatric cases, whose long-term survival plagued with marked cognitive decrements results in significant socioeconomic burdens. To date, there are still no satisfactory solutions to this significant clinical problem. We have addressed this serious health concern using transplanted stem cells to combat radiation-induced cognitive decline in athymic rats subjected to cranial irradiation. Details of the stereotaxic irradiation and the in vitro culturing and transplantation of human neural stem cells (hNSCs) can be found in our companion paper (Acharya et al., JoVE reference). Following irradiation and transplantation surgery, rats are then assessed for changes in cognition, grafted cell survival and expression of differentiation-specific markers 1 and 4-months after irradiation. To critically evaluate the success or failure of any potential intervention designed to ameliorate radiation-induced cognitive sequelae, a rigorous series of quantitative cognitive tasks must be performed. To accomplish this, we subject our animals to a suite of cognitive testing paradigms including novel place recognition, water maze, elevated plus maze and fear conditioning, in order to quantify hippocampal and non-hippocampal learning and memory. We have demonstrated the utility of these tests for quantifying specific types of cognitive decrements in irradiated animals, and used them to show that animals engrafted with hNSCs exhibit significant improvements in cognitive function. The cognitive benefits derived from engrafted human stem cells suggest that similar strategies may one day provide much needed clinical recourse to cancer survivors suffering from impaired cognition. Accordingly, we have provided written and visual documentation of the critical steps used in our cognitive testing paradigms to facilitate the translation of our promising results into the clinic.


Assuntos
Transtornos Cognitivos/diagnóstico , Cognição/efeitos da radiação , Lesões Experimentais por Radiação/diagnóstico , Animais , Transtornos Cognitivos/etiologia , Transtornos Cognitivos/cirurgia , Condicionamento Clássico , Medo , Humanos , Aprendizagem em Labirinto , Lesões Experimentais por Radiação/cirurgia , Ratos , Ratos Endogâmicos , Transplante de Células-Tronco , Transplante Heterólogo
20.
Cancer Res ; 71(14): 4834-45, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21757460

RESUMO

Cranial radiotherapy induces progressive and debilitating declines in cognition that may, in part, be caused by the depletion of neural stem cells. The potential of using stem cell replacement as a strategy to combat radiation-induced cognitive decline was addressed by irradiating athymic nude rats followed 2 days later by intrahippocampal transplantation with human neural stem cells (hNSC). Measures of cognitive performance, hNSC survival, and phenotypic fate were assessed at 1 and 4 months after irradiation. Irradiated animals engrafted with hNSCs showed significantly less decline in cognitive function than irradiated, sham-engrafted animals and acted indistinguishably from unirradiated controls. Unbiased stereology revealed that 23% and 12% of the engrafted cells survived 1 and 4 months after transplantation, respectively. Engrafted cells migrated extensively, differentiated along glial and neuronal lineages, and expressed the activity-regulated cytoskeleton-associated protein (Arc), suggesting their capability to functionally integrate into the hippocampus. These data show that hNSCs afford a promising strategy for functionally restoring cognition in irradiated animals.


Assuntos
Transtornos Cognitivos/etiologia , Transtornos Cognitivos/cirurgia , Células-Tronco Neurais/transplante , Lesões Experimentais por Radiação/cirurgia , Animais , Movimento Celular/fisiologia , Transtornos Cognitivos/metabolismo , Proteínas do Citoesqueleto/metabolismo , Sobrevivência de Enxerto/fisiologia , Hipocampo/citologia , Hipocampo/cirurgia , Humanos , Masculino , Células-Tronco Neurais/citologia , Lesões Experimentais por Radiação/etiologia , Lesões Experimentais por Radiação/metabolismo , Ratos , Ratos Nus
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