Study on Effects of Metformin and Transplantation of NPCs Separately and in Combination on Restores Cognitive Dysfunction and Histopathological Deficits in Mouse Model of Sporadic Alzheimer’s Disease

Abstract

[eng] LOAD is a type of metabolic disorder known as type 3 diabetes. Metformin, a well-known anti-diabetic medication, has been introduced as a neuroprotective agent in recent years. On the hand, identifying the factors and solutions that can improve the amount of signaling and cognitive function through preserving brain energy and restoring/replacing the lost neurons can provide a clear perspective for the treatment of this disease. Since metformin has brought good results in insulin resistance treatment (T2DM) and shown an effective role in the process of neurogenesis, the simultaneous treatment of NPCs transplantation along with the metformin injection which improves the process of neurogenesis has been evaluated for improves cognition and memory. In addition, treatment with metformin and transplantation of NPCs were investigated separately. The goal of the current study was to evaluate effects of metformin, NPCs transplantation and metformin+NPCs transplantation on sporadic mouse model of Alzheimer’s disease (SAD) using behavioral, histological and immunofluorescence studies. Five groups of mice including Control (no treatment); sporadic AD (receiving streptozotocin (0.5 mg/kg) on days 1 and 3; STZ+MET (received STZ and metformin (MET) 200 mg/kg per day) for two weeks; STZ+NPCs (received STZ and NPCs transplantation in hippocampus (100,000 in each side) and STZ+MET+NPCs (received STZ, metformin and NPCs simultaneously) were assigned. Novel objective recognition (NOR) and Barnes Maze test were used to test learning and memory. Nissl staining was used as a histological method for counting the dark neurons (dark purple stained neuros known as dead cells) in different regions of hippocampus in five experimental groups. Immunofluorescence staining against glial fibrillary acidic protein (GFAP), ionized calcium binding adaptor molecule 1 (Iba1) and NeuN were used to visualize reactive astrocytes, microglia (gliosis) and neurons, respectively. In NOR test, the percentage of discrimination index in the STZ group was significantly lower than the control and treatment groups. In addition, the discrimination index percentage for the novel object in STZ was significantly lower than other groups, while in treated group it was still less than the Control. The Goal sector/non-goal sector (GS/NGS) ratio index in Barns maze was significantly higher in metformin treatment group compared to other two treatment groups while scape latency was not significantly different between the groups. Traveled distance was significantly higher in metformin group. The results of Nissl staining demonstrated the number of dead neurons was significantly increased after STZ induction and metformin and transplantation of NPCs treatment has been able significantly reduce the number of dead neurons vs STZ group. In STZ group, GFAP level was significantly higher in CA1+DG, CA3 and cortex as compared to Control and reversed in treated groups with significantly reduction in STZ+MET, STZ+NPCs and STZ+NPCs+MET as compared to STZ group. IBA1 level was significantly higher in STZ group in CA3, and cortex regions compared to Control. Moreover, metformin significantly decreased the intensity of IBA1 in CA3 and cortex vs STZ group. NPCs transplantation also significantly reduced the IBA1 intensity in CA1+DG and cortex. Counting NeuN+ cells significantly demonstrated reduction of number of neurons in DG+CA1, CA3 and cortex after STZ induction. NPCs transplantation in both STZ+NPCs and STZ+NPCs+MET significantly increased the number of neurons vs STZ group in CA1+DG and CA3 regions. Metformin also increased the number of neurons in limited range and non-significantly. Conclusion: Metformin decreased inflammatory cells and reactive astrocytes as well as the dark neurons in the hippocampus region and the cortex in STZ model of sporadic AD and improved cognitive performance. Transplantation of NPCs separately and together with metformin injection also reduced inflammation in the hippocampus. And on the other hand, following the NPCs transplantation, neurogenesis in CA1+DG and CA3 areas of the hippocampus was strengthened, and the lost neurons were replaced. In this regard, improvement in cognitive memory and learning was evident in these two linked groups. In general, therefore, in the field of cognition and memory according to the new object recognition behavioral test, stem cell transplant alone showed better results than stem cell transplant combined with metformin injection and compared to metformin treatment alone. On the other hand, metformin has been helpful in learning.

[spa] LOAD es un tipo de trastorno metabólico conocido como diabetes tipo 3. La metformina, un conocido medicamento antidiabético, se ha introducido como agente neuroprotector en los últimos años. Por otro lado, identificar los factores y soluciones que pueden mejorar la cantidad de señalización y la función cognitiva mediante la preservación de la energía cerebral y la restauración/reemplazo de las neuronas perdidas puede proporcionar una perspectiva clara para el tratamiento de esta enfermedad. Dado que la metformina ha dado buenos resultados en el tratamiento de la resistencia a la insulina (DM2) y ha demostrado un papel eficaz en el proceso de neurogénesis, se ha evaluado el tratamiento simultáneo del trasplante de NPC junto con la inyección de metformina, que mejora el proceso de neurogénesis, para mejorar la cognición y la memoria. Además, el tratamiento con metformina y el trasplante de NPC se investigaron por separado. El objetivo del estudio actual fue evaluar los efectos de la metformina, el trasplante de NPC y el trasplante de metformina + NPC en un modelo de ratón esporádico de la enfermedad de Alzheimer (SAD) mediante estudios de comportamiento, histológicos e inmunofluorescencia.