ABSTRACT
BACKGROUND AIMS: Hippocampal neurodegeneration is one of the hallmarks in neurological and neurodegenerative diseases such as temporal lobe epilepsy and Alzheimer disease. Human embryonic kidney (HEK) cells are a mixed population of cells, including neurons, and their conditioned medium is enriched with erythropoietin (EPO). Because EPO is a known neuroprotectant, we hypothesized that infusion of HEK cells or HEK-conditioned medium (HEK-CM) may provide neuroprotection against kainic acid (KA)-induced hippocampal damage in mice. METHODS: Adult CF1 mice were treated with KA to induce hippocampal damage. On 3rd and 5th days after KA treatment, HEK cells or HEK-CM was infused intravenously through the tail vein. On the 7th and 8th days after KA treatment, all groups of mice were subjected to cognitive and depression assessment by use of a novel object recognition test and a forced swim test, respectively. Subsequent to this assessment, mice were killed and the brain samples were used to assess the histopathology and messenger RNA expression for EPO and B-cell lymphoma-2 (Bcl-2). RESULTS: We found that infusion of HEK cells/HEK-CM improves cognitive function and alleviates symptoms of depression. Histological assessment demonstrates complete neuroprotection against KA-mediated excitotoxicity, and the hippocampal cytoarchitecture of HEK cells/HEK-CM treated mice was comparable to normal control mice. HEK cells/HEK-CM treatment could provide neuroprotection by upregulating the endogenous EPO and Bcl-2 in KA-treated mice. CONCLUSIONS: Our present data demonstrate for the first time that infusion of HEK cells/HEK-CM can prevent excitotoxic hippocampal damage and alleviate consequent behavioral abnormalities.
Subject(s)
Brain Injuries , Culture Media, Conditioned , Excitatory Amino Acid Agonists/adverse effects , Hippocampus/injuries , Kainic Acid/adverse effects , Animals , Brain Injuries/chemically induced , Brain Injuries/drug therapy , Brain Injuries/metabolism , Culture Media, Conditioned/chemistry , Culture Media, Conditioned/pharmacology , Excitatory Amino Acid Agonists/pharmacology , HEK293 Cells , Hippocampus/metabolism , Humans , Kainic Acid/pharmacology , Male , Mice , Time FactorsABSTRACT
Stem cell therapy is gaining attention as a promising treatment option for neurodegenerative diseases. The functional efficacy of grafted cells is a matter of debate and the recent consensus is that the cellular and functional recoveries might be due to "by-stander" effects of grafted cells. In the present study, we investigated the neuroprotective effect of conditioned medium (CM) derived from human embryonic kidney (HEK) cells in a kainic acid (KA) induced hippocampal degeneration model system in in vitro condition. Hippocampal cell line was exposed to KA (200 µM) for 24 hrs (lesion group) whereas, in the treatment group, hippocampal cell line was exposed to KA in combination with HEK-CM (KA + HEK-CM). We observed that KA exposure to cells resulted in significant neuronal loss. Interestingly, HEK-CM cotreatment completely attenuated the excitotoxic effects of KA. In HEK-CM cotreatment group, the cell viability was ~85-95% as opposed to 47% in KA alone group. Further investigation demonstrated that treatment with HEK-CM stimulated the endogenous cell survival factors like brain derived neurotrophic factors (BDNF) and antiapoptotic factor Bcl-2, revealing the possible mechanism of neuroprotection. Our results suggest that HEK-CM protects hippocampal neurons against excitotoxicity by stimulating the host's endogenous cell survival mechanisms.
