Conditioned Medium Reconditions Hippocampal Neurons against Kainic Acid Induced Excitotoxicity: AnIn VitroStudy

Abstract

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.

Trkb-IP3 Pathway Mediating Neuroprotection in Rat Hippocampal Neuronal Cell Culture Following Induction of Kainic Acid

“…BDNF and its receptors have been implicated in the development of epilepsy. Conditioned media can protect hippocampal neurons against KA-induced excitotoxicity, stimulating endogenous cell survival factors BDNF and anti-apoptotic Bcl-2 in the host cell ( 19 ). In addition, increased seizure activity has been found to upregulate BDNF mRNA and protein expression in immunoreactivity, and to activate TrkB in the epileptic brain ( 22 , 28 , 36 , 65 , 66 ).…”

“…In addition, it has been reported that epileptogenesis can be caused by changes in homeostatic mechanisms involving calcium ( 18 ). Overloading of glutamate receptor activation by KA receptors induces an influx of cellular Ca 2+ , production of reactive oxygen species (ROS) and mitochondrial dysfunction ( 19 , 20 ). Subsequently, Ca 2+ sequestration mechanisms cause neuronal insult and neuronal death, including, hypoxia, ischemia, and epileptic seizures ( 14 , 18 , 19 , 20 ).…”

“…Overloading of glutamate receptor activation by KA receptors induces an influx of cellular Ca 2+ , production of reactive oxygen species (ROS) and mitochondrial dysfunction ( 19 , 20 ). Subsequently, Ca 2+ sequestration mechanisms cause neuronal insult and neuronal death, including, hypoxia, ischemia, and epileptic seizures ( 14 , 18 , 19 , 20 ). Importantly, KA was found to trigger neurogenesis, reporting that abnormal maturation of dendrites resulted in the occurrence of seizures.…”

“…Several studies have reported that brain derived neurotrophic factor (BDNF) has neuroprotective features, and BDNF mRNA expression has been found to increase after KA exposure ( 19 , 22 , 23 ). Interestingly, BDNF transgenic mice exhibited reduced seizure behaviour in response to KA under conditions of overexpression of truncated TrkB receptors ( 24 ).…”

Conditioned medium of E17 rat brain cells induced differentiation of primary colony of mice blastocyst into neuron-like cells

“…Secretome in a paracrine mechanism can significantly repair the tissues while the differentiation of cells has a minor benefit [ 5 ]. The secretome in conditioned medium may also stimulate the host's endogenous cell survival mechanism [ 6 ]. The majority of the studies reported that the beneficial effect is most likely mediated by modulation of neurotrophic factor expression [ 7 ].…”