Endothelial Progenitor Cells Conditioned Medium Supports Number of GABAergic Neurons and Exerts Neuroprotection in Cultured Striatal Neuronal Progenitor Cells

Abstract

There is growing evidence that stem and progenitor cells exert regenerative actions by means of paracrine factors. In line with these notions, we recently demonstrated that endothelial progenitor cell (EPC)-derived conditioned medium (EPC-CM) substantially increased viability of brain microvascular cells. In the present study, we aimed at investigating whether EPC-CM supports cell survival of cultured striatal progenitor cells. For that purpose, primary cultures from fetal rat embryonic (E14) ganglionic eminence were prepared and grown for 7 days in vitro (DIV). EPC-CM was administered from DIV5–7. Treatment of the striatal cultures with EPC-CM resulted in significantly increased densities of GABA-immunoreactive (-ir) neurons. Inhibition of mitogen-activated protein kinase and phosphatidylinositol-3-kinase, but not of the ROCK pathway, significantly attenuated the EPC-CM induced increase in GABA-ir cell densities. Similar results were observed when EPC-CM was subjected to proteolytic digestion and lipid extraction. Furthermore, inhibition of translation abolished the EPC-CM induced effects. Importantly, EPC-CM displayed neuroprotection against 3-nitropropionic acid induced toxicity. These findings demonstrate that EPC-derived paracrine factors substantially promote survival and/or differentiation of cultured striatal progenitor cells involving both proteinaceous factors and lipidic factors. In sum, EPC-CM constituents might lead to a novel cell-free therapeutic strategy to challenge neuronal degeneration.

Endothelial Progenitor Cell-Derived Factors Exert Neuroprotection in Cultured Cortical Neuronal Progenitor Cells

“…Further experiments will be needed to verify whether EPC-CM promotes the proliferation of immature neurons in cortical cultures and to evaluate the possible role of lipids and other factors. On the other hand, the finding that EPC-CM induced a prominent increase of microglia cell numbers was not surprising and in line with our past report 7 . In fact, we have previously reported that several immunomodulatory cytokines are secreted from EPC 7 , 8 .…”

“…Notably and to our knowledge for the first time, we could demonstrate that EPC-CM disclosed the capacity to confer neuroprotection from a metabolic insult. These results extend our previous observations regarding survival-promoting capacity of paracrine factors released by peripheral blood-derived EPC on striatal and ventral mesencephalic neuronal cells 7 8 . The mechanisms and pathways involved in higher GABA-ir cell densities found with EPC-CM supplementation in cultures challenged by GSD, however, were not addressed in the present study.…”

“…The identification of the factors for the survival improvement of neuronal progenitors was not specifically addressed in our paper. However, our earlier study identified lipidic factors as important mediators of the actions of EPC-CM 7 . Moreover, we have previously shown that EPC-CM contains a number of neurotrophic factors including brain-derived neurotrophic factor glial cell line-derived neurotrophic factor, neuritin, and vascular endothelial growth factor, which are critical for the developing cerebral cortex 8 , 30 .…”

“…We have recently shown that EPC-CM exerted neuroprotection for cultured striatal progenitor cells 7 . Hence, we assessed whether EPC-CM administration offers a survival-promoting potential also for cerebral cortical cultures.…”

“…In addition, endothelial progenitor cells (EPC) and their soluble factors have also been successfully used in traumatic brain injury, ischemic stroke, and white matter damage models 3 – 6 . We have recently demonstrated that the conditioned medium of peripheral blood- derived EPC (EPC-CM) promotes viability of neurons in primary cultures from the ventral mesencephalic as well as the ganglionic eminence and importantly, in these cultures EPC-CM elicited neuroprotective responses against neurotoxic insults induced by 1-methyl-4-phenyl pyridinium and 3-nitropropionic acid treatment, respectively 7 , 8 .…”