Erythropoietin produced by genetic-modified NIH/3T3 fibroblasts enhances the survival of degenerating neurons

Intracerebral transplantation of erythropoietin-producing fibroblasts facilitates neurogenesis and functional recovery in an ischemic stroke model

INTRODUCTION

Erythropoietin (EPO) can enhance neurogenesis and fibroblasts can secrete growth factors; together, they may benefit ischemic stroke. We transplanted EPO-producing fibroblasts into the rodent infarcted brain to test their effect on neurogenesis and functional recovery.

METHODS

A total of 10⁶ cells of EPO-producing NIH/3T3 fibroblasts (EPO/EGFP/3T3) or enhanced green fluorescence protein (EGFP)-expressing fibroblasts (EGFP/3T3) were stereotaxically injected into the infarcted striatum of adult rats that received transient middle cerebral artery occlusion (MCAO) surgery 1 day poststroke. On day 14 after MCAO, the animals were euthanized for the evaluation of neurogenesis via immunohistochemistry and of the expression of growth factors using enzyme-linked immunosorbent assay. The infarct volume was analyzed using magnetic resonance imaging and the neurological behavior was assessed using the neurological severity scoring performed within 14 days after MCAO.

RESULTS

The MCAO rats with EPO/EGFP/3T3 treatment showed high EPO expression in the infarcted brain for at least 1 week. The concentration of brain-derived neurotrophic factor was higher in both hemispheres of MCAO rats with either EGFP/3T3 or EPO/EGFP/3T3 treatment at 14 days poststroke compared with untreated MCAO rats. The number of Ki-67-, nestin-, or doublecortin-immunoreactive cells in bilateral subventricular zones was higher in EPO/EGFP/3T3-treated MCAO rats than it was in untreated MCAO control animals, indicating the enhancement of neurogenesis after EPO/EGFP/3T3 treatment. Notably, post-MCAO EPO/EGFP/3T3 treatment significantly reduced infarct size and improved functional recovery.

CONCLUSION

The intracerebral transplantation of EPO-producing fibroblasts benefited an ischemic stroke model probably via the enhancement of neurogenesis.

Modulation of ERK1/2 and Akt Pathways Involved in the Neurotrophic Action of Caffeic Acid Alkyl Esters

Neurodegenerative diseases affect millions of human lives all over the world. The number of afflicted patients is rapidly growing, and disease-modifying agents are urgently needed. Caffeic acid, an important member of the hydroxycinnamic acid family of polyphenols, has considerable neurotrophic effects. We have previously shown how caffeate alkyl ester derivatives significantly promote survival and differentiation in neuronal cells. In this study, the mechanisms by which these ester derivatives exert their neurotrophic effects are examined. A series of eight caffeic acid esters with different alkyl chain lengths, ranging from methyl (CAF1) to dodecyl esters (CAF8), were synthesized and studied for their influence on neurotrophic signaling pathways. Caffeate esters did not induce tropomyosin-receptor kinase A (TrkA) phosphorylation, which was assessed by immunoblotting up to a concentration of 25 µM. NIH/3T3 cells overexpressing TrkA were generated to further examine phosphorylation of this receptor tyrosine kinase. None of the esters induced TrkA phosphorylation in these cells either. Assessment of the effect of caffeate derivatives on downstream neurotrophic pathways by immunoblotting showed that the most potent esters, decyl caffeate (CAF7) and dodecyl caffeate (CAF8) caused extracellular signal-regulated kinase (ERK1/2) and Akt serine threonine kinase phosphorylation in PC12 cells at 5 and 25 µM concentrations. In conclusion, this study shows that caffeate esters exert their neurotrophic action by modulation of ERK1/2 and Akt signaling pathways in neuronal cells, and further demonstrates the potential therapeutic implications of these derivatives for neurodegenerative diseases.