Abstract
BackgroundCongenital human cytomegalovirus (HCMV) infection, a leading cause of birth defects, is most often manifested as neurological disorders. The pathogenesis of HCMV-induced neurological disorders is, however, largely unresolved, primarily because of limited availability of model systems to analyze the effects of HCMV infection on neural cells.MethodsAn induced pluripotent stem cell (iPSC) line was established from the human fibroblast line MRC5 by introducing the Yamanaka’s four factors and then induced to differentiate into neural stem/progenitor cells (NSPCs) by dual inhibition of the SMAD signaling pathway using Noggin and SB-431542.ResultsiPSC-derived NSPCs (NSPC/iPSCs) were susceptible to HCMV infection and allowed the expression of both early and late viral gene products. HCMV-infected NSPC/iPSCs underwent apoptosis with the activation of caspase-3 and −9 as well as positive staining by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Cytochrome c release from mitochondria to cytosol was observed in these cells, indicating the involvement of mitochondrial dysfunction in their apoptosis. In addition, phosphorylation of proteins involved in the unfolded protein response (UPR), such as PKR-like eukaryotic initiation factor 2a kinase (PERK), c-Jun NH2-terminal kinase (JNK), inositol-requiring enzyme 1 (IRE1), and the alpha subunit of eukaryotic initiation factor 2 (eIF2α) was observed in HCMV-infected NSPC/iPSCs. These results, coupled with the finding of increased expression of mRNA encoding the C/EBP-homologous protein (CHOP) and the detection of a spliced form of X-box binding protein 1 (XBP1) mRNA, suggest that endoplasmic reticulum (ER) stress is also involved in HCMV-induced apoptosis of these cells.ConclusionsiPSC-derived NSPCs are thought to be a useful model to study HCMV neuropathogenesis and to analyze the mechanisms of HCMV-induced apoptosis in neural cells.
Highlights
Congenital human cytomegalovirus (HCMV) infection, a leading cause of birth defects, is most often manifested as neurological disorders
The results indicated that Neural stem/progenitor cell (NSPC) are susceptible to HCMV infection and undergo apoptosis caused by mitochondrial dysfunction and endoplasmic reticulum (ER) stress
Induced differentiation on induced pluripotent stem cell (iPSC) into neural stem cells MRC-iPSC-25 cells cultured under feeder-free conditions were induced to differentiate into neural stem/progenitor cells (NSPCs) by the method of dual inhibition of the SMAD signaling pathway described previously [16]
Summary
Congenital human cytomegalovirus (HCMV) infection, a leading cause of birth defects, is most often manifested as neurological disorders. The pathogenesis of HCMV-induced neurological disorders is, largely unresolved, primarily because of limited availability of model systems to analyze the effects of HCMV infection on neural cells. Congenital cytomegalovirus (CMV) infection is a major cause of birth defects resulting mainly from primary CMV infection during pregnancy. Approximately 5 to 10% of congenitally infected newborns are estimated to be symptomatic exhibiting multi-organ disorders including neurological defects such as mental retardation, sensorineural hearing loss, and microencephaly [1,2]. A recent study has shown that neural progenitor cells isolated from developing human brain tissues are susceptible to CMV infection and undergo apoptosis following infection [8,9]. The amount of neural cells obtainable from human brain tissues is limited
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