The Presence of Neural Stem Cells and Changes in Stem Cell-Like Activity With Age in Mouse Spiral Ganglion Cells In Vivo and In Vitro

OBJECTIVES: Spiral ganglion neurons (SGNs) include potential endogenous progenitor populations for the regeneration of the peripheral auditory system. However, whether these populations are present in adult mice is largely unknown. We examined the presence and characteristics of SGN-neural stem cells (NSCs) in mice as a function of age. METHODS: The expression of Nestin and Ki67 was examined in sequentially dissected cochlear modiolar tissues from mice of different ages (from postnatal day to 24 weeks) and the sphere-forming populations from the SGNs were isolated and differentiated into different cell types. RESULTS: There were significant decreases in Nestin and Ki67 double-positive mitotic progenitor cells in vivo with increasing mouse age. The SGNs formed spheres exhibiting self-renewing activity and multipotent capacity, which were seen in NSCs and were capable of differentiating into neuron and glial cell types. The SGN spheres derived from mice at an early age (postnatal day or 2 weeks) contained more mitotic stem cells than those from mice at a late age. CONCLUSION: Our findings showed the presence of self-renewing and proliferative subtypes of SGN-NSCs which might serve as a promising source for the regeneration of auditory neurons even in adult mice.

Bone morphogenetic protein 4 stimulates neuronal differentiation of neuronal stem cells through the ERK pathway

Bone morphogenic protein 4 (BMP4), a member of the TGF-beta superfamily, induced neural differentiation of neural stem cells (NSCs) grown in a medium containing basic fibroblast growth factor (bFGF). The Ras protein level and the activities of the downstream ERKs were increased by transfection of BMP4 or treatment with recombinant BMP4. The effects of BMP4, including activation of the Ras-ERK pathway and induction of the neuron marker beta-tubulin type III (Tuj1), were blocked by co-treatment of the BMP4 antagonist, noggin. The roles of the Ras-ERK pathway in neuronal differentiation by BMP4 were revealed by measuring the effect of the ERK pathway inhibition by dominant negative Ras or PD98059, the MEK specific inhibitor. BMP4 is a transcriptional target of Wnt/beta-catenin signaling, and both the mRNA and protein levels of BMP4 were increased by treatment of valproic acid (VPA), a chemical inhibitor of glycogen synthase kinase 3beta (GSK3beta) activating the Wnt/beta-catenin pathway. The BMP4- mimicking effects of VPA, activation of the Ras-ERK pathway and induction of Tuj1, also were blocked by noggin. These results indicate the potential therapeutic usage of VPA as a replacement for BMP4.

Nitric Oxide Synthase (NOS) Expression in Breast Cancer

PURPOSE: NO, a diatomic free radical, plays a diverse physiological and pathophysiological roles in the vascular, neuronal and immune systems. It is produced by nitric oxide synthase (NOS) which consists of three different isoforms. In this study we investigated NOS expression in 84 human breast carcinomas and its associations to other clinicopathological factors. METHODS: The immunohistochemical staining for NOS expression in 84 human breast carcinomas were performed and their medical records were reviewed retrospectively. RESULTS: iNOS expression in tumor cells was observed in 48.2% and eNOS expression was detected in 51.9%. iNOS expression in tumor cells has positive correlation with eNOS expression in tumor and is associated with iNOS expression in stroma and endothelial cells. Although iNOS expression in tumor cells has negative correlation with tumor size (P=0.047) and lymph node metastasis (P=0.002), it has no effects on 5 year overall and disease free survivals. iNOS expression in stroma also has negative correlation with tumor size (P=0.016) and nuclear grade (P=0.025). No significant correlation between eNOS expression and clinicopathological factors was observed but eNOS expression in tumor cells contributed to worse 5 year overall survivals (92.1% vs 77.0%) in marginal significance (P=0.053). CONCLUSION: These data suggest that iNOS expression in tumor may have an inhibitory effect in tumor growth and lymph node metastasis. These results may be further investigated.