ABSTRACT
Hypoxia is beneficial for the differentiation of stem cells transplanted for myocardial injury, but mechanisms underlying this benefit remain unsolved. Here, we report the impact of hypoxia-induced Jagged1 expression in cardiomyocytes (CMs) for driving the differentiation of cardiac stem cells (CSCs). Forced hypoxia-inducible factor 1 (HIF-1) expression and physical hypoxia (5% O) treatment could induce Jagged1 expression in neonatal rat CMs. Pharmacological inhibition of HIF-1 by YC-1 attenuated hypoxia-promoted Jagged1 expression in CMs. An ERK inhibitor (PD98059), but not inhibitors of JNK (SP600125), Notch (DAPT), NF-B (PTDC), JAK (AG490), or STAT3 (Stattic) suppressed hypoxia-induced Jagged1 protein expression in CMs. c-Kit CSCs isolated from neonatal rat hearts using a magnetic-activated cell sorting method expressed GATA4, SM22 or vWF, but not Nkx2.5 and cTnI. Moreover, 87.3% of freshly isolated CSCs displayed Notch1 receptor expression. Direct co-culture of CMs with BrdU-labeled CSCs enhanced CSCs differentiation, as evidenced by an increased number of BrdU/Nkx2.5 cells, while intermittent hypoxia for 21 days promoted co-culture-triggered differentiation of CSCs into CM-like cells. Notably, YC-1 and DAPT attenuated hypoxia-induced differentiation. Our results suggest that hypoxia induces Jagged1 expression in CMs primarily through ERK signaling, and facilitates early cardiac lineage differentiation of CSCs in CM/CSC co-cultures HIF-1/Jagged1/Notch signaling.
ABSTRACT
AIM: To explore the expression and significance of receptor tyrosine kinase anexelekto (Axl) in nasopharyngeal carcinoma (NPC).METHODS: Immunohistochemistry was used to detect the Axl protein expression of 78 patients with NPC and 32 patients with nasopharyngeal chronic inflammation (NPI).The correlations between the Axl protein levels and the clinical parameters of NPC patients were analyzed.NPC cells were cultured in vitro, and the expression of Axl in well differentiated CNE1 cells, poorly-differentiated CNE2Z cells and undifferentiated C666-1 cells was detected by immunofluorescence staining.After treatment of the CNE1and C666-1 cells with Axl specific inhibitor TP-0903, CCK-8 assay was used to detect cell viability, flow cytometry was adopted to analyze the cell cycle distribution, qPCR was used to examine the mRNA levels of Axl and proliferating cell nuclear antigen (PCNA), and Western blot was used to examine the protein expression of Axl and p-Axl.RESULTS: Axl protein was localized in the cell membrane and cytoplasm.The rate of high expression of Axl in NPC was significantly higher than that in NPI (P<0.01).High Axl expression showed no correlations with NPC patients'' age, gender and M stage, while positively correlated with the clinical stage, T stage and N stage (P<0.05).Axl protein showed a low level in the CNE1 cells, but showed a high level in CNE2Z and C666-1 cells.TP-0903 inhibited cell viability in concentration and time dependent manners.TP-0903 at 2 nmol/L showed significant inhibitory effects, as evidenced by arresting the cell cycle at G0 phase and reducing Axl activity and PCNA expression.CONCLUSION: High expression of Axl promotes the clinical progress of NPC.TP-0903 significantly inhibits the viability of NPC cells, suggesting that Axl may be a valuable target in the NPC treatment.