Epiregulin can promote proliferation of stem cells from the dental apical papilla via MEK/Erk and JNK signalling pathways

OBJECTIVES

Mesenchymal stem cells (MSCs) are a reliable resource for tissue regeneration, but their molecular mechanisms of differentiation and proliferation remain unclear; this situation has restricted use of MSCs to a limited number of applications. A previous study of ours found a member of the epidermal growth factor family, epiregulin (EREG), to be involved in regulation of MSC differentiation. In the present study, we have used human dental stem cells from the apical papilla (SCAPs) to investigate the role of EREG on proliferation of MSCs.

MATERIALS AND METHODS

SCAPs were isolated from apical papillae of immature third molars. Retroviral short hairpin RNA (shRNA) was used to silence EREG gene expression, and human recombinant EREG protein was used to stimulate SCAPs. SCAP proliferation was examined using tetrazolium dye colorimetric assay/cell growth curve. Western blotting was performed to detect expressions of extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), mitogen-activated protein kinases 1 and 2 (MEK1/2), protein kinase B (Akt), p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK).

RESULTS

Depletion of EREG with shRNA inhibited SCAP proliferation and repressed phosphorylation of Erk1/2 and JNK. Human recombinant EREG protein promoted cell proliferation and enhanced Erk1/2, MEK and JNK phosphorylation in SCAPs. Furthermore, blocking MEK/Erk signalling with specific Erk1/2 inhibitor PD98059, or JNK signalling with specific inhibitor SP600125, abolished effects of EREG on cell proliferation.

CONCLUSION

These findings indicate that EREG could enhance cell proliferation in dental tissue-derived MSCs by activating MEK/Erk and JNK signalling pathways.

Level set based auto segmentation of the tagged left ventricle MR images

To facilitate automatic segmentation, we adopt SVM (Support Vector Machine) to localize the left ventricle, and the segmentation is then carried out with narrow band level set. The method of generating the narrow band is improved such that the time used is reduced. Based on the imaging characteristics of the tagged left ventricle MR images, BPV (block-pixel variation) and intensity comparability are introduced to improve the speed term of level set and to increase the precision of segmentation. Our method can perform the segmentation of the tagged left ventricle MR images accurately and automatically.

Destruction of parotid glands affects nitrate and nitrite metabolism

The role of salivary glands in nitrate and nitrite metabolism is poorly understood. The aim of the present study was to investigate the effect of parotid gland ablation on dynamic metabolism of nitrate and nitrite in miniature pigs. The parotid glands of 5 healthy miniature pigs were bilaterally ablated by methyl violet. Concentrations of nitrate and nitrite of whole saliva, serum, and urine samples were analyzed by high-performance liquid chromatography. Results showed that bilateral ablation of the parotid glands led to a significant decrease of nitrate secretion from blood to saliva (P < 0.05) and thus low nitrite levels. Dysfunction of the parotid glands temporarily increased the systemic level of nitrate in miniature pigs after nitrate loading. This study suggests that the parotid glands play an important role in the balance of nitrate and nitrite levels in both whole saliva and the body.

[Analysis of dynamic blood pressure of essential hypertension patients with Ganyang shangkangzheng or Gan-shengyinxuzheng]

Inspecting twenty-four hours dynamic blood pressure of sixty-two essential hypertension patients with Ganyang shangkangzheng or Gan-shengyinxuzheng in normal conditions and analysing blood pressure's dynamic regularity of the two groups with different traditional Chinese medicine Zheng type, we found that the blood pressure of Ganyang shangkangzheng patients was higher in the daytime than that at night, and the Gan-Shengyinxuzheng patients had the reverse results. The results suggest that the dynamic blood pressure value may be an objective index for differential diagnosis of traditional Chinese medicine Zheng types of patients with essential hypertension.