Objective： To investigate the effects and underlying molecular mechanisms of icariin （ICA） on self-renewal and differentiation of neural stem cells （NSCs）. Methods： NSCs were derived from forebrains of mice embryos by mechanical dissociation into single cell suspension. The self-renewal of NSCs was measured by neurosphere formation assay. The proliferation of NSCs was detected by water-soluble tetrazolium （WST） and 5-ethynyl-2＇-deoxyuridine （EdU） incorporation assay. Protein expression of neuron-specific marker tubulin-βⅢ（TuJ1） and astrocyte-specific marker glial fibrillary acidic protein （GFAP） were measured by immunofluorescence and Western blotting. Using microarray, the differentially expressed genes （DEGs） were screened between NSCs with or without ICA treatment. The signaling pathways enriched by these DEGs and their role in mediating effects of ICA were analyzed. Results： ICA significantly promoted neurosphere formation of NSCs cultured in growth protocol in a dose-dependent manner and achieved the maximum effects at 100 nmol/L. ICA also increased optical absorbance value and EdU incorporation into nuclei of NSCs. ICA had no significant effects on the percentage of TuJ1 or GFAP-positive cells, and TuJ1 or GFAP protein expression in NSCs cultured in differentiation protocol. A total of 478 genes were found to be differentially regulated. Among signaling pathways significantly enriched by DEGs, mitogen activated protein kinase （MAPK） pathway was of interest. Blockade of extracellular signal-regulated kinase （ERK）/MAPK, other than p38/MAPK subfamily pathway partially abolished effects of ICA on neurosphere formation and EdU incorporation of NSCs. Conclusion： ICA can promote the self- renewal of NSCs at least partially through ERK/MAPK signaling pathway.
As the epitome of the modern regenerative medicine, stem cells were proposed in the basic sense no more than 200 years ago. However, the concept of "stem cells" existed long before the modern medical description. The hypothesis that all things, including our sentient body, were generated from a small origin was shared between Western and Chinese people. The ancient Chinese philosophers considered Jing(also known as essence) as the origin of life. In Chinese medicine(CM), Jing is mainly stored in Kidney(Shen) and the so-called Shen-Jing(Kidney essence). Here, we propose that Shen-Jing is the CM term used to express the meaning of "origin and regeneration". This theoretical discovery has at least two applications. First, the actions underlying causing Shen-Jing deficiency, such as excess sexual intercourse, chronic diseases, and aging, might damage the function of stem cells. Second, a large number of Chinese herbs with Shen-Jing-nourishing efficacy had been proven to affect stem cell proliferation and differentiation. Therefore, if Shen-Jing in CM is equivalent with stem cells in regenerative medicine, higher effective modulators for regulating stem-cell behaviors from Kidney-tonifying herbs would be expected.
