Abstract: BACKGROUND: There are many kinds of cell media with different components, which have a great influence on cell growth. Several studies in and outside China have used serum-free media containing fetal bovine serum for in vitro amplification culture, but the use of media containing human peripheral blood serum to directionally induce human umbilical cord mesenchymal stem cells to neural stem cells and human peripheral blood serum to promote neural stem cells to differentiate into other nerve cells, so far there are few relevant studies. 
OBJECTIVE: To observe the feasibility of inducing human umbilical cord mesenchymal stem cells cultured with human peripheral blood serum into neural stem cells. 
METHODS: (1) Human umbilical cord mesenchymal stem cells were cultured in DMEM/F-12 culture medium containing 10% human peripheral blood serum by volume fraction. Flow cytometry analysis was performed at the third passage to identify surface markers and alizarin red staining was used to detect osteogenic differentiation function. (2) The third-generation human umbilical cord mesenchymal stem cells were induced into neural stem cells using DMEM/F-12 medium containing 0.5% N2, 1.5% B27, 20 ng/mL basic fibroblast growth factor, and 20 ng/mL epidermal growth factor, and their surface markers were identified. (3) Well-growing human umbilical cord mesenchymal stem cell-derived neural stem cells were taken to prepare a single cell suspension. They were evenly inoculated into 96-well plates and incubated with DMEM/F-12 culture medium containing 10% human peripheral blood serum for 8 days. Then, hematoxylin-eosin staining, microtubule-associated protein 2, and glial fibrillary acidic protein immunofluorescence staining were performed to detect the differentiation of neural stem cells into other neural cells.  
RESULTS AND CONCLUSION: (1) Human umbilical cord mesenchymal stem cells cultured with human peripheral blood serum grew in a spiral-like pattern and were distributed in multiple layers, with directional arrangement. The surface of human umbilical cord mesenchymal stem cells highly expressed CD44, CD105, CD29, and CD73. Cells stained with alizarin red showed a color reaction. (2) Human umbilical cord mesenchymal stem cells cultured with human peripheral blood serum could be induced to differentiate into neural stem cells, and the surface of neural stem cells was highly expressed with CD44, CD105, CD29, CD73, Nestin, NF-L, and GALC. (3) On day 8 of induced differentiation of neural stem cells, after staining with hematoxylin and eosin, it was found that the protruding protrusions were longer, with more branches and adjacent cells connected, presenting typical neural cell morphology. Immunofluorescence staining for microtubule-associated protein 2 and glial fibrillary acidic protein was positive. It is concluded that human umbilical cord mesenchymal stem cells cultured by human peripheral blood serum can be directly induced to differentiate into neural stem cells. Under the action of human peripheral blood serum, neural stem cells can differentiate into other neural cells as the culture time prolongs. 

Key words: human peripheral blood serum, human umbilical cord mesenchymal stem cell, neural stem cell, neural cell, differentiation