Nerve growth factor induces cord formation of mesenchymal stem cell by promoting proliferation and activating the PI3K/Akt signaling pathway

Aim： To investigate whether nerve growth factor （NGF） induced angiogenesis of bone marrow mesenchymal stem cells （MSCs） and the underlying mechanisms. Methods： Bone marrow MSCs were isolated from femors or tibias of Sprague-Dawley rat, and cultured. The cells were purified after 3 to 5 passages, seeded on Matrigel-coated 24-well plates and treated with NGF. Tube formation was observed 24 h later. Tropomyosin- related kinase A （TrkA） and p75NTR gene expression was examined using PCR analysis and flow cytometry. Growth curves were deter- mined via cell counting. Expression of VEGF and pAkt/Akt were analyzed with Western blot. Results： NGF （25, 50, 100 and 200 pg/L） promoted tube formation of MSCs. The tubular length reached the maximum of a 2.24-fold increase, when the cells were treated with NGF （50 pg/L）. NGF （50 pg/L） significantly enhanced Akt phosphoryiation. Pretreatment with the specific PI3K inhibitor LY294002 （10 pmol/L） blocked NGF-stimulated Akt phosphorylation, tube formation and angiogenesis. NGF （25-200 pg/L） did not affect the expression of TrkA and vascular endothelial growth factor （VEGF）, but significantly suppressed the expression of p75NTR. NGF （50 pg/L） markedly increased the proliferation of MSCs. Conclusion： NGF promoted proliferation of MSCs and activated the PI3K/Akt signaling pathway, which may be responsible for NGF induction of MSC angiogenesis.