Neurotrophins promote bone marrow stromal cells (MSCs) to express neural proteins in vitro
We tested the hypothesis that MSCs cultured in an environment containing neurotrophins promotes the expression of neural proteins. The effect of neurotrophins (brain-derived neurotrophic factor, BDNF; nerve growth factor, NGF) and the detection of corresponding receptors (TrkA-NGF, TrkB-BDNF) on the MSCs were investigated. MSCs were cultured in regular medium, i.e. Iscove s Modified Dulbecco s medium (IMDM) supplemented with 10% fetal bovine serum (FBS), and then isolated by their adherence to the plastic dishes from non-adherent hematopoietic cells at 72 h of incubation. Subsequently, the cells were cultured for 2 weeks under the following conditions: (A) regular medium, (B) regular medium + BDNF (100ng/ml), (C) regular medium + BDNF (100ng/ml) + NGF (100ng/ml ), or (D) regular medium + BDNF (100ng/ml ) + NFG (100ng/ml) + bFGF (10ng/ml). Using immunoflurescence staining, MSCs widely expressed TrkA and TrkB (the receptors of NGF and BDNF) in the medium (A). Medium (B) and (C) induced an increase of total number of cells (116%) derived from MSCs at 12 days, however, this did not reach statistical significance (P>0.05). Medium (D) significantly promoted the proliferation of MSCs (P<0.05), compared with controls (148%). Approximately 1% and 0.5% of MSCs expressed GFAP (an astroglial marker) and NeuN (a neuronal marker), respectively, in the medium (A). GFAP positive cells increased to 4%∼6% and NeuN positive cells increased to 1% in culture maintained in the medium (B) and (C). However, medium (D) exerted a dramatic effect on GFAP positive cells that reached 8% and NeuN positive cells reached 2%. Our data provide evidence that neurotrophins enhance the proliferation and differentiation of MSCs into the neural-like cells that express neural proteins in vitro.