Adipose tissue-derived mesenchymal stem cells cultured at high cell density express brain-derived neurotrophic factor and exert neuroprotective effects in a 6-hydroxydopamine rat model of Parkinson’s disease

Mesenchymal stem cells (MSCs) secrete neurotrophic factors, and have been reported to improve functional outcomes in animal models of neurodegenerative diseases such as cerebral ischemia, stroke, spinal cord lesions, and Parkinson’s disease. Previously, we found that adipose tissue-derived mesenchymal stem cells (ASCs) cultured at high cell density (HD-ASCs) expressed interferon-beta (IFN-β). Here we demonstrate that ASCs expressing IFN-β also express brain-derived neurotrophic factor (BDNF). Growth rates of neuroblastoma cells (SK-N-BE(2)C) were increased when co-cultured with HD-ASCs or treated with concentrated medium obtained from HD-ASCs (HD-ASC-CM). The HD-ASC-CM induced AKT phosphorylation in SK-N-BE(2)C cells, and AKT inhibition by Ly294002 reduced cell viability of SK-N-BE(2)C cells. Additionally, a protective effect on SK-N-BE(2)C cells exposed to 6-hydroxydopamine (6-OHDA) was observed in the HD-ASC-CM or brain-derived neurotrophic factor (BDNF) treated cells. The protective effect of the HD-ASC-CM was neutralized by anti-BDNF antibody. In the 6-OHDA-induced Parkinson’s disease rat model, ASCs reduced amphetamine-induced rotations and a greater number of tyrosine hydroxylase (TH)-positive cells were observed in the HD-ASCs-injected group compared with sham controls and the low density cultured ASC-injected group. Moreover, the expression of BDNF, nerve growth factor (NGF), TH, and proliferating cell nuclear antigen (PCNA) in ipsilateral midbrain tissues including substantia nigra pars compacta (SNc) was increased by transplantation of HD-ASCs. These data indicate that HD-ASCs may induce neuroprotective effects through BDNF expression and subsequent increase of proliferation in neuronal cells both in vitro and in vivo.