Effects of histone deacetylase inhibitors on epigenetic modification in human bone marrow mesenchymal stem cells

Abstract

Somatic stem cells can provide properly differentiated cells to restore the function of tissues in the human body damaged by several factors, including reactive oxygen species (ROS) production and inflammation. As unhealthy or older people often fail to replace their damaged cells due to functional weakness at their stem cells, stem cell therapies are an attractive option. The usage of unhealthy stem cells could give a weak therapeutic efficacy in patients; therefore, autologous stem cells need to be improved prior to applications in cell therapy. Recent studies have shown that inhibition of histone deacetylase (HDACs) have been applied in the induction of stem cell differentiation and treatment for disease. These suggest HDAC inhibitors may be good candidates for the improvement of stem cell capacities. In this study, first, I investigated the effects of a HDAC inhibitor, valproic acid (VPA), for the neuronal differentiation of human bone marrow-mesenchymal stromal cells (PART I). VPA-treated MSCs had significant increases in their expression of the neuro-progenitor marker Nestin, Musashi, CD133, and GFAP, as measured by real-time PCR and immunoblot analysis. When VPA-pretreated MSCs were differentiated with neuronal induction media (VPA-dMSCs), they exhibited a cell body and dendritic morphology similar to neurons. The number and neurite length of these VPA-dMSCs significantly increased compared to differentiated MSCs (dMSCs). The VPA-dMSCs and dMSCs had significantly increased transcripts of neuronal-specific marker genes, including Nestin, Musashi, CD133, GFAP, NeuN, MAP-2, NF-M, KCNH1, KCNH5. The cells also showed a higher expression of the neuronal marker proteins Nestin and NF-M from immunocytochemical staining and immunoblot analysis. This study has shown that VPA pretreatment of hBM-MSCs, following their incubation with neuronal induction media, effectively stimulates neuronal cell differentiation to BM-MSCs. Next, I investigated whether ROS are reduced by the HDAC inhibitor, trichostatin A (TSA) in human bone marrow mesenchymal stem cells (PART II). I examined the effects of TSA on ROS in hBM-MSCs through MTT assay and ROS detection. The intracellular ROS were significantly increased in hydrogen peroxide (H2O2) treated MSCs and sodium arsenite (SA) treated MSCs. When hBM-MSCs were incubated with TSA (0 ~ 5000 nM) for 8 hours, cell viability and ROS levels were not changed. The ROS induced by oxidative stress were reduced in TSA pretreated hBM-MSCs (TSA-MSCs) compared to non-treated hBM-MSCs (Stress-MSCs). In conclusion, the TSA reduced ROS in hBM-MSCs, which may protect cells from oxidative stress. The present my studies suggest that HDAC inhibitors, TSA and VPA, effectively improves capacity of differentiation and protection. The combination of HDAC inhibitors and MSCs may improve the efficacy in the cell therapy.