The effect of epigenetic reprogramming using MI192 HDAC inhibitor on enhancing the osteogenesis of human adipose-derived stem cells in vitro.

The ability to control stem cell function is the key to stem cell-based therapy and living tissue regeneration. In natural conditions, histone deacetylases (HDAC) are regarded as the important defining epigenetic reprogramming for stem cell differentiation. To date, human adipose-derived stem cells (hADSCs) have been widely utilised for bone tissue engineering applications. The present study aimed to examine the effect of a novel HDAC2&3-selective inhibitor, MI192, on hADSCs epigenetic reprogramming for regulating its osteogenic potential in vitro. The results confirmed that MI192 treatment reduced the hADSCs viability in a time and dose-dependent manner. The optimal concentration and pre-treatment time of MI192 for hADSCs osteogenic induction was 30 µM and 2 days representatively. A quantitative biochemical assay confirmed that the pre-treatment with MI192 (30 µM) for 2 days significantly enhanced hADSCs alkaline phosphatase (ALP) specific activity (P<0.05) compared with that of the valproic acid (VPA) pre-treatment group. Real-time PCR analysis revealed that MI192 pre-treatment up-regulated hADSCs gene expressions of osteogenic markers (e.g., Runx2, Col1, and OCN) under the osteogenic induction. DNA flow cytometric analysis indicated that two days' pre-treatment with MI192 (30 µM) resulted in G2/M arrest in hADSCs and this G2/M arrest was reversible. Our results suggest that MI192 is capable of epigenetic reprogramming of hADSCs via HDAC inhibition for controlling the cell cycle, resulting in enhancing hADSCs osteogenic differentiation, which indicates the potential of using MI192 for promoting bone tissue regeneration.

Induction of differentiation and apoptosis in leukaemic cell lines by the novel benzamide family histone deacetylase 2 and 3 inhibitor MI-192.

Histone deacetylase inhibitors (HDACIs) are in advanced clinical development as cancer therapeutic agents. However, first generation HDACIs such as butyrate and valproate are simple short chain aliphatic compounds with moieties resembling acetyl groups, and have a broad spectrum of activity against HDACs. More complex second generation HDACIs undergoing clinical trials, such as the benzamide group compounds MS-275 and MGCD0103, are specific primarily for HDAC1 and HDAC2. To expand the repertoire of available HDACIs and HDAC specificities we created a novel benzamide-based compound named MI-192. When tested against purified recombinant HDACs, MI-192 had marked selectivity for the class I enzymes, HDAC2 and HDAC3. Screening in the NCI60 screen demonstrated that MI-192 had greatly enhanced efficacy against cells of leukaemic origin. When tested in culture against the acute myeloid leukaemic cell lines U937, HL60 and Kasumi-1, MI-192 induced differentiation and was cytotoxic through promotion of apoptosis. MI-192 therefore justifies further investigation and development as a potential therapeutic agent for use in leukaemia.

Histone deacetylases are dysregulated in rheumatoid arthritis and a novel histone deacetylase 3-selective inhibitor reduces interleukin-6 production by peripheral blood mononuclear cells from rheumatoid arthritis patients.

OBJECTIVE: To characterize the role of histone deacetylase (HDAC) activity in rheumatoid arthritis (RA) and to evaluate the effects of MI192, a novel HDAC-3-selective inhibitor, compared with the established nonselective HDAC inhibitor trichostatin A (TSA), on proinflammatory cytokine production. METHODS: Activity of HDAC and histone acetyltransferase was measured in peripheral blood mononuclear cells (PBMCs) from RA patients by spectrophotometric assay, prior to and after 12 weeks of etanercept therapy. The effects of HDAC inhibitor treatment on cytokine production in both RA and healthy PBMCs were assessed by enzyme-linked immunosorbent assay. RESULTS: RA PBMCs exhibited significantly increased HDAC activity (P = 0.007) compared to PBMCs from healthy individuals, and the increase was unaltered after 12 weeks of etanercept therapy. TSA was a potent inhibitor of tumor necrosis factor (TNF) and interleukin-6 (IL-6) production in both RA and healthy PBMCs and of interferon-γ (IFNγ) production in healthy PBMCs; IFNγ was not produced by RA PBMCs. MI192 inhibited TNF production at high concentrations and dose-dependently inhibited IL-6 in RA PBMCs but not healthy PBMCs, across a dose range of 10 µM-5 nM. CONCLUSION: HDAC activity is dysregulated in RA PBMCs and is a potential target for therapeutic intervention, as it is not affected by conventional anti-TNF treatment with etanercept. Both the selective and the nonselective HDAC inhibitors (MI192 and TSA, respectively) were found to regulate cytokine production from PBMCs, but their effects were cell type and compound specific. HDAC inhibitors have potential in the treatment of RA, and HDAC-selective inhibition may improve the therapeutic margin of safety; however, further clinical characterization and evaluation for adverse effects is needed.