Histone Deacetylase Inhibition with Valproic Acid Downregulates Osteocalcin Gene Expression in Human Dental Pulp Stem Cells and Osteoblasts: Evidence for HDAC2 Involvement

Abstract

Adult mesenchymal stem cells, such as dental pulp stem cells, are of great interest for cell-based tissue engineering strategies because they can differentiate into a variety of tissue-specific cells, above all, into osteoblasts. In recent years, epigenetic studies on stem cells have indicated that specific histone alterations and modifying enzymes play essential roles in cell differentiation. However, although several studies have reported that valproic acid (VPA)—a selective inhibitor of histone deacetylases (HDAC)—enhances osteoblast differentiation, data on osteocalcin expression—a late-stage marker of differentiation—are limited. We therefore decided to study the effect of VPA on dental pulp stem cell differentiation. A low concentration of VPA did not reduce cell viability, proliferation, or cell cycle profile. However, it was sufficient to significantly enhance matrix mineralization by increasing osteopontin and bone sialoprotein expression. In contrast, osteocalcin levels were decreased, an effect induced at the transcriptional level, and were strongly correlated with inhibition of HDAC2. In fact, HDAC2 silencing with shRNA produced a similar effect to that of VPA treatment on the expression of osteoblast-related markers. We conclude that VPA does not induce terminal differentiation of osteoblasts, but stimulates the generation of less mature cells. Moreover, specific suppression of an individual HDAC by RNA interference could enhance only a single aspect of osteoblast differentiation, and thus produce selective effects.

KDM5A controls bone morphogenic protein 2-induced osteogenic differentiation of bone mesenchymal stem cells during osteoporosis

“…22 The application of epigenetic regulators, such as inhibitors of histone modification enzymes, may be valuable for stem cell-based interventions. 23, 24 Previous studies showed that the degree of H3K9 acetylation and H3K4 trimethylation in MSCs increased, whereas the level of H3K9 trimethylation decreased during osteogenic differentiation, 25 which was in consistent with our results. For example, TSA, an inhibitor of HDAC1, promoted osteogenic differentiation by altering the epigenetic modifications on the Runx2 promoter in a BMP signaling-dependent manner.…”

Decreased extracellular pH inhibits osteogenesis through proton-sensing GPR4-mediated suppression of yes-associated protein

“…The results revealed that the reduction of the proton concentration resulted in prominent increases in the expressions of BGLAP and IBSP (Fig. 1B), which are mainly expressed during late-stage osteogenic differentiation and mineralization2021; this latter phenomenon was also proved by the data in our study (Fig. S1).…”

Comparison of osteo/odontogenic differentiation of human adult dental pulp stem cells and stem cells from apical papilla in the presence of platelet lysate

“…The expression of these markers (osteocalcin OCN, bone sialoprotein BSP, and dentin sialophosphoprotein DSPP) (Morsczeck et al, 2009;Batouli et al, 2003;Yang et al, 2012;Laino et al, 2011;Chen et al, 2012), is an evidence for the osteogenic/dentinogenic differentiation of DPSCs and SCAP. It has been reported recently that certain inhibitors could enhance the expression levels for osteoblast differentiation (OPN and BSP) in DPSC (Paino et al, 2014) selectively.…”