Modulation of the resorption and osteoconductivity of alpha-calcium sulfate by histone deacetylase inhibitors.

Calcium sulfate (CS) is an osteoconductive material with a long history of clinical use. However, its resorptive properties are not optimal for bone regeneration. Recently, histone deacetylase inhibitors (HDIs) have been suggested as bone regeneration tools. In this study, we investigated the effects of the HDIs sodium butyrate and trichostatin A on alpha-form CS (alphaCS) performance. MC3T3-E1 pre-osteoblasts cultured on alphaCS containing either HDI (alphaCS/HDI) showed higher levels of alkaline phosphatase activity than those cultured on alphaCS alone. The expression of genes characteristic of the osteoblast phenotype, including Runx2, osteocalcin, and bone sialoprotein, was strongly promoted by alphaCS/HDI. When cultured on alphaCS/HDIs, the osteoclastic differentiation of RAW264.7 monocytes was substantially suppressed, as measured by tartrate-resistant acid phosphatase (TRAP) activity and the expression levels of calcitonin receptor and TRAP. Neither HDI affected the CS setting time, compressive strength, or dissolution in a simulated body fluid. In a rat calvarial model of critical size bone defects, alphaCS/HDIs enhanced osteoblast differentiation, led to new bone formation, and delayed resorption, as confirmed by micro-computed tomography and histological analyses.

Enhanced ex vivo expansion of human adipose tissue-derived mesenchymal stromal cells by fibroblast growth factor-2 and dexamethasone.

In the present study, we investigated the ex vivo expansion of human adipose tissue-derived mesenchymal stromal cells (ATSCs) to identify factors that promoted efficient expansion while preserving stem cell potential. We examined several growth factors and steroids, and found that the combination of a low concentration of fibroblast growth factor-2 (FGF-2) (1 ng/mL) and dexamethasone (DEX) or betamethasone (BET) enhanced the proliferation of ATSCs by approximately 30-60% as compared to control. Enhanced proliferation under these conditions was confirmed using ATSCs isolated from three independent donors. ATSCs that were expanded in the presence of FGF-2 and DEX for 5 days were capable of differentiating into either osteoblastic or adipogenic cells, and the cells were positive for the mesenchymal stem cell markers such as CD29, CD44, CD90, CD105, and CD146, suggesting that the stem cell potential of the ATSCs was preserved. Analysis of signaling pathway revealed that tyrosine phosphorylation of Src kinase was dramatically increased in response to FGF-2 and DEX, suggesting the involvement of Src-dependent pathways in the stimulatory mechanism of proliferation of ATSCs by FGF-2 and DEX. Moreover, Src family kinase inhibitors (SU6656 and Src kinase inhibitor I) substantially reduced the FGF-2 and DEX-induced proliferation of ATSCs. SU6656 also inhibited the osteogenic and adipogenic differentiation of ATSCs. The results of the current study demonstrate that FGF-2 in combination with DEX stimulates the proliferation and osteoblastic and adipogenic differentiation of ATSCs through a Src-dependent mechanism, and that FGF-2 and DEX promote the efficient ex vivo expansion of ATSCs.