Histone deacetylase inhibitors promote osteoblast maturation.
HDIs are potential therapeutic agents for cancer and neurological diseases because of their abilities to alter gene expression, induce growth arrest or apoptosis of tumors cells, and stimulate differentiation. In this report, we show that several HDIs promote osteoblast maturation in vitro and in calvarial organ cultures.


BACKGROUND
Histone deacetylase inhibitors (HDIs) are currently in phase I and II clinical trials as anticancer agents. Some HDIs are also commonly prescribed treatments for epilepsy and bipolar disorders. Although administered systemically, the effects of HDIs on osteoblasts and bone formation have not been extensively examined. In this study, we investigated the effect of histone deacetylase inhibition on osteoblast proliferation and differentiation.


METHODS
MC3T3-E1 cells, calvarial-derived primary osteoblasts, and calvarial organ cultures were treated with various commercially available HDIs (trichostatin A [TSA], sodium butyrate [NaB], valproic acid [VPA], or MS-275). The effects of these inhibitors on cell proliferation, viability, cell cycle progression, Runx2 transcriptional activity, alkaline phosphatase production, and matrix mineralization were determined. Expression levels of osteoblast maturation genes, type I collagen, osteopontin, bone sialoprotein, and osteocalcin in response to TSA were measured by quantitative PCR.


RESULTS
Concentrations of HDIs that caused hyperacetylation of histone H3 induced transient increases in osteoblast proliferation and viability but did not alter cell cycle profiles. These concentrations of HDIs also increased the transcriptional activity of Runx2. TSA accelerated alkaline phosphatase production in MC3T3-E1 cells and calvarial organ cultures. In addition, TSA accelerated matrix mineralization and the expression of osteoblast genes, type I collagen, osteopontin, bone sialoprotein, and osteocalcin in MC3T3-E1 cells.


CONCLUSIONS
These studies show that histone deacetylase activity regulates osteoblast differentiation and bone formation at least in part by enhancing Runx2-dependent transcriptional activation. Therefore, HDIs are a potentially new class of bone anabolic agents that may be useful in the treatment of diseases that are associated with bone loss such as osteoporosis and cancer.
Schroeder
Tania M
TM
Graduate Program in Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, USA.
Westendorf
Jennifer J
JJ
D000107:Acetylation / Q000187:drug effects; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D020148:Butyric Acid / Q000494:pharmacology; D002113:Calcification, Physiologic / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D058574:Integrin-Binding Sialoprotein; D051379:Mice; D009924:Organ Culture Techniques; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics; D053495:Osteopontin; D011725:Pyridines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012795:Sialoglycoproteins / Q000235:genetics; D012886:Skull / Q000187:drug effects / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology
D001549:Benzamides; D024042:Collagen Type I; D050659:Core Binding Factor Alpha 1 Subunit; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; C546872:Ibsp protein, mouse; D058574:Integrin-Binding Sialoprotein; D011725:Pyridines; C493716:Runx2 protein, mouse; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D015675:Osteocalcin; D053495:Osteopontin; D020148:Butyric Acid; C118739:entinostat; C012589:trichostatin A; D014635:Valproic Acid; D000469:Alkaline Phosphatase; D006655:Histone Deacetylases; D002118:Calcium