Department of Orthopedics, University of Minnesota, Minneapolis, Minnesota, USA.
Departments of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
J Biol Chem. 2020 Dec 18;295(51):17713-17723. doi: 10.1074/jbc.RA120.013573.
Hdac3 is a lysine deacetylase that removes acetyl groups from histones and additional proteins. Although Hdac3 functions within mesenchymal lineage skeletal cells are defined, little is known about Hdac3 activities in bone-resorbing osteoclasts. In this study we conditionally deleted Hdac3 within Ctsk-expressing cells and examined the effects on bone modeling and osteoclast differentiation in mice. Hdac3 deficiency reduced femur and tibia periosteal circumference and increased cortical periosteal osteoclast number. Trabecular bone was likewise reduced and was accompanied by increased osteoclast number per trabecular bone surface. We previously showed that Hdac3 deacetylates the p65 subunit of the NF-κB transcriptional complex to decrease DNA-binding and transcriptional activity. Hdac3-deficient osteoclasts demonstrate increased K310 NF-κB acetylation and NF-κB transcriptional activity. Hdac3-deficient osteoclast lineage cells were hyper-responsive to RANKL and showed elevated ex vivo osteoclast number and size and enhanced bone resorption in pit formation assays. Osteoclast-directed Hdac3 deficiency decreased cortical and trabecular bone mass parameters, suggesting that Hdac3 regulates coupling of bone resorption and bone formation. We surveyed a panel of osteoclast-derived coupling factors and found that Hdac3 suppression diminished sphingosine-1-phosphate production. Osteoclast-derived sphingosine-1-phosphate acts in paracrine to promote bone mineralization. Mineralization of WT bone marrow stromal cells cultured with conditioned medium from Hdac3-deficient osteoclasts was markedly reduced. Expression of alkaline phosphatase, type 1a1 collagen, and osteocalcin was also suppressed, but no change in Runx2 expression was observed. Our results demonstrate that Hdac3 controls bone modeling by suppressing osteoclast lineage cell responsiveness to RANKL and coupling to bone formation.
Hdac3 是一种赖氨酸去乙酰化酶，可从组蛋白和其他蛋白质上去除乙酰基。尽管 Hdac3 在间充质谱系骨骼细胞中的功能已得到明确界定，但对于其在破骨细胞中的活性知之甚少。在这项研究中，我们在 Ctsk 表达细胞中条件性缺失 Hdac3，并在小鼠中研究其对骨建模和破骨细胞分化的影响。Hdac3 缺失减少了股骨和胫骨的骨膜周长，并增加了皮质骨膜破骨细胞的数量。小梁骨也相应减少，同时伴随每个小梁骨表面破骨细胞数量的增加。我们之前表明，Hdac3 去乙酰化 NF-κB 转录复合物的 p65 亚基，以减少 DNA 结合和转录活性。Hdac3 缺陷型破骨细胞表现出 K310 NF-κB 乙酰化和 NF-κB 转录活性增加。Hdac3 缺陷型破骨细胞谱系细胞对 RANKL 反应过度，并表现出体外破骨细胞数量和大小增加，以及在陷窝形成测定中增强的骨吸收。破骨细胞定向的 Hdac3 缺失减少了皮质骨和小梁骨量参数，表明 Hdac3 调节骨吸收和骨形成的偶联。我们调查了一组破骨细胞衍生的偶联因子，发现 Hdac3 抑制降低了 1-磷酸鞘氨醇的产生。破骨细胞衍生的 1-磷酸鞘氨醇以旁分泌方式起作用，促进骨矿化。用 Hdac3 缺陷型破骨细胞条件培养基培养的 WT 骨髓基质细胞的矿化明显减少。碱性磷酸酶、1a1 型胶原和骨钙素的表达也受到抑制，但未观察到 Runx2 表达的变化。我们的结果表明，Hdac3 通过抑制破骨细胞谱系细胞对 RANKL 的反应性并与骨形成偶联来控制骨建模。
