DDIT3 deficiency accelerates bone remodeling during bone healing by enhancing osteoblast and osteoclast differentiation through ULK1-mediated autophagy

• Published in: Bone (New York, N.Y.) Vol. 182; p. 117058
• Main Authors: Jia, Meie, Dong, Zhipeng, Dong, Wei, Yang, Beining, He, Ying, Wang, Yan, Wang, Jiawei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2024
• Subjects: Animals; Autophagy; Bone remodeling; Bone Remodeling - physiology; Bone Resorption - metabolism; Cell Differentiation - physiology; DDIT3; Mice; Osteoblast; Osteoblasts - metabolism; Osteoclast; Osteoclasts - metabolism; Osteoprotegerin - metabolism; RANK Ligand - metabolism; ULK1; Osteoblast; Osteoclast; ULK1; Bone remodeling; Autophagy; DDIT3
• DOI: 10.1016/j.bone.2024.117058
• ISSN: 8756-3282

The coordination of osteoblasts and osteoclasts is essential for bone remodeling. DNA damage inducible script 3 (DDIT3) is an important regulator of bone and participates in cell differentiation, proliferation, autophagy, and apoptosis. However, its role in bone remodeling remains unexplored. Here, we found that Ddit3 knockout (Ddit3-KO) enhanced both bone formation and resorption. The increased new bone formation and woven bone resorption, i.e., enhanced bone remodeling capacity, was found to accelerate bone defect healing in Ddit3-KO mice. In vitro experiments showed that DDIT3 inhibited both osteoblast differentiation and Raw264.7 cell differentiation by regulating autophagy. Cell coculture assay showed that Ddit3-KO decreased the ratio of receptor activator of nuclear factor-κβ ligand (RANKL) to osteoprotegerin (OPG) in osteoblasts, and Ddit3-KO osteoblasts inhibited osteoclast differentiation. Meanwhile, DDIT3 knockdown (DDIT3-sh) increased receptor activator of nuclear factor-κβ (RANK) expression in Raw264.7 cells, and DDIT3-sh Raw264.7 cells promoted osteoblast differentiation, whereas, DDIT3 overexpression had the opposite effect. Mechanistically, DDIT3 promoted autophagy partly by increasing ULK1 phosphorylation at serine555 (pULK1-S555) and decreasing ULK1 phosphorylation at serine757 (pULK1-S757) in osteoblasts, thereby inhibiting osteoblast differentiation. DDIT3 inhibited autophagy partly by decreasing pULK1-S555 in Raw264.7 cells, thereby suppressing osteoclastic differentiation. Taken together, our data indicate that DDIT3 is one of the elements regulating bone remodeling and bone healing, which may become a potential target in bone defect treatment. [Display omitted] •DDIT3 inhibits osteoblast differentiation by enhancing autophagy.•DDIT3 inhibits Raw264.7 cell differentiation by inhibiting autophagy.•DDIT3 differentially regulates autophagy through ULK1 phosphorylation.•DDIT3 regulates osteoblast-osteoclast coupling.•DDIT3 deficiency promotes bone remodeling and bone healing in vivo.