Inhibition of miR338 rescues cleidocranial dysplasia in Runx2 mutant mice partially via the Hif1a-Vegfa axis.

ABSTRACT

Haploinsufficiency of Runt-related transcription factor-2 (RUNX2) is responsible for cleidocranial dysplasia (CCD), a rare hereditary disease with a range of defects, including delayed closure of the cranial sutures and short stature. Symptom-based treatments, such as a combined surgical-orthodontic approach, are commonly used to treat CCD patients. However, there have been few reports of treatments based on Runx2-specific regulation targeting dwarfism symptoms. Previously, we found that the miR338 cluster, a potential diagnostic and therapeutic target for postmenopausal osteoporosis, could directly target Runx2 during osteoblast differentiation in vitro. Here, we generated miR338-/-;Runx2+/- mice to investigate whether inhibition of miR338 could rescue CCD defects caused by Runx2 mutation in vivo. We found that the dwarfism phenotype caused by Runx2 haploinsufficiency was recovered in miR338-/-;Runx2+/- mice, with complete bone density restoration and quicker closure of fontanels. Single-cell RNA-seq analysis revealed that knockout of miR338 specifically rescued the osteoblast lineage priming ability of bone marrow stromal cells in Runx2+/- femurs, which was further confirmed by Osterix-specific conditional knockout of miR338 in Runx2+/- mice (OsxCre; miR338 fl/fl;Runx2+/-). Mechanistically, ablation of the miR338 cluster in Runx2+/- femurs directly rescued the Hif1a-Vegfa pathway in Runx2+/- osteoblasts, as proven by gene expression profiles and ChIP and Re-ChIP assays. Collectively, our data revealed the genetic interaction between Runx2 and the miR338 cluster during osteoblast differentiation and implied that the miR338 cluster could be a potential therapeutic target for CCD.