microRNA-31 inhibition partially ameliorates the deficiency of bone marrow stromal cells from cleidocranial dysplasia

Cleidocranial dysplasia (CCD) in humans is an autosomal-dominant skeletal dysplasia caused by heterozygous mutations of the runt-related transcription factor 2 (RUNX2) and significantly increases the risk of osteoporosis. Increasing evidence demonstrates that the dysfunction of bone marrow stromal cells from CCD patients (BMSCs-CCD) contributes to the bone deficiency, but the characteristics of BMSCs-CCD and the mechanisms that underlie their properties remain undefined.

Our results show the functional deficiencies of BMSCs-CCD and a potential role of miR-31 in BMSCs-CCD deficiencies. The application of miR-31 inhibitor in BMSCs-CCD might lend hope for developing BMSC-based therapeutic approaches against CCD-associated skeletal diseases.

The clinical manifestations of three CCD patients were collected and the mutations of RUNX2 were analyzed. The properties of proliferation, osteogenesis, stemness, and senescence of BMSCs-CCD were compared with that of BMSCs from healthy donors. The expression of microRNA-31 ( miR-31) between BMSCs-CCD and BMSCs was measured and lentivirus-carried miR-31 inhibitor was used to determine the role of miR-31 in BMSCs-CCD both in vitro and in vivo. The molecular mechanisms underlying RUNX2-miR31 and miR-31 targeting stemness and senescence of BMSCs-CCD were also explored.

We identified two mutation sites of RUNX2 via exome sequencing from 2 of 3 Chinese CCD patients with typical clinical presentations. Compared with BMSCs from healthy donors, BMSCs-CCD displayed significantly attenuated proliferation, osteogenesis and stemness, and enhanced senescence. Meanwhile, miR-31 knockdown could ameliorate these deficiency phenotypes of BMSCs-CCD by regulating SATB2, BMI1, CDKN, and SP7. Mechanistically, RUNX2 directly repressed miR-31 expression, and therefore RUNX2 haploinsufficiency in CCD leading to miR-31 upregulation contributed to the deficiency of BMSCs-CCD. miR-31 inhibition in BMSCs-CCD showed enhanced osteogenesis through heterotopic subcutaneous implantation in the nude mice. Conclusions: Our results show the functional deficiencies of BMSCs-CCD and a potential role of miR-31 in BMSCs-CCD deficiencies. The application of miR-31 inhibitor in BMSCs-CCD might lend hope for developing BMSC-based therapeutic approaches against CCD-associated skeletal diseases.