The H19 gene was cloned about 20 years ago and was one of the first imprinted genes to be identified. H19 is exclusively expressed from the maternal chromosome (Ariel et al., 2000). The expression of H19 is high during vertebrate embryo development, but it is downregulated in most tissues shortly after birth with the exception of skeletal tissue and cartilage (Lustig et al., 1994). H19 is a long non-coding RNA (lncRNA) that harbours the microRNA-675 in its transcript. Recently it has been shown that microRNA-675 is involved in regulation of type II collagen expression in human articular chondrocytes and may present a potential new target for cartilage repair (Dudek KA et al. 2010). Yet the role of H19 in osteoblasts and mineralisation is incompletely understood. We show that H19 is progressively expressed (about 30-fold increase, p<0.001) during osteogenic differentiation of human mesenchymal stromal cells (hMSC). Vitamin D stimulated H19 expression 3-fold (P<0.001) in parallel to enhancing mineralisation. Knock-down of H19 RNA by short hairpin RNAs (shRNA) led to 70-95% reduction in alkaline phosphatase mRNA expression and activity and 80-95% inhibition of extracellular matrix mineralisation (P values <0.01 to <0.001). Similar levels of inhibition of the osteoblastic transcription factor RUNX2 and the matrix protein collagen type I expression were observed. H19 expression is paralleled by expression of miR-675 (30-fold increase during differentiation) and knockdown of H19 suppresses miR-675 expression in osteoblasts. However, yet miR-675 inhibition didnt significantly affect mineralisation. In conclusion, our data show for the first time involvement of the long non-coding RNA H19 in osteoblast biology and its role in regulation of bone formation and extracellular matrix mineralisation. Current data suggest a role of the lncRNA H19 besides the miR675.
Disclosure: The authors declared no competing interests. This work was supported by The Netherlands Institute for Regenerative Medicine (NIRM, grant No: FES0908).