lncRNA HHIP-AS1/HHIP modulates osteogenic differentiation of BM-MSCs by regulating Hedgehog signaling pathway

Abstract

Background: lncRNA, a type of non-coding RNA, plays an important role in the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs). In this study, lncRNA and mRNA microarrays were performed to study the change of gene expression during osteogenic differentiation of BM-MSCs. We focused on Hedgehog interacting protein (HHIP), because HHIP mRNA and lncRNA HHIP-AS1 were gradually down-regulated on days 0, 7, and 14 during osteogenic differentiation. In addition, the gene coding lncRNA HHIP-AS1 is located on the anti-sense of Hhip gene, implying the potential interaction between lncRNA HHIP-AS1 and HHIP mRNA. Methods: BM-MSCs with over-expressed or silenced lncRNA HHIP-AS1 were constructed to explore the biological role of HHIP-AS1 in osteogenic differentiation. BM-MSCs were lysed to determine the alkaline phosphatase activity. Fluorescence in situ hybridization and immunofluorescence were performed to analyze HHIP-AS1, HHIP, RUNX2 and osteocalcin. Results: Overexpression of lncRNA HHIP-AS1 increased HHIP expression, which suppressed Hedgehog signaling pathway, as indicated by the reduction of SMO, Gli1 and Gli2. The suppression of Hedgehog signal was associated with the inhibited osteogenesis. HHIP knockdown abolished the suppression of osteogenesis induced by lncRNA HHIP-AS1 overexpression. Through binding to HHIP mRNA, lncRNA HHIP-AS1 recruited ELAVL1 to HHIP mRNA, whereby increasing the mRNA stability and the protein level. Conclusions: This study revealed that down-regulation of HHIP due to lncRNA HHIP-AS1 reduction promoted the osteogenic differentiation of BM-MSCs though removing the suppression of Hedgehog signal.

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“…Recently, lncRNAs have received increasing attention as epigenetic regulators of stem cell differentiation. Many studies have demonstrated that lncRNAs are essential for MSCs' osteogenic differentiation [37][38][39]. The function of lncRNAs in controlling cellular reactions during osseointegration in TNTs has been poorly studied.…”

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“…The overexpression of HHIP‐AS1 was found to increase the expression level of HHIP, inhibit the Hedgehog signaling pathway, and decrease the expression levels of SMO, Gli1, and Gli2. In addition, downregulation of HHIP was found to eliminate the inhibitory effect of HHIP‐AS1 overexpression on osteogenesis (Yin et al, 2022).…”

“…The overexpression of HHIP-AS1 was found to increase the expression level of HHIP, inhibit the Hedgehog signaling pathway, and decrease the expression levels of SMO, Gli1, andGli2. In addition, downregulation of HHIP was found to eliminate the inhibitory effect of HHIP-AS1 overexpression on osteogenesis(Yin et al, 2022).2.3.4 | TGFβ/BMP familyAfter TGF-β/BMP induction, both Smad and p38 MAPK pathways regulate the expression of Runx2 and PPAR-γ. Depletion of the novel lncRNA Bmncr decreases bone mass and increases bone marrow fat content.…”