Recent advances in deep sequencing technologies have revealed that, while less than 2% of the human genome is transcribed into mRNA for protein synthesis, over 80% of the genome is transcribed, leading to the production of large amounts of noncoding RNAs (ncRNAs). It has been shown that ncRNAs, especially long non-coding RNAs (lncRNAs), may play crucial regulatory roles in gene expression. As one of the first isolated and reported lncRNAs, H19 has gained much attention due to its essential roles in regulating many physiological and/or pathological processes including embryogenesis, development, tumorigenesis, osteogenesis, and metabolism. Mechanistically, H19 mediates diverse regulatory functions by serving as competing endogenous RNAs (CeRNAs), Igf2/H19 imprinted tandem gene, modular scaffold, cooperating with H19 antisense, and acting directly with other mRNAs or lncRNAs. Here, we summarized the current understanding of H19 in embryogenesis and development, cancer development and progression, mesenchymal stem cell lineage-specific differentiation, and metabolic diseases. We discussed the potential regulatory mechanisms underlying H19's functions in those processes although more in-depth studies are warranted to delineate the exact molecular, cellular, epigenetic, and genomic regulatory mechanisms underlying the physiological and pathological roles of H19. Ultimately, these lines of investigation may lead to the development of novel therapeutics for human diseases by exploiting H19 functions.

Bone morphogenetic protein 2 (BMP2) effectively induced mesenchymal stem cells (MSCs) osteogenic differentiation hold great potential for bone tissue engineering. However, a global mechanistic view of BMP2-induced osteogenic differentiation of MSCs remains to be fully elucidated. Here, human umbilical cord-derived MSCs (UC-MSCs) were induced with BMP2, three days and five days later, total RNA were extracted and subjected to RNA-sequencing (RNA-Seq) followed with bioinformatic analysis. Osteogenic differentiation abilities were evaluated with Alkaline phosphatase (ALP) staining and osteogenic differentiation marker expression at both mRNA and protein levels. We identified that adenoviral vectors effectively transduced in UC-MSCs and expressed BMP2 in high efficiency. Both on day 3 and day 5, differentially expressed genes (DEGs) were highly enriched in PI3K-Akt signaling pathway. As for the common DEGs among total BMP2 group vs control group, BMP2 (day 3) versus control (day 3) and BMP2 (day 5) versus control (day 5), there were 105 DGEs and highly enriched in PI3K-Akt signaling pathway. Finally, we found that PI3K-Akt signaling inhibitor dramatically inhibited BMP2-iduced osteogenic differentiation of UC-MSCs. We firstly identified that PI3K-Akt signaling pathway plays a pivotal role in BMP2-induced osteogenic differentiation of MSCs, which may apply a new perspective for BMP2 based bone tissue engineering.

Despite the high prevalence of osteoarthritis (OA) in older populations, disease-modifying OA drugs (DMOADs) are still lacking. This study was performed to investigate the effects and mechanisms of the small molecular drug salicin (SA) on OA progression. Primary rat chondrocytes were stimulated with TNF-α and treated with or without SA. Inflammatory factors, cartilage matrix degeneration markers, and cell proliferation and apoptosis markers were detected at the mRNA and protein levels. Cell proliferation and apoptosis were evaluated by EdU assays or flow cytometric analysis. RNA sequencing, molecular docking and drug affinity-responsive target stability analyses were used to clarify the mechanisms. The rat OA model was used to evaluate the effect of intra-articular injection of SA on OA progression. We found that SA rescued TNF-α-induced degeneration of the cartilage matrix, inhibition of chondrocyte proliferation, and promotion of chondrocyte apoptosis. Mechanistically, SA directly binds to IRE1α and occupies the IRE1α phosphorylation site, preventing IRE1α phosphorylation and regulating IRE1α-mediated endoplasmic reticulum (ER) stress by IRE1α-IκBα-p65 signaling. Finally, intra-articular injection of SA-loaded lactic-co-glycolic acid (PLGA) ameliorated OA progression by inhibiting IRE1α-mediated ER stress in the OA model. In conclusion, SA alleviates OA by directly binding to the ER stress regulator IRE1α and inhibits IRE1α-mediated ER stress via IRE1α-IκBα-p65 signaling. Topical use of the small molecular drug SA shows potential to modify OA progression.

Objectives: BMP2 triggers hypertrophic differentiation followed after chondrogenic differentiation of mesenchymal stem cells (MSCs), which blocked the further application of BMP2 mediated cartilage tissue engineering. Here, we investigated the underlying mechanisms of BMP2 mediated hypertrophic differentiation of MSCs. Materials and methods: In vitro and in vivo chondrogenic differentiation models of MSCs were constructed. The expression of H19 in mouse limb was detected by FISH analysis. Transgenes BMP2, H19 silencing and overexpression were expressed by adenoviral vectors. Gene expression was determined by RT-qPCR, Western-blot and Immunohistochemistry. Correlations between H19 expressions and other parameters were calculated with Spearman’s correlation coefficients. The combination of H19 and Runx2 was identified by RIP analysis. Results: We identified H19 expression level was highest in proliferative zone and decreased gradually from pre-hypertrophic zone to hypertrophic zone in mouse limbs. With the stimulation of BMP2, the highest expression level of H19 was followed after the peak expression level of Sox9, meanwhile, H19 expression levels were positively corelated with chondrogenic differentiation markers, especially in the late stage of BMP2 stimulation, and negatively corelated with hypertrophic differentiation markers. Our further experiments found that silencing H19 promoted BMP2 triggered hypertrophic differentiation through in vitro and in vivo tests, which indicted the essential role of H19 for maintaining the phenotype of BMP2 induced chondrocytes. In mechanism, we characterized that H19 combined with Runx2 and promoted BMP2 mediated Runx2 phosphorylation. Conclusions: These findings suggested H19 regulates BMP2 induced hypertrophic differentiation of MSCs by promoting the phosphorylation of Runx2.