Transcriptome-wide mA methylome during osteogenic differentiation of human adipose-derived stem cells.

Objectives: Adipose-derived stem cells are frequently used for bone regeneration both in vitro and in vivo. N-methyladenosine (mA) is the most abundant post-transcriptional modification on eukaryotic RNAs and plays multifaceted roles in development and diseases. However, the regulatory mechanisms of mA in osteogenic differentiation of human adipose-derived stem cells (hASCs) remain elusive. The present study aimed to build the transcriptome-wide mA methylome during the osteogenic differentiation of hASCs.

Materials And Methods: hASCs were harvested after being cultured in a basic or osteogenic medium for 7 days, and the osteogenic differentiation was validated by alkaline phosphatase (ALP) and Alizarin Red S staining, ALP activity assay, and qRT-PCR analysis of ALP, RUNX2, BGLAP, SPP1, SP7, and COL1A1 genes. The mA level was colorimetrically measured, and the expression of mA regulators was confirmed by qRT-PCR and western blot. Moreover, mA MeRIP-seq and RNA-seq were performed to build the transcriptome and mA methylome. Furthermore, bioinformatic analyses including volcano plots, Venn plots, clustering analysis, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, gene sets enrichment analysis, and protein-protein interaction analysis were conducted.

Results: In total, 1145 differentially methylated peaks, 2261 differentially expressed genes, and 671 differentially methylated and expressed genes (DMEGs) were identified. GO and KEGG pathway analyses conducted for these DMEGs revealed extensive and osteogenic biological functions. The "PI3K-Akt signaling pathway"; "MAPK signaling pathway"; "parathyroid hormone synthesis, secretion, and action"; and "p53 signaling pathway" were significantly enriched, and the DMEGs in these pathways were identified as mA-specific key genes. A protein-protein interaction network based on DMEGs was built, and VEGFA, CD44, MMP2, HGF, and SPARC were speculated as the hub DMEGs.

Conclusions: The total mA level was reduced with osteogenic differentiation of hASCs. The transcriptome-wide mA methylome built in the present study indicated quite a few signaling pathways, and hub genes were influenced by mA modification. Future studies based on these epigenetic clues could promote understanding of the mechanisms of osteogenic differentiation of hASCs.