MicroRNA‑23a‑5p mediates the proliferation and differentiation of C2C12 myoblasts

Post-transcriptional regulation of myogenic transcription factors during muscle development and pathogenesis

The transcriptional regulation of skeletal muscle (SKM) development (myogenesis) has been documented for over 3 decades and served as a paradigm for tissue-specific cell type determination and differentiation. Myogenic stem cells (MuSC) in embryos and adult SKM are regulated by the transcription factors Pax3 and Pax7 for their stem cell characteristics, while their lineage determination and terminal differentiation are both dictated by the myogenic regulatory factors (MRF) that comprise Mrf4, Myf5, Myogenin, and MyoD. The myocyte enhancer factor Mef2c is activated by MRF during terminal differentiation and collaborates with them to promote myoblast fusion and differentiation. Recent studies have found critical regulation of these myogenic transcription factors at mRNA level, including subcellular localization, stability, and translational regulation. Therefore, the regulation of Pax3/7, MRFs and Mef2c mRNAs by RNA-binding factors and non-coding RNAs (ncRNA), including microRNAs and long non-coding RNAs (lncRNA), will be the focus of this review and the impact of this regulation on myogenesis will be further addressed. Interestingly, the stem cell characteristics of MuSC has been found to be critically regulated by ncRNAs, implying the involvement of ncRNAs in SKM homeostasis and regeneration. Current studies have further identified that some ncRNAs are implicated in the etiology of some SKM diseases and can serve as valuable tools/indicators for prediction of prognosis. The roles of ncRNAs in the MuSC biology and SKM disease etiology will also be discussed in this review.

Integrated analysis of long non-coding RNAs (lncRNAs) and mRNA expression profiles identifies lncRNA PRKG1-AS1 playing important roles in skeletal muscle aging

This study aimed to identify long non-coding RNAs (lncRNAs) involving in the skeletal muscle aging process. Skeletal muscle samples from old and young subjects were collected for lncRNA-sequencing. Differentially expressed genes (DEGs) and DElncRNAs between young and old groups were identified and a co-expression network was built. Further, a dexamethasone-induced muscle atrophy cell model was established to characterize the function of a critical lncRNA. A total of 424 DEGs, including 271 upregulated genes and 153 downregulated genes as well as 152 DElncRNAs including 76 up-regulated and 76 down-regulated lncRNAs were obtained. Functional analysis demonstrated that the DEGs were significantly related to immune response. Coexpression network demonstrated lncRNA AC004797.1, PRKG1-AS1 and GRPC5D-AS1 were crucial lncRNAs. Their expressions were further validated by qRT-PCR in human skeletal muscle and the muscle atrophy cell model. Further in vitro analysis suggested that knock-down of PRKG1-AS1 could significantly increase cell viability and decrease cell apoptosis. qRT-PCR and western blot analyses demonstrated that knock-down of PRKG1-AS1 could increase the expression of MyoD, MyoG and Mef2c. This study demonstrated that lncRNAs of GPRC5D-AS1, AC004797.1 and PRKG1-AS1 might involve the aging-associated disease processes.

The role of physical activity and miRNAs in the vascular aging and cardiac health of dialysis patients

Cardiovascular comorbidities are independent risk factors for mortality in dialysis patients. MicroRNA signaling has an important role in vascular aging and cardiac health, while physical activity is a primary nonpharmacologic treatment for cardiovascular comorbidities in dialysis patients. To identify the relationships between muscle function, miRNA signaling pathways, the presence of vascular calcifications and the severity of cardiovascular comorbidities, we initially enrolled 90 subjects on hemodialysis therapy and collected complete data from 46 subjects. A group of 26 subjects inactiv group (INC) was monitored during 12 weeks of physical inactivity and another group of 20 patients exercise group (EXC) was followed during 12 weeks of intradialytic, moderate intensity, resistance training intervention applied three times per week. In both groups, we assessed the expression levels of myo‐miRNAs, proteins, and muscle function (MF) before and after the 12‐week period. Data on the presence of vascular calcifications and the severity of cardiac comorbidities were collected from the patients’ EuCliD^® records. Using a full structural equitation modelling of the total study sample, we found that the higher the increase in MF was observed in patients, the higher the probability of a decrease in the expression of miR‐206 and TRIM63 and the lower severity of cardiac comorbidities. A reduced structural model in INC patients showed that the higher the decrease in MF, the higher the probability of the presence of calcifications and the higher severity of cardiac comorbidities. In EXC patients, we found that the higher the increase in MF, the lower the probability of higher severity of cardiovascular comorbidities.

MYCN‑amplified neuroblastoma cell‑derived exosomal miR‑17‑5p promotes proliferation and migration of non‑MYCN amplified cells

Neuroblastoma (NB) is considered a highly prevalent extracranial solid tumor in young children, and the upregulation of N‑myc proto‑oncogene (MYCN) is closely associated with the late stages of NB and poor prognostic outcomes. The current study was designed to evaluate the effects of exosomal microRNA (miRNA/miR)‑17‑5p from MYCN‑amplified NB cells on the proliferative and migratory potential of non‑MYCN amplified NB cells. miR‑17‑5p was found to activate the PI3K/Akt signaling cascade by targeting PTEN, and the overexpression of miR‑17‑5p was found to promote cellular migration and proliferation in vitro. Further experimentation revealed that the elevated expression of miR‑17‑5p in SK‑N‑BE(2) cell‑derived exosomes significantly promoted the proliferative and migratory capacities of SH‑SY5Y cells by inhibiting PTEN. Collectively, these findings demonstrated that miR‑17‑5p derived from MYCN‑amplified NB cell exosomes promoted the migration and proliferation of non‑MYCN amplified cells, highlighting an exosome‑associated malignant role for miR‑17‑5p.