Loss of circIGF1R Suppresses Cardiomyocytes Proliferation by Sponging miR-362-5p.

Circular RNAs (circRNAs) are generally formed by the back-splicing of precursor mRNA. Increasing evidence implicates the important role of circRNAs in cardiovascular diseases. However, the role of circ-insulin-like growth factor 1 receptor (circIGF1R) in cardiomyocyte (CM) proliferation remains unclear. Here, we investigated the potential role of the circIGF1R in the proliferation of CMs. We found that circIGF1R expression in heart tissues and primary CMs from adult mice was significantly lower than that in neonatal mice at postnatal 1 day (p1). Increased circIGF1R expression was detected in the injured neonatal heart at 0.5 and 1 days post-resection. circIGF1R knockdown significantly decreased the proliferation of primary CMs. Combined prediction software, luciferase reporter gene analysis, and quantitative real time-PCR (qPCR) revealed that circIGF1R interacted with miR-362-5p. A significant increase in miR-362-5p expression was detected in the adult heart compared with that in the neonatal heart. Further, heart injury significantly decreased the expression of miR-362-5p in neonatal mice. Treatment with miR-362-5p mimics significantly suppressed the proliferation of primary CMs, whereas knockdown of miR-362-5p promoted the CMs proliferation. Meanwhile, miR-362-5p silencing can rescue the proliferation inhibition of CMs induced by circIGF1R knockdown. Target prediction and qPCR validation revealed that miR-362-5p significantly inhibited the expression of Phf3 in primary CMs. In addition, decreased Phf3 expression was detected in adult hearts compared with neonatal hearts. Consistently, increased Phf3 expression was detected in injured neonatal hearts compared with that in sham hearts. Knockdown of Phf3 markedly repressed CMs proliferation. Taken together, these findings suggest that circIGF1R might contribute to cardiomyocyte proliferation by promoting Pfh3 expression by sponging miR-362-5p and provide an important experimental basis for the regulation of heart regeneration.

Mettl3-mediated m6A modification of Fgf16 restricts cardiomyocyte proliferation during heart regeneration.

Cardiovascular disease is the leading cause of death worldwide due to the inability of adult heart to regenerate after injury. N6-methyladenosine (m6A) methylation catalyzed by the enzyme methyltransferase-like 3 (Mettl3) plays an important role in various physiological and pathological bioprocesses. However, the role of m6A in heart regeneration remains largely unclear. To study m6A function in heart regeneration, we modulated Mettl3 expression in vitro and in vivo. Knockdown of Mettl3 significantly increased the proliferation of cardiomyocytes and accelerated heart regeneration following heart injury in neonatal and adult mice. However, Mettl3 overexpression decreased cardiomyocyte proliferation and suppressed heart regeneration in postnatal mice. Conjoint analysis of methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq identified Fgf16 as a downstream target of Mettl3-mediated m6A modification during postnatal heart regeneration. RIP-qPCR and luciferase reporter assays revealed that Mettl3 negatively regulates Fgf16 mRNA expression in an m6A-Ythdf2-dependent manner. The silencing of Fgf16 suppressed the proliferation of cardiomyocytes. However, the overexpression of ΔFgf16, in which the m6A consensus sequence was mutated, significantly increased cardiomyocyte proliferation and accelerated heart regeneration in postnatal mice compared with wild-type Fgf16. Our data demonstrate that Mettl3 post-transcriptionally reduces Fgf16 mRNA levels through an m6A-Ythdf2-dependen pathway, thereby controlling cardiomyocyte proliferation and heart regeneration.

Cardiovascular diseases are one of the world's biggest killers. Even for patients who survive a heart attack, recovery can be difficult. This is because ­ unlike some amphibians and fish ­ humans lack the ability to produce enough new heart muscle cells to replace damaged tissue after a heart injury. In other words, the human heart cannot repair itself. Molecules known as messenger RNA (mRNA) carry the 'instructions' from the DNA inside the cell nucleus to its protein-making machinery in the cytoplasm of the cell. These messenger molecules can also be altered by different enzymes that attach or remove chemical groups. These modifications can change the stability of the mRNA, or even 'silence' it altogether by stopping it from interacting with the protein-making machinery, thus halting production of the protein it encodes. For example, a protein called Mettl3 can attach a methyl group to a specific part of the mRNA, causing a reversible mRNA modification known as m⁶A. This type of alteration has been shown to play a role in many conditions, including heart disease, but it has been unclear whether m⁶A could also be important for the regeneration of heart tissue. To find out more, Jiang, Liu, Chen et al. studied heart injury in mice of various ages. Newborn mice can regenerate their heart muscle for a short time, but adult mice lack this ability, which makes them a useful model to study heart disease. Analyses of the proteins and mRNAs in mouse heart cells confirmed that both Mettl3 and m⁶A-modified mRNAs were present. The amount of each also increased with age. Next, experiments in genetically manipulated mice revealed that removing Mettl3 greatly improved tissue repair after heart injury in both newborn and adult mice. In contrast, mouse hearts that produced abnormally high quantities of Mettl3 were unable to regenerate ­ even if the mice were young. Moreover, a detailed analysis of gene activity revealed that Mettl3 was suppressing heart regeneration by decreasing the production of a growth-promoting protein called FGF16. These results reveal a key biological mechanism controlling the heart's ability to repair itself after injury. In the future, Jiang et al. hope that Mettl3 can be harnessed for new, effective therapies to promote heart regeneration in patients suffering from heart disease.

[Clinical Study on Early Extubation and Sequential Non-Invasive Respiratory Support for Children with Acute Respiratory Failure Receiving Invasive Mechanical Ventilation].

Objective: To explore the treatment outcome of the strategy of early extubation and then switching to non-invasive mechanical ventilation in children with acute respiratory failure, and the safety and feasibility of using the strategy to replace traditional methods. Methods: A total of 102 children, aged between 1 month to 14 years old, who had acute respiratory failure and were admitted to the pediatric ICU of West China Second University Hospital, Sichuan University between January 2019 and December 2020 were enrolled and randomly assigned to treatment group 1 (n=55) and treatment group 2 (n=47). In addition, 53 children who had the same condition in the 12 month prior to the beginning of the study were included in the control group. In the two treatment groups, the patients were extubated first, and then weaned off the ventilator. In group 1, when the patient met the invasive-non-invasive switching criteria, the tracheal tube was pulled out and non-invasive bi-level positive airway pressure (BiPAP) ventilation was used for respiratory support. In group 2, high-flow nasal cannula (HFNC) oxygen therapy was used for respiratory support. The traditional progressive weaning method was adopted for the control group (extubing and weaning were performed at the same time). The incidence of ventilator-associated pneumonia (VAP) during the period of tracheal intubation was compared and the mortality of the two groups was evaluated from the point when the patients were recruited. At the time of extubation in the treatment groups and extubation plus weaning in the control group, the pressure support levels, or PC above PEEP, intubation time, sequential time (between 2 treatment groups only), weaning failure rate, and the incidence of laryngeal edema and nasal pressure ulcer were compared. Results: The subjects of the study were predominantly infants (93 cases, 60%) and young children (31 cases, 20%). Among the 155 cases, 82 (53%) were male. There was no statistical difference in age distribution or gender among the groups. There was no significant difference in the clinical indicators among the three groups before tracheal intubation. At the time of extubation, the PC above PEEP in the two treatment groups was higher than that in the control group, and higher in group 1 than that of group 2, the difference being statistically significant (P<0.05). The intubation time of the two treatment groups was shorter than that of the control group, and shorter in group 1 than that of group 2 (P<0.05). The sequential time of group 2 was shorter than that of group 1 (P<0.05). The extubation failure rate and the incidence of VAP in the two treatment groups were lower than those in the control group, and there was no statistically significant difference between the two treatment groups. The incidence of nasal pressure ulcers in group 1 was higher than that in the other two groups (P<0.05). There was 1 death in treatment group 1, and no deaths in treatment group 2 or the control group. There was no significant difference in mortality or the incidence of laryngeal edema after extubation in the three groups. Conclusion: Early extubation and then switching to non-invasive mechanical ventilation can be well tolerated by the patients, and can be used in clinical practice as an effective weaning method for children with acute respiratory failure.

Associations among birth weight, placental weight, gestational period and product quality indicators of umbilical cord blood units.

INTRODUCTION: Numbers of CD34+ cell and total nucleated cell (TNC) and cord blood volume are commonly used as indicators for haematopoietic potential of umbilical cord blood (UCB) units. The purpose of this study was to investigate the relationship between donor-related factors and the quality indicators of UCB. METHODS: Obstetric and neonatal clinical laboratory data of a total of 1549 UCB units were obtained from Buddhist Tzu Chi Stem Cells Center (BTCSCC) Cord Blood Bank. A retrospective multivariate analysis was conducted to analyze the data. RESULTS: Our results showed that birth weight had positive correlations with each of the clinical features of CD34+ cell number, TNC count and unit volume of UCB, followed by the placental weight. Longer gestational period would decrease CD34+ cell number and volume of UCB. Female baby and mode of vaginal delivery of neonates were found to have larger amount of TNC in UCB. CONCLUSION: Our results would be helpful and beneficial in building up standard criteria for evaluating stored UCB units.