The mammalian heart possesses entire regeneration capacity after birth, which is lost in adulthood. The role of the kinase network in myocardial regeneration remains largely elusive. SGK3 (threonine-protein kinase 3) is a functional kinase we identified previously with the capacity to promote cardiomyocyte proliferation and cardiac repair after myocardial infarction. However, the upstream signals regulating SGK3 are still unknown. Based on the quantitative phosphoproteomics data and pulldown assay, we identified cyclin-dependent kinase 9 (CDK9) as a novel therapeutic target in regeneration therapy. The direct combination between CDK9 and SGK3 was further confirmed by co-immunoprecipitation (Co-IP). CDK9 is highly expressed in the newborn period and rarely detected in the adult myocardium. In vitro, the proliferation ratio of primary cardiomyocytes was significantly elevated by CDK9 overexpression while inhibited by CDK9 knockdown. In vivo, inhibition of CDK9 shortened the time window of cardiac regeneration after apical resection (AR) in neonatal mice, while overexpression of CDK9 significantly promoted mature cardiomyocytes (CMs) to re-enter the cell cycle and cardiac repair after myocardial infarction (MI) in adult mice. Mechanistically, CDK9 promoted cardiac repair by directly activating SGK3 and downstream GSK-3β/β-catenin pathway. Consequently, our study indicated that CDK9 might be a novel target for MI therapy by stimulating myocardial regeneration.

Neonatal mice achieve complete cardiac repair through endogenous myocardial regeneration after apical resection (AR), but this capacity is rapidly lost 7 days after birth. As an upstream inhibitor of cyclin-dependent kinase 4/6- (CDK4/6-) mediated cell cycle activity, p16INK4a is widely involved in regulating tumor and senescence. Given that p16INK4a had a significant negative regulation on cell proliferation, targeting cardiomyocytes (CMs) to inhibit p16INK4a seems to be a promising attempt at myocardial regeneration therapy. The p16INK4a expression was upregulated during perimyocardial regeneration time. Knockdown of p16INK4a stimulated CM proliferation, while p16INK4a overexpression had the opposite effect. In addition, p16INK4a knockdown prolonged the proliferation time window of newborn myocardium. And p16INK4a overexpression inhibited cell cycle activity and deteriorated myocardial regeneration after AR. The quantitative proteomic analysis showed that p16INK4a knockdown mediated the cell cycle progression and intervened in energy metabolism homeostasis. Mechanistically, overexpression of p16INK4a causes abnormal accumulation of reactive oxygen species (ROS) to induce autophagy, while scavenging ROS with N-acetylcysteine can alleviate autophagy and regulate p16INK4a, CDK4/6, and CyclinD1 in a covering manner. And the effect of inhibiting the proliferation of p16INK4a-activated CMs was significantly blocked by the CDK4/6 inhibitor Palbociclib. In summary, p16INK4a regulated CM proliferation progression through CDK4/6 and ROS-related autophagy to jointly affect myocardial regeneration repair. Our study revealed that p16INK4a might be a potential therapeutic target for myocardial regeneration after injury.

Background Papillary thyroid carcinoma (PTC) is the most common thyroid carcinoma, and is prone to cervical lymph node metastases (CLNM). We aim to analyze the correlation between clinical information, ultrasonic parameters of PTC and CLNM. Methods 1335 patients who had pathologically confirmed unifocal PTC were enrolled. Univariate and multivariate logistic analysis were performed to predict CLNM in PTC patients. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic performance. Results Univariate analysis showed that gender, age, maximum tumor diameter and volume, cross-sectional and longitudinal aspect ratio were related to CLNM (P<0.05). Multivariate logistic analysis showed that gender, age, maximum tumor diameter and volume were independent correlative factors, cross-sectional aspect ratio had significant difference for PTC2 to predict CLNM. The area under the curve (AUC) of the maximum tumor diameter and volume was 0.738 and 0.733, respectively. Maximum tumor diameter and volume, and cross-sectional and longitudinal aspect ratio were statistically significant following analysis of variance (P < 0.05). Conclusions Younger age, male, and larger tumor were high risk factors for CLNM in patients with unifocal PTC. Cross-sectional aspect ratio had a more effective predictive value for CLNM in patients with larger thyroid tumors.