Checkpoint Kinase 1 Stimulates Endogenous Cardiomyocyte Renewal and Cardiac Repair by Binding to Pyruvate Kinase Isoform M2 C-Domain and Activating Cardiac Metabolic Reprogramming in a Porcine Model of Myocardial Ischemia/Reperfusion Injury.

BACKGROUND: The regenerative capacity of the adult mammalian hearts is limited. Numerous studies have explored mechanisms of adult cardiomyocyte cell-cycle withdrawal. This translational study evaluated the effects and underlying mechanism of rhCHK1 (recombinant human checkpoint kinase 1) on the survival and proliferation of cardiomyocyte and myocardial repair after ischemia/reperfusion injury in swine. METHODS AND RESULTS: Intramyocardial injection of rhCHK1 protein (1 mg/kg) encapsulated in hydrogel stimulated cardiomyocyte proliferation and reduced cardiac inflammation response at 3 days after ischemia/reperfusion injury, improved cardiac function and attenuated ventricular remodeling, and reduced the infarct area at 28 days after ischemia/reperfusion injury. Mechanistically, multiomics sequencing analysis demonstrated enrichment of glycolysis and mTOR (mammalian target of rapamycin) pathways after rhCHK1 treatment. Co-Immunoprecipitation (Co-IP) experiments and protein docking prediction showed that CHK1 (checkpoint kinase 1) directly bound to and activated the Serine 37 (S37) and Tyrosine 105 (Y105) sites of PKM2 (pyruvate kinase isoform M2) to promote metabolic reprogramming. We further constructed plasmids that knocked out different CHK1 and PKM2 amino acid domains and transfected them into Human Embryonic Kidney 293T (HEK293T) cells for CO-IP experiments. Results showed that the 1-265 domain of CHK1 directly binds to the 157-400 amino acids of PKM2. Furthermore, hiPSC-CM (human iPS cell-derived cardiomyocyte) in vitro and in vivo experiments both demonstrated that CHK1 stimulated cardiomyocytes renewal and cardiac repair by activating PKM2 C-domain-mediated cardiac metabolic reprogramming. CONCLUSIONS: This study demonstrates that the 1-265 amino acid domain of CHK1 binds to the 157-400 domain of PKM2 and activates PKM2-mediated metabolic reprogramming to promote cardiomyocyte proliferation and myocardial repair after ischemia/reperfusion injury in adult pigs.

Exceptional points enhance sum sideband generation in a mechanical PT-symmetric system.

Systems exhibiting parity-time (PT) symmetry are, in general, non-Hermitian systems, in which exceptional points (EPs) emerge when the system transits from the PT-symmetric phase to the broken-PT-symmetric phase. Based on the abnormal exponential amplification effect in EPs, it is often used to generate, control and transmit light in non-Hermitian systems. In this paper, we theoretically analyze the generation of the frequency components at the sum sideband by considering the nonlinear terms of the optomechanical dynamics in a double-probe-field-driven mechanical PT-symmetric system. Using experimentally achievable parameters, we demonstrate that the efficiency of sum sideband generation (SSG) can be significantly enhanced in EPs, even that the efficiency of SSG can be raised by three orders of magnitude compared to the general optomechanical system by adjusting the appropriate system parameters. These results are beneficial to explore the transmission and conversion of light in chip-scale optical communications.

[Influencing Factors of Ozone Concentration in Xi'an Based on Generalized Additive Models].

Based on the ozone monitoring data from 2014 to 2018, we presented the variation of ozone concentration in Xi'an and revealed the effects of ozone concentration by meteorological factors based on the generalized additive model (GAM). The results showed that ① with increasing ozone concentration year by year, the assessment standard of ozone pollution was overtaken by three consecutive years since 2016. However, the rising trend was slowed down since 2017 as a result of the strengthened pollution control during summer. ② The monthly curve of ozone concentration was presented as a reversed "V" model with a rising trend accompanying the rising temperature from January to July and a decreasing one during the rest of the year, peaking in July in terms of average monthly ozone concentration. However, this model would turn into an "M" in years with high precipitation when the valley witnessed the highest precipitation in a month. ③ The ozone pollution increased from the year 2014 to 2018 with a stretch-forward ozone polluted time. Furthermore, the rates of ozone non-attainment increased from 1.9% in 2014 to 14% in 2018. In addition, the time ozone pollution emerged advanced from July to May. ④ Based on the GAM model, ozone concentration was non-colinearly related to temperature, air pressure, sunshine duration, and relative humidity. However, the curves of these factors varied considerably, with a positive influence of temperature and sunshine duration and a negative influence of air pressure and relative humidity. The influence of precipitation was mainly witnessed in summers, while no influence of wind was observed. Furthermore, ozone pollution can be easily triggered under the following conditions:temperature>24℃, air pressure <962 hPa, sunshine duration>9 h, and a relative humidity 36%-65% with no rain.

Generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions.

We investigate theoretically the generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions. It is shown that the generation of frequency components at the sum sideband stems from the nonlinear optomechanical interactions via two-phonon processes in the quadratically coupled optomechanical system, while an optical parametric amplifier (OPA) inside the system can considerably improve the sum sideband generation (SSG). The dependence of SSG on the system parameters, including the power of the control field, the frequency detuning of the probe fields and the nonlinear gain of OPA are analyzed in detail. Our analytic calculation indicates that the SSG can be obtained even under weak driven fields and greatly enhanced via meeting the matching conditions. The effect of SSG may have potential applications for achieving measurement of electric charge (or other weak forces) with higher precision and on-chip manipulation of light propagation.

Biomechanical characterization of a novel ring connector for sutureless aortic anastomosis.

The surgical treatment for aortic diseases remains a challenge for any cardiac surgeon. The use of sutureless ring connector in aortic anastomosis can simplify the procedure and shorten anastomosis time. Therefore, we developed a novel device for sutureless aortic anastomosis. A series of experiments were carried out for tensile and leakproof-capacity assessments to verify the feasibility of the ring connector by using fresh swine aorta samples. In in vivo test, the ring connector was implanted in 6 swine with follow-up of 6 months. Radiographic and pathological studies of the aorta were performed. In the tensile tests, the strength was 32.7±5.9 Newton (N) in the sutureless anastomosis group, compared with 73.3±12.5 N in the control group by traditional manual suture. In the leakproof-capacity assessment, no sign of either leakage or bursting was evident at 280 mmHg of internal pressure in the aorta samples. In in vivo tests, it took 9.47±0.3 minutes for the sutureless anastomosis, compared with 15.58±1.39 minutes for hand-sewn suturing. Insertion was easy and rapid. Radiographic and pathological studies were performed at first month, third month and sixth month after surgery, each time obtained from the two swine, showed patency of the anastomosis and no signs of stenosis, blood leakage, migration or pseudoaneurysm formation, except one paralyzed swine developed of thrombo-occlusion at the site of the sutureless anastomosis. The result indicates that this novel ring connector offers considerable promise for sutureless aortic anastomosis.

[Biocompatibility of polylactic-co-glycolic acid for culturing bFGF gene-transfected bone marrow stromal cells and application of the cell complex for repairing rabbit cartilage defect].

OBJECTIVE: To evaluate the biocompatibility of polylactic-co-glycolic acid (PLGA) for culturing bFGF gene-transfected bone marrow stromal cells (BMSCs) and assess the feasibility of this cell complex for repairing cartilage defect in rabbits using tissue engineering method. METHODS: BMSCs transfected by bFGF gene were cultured on PLGA matrix to assess the biocompatibility of PLGA. The cell complex was then implanted into the cartilage defect in rabbits, and its effect in cartilage defect repair was evaluated by histological observation and immunohistochemical staining. RESULTS: BMSCs transfected by bFGF gene grew normally on PLGA matrix. After implantation, the complex showed good effect for cartilage defect repair in rabbits. CONCLUSION: PLGA has good biocompatibility with the transfected BMSCs, and the cell complex can be used for repairing rabbit cartilage defect and may potentially serve as a substitute of cartilage autograft.

[Construction of eukaryotic expression vectors of basic fibroblast growth factor and transfection in rabbit bone marrow stromal cells].

OBJECTIVE: To investigate approach and possibility of transferring basic fibroblast growth factor (bFGF) gene into rabbit bone marrow stromal cells (BMSCs). METHODS: The eukaryotic expression vectors harboring bFGF cDNA were constructed and transfected into rabbit BMSCs mediated by liposome. The transcription and expression of bFGF gene in the transfected BMSCs were detected by means of morphological observation, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and RT-PCR. The changes in the biological characteristics of the transfected MSCs were also observed. RESULTS: Stable overexpression of bFGF protein was detected in the transfected BMSCs, which showed differentiation towards chondrocyte lineage. CONCLUSION: Stable expression of bFGF gene in transfected BMSCs can induce cell differentiation into chondrocyte lineage.