The Role Of Cardiac Transgelin In Age-dependent Regulation Of Cardiac Response To Pressure Overload

Objective:Cardiomyocytes have an intrinsic capability of sensing and reacting to workload that varies from time to time through a process termed mechanotransduction.This ability declines with age,but the underlying mechani SMs are not well understood.Dynamic deformation of cardiomyocytes takes place during each contractile cycles,mechanical stress applied at the cell surface is tran SMitted throughout the cell via the cortical actin cytoskeleton.[1]Transgelin,or SM22?,is an actin-binding protein that plays critical roles in mediating gelation of actin filaments[2]and stretch sensitivity of cytoskeleton[3-5].This project was designed to evaluate the role of transgelin in the age-dependent regulation of cardiac response to pressure overload.Methods:1 experimental animalIn this experiment,healthy C57BL/6 mice raised in the SPF environment were used,aged 8-24 weeks,and the ambient temperature was 23-25°.The mice fed and ate freely.2 Genotype identification of SM22?knockout miceSM22?heterozygous mice(SM22?^+/-)were randomly selected for 6-8weeks of age and mated according to a male-to-female ratio of 2:1 to breed the pups.The pups of the pups'ears were collected for 4 weeks to extract DNA.?Polymerase chain reaction,PCR?identification of mouse genotypes.3 Establishment of Aortic Arch Constriction Model in mice?TAC?WT mice and SM22?ko mice were randomly selected,depilated after anesthesia,and ligated between the right head brachial artery and the left common carotid artery.The sham operation group was consistent with the TAC group except that it was not ligated.4 Identification of mouse heart functionCardiac function?ejection fraction?of mice was monitored weekly after TAC using Visual Sonics Vevo 770 ultrasonic diagnostic equipment.5 Detection of cardiac stress indicatorsWestern blot was used to detect the expression of various stress indicators in the heart tissue of mice in each group.6 Determination of calcium sparks in CardiomyocytesThe frequency of calcium sparks in myocardial cells of each group was observed under a confocal laser scanning microscope.Results:1.1 the cardiac function?as represented by ejection fraction?of a group of mice between 2 to 6-month-old is not age-dependent.1.2 8 weeks following TAC,the reduction of cardiac function is age dependent with elder mice being more significant.2.1 there was no significant difference in heart function between SM22?^-/-mice in the young and old groups.2.2 the cardiac function of SM22?KO mice was comparable between3-month-old group and 6 month old group. 8 weeks following TAC,the cardiac function of the 6-month-old group declined more.2.3 In KO mice,stress marks such as BNP,?MHC,?MHC were significantly elevated in 6-month-old group than in 2-month-old group.3.1 calcium spark frequency was significantly increased in transgelin KO mice compared with WT control,with most calcium spark properties being significantly altered.3.2 8 weeks following TAC,calcium spark frequency was increased in both WT and transgelin KO group compared with controls,but the increase was more significant in KO group.Conclusions:1.older SM22?KO mice were more vulnerable to pressure overload.2.Impaired mechanical sensing and disrupted calcium handling may contribute to the age-dependent deterioration.