--------------------------------------------- # Phosphodiesterase 9a Inhibition in Mouse Models of Diastolic Dysfunction Preferred citation (DataCite format): Methawasin, M., Strom, J., Borkowski, T., Hourani, Z., Runyan, R., Smith, J. E., III, & Granzier, H. (2020). Phosphodiesterase 9a Inhibition in Mouse Models of Diastolic Dysfunction. In Circulation: Heart Failure (Vol. 13, Issue 5). Ovid Technologies (Wolters Kluwer Health). https://doi.org/10.1161/circheartfailure.119.006609 Corresponding Author: Mei Methawasin, Cellular Molecular Medicine, methajit@arizona.edu License: CC BY 4.0 DOI: https://doi.org/10.25422/azu.data.22122197 --------------------------------------------- ## Summary **Background:** Low myocardial cGMP-PKG activity has been associated with increased cardiomyocyte diastolic stiffness in HFpEF. cGMP is mainly hydrolyzed by phosphodiesterases (PDE) 5a and 9a. Importantly, PDE9a expression has been reported to be upregulated in human HFpEF myocardium and chronic administration of a PDE9a inhibitor reverses pre-established cardiac hypertrophy and systolic dysfunction in mice subjected to TAC (Transverse Aortic Constriction). We hypothesized that inhibiting PDE9a activity ameliorates diastolic dysfunction. **Methods and Results:** Two diastolic dysfunction mouse models were studied: 1) TAC-DOCA (deoxycorticosterone acetate) and 2) _Leprdb/db_ , a metabolically induced diastolic dysfunction model. The effect of acute PDE9a inhibition was investigated in intact cardiomyocytes isolated from TAC-DOCA mice; no acute cellular stiffness reduction was found. For chronic inhibition, mice were implanted with osmotic minipumps containing either PDE9a inhibitor or vehicle. PDE9a inhibition (5 and 8 mg/kg/day) resulted in reduced LV chamber stiffness in TAC-DOCA, but not in _Leprdb/db_ mice. Passive cardiomyocyte stiffness was reduced by chronic PDE9a inhibition, with no differences in myocardial fibrosis or cardiac morphometry. PDE9a inhibition increased the ventricular- arterial (VA) coupling ratio, reflecting impaired systolic function. **Conclusions:** Chronic PDE9a inhibition lowers LV chamber stiffness in TAC- DOCA mice. However, the usefulness of PDE9a inhibition to treat high diastolic stiffness may be limited as the required PDE9a inhibitor dose also impairs systolic function, observed as a decline in ventricular-arterial coordination, in this model. Cardiac functional analysis was conducted using the: - in vivo: echocardiogram, pressure-volume analysis, treadmill exercise stress test - cardiomyocyte mechanical studies: intact and permeabilized cardiomyocytes The PDE9a activity in the mouse's left ventricle was measured using the HPLC technique. The mouse plasma levels of PF 4449613 ( PDE9a inhibitor) were measured by mass spectrometry. The PKG and cGMP levels were measured by a commercial ELISA kit. The extent of myocardial fibrosis was studied by Picrosirius red stain and RNA study. --------------------------------------------- ## Files and Folders Each Zip file has its own read-me file ( explaining the names of each subfolder/file), protocol file, analyzed Excel files, and the final figures corresponding to the final result. --------------------------------------------- ## Materials and Methods Some specialized software is required to view the raw data files: Intact cardiomyocyte: IonWizard software 6.3 or higher version (Ion optix) Permeabilized cardiomyocyte: 600A Aurora Scientific Pressure-volume analysis:LabScribe3 or higher version (iWorx) Treadmill exercise stress test: PhenoMaster software (TSE Systems). The analysis software is available to download through the website of company. --------------------------------------------- ## Contributor Roles The roles are defined by the CRediT taxonomy http://credit.niso.org/ - Methawasin, M., University of Arizona: Funding acquisition, Investigation, Data curation, Formal Analysis, Writing – original draft - Strom, J., University of Arizona: Investigation, Data curation, Writing – original draft - Borkowski, T., University of Arizona: Investigation, Data curation - Hourani, Z., University of Arizona: Investigation, Data curation - Runyan, R., University of Arizona: Resources, Supervision - Smith, J. E. III, University of Arizona: Methodology - Granzier, H., University of Arizona: Funding acquisition, Conceptualization, Writing – review & editing