Adssl1-mediated purine synthesis modulates cardiomyocyte proliferation and heart regeneration

Abstract Introduction The enhancement of pre-exist cardiomyocyte proliferation has been proved to be an effective treatment of myocardial infarction(MI) (1-2). Purine bases from the de novo purine synthesis (DNPS) pathways is the critical source of nucleotide synthesis for proliferative cell (3). The muscle specific isoform of adenylosuccinate synthase (Adssl1) catalyses the last step of DNPS pathway (4). Patients with Adssl1 mutation develop cardiomyopathy at 13-15 years (5). Nevertheless, its role and mechanism in cardiomyocyte cell-cycle re-entry and heart regeneration remain unknown. Purpose To explore the effect and underlying mechanism of Adssl1 and its mediated DNPS pathway in cardiomyocyte proliferation and heart regeneration. Methods We used qRT-PCR, Western blot and Immunofluorescence to assess the expression of Adssl1 during heart developement and heart regeneration after apical resection (AR) operation. Using newly generated loss- and gain-of-function genetic tools to investigate the role of Adssl1 in cardiac regeneration after AR or MI operation. Transcriptomic RNA sequencing (RNA-Seq) and liquid chromatography-tandem mass spectrometry (LC/MS) allowed us to determine the metabolism of Adssl1 in modulating cardiomyocyte proliferation. Results Here, we found that Adssl1 was increased during heart regeneration. Depletion of Adssl1 in neonatal hearts significantly inhibited purine synthesis pathway and attenuated heart regenerative capacity after AR operation. Cardiomyocyte-specific overexpression of Adssl1 extended postnatal regenerative window and induced a robust cell-cycle re-entry after MI, leading to a decrease in fibrosis scar size and improvement of cardiac function. Adssl1 caused accumulation of Inosine, which could promote the cardiac repair in mice. Mechanistically, we demonstrated that Adssl1 significantly involved in modulating mTORC1/S6K pathway. Conclusion Collectively, our study elucidates the role of Adssl1 in modulating cardiac proliferation and heart regeneration through activating mTORC1/S6K pathway after MI. Notably, Inosine has the potential to be employed as an effective agent in regulating cardiac proliferation and myocardial repair.Heart regeneration