Abstract Body (Do not enter title and authors here): Background: Neonatal heart possesses a unique ability to regenerate within seven days of birth. However, the adult mammalian heart is incapable of regeneration. The underlying related mechanisms affecting cardiomyocyte proliferation and heart regeneration remain to be explored.
Methods: Primary cardiomyocytes and hearts from neonatal (P1) mice and adult (P56) mice were used to investigate potential hub proteins involved in heart regeneration. High mobility group box 2 (HMGB2) was identified through using quantitative proteomics with tandem mass tag labeling, RNA-sequencing (RNA-seq) and single-nucleus RNA-seq dataset analyses. Cardiomyocyte-specific HMGB2 knockdown mice and cardiomyocyte-specific HMGB2 overexpression mice were used to evaluate the role of HMGB2 in heart regeneration in vivo. RNA-sequencing analysis was then conducted to identify transcriptome changes associated with HMGB2 in cardiomyocytes. Immunoprecipitation coupled with mass spectrometry and co immunoprecipitation were used to uncover Metastasis-associated protein 2 (MTA2) as a downstream target of HMGB2.
Results: HMGB2 was identified as a key regulator of cardiomyocyte proliferation, whose expression declines during postnatal heart development and increases in the high regenerative potential cardiomyocyte populations in hearts post-injury. Cardiomyocyte-specific HMGB2 knockdown curtailed cardiomyocyte proliferation and impaired heart regeneration following apical resection (AR) in neonatal mice, while cardiomyocyte-specific HMGB2 overexpression enhanced cardiomyocyte proliferation and facilitated heart regeneration post-myocardial infarction in adult mice. Mechanistically, RNA-seq analysis revealed that HMGB2 promotes cardiomyocyte proliferation via activating HIF-1α-mediated glycolysis. This study further found HMGB2 can directly interact with metastasis-associated protein 2 (MTA2) and inhibit its ubiquitination degradation to stabilize HIF-1α protein through immunoprecipitation-mass spectrometry (IP-MS) analysis. Finally, activating HIF-1α or MTA2 could also promote heart regeneration post-myocardial infarction.
Conclusions: HMGB2 plays a crucial role in promoting heart regeneration through regulating glycolysis. Activating the HMGB2-MTA2 axis might serve as potential therapeutic options for regenerative therapies post-myocardial injury.