Downregulation of ALKBH5 rejuvenates aged human mesenchymal stem cells and enhances their therapeutic efficacy in myocardial infarction

Despite promising results in myocardial infarction (MI), mesenchymal stem cell (MSC)‐based therapy is limited by cell senescence. N6‐methyladenosine (m6A) messenger RNA methylation has been reported to be closely associated with cell senescence. Nonetheless, its role in the regulation of MSC senescence remains unclear. We examined the role of ALKB homolog 5 (ALKBH5) in regulating MSC senescence and determined whether ALKBH5 downregulation could rejuvenate aged MSCs (AMSCs) to improve their therapeutic efficacy for MI. RNA methylation was determined by m6A dot blotting assay. MSC senescence was evaluated by senescence‐associated β‐galactosidase (SA‐β‐gal) staining. A mouse model of acute MI was established by ligation of the left anterior decedent coronary artery (LAD). Compared with young MSCs (YMSCs), m6A level was significantly reduced but ALKBH5 was greatly increased in AMSCs. Overexpression of ALKBH5 reduced m6A modification and accelerated YMSC senescence. Conversely, ALKBH5 knockdown increased m6A modifications and alleviated AMSC senescence. Mechanistically, ALKBH5 regulated the m6A modification and stability of CDKN1C mRNA, which further upregulated CDKN1C expression, leading to MSC senescence. CDKN1C overexpression ameliorated the inhibition of cellular senescence of ALKBH5 siRNA‐treated AMSCs. More importantly, compared with AMSCs, shALKBH5‐AMSCs transplantation provided a superior cardioprotective effect against MI in mice by improving MSC survival and angiogenesis. We determined that ALKBH5 accelerated MSC senescence through m6A modification‐dependent stabilization of the CDKN1C transcript, providing a potential target for MSC rejuvenation. ALKBH5 knockdown rejuvenated AMSCs and enhanced cardiac function when transplanted into the mouse heart following infarction. ALKBH5 increases in AMSCs, which interacted with CDKN1C mRNA by m6A RNA demethylation, then increases CDKN1C mRNA stability and decays the mRNA degradation. Conversely, knockdown ALKBH5 accelerates CDKN1C mRNA degradation, downregulates CDKN1C expression, and finally rejuvenates AMSCs. MSCs transplantation improves cardiac function, promotes angiogenesis, and decreases infarct size and cardiac fibrosis. Moreover, shALKBH5‐AMSCs were superior to AMSCs at improving heart function following MI in mice.