Myocardial infarction (MI) occurs when the coronary blood supply is interrupted. As a consequence, cardiomyocytes are irreversibly damaged and lost. Unfortunately, current therapies for MI are unable to prevent progression towards heart failure. As the renewal rate of cardiomyocytes is minimal, the optimal treatment should achieve effective cardiac regeneration, possibly with stem cells transplantation. In that context, our research group identified the cardiac atrial appendage stem cells (CASCs) as a new cellular therapy. However, CASCs are transplanted into a hostile environment, with elevated levels of advanced glycation end products (AGEs), which may affect their regenerative potential. In this study, we hypothesize that pyridoxamine (PM), a vitamin B6 derivative, could further enhance the regenerative capacities of CASCs transplanted after MI by reducing AGEs’ formation. Methods and Results: MI was induced in rats by ligation of the left anterior descending artery. Animals were assigned to either no therapy (MI), CASCs transplantation (MI + CASCs), or CASCs transplantation supplemented with PM treatment (MI + CASCs + PM). Four weeks post-surgery, global cardiac function and infarct size were improved upon CASCs transplantation. Interstitial collagen deposition, evaluated on cryosections, was decreased in the MI animals transplanted with CASCs. Contractile properties of resident left ventricular cardiomyocytes were assessed by unloaded cell shortening. CASCs transplantation prevented cardiomyocyte shortening deterioration. Even if PM significantly reduced cardiac levels of AGEs, cardiac outcome was not further improved. Conclusion: Limiting AGEs’ formation with PM during an ischemic injury in vivo did not further enhance the improved cardiac phenotype obtained with CASCs transplantation. Whether AGEs play an important deleterious role in the setting of stem cell therapy after MI warrants further examination.

Chronically increased levels of high molecular weight advanced glycation end products (HMW-AGEs) are known to induce cardiovascular dysfunction. Whether an acute increase in HMW-AGE levels affects vascular function remains unknown. In this study, we examined whether acute exposure to HMW-AGEs disturbs aortic vasomotor function. Aortae were obtained from healthy male rats and were acutely pre-treated with HMW-AGEs in organ baths. Aortic relaxation responses to cumulative doses of acetylcholine (ACh), in the presence or absence of superoxide dismutase (SOD), were measured after precontraction with phenylephrine (PE). Furthermore, levels of 3-nitrotyrosine were evaluated on aortic paraffine sections. In our study, we show that acute exposure to HMW-AGEs significantly decreases the aortic relaxation response to ACh. SOD pre-treatment prevents acute HMW-AGEs-induced impairment by limiting superoxide formation. In conclusion, our data demonstrate that acute exposure to HMW-AGEs causes adverse vascular remodelling, characterised by disturbed vasomotor function due to increased oxidative stress. These results create opportunities for future research regarding the acute role of HMW-AGEs in cardiovascular dysfunction.

Introduction: Although doxorubicin (DOX) is an efficient anthracycline agent used to treat cancer, it induces cardiotoxicity and mortality in cancer survivors. Cardioprotection is inadequate. The vitamin B 6 -derivative pyridoxamine (PM) has shown to be cardioprotective in diverse cardiac diseases. Whether PM offers cardioprotection after DOX treatment is unknown. We hypothesized that PM limits cardiac impairment after DOX treatment by reducing cardiac fibrosis and inflammation. Methods: Female Sprague Dawley rats were weekly treated with 2 mg/kg DOX or saline IV for 8 weeks. At DOX treatment onset, 2 extra groups received PM (1 g/L) via the drinking water. Echocardiographic (4D) and hemodynamic parameters were assessed at week 8, together with plasma BNP. PCR analysis was performed on left ventricular tissue to evaluate fibrosis and inflammation. Data were compared using 1-way ANOVA, Kruskal-Wallis test or 2-way ANOVA with post-hoc tests as appropriate. Results: As shown in Table 1, cardiac impairment by DOX was prevented by PM. In addition, DOX significantly increased the expression of fibrosis markers, such as TGFβ (0.29 ± 0.02 vs. 0.69 ± 0.09 a.u., p<0.0001), LOX (0.055 ± 0.002 vs. 0.590 ± 0.174 a.u., p<0.01), collagen type 1 (0.21 ± 0.02 vs. 0.62 ± 0.11 a.u., p<0.001) and interstitial collagen (4.6 ± 0.3 vs. 7.7 ± 0.6%, p<0.001). DOX also increased the inflammation marker IL-6 (0.13 ± 0.03 vs. 0.73 ± 0.13 a.u., p<0.01). PM treatment significantly lowered all these parameters (p<0001, p<0.001, p<0.01, p<0.01 and p<0.01 respectively). Conclusions: In conclusion, our data show that DOX causes dilated cardiomyopathy with reduced ejection fraction, accompanied by cardiac fibrosis and myocarditis. As PM limits this adverse phenotype, it could be a novel cardioprotective strategy for DOX-treated cancer patients.