The use of doxorubicin (DOX) chemotherapy is restricted due to dose-dependent cardiotoxicity. Pyridoxamine (PM) is a vitamin B6 derivative with favorable effects on diverse cardiovascular diseases, suggesting a cardioprotective effect on DOX-induced cardiotoxicity. The cardioprotective nature of PM was investigated in a rat model of DOX-induced cardiotoxicity. Six-week-old female Sprague Dawley rats were treated intravenously with 2 mg/kg DOX or saline (CTRL) weekly for eight weeks. Two other groups received PM via the drinking water next to DOX (DOX+PM) or saline (CTRL+PM). Echocardiography, strain analysis, and hemodynamic measurements were performed to evaluate cardiac function. Fibrotic remodeling, myocardial inflammation, oxidative stress, apoptosis, and ferroptosis were evaluated by various in vitro techniques. PM significantly attenuated DOX-induced left ventricular (LV) dilated cardiomyopathy and limited TGF-β1-related LV fibrotic remodeling and macrophage-driven myocardial inflammation. PM protected against DOX-induced ferroptosis, as evidenced by restored DOX-induced disturbance of redox balance, improved cytosolic and mitochondrial iron regulation, and reduced mitochondrial damage at the gene level. In conclusion, PM attenuated the development of cardiac damage after DOX treatment by reducing myocardial fibrosis, inflammation, and mitochondrial damage and by restoring redox and iron regulation at the gene level, suggesting that PM may be a novel cardioprotective strategy for DOX-induced cardiomyopathy.

Rodents models of myocardial infarction (MI) continue to be frequently used in preclinical cardiovascular research, despite alternative approaches being on the rise. The commonly used coronary artery permanent ligation (PL) approach is often hampered by substantial perioperative mortality and variable success rates. We optimized the rat PL protocol by relying exclusively on isoflurane inhalation anesthesia by introducing a standardized intubation setup, maintaining strict control of body temperature throughout surgery, and surgical technique refinements. The latter included gentle mobilization of the Pectoralis major and thymus, a medial thoracotomy through the third intercostal space, and the use of a reference ligature to facilitate reliable identification and ligation of the left anterior descending coronary artery (LAD). Cardiac rhythm was continuously monitored, and extubation was carefully timed to reduce complications. With this protocol, perioperative mortality was reduced to zero and successful ligation was obtained in 94% of animals (n = 172). Echocardiography and histology confirmed consistent induction of infarcts. By lowering invasiveness and improving survival and reproducibility, the refined PL method enhances both the reliability of preclinical research and compliance with the 3Rs, representing a meaningful step forward for studies in cardiac regeneration.

Individuals with type 2 diabetes mellitus (T2DM) are at an increased risk for heart failure, yet preventive cardiac care is suboptimal in this population. Pyridoxamine (PM), a vitamin B₆ analog, has been shown to exert protective effects in metabolic and cardiovascular diseases. In this study, we aimed to investigate whether PM limits adverse cardiac remodeling and dysfunction in rats who develop T2DM. Male rats received a standard chow diet or Western diet (WD) for 18 weeks to induce prediabetes. One WD group received additional PM (1 g/L) via drinking water. Glucose tolerance was assessed with a 1 h oral glucose tolerance test. Cardiac function was evaluated using echocardiography and hemodynamic measurements. Histology on left ventricular (LV) tissue was performed. Treatment with PM prevented the increase in fasting plasma glucose levels compared to WD-fed rats (p < 0.05). LV cardiac dilation tended to be prevented using PM supplementation. In LV tissue, PM limited an increase in interstitial collagen deposition (p < 0.05) seen in WD-fed rats. PM tended to decrease 3-nitrotyrosine and significantly lowered 4-hydroxynonenal content compared to WD-fed rats. We conclude that PM alleviates interstitial fibrosis and oxidative stress in the hearts of WD-induced prediabetic rats.

Myocardial infarction (MI) causes extensive cardiomyocyte loss and adverse remodeling, frequently progressing to heart failure. Although stem cell-based therapies are being investigated for cardiac repair, clinical outcomes remain modest. Cardiac atrial appendage stem cells (CASCs) harbor cardiomyogenic potential, making them promising candidates for cardiac regeneration. This proof-of-concept pilot study investigates the feasibility and preliminary therapeutic potential of delivering CASCs within an elastin-like recombinamer (ELR) hydrogel scaffold following MI. MI was induced in rats by permanent ligation of the left anterior descending coronary artery. Immediately after occlusion, CASCs (MI+C), ELR hydrogel (MI+H), or CASCs embedded in ELR hydrogel (MI+C+H) were injected intramyocardially into the peri-infarct region. MI and SHAM-operated animals served as controls. Four weeks post-MI, echocardiography showed a large, non-significant left ventricular ejection fraction improvement in MI+C+H versus MI, with a trend toward reduced end-diastolic volume. MI+C+H significantly improved anterior wall thickness versus MI+H, with favorable trends for MI+C. Wall motion score index showed a similar large, non-significant effect. Transcriptomics suggested the MI+C+H molecular profile reflected complementary contributions of both monotherapies rather than distinct synergistic mechanisms. These preliminary findings support ELR-mediated CASC delivery and suggest potential benefits for preserving cardiac function and limiting adverse remodeling, warranting confirmation in adequately powered studies.

Echocardiography-guided intramyocardial injection (EGI) is a minimally invasive technique for delivering stem cell therapies in preclinical myocardial infarction (MI) models. Compared to traditional open-chest approaches, EGI offers improved clinical translatability, reduced invasiveness, and minimized physiological impact on the animal. While EGI is well established in murine models, its application in rats remains limited due to anatomical and technical challenges. In particular, thinning of the left ventricular anterior wall (LVAW) in infarcted and peri-infarct regions complicates safe and accurate myocardial delivery, as wall thickness can fall below the needle bevel size of commonly used 27 G or 28 G needles, increasing the risk of ventricular perforation or failed delivery. To address this limitation, we optimized a protocol for EGI in rat MI models using 29 G Spinocan needles. The smaller-diameter, longer needle enables precise targeting of thin myocardial tissue, minimizing damage and enhancing injection accuracy, independent of LVAW thickness. This technique is compatible with standard transthoracic echocardiography platforms and eliminates the need for thoracotomy, allowing longitudinal studies in the same animal. Our refined method enables robust, reproducible delivery of therapeutic agents into viable myocardium adjacent to the infarct zone, where regenerative therapies are most effective. By improving safety and targeting precision, this approach increases the translational relevance of preclinical cardiac research and supports the development of standardized protocols across laboratories.

Echocardiography-guided intramyocardial injection (EGI) is a minimally invasive technique for delivering stem cell therapies in preclinical myocardial infarction (MI) models. Compared to traditional open-chest approaches, EGI offers improved clinical translatability, reduced invasiveness, and minimized physiological impact on the animal. While EGI is well established in murine models, its application in rats remains limited due to anatomical and technical challenges. In particular, thinning of the left ventricular anterior wall (LVAW) in infarcted and peri-infarct regions complicates safe and accurate myocardial delivery, as wall thickness can fall below the needle bevel size of commonly used 27 G or 28 G needles, increasing the risk of ventricular perforation or failed delivery. To address this limitation, we optimized a protocol for EGI in rat MI models using 29 G Spinocan needles. The smaller-diameter, longer needle enables precise targeting of thin myocardial tissue, minimizing damage and enhancing injection accuracy, independent of LVAW thickness. This technique is compatible with standard transthoracic echocardiography platforms and eliminates the need for thoracotomy, allowing longitudinal studies in the same animal. Our refined method enables robust, reproducible delivery of therapeutic agents into viable myocardium adjacent to the infarct zone, where regenerative therapies are most effective. By improving safety and targeting precision, this approach increases the translational relevance of preclinical cardiac research and supports the development of standardized protocols across laboratories.