Macrophages of the Cardiorenal Axis and Myocardial Infarction

Mediating Role of Blood Metabolites in the Relationship Between Immune Cell Traits and Heart Failure: A Mendelian Randomization and Mediation Analysis

BACKGROUND

Observational studies have shown a significant association between immune cells and heart failure (HF). Nevertheless, the precise biological mechanisms underlying this association remain unclear.

METHODS

To investigate the causative relationships and underlying mechanisms between immune cell traits and adult HF, 3 main methods of Mendelian randomization were used: 2-sample Mendelian randomization, multivariable Mendelian randomization with controlling for several factors affecting HF, and mediation analysis. Results from the inverse variance-weighted model indicated that genetic predispositions for human leukocyte antigen-type DR (HLA DR) on CD33dim HLA DR+ CD11b+ (odds ratio, 0.967 [95% CI, 0.939-0.996]; P=0.028) may be associated with a reduced risk of HF. Although the association between HF and HLA DR on CD33 dim HLA DR+ CD11b+ did not withstand multiple-testing correction, the Mendelian randomization results (PIVW <0.05) decrease the likelihood that the observational results are due to chance.

RESULTS

Our 2-step mediation analysis demonstrated that genetic predispositions for HLA DR on CD33dim HLA DR+ CD11b+ (odds ratio,1.085 [95% CI, 1.020-1.155]; P=0.010) was associated with increased levels of the metabolite Octadecanedioate, while genetic predispositions for Octadecanedioate levels (odds ratio, 0.917 [95% CI, 0.849-0.991]; P=0.028) was associated with a reduced risk of HF. Moreover, our results also demonstrated that the association between HLA DR on CD33dim HLA DR+ CD11b+ and HF was possibly mediated by Octadecanedioate levels, with a mediation proportion of 21.4% [95% CI, 43.7 -0.998].

CONCLUSIONS

These findings underscore the importance of HLA DR on CD33dim HLA DR+ CD11b+ in the development of HF, with Octadecanedioate levels acting as a possible mediator in this pathway.

Itaconate and citrate releasing polymer attenuates foreign body response in biofabricated cardiac patches

Application of cardiac patches to the heart surface can be undertaken to provide support and facilitate regeneration of the damaged cardiac tissue following ischemic injury. Biomaterial composition is an important consideration in the design of cardiac patch materials as it governs host response to ultimately prevent the undesirable fibrotic response. Here, we investigate a novel patch material, poly (itaconate-co-citrate-co-octanediol) (PICO), in the context of cardiac implantation. Citric acid (CA) and itaconic acid (ITA), the molecular components of PICO, provided a level of protection for cardiac cells during ischemic reperfusion injury in vitro. Biofabricated PICO patches were shown to degrade in accelerated and hydrolytic conditions, with CA and ITA being released upon degradation. Furthermore, the host response to PICO patches after implantation on rat epicardium in vivo was explored and compared to two biocompatible cardiac patch materials, poly (octamethylene (anhydride) citrate) (POMaC) and poly (ethylene glycol) diacrylate (PEGDA). PICO patches resulted in less macrophage infiltration and lower foreign body giant cell reaction compared to the other materials, with corresponding reduction in smooth muscle actin-positive vessel infiltration into the implant region. Overall, this work demonstrates that PICO patches release CA and ITA upon degradation, both of which demonstrate cardioprotective effects on cardiac cells after ischemic injury, and that PICO patches generate a reduced inflammatory response upon implantation to the heart compared to other materials, signifying promise for use in cardiac patch applications.