Near Complete Repair After Myocardial Infarction in Adult Mice by Altering the Inflammatory Response With Intramyocardial Injection of α-Gal Nanoparticles

Abstract

Background: Neonatal mice, but not older mice, can regenerate their hearts after myocardial-infarction (MI), a process mediated by pro-reparative macrophages. α-Gal nanoparticles applied to skin wounds in adult-mice bind the anti-Gal antibody, activate the complement cascade and generate complement chemotactic peptides that recruit pro-reparative macrophages which are further activated by these nanoparticles. The recruited macrophages decrease wound healing time by ~50%, restore the normal skin structure and prevent fibrosis and scar formation in mice.Objectives: The objective of this study is to determine if α-gal nanoparticles injected into the reperfused myocardium after MI in adult-mice can induce myocardial repair that restores normal structure, similar to that observed in skin injuries.Methods and Results: MI was induced by occluding the mid-portion of the left anterior descending (LAD) coronary artery for 30 min. Immediately following reperfusion, each mouse received two 10 μl injections of 100 μg α-gal nanoparticles in saline into the LAD territory (n = 20), or saline for controls (n = 10). Myocardial infarct size was measured by planimetry following Trichrome staining and macrophage recruitment by hematoxylin-eosin staining. Left ventricular (LV) function was measured by echocardiography. Control mice displayed peak macrophage infiltration at 4-days, whereas treated mice had a delayed peak macrophage infiltration at 7-days. At 28-days, control mice demonstrated large transmural infarcts with extensive scar formation and poor contractile function. In contrast, mice treated with α-gal nanoparticles demonstrated after 28-days a marked reduction in infarct size (~10-fold smaller), restoration of normal myocardium structure and contractile function.Conclusions: Intramyocardial injection of α-gal nanoparticles post-MI in anti-Gal producing adult-mice results in near complete repair of the infarcted territory, with restoration of normal LV structure and contractile function. The mechanism responsible for this benefit likely involves alteration of the usual inflammatory response post-MI, as previously observed with regeneration of injured hearts in adult zebrafish, salamanders and neonatal mice.

The interaction between nanoparticles and immune system: application in the treatment of inflammatory diseases

“…Galili et al utilized α-gal nanoparticles prepared from rabbit red blood cell membranes to recruit pro-reparative macrophages to the infarcted territory in a mouse model of myocardial infarction. After 28 days of treatment, treated mice demonstrated a marked remission in terms of infarct size (~ tenfold smaller), restoration of normal myocardium structure and contractile function comparing with control group [ 44 ]. Such strategy has also been applied to manage diabetic wound healing with satisfying outcomes [ 45 ].…”

New diagnostic and therapeutic strategies for myocardial infarction via nanomaterials

“…After LAD ligation followed by three-day tail vein injection of nanoparticles, given to the CD11b, CD44, and αLβ2-integrin combined on the surface of apoptotic bodies, the nanoparticles had the capability to target cardiac inflammation actively, thus promoting the M2 polarization and improving cardiac functions. Another interesting result came from Galili et al., 116 who used α-Gal nanoparticles that recruited macrophages via the activation of the complement system, whereas the accumulated macrophages showed an M2 phenotype and expressed high levels of VEGF, IL-1α, FGF, and PDGF, all reparative cytokines, thus decreasing the poor fibrosis and improved cardiac functions.…”

Biosynthesis of α-Gal Epitopes (Galα1-3Galβ1-4GlcNAc-R) and Their Unique Potential in Future α-Gal Therapies

“…These observations raised the possibility that injection of α-gal nanoparticles into the post-MI injured myocardium of adult anti-Gal–producing mice may recruit macrophages that are activated to have the capacity of neonatal macrophages for mediating restoration of the normal structure and of contractility in the myocardium without scar formation. Studies in anti-Gal–producing GT-KO mice ( Galili et al, 2021 ) have demonstrated that ischemia in the adult mouse heart due to occlusion of the mid-left descending coronary artery for 30 min, followed by reperfusion, results in fibrosis and scar formation in ∼20% of the left ventricle myocardium including thinning of the ventricular wall (representative example in Figure 10A ). However, injection of α-gal nanoparticles into the injured myocardium immediately after reperfusion decreases the fibrosis to only ∼2% of the left ventricle due to infiltration of pro-reparative macrophages into the injured myocardium and its subsequent repopulation with healthy cardiomyocytes (representative example in Figure 10B ).…”

“…However, injection of α-gal nanoparticles into the injured myocardium immediately after reperfusion decreases the fibrosis to only ∼2% of the left ventricle due to infiltration of pro-reparative macrophages into the injured myocardium and its subsequent repopulation with healthy cardiomyocytes (representative example in Figure 10B ). Thus, the post-MI α-gal nanoparticles treatment resulted in near complete restoration of the normal structure and function of the injured myocardium ( Galili et al, 2021 ).…”

“…Note the thinning of the ventricular wall and the much larger scar tissue in the saline-treated heart vs. the normal ventricular wall thickness and much smaller scar in the α-gal nanoparticle–treated heart. Adapted from Galili et al (2021) .…”