Adenosine Production by Biomaterial‐Supported Mesenchymal Stromal Cells Reduces the Innate Inflammatory Response in Myocardial Ischemia/Reperfusion Injury

Abstract

BackgroundDuring myocardial ischemia/reperfusion (MI/R) injury, there is extensive release of immunogenic metabolites that activate cells of the innate immune system. These include ATP and AMP, which upregulate chemotaxis, migration, and effector function of early infiltrating inflammatory cells. These cells subsequently drive further tissue devitalization. Mesenchymal stromal cells (MSCs) are a potential treatment modality for MI/R because of their powerful anti‐inflammatory capabilities; however, the manner in which they regulate the acute inflammatory milieu requires further elucidation. CD73, an ecto‐5′‐nucleotidase, may be critical in regulating inflammation by converting pro‐inflammatory AMP to anti‐inflammatory adenosine. We hypothesized that MSC‐mediated conversion of AMP into adenosine reduces inflammation in early MI/R, favoring a micro‐environment that attenuates excessive innate immune cell activation and facilitates earlier cardiac recovery.Methods and ResultsAdult rats were subjected to 30 minutes of MI/R injury. MSCs were encapsulated within a hydrogel vehicle and implanted onto the myocardium. A subset of MSCs were pretreated with the CD73 inhibitor, α,β‐methylene adenosine diphosphate, before implantation. Using liquid chromatography/mass spectrometry, we found that MSCs increase myocardial adenosine availability following injury via CD73 activity. MSCs also reduce innate immune cell infiltration as measured by flow cytometry, and hydrogen peroxide formation as measured by Amplex Red assay. These effects were dependent on MSC‐mediated CD73 activity. Finally, through echocardiography we found that CD73 activity on MSCs was critical to optimal protection of cardiac function following MI/R injury.Conclusions MSC‐mediated conversion of AMP to adenosine by CD73 exerts a powerful anti‐inflammatory effect critical for cardiac recovery following MI/R injury.

Adenosine from a biologic source regulates neutrophil extracellular traps (NETs)

“…ADO exerts anti‐inflammatory effects on neutrophils and other immune cells, inhibiting migration, priming, and inflammatory mediator production . We investigated whether exogenous ADO, as well as the stable ADO analogue NECA, can reduce NETs in freshly isolated human neutrophils.…”

“…C). Ecto‐5′‐nuclotidase (CD73) converts extracellular adenosine monophosphate (AMP) into ADO, and can be blocked with the irreversible inhibitor APCP . The conditioned media of cultured MSCs supplemented with CD73 substrate AMP had increased ADO (Fig.…”

“…Previously our lab has utilized the immune‐ and purinergic‐modulatory abilities of MSCs to alter the innate immune response in response to myocardial ischemia . MSC delivered to the cardiac epicardium increased myocardial ADO levels, reducing inflammation and ultimately improving cardiac function . In tissues, purines are rapidly metabolized and local concentrations can vary considerably.…”

“…This has made pharmacologic attempts to augment ADO levels largely unsuccessful and may be an argument in favor of cell‐based therapy. By delivering MSCs to the site of injury, they may be more effective at modulating and maintaining the purinergic environment than a systemically administered drug …”

“…Neutrophil activation is tightly regulated in the bone marrow where mesenchymal stromal cells (MSCs) set up an anti‐inflammatory bone marrow niche and have a strong anti‐inflammatory effect on cells of the innate and adaptive immune systems . MSCs release chemokines and exosomes to effect immune cell activation, but may also influence surrounding cells by modulating extracellular purine balance . ATP is a ubiquitous nucleotide necessary for almost all forms of life on earth and thus is sensed by many immune and vascular cells as indicators of tissue health, energetic state, and homeostasis .…”