Infarct-Derived Chondroitin Sulfate Proteoglycans Prevent Sympathetic Reinnervation after Cardiac Ischemia-Reperfusion Injury

Abstract

Sympathetic nerve can regenerate after injury to re-innervate target tissues. Sympathetic regeneration is well documented after chronic cardiac ischemia, so we were surprised that the cardiac infarct remained denervated following ischemia-reperfusion (I-R). We used mice to ask if the lack of sympathetic regeneration into the scar was due to blockade by inhibitory extracellular matrix within the infarct. We found that chondroitin sulfate proteoglycans (CSPGs) were present in the infarct after I-R, but not after chronic ischemia, and that CSPGs caused inhibition of sympathetic axon outgrowth in vitro. Ventricle explants after I-R and chronic ischemia stimulated sympathetic axon outgrowth that was blocked by NGF antibodies. However, growth in I-R co-cultures was asymmetrical, with axons growing toward the heart tissue consistently shorter than axons growing in other directions. Growth toward I-R explants was rescued by adding chondroitinase ABC (ChABC) to the co-cultures, suggesting that I-R infarct-derived CSPGs prevented axon extension. Sympathetic ganglia lacking Protein Tyrosine Phosphatase Sigma (PTPRS) were not inhibited by CSPGs or I-R explants in vitro, suggesting PTPRS is the major CSPG receptor in sympathetic neurons. To test directly if infarct-derived CSPGs prevented cardiac reinnervation, we carried out ischemia-reperfusion in ptprs-/- and ptprs+/- mice. Cardiac infarcts in ptprs-/- mice were hyperinnervated, while infarcts in ptprs+/- littermates were denervated, confirming that CSPGs prevent sympathetic reinnervation of the cardiac scar after I-R. This is the first example of CSPGs preventing sympathetic reinnervation of an autonomic target following injury, and may have important consequences for cardiac function and arrhythmia susceptibility after myocardial infarction.

Sympathetic nerve damage and restoration after ischemia-reperfusion injury as assessed by 11C-hydroxyephedrine

“…Therefore, it is plausible that the reinnervation process starts in the epicardium. Furthermore, blocking of sympathetic nerve regeneration by inhibitory components of the extracellular matrix has recently been reported [8]. The presence of endocardial nontransmural scar tissue may be one factor contributing to the inhibition of further nerve growth towards the distal endocardial portion of the ventricle.…”

“…In animal experimental studies, temporal damage to the cardiac sympathetic nerves after transient ischemia has been shown [6][7][8][9][10][11][12][13]. In humans, several imaging studies using radiolabeled norepinephrine analog tracers have confirmed sympathetic nerve alterations, which are correlated with the area of ischemia in acute coronary syndrome [14].…”

The nervous heart

“…Interestingly, whereas NGF stimulates axon growth, its precursor, proNGF, triggers axon degeneration (Nykjaer et al, 2004) and may be involved in post-MI denervation (Siao et al, 2012). Recently, Gardner and Habecker (2013) also identified chondroitin sulfate proteoglycans, which are present in reperfused infarcts, as responsible for chronic denervation observed in reperfused post-MI hearts.…”

“…It is thought that increases in nerve growth factor (NGF) are primarily responsible for hyperinnervation (Cao et al, 2000a) and blocking NGF prevents nerve sprouting following MI (Hasan et al, 2006). Conversely, sympathetic denervation is also associated with ventricular arrhythmia (Boogers et al, 2010; Fallavollita et al, 2014) and occurs in MI, diabetic neuropathy, and heart failure (Gardner and Habecker, 2013; Gardner et al, 2015; Jacobson et al, 2010; Kimura et al, 2010). Interestingly, whereas NGF stimulates axon growth, its precursor, proNGF, triggers axon degeneration (Nykjaer et al, 2004) and may be involved in post-MI denervation (Siao et al, 2012).…”

Estrogen and female reproductive tract innervation: Cellular and molecular mechanisms of autonomic neuroplasticity

“…Other ECM signals with inhibitory effects for sympathetic axons may also be involved. For example, chondroitin sulfate proteoglycans have been shown recently to prevent sympathetic reinnervation after cardiac ischemia-reperfusion injury (Gardner and Habecker, 2013). It is also unknown whether other estrogen-regulated inhibitory signals, such as cell adhesion molecules, transmembrane signals and diffusible signals anchored to the ECM remain present in the frozen myometrial tissue sections and whether these signals may contribute to the diminished ability of the myometrial substrate to support sympathetic neurite outgrowth in vitro .…”