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. 2022 Dec 1;323(6):H1365-H1375.
doi: 10.1152/ajpheart.00580.2022. Epub 2022 Nov 11.

Remote ischemic conditioning in Ossabaw minipigs induces the release of humoral cardioprotective triggers, but the myocardium does not respond with reduced infarct size

Affiliations

Remote ischemic conditioning in Ossabaw minipigs induces the release of humoral cardioprotective triggers, but the myocardium does not respond with reduced infarct size

Helmut Raphael Lieder et al. Am J Physiol Heart Circ Physiol. .

Abstract

Ischemic preconditioning (IPC; brief cycles of coronary occlusion/reperfusion) is operative in all species tested so far and reduces infarct size through the release of trigger molecules and activation of signal transducer and activator of transcription (STAT)3 in pigs. We have recently demonstrated that IPC failed to protect Ossabaw minipigs, which had a genetic predisposition to, but not yet established a metabolic syndrome, from infarction and did not activate STAT3. We now subjected Ossabaw minipigs to remote ischemic conditioning (RIC; 4 × 5 min/5 min bilateral hindlimb ischemia-reperfusion) and analyzed the release of cardioprotective triggers into the circulation with the aim to distinguish whether IPC failed to stimulate trigger release or to activate intracellular signaling cascades upstream of STAT3. RIC or a placebo protocol, respectively, was induced in anesthetized pigs before 60 min/180 min coronary occlusion/reperfusion. Plasma, prepared from Ossabaw minipigs after RIC or placebo, was infused into isolated rat hearts subjected to 30 min/120 min global ischemia-reperfusion. In the Ossabaw minipigs, RIC did not reduce infarct size (49.5 ± 12.1 vs. 56.0 ± 11.8% of area at risk with placebo), and STAT3 was not activated. In isolated rat hearts, infusion of RIC plasma reduced infarct size (19.7 ± 6.7 vs. 33.2 ± 5.5% of ventricular mass with placebo) and activated STAT3. Pretreatment of rat hearts with the STAT3 inhibitor stattic abrogated such infarct size reduction and STAT3 activation. In conclusion, Ossabaw minipigs release cardioprotective triggers in response to RIC into the circulation, and lack of cardioprotection is attributed to myocardial nonresponsiveness.NEW & NOTEWORTHY Ischemic conditioning reduces myocardial infarct size in all species tested so far. In the present study, we used Ossabaw minipigs that had a genetic predisposition to, but not yet established a metabolic syndrome. In these pigs, remote ischemic conditioning (RIC) induced the release of cardioprotective triggers but did not reduce infarct size. Transfer of their plasma, however, reduced infarct size in isolated recipient rat hearts, along with signal transducer and activator of transcription (STAT)3 activation.

Keywords: Ossabaw minipig; cardioprotection; ischemia-reperfusion; myocardial infarction; remote ischemic conditioning.

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Conflict of interest statement

Michael Sturek is cofounder and Chief Scientific Officer of CorVus Biomedical, LLC, which produces Ossabaw minipigs. None of the other authors has any conflicts of interest, financial or otherwise, to disclose.

Petra Kleinbongard is an editor of American Journal of Physiology-Heart and Circulatory Physiology and was not involved and did not have access to information regarding the peer-review process or final disposition of this article. An alternate editor oversaw the peer-review and decision-making process for this article.

Figures

None
Graphical abstract
Figure 1.
Figure 1.
Lack of cardioprotection in Ossabaw minipigs. Ossabaw minipigs were subjected to remote ischemic conditioning (RIC) or placebo before 60 min coronary occlusion and 180 min reperfusion. Data are presented as means ± SD. Red circles, female; blue circles, castrated male Ossabaw minipigs; open symbols, placebo; closed symbols, RIC protocol.
Figure 2.
Figure 2.
Humoral transfer of remote ischemic conditioning´s (RIC) cardioprotection through plasma from Ossabaw minipigs with RIC to isolated perfused recipient rat hearts despite nonresponsiveness of the pig’s myocardium to cardioprotection. Isolated perfused rat hearts were subjected to 30 min global ischemia and 120 min reperfusion (GI/R) without or with blockade of signal transducer and activator of transcription (STAT)3 by stattic and infusion of plasma taken from Ossabaw minipigs subjected to a placebo or RIC protocol. Red circles, data obtained with plasma from female; blue circles, data obtained with plasma from castrated male Ossabaw minipigs; open symbols, placebo; closed symbols, RIC protocol. Data are presented as means ± SD. *P < 0.001 vs. all other groups, respectively; two-way analysis of variance with Fisher’s least significant differences post hoc tests.
Figure 3.
Figure 3.
A: remote ischemic conditioning (RIC) does not activate the signal transducer and activator of transcription (STAT)3tyr705 in the Ossabaw minipig’s myocardium. STAT3tyr705 phosphorylation (p-STAT3) was analyzed in myocardial biopsies taken at baseline, during ischemia and at early reperfusion, respectively, from Ossabaw minipigs which had been subjected to a RIC (females/castrated males, n = 5/6) or to a placebo (females/castrated males, n = 6/5) protocol before ischemia-reperfusion by 60 min coronary occlusion and 180 min. Continuous lines indicate samples taken from one individual Ossabaw minipig with RIC protocol, respectively. Dashed lines indicate samples taken from one individual Ossabaw minipig with placebo protocol. Red circles, female; blue circles, castrated male Ossabaw minipigs. Data are presented as means ± SD. I55, 55 min ischemia; R10, 10 min reperfusion. *P < 0.0001 vs. baseline; #P < 0.001 vs. I55; †P = 0.0183 vs. baseline. B: infusion of plasma from Ossabaw minipigs subjected to RIC increases the phosphorylation of STAT3tyr705 in isolated perfused rat hearts in comparison to infusion of plasma from pigs with placebo protocol. *P < 0.01 vs. placebo plasma+global ischemia-reperfusion (GI/R), one-way analysis of variance with Fisher’s least significant post hoc tests. C: pretreatment of isolated perfused rat hearts with the STAT3 inhibitor stattic abrogates the increase in STAT3tyr705 phosphorylation induced by infusion of plasma from Ossabaw minipigs with RIC. Total STAT3 signals are normalized to the aggregate fluorescence signal on the membrane and displayed in the boxes below the x-axes of A, B, and C, respectively.

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