T cells as a therapeutic target in an acute myocardial infarction pig model
A Stadtmueller, R Grampp, F Schnitter, F Becker, K Nuriyeva, D Langenhorst, L Metka, N Gladow, U Hofmann, A Frey, N BeyersdorfAbstract
Background
Following myocardial infarction (MI), cardiac wound healing, long-term survival, and cardiac function are frequently impaired. Studies in mice have shown that shifting the balance between Foxp3+ CD25+ regulatory T cells (Treg) and conventional T cells (Tconv) towards the Treg can enhance healing and improve survival. However, it remains currently unclear whether these findings can be translated into a large animal model under clinically relevant conditions.
Purpose
The aim of this project was to evaluate the efficacy of manipulating the Treg/Tconv ratio in a porcine MI model as a key intermediate step before toward clinical translation. To increase the Treg/Tconv ratio we activated Treg over Tconv by injection of a superagonistic anti-CD28 monoclonal antibody (mAb) (CD28-SA), which was efficacious in a murine MI model.
Methods
To induce an MI, the left anterior descending artery (LAD) was assessed via a femoral arterial approach and occluded after the separation of a first diagonal branch with a balloon for 90 minutes, mimicking a common ischemia-reperfusion scenario in humans. Echocardiography of the heart was performed on days 0, 3 and 7. Therapeutic (CD28-SA) or control (MOPC) antibodies were applied on day 3 post MI through i.v. infusion by surgeons blinded to the applied therapy. On day 7, pigs were euthanized and samples from blood, spleen, thymus, mediastinal lymph nodes and the heart were collected for flow cytometric analyses of myeloid cells and lymphocytes.
Results
4 out of 18 animals died due to refractory ventricular fibrillation during the MI. The remaining 14 animals were assigned to 3 treatment groups: NaCl infusion (n=2), control mAb (10 µg/kg, n=6) and CD28-SA (10 µg/kg, n=6). Echocardiographic analyses showed no significant differences between the treatment and the control mAb group, however cardiac function was impaired in MI animals irrespective of the therapeutic group assignment. Immunologically, CD28-SA infusion increased the proportion of CD25+ Foxp3+ Treg among heart-infiltrating CD4+ T cells, but not among CD4+ T cells of mediastinal lymph nodes, spleen or CD4-single positive thymocytes. This increase was accompanied by a reduction in pro-inflammatory TNFα-producing cells among heart-infiltrating myeloid cells. The treatment appeared to shift mRNA expression in the infarcted myocardium towards wound healing and increased the proportion of Ki-67+ Tconv in the peripheral blood. Additionally, immunofluorescence staining showed an accumulation of Treg in the infarcted heart.
Conclusions
CD28-SA treatment induced a marked increase in the Treg population, influenced the myeloid cell compartment and appeared to promote wound healing in the cardiac tissue after MI. Further long-term experiments to evaluate the improvement of cardiac function in pigs after MI are needed to translate this novel therapeutic approach into humans.