Cold Storage of Hearts from Brain-dead Donors using a Preservation Solution, Supplemented by a Mesenchymal Stem Cell Conditioned Medium Improves Contractile Function of Graft after Heart Transplantation in Rats

Objectives: Heart transplantation is the standard therapy in end-stage heart failure. Presently, heart donation is only possible after brain death (BD). However, BD donors could suffer hemodynamic instability, which may further explain posttransplant graft dysfunction. It has been shown that conditioned medium (CM) from bone marrow derived mesenchymal stem cells significantly protects the myocardium in an ex vivo model of ischemia/reperfusion. Additionally, in vitro data suggest a protection mediated by paracrine activation of the phosphatidylinositol 3 kinase (PI3K) pathway. We assessed the hypothesis that CM when added to a preservation solution (Custodiol) will attenuate in vivo left ventricular (LV) graft dysfunction after transplantation. Additionally, we explore the potential implication of the PI3K pathway.

Methods: Donor rats were either subjected to BD by inflation of subdurally placed balloon catheter or sham operation, and monitored for 5.5h. Then, hearts were arrested and stored for 1 hour in cold Custodiol supplemented with medium vehicle (BD and sham), Custodiol supplemented with CM (BD CM and sham CM), and BD CM+LY294002 (LY, a specific non selective inhibitor of PI3K). Thereafter they were heterotopically transplanted. Posttransplant graft function was assessed in vivo 1.5h after transplantation via a Millar catheter.

Results: In donors, BD was associated with significantly decreased systolic performance and impaired relaxation. After transplantation, systolic function (LV systolic pressure 74 ± 6 vs. 108 ± 2 mm Hg, dP/dt_max 2,070 ± 96 vs. 2,984 ± 146 mm Hg/s at 80 µl, p < 0.05) and diastolic function (dP/dt_min 1,389 ± 50 vs 2681 ± 75 mm Hg/s at 80µl, p < 0.05) were significantly decreased in BD compared with sham. CM resulted in a better systolic functional recovery of grafts in both sham and BD groups compared with the corresponding controls (LV systolic pressure: sham CM 149 ± 10 vs sham 108 ± 2, BD CM 116 ± 6 vs BD 74 ± 6 mm Hg, dP/dt_max: sham CM 5395 ± 457 vs sham 2984 ± 146, BD CM 2965 ± 121 vs BD 2070 ± 96 mm Hg/s, p < 0.05). Addition of LY to the CM significantly attenuated the protection by CM of grafts in BD group (LV systolic pressure BD CM 116 ± 6 vs BD CM LY 84 ± 2 mm Hg at 80 µl, p < 0.05). CM had no effect on diastolic function.

Conclusions: CM added to a preservation solution improves posttransplant cardiac contractility decline associated with BD and IR injury. Our data suggest that this protection is, partly, mediated by paracrine activation of the PI3K pathway.