Post-MI bone marrow cell secretome reprograms macrophages to a reparative M2 phenotype, enhancing cardiac repair
S Ahmed, A Frobert, I Borrego, M N GiraudAbstract
Background/Introduction
After myocardial infarction (MI), an inadequate resolution of inflammation and failure to activate reparative macrophage programs contribute to infarct expansion and adverse left ventricular remodelling. Cell therapy is increasingly thought to confer cardiac repair primarily via paracrine immunomodulation. However, it remains unclear whether a cell donor’s MI history enhances the cell secretome’s potency to induce a macrophage phenotype shift that supports tissue repair.
Purpose
To: determine whether MI-primed donor Bone Marrow cells (BMC) produce a distinct secretome that promotes macrophage reparative polarisation and assess if this translates into improved post-MI cardiac repair in vivo.
Methods
MI was induced in rats by left coronary ligation. BMCs from healthy donors (hBMC) or from donors 2 weeks post-MI (iBMC) were harvested and expanded ex vivo for 2 weeks. The conditioned media (secretomes) were analyzed by LC–MS/MS proteomics. Bone-marrow–derived macrophages were cultured with BMC-conditioned media for 48 h and then assessed by flow cytometry and gene expression profiling of polarization markers. For in vivo, rats 2 weeks post-MI received an epicardial fibrin patch delivering BMCs at the infarct. Cardiac function was evaluated by echocardiography before BMC delivery and 4 weeks after, with change in ejection fraction as the primary outcome. Infarct size was assessed by Masson–Goldner trichrome staining, and immunofluorescence was performed
Results
In vitro, iBMC cultures contained a higher proportion of hematopoietic/myeloid cells (CD45⁺, CD68⁺) and less CD90⁺ cells compared to hBMC, along with greater expression of M2-associated markers (CD206, CD163) and no increase in M1 markers (Fig 1). Proteomic analysis revealed that the iBMC secretome was distinct from hBMC, enriched in myeloid-related, pro-angiogenic and matrix-remodelling factors. Functionally, macrophages exposed to iBMC-conditioned media showed enhanced growth and a shift to a reparative (M2-like) gene expression profile, with upregulation of Arg1, CD163, IL-10 and downregulation of iNOS, CD80, IL-1β. In vivo, rats treated with iBMCs exhibited superior improvement in EF (Fig2) and attenuated adverse remodelling compared to hBMC-treated or untreated controls. Consistently, immunofluorescence of iBMC-treated hearts showed an infarct-zone immune shift with reduced persistence of inflammatory macrophages and an enrichment of CD206⁺ reparative macrophages, indicating that the MI-primed secretome effectively “educates” macrophages toward a healing phenotype in the infarct.
Conclusion(s)
Donor MI history primes BMC composition and secretory profile toward an immunoreparative program that drives reparative macrophage polarization by effectively instructing macrophages towards a pro-healing phenotype, in line with improved post-MI cardiac repair in vivo.