The Immune System as a Crucial Determinant of the Fate of Decellularized Cardiovascular Implants

Background: Decellularized cardiovascular implants represent a promising advancement in cardiac tissue engineering, offering potential alternative solutions for cardiovascular replacement therapy. These implants have already demonstrated superior hemocompatibility and durability, with reduced risk of thrombosis in preclinical in vivo and clinical models. Clinical outcomes unfortunately reveal instances of degeneration in decellularized grafts. Immune responses to these implants have been identified as a cause of graft failure, although direct evidence is still lacking. This study delineates innate immune responses to decellularized cardiovascular implants.

Methods: Bone marrow-derived macrophages (BMDMs), aortic endothelial cells (AoECs), and vascular smooth muscle cells (VSMCs) from male Wistar rats were cultured with detergent-based decellularized ovine aortic valve extracellular matrix (davECM). To investigate the interaction between BMDMs and AoECs, BMDM-davECM-conditioned medium was applied to AoECs. Supernatants were analyzed for cytokine secretion, gene expression, and cell surface markers using flow cytometry, ELISA, and RT-PCR. These results were validated in a sheep model, where decellularized aortic conduits were implanted into healthy sheep and analyzed for infiltrating cell populations via immunofluorescence staining of the aortic tissue.

Results: BMDMs and VSMCs migrated toward and co-localized with the davECM within 48 hours. Elevated secretion of IFN-γ, CXCL1, IL-6, and CCL2 was observed at both 24 and 48 hours. Gene analysis revealed significant upregulation of CCL2 and IL-1β, while IL-10 and TGF-β levels remained unchanged. Flow cytometry showed a peak in CCR2 and CD86 expression at 24 hours, which decreased by 48 hours. VSMCs underwent a phenotypic shift from contractile to osteoblastic. At 2 weeks post-implantation, decellularized sheep aortic conduits exhibited substantial infiltration by inflammatory and regenerative cells.

Conclusion: Our study highlights the dynamic interactions between BMDMs, VSMCs, and davECM. The observed gene expression changes and phenotypic shift induced by davECM suggest a complex cellular response that may influence tissue remodeling, either facilitating it or exacerbating degeneration. These findings indicate that immune cells are crucial in determining the fate of decellularized heart valves through their interactions with vascular endothelial and interstitial cells.

Publikationsverlauf

Artikel online veröffentlicht:
11. Februar 2025