A Hybrid Biomaterials Platform for Neovascularization in Engineered Human iPSC-derived Cardiac Tissue

Vascularization of ischemic myocardium and implanted engineered cardiac tissue is critical for long-term survival of native cardiomyocytes and integration of hiPSC-derived cardiomyocytes. We are developing a hybrid... [ view full abstract ]

Vascularization of ischemic myocardium and implanted engineered cardiac tissue is critical for long-term survival of native cardiomyocytes and integration of hiPSC-derived cardiomyocytes. We are developing a hybrid biomaterials platform to induce vascularization into engineered human myocardium using alginate microspheres releasing angiogenic growth factors from within implanted engineered tissue. Alginate (1% w/v) is mixed with VEGF, bFGF, and/or sonic hedgehog (SHH) and microspheres formed with co-axial air flow (70 μm diameter). In vitro release kinetics show 80% release within 1 day and continuing for 2 days. Using an in vitro 3D collagen gel platform with embedded microspheres and HUVECs, endothelial cell network number and branching were dose-dependent and peaked at ~1.5-fold above positive control (complete EGM2 medium with unloaded microspheres) for VEGF+bFGF or VEGF+bFGF+SHH where each growth factor was 16-32ng/mL (loading concentration). Validation and synergistic effects are being evaluated in in vitro aortic ring assays. For evaluation of neovascularization in vivo, engineered tissues (1.4 x 1.4 cm) are implanted on the epicardial surface of the heart 4 days after ischemia/reperfusion injury in athymic rats. HiPSC-derived cardiomyocytes (10 x 106 cells) mixed with collagen-1 (1.5 mg/mL), fibrinogen (8 mg/mL), thrombin (200 U/mL), and alginate microspheres (unloaded or containing growth factors) were used to form tissues on the day of implant. Perfusion analysis and 3D vessel reconstruction imaging at 1 week post-implant showed large vessels penetrating the implants. Ongoing work to quantify the vascular tree of the implant will assess effectiveness of angiogenic growth factors to induce neovascularization into engineered cardiac tissue.