Engineered human myocardium with local release of angiogenic proteins improves vascularization and cardiac function in injured rat hearts

Abstract

Heart regeneration after myocardial infarction requires new cardiomyocytes and a supportive vascular network. Here, we evaluate the efficacy of localized delivery of angiogenic factors from biomaterials within the implanted muscle tissue to guide growth of a more dense, organized, and perfused vascular supply into implanted engineered human cardiac tissue on an ischemia/ reperfusion injured rat heart. We use large, aligned 3-dimensional engineered tissue with cardiomyocytes derived from human induced pluripotent stem cells in a collagen matrix that contains dispersed alginate microspheres as local protein depots. Release of angiogenic growth factors VEGF and bFGF in combination with morphogen sonic hedgehog from the microspheres into the local microenvironment occurs from the epicardial implant site. Analysis of the 3D vascular network in the engineered tissue via Microfil® perfusion and microCT imaging at 30 days shows increased volumetric network density with a wider distribution of vessel diameters, proportionally increased branching and length, and reduced tortuosity. Global heart function is increased in the angiogenic factor-loaded cardiac implants versus sham. These findings demonstrate for the first time the efficacy of a combined remuscularization and revascularization therapy for heart regeneration after myocardial infarction.

Heparin-modified alginate microspheres enhance neovessel formation in hiPSC-derived endothelial cells and heterocellularin vitromodels by controlled release of VEGF

“…As discussed by Ronghua et al [21], the new peak appearing after sulfation at 1690 cm -1 in S-Alg (stretching vibration of the carbonyl groups of -COOH), indicated by the arrow in Figure 1B, is associated to the formation of carboxyl groups (COOH) after dialysis (dialysis buffer pH=6.8). As shown in Figure 1C, the H-Alg spectrum showed the main absorption band of sulfate at 1220 cm −1 , and a newly emerging In comparison to the VEGF release profiles reported for unmodified alginate microspheres in our previous work [30], where we have observed a burst 3-days release of biotinylated VEGF with western blot analysis, the sensitive ELISA assay used in this work allowed us to detect the release of small amounts of VEGF (5-20 ng/mL) in the incubation solutions at longer time points up to 14 days. The release kinetics of H-Alg bulk hydrogels and microspheres showed a more gradual release of VEGF over 14 days compared to the unmodified group, when normalized to total release at 14 days (Figures 2A-B).…”

“…In comparison to the VEGF release profiles reported for unmodified alginate microspheres in our previous work [30], where we have observed a burst 3-days release of biotinylated VEGF with western blot analysis, the sensitive ELISA assay used in this work allowed us to detect the release of small amounts of VEGF (5-20 ng/mL) in the incubation solutions at longer time points up to 14 days. The release kinetics of H-Alg bulk hydrogels and microspheres showed a more gradual release of VEGF over 14 days compared to the unmodified group, when normalized to total release at 14 days (Figures 2A-B).…”

“…In this work we propose an acellular approach to stimulate neovascularization in ischemic tissues that consists of amplifying the native host response by supplying angiogenic growth factors in the local microenvironment to promote new vessel development [12,13]. We and others have previously used alginate hydrogels and microspheres for the release of growth factors, due to the minimal processing, rapid encapsulation of bioactive molecules, and high compatibility with cells and tissues [12][13][14][15][16][17][18][19]. However, immobilized growth factors are only retained in alginate hydrogels by relatively weak ionic interactions, and thus, in the presence of diffusion, relatively short release kinetics of growth factors are obtained from alginate microspheres [20].…”

“…In this work we propose an acellular approach to stimulate neovascularization in ischemic tissues that consists of amplifying the native host response by supplying angiogenic growth factors in the local microenvironment to promote new vessel development [12, 13]. We and others have previously used alginate hydrogels and microspheres for the release of growth factors, due to the minimal processing, rapid encapsulation of bioactive molecules, and high compatibility with cells and tissues [12-19].…”

Engineering Myocardium for Heart Regeneration—Advancements, Considerations, and Future Directions

“…In addition to improving proliferation and maturation of cardiomyocytes in vitro, vascularization is necessary for creating larger cardiac constructs that survive and engraft in vivo. An in situ approach of releasing angiogenic growth factors from CM patches has shown to increase vessel ingrowth and improve overall outcomes in rodent myocardial infarction models compared to non-angiogenic controls (81,82). However, the in vitro approach that adds vascular cells to living cardiac constructs may provide quicker and more robust vascular development for MI repair and will be necessary for developing reconstructive tissues for CHD repair.…”