BACKGROUND: Cellular repair of myocardial infarcts requires that seeded cells survive in the ischemic infarct bed. A tissue engineering scaffold that provides angiogenic growth factors might accelerate host vascularization. We have developed a novel three-dimensional collagen gel incorporating microspheres that continuously release basic fibroblast growth factor (bFGF) over 7 days as a platform to support engineered cardiac replacement tissues.
METHODS: Gels constructed with 70 μm diameter hydrogel microspheres containing either bFGF (20 μg) or phosphate buffered saline (PBS controls) were cast into lenticular type I collagen gels. Gels were implanted subcutaneously in normal mice and excised 3, 7, or 14 days later. Vascular space was quantified as the area within CD31 (PECAM-1)-positive vascular profiles per high-powered field using image analysis software. Statistical analysis was by two-tailed t tests.
RESULTS: Accelerated neovascularization in the bFGF group was evident on both gross and histologic specimens by 7 and 14 days after implantation (Fig 1A,B) while no reaction was seen in PBS controls (C,D). At 7 days, vascular space in tissue surrounding the bFGF-containing collagen gels (11.8±0.62 %, n=7) was significantly greater than in the PBS-containing controls (0.89±0.39 %, n=7, p <0.0001).
CONCLUSIONS: Incorporating microspheres with timed release of bFGF into collagen gels resulted in a novel scaffold with significantly enhanced host neovascularization. Such a scaffold might improve the survival of seeded cardiac or skeletal myocytes in myocardial infarct areas.

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