Controlled Angiogenesis in the Heart by Cell-Based Expression of Specific Vascular Endothelial Growth Factor Levels

Abstract

Vascular endothelial growth factor (VEGF) can induce normal angiogenesis or the growth of angioma-like vascular tumors depending on the amount secreted by each producing cell because it remains localized in the microenvironment. In order to control the distribution of VEGF expression levels in vivo, we recently developed a high-throughput fluorescence-activated cell sorting (FACS)-based technique to rapidly purify transduced progenitors that homogeneously express a specific VEGF dose from a heterogeneous primary population. Here we tested the hypothesis that cell-based delivery of a controlled VEGF level could induce normal angiogenesis in the heart, while preventing the development of angiomas. Freshly isolated human adipose tissue–derived stem cells (ASC) were transduced with retroviral vectors expressing either rat VEGF linked to a FACS-quantifiable cell-surface marker (a truncated form of CD8) or CD8 alone as control (CTR). VEGF-expressing cells were FACS-purified to generate populations producing either a specific VEGF level (SPEC) or uncontrolled heterogeneous levels (ALL). Fifteen nude rats underwent intramyocardial injection of 107 cells. Histology was performed after 4 weeks. Both the SPEC and ALL cells produced a similar total amount of VEGF, and both cell types induced a 50%–60% increase in both total and perfused vessel density compared to CTR cells, despite very limited stable engraftment. However, homogeneous VEGF expression by SPEC cells induced only normal and stable angiogenesis. Conversely, heterogeneous expression of a similar total amount by the ALL cells caused the growth of numerous angioma-like structures. These results suggest that controlled VEGF delivery by FACS-purified ASC may be a promising strategy to achieve safe therapeutic angiogenesis in the heart. Melly and colleagues show that controlled, cell-based delivery of Vascular Endothelial Growth Factor (VEGF) results in safe and stable angiogenesis in mouse hearts. Adipose tissue stem cell populations expressing either homogeneous or heterogeneous levels of retrovirally delivered VEGF were injected into nude mouse hearts. While both cell populations produced similar VEGF amounts and led to increased total and perfused vessel density, cells expressing VEGF heterogeneously resulted in the growth of numerous angioma-like structures not seen in hearts injected with cells expressing homogeneous VEGF levels.