Controlled Hydrogen Peroxide Release Induces Angiogenesis

Regenerative engineering is an exciting field that combines expertise from materials science, developmental biology, and stem cell science to achieve complex tissue repair. While many advances have been made in this field over the past quarter-century, engineered solutions capable of achieving higher-order tissue regeneration have yet to be translated to the clinic. Nowhere is this more apparent than in bone regeneration for which commercially available solutions improve small fracture healing but are sub-optimal for the large volume repair necessary for non-union bone defects due to traumatic injury or tumor removal. One reason for this bottleneck is that most technologies focus on the use of polymeric scaffolds loaded with proteinaceous growth factors which have significant drawbacks including their cost, fragility, poor processability, potential immunogenicity, and high dosage requirements. Additionally, most current models solely focus on the regeneration of osteoblasts and fail to recognize the importance of facilitating vascular network development which is imperative for new bone tissue to thrive. An alternative to protein growth factors are simple signaling molecules which are ions, redox reagents, and gases that have been found to possess potent bioactivity. Specifically, calcium and phosphate ions have been found to induce osteogenesis in mesenchymal stem cells (MSCs) and hydrogen peroxide has been found to induce angiogenesis in endothelial progenitor cells (EPCs). It was hypothesized that controllably delivering hydrogen peroxide can allow for the regeneration of high-quality vasculature which can be leveraged in the future to facilitate complex bone tissue repair.

To controllably deliver hydrogen peroxide, we evaluated the release profiles of several different peroxide generating molecules over the course of 7 days. EPCs were then exposed to a gradient of these molecules to determine their angioinductive potential. At selected time points, Von Willebrand Factor (vWF) fluorescent staining was conducted and assessed via confocal microscopy and flow cytometry to determine if the EPCs were differentiating down the endothelial lineage. Cell viability and proliferation were measured using commercial colorimetric and fluorometric assays. This study uncovered the therapeutic window where hydrogen peroxide can induce angiogenesis in EPCs.