Induction of scaffold angiogenesis by recipient vasculature precision micropuncture

The success of engineered tissues continues to be limited by time to vascularization and perfusion. Here, we studied the effects of precision injury to a recipient macrovasculature in promoting neovessel formation in an adjacently placed scaffold. Segmental 60 μm diameter micropunctures (MP) were created in the recipient rat femoral artery and vein followed by coverage with a simple collagen scaffold. Scaffolds were harvested at 24, 48, 72, and 96 h post-implantation for detailed analysis. Those placed on top of an MP segment showed an earlier and more robust cellular infiltration, including both endothelial cells (CD31) and macrophages (F4/80), compared to internal non-micropunctured control limbs (p < 0.05). At the 96-hour timepoint, MP scaffolds demonstrated an increase in physiologic perfusion (p < 0.003) and a 2.5-fold increase in capillary network formation (p < 0.001). These were attributed to an overall upsurge in small vessel quantity. Furthermore, MP positioned scaffolds demonstrated significant increases in many modulators of angiogenesis, including VEGFR2 and Tie-2 despite a decrease in HIF-1α at all timepoints. This study highlights a novel microsurgical approach that can be used to rapidly vascularize or inosculate contiguously placed scaffolds and grafts. Thereby, offering an easily translatable route towards the creation of thicker and more clinically relevant engineered tissues.

Targeted Ablation Using Laser Nanosurgery

Laser-mediated dissection methods have been used for many years to micro-irradiate biological samples, but recent technological progress has rendered this technique more precise, powerful, and easy to use. Today pulsed lasers can be operated with diffraction limited, sub-micrometer precision to ablate intracellular structures. Here, we discuss laser nanosurgery setups and the instrumentation in our laboratory. We describe how to use this technique to ablate cytoskeletal elements in living cells. We also show how this technique can be used in multicellular organisms, to micropuncture and/or ablate cells of interest and finally how to monitor a successful laser nanosurgery.