Fluorescence imaging preparation methods for tissue scaffolds implanted into a green fluorescent protein porcine model.

Green fluorescent protein (GFP) animal models have become increasingly popular due to their potential to enhance in vivo imaging and their application to many fields of study. We have developed a technique to observe host tissue integration into scaffolds using GFP expressing swine and fluorescence imaging. Current fluorescence imaging preparation methods cannot be translated to a full GFP animal model due to several challenges and limitations that are investigated here. We have implanted tissue scaffolds into GFP expressing swine and have prepared explanted scaffolds for fluorescence imaging using four different methods including formalin fixation and paraffin embedding, vapor fixation, freshly prepared paraformaldehyde fixation, and fresh frozen tissue. Explanted scaffolds and tissue were imaged using confocal microscopy with spectral separation to evaluate the GFP animal model for visualization of host tissue integration into explanted scaffolds. All methods except fresh frozen tissue induced autofluorescence of the scaffold, preventing visualization of detail between host tissue and scaffold fibers. Fresh frozen tissue preparation allowed for the most reliable visualization of fluorescent host tissue integration into non-fluorescent scaffolds. It was concluded that fresh frozen tissue preparation is the best method for fluorescence imaging preparation when using scaffolds implanted into GFP whole animal models.