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The lack of vascularization within tissue-engineered constructs remains the primary cause of construct failure following implantation. Porous constructs have been successful in allowing for vessel infiltration without requiring extensive matrix degradation. We hypothesized that the rate and maturity of infiltrating vessels could be enhanced by complementing the open pore structure with the added delivery of DNA encoding for angiogenic growth factors. Both 100 and 60 μm porous and non-porous hyaluronic acid hydrogels loaded with pro-angiogenic (pVEGF) or reporter (pGFPluc) plasmid nanoparticles were used to study the effects of pore size and DNA delivery on angiogenesis in a mouse subcutaneous implant model. GFP-expressing transfected cells were found inside all control hydrogels over the course of the study, although transfection levels peaked by week 3 for 100 and 60 μm porous hydrogels. Transfection in non-porous hydrogels continued to increase over time corresponding with continued surface degradation. pVEGF transfection levels were not high enough to enhance angiogenesis by increasing vessel density, maturity, or size, although by 6 weeks for all pore size hydrogels more hydrogel implants were positive for vascularization when pVEGF polyplexes were incorporated compared to control hydrogels. Pore size was found to be the dominant factor in determining the angiogenic response with 60 μm porous hydrogels having more vessels/area present than 100 μm porous hydrogels at the initial onset of angiogenesis at 3 weeks. The results of this study show promise for the use of polyplex loaded porous hydrogels to transfect infiltrating cells in vivo and guide tissue regeneration and repair.

Talar Tokatlian, Cynthia Cam, Tatiana Segura

Tokatlian T, Cam C, Segura T