VEGF-delivering PEG hydrogels promote vascularization in the porcine subcutaneous space.

For cell therapies, the subcutaneous space is an attractive transplant site due to its large surface area and accessibility for implantation, monitoring, biopsy, and retrieval. However, its poor vascularization has catalyzed research to induce blood vessel formation within the site to enhance cell revascularization and survival. Most studies focus on the subcutaneous space of rodents, which does not recapitulate important anatomical features and vascularization responses of humans. Herein, we evaluate biomaterial-driven vascularization in the porcine subcutaneous space. Additionally, we report the first use of cost-effective fluorescent microspheres to quantify perfusion in the porcine subcutaneous space. We investigate the vascularization-inducing efficacy of vascular endothelial growth factor (VEGF)-delivering synthetic hydrogels based on 4-arm poly(ethylene) glycol macromers with terminal maleimides (PEG-4MAL). We compare three groups: a non-degradable hydrogel with a VEGF-releasing PEG-4MAL gel coating (Core+VEGF gel); an uncoated, non-degradable hydrogel (Core-only); and naïve tissue. After 2 weeks, Core+VEGF gel has significantly higher tissue perfusion, blood vessel area, blood vessel density, and number of vessels compared to both Core-only and naïve tissue. Furthermore, healthy vital signs during surgery and post-procedure metrics demonstrate the safety of hydrogel delivery. We demonstrate that VEGF-delivering synthetic hydrogels induce robust vascularization and perfusion in the porcine subcutaneous space.

Engineering ß Cell Replacement Therapies for Type 1 Diabetes: Biomaterial Advances and Considerations for Macroscale Constructs.

While significant progress has been made in treatments for type 1 diabetes (T1D) based on exogenous insulin, transplantation of insulin-producing cells (islets or stem cell-derived ß cells) remains a promising curative strategy. The current paradigm for T1D cell therapy is clinical islet transplantation (CIT)-the infusion of islets into the liver-although this therapeutic modality comes with its own limitations that deteriorate islet health. Biomaterials can be leveraged to actively address the limitations of CIT, including undesired host inflammatory and immune responses, lack of vascularization, hypoxia, and the absence of native islet extracellular matrix cues. Moreover, in efforts toward a clinically translatable T1D cell therapy, much research now focuses on developing biomaterial platforms at the macroscale, at which implanted platforms can be easily retrieved and monitored. In this review, we discuss how biomaterials have recently been harnessed for macroscale T1D ß cell replacement therapies.