Human Decellularized Adipose Tissue Hydrogels as a Delivery Platform to Enhance Human Endothelial Colony-Forming Cell Retention and Vascular Regeneration
Cellular therapies harnessing the potential of endothelial colony-forming cells (ECFCs) for therapeutic revascularization in patients with critical limb ischemia (CLI) have garnered much interest. However, limited cell persistence following intramuscular injection into ischemic tissues has prompted the development of biomaterials as cell-delivery platforms to support cell survival and enhance therapeutic outcomes. This study explored the use of hydrogels derived from human decellularized adipose tissue (DAT) as a cell-instructive platform for ECFC delivery. In vitro studies confirmed high initial ECFC viability at 1 day following encapsulation in the DAT hydrogels but revealed that cell viability and proliferation were reduced over time in culture as compared to ECFCs cultured on tissue culture polystyrene (TCP). However, the ECFCs cultured within the DAT hydrogels showed similar ECFC cell surface marker expression patterns compared to ECFCs cultured on TCP after 6 days in culture, supporting that their phenotype was maintained. Subsequent testing focused on comparing a low (2.4 × 105 cells) and high (1 × 106 cells) dose of ECFCs delivered in either saline or within DAT hydrogels in a femoral artery ligation-induced CLI (FAL-CLI) model in NOD/SCID mice over 35 days. Bioluminescence imaging results showed that the low dose of ECFCs delivered in DAT hydrogels demonstrated enhanced retention on days 14, 21, and 28 compared to delivery in saline. Despite this finding, there were no observed improvements in hindlimb perfusion between delivery strategies, which may be related to the robust collateral vessel formation observed in this model with a µCT-based angiography method. Overall, this work supports that DAT hydrogels can enhance localized ECFC retention following intramuscular injection in mice with femoral artery ligation but emphasizes that enhanced retention may be insufficient for improving functional vascular regeneration.