Co-delivery of human adipose-derived stromal cells and endothelial colony-forming cells in cell-assembled decellularized adipose tissue scaffolds for applications in soft tissue regeneration

Cellular therapies involving the co-delivery of cells with complementary pro-regenerative functionality hold promise as a strategy to promote soft tissue augmentation and regeneration. In particular, the co-delivery of adipose-derived stromal cells (ASCs) and endothelial colony-forming cells (ECFCs) has shown promise for regenerating stable blood vessels in vivo. The current study developed "cell-assembled" scaffolds for co-delivering human ASCs and ECFCs within a supportive decellularized adipose tissue (DAT) matrix, with the objective of enhancing their localized retention and augmenting their capacity to stimulate adipose tissue regeneration. Human ASCs and ECFCs were seeded separately onto human-derived DAT microcarriers under cell-type specific conditions. The cell-seeded microcarriers were then combined and cultured for 8 days under conditions that promoted matrix remodeling to fuse the microcarriers into 3D engineered tissues containing ASCs+ECFCs, ASCs alone, or ECFCs alone. Co-culture with ECFCs within the scaffolds was shown to modulate ASC pro-angiogenic gene expression, with some ECFCs forming tubule-like structures in vitro in both the ASC+ECFC and ECFC alone groups. In vivo bioluminescence imaging using a dual luciferase reporter system showed that co-delivery with ASCs enhanced ECFC retention following subcutaneous implantation in athymic nu/nu mice, but co-delivery did not alter the localized retention of viable ASCs. Interestingly, while immunofluorescence staining for CD31 and microcomputed tomography angiography indicated that vascular regeneration was similar in the cell-assembled scaffolds containing ASC+ECFCs, ASCs alone, and ECFCs alone, histological staining revealed that extensive regions of the ECFC alone scaffolds had remodelled into adipose tissue at 29 days post-implantation. STATEMENT OF SIGNIFICANCE: Cellular therapies involving the co-delivery of complementary pro-regenerative cell types hold promise as a strategy to promote soft tissue regeneration. In particular, the co-delivery of adipose-derived stromal cells (ASCs) and endothelial colony forming cells (ECFCs) may enhance blood vessel regeneration in vivo, as well as promote ASC engraftment and adipogenic differentiation. The current study developed a modular bottom-up fabrication approach for generating "cell-assembled" scaffolds incorporating both human ASCs and ECFCs dispersed throughout a supportive human decellularized adipose tissue (DAT) matrix, which were compared to scaffolds incorporating ASCs alone or ECFCs alone. Co-delivery modulated ASC pro-angiogenic gene expression in vitro and enhanced viable ECFC retention in vivo, but interestingly, in vivo adipogenesis was augmented in the cell-assembled scaffolds incorporating ECFCs alone.