Tricellular Adipose Regeneration Units in pGelMA Hydrogel Synergistically Enhance Fat Graft Survival through Vascularization and ECM Remodeling

Autologous fat transplantation (AFT) remains limited by low graft survival rates due to insufficient vascularization and extracellular matrix (ECM) support. Here, we developed an adipose tissue regeneration unit (ATRU) system combining three key cellular components (adipose-derived stem cells, ADSCs; human umbilical vein endothelial cells, HUVECs; and fibroblasts, FBs) within a porous gelatin methacryloyl (pGelMA) hydrogel microenvironment. Through controlled coculture in microwell plates, this system generated functional microtissues, demonstrating synergistic effects: ADSCs provided adipogenic potential; HUVECs enabled vascular network formation, and FBs facilitated ECM deposition. Comprehensive <i>in vitro</i> characterization confirmed enhanced cell viability, adipogenic differentiation, and collagen production. <i>In vivo</i> implantation in nude mice revealed enhanced performance of ATRU constructs compared to ADSC-only controls, with histological and immunohistochemical analysis showing: (1) a 1.14-fold increase in adipose tissue area, (2) a 1.55-fold increase in the number of CD31⁺ blood vessels per field of view, and (3) substantially elevated type III collagen deposition. The incorporation of pGelMA provided a biocompatible and porous scaffold, facilitating cell viability, nutrient diffusion, and structural integration with the host tissues. These results highlight the capacity of the ATRU strategy to simultaneously address the critical challenges of vascularization, ECM remodeling, and volume retention in fat grafting, offering a promising proof-of-concept platform to guide further preclinical optimization for breast reconstruction and aesthetic augmentation.