Optimization and Biological Characterization of Decellularized Adipose Tissue Scaffolds for Soft Tissue Reconstruction
ECM (extracellular matrix) , Decellularization , Biomaterial , Adipose tissue engineering
It would be a great advantage in reconstructive surgery to have an off-the-shelf biomaterial to promote regeneration and volume augmentation following soft tissue damage. With this long-term objective, human adipose tissue (fat) is an abundant and accessible source of extracellular matrix (ECM) for bioscaffold fabrication. The main goal of the current research project was to optimize the established 5-day detergent-free decellularization protocol developed by the Flynn group, by shortening it to a maximum of 3 days, while achieving comparable results in terms of cell and lipid extraction with preservation of the ECM. The effectiveness of the optimized protocol was assessed by examination of the decellularized adipose tissue (DAT) and its characteristic biological properties, including in vitro bioactivity assays with human adipose-derived stem cells (ASCs) to measure adipogenic potential, as well as in vivo testing of scaffold biocompatibility. In the optimized approach, the addition of mechanical processing steps including repeated pressing and centrifugation were shown to enhance cell extraction. Fibrous ultrastructure was observed under scanning electron microscopy (SEM) for the original and optimized protocols. The preservation of collagen fibres was assessed with picro-sirius red staining and confirmed by high hydroxyproline content. Enhanced preservation of glycosaminoglycans (GAGs) was determined for the optimized protocol. Residual DNA content was higher in the DAT scaffolds processed with the optimized protocol, including larger DNA fragments that were not typically observed in the samples treated with the original protocol, which incorporated additional enzymatic treatment stages with DNase, RNase and lipase. However, no residual nuclei were visualized through DAPI staining for both protocols. Enhanced removal of DNA was achieved with electron beam (e-beam) sterilization. E-beam sterilization caused some changes in the fine fibrous structure of the ECM, but did not negatively affect the adipo-conductive potential in vitro. In comparison to the original protocol, DAT produced via the optimized protocol exhibited similar adipo-conductive properties in vitro. The in vivo biocompatibility study over a 16 week period using an immunocompetent Wistar rat model showed promising results. DAT implants produced with the original and optimized protocols promoted adipogenesis and angiogenesis, gradually being remodelled to resemble mature adipose tissue.