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Background: Adipose tissue engineering plays a key role in the reconstruction of soft-tissue defects. The acellular adipose matrix (AAM) is a promising biomaterial for the construction of engineered adipose tissue. However, AAM lacks sufficient adipoinduction potency because of the abundant loss of matrix-bound adipokines during decellularization., Methods: An adipose-derived extracellular matrix collagen scaffold, "adipose collagen fragment" (ACF), was prepared using a novel mechanical method that provides sustained release of adipokines. Here, the authors used label-free proteomics methods to detect the protein components in AAM and ACF. In vivo, ACF was incorporated into AAM or acellular dermal matrix and implanted into nude mice to evaluate adipogenesis. Neoadipocytes, neovessels, and corresponding gene expression were evaluated. The effects of ACF on adipogenic differentiation of human adipose-derived stem cells and tube formation by human umbilical vein endothelial cells were tested in vitro., Results: Proteomics analysis showed that ACF contains diverse adipogenic and angiogenic proteins. ACF can release diverse adipokines and induce highly vascularized, mature adipose tissue in AAM, and even in nonadipogenic acellular dermal matrix. Higher expression of adipogenic markers peroxisome proliferator-activated receptor gamma and CCAAT/enhancer-binding protein alpha and greater numbers of tubule structures were observed in ACF-treated groups in vitro., Conclusion: The combination of ACF and AAM could serve as a novel and promising strategy to construct mature, vascularized adipose tissue for soft-tissue reconstruction., Clinical Relevance Statement: The combined use of AAM and ACF has been proven to induce a highly vascularized, mature, engineered adipose tissue in the nude mouse model, which may serve as a promising strategy for soft-tissue reconstruction., (Copyright © 2023 by the American Society of Plastic Surgeons.)

Extracellular matrix (ECM)-mimicking biomaterials are considered effective tissue-engineered scaffolds for regenerative medicine because of their biocompatibility, biodegradability, and bioactivity. ECM-mimicking biomaterials preserve natural microstructures and matrix-related bioactive components and undergo continuous matrix remodeling upon transplantation. The interaction between host immune cells and transplanted ECM-mimicking biomaterials has attracted considerable attention in recent years. Transplantation of biomaterials may initiate injuries and early pro-inflammation reactions characterized by infiltration of neutrophils and M1 macrophages. Pro-inflammation reactions may lead to degradation of the transplanted biomaterial and drive the matrix into a fetal-like state. ECM degradation leads to the release of matrix-related bioactive components that act as signals for cell migration, proliferation, and differentiation. In late stages, pro-inflammatory cells fade away, and anti-inflammatory cells emerge, which involves macrophage polarization to the M2 phenotype and leukocyte activation to T helper 2 (Th2) cells. These anti-inflammatory cells interact with each other to facilitate matrix deposition and tissue reconstruction. Deposited ECM molecules serve as vital components of the mature tissue and influence tissue homeostasis. However, dysregulation of matrix remodeling results in several pathological conditions, such as aggressive inflammation, difficult healing, and non-functional fibrosis. In this review, we summarize the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. STATEMENT OF SIGNIFICANCE: Extracellular matrix (ECM)-mimicking biomaterials are effectively used as scaffolds in tissue engineering and regenerative medicine. However, dysregulation of matrix remodeling can cause various pathological conditions. Here, the review describes the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. We believe that understanding host immune responses to matrix remodeling of transplanted biomaterials is important for directing effective tissue regeneration of ECM-mimicking biomaterials. Considering the close relationship between immune response and matrix remodeling results, we highlight the need for studies of the effects of clinical characteristics on matrix remodeling of transplanted biomaterials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (Copyright © 2022. Published by Elsevier Ltd.)

Decellularized adipose tissue (DAT) represents a promising scaffold for adipose tissue engineering. However, the unique and prolonged lipid removal process required for adipose tissue can damage extracellular matrix (ECM) constituents. Moreover, inadequate vascularization limits the recellularization of DAT in vivo. We proposed a neo-mechanical protocol for rapidly breaking adipocytes and removing lipid content from adipose tissue. The lipid-depleted adipose tissue was then subjected to a fast and mild decellularization to fabricate high-quality DAT (M-DAT). Adipose liquid extract (ALE) derived from this mechanical process was collected and incorporated into M-DAT to further optimize in vivo recellularization. Ordinary DAT was fabricated and served as a control. This developed strategy was evaluated based on decellularization efficiency, ECM quality, and recellularization efficiency. Angiogenic factor components and angiogenic potential of ALE were evaluated in vivo and in vitro. M-DAT achieved the same decellularization efficiency, but exhibited better retention of ECM components and recellularization, compared with those with ordinary DAT. Protein quantification revealed considerable levels of angiogenic factors (basic fibroblast growth factor, epidermal growth factor, transforming growth factor-β1, and vascular endothelial growth factor) in ALE. ALE promoted tube formation in vitro and induced intense angiogenesis in M-DAT in vivo; furthermore, higher expression of the adipogenic factor PPARγ and greater numbers of adipocytes were evident following ALE treatment, compared with those in the M-DAT group. Mechanical processing of adipose tissue led to the production of high-quality M-DAT and angiogenic factor-enriched ALE. The combination of ALE and M-DAT could be a promising strategy for engineered adipose tissue construction., (© 2018 by the Wound Healing Society.)

Tissue engineering chamber technique can be used to generate engineered adipose tissue, showing the potential for the reconstruction of soft tissue defects. However, the consequent foreign body reaction induced by the exogenous chamber implantation causes thick capsule formation on the surface of the adipose flap following capsule contracture, which may limit the internal tissue expansion. The nanotopographical property and architecture of nanofibrous scaffold may serve as a promising method for minimizing the foreign body reaction. Accordingly, electrospinning porous polycaprolactone (PCL) nanofibrous mesh, a biocompatible synthetic polymer, was attached to the internal surface of the chamber for the reducing local foreign body reaction. Adipose flap volume, level of inflammation, collagen quantification, capsule thickness, and adipose tissue-specific gene expression in chamber after implantation were evaluated at different time points. The in vivo study revealed that the engineered adipose flaps in the PCL group had a structure similar to that in the controls and normal adipose tissue structure but with a larger flap volume. Interleukin (IL)-1β, IL-6, and transforming growth factor-β expression decreased significantly in the PCL group compared with the control. Moreover, the control group had much more collagen deposition and thicker capsule than that observed in the PCL group. These results indicate that the unique nanotopographical effect of electrospinning PCL nanofiber can reduce foreign body reaction in a tissue engineering chamber, which maybe a promising new method for generating a larger volume of mature, vascularized, and stable adipose tissue., Competing Interests: The authors report no conflicts of interest in this work.

Chitosan is a promising natural biomaterial for biological application; however, the weak mechanical performance of pristine chitosan limits its further utilization in hard tissue (such as cartilage) engineering. In this study, a chitosan-based 3D printing bioink with suitable mechanical properties was developed as 3D bioprinting ink for chondrocyte support. Chitosan was first modified by ethylenediaminetetraacetic acid (EDTA) to provide more carboxyl groups followed by physical crosslinking with calcium to increase the hydrogel strength. Dynamic mechanical analysis was carried out to evaluate viscoelastic properties with the addition of modified chitosan. A bioink with a combination of modified and pristine chitosan was formulated for scaffold fabrication via 3D bioprinting technique. Furthermore, cell viability, cell proliferation, and expression of chondrogenic markers were evaluated in vitro in chondrocytes loaded on the bioink. The novel bioink exhibited a favorable mechanical property and promoted cell attachment and chondrogenic gene expression in chondrocytes. Based on these results, we can conclude that the presented bioink could qualify for use in 3D bioprinting in cartilage tissue engineering. [ABSTRACT FROM AUTHOR]

Adipose stem cells have prominent implications in tissue regeneration due to their abundance and relative ease of harvest from adipose tissue and their abilities to differentiate into mature cells of various tissue lineages and secrete various growth cytokines. Development of tissue engineering techniques in combination with various carrier scaffolds and adipose stem cells offers great potential in overcoming the existing limitations constraining classical approaches used in plastic and reconstructive surgery. However, as most tissue engineering techniques are new and highly experimental, there are still many practical challenges that must be overcome before laboratory research can lead to large-scale clinical applications. Tissue engineering is currently a growing field of medical research; in this review, we will discuss the progress in research on biomaterials and scaffolds for tissue engineering applications using adipose stem cells. [ABSTRACT FROM AUTHOR]