Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Innovative applications of acellular adipose matrix derived film in skin soft tissue expansion

BACKGROUND

Skin dilation generates "extra" skin tissue through mechanical traction, but its effectiveness is limited by the proliferation capacity of keratinocytes, fibroblasts and the level of angiogenesis. Cutaneous application of drug and subcutaneous injection are common interventions to promote skin dilation, but they have defects such as uneven drug distribution, high risk of infection and single targeting. Although Acellular adipose matrix (AAM) has the potential to promote cell proliferation and angiogenesis, its hydrogel/powder dosage forms still need frequent injection, which limits clinical application.

RESULTS

In this study, Acellular adipose matrix derived film (AAF) was successfully developed, and a flexible film was formed by acellular - lyophilized - enzymolysis - self-assembly process. In vitro experiments confirmed that AAF significantly promoted the activity of Human Immortalized Epidermal Cells (HaCaTs), Normal Skin Fibroblasts (NFbs) and Human Umbilical Endothelial Cells (HUVECs); It was also found that AAF can induce adipose mesenchymal stem cells (ASCs) to differentiate into adipocytes and promote subcutaneous fat regeneration. In vivo, the rat model showed that AAF wrapping expander could effectively improve the skin expansion efficiency, promote the skin thickness increase in the expanded area, and the density of new blood vessels was significantly increased compared with the comparative group, and there was no complication such as infection or skin collapse. It was found for the first time that AAF successfully formed new adipose tissue in the subcutaneous area.

CONCLUSION

AAF innovatively integrates the bionic structure of extracellular matrix and slow-release function, and solves the uneven drug distribution and associated infection risk of traditional intervention methods by regulating the synergistic regeneration of epidermodermis and vascular units. Its mechanical adaptability (dry toughness/wet plasticity) and the ability of inducing adipose regeneration provide a new strategy of both structural strengthening and metabolic support for skin dilation, also laying a mechanism and empirical foundation for clinical transformation of tissue engineering materials.

Adipose Decellularized Matrix: A Promising Skeletal Muscle Tissue Engineering Material for Volume Muscle Loss

Volume muscle loss is a severe injury often caused by trauma, fracture, tumor resection, or degenerative disease, leading to long-term dysfunction or disability. The current gold-standard treatment is autologous muscle tissue transplantation, with limitations due to donor site restrictions, complications, and low regeneration efficiency. Tissue engineering shows potential to overcome these challenges and achieve optimal muscle regeneration, vascularization, nerve repair, and immunomodulation. In the field of muscle tissue engineering, skeletal muscle decellularized matrices are regarded as an ideal material due to their similarity to the defect site environment, yet they suffer from difficulties in preparation, severe fibrosis, and inconsistent experimental findings. Adipose decellularized matrices (AdECMs) have demonstrated consistent efficacy in promoting muscle regeneration, and their ease of preparation and abundant availability make them even more attractive. The full potential of AdECMs for muscle regeneration remains to be explored. The aim of this review is to summarize the relevant studies on using AdECMs to promote muscle regeneration, to summarize the preparation methods of various applied forms, and to analyze their advantages and shortcomings, as well as to further explore their mechanisms and to propose possible improvements, so as to provide new ideas for the clinical solution of the problem of volume muscle loss.

Exploring Biomaterial Scaffolds for Eyelid Reconstruction: A Synthesis of Experimental Findings

This review synthesizes experimental findings on various biomaterial scaffolds used in eyelid reconstruction. It examines the structural properties, cellular responses, and functional outcomes of scaffolds such as chitosan, poly(propylene glycol fumarate)-2-hydroxyethyl methacrylate, poly(propylene glycol fumarate) - type I collagen (PPF-Col), decellularized matrix-polycaprolactone, branched polyethylene, collagen, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, and poly(lactic-co-glycolic acid. These scaffolds exhibit diverse mechanical and biological properties, with some demonstrating good biocompatibility, tunable properties, and potential for tissue repair. However, there are limitations, including concerns about long-term functionality and a lack of comprehensive evaluations. This review highlights the need for multifunctional scaffolds that combine lid replacement and ocular surface function restoration, as well as the establishment of standardized research methods. The goal is to guide future innovation in the field and improve the quality of life for patients with eyelid defects.

Comparative Analysis of Hydrogels From Porcine Extracellular Matrix for 3D Bioprinting of Adipose Tissue

The extracellular matrix (ECM) is the natural scaffold of all soft tissues in tissue engineering. Of special interest is the use of ECM as a hydrogel, which can be used to enclose cells and to be molded into any form by 3D bioprinting. Protocols for the preparation of ECM vary in the use of physical and chemical processing steps, the use of different detergents for decellularization, and the removal of DNA and RNA residues and show a different use of solvents and wash buffers. We have, therefore, compared seven different variations for the decellularization of a primary porcine isolate to manufacture decellularized adipose tissue (DAT) for their use in adipose tissue engineering and as a hydrogel in particular. Decellularization efficacy was assessed by DNA quantification while retention of ECM components was evaluated by measuring the content of hydroxyproline and glycosaminoglycan (GAGs). Depending on the decellularization protocol, the composition and DNA content of the resulting DAT were different. All DAT samples were processed into hydrogels to assess their mechanical properties as well as their influence on cellular metabolic activity and cell differentiation. The different compositions of the DAT and the resulting hydrogels had an effect on the stability and printability of the gels. Some DAT that were digested with hydrochloric acid (HCl) were more stable than those that were digested with acetic acid (AA). In addition, depending on the protocol, there was a clear effect on adipose-derived stem cells (ASC), endothelial cells and fibroblasts, cultured with the hydrogels. The differentiation of ASC to adipocytes could be achieved on most of the hydrogels. Human dermal microvascular endothelial cells (HDMEC) showed significantly better metabolic activity on hydrogels digested with HCl than digested with AA. HDMEC cultured on hydrogel #2 digested with HCl showed a 40% higher metabolic activity compared to collagen as a positive control, whereas culturing HDMEC on hydrogel #2 digested with AA resulted in a cellular metabolic activity loss of 60%. In a triculture of all three cell types, the formation of first tubular networks by HDMEC was achieved depending on the hydrogel used.

Injectable Human Acellular Adipose Matrix with Crosslinked Hyaluronic Acid and Carboxymethyl Cellulose Gels for Soft Tissue Augmentation

BACKGROUND

Fillers have become a viable treatment option for addressing volume deficits, whether for aesthetic purposes or due to trauma or congenital deformities. While most fillers effectively maintain volume, promoting adipogenesis remains a significant challenge. This study investigated a biomaterial designed to maintain volume both in the short and long term while promoting adipose tissue formation, focusing on the biological properties of a human acellular adipose matrix (AAM) combined with crosslinked hyaluronic acid (HA) and carboxymethyl cellulose (CMC) gels.

METHODS

The AAM was prepared through delipidation and decellularization and evaluated for residual fat and cells. To assess its performance, the AAM was compared with conventional collagen scaffolds for the proliferation and adipogenic differentiation of human adipose-derived stem cells(hADSCs) in vitro. An injectable AAM filler was developed by combining AAM with crosslinked HA and CMC gels for the desired rheological properties. Over 12 weeks, the AAM filler, conventional HA filler, and adipose tissue were compared in a nude mice model, assessing volume retention, cell incorporation, and adipogenesis.

RESULTS

The AAM showed effective fat and cell removal and promoted the viability and adipogenic differentiation of hADSCs in vitro. The AAM filler exhibited six times higher viscosity than HA filler. It also outperformed both HA filler and adipose tissue in volume retention and cell incorporation, and new adipose tissue formation.

CONCLUSIONS

These results suggest that AAM filler is a promising biomaterial for soft tissue augmentation, particularly in applications requiring volume retention and adipogenesis.

Efficacy and Safety of Cell-Assisted Acellular Adipose Matrix Transfer for Volume Retention and Regeneration Compared to Hyaluronic Acid Filler Injection

BACKGROUND

Cell-assisted acellular adipose matrix (AAM) transfer is a novel technique for soft tissue volume restoration, where AAM acts as a scaffold for tissue proliferation and promotes host cell migration, vascularization, and adipogenesis. This study aimed to evaluate the efficacy and safety of in vivo cell-assisted AAM transfer compared to hyaluronic acid (HA) filler injection.

METHODS

Human adipose tissue was used to manufacture AAM, and murine adipose-derived stem cells (ASCs) were prepared. Nude mice were divided into four groups: AAM transfer (AT), ASC-assisted AAM transfer (CAT), HA filler injection (HI), and ASC-assisted HA filler injection (CHI). Eight weeks post-transfer, in vivo graft volume/weight, histology, and gene expression were analyzed to assess efficacy and safety.

RESULTS

The AAM retained its three-dimensional scaffold structure without cellular components. AT/CAT showed lower volume retention than HA/CHA; however, CAT maintained a similar volume to HA. Histologically, adipogenesis and collagen formation were increased in AT/CAT compared to HA/CHA, with CAT showing the highest levels. CAT also demonstrated superior angiogenesis, adipogenesis, and gene expression (Vegf and Pparg), along with lower Il-6 expression, higher Il-10 expression, and reduced capsule formation, indicating better biocompatibility.

CONCLUSIONS

Cell-assisted AAM transfer is a promising technique for volume retention and tissue regeneration, offering a safe and effective alternative to HA filler injections.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Bioactive scaffolds for tissue engineering: A review of decellularized extracellular matrix applications and innovations

Decellularized extracellular matrix (dECM) offers a three-dimensional, non-immunogenic scaffold, enriched with bioactive components, making it a suitable candidate for tissue regeneration. Although dECM-based scaffolds have been successfully implemented in preclinical and clinical settings within tissue engineering and regenerative medicine, the mechanisms of tissue remodeling and functional restoration are not fully understood. This review critically assesses the state-of-the-art in dECM scaffolds, including decellularization techniques for various tissues, quality control and cross-linking. It highlights the functional properties of dECM components and their latest applications in multiorgan tissue engineering and biomedicine. Additionally, the review addresses current challenges and limitations of decellularized scaffolds and offers perspectives on future directions in the field.

Challenges in Application: Gelation Strategies of DAT-Based Hydrogel Scaffolds

Decellularized adipose tissue (DAT) has great clinical applicability, owing to its abundant source material, natural extracellular matrix microenvironment, and nonimmunogenic attributes, rendering it a versatile resource in the realm of tissue engineering. However, practical implementations are confronted with multifarious limitations. Among these, the selection of an appropriate gelation strategy serves as the foundation for adapting to diverse clinical contexts. The cross-linking strategies under varying physical or chemical conditions exert profound influences on the ultimate morphology and therapeutic efficacy of DAT. This review sums up the processes of DAT decellularization and subsequent gelation, with a specific emphasis on the diverse gelation strategies employed in recent experimental applications of DAT. The review expounds upon methodologies, underlying principles, and clinical implications of different gelation strategies, aiming to offer insights and inspiration for the application of DAT in tissue engineering and advance research for tissue engineering scaffold development.

Constructing the Well Regenerated Decellularized Adipose Tissue Using External Volume Expansion Device

BACKGROUND

External volume expansion (EVE) devices has been demonstrated to enhance the survival of fat grafts. Decellularized adipose tissue (DAT) serves as a promising scaffold for adipose regeneration; however, the effectiveness of adipose regeneration in DAT remains limited, and the underlying mechanisms of its regeneration require further investigation.

OBJECTIVE

This study explores the potential of EVE technology to enhance DAT-mediated adipogenesis by facilitating cellular recruitment and establishing a microenvironment conducive to adipose tissue regeneration.

METHODS

DAT was injected into the dorsal area of rats, followed by daily treatment with an EVE suction device for 10 hours per day over 14 days. Control groups underwent transplantation without suction. After the treatment period, tissue samples were collected and analyzed. This included volume measurement, H&E staining, immunofluorescence staining for CD34, CD90, CD68, CD31, and perilipin, electron microscopy for microscopic analysis, and ELISA analysis for IL1, TNFα, CCL2, and CXCL12.

RESULTS

Fourteen days post-transplantation, the volume of DAT significantly increased in the EVE group compared to the control group. Histological H&E staining revealed a higher peripheral region in the EVE group. Electron microscopy examination showed that EVE suction led to increased porosity in the DAT material, with a greater number of cells adhering to the material. Immunofluorescence staining for CD34/CD90 adipose-derived stem cells also showed a significant increase in the EVE group. The presence of CD68-positive macrophages increased after EVE suction. Evaluation of vascularization using CD31 staining showed a higher level of vascularization in the EVE group compared to the control group. ELISA analysis of IL-1, TNF-α, CCL2, and CXCL12 levels demonstrated that the EVE group effectively increased the levels of adipogenic factors within the DAT.

CONCLUSION

EVE enhances DAT-mediated adipogenesis by promoting stem cell recruitment, macrophage activation, and adipogenesis-related cytokine expression, ultimately improving the regeneration of functional adipose tissue.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Hydrophilic Components as Key Active Ingredients in Adipose-Derived Matrix Bioscaffolds for Inducing Fat Regeneration

Decellularized adipose-derived matrix (DAM) has emerged as a promising biomaterial for soft tissue reconstruction. However, due to a lack of research on its complex composition, the understanding of the key components in DAM remains limited, leading to inconsistent adipogenic properties and challenges in optimizing preparation methods purposefully. In this study, it is proposed for the first time that DAM comprises two distinct components: hydrophilic (H-DAM) and lipophilic (L-DAM), each with markedly different effects on fat regeneration. It is confirmed that H-DAM is the key component for inducing fat regeneration due to its enhanced cell-cell and cell-scaffold interactions, primarily mediated by the Hedgehog signaling pathway. In contrast, L-DAM exhibits poor cell adhesion and contains more antigenic components, leading to a higher immunoinflammatory response and reduced adipogenesis. In addition, it is found that intracellular proteins, which are more abundant in H-DAM, can be retained as beneficial components due to their hydrophilicity, contrary to the conventional view that they shall be removed. Accordingly, a purified bioscaffold with unprecedented efficacy is proposed for fat regeneration and reduced immunogenicity. This finding provides insights for developing scaffolds for fat regeneration and promotes the realization of xenotransplantation.

Advances in, and prospects of, 3D preclinical models for skin drug discovery

The skin has an important role in regulating homeostasis and protecting the body from endogenous and exogenous microenvironments. Although 3D models for drug discovery have been extensively studied, there is a growing demand for more advanced 3D skin models to enhance skin research. The use of these advanced skin models holds promise across domains such as cosmetics, skin disease treatments, and toxicity testing of new therapeutics. Recent advances include the development of skin-on-a-chip, spheroids, reconstructed skin, organoids, and computational approaches, including quantitative structure-activity relationship (QSAR) and quantitative structure-property relationship (QSPR) research. These innovations are bridging the gap between traditional 2D and advanced 3D models, moving progress from research to clinical applications. In this review, we highlight in vitro and computational skin models with advanced drug discovery for skin-related applications.

Comparison of Stored and Fresh Injectable Acellular Adipose Matrix in Soft Tissue Reconstruction in a Murine Model

BACKGROUND

We previously showed comparable volume effects of injections of acellular adipose matrix (AAM), an adipose tissue-derived extracellular matrix, and conventional fat grafting in a murine model. Thus, AAM could be a novel allogenic injectable product. However, its retention rate poses a concern, as repeated AAM injections may be required in some cases. This study investigated the biological properties and therapeutic value of stored AAM and compared them with those of fresh AAM, in a murine model.

METHODS

AAM was manufactured from fresh human abdominoplasty fat. Fresh and stored injectable AAM was prepared within 24 h and 3 months after generation, respectively. Either fresh or stored injectable AAM was injected into the scalp of athymic nude mice (0.2 mL/sample, n = 6 per group). After 8 weeks, graft retention was assessed through weight measurement, and histological analysis was performed, including immunofluorescence staining for CD31 and perilipin.

RESULTS

Retention rate was significantly reduced in the stored compared to the fresh injectable AAM group. Nevertheless, histological analysis revealed comparable inflammatory cell presence, with minimal capsule formation, in both groups. Adipogenesis occurred in both groups, with no significant difference in the blood vessel area (%) between groups.

CONCLUSIONS

Although the volume effects of stored AAM for soft tissue reconstruction were limited compared to those of fresh injectable AAM, stored AAM had similar capacity for adipogenesis and angiogenesis. This promising allogeneic injectable holds the potential to serve as an effective "off-the-shelf" alternative for repeated use within a 3-month storage period.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://link.springer.com/journal/00266 .

Effect of Injectable Acellular Adipose Matrix on Soft Tissue Reconstruction in a Murine Model

BACKGROUND

The extracellular matrix isolated from adipose tissue, known as acellular adipose matrix (AAM), represents a novel biomaterial. AAM functions as a scaffold that not only supports stem cell proliferation and differentiation but also induces adipogenesis and angiogenesis. This study aims to investigate the volumetric effects and microenvironmental changes associated with injectable AAM in comparison to conventional fat grafting.

METHODS

AAM was manufactured from fresh human abdominoplasty fat using a mechanically modified method and then transformed into an injectable form. Lipoaspirate was harvested employing the Coleman technique. A weight and volume study was conducted on athymic nude mice by injecting either injectable AAM or lipoaspirate into the scalp (n=6 per group). After eight weeks, graft retention was assessed through weight measurement and volumetric analysis using micro-computed tomography (micro-CT) scanning. Histological analysis was performed using immunofluorescence staining for perilipin and CD31.

RESULTS

Injectable AAM exhibited similar weight and volume effects in murine models. Histological analysis revealed comparable inflammatory cell presence with minimal capsule formation when compared to conventional fat grafts. Adipogenesis occurred in both AAM-injected and conventional fat graft models, with no significant difference in the blood vessel area (%) between the two.

CONCLUSIONS

In summary, injectable AAM demonstrates effectiveness comparable to conventional fat grafting concerning volume effects and tissue regeneration in soft tissue reconstruction. This promising allogeneic injectable holds the potential to serve as a safe and effective "Off-the-Shelf" alternative in both aesthetic and reconstructive clinical practices.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Application of Decellularized Adipose Matrix as a Bioscaffold in Different Tissue Engineering

With the development of tissue engineering, the application of decellularized adipose matrix as scaffold material in tissue engineering has been intensively explored due to its wide source and excellent potential in tissue regeneration. Decellularized adipose matrix is a promising candidate for adipose tissue regeneration, while modification of decellularized adipose matrix scaffold can also allow it to transcend the limitations of adipose tissue source properties and applied to other tissue engineering fields, including cartilage and bone tissue engineering, neural tissue engineering, and skin tissue engineering. In this review, we summarized the development of the applications of decellularized adipose matrix in different tissue engineering and present future perspectives.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Combined Use of Autologous Sustained-Release Scaffold of Adipokines and Acellular Adipose Matrix to Construct Vascularized Adipose Tissue

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.

Bioactive decellularized adipose matrix prepared using a rapid, nonchemical/enzymatic method for adipogenesis

Recent developments in the field of regenerative surgeries and medical applications have led to a renewed interest in adipose tissue-enriched mesenchymal stem cell scaffolds. Various advantages declared for the decellularized adipose matrix (DAM) have caused its extensive use in the transfer of stem cells or growth factors for soft tissue regeneration induction. Meanwhile, the long-term application of detergents toward DAM regeneration has been assumed as a risky obstacle in this era. Herein, a rapid, mechanical protocol was developed to prepare DAM (M-DAM) without chemicals/enzymes and was comprehensively compared with the ordinary DAM (traditional chemical method). Accordingly, this method could effectively hinder oils and cells, sustain the structural and biological elements, and contain a superior level of collagen content. In addition, more protein numbers, as well as higher basement membrane elements, glycoproteins, and extracellular matrix-related proteins were detected in the regenerated M-DAM. Also, superior adipogenesis and angiogenesis proteins were distinguished. The noncytotoxicity of the M-DAM was also approved, and a natural ecological niche was observed for the proliferation and differentiation of stem cells, confirming its great potential for vascularization and adipogenesis in vivo. The suggested technique could effectively prepare the modified DAM in variant constructions of tablets, powders, emulsions, hydrogels, and different three-dimensional-printed structures. Hence, this rapid, mechanical process can produce bioactive DAM, which has the potential to be widely used in various research fields of regenerative medicine.

Biomedical Application of Decellularized Scaffolds

Tissue loss and end-stage organ failure are serious health problems across the world. Natural and synthetic polymer scaffold material based artificial organs play an important role in the field of tissue engineering and organ regeneration, but they are not from the body and may cause side effects such as rejection. In recent years, the biomimetic decellularized scaffold based materials have drawn great attention in the tissue engineering field for their good biocompatibility, easy modification, and excellent organism adaptability. Therefore, in this review, we comprehensively summarize the application of decellularized scaffolds in tissue engineering and biomedicine in recent years. The preparation methods, modification strategies, construction of artificial tissues, and application in biomedical applications are discussed. We hope that this review will provide a useful reference for research on decellularized scaffolds and promote their application tissue engineering.

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

Application of decellularization-recellularization technique in plastic and reconstructive surgery

ABSTRACT

In the field of plastic and reconstructive surgery, the loss of organs or tissues caused by diseases or injuries has resulted in challenges, such as donor shortage and immunosuppression. In recent years, with the development of regenerative medicine, the decellularization-recellularization strategy seems to be a promising and attractive method to resolve these difficulties. The decellularized extracellular matrix contains no cells and genetic materials, while retaining the complex ultrastructure, and it can be used as a scaffold for cell seeding and subsequent transplantation, thereby promoting the regeneration of diseased or damaged tissues and organs. This review provided an overview of decellularization-recellularization technique, and mainly concentrated on the application of decellularization-recellularization technique in the field of plastic and reconstructive surgery, including the remodeling of skin, nose, ears, face, and limbs. Finally, we proposed the challenges in and the direction of future development of decellularization-recellularization technique in plastic surgery.

Evolution of biomimetic ECM scaffolds from decellularized tissue matrix for tissue engineering: A comprehensive review

Tissue engineering is essentially a technique for imitating nature. Natural tissues are made up of three parts: extracellular matrix (ECM), signaling systems, and cells. Therefore, biomimetic ECM scaffold is one of the best candidates for tissue engineering scaffolds. Among the many scaffold materials of biomimetic ECM structure, decellularized ECM scaffolds (dECMs) obtained from natural ECM after acellular treatment stand out because of their inherent natural components and microenvironment. First, an overview of the family of dECMs is provided. The principle, mechanism, advances, and shortfalls of various decellularization technologies, including physical, chemical, and biochemical methods are then critically discussed. Subsequently, a comprehensive review is provided on recent advances in the versatile applications of dECMs including but not limited to decellularized small intestinal submucosa, dermal matrix, amniotic matrix, tendon, vessel, bladder, heart valves. And detailed examples are also drawn from scientific research and practical work. Furthermore, we outline the underlying development directions of dECMs from the perspective that tissue engineering scaffolds play an important role as an important foothold and fulcrum at the intersection of materials and medicine. As scaffolds that have already found diverse applications, dECMs will continue to present both challenges and exciting opportunities for regenerative medicine and tissue engineering.

Recent advances in decellularized biomaterials for wound healing

The skin is one of the most essential organs in the human body, interacting with the external environment and shielding the body from diseases and excessive water loss. Thus, the loss of the integrity of large portions of the skin due to injury and illness may lead to significant disabilities and even death. Decellularized biomaterials derived from the extracellular matrix of tissues and organs are natural biomaterials with large quantities of bioactive macromolecules and peptides, which possess excellent physical structures and sophisticated biomolecules, and thus, promote wound healing and skin regeneration. Here, we highlighted the applications of decellularized materials in wound repair. First, the wound-healing process was reviewed. Second, we elucidated the mechanisms of several extracellular matrix constitutes in facilitating wound healing. Third, the major categories of decellularized materials in the treatment of cutaneous wounds in numerous preclinical models and over decades of clinical practice were elaborated. Finally, we discussed the current hurdles in the field and anticipated the future challenges and novel avenues for research on decellularized biomaterials-based wound treatment.

Insulin modified Decellularized Adipose Tissue/Tremella Polysaccharide hydrogel loaded with ADSCs for skin wound healing

Full-thickness skin wounds still represent a challenge for clinical treatment. Adipose-derived stem cells (ADSCs) therapy is a promising approach to achieve efficient healing in skin wounds. The excellent cell scaffold can promote proliferation, differentiation and paracrine of ADSCs in wound microenvironment, and is a key factor in ADSCs application. Herein, we first prepared the composite hydrogel with decellularized adipose tissue (DAT) and tremella polysaccharide (TPS), and loaded insulin (INS) into the DAT/TPS composite hydrogel (DAT/TPS-gel) to fabricate an efficient carrier for ADSCs in treating skin wound. Our study showed that INS modified DAT/TPS-gel (INS-DAT/TPS-gel) can promote the proliferation, differentiation and paracrine of ADSCs. INS-DAT/TPS-gel laden with ADSCs (ADSCs/INS-DAT/TPS-gel) effectively facilitated the skin wound healing in SD rats. These findings indicated that INS-DAT/TPS-gel was an effective scaffold for ADSCs transplantation, and ADSCs/INS-DAT/TPS-gel provides a potential strategy for the treatment of skin wounds.

Adjusting the stiffness of a cell-free hydrogel system based on tissue-specific extracellular matrix to optimize adipose tissue regeneration

Background

Large-area soft tissue defects are challenging to reconstruct. Clinical treatment methods are hampered by problems associated with injury to the donor site and the requirement for multiple surgical procedures. Although the advent of decellularized adipose tissue (DAT) offers a new solution to these problems, optimal tissue regeneration efficiency cannot be achieved because the stiffness of DAT cannot be altered in vivo by adjusting its concentration. This study aimed to improve the efficiency of adipose regeneration by physically altering the stiffness of DAT to better repair large-volume soft tissue defects.

Methods

In this study, we formed three different cell-free hydrogel systems by physically cross-linking DAT with different concentrations of methyl cellulose (MC; 0.05, 0.075 and 0.10 g/ml). The stiffness of the cell-free hydrogel system could be regulated by altering the concentration of MC, and all three cell-free hydrogel systems were injectable and moldable. Subsequently, the cell-free hydrogel systems were grafted on the backs of nude mice. Histological, immunofluorescence and gene expression analyses of adipogenesis of the grafts were performed on days 3, 7, 10, 14, 21 and 30.

Results

The migration of adipose-derived stem cells (ASCs) and vascularization were higher in the 0.10 g/ml group than in the 0.05 and 0.075 g/ml groups on days 7, 14 and 30. Notably, on days 7, 14 and 30, the adipogenesis of ASCs and adipose regeneration were significantly higher in the 0.075 g/ml group than in the 0.05 g/ml group (p < 0.01 or p < 0.001) and 0.10 g/ml group (p < 0.05 or p < 0.001).

Conclusion

Adjusting the stiffness of DAT via physical cross-linking with MC can effectively promote adipose regeneration, which is of great significance to the development of methods for the effective repair and reconstruction of large-volume soft tissue defects.

Analysis of DAT Combined with the VSD Technique in Wound Repair of Rats and Its Effect on Inflammatory Factors

The clinical efficacy of decellularized adipose tissue (DAT) combined with vacuum sealing drainage (VSD) in the treatment of wound healing in rats is investigated, and the changes of inflammatory factors are analyzed. The tissue defect model of SD (Sprague-Dawley) rats is established and divided into the combined group (n = 12) and the control group (n = 12) according to different treatment methods. The control group is treated with a single VSD technique, and the combined group is treated with DAT on the basis of the control group. The wound healing time of the two groups is observed. Wound tissue is collected 1 day, 10 days, 20 days, and 30 days after treatment, and neutrophil infiltration is observed by HE (hematoxylin-eosin) staining. The expression changes of IL-6 and IL-13 at each time point before and after treatment are compared. Histological observation shows that the cell infiltration is reduced in both groups, and the wound repair in the combined group is better than that in the control group. The experimental results show that the DAT combined with the VSD technique can further speed up wound healing and reduce inflammation in rats.

Adipose Stem Cells in Regenerative Medicine: Looking Forward

Over the last decade, stem cell-based regenerative medicine has progressed to clinical testing and therapeutic applications. The applications range from infusions of autologous and allogeneic stem cells to stem cell-derived products. Adult stem cells from adipose tissue (ASCs) show significant promise in treating autoimmune and neurodegenerative diseases, vascular and metabolic diseases, bone and cartilage regeneration and wound defects. The regenerative capabilities of ASCs in vivo are primarily orchestrated by their secretome of paracrine factors and cell-matrix interactions. More recent developments are focused on creating more complex structures such as 3D organoids, tissue elements and eventually fully functional tissues and organs to replace or repair diseased or damaged tissues. The current and future applications for ASCs in regenerative medicine are discussed here.

The Future of Fat Grafting

One of the earliest reported cases of autologous fat grafting (AFG) was by Neuber in 1893 and consisted of the transfer of small lobules of fat from the upper arm for cicatrical depression of the face. He advocated the use of smaller grafts, noting that pieces larger than the size of a bean would form cysts. In 1895, Czerny excised a lumbar lipoma and transplanted it to the chest for breast reconstruction. Since these early reports, the knowledge base around AFG has expanded exponentially, as illustrated by the other papers within this special topic. As we embark on the next phase of AFG in the clinical setting, there are several directions which are near-clinical translation. This paper discusses future directions in fat grafting that build on optimization of our current techniques as clinical indications expand, such as supplementing purified lipoaspirate and the associated regulatory burden, or deconstructing adipose tissue to selectively use adipose graft components for a variety of regenerative indications.