Targeted delivery of adipose-derived stem cells via acellular dermal matrix enhances wound repair in diabetic rats

Injectable ADM temperature-sensitive hydrogel loaded with bFGF in diabetic rat wound healing study

Background: Diabetic wound is one of the most common diabetic chronic complications. Effective treatments of diabetic wound remain limited. Here, we explored the effects of basic fibroblast growth factor (bFGF)-acellular dermal matrix (ADM) hydrogel on the diabetic wound. Methods: The bFGF-ADM hydrogel was manufactured by mixing 180 µL ADM hydrogel and 20 µL bFGF aqueous solution (10 mg/mL). The morphology of ADM hydrogel and bFGF-ADM hydrogel was observed under scanning electron microscope. The release property of bFGF-ADM hydrogel was determined by ELISA. CCK-8 assay was utilized to estimate the cell viability of mouse skin fibroblasts. The diabetes mellitus (DM) model was established in rats. The four wounds on the back of each DM rat were treated with the ADM hydrogel, bFGF-ADM hydrogel, bFGF aqueous solution and no solution (control), respectively. The wound healing rate of each rat was estimated. The traumatized skin tissue of each rat was observed by H&E staining and Sirius red staining. Results: The bFGF-ADM hydrogel displayed an interconnected pore structure and bFGF was gradually released from the bFGF-ADM hydrogel over time. The bFGF-ADM hydrogel could enhance the cell viability of skin fibroblasts and promote the wound healing rate, the re-epithelialization of wound and increase the collagen fiber content of dermis. And the bFGF-ADM hydrogel exhibited better therapeutic effects of diabetic wound than either bFGF or ADM alone. Conclusions: Our study revealed that the bFGF-ADM hydrogel could promote diabetic wound healing.

Combination therapy of placenta-derived mesenchymal stem cells and artificial dermal scaffold promotes full-thickness skin defects vascularization in rat animal model

PURPOSE

Recently, placenta-derived mesenchymal stem cells (PMSCs) have garnered considerable attention in tissue repair and regeneration. The present study was conducted to evaluate the effect of PMSCs on artificial dermal scaffold (ADS) angiogenesis and their combination therapy on wound closure.

MATERIAL AND METHODS

Herein, the growth and survival of PMSCs in ADS were explored. CCK8, scratch wound, and tubule formation assays were employed to investigate the effects of ADS conditioned medium (CM) and ADS-PMSCs CM on human umbilical vein endothelial cells (HUVECs). The effect of ADS-PMSCs on full-thickness skin defects healing was evaluated based on a rat model. Wound healing progresses was meticulously investigated through hematoxylin and eosin (HE), Masson's trichrome, and immunohistochemical staining analyses.

RESULTS

In vitro cell culture results demonstrated the proliferation of PMSCs in ADS. The ADS-PMSCs CM notably stimulated the proliferation, migration, and tube formation of HUVECs compared to the ADS CM group. In the rat full-thickness skin defect model, the ADS-PMSCs treatment significantly accelerated the vascularization area of ADS after 2 weeks. Besides, HE and Masson's trichrome staining results indicated that ADS-PMSCs treatment significantly enhanced fibroblast proliferation and collagen fiber 2 weeks after surgical procedure. Compared to the ADS group, collagen fiber arrangement was thicker in the ADS-PMSCs group. Immunohistochemical staining reinforced this finding, illustrating a substantial increase in CD31 expression within the ADS-PMSCs group.

CONCLUSIONS

The results suggest that the combination of ADS with PMSCs accelerates ADS vascularization by fostering granulation tissue development and boosting the formation of new blood vessels.

Innovative approaches to tissue engineering: Utilizing decellularized extracellular matrix hydrogels for mesenchymal stem cell transport

In recent years, the realm of tissue regeneration experienced significant advancements, leading to the development of innovative therapeutic agents. The systemic delivery of mesenchymal stem cells (MSCs) emerged as a promising strategy for promoting tissue regeneration. However, this approach is hindered by hurdles such as poor cell survival, limited cell propagation, and inadequate cell integration. Decellularized extracellular matrix (dECM) hydrogel serves as an innovative carrier that protects MSCs from the detrimental effects of the hostile microenvironment, facilitates their localization and retention at the injection site, and preserves their viability. Regarding its low immunogenicity, low cytotoxicity, high biocompatibility, and its ability to mimic natural extracellular matrix (ECM), this natural hydrogel offers a new avenue for systemic delivery of MSCs. This review digs into the properties of dECM hydrogels (dECMHs), the methods employed for decellularization and the utilization of dECMH as carriers for various types of MSCs for tissue regeneration purposes. This review also sheds light on the benefits of hybrid hydrogels composed of dECMH and other components such as proteins and polysaccharides. By addressing the limitations of conventional hydrogels and enhancing efficacy of cell therapy, dECMH opens new pathways for the future of tissue regeneration.

Porcine pericardial decellularized matrix bilayer patch containing adipose stem cell-derived exosomes for the treatment of diabetic wounds

Chronic hard-to-heal wounds pose a significant threat to patients' health and quality of life, and their clinical management remains a challenge. Adipose-derived stem cell exosomes (ADSC-exos) have shown promising results in promoting diabetic wound healing. However, effectively enhancing the retention of exosomes in wounds for treatment remains a key issue that needs to be addressed. There is a pressing need to develop new materials or methods to improve the bioavailability of exosomes. Porcine pericardium, an extracellular matrix-rich tissue, is easily obtainable and widely available. Decellularized porcine pericardium removes cellular components while retaining an extracellular matrix that supports cellular growth, making it an ideal raw material for preparing wound dressings. In this study, we developed porcine pericardial decellularized matrix bilayer patches loaded with ADSC-exos, which were transplanted into diabetic mouse skin wounds. Histological and immunohistochemical analyses revealed that these bilayer matrix patches accelerate wound healing by promoting granulation tissue formation, re-epithelialization, stimulating vascularization, and enhancing collagen production. In terms of the underlying biological mechanism, we found that decellularized extracellular matrix bilayer patches loaded with ADSC-exos enhanced the proliferation and migration of human dermal fibroblasts (HDFs) and HaCaT cells in vitro, and promoted tube formation in human umbilical vein endothelial cells (HUVECs). This research demonstrated that the porcine pericardial decellularized matrix is well-suited for exosome delivery and that these bilayer patches hold great potential in promoting diabetic wound healing, providing evidence to support the future clinical application of ADSC-exos.

Prevention of medication-related osteonecrosis of the jaw in mice by adipose-derived stem cells associated with activated autophagic flux

Background/purpose

Medication-related osteonecrosis of the jaw (MRONJ) represents a rare yet serious adverse reaction associated with the prolonged use of anti-bone resorptive or anti-angiogenic agents. This study aimed to investigate the impact and underlying mechanisms of adipose-derived stem cells (ADSCs) in preventing MRONJ in a mouse model.

Materials and methods

Following tooth extraction in MRONJ mice, ADSCs or PBS were administered via the tail vein. The healing progress of gingival epithelium and the extraction socket was assessed using a stereoscopic microscope and histological analysis. Immunofluorescence was employed to examine markers associated with autophagy (LC3 and SQSTM1) and apoptosis (Cleaved-CASP 3). Statistical analysis involved unpaired Student's t-test and ANOVA on ABI Prism 7500, with P-values below 0.05 deemed statistically significant.

Results

ADSCs enhanced gingival epithelium migration and facilitated new bone formation. In the MRONJ group, the expressions of autophagy-related protein LC3 and SQSTM1 in gingival epithelium were concurrently elevated, which indicated autophagic flux was impaired. Conversely, when treated with ADSCs, the expression of LC3 and SQSTM1 were downregulated, similarly to the Control group. Mechanically, zoledronate induced a deficiency of autophagosome-lysosome fusion in epithelial cells, while ADSCs supernatant could promote the autolysosomes formation. Furthermore, ADSCs rescued the number of autophagy-related apoptotic cells in the gingival epithelium of MRONJ.

Conclusion

ADSCs could effectively prevent the occurrence of MRONJ, likely through the activation of autophagic flux and the inhibition of autophagy-related apoptosis in gingival epithelium. These findings enhanced the understanding of MRONJ pathogenesis and propose a potential therapeutic target for this disease.

The role of adipose tissue-derived stromal cells, macrophages and bioscaffolds in cutaneous wound repair

Skin healing is a complex and dynamic physiological process that follows mechanical alteration of the skin barrier. Under normal conditions, this complex process can be divided into at least three continuous and overlapping phases: an inflammatory reaction, a proliferative phase that leads to tissue reconstruction and a phase of tissue remodeling. Macrophages critically contribute to the physiological cascade for tissue repair. In fact, as the inflammatory phase progresses, macrophage gene expression gradually shifts from pro-inflammatory M1-like to pro-resolutive M2-like characteristics, which is critical for entry into the repair phase. A dysregulation in this macrophage' shift phenotype leads to the persistence of the inflammatory phase. Mesenchymal stromal cells and specifically the MSC-derived from adipose tissue (ADSCs) are more and more use to treat inflammatory diseases and several studies have demonstrated that ADSCs promote the wound healing thanks to their neoangiogenic, immunomodulant and regenerative properties. In several studies, ADSCs and macrophages have been injected directly into the wound bed, but the delivery of exogenous cells directly to the wound raise the problem of cell engraftment and preservation of pro-resolutive phenotype and viability of the cells. Complementary approaches have therefore been explored, such as the use of biomaterials enriched with therapeutic cell to improve cell survival and function. This review will present a background of the current scaffold models, using adipose derived stromal-cells and macrophage as therapeutic cells for wound healing, through a discussion on the potential impact for future applications in skin regeneration. According to the PRISMA statement, we resumed data from investigations reporting the use ADSCs and bioscaffolds and data from macrophages behavior with functional biomaterials in wound healing models. In the era of tissue engineering, functional biomaterials, that can maintain cell delivery and cellular viability, have had a profound impact on the development of dressings for the treatment of chronic wounds. Promising results have been showed in pre-clinical reports using ADSCs- and macrophages-based scaffolds to accelerate and to improve the quality of the cutaneous healing.

Molecular immunological mechanisms of impaired wound healing in diabetic foot ulcers (DFU), current therapeutic strategies and future directions

Diabetic foot ulcer (DFU) is a foremost cause of amputation in diabetic patients. Consequences of DFU include infections, decline in limb function, hospitalization, amputation, and in severe cases, death. Immune cells including macrophages, regulatory T cells, fibroblasts and other damage repair cells work in sync for effective healing and in establishment of a healthy skin barrier post-injury. Immune dysregulation during the healing of wounds can result in wound chronicity. Hyperglycemic conditions in diabetic patients influence the pathophysiology of wounds by disrupting the immune system as well as promoting neuropathy and ischemic conditions, making them difficult to heal. Chronic wound microenvironment is characterized by increased expression of matrix metalloproteinases, reactive oxygen species as well as pro-inflammatory cytokines, resulting in persistent inflammation and delayed healing. Novel treatment modalities including growth factor therapies, nano formulations, microRNA based treatments and skin grafting approaches have significantly augmented treatment efficiency, demonstrating creditable efficacy in clinical practices. Advancements in local treatments as well as invasive methodologies, for instance formulated wound dressings, stem cell applications and immunomodulatory therapies have been successful in targeting the complex pathophysiology of chronic wounds. This review focuses on elucidating the intricacies of emerging physical and non-physical therapeutic interventions, delving into the realm of advanced wound care and comprehensively summarizing efficacy of evidence-based therapies for DFU currently available.

Mesenchymal stem cell therapy in diabetic foot ulcer: An updated comprehensive review

Background

Diabetes has evolved into a worldwide public health issue. One of the most serious complications of diabetes is diabetic foot ulcer (DFU), which frequently creates a significant financial strain on patients and lowers their quality of life. Up until now, there has been no curative therapy for DFU, only symptomatic relief or an interruption in the disease's progression. Recent studies have focused attention on mesenchymal stem cells (MSCs), which provide innovative and potential treatment candidates for several illnesses as they can differentiate into various cell types. They are mostly extracted from the placenta, adipose tissue, umbilical cord (UC), and bone marrow (BM). Regardless of their origin, they show comparable features and small deviations. Our goal is to investigate MSCs' therapeutic effects, application obstacles, and patient benefit strategies for DFU therapy.

Methodology

A comprehensive search was conducted using specific keywords relating to DFU, MSCs, and connected topics in the databases of Medline, Scopus, Web of Science, and PubMed. The main focus of the selection criteria was on English-language literature that explored the relationship between DFU, MSCs, and related factors.

Results and Discussion

Numerous studies are being conducted and have demonstrated that MSCs can induce re-epithelialization and angiogenesis, decrease inflammation, contribute to immunological modulation, and subsequently promote DFU healing, making them a promising approach to treating DFU. This review article provides a general snapshot of DFU (including clinical presentation, risk factors and etiopathogenesis, and conventional treatment) and discusses the clinical progress of MSCs in the management of DFU, taking into consideration the side effects and challenges during the application of MSCs and how to overcome these challenges to achieve maximum benefits.

Conclusion

The incorporation of MSCs in the management of DFU highlights their potential as a feasible therapeutic strategy. Establishing a comprehensive understanding of the complex relationship between DFU pathophysiology, MSC therapies, and related obstacles is essential for optimizing therapy outcomes and maximizing patient benefits.

Comparable Effects on Healing between Autologous Diabetic Adipose-Derived Stem Cells and Allogeneic Normal Counterparts

BACKGROUND

Adipose-derived stem cell (ASC) therapy is considered a promising strategy for improving impaired wound healing, especially in diabetics. Although the therapeutic potential of allogeneic ASCs from healthy donors is naturally limited, that of autologous ASCs from diabetic patients is questionable. The aim of this study was to investigate the impact of diabetic ASCs in the treatment of diabetic wounds.

METHODS

Diabetic ASCs (DMA) and nondiabetic ASCs were isolated from db/db and C57BL/6J mice, and characterized by immunocytochemistry, proliferation, differentiation, and gene expression assays. The effects of both ASCs on healing were investigated using 36 male 10- to 12-week-old db/db mice. Wound size was measured semiweekly until day 28, and histologic and molecular analyses were performed at day 14.

RESULTS

Both ASCs had fibroblast-like morphology and were CD44 + /CD90 + /CD34 - /CD45 - at passage 4. Compared with nondiabetic ASCs in vitro, DMA proliferative capability was restored by passage 4 ( P > 0.05). Although DMA osteogenesis was attenuated ( P < 0.01), both ASCs had similar adipogenesis and expressions of PPARγ/LPL/OCN/RUNX2 ( P > 0.05). In vivo experiments showed that, compared with phosphate-buffered saline control, both ASCs are comparable in improving wound healing ( P < 0.0001), angiogenesis ( P < 0.05), epithelial cell proliferation ( P < 0.05), and granulation tissue formation ( P < 0.0001).

CONCLUSIONS

In both in vitro and in vivo murine models, DMAs have shown a comparable therapeutic capacity to normal ASCs in promoting diabetic wound healing by improving angiogenesis, reepithelialization, and granulation tissue formation. These results support clinical applications of autologous ASCs in diabetic wound treatments.

CLINICAL RELEVANCE STATEMENT

This work has particular surgical relevance as it highlights a theoretical and clinical pathway to use diabetic patients' own ASCs to treat their wounds, bypassing any concerns of cross-host sourcing issues in regenerative medicine.

Human Placenta-Derived Mesenchymal Stem Cells Combined With Artificial Dermal Scaffold Enhance Wound Healing in a Tendon-Exposed Wound of a Rabbit Model

To overcome the difficulty of vascular regeneration in exposed tendon wounds, we combined human placenta-derived mesenchymal stem cells (hPMSCs) with an artificial dermal scaffold and assessed their role in promoting vascular regeneration and wound healing in vivo. hPMSCs were isolated from the human placenta and characterized based on their morphology, phenotypic profiles, and pluripotency. New Zealand rabbits were used to establish an exposed tendon wound model, and hPMSCs and artificial dermal scaffolds were transplanted into the wounds. The results of gross wound observations and pathological sections showed that hPMSCs combined with artificial dermal scaffold transplantation increased the vascularization area of the wound, promoted wound healing, and increased the survival rate of autologous skin transplantation. Following artificial dermal scaffold transplantation, hPMSCs accelerated the vascularization of the dermal scaffold, and the number of fibroblasts, collagen fibers, and neovascularization in the dermal scaffold after 1 week were much higher than those in the control group. Immunohistochemical staining further confirmed that the expression of the vascular endothelial cell marker, CD31, was significantly higher in the combined transplantation group than in the dermal scaffold transplantation group. Our findings demonstrated that hPMSCs seeded onto artificial dermal scaffold could facilitate vascularization of the dermal scaffold and improve tendon-exposed wound healing.

Innovations in Stem Cell Therapy for Diabetic Wound Healing

Significance: The global burden of diabetic wounds, particularly diabetic foot ulcers, continues to have large economic and social impact throughout the world. Current strategies are not sufficient to overcome this burden of disease. Finding newer, more advanced regenerative cell and tissue-based strategies to reduce morbidity remains paramount. Recent Advances: Recent advances in stem cell therapies are discussed. We also highlight the practical issues of translating these advancing technologies into the clinical setting. Critical Issues: We discuss the use of somatic and induced pluripotent stem cells and the stromal vascular fraction, as well as innovations, including the use of 3D bioprinting of skin. We also explore related issues of using regenerative techniques in clinical practice, including the current regulatory landscape and translatability of in vivo research. Future Directions: Advances in stem cell manipulation showcase the best therapeutic resources available to enhance mechanisms of wound healing such as angiogenesis, cell proliferation, and collagen synthesis; potential methods include changing the scaffold microenvironment, including relative oxygen tension, and the use of gene modification and nanotechnology. Secretome engineering, particularly the use of extracellular vesicles, may be another potential cell-derived therapeutic that may enable use of cell-free translational therapy.

Fat Graft Retention: Adipose Tissue, Adipose-Derived Stem Cells, and Aging

SUMMARY

Over the past 30 years, there has been a dramatic increase in the use of autologous fat grafting for soft-tissue augmentation and to improve facial skin quality. Several studies have highlighted the impact of aging on adipose tissue, leading to a decrease of adipose tissue volume and preadipocyte proliferation and increase of fibrosis. Recently, there has been a rising interest in adipose tissue components, including adipose-derived stem/stromal cells (ASCs) because of their regenerative potential, including inflammation, fibrosis, and vascularization modulation. Because of their differentiation potential and paracrine function, ASCs have been largely used for fat grafting procedures, as they are described to be a key component in fat graft survival. However, many parameters as surgical procedures or adipose tissue biology could change clinical outcomes. Variation on fat grafting methods have led to numerous inconsistent clinical outcomes. Donor-to-donor variation could also be imputed to ASCs, tissue inflammatory state, or tissue origin. In this review, the authors aim to analyze (1) the parameters involved in graft survival, and (2) the effect of aging on adipose tissue components, especially ASCs, that could lead to a decrease of skin regeneration and fat graft retention.

CLINICAL RELEVANCE STATEMENT

This review aims to enlighten surgeons about known parameters that could play a role in fat graft survival. ASCs and their potential mechanism of action in regenerative medicine are more specifically described.

Scaffold-based delivery of mesenchymal stromal cells to diabetic wounds

Foot ulceration is a major complication of diabetes mellitus, which results in significant human suffering and a major burden on healthcare systems. The cause of impaired wound healing in diabetic patients is multifactorial with contributions from hyperglycaemia, impaired vascularization and neuropathy. Patients with non-healing diabetic ulcers may require amputation, creating an urgent need for new reparative treatments. Delivery of stem cells may be a promising approach to enhance wound healing because of their paracrine properties, including the secretion of angiogenic, immunomodulatory and anti-inflammatory factors. While a number of different cell types have been studied, the therapeutic use of mesenchymal stromal cells (MSCs) has been widely reported to improve delayed wound healing. However, topical administration of MSCs via direct injection has several disadvantages, including low cell viability and poor cell localization at the wound bed. To this end, various biomaterial conformations have emerged as MSC delivery vehicles to enhance cell viability and persistence at the site of implantation. This paper discusses biomaterial-based MSCs therapies in diabetic wound healing and highlights the low conversion rate to clinical trials and commercially available therapeutic products.

Adipose-Derived Stem Cells for the Treatment of Diabetic Wound: From Basic Study to Clinical Application

Diabetic wounds significantly affect the life quality of patients and may cause amputation and mortality if poorly managed. Recently, a wide range of cell-based methods has emerged as novel therapeutic methods in treating diabetic wounds. Adipose-derived stem cells (ASCs) are considered to have the potential for widespread clinical application of diabetic wounds treatment in the future. This review summarized the mechanisms of ASCs to promote diabetic wound healing, including the promotion of immunomodulation, neovascularization, and fibro synthesis. We also review the current progress and limitations of clinical studies using ASCs to intervene in diabetic wound healing. New methods of ASC delivery have been raised in recent years to provide a standardized and convenient use of ASCs.

Effect of Morphologically Transformed Acellular Dermal Matrix on Chronic Diabetic Wounds: An Experimental Study in a Calvarial Bone Exposure Diabetic Rat Model

BACKGROUND

The use of acellular dermal matrix on chronic diabetic wounds in clinical practice is hindered by its high cost and difficulty in application. We aimed to acquire experimental evidence on the effect of morphologically transformed acellular dermal matrix on chronic diabetic wounds and investigate how this transformation affects the wound healing mechanism.

MATERIALS AND METHODS

We developed a new chronic wound model that resembles a diabetic chronic wound as it involves an open wound with partial calvarial bone exposure in diabetic rats. According to treatment materials, rats were assigned into the CONTROL, ADM, and PASTE groups. The wound healing period was subdivided into T1 and T2 (postoperative days 14 and 30, respectively). Three-staged analyses were performed using 3D camera, histological analysis, and real-time quantitative polymerase chain reaction.

RESULTS

The morphologically transformed acellular dermal matrix showed a compatible treatment rate in the total wound and more rapidly reduced the initial bone exposure area. In the PASTE group, collagen scaffold appeared at a later period and expression levels of epidermal growth factor and epidermal growth factor receptor increased.

CONCLUSIONS

The transformation of acellular dermal matrix into the pulverized form is thought to contribute to its non-inferior therapeutic effect compared with normal acellular dermal matrix. With respect to the mechanism, the pulverized form reduced the bone exposure area in the early stage and provided a collagen scaffold at a later period. An increase in epithelial growth factors through mechanochemical transformations along with increased contact area contribute to the enhanced healing capacity of the morphologically transformed acellular dermal matrix.

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

Chronic Diabetic Wounds and Their Treatment with Skin Substitutes

With the global prevalence of type 2 diabetes mellitus steeply rising, instances of chronic, hard-healing, or non-healing diabetic wounds and ulcers are predicted to increase. The growing understanding of healing and regenerative mechanisms has elucidated critical regulators of this process, including key cellular and humoral components. Despite this, the management and successful treatment of diabetic wounds represents a significant therapeutic challenge. To this end, the development of novel therapies and biological dressings has gained increased interest. Here we review key differences between normal and chronic non-healing diabetic wounds, and elaborate on recent advances in wound healing treatments with a particular focus on biological dressings and their effect on key wound healing pathways.

Adipose tissue-derived stem cells in breast reconstruction: a brief review on biology and translation

Recent developments in adipose-derived stromal/stem cell (ADSC) biology provide new hopes for tissue engineering and regeneration medicine. Due to their pluripotent activity, paracrine activity, and immunomodulatory function, ADSCs have been widely administrated and exhibited significant therapeutic effects in the treatment for autoimmune disorders, neurodegenerative diseases, and ischemic conditions both in animals and human clinical trials. Cell-assisted lipotransfer (CAL) based on ADSCs has emerged as a promising cell therapy technology and significantly improved the fat graft retention. Initially applied for cosmetic breast and facial enhancement, CAL has found a potential use for breast reconstruction in breast cancer patients. However, more challenges emerge related to CAL including lack of a standardized surgical procedure, the controversy in the effectiveness of CAL, and the potential oncogenic risk of ADSCs in cancer patients. In this review, we summarized the latest research and intended to give an outline involving the biological characteristics of ADSCs as well as the preclinical and clinical application of ADSCs.

Human decellularized adipose matrix derived hydrogel assists mesenchymal stem cells delivery and accelerates chronic wound healing

Biological scaffolds based stem cell delivery methods have emerged as a promising approach for tissue repair and regeneration. Here we developed a hydrogel biological scaffold from human decellularized adipose matrix (hDAM) for human adipose-derived stem cells (hASCs) delivery to accelerate chronic wound healing. The hDAM hydrogel was prepared by pepsin mediated digestion and pH controlled neutralization. The morphology, survival, proliferation, and angiogenic paracrine activity of hASCs cultured in the hydrogel were assessed. Moreover, the therapeutic efficacy of the hASCs-hydrogel composite for impaired wound healing was evaluated by using a full-thickness wound model on diabetic mouse. The developed hDAM hydrogel was a thermosensitive hydrogel, presented the biochemical complexity of native extracellular matrix and formed a porous nanofiber structure after gelation. The hydrogel can support hASCs adhesion, survival, and proliferation. Compared to standard culture condition, hASCs cultured in the hydrogel exhibited enhanced paracrine activity with increased secretion of hepatocyte growth factor. In the diabetic mice model with excisional full-thickness skin wounds, mice treated with the hASCs-hydrogel composite displayed accelerated wound closure and increased neovascularization. Our results suggested that the developed hDAM hydrogel can provide a favorable microenvironment for hASCs with augmented regeneration potential to accelerate chronic wound healing.

Stem Cell Seeded and Silver Nanoparticles Loaded Bilayer PLGA/PVA Dressings for Wound Healing

Antibacterial activity and promoting wound healing are two important characteristics of ideal dressings. The previous work has successfully prepared a stem cell seeded polyvinyl alcohol (PVA) hydrogel dressing, which could promote wound healing by active factors secreted from the dressing. However, a lack of antibacterial activity might limit its better application. In this study, a photo-active gelatin (Az-Gel) modified stem cell seeded bilayer PVA hydrogel dressings with silver nanoparticles loaded poly(lactic-co-glycolic acid) (PLGA) electrospinning films (Ag-PLGA) in it is prepared. The physical properties of the dressings show the dressings are mechanically enhanced by the addition of Ag-PLGA film. The addition of Ag-PLGA film does not alter the moisture content of PVA, but extends the moisture of the dressing. Obviously, antibacterial activity is observed and Ag-PLGA/PVA scaffold is biocompatible and low toxic to murine dermal fibroblasts (NIH-3T3). When seeded with Adipose-derived stem cells (ADSCs), bioactive factors secreted by ADSCs could penetrate the dressing and promote cell growth and wound healing. It is speculated that the stem cells seeded bilayer dressing would be of great potential for skin tissue engineering, because of its antibacterial activity and safe application of stem cells.

Adipose-Derived Mesenchymal Stem Cells in the Treatment of Diabetic Foot Ulcers: A Review of Preclinical and Clinical Studies

This review provides an outline of the use of adipose-derived mesenchymal stem cells (AMSCs) in the treatment of diabetic foot ulcers (DFUs). A systematic search of PubMed and the Cochrane database was performed on October 2, 2019. Eighteen studies were identified (14 preclinical and 4 clinical). Studies in animal models have demonstrated that AMSCs enhance diabetic wound healing, accelerate granulation tissue formation, and increase reepithelialization and neovascularization. Only 1 randomized control trial has been published so far. Patients (n = 25) with DFUs were treated using an allogeneic AMSC directly on the wound bed as a primary dressing, and improvements were found in complete wound closure in the treatment group (n = 16). Three clinical studies showed that autologous AMSC might be a safe alternative to achieve therapeutic angiogenesis in patients with diabetes and peripheral arterial disease. Based on the available evidence, AMSCs hold promise in the treatment of DFUs. However, this evidence requires confirmation by well-designed trials. Additional studies are also required to understand some issues regarding this treatment for DFUs. For example, the potential application of autologous or allogeneic AMSCs in different types of DFUs, optimal dose/infusion schedules, safety evaluations, and cost-effectiveness.

Adipose-Derived Stem Cells for Regenerative Wound Healing Applications: Understanding the Clinical and Regulatory Environment

There is growing interest in the regenerative potential of adipose-derived stem cells (ADSCs) for wound healing applications. ADSCs have been shown to promote revascularization, activate local stem cell niches, reduce oxidative stress, and modulate immune responses. Combined with the fact that they can be harvested in large numbers with minimal donor site morbidity, ADSC products represent promising regenerative cell therapies. This article provides a detailed description of the defining characteristics and therapeutic potential of ADSCs, with a focus on understanding how ADSCs promote tissue regeneration and repair. It summarizes the current regulatory environment governing the use of ADSC products across Europe and the United States and examines how various adipose-derived products conform to the current UK legislative framework. Advice is given to clinicians and researchers on how novel ADSC therapeutics may be developed in accordance with regulatory guidelines.

Chondrogenesis of Adipose-Derived Stem Cells on Irradiated Cartilage

BACKGROUND

Irradiated allogeneic costal cartilage is an alternative option of cartilage graft in patients with insufficient autologous cartilage. However, complications can occur during long-term follow-up. This study investigated whether Tutoplast-processed cartilage, one of the irradiated allogeneic costal cartilages, acts as a scaffold for adipose-derived stem cells and chondrogenesis.

METHODS

In vitro setting, human adipose-derived stem cells seeded onto Tutoplast-processed cartilage were cultured in chondrogenic medium and observed using a scanning electron microscope. Next, 3 types of irradiated cartilage-including Tutoplast-processed cartilage, undifferentiated stem cells on Tutoplast-processed cartilage (undifferentiated group), and chondrogenic differentiated stem cells on Tutoplast-processed cartilage (chondrogenic group)-were implanted subcutaneously into nude mice. Gross, histologic, and gene expression analyses of Tutoplast-processed cartilages were performed at postoperative weeks 2 and 4.

RESULTS

Human adipose-derived stem cells subjected to in vitro three-dimensional culture differentiated into chondrocytes and expressed cartilage-specificgenes. Adipose-derived stem cells seeded onto Tutoplast-processed cartilage were differentiated into chondrocytes in chondrogenic medium. In the chondrogenic group, the chondrogenic-differentiated cells attached to the surface of the Tutoplast-processed cartilage were maintained during the follow-up and were distinct from the existing Tutoplast-processed cartilage. Moreover, the chondrogenic group had higher expression of cartilage-specific genes compared with the undifferentiated group.

CONCLUSIONS

Adipose-derived stem cells seeded onto Tutoplast-processed cartilage underwent chondrogenic differentiation, generating new cartilage, which was maintained after implantation without critical complications. The findings are clinically valuable in terms of overcoming the limitations of irradiated allogeneic costal cartilage, and broaden the surgical options for treatments requiring cartilage.

The Role of Adipose-Derived Stem Cells, Dermal Regenerative Templates, and Platelet-Rich Plasma in Tissue Engineering-Based Treatments of Chronic Skin Wounds

The continuous improvements in the field of both regenerative medicine and tissue engineering have allowed the design of new and more efficacious strategies for the treatment of chronic or hard-to-heal skin wounds, which represent heavy burden, from a medical and economic point of view. These novel approaches are based on the usage of three key methodologies: stem cells, growth factors, and biomimetic scaffolds. These days, the adipose tissue can be considered the main source of multipotent mesenchymal stem cells, especially adipose-derived stem cells (ASCs). ASCs are easily accessible from various fat depots and show an intrinsic plasticity in giving rise to cell types involved in wound healing and angiogenesis. ASCs can be found in fat grafts, historically used in the treatment of chronic wounds, and have been evaluated as such in both animal models and human trials, to exploit their capability of accelerating wound closure and inducing a correct remodeling of the newly formed fibrovascular tissue. Since survival and fitness of ASCs need to be improved, they are now employed in conjunction with advanced wound dressings, together with dermal regenerative templates and platelet-rich plasma (as a source of growth and healing factors). In this work, we provide an overview of the current knowledge on the topic, based on existing studies and on our own experience.

Human decellularized dermal matrix seeded with adipose-derived stem cells enhances wound healing in a murine model: Experimental study

OBJECTIVE

Full-thickness cutaneous wounds treated with split-thickness skin grafts often result in unaesthetic and hypertrophic scars. Dermal substitutes are currently used together with skin grafts in a single treatment to reconstruct the dermal layer of the skin, resulting in improved quality of scars. Adipose-derived stem cells (ASCs) have been described to enhance wound healing through structural and humoral mechanisms. In this study, we investigate the compatibility of xenogen-free isolated human ASCs seeded on human acellular dermal matrix (Glyaderm®) in a murine immunodeficient wound model.

METHODS

Adipose tissue was obtained from abdominal liposuction, and stromal cells were isolated mechanically and cultured xenogen-free in autologous plasma-supplemented medium. Glyaderm® discs were seeded with EGFP-transduced ASCs, and implanted on 8 mm full-thickness dorsal wounds in an immunodeficient murine model, in comparison to standard Glyaderm® discs. Re-epithelialization rate, granulation thickness and vascularity were assessed by histology on days 3, 7 and 12. Statistical analysis was conducted using the Wilcoxon signed-rank test. EGFP-staining allowed for tracking of the ASCs in vivo. Hypoxic culture of the ASCs was performed to evaluate cytokine production.

RESULTS

ASCs were characterized with flowcytometric analysis and differentiation assay. EGFP-tranduction resulted in 95% positive cells after sorting. Re-epithelialization in the ASC-seeded Glyaderm® side was significantly increased, resulting in complete wound healing in 12 days. Granulation thickness and vascularization were significantly increased during early wound healing. EGFP-ASCs could be retrieved by immunohistochemistry in the granulation tissue in early wound healing, and lining vascular structures in later stages.

CONCLUSION

Glyaderm® is an effective carrier to deliver ASCs in full-thickness wounds. ASC-seeded Glyaderm® significantly enhances wound healing compared to standard Glyaderm®. The results of this study encourage clinical trials for treatment of full-thickness skin defects. Furthermore, xenogen-free isolation and autologous plasma-augmented culture expansion of ASCs, combined with the existing clinical experience with Glyaderm®, aid in simplifying the necessary procedures in a GMP-laboratory setting.

Adipose-derived stem cells prevent the onset of bisphosphonate-related osteonecrosis of the jaw through transforming growth factor β-1-mediated gingival wound healing

Background

Due to its complex pathogenesis and low clinical cure rate, bisphosphonate-related osteonecrosis of the jaw (BRONJ) poses a substantial challenge for oral and maxillofacial surgeons. Therefore, the treatment of BRONJ should focus on prevention. In clinical studies, primary wound closure can significantly reduce the incidence of BRONJ. Whether local stem cell transplantation can promote primary gingival healing in patients with a medication history and prevent BRONJ has not been reported.

Methods

In this study, animals were divided into a healthy group (non-drug treatment), a BP group, a hydroxyapatite (HA) group, and an adipose-derived stem cell (ADSC) group. All groups except the healthy group were treated with BPs and immunosuppressive drugs once per week for 8 weeks, simulating clinical use for the treatment of cancer patients with bone metastasis, to induce BRONJ-like animals. After the sixth drug treatment, the bilateral premolars were extracted in all groups. In contrast to the healthy and BP groups, the extraction sockets in the HA and ADSC groups were filled with HA or HA + ADSCs simultaneously post extraction to observe the preventive effect of ADSCs on the occurrence of BRONJ. At 2 and 8 weeks post extraction, animals from all groups were sacrificed.

Results

At 8 weeks post transplantation, ADSCs prevented the occurrence of BRONJ, mainly through accelerating healing of the gingival epithelium at 2 weeks post extraction. We also found that ADSCs could upregulate the expression of transforming growth factor β1 (TGF-β1) and fibronectin in tissue from animals with a medication history by accelerating gingival healing of the extraction socket. A rescue assay further demonstrated that TGF-β1 and fibronectin expression decreased in TGF-β1-deficient ADSC-treated animals, which partially abolished the preventive effect of ADSCs on the onset of BRONJ.

Conclusion

ADSCs prevent the onset of BRONJ, mainly by upregulating the expression of TGF-β1 and fibronectin to promote primary gingival healing, ultimately leading to bone regeneration in the tooth extraction socket. Our new findings provide a novel stem cell treatment for the prevention of BRONJ.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1277-y) contains supplementary material, which is available to authorized users.

Patterned Polyvinyl Alcohol Hydrogel Dressings with Stem Cells Seeded for Wound Healing

Polyvinyl alcohol (PVA) hydrogel and stem cell therapy have been widely used in wound healing. However, the lack of bioactivity for PVA and security of stem therapy limited their application. In this study, an adipose-derived stem cells (ADSCs)-seeded PVA dressing (ADSCs/PVA) was prepared for wound healing. One side of the PVA dressing was modified with photo-reactive gelatin (Az-Gel) via ultraviolet (UV) irradiation (Az-Gel@PVA), and thus ADSCs could adhere, proliferate on the PVA dressings and keep the other side of the dressings without adhering to the wound. The structure and mechanics of Az-Gel@PVA were determined by scanning electron microscopy (SEM) and material testing instruments. Then, the adhesion and proliferation of ADSCs were observed via cell counts and live-dead staining. Finally, in vitro and in vivo experiments were utilized to confirm the effect of ADSCs/PVA dressing for wound healing. The results showed that Az-Gel was immobilized on the PVA and showed little effect on the mechanical properties of PVA hydrogels. The surface-modified PVA could facilitate ADSCs adhesion and proliferation. Protein released tests indicated that the bioactive factors secreted from ADSCs could penetrated to the wound. Finally, in vitro and in vivo experiments both suggested the ADSCs/PVA could promote the wound healing via secreting bioactive factors from ADSCs. It was speculated that the ADSCs/PVA dressing could not only promote the wound healing, but also provide a new way for the safe application of stem cells, which would be of great potential for skin tissue engineering.

Mapping theme trends and knowledge structure on adipose-derived stem cells: a bibliometric analysis from 2003 to 2017

AIM

To investigate the theme trends and knowledge structure of adipose-derived stem cells (ADSCs) related literatures by using bibliometric analysis.

MATERIALS & METHODS

Co-word analysis, strategic diagram and social network analysis were employed.

RESULTS

In line with strategic diagrams, ADSC differentiation and transplantation as main undeveloped themes in 2003-2007 were partially replaced by regeneration medicine and ADSCs for myocardial infarction in 2008 to 2012, and then partially replaced by miRNAs in ADSC genetics and nerve regeneration in 2013 to 2017. Based on social network analysis, regenerative medicine/methods, myocardial infarction/therapy, as well as miRNAs/genetics, and nerve regeneration/physiology were considered the emerging hot spots in 2008 to 2012 and 2013 to 2017.

CONCLUSION

The undeveloped themes and emerging hot spots could be considered as new research topics.

Autologous fat grafting: Latest insights

A recent rise in the use of autologous fat transfer for soft tissue augmentation has paralleled the increasing popularity of liposuction body contouring. This creates a readily available and inexpensive product for lipografting, which is the application of lipoaspirated material. Consistent scientific proof about the long-term viability of the transferred fat is not available. Clinically, there is a reabsorption rate which has been reported to range from 20 to 90%. Results can be unpredictable with overcorrection and regular need for additional interventions. In this review, adipogenesis physiology and the adipogenic cascade from adipose-derived stem cells to adult adipocytes is extensively described to determine various procedures involved in the fat grafting technique. Variables in structure and physiology, adipose tissue harvesting- and processing techniques, and the preservation of fat grafts are taken into account to collect reproducible scientific data to establish standard in vitro and in vivo models for experimental fat grafting. Adequate histological staining for fat tissue, immunohistochemistry and viability assays should be universally used in experiments to be able to produce comparative results. By analysis of the applied methods and comparison to similar experiments, a conclusion concerning the ideal technique to improve clinical outcome is proposed.

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Adipogenic physiology is described to determine various procedures involved in the fat grafting technique.

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Clinical studies on fat grafting have confirmed an unpredictable result.

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After analysis of the literature and despite attempts to eliminate confounding factors, on every step of the fat transfer technique a number of studies with conflicting results exist.

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Adequate histological staining for fat tissue, immunohistochemistry and viability assays should be universally used in experiments to be able to produce comparative results.

Decellularized Matrices As Cell-Instructive Scaffolds to Guide Tissue-Specific Regeneration

Decellularized scaffolds are promising clinically translational biomaterials that can be applied to direct cell responses and promote tissue regeneration. Bioscaffolds derived from the extracellular matrix (ECM) of decellularized tissues can naturally mimic the complex extracellular microenvironment through the retention of compositional, biomechanical, and structural properties specific to the native ECM. Increasingly, studies have investigated the use of ECM-derived scaffolds as instructive substrates to recapitulate properties of the stem cell niche and guide cell proliferation, paracrine factor production, and differentiation in a tissue-specific manner. Here, we review the application of decellularized tissue scaffolds as instructive matrices for stem or progenitor cells, with a focus on the mechanisms through which ECM-derived scaffolds can mediate cell behavior to promote tissue-specific regeneration. We conclude that although additional preclinical studies are required, ECM-derived scaffolds are a promising platform to guide cell behavior and may have widespread clinical applications in the field of regenerative medicine.

Combination therapy of autologous adipose mesenchymal stem cell-enriched, high-density lipoaspirate and topical timolol for healing chronic wounds

Chronic venous leg ulcers are profoundly debilitating and result in billions in health care expenditure. Thus, there is a quest for engineered and innovative approaches. Herein we present a 63-year-old patient with a 30 year history of venous stasis and left lower extremity ulcers, which have been refractory to standard of care, anticoagulation and venous stripping. The medial ulcer was treated with transplantation of autologous adipose mesenchymal stem cell (AMSC)-enriched, high-density lipoaspirate (HDL) on OASIS wound matrix and compression therapy. The lateral ulcer was treated as a control with standard debridement and compression therapy. Four weeks later, both ulcers received daily topical timolol. Three months later, the test ulcer was completely epithelized and remains healed for over 15 months. However, the control showed minimal signs of improvement. In companion studies in our laboratory, human AMSC were cultured in Minimum Essential Medium Eagle Alpha Modifications (MEMα) with fetal bovine serum (FBS). Timolol was administered to AMSC prior to treatment with epinephrine and 104 bacteria/ml heat-killed Staphylococcus aureus. The MEMα with FBS devoid of AMSC served as a background control. After 24 h, cell culture supernatants and protein lysates were collected to determine cytokine production. There was a statistical significant decrease in pro-inflammatory interleukin-6 and -8 induced by the bacteria (to model the wound environment) in AMSC in the presence of timolol compared with control (p < 0.5). This is the first case of a successful combination of autologous AMSC-enriched, HDL with topical timolol for the healing of chronic venous leg ulcers. Copyright © 2016 John Wiley & Sons, Ltd.

Transit-Amplifying Cells in the Fast Lane from Stem Cells towards Differentiation

Stem cells have a high potential to impact regenerative medicine. However, stem cells in adult tissues often proliferate at very slow rates. During development, stem cells may change first to a pluripotent and highly proliferative state, known as transit-amplifying cells. Recent advances in the identification and isolation of these undifferentiated and fast-dividing cells could bring new alternatives for cell-based transplants. The skin epidermis has been the target of necessary research about transit-amplifying cells; this work has mainly been performed in mammalian cells, but further work is being pursued in other vertebrate models, such as zebrafish. In this review, we present some insights about the molecular repertoire regulating the transition from stem cells to transit-amplifying cells or playing a role in the transitioning to fully differentiated cells, including gene expression profiles, cell cycle regulation, and cellular asymmetrical events. We also discuss the potential use of this knowledge in effective progenitor cell-based transplants in the treatment of skin injuries and chronic disease.

The biological and clinical basis for the use of adipose-derived stem cells in the field of wound healing

Worldwide, hard-to-heal lower limb wounds are estimated to affect 1.5–3% of the adult population with a treatment-related annual cost of $10 billion. Thus, chronic skin ulcers of the lower limb are a matter of economic and public concern. Over the years, multiple medical and surgical approaches have been proposed but they are still inadequate, and no effective therapy yet exists. Regenerative medicine and stem cell-based therapies hold great promise for wound healing. Recently, many plastic surgeons have studied the potential clinical application of adipose-derived stem cells (ASCs), which are a readily available adult stem cell population that can undergo multilineage differentiation and secrete growth factors that can enhance wound-healing processes by promoting angiogenesis, and hence increase local blood supply. ASCs have been widely studied in vitro and in vivo in animal models. However, there are few randomized clinical trials on humans, and these are still ongoing or recruiting patients. Moreover, there is no consensus on a common isolation protocol that is clinically feasible and which would ensure reproducible results. The authors aim to provide readers with an overview of the biological properties of ASCs as well as their clinical application, to help better understanding of present and future strategies for the treatment of hard-to-heal wounds by means of stem cell-based therapies.

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Worldwide, hard-to-heal wounds are a matter of economic and public concern.

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The emerging fields of regenerative medicine and stem cell-based therapies hold great promise for wound healing.

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ASCs can potentially give the support necessary for recovery of hard-to-heal wounds.

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ASCs can be easily harvested from adipose tissue by means of standard wet liposuction technique.

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ASCs have been widely studied in vitro and in vivo to demonstrate their potential and safety.

Therapeutic angiogenesis of adipose-derived stem cells for ischemic diseases

Ischemic diseases, the leading cause of disability and death, are caused by the stenosis or obstruction of arterioles/capillaries that is not compensated for by vessel dilatation or collateral circulation. Angiogenesis is a complex process leading to new blood vessel formation and is triggered by ischemic conditions. Adequate angiogenesis, as a compensatory mechanism in response to ischemia, may increase oxygen and nutrient supplies to tissues and protect their function. Therapeutic angiogenesis has been the most promising therapy for treating ischemic diseases. In recent years, stem cell transplantation has been recognized as a new technique with therapeutic angiogenic effects on ischemic diseases. Adipose-derived stem cells, characterized by their ease of acquisition, high yields, proliferative growth, and low immunogenicity, are an ideal cell source. In this review, the characterization of adipose-derived stem cells and the role of angiogenesis in ischemic attack are summarized. The angiogenic effects of adipose-derived stem cells are discussed from the perspectives of in-vitro, in-vivo, and clinical trial studies for the treatment of ischemic diseases, including ischemic cardiac, cerebral, and peripheral vascular diseases and wound healing. The microvesicles/exosomes released from adipose-derived stem cells are also presented as a novel therapeutic prospect for treating ischemic diseases.

Current Advancements and Strategies in Tissue Engineering for Wound Healing: A Comprehensive Review

Significance: With an aging population leading to an increase in diabetes and associated cutaneous wounds, there is a pressing clinical need to improve wound-healing therapies. Recent Advances: Tissue engineering approaches for wound healing and skin regeneration have been developed over the past few decades. A review of current literature has identified common themes and strategies that are proving successful within the field: The delivery of cells, mainly mesenchymal stem cells, within scaffolds of the native matrix is one such strategy. We overview these approaches and give insights into mechanisms that aid wound healing in different clinical scenarios. Critical Issues: We discuss the importance of the biomimetic niche, and how recapitulating elements of the native microenvironment of cells can help direct cell behavior and fate. Future Directions: It is crucial that during the continued development of tissue engineering in wound repair, there is close collaboration between tissue engineers and clinicians to maintain the translational efficacy of this approach.

Effect of adipose-derived stem cells on acellular dermal matrix engraftment in a rabbit model of breast reconstruction

Acellular dermal matrix (ADM) is frequently used in implant-based breast reconstruction. Although there are several advantages, ADM implantation also increases the risk of certain complications. Recently, ADM seeded with adipose-derived stem cells (ADSCs) were shown to induce angiogenesis and improve wound healing. This study aimed to investigate the effects of ADSCs on ADM engraftment in a rabbit model of implant-based breast reconstruction. Silicone implants were inserted to submuscular pocket of 16 female New Zealand rabbits using ADM with or without seeding of fluorescent PKH26-labelled rabbit ADSCs. The marginal and central ADMs in each group were evaluated at 1 and 3 months after insertion. We performed a histological analysis including the number of CD31⁺ blood vessels, vimentin⁺ fibroblasts and lymphocytes; live/dead analysis; and gene expression analysis related to angiogenesis, inflammation and hypoxia. The implant was exposed in one rabbit with ADM without ADSCs during the study period. At 1 month, a histological analysis revealed more blood vessels and fibroblasts and reduced immune cell infiltration in marginal ADM with ADSCs. At 3 months, only angiogenesis was histologically different between groups. Conversely, cellularity was not significantly different in the central ADM between groups at month 1 or 3. ADSC supplementation increased the gene expression level associated with angiogenesis and inflammation, but not hypoxia. PKH26-labelled ADSCs were observed in both marginal and central ADMs at month 3. ADM seeded with ADSCs might be useful in promoting early incorporation with recipient tissue. This study supports the potential of ADM seeded with ADSCs as a reliable material for implant-based breast reconstruction.

Xenogeneic transplantation of human adipose-derived stem cell sheets accelerate angiogenesis and the healing of skin wounds in a Zucker Diabetic Fatty rat model of obese diabetes

Introduction

Diabetic patients with foot ulcers often suffer impaired wound healing due to diabetic neuropathy and blood flow disturbances. Direct injection of human adipose-derived stem cells (hASCs) effectively accelerates wound healing, although hASCs are relatively unstable.

Methods

We developed an optimized protocol to engineer hASC sheets using temperature-responsive culture dishes to enhance the function and stability of transplanted cells used for regenerative medicine. Here, we evaluated the efficacy of hASC sheets for enhancing wound healing. For this purpose, we used a xenogeneic model of obese type 2 diabetes, the Zucker Diabetic Fatty rat (ZDF rat), which displays full-thickness skin defects. We isolated hASCs from five donors, created hASC sheets, and transplanted the hASC sheets along with artificial skin into full-thickness, large skin defects (15-mm diameter) of ZDF rats.

Results

The hASC sheets secreted angiogenic growth factors. Transplantation of the hASC sheets combined with artificial skin increased blood vessel density and dermal thickness, thus accelerating wound healing compared with that in the controls. Immunohistochemical analysis revealed significantly more frequent neovascularization in xenografted rats of the transplantation group, and the transplanted hASCs were localized to the periphery of new blood vessels.

Conclusion

This xenograft model may contribute to the use of human cell tissue-based products (hCTPs) and the identification of factors produced by hCTPs that accelerate wound healing.

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We established a protocol for human adipose-derived stem cells (hASC) sheets.

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The hASC sheets secreted angiogenic growth factors.

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Xenogeneic hASC sheet transplantation accelerated wound healing in diabetic rats.

Trauma and Stem Cells: Biology and Potential Therapeutic Implications

Trauma may cause irreversible tissue damage and loss of function despite current best practice. Healing is dependent both on the nature of the injury and the intrinsic biological capacity of those tissues for healing. Preclinical research has highlighted stem cell therapy as a potential avenue for improving outcomes for injuries with poor healing capacity. Additionally, trauma activates the immune system and alters stem cell behaviour. This paper reviews the current literature on stem cells and its relevance to trauma care. Emphasis is placed on understanding how stem cells respond to trauma and pertinent mechanisms that can be utilised to promote tissue healing. Research involving notable difficulties in trauma care such as fracture non-union, cartilage damage and trauma induced inflammation is discussed further.

Cell-mediated remodeling of biomimetic encapsulating hydrogels triggered by adipogenic differentiation of adipose stem cells

One of the most common regenerative therapies is autologous fat grafting, which frequently suffers from unexpected volume loss. One approach is to deliver adipose stem cells encapsulated in the engineered hydrogels supportive of cell survival, differentiation, and integration after transplant. We describe an encapsulating, biomimetic poly(ethylene)-glycol hydrogel, with embedded peptides for attachment and biodegradation. Poly(ethylene)-glycol hydrogels containing an Arg–Gly–Asp attachment sequence and a matrix metalloprotease 3/10 cleavage site supported adipose stem cell survival and showed remodeling initiated by adipogenic differentiation. Arg–Gly–Asp–matrix metalloprotease 3/10 cleavage site hydrogels showed an increased number and area of lacunae or holes after adipose stem cell differentiation. Image analysis of adipose stem cells in Arg–Gly–Asp–matrix metalloprotease 3/10 cleavage site hydrogels showed larger Voronoi domains, while cell density remained unchanged. The differentiated adipocytes residing within these newly remodeled spaces express proteins and messenger RNAs indicative of adipocytic differentiation. These engineered scaffolds may provide niches for stem cell differentiation and could prove useful in soft tissue regeneration.

Current and emerging vascularization strategies in skin tissue engineering

Vascularization is a key process in skin tissue engineering, determining the biological function of artificial skin implants. Hence, efficient vascularization strategies are a major prerequisite for the safe application of these implants in clinical practice. Current approaches include (i) modification of structural and physicochemical properties of dermal scaffolds, (ii) biological scaffold activation with growth factor-releasing systems or gene vectors, and (iii) generation of prevascularized skin substitutes by seeding scaffolds with vessel-forming cells. These conventional approaches may be further supplemented by emerging strategies, such as transplantation of adipose tissue-derived microvascular fragments, 3D bioprinting and microfluidics, miRNA modulation, cell sheet engineering, and fabrication of photosynthetic scaffolds. The successful translation of these vascularization strategies from bench to bedside may pave the way for a broad clinical implementation of skin tissue engineering.

Secretory factors of human chorion-derived stem cells enhance activation of human fibroblasts

BACKGROUND AIMS

Wound healing remains a principal challenge in modern medical science. Chorion-dervied stem cells (CDSCs), isolated from human placenta, have largely been overlooked, and few studies on their potential in wound healing have been conducted. In this study, we investigated the functional characteristics of CDSCs compared with adipose-derived stem cells (ASCs) on human fibroblasts (HFs).

METHODS

We analyzed CDSCs by means of flow cytometry to confirm their mesenchymal stromal cell characteristics. We then evaluated the paracrine effects of CDSCs on HFs in a co-culture system and focused on fibroblast proliferation, migration and collagen synthesis. To explore the potential of CDSCs in wound healing, CDSC- and ASC-secreted factors were compared by use of a cytokine antibody array.

RESULTS

CDSCs had morphology similar to MSCs and expressed a mesenchymal stromal cell phenotype. HF proliferation and migration increased more than 5-fold when co-cultured with CDSCs. Furthermore, Western blot and reverse transcription-polymerase chain reaction analysis showed that expression of collagen (types I and III) in fibroblasts was upregulated 2-fold when co-cultured with CDSCs. Cytokine array results of CDSC-conditioned medium and ASC-conditioned medium revealed the presence of growth factors known to influence wound healing, including interleukin -6, interleukin -8, monocyte chemotactic protein 1 and regulated on activation, normal T cells expressed and secreted.

CONCLUSIONS

Our data demonstrated that CDSCs are functionally similar to ASCs, promote HF activation, and secrete growth factors that influence wound healing. Therefore, we suggest that CDSCs are potentially applicable in wound healing.

Intradermal injection of human adipose-derived stem cells accelerates skin wound healing in nude mice

Background

The use of stem cells from adipose tissue or adipose-derived stem cells (ASCs) in regenerative medicine could be an interesting alternative to bone marrow stem cells because they are easily accessible and available in large quantities. The aim of this study was to evaluate the potential effect of ASCs on the healing of 12 mm diameter-excisional wounds (around 110 mm²) in nude mice.

Methods

Thirty nude mice underwent surgery to create one 12-mm excisional wound per mouse (spontaneous healing, n = 6; Cytocare® 532, n = 12; ASCs, n = 12). The Galiano wound model was chosen to avoid shrinkage and thus slow the spontaneous healing (SH) of mouse skin, making it closer to the physiology of human skin healing. Transparent dressings were used to enable daily healing time measurements to be taken. Immunohistochemistry, histological and blood perfusion analysis were carried out on the healed skin.

Results

The in vivo results showed the effectiveness of using ASCs on reducing the time needed for complete healing to 21.2 days for SH, 17.4 days for vehicle alone (Cytocare® 532) and 14.6 days with the addition of ASCs (p < 0.001). Moreover, cutaneous perfusion of the healed wound was significantly improved in ASC-treated mice compared to SH group, as shown by laser Doppler flowmetry and the quantitation of blood vessels using immunohistochemistry of αsmooth muscle actin.

Conclusions

The tolerance and efficacy of cryopreserved ASCs to accelerate the complete closure of the wound by increasing the maturation of the skin and its blood perfusion, shows their therapeutic benefit in the wound healing context.

Freeze-dried rat bone marrow mesenchymal stem cell paracrine factors: a simplified novel material for skin wound therapy

The mesenchymal stem cell (MSC) supernatant is well known as a rich source of autologous cytokines and universally used for tissue regeneration in current clinical medicine. However, the limitation of conditioned medium used in open-wound repair compels the need to find a more sophisticated way to take advantage of the trophic factors of MSCs. We have now fabricated a three-dimensional membrane from freeze-dried bone marrow mesenchymal stem cells-conditioned medium (FBMSC-CM) using a simple freeze-dried protocol. Scanning electron microscopy images showed the microstructure of the FBMSC-CM membrane (FBMSC-CMM) resembling a mesh containing growth factors. ELISA was used to test the paracrine factors retained in the FBMSC-CMM, and the results indicated that FBMSC-CMM withheld over 80% of the paracrine factors. Live/dead assays were adopted to test the toxicity of the FBMSC-CMM on cultured rat dermal fibroblasts, and the results confirmed its biological safety with low toxicity. Moreover, the FBMSC-CMM could significantly accelerate wound healing and enhance the neovascularization as well as epithelialization through strengthening the trophic factors in the wound bed as determined by immunohistochemical staining. Thus, the ability to maintain paracrine factors and enhance the effectiveness of these growth factors in the wound as well as the simple procedure and economical materials required for production qualifies the FBMSC-CMM to be a candidate biomaterial for open-wound regeneration.